Report SFRC-87/02 

Distribution and Abundance of 

Fish Communities Among 

Selected Estuarine and Marine 

Habitats in Everglades National 

Park 

u 

Everglades National Park, South Florida Research Center, PO. Box 279, Homestead, Florida 33030 
DISTRIBUTION AND ABUNDANCE Of FISH COMMUNITIES 

AMONG SELECTED ESTUARINE AND MRINE 

HABITATS IN-EVERGLADES NATIONAL PARK 

Gordon W. Thayer , William F. Hettler , Jr . , 

Alexander J. Chester, David R. Colby, Patti 3. McElhaney 

U .S . Department of Commerce 

National Marine Fisheries Service, NOAA 

Southeast Fisheries Center 

Beauf ort Laboratory 

Beaufort, North Carolina 28516 
TABLE OF CONTENTS 

LIST OF TABLES.. .......................................................... ii 

LIST OF FIGURES ............................................................ iv 

ABSTRACT ................................................................... I 

INTRODUCTION ............................................................... 2 

I .FISH ASSOCIATED WITH SEAGRASS AND UNVEGETATED HABITATS ......a 3 

AREA AND ILETHODS ...................................................... 3 

RESULTS AND DISCUSSION ............................................... 15 

Description of Environmental Characteristics of Strata ............ 15 

Temperature and Salinity ..................................... 15 

Silt-Clay and Organic Content of Sediments ................... 24 

Sediment Depth ............................................... 33 

Standing Crop and Shoot Density of Seagasses ................. 33 

Summary of Environmental Variables ........................... 42 

Distribution of Fish Communities .................................. 46 

Relative Abundance and Biomass .............................. 46 

Distribution of Fish Among Strata ................ ............ 56 

Distribution of Fish Within and Between Strata ............... 69 

Similarily Among Strata ...................................... 75 

Distribution of Target Species Among Strata ....................... 88 

Seasonality of Environmental Parameters and Fishes at 

Joe Kemp Key and Bradley Key ................. .... .............. 93 

Feeding Habits of Target Fish ................ .... ................. 110 

Spotted Seatrout .................... ..... .................... 110 

Gray Snapper ................................................. 117 

Feeding Habits of Other Species .............................. 120 

Distribution of Macroinvertebrates ................................ 120 

I1 . FISH COWUNITIES UTILIZING RED MNGROVE PRW ROOT HABITATS ........... A29 

AREA AND METHODS ....................................................... 134 

RESULTS AND DISCUSSION ................................................ 138 

Habitat Characteristics ........................................... 138 

Relative Abundance of Fish ........................................ 141 

Species Composition and Habitat Comparisons ....................... 149 

Day-Night Comparisons ......... .................................. 156 

Conclusions ................................................... 160 

ACKNOWLEDGMENTS ............................................................ 161 

LITERATURE CITED ........................................................... 162 
LIST OF TABLES 

. 

Table Page 

1 . Measurements made at each site ....................................... 12 

2a . Stations sampled in Stratum I ....................................... 18 

2b . Stations sampled in Stratum I1 ...................................... 19 

2c . Stations sampled in Stratum I11 ..................................... 20 

2d . Stations sampled in Stratum IV ...................................... 21 

2e . Stations sample dni Stratum V (Whitewater Bay) ....................... 22 

2f . Stations sampled in Stratum V (Coot Bay) ............................. 23 

3 . Mean values for environmental and biological parameters .......... .... 25 

4 . Average monthly temperature and salinity data by strhtum ............. 26 

5 . Fish collected by bottom trawls and their abundance by s'tratum ....... 47 

6 . Fish collected by surface trawls and their abundande by stratum ...... 53 

7 . Biomass of fish collected by bottom trawl ...... i ..................... 57 

8 . Biomass of fish collected by surface trawl ........................... 66 

9 . Abundance of fish collected in Whitewater Bay and Coot Bay 

using a bottom trawl ................................................. 70 

10 . Abundance of fish collected in Whitewater Bay and Coot Bay 

using a surface trawl ................................................ 71 

11 . Stations grouped by clusters based on dissimilarity index analyses ... 83 

12 . Abundance and occurrance of fish grouped by strata clusters .......... 84 

13 . Mean values and significance levels for variables used to 

destinguish spotted seatrout stations ................................ 92 

14 . Mean values and significance levels for variables used to 

distinguish gray snapper stations .................................... 94 

15 . Mean values and significance levels for variables used to 

distinguish combined seatrout and gray snapper stations .............. 95 

16 . Mean monthly standing .stock and biomass of seagrasses at Joe 

Kemp Key and Bradley Key ............................................. 99 

17 . Abundance and biomass of fishes collected at Joei Kemp Key and 

Bradley Key... ........................................................ 100 
List of Tables (Contd) 

. 

Table Pase 

18 . Biomass of dominant fish collected at Joe Kemp Key .................. 104 

19 . Biomass of dominant fish collected at Bradley Key .................... 105 

20 . Frequency of occurrence of-fish at Joe Kmp Key ...................... 106 

21 . Frequency of occurrence of fish at Bradley Key ....................... 111 

22 . Numbers and size range of Panulirus ar~us collected .................. 124 

23 . Numbers and biomass of Callinectes anatus collected .................. 126 

24 . Numbers and biomass of Callinectes sapidus collected ................. 127 

25 . Numbers and biomass of Penaeus duorarum collected .................... 130 

26 . Total numbers and biomass of Penaeus duorarum collected each month ... 132 

27 . Characteristics of mangrove habitats sampled for fishery 

communities .......................................................... 139 

28 . Characteristics of seagrass areas adjacent to mangrove sampling 

areas ................................................................ 140 

29 . List of fishes and abundances collected in mangrove prop root and 

adjacent seagrass meadows ............................................ 142 

30a . Analysis of variance of fish abundances collected in mangrove 

and adjacent seagrass habitat^...........^........................... 147 

30b . Analysis of variance of fish biomass collected in mangrove and 

adjacent seagrass habitats ........................................... 147 

31a . Density of fish (number/m2) collected from mangrove and 

adjacent seagrass habitats ........................................... 150 

31b . Wet weight of fish (g/m2) collected from mangrove and adjacent 

seagrass habitats .................................................... 151 

32 . Density of fishes collected in day-night sampling in mangroves 

during September 1985 ............................................... 157 
LIST OF FIGURES 

1 . Diagram of sampling area in Whitewater Bay. Coot Bay and 

Florida Bay ................... .................................... 4 

2 . Sampling area and stations in southeast Whitewater Bay ............. 5 

3 . Sampling area and stations in Coot Bay .............................. 6 

4 . Location of strata used in sampling ................................. 8 

5 . Location of channel stations in Florida Bay ........................ 9 

6 . Location of potential open water stations in Florida Bay ........... 10 

7 . Non-sampleable grid cells in Florida Bay .......................... 11 

8 . Sampling stations at Joe Kemp Key and Bradley Key .................. 14 

9 . Diagram showing number of times each grid cell was sampled 

in Florida Bay ..................................................... 16 

10 . Stations sampled in Coot Bay and mitewater Bay .................... 17 

11 . Distribution of percent silt-clay in Florida Bay ................... 28 

12 . Distribution of percent silt-clay in Whitewater Bay and 

Coot Bay ........................................................... 29 

13 . Mean monthly sediment organic content for each stratum ............. 30 

14 . Distribution of percent organic matter. .in Florida Bay 

sediments .......................................................... 31 

15 . Distribution of percent organic matter in sediments from 

Whitewater Bay and Coot Bay ......................................... 32 

16 . Distribution of sediment thickness in Florida Bay .................. 34 

17 . Distribution of sediment thickness in Whitewater Bay and 

Coot Bay ........................................................... 35 

18 . Seagrass standing crops in Florida Bay ............................. 37 

19 . Seagrass standing crops in channels sampled in Florida Bay ......... 38 

20 . Seagrass shoot density distribution in Florida Bay ................. 40 

21 . Seagrass shoot density in channels sampled in Florida Bay .......... 41 
List of Figures (Contd) 

Figure Page 

22 . Standing crop of seagrasses at Whitewater Bay and Coot 

Bay stations ......................................................... 43 

23 . Seagrass shoot densities at Whitewater Bay and Coot Bay stations .... .4.4 

24 . Distribution of bottom types in Coot Bay (March 1984) ............... 45 

25 . Venn diagrams of surface-trawl data for fishes from the 

five strata ......................................................... 62 

26 . Venn diagrams of otter trawl data for fishes from the five 

strata .............................................................. 63 

27 . Venn diagrams of pooled trawl data for fishes from the five 

strata .............................................................. 65 

.2 8. Distribution of fish abundances in Florida Bay ...................... 72 

29 . Distribution of fish abundances collected from channels in 

Florida Bay ......................................................... 73 

30 . Distribution of fish abundances in Whitewater Bay and Coot Bay ...... 74 

31 . Distribution of numbers of fish species collected in Florida 

Bay ................................................................. 76 

32 . Distribution of numbers of fish species collected in channels 

ifi Florida Bay ...................................................... 77 

33 . Distribution of numbers of fish species collected in 

Whitewater Bay and Coot Bay ......................................... 78 

34 . Distribution of fish biomass in Florida Bay ......................... 79 

35 . Distribution of fish biomass in channels in Flbrida Bay ............. 80 

'36 . Biomass of fish collected from Whitewater Bay and Coot Bay .......... 81 

37 . Distribution of Cluster 1 stations ...................... .... ........ 85 

38a . Distribution of Cluster 2 stations in Florida Bay .................. .. 86 

38b . Distribution of Cluster 2 stations in Whitewater Bay and 

Cwt Bay ............................................................ 87 

39 . Distribution of gray snapper and spotted seatrout c~llectiws 

in Florida Bay ............................................ .......... 90 
List of Figures (Contd) 

Figure 

40 . Seatrout habitat based on discriminant analyses ..................... 96 

41 . Gray snapper habitat based on discriminant analyses ................. 97 

42 . Distribution of non-seat rout-snapper habitat and preferred 

seatrout-snapper habitat in Florida Bay ................. .... ........ 101 

43 . Temperature and salinity distribution at Joe Kemp Key and 

Bradley Key ........... ............................................ 102 

44 . Monthly distribution of fish abundance and biomass at Joe Kemp 

Key and Bradley Key ................ ... ............................. 107 

45 . Pinfish. pigfish. silver perch and silver jenny biomass at 

Joe Kemp Key and Bradley Key ........................................ 108 

46 . Biomass of gray snapper. sheepshead. inshore lizardfish and 

spotted seatrout at Joe Kemp Key and Bradley Key .................... 109 

47 . Food items found in stomachs of sedrout ........................... 112 

48 . Food items found in stomachs of seatrout collected from 

seagrass areas ...................................................... 113 

49 . Food items found in stomachs of seatrout collected from among 

mangrove prop roots ............................................... 114 

50 . Food items in seatrout collected from Whitewater Bay and Coot 

Bay ................................................................ 115 

51 . Food items in seatrout collected from channels in Florida Bay ....... 116 

52 . Food items' in gray trout stomachs ................................. 118 

53 . Food items from gray trout collected from Florida Bay seagrass 

meadows ............................................................. 119 

54 . Food items from gray trout collected from among mangrove prop 

roots .............................................................. 121 

55 . Food items from gray trout collected in channels in Florida Bay ..... 122 

56 . Distribution of spiny lobster in Florida Bay ..................... ... 125 

57 . Distribution of ornate crabs and blue crabs in Florida Bay .......... 128 

58 . Distribution of blue crabs and penaeid shrimp in eastern 

Whitewater Bay and Coot Bay ......................................... 133 

59 . Mangrove sampling sites ............................................. 135 
List of Figures (Contd) 

Figure Page 

60. Abundance and biomass of fishes collected from mangrove and 

adjacent seagrass sampling sites.................................... 148 

61. Cluster analysis of mangrove and adjacent seagrass sites based 

on fish occurrence.. ..........*........... .. ........................ 153 

62. Cluster analysis of mangrove and seagrass sites based on 

fish occurrence ..................................................... 155 
ABSTRACT 

The overall objective of our juvenile study was to evaluate relative species abundance and size composition of fish communities among selected habitats in 

estuarine and marine waters of Everglades National Park and to provide 

descriptions of the habitats in which these fishes occurred. Particular 

emphasis was placed on spotted seat rout (Cynoscion nebulosus ) and gray snapper 

(~ut janus griseus) . The study was divided into two subob jectives --juvenile fish associated with open water habitats and fish utilizing red mangrove prop 

ro itats. 

T~C >LUU~ area was subdivided into five sampling strata that included Whitewater 

~ay-Coot Bay, channels in Florida Bay, and three open water. areas between 

western and eastern Florida Bay. Random sampling was conducted within these 

strata as well as regular periodic sampling at several selected sites. Coot Bay and eastern Whitewater Bay are characterized by low salinities and sediments 

with high Organic content and generally low densities of Ruppia maritima and/or 

~alodule wrightii. Channel areas in Florida Bay generally display the highest overall standlng crop and density of seagrasses composed of Thalassia 

testudinum, Syringodium filiforme and Halodule wrightii. The western strata of 

Florida Bay ad-lacent to the Gulf of Mexico was the most diverse in terms of 

seagrass cornposit ion, particularly in the northern port ion, and exhibits the 

highest overall densities of Syrinqodium. The central and eastern strata are 

dominated by monotypic stands of Thalassia with the sparcest seagrass densities 

occuring in the eastern area adjacent to the Florida Keys. Here the sediment 

veneer is the thinnest observed in our study area. 

Over 90 species of fish representing 43 families were collected during the 

study, and 11 species contributed to over 90% of the fish collected. Western 

Florida Bay and channels in Florida Bay consistently supported fish communities 

that were comprised of similar species and the highest densities relative to 

other study areas. On an areal basis, the average numerical abundance and 

standing crop values of fish we observed are similar to, but at the low end of, 

the range of several published reports of fishes in seagrass meadows. Cluster 

analysis demonstrated two obvious associations~ One cluster was characterized 

by species that occurred frequently and in large numbers, and this grouping occurred ~rimarilv in channels and in northwestern Florida Bay where mixtures of 

~yringodium and ~halassia were prevalent. A second cluster &s of low fish 

density stations that are qenerally in areas of sparce monotypic meadows of 

Thalassia . 

Juvenile gray snapper and spotted seat rout were collected regularly, but in 

small numbers, during the stratified sampling- phase as well as at regular sampling at Joe Kemp Key and Bradley Key. Although gray snapper were collected 

in western Florida Bay, they were most abundant in channels in eastern Florida 

Bay. This distribution is coincident with our larval sampling which found 

larval snapper only in the vicinity of the Florida Keys. Juvenile spotted 

seatrout were collected primarily in northwestern Florida Bay, and primarily in 

areas with mixed seagrass meadows containing Syringodium. Larval seatrout also 

were collected in greatest abundance in the same area, possibly suggesting only limited geographic movement of juveniles after settlement out of the plankton. 

Discriminant function analyses of data from randomly sampled sites were employed in an attempt to identify those environmental characteristics most important in 

determining juvenile spotted seatrout and gray snapper habitat. High densities 
'of Syringodium and high percentages of organic matter in the sediments were 

particularly diagnostic of spotted seatrout habitat, while Halodule and 

Syringodium biomass were the most informative variables in describing gray 

snapper habitat, particularly when these seagrasses were present in channels. 

These discriminant functions were employed to classify Joe Kemp Key and Bradley 

Key collections as having occurred at target fish or non-target fish habitat. 

Target fish were collected on all occasions at Joe Kemp Key and Bradley Key and 

the discriminant functions developed from our stratified random sampling phase 

of the study classified the sampling locations at Joe Kemp Key and Bradley Key 

as target fish habitat on all but one occasion. 

Data also are presented on the food habits of juvenile gray snapper and spotted 

seatrout, and on the distribution of spiny lobsters, blue ana ornate crabs, and 

penaeid shrimp based on otter trawl collections at the randomly sampled sites. 

Food habit data was similar to published accounts for similar size fish. There 

appeared to be distinct distribution patterns of lobsters, crabs and shrimp. t 

The red mangrove prop roots of Whitewater Bay, Coot Bay and Florida Bay provides 

an extensive habitat that heretofore has not been evaluated quantitatively for 

fishes. A technique was developed and tested to sample these habitats 

quantitatively. Fishes collected from this habitat type were compared with 

fishes collected by trawl from the immediately adjacent seagrass habitat. The 

mangrove prop root habitat supported an overall greater density and standing 

crop of fish. Several of the species utilizing the prop root habitat are of 

commercial and recreational importance (e.g., mullet and gray snapper), while 

many are forage foods for predatory fishes. This phase of the study 

demonstrated that the red mangrove prop root habitat is utilized by a wide 

variety of fish, and that greater attention should be given to evaluating its 

contribution as a refuge and a source of food resources for fishes in Everglades 

National Park. 

INTRODUCTION 

There are relatively few publications addresssing the ecology of the estuarine 

habitats of Everglades National Park and specifically the ecology of juvenile 

and forage fishes. Published data on recreationally and commercially important 

juvenile fishery organisms in estuarine and marine waters of Everglades National 

Park do not provide a great deal of insight into their distribution and 

abundance or their preferred habitats. Recently, Odum et a1 . (1982), Schomer 

and Drew (1982) and Zieman (1982) described aspects of the ecology of south 

Florida estuarine areas and Florida Bay. They summarized general distributions 

of fishery organisms associated with mangrove-lined environments and seagrass 

meadows, but little quantitative information are available on juveniles. Tabb 

and Manning (1961, 1962) and Tabb and Dubrow (1962) provided lists of 

invertebrate and fish species in portions of the area as well as information on 

general habitats of these species. These data predate the perceived decline in 

harvest felt by sport fisherman (Davis 1982), and pertain primarily to Whitewater 

Bay, Coot Bay and western Florida Bay. Powell, et al. (1986) have described the 

ecology of the fish communities using several carbonate mud banks in Florida 

Bay, and have shown this to be a very dynamic habitat used by large numbers of 

fish of numerous species. 

The objective of the juvenile phase of the overall Beaufort Laboratory study 

(see Beaufort Laboratory, 1987) was to evaluate the relative spedes abundance 
and size composition of fish communities among selected habitats in the 

estuarine and marine waters of Everglades National Park and to provide 

descriptions of the habitats sampled. We examined a variety of habitat 

characteristics in an attempt to discriminate their roles in structuring fish 

communities utilizing these habitats. Our emphasis was on four target species: 

gray snapper, spotted seatrout, red drum, and snook. Most of the fish we 

captured were species other than the target species. We include information on 

these fishes in this report to characterize the fish communities in selected 

estuarine and marine habitats of the Park. Little information was available 

until this report and that of Powell et al. (1986) on the relative distribution 

and abundance of the pelagic, shallow-water estuarine fish of the Everglades 

National Park, such as the clupeids, engraulids, atherinids, and belonids. 

This juvenile fish phase of our study is subdivided into two subobjectives: 

juvenile fish associated with seagrass habitats; and fish communities utilizing 

red mangrove (Rhizophora mangle) prop root habitats. This latter part of our 

report is a combination of two manuscripts that currently are in press (see 

Thayer et al. 1987, In press). 

I. FISH ASSOCIATED WITH SEAGRASS AND UNVEGETATED HABITATS 

AREA AND METHODS 

The study area sampled included open water and channel areas of southwestern 

Florida Bay, Coot Bay and eastern Whitewater Bay (Fig. 1) , and included 

vegetated and unvegetated bottom. Two strategies were employed. A stratified 

random design with five strata was established for sampling the fish community 

and environmental parameters in open water and in channels. In addition, two 

permanent stations on carbonate banks adjacent to Joe Kemp Key and Bradley Key 

were sampled routinely; several other areas around Joe Kemp Key also were 

sampled but on an irregular basis. 

Our sampling universe included eastern Whitewater' Bay, Coot Bay, and Florida Bay 

west of a line drawn from Tavernier Creek to Madeira Bay. These boundaries were 

chosen based on available time and resources. Eastern Whitewater Bay, from an 

area northwest of Tarpon Creek to the embayment northwest of East River (Fig. 

2), and Coot Bay (Fig. 3) formed a low salinity stratum (Stratum v). The 

remaining four higher salinity strata were located in Florida Bay. The 

northeastern boundary of the Florida Bay sampling area was a line from Tavernier 

treek to Madeira Bay; the Park boundary formed the southeastern sampling limit; 

the shore from about East Cape Canal to Madeira Bay formed a boundary; and the 

western boundary was formed by a line from the East Cape Canal to a point on the 

gulf side of Ninemile Bank and then east to a point southwest of Peterson Keys 

(Fig. 4). 

The areas sampled were designated as either open water habitats or channels and 

did not include the extensive carbonate mud banks characteristic of much of 

Florida Bay. The open water area of southwestern Florida Bay was subdivided 

into three approximately equal sized strata (Fig. 4) based on benthic 

vegetation distribution (Zieman and Fourqurean 1985) and discussions with Mr. 

Jim Fourqurean (Univ. Va., pers. comm.). Althsugh variable plant biomasses were 

evident ( tieman and Fourqurean 1985), the overall lowest Thalasqia st anding crop 

was reported for Stratum I (east), generally intermediate standing crops for the 
\ 

\ 

\ 

'.d 

& LOWER MATECUMBE 

KEY 

Figure 1. Diagram of the general sampling area showing Whi tewater Bay, Coot Bay and Florida Bay. 
Figure 2. Diagram of the southeast section of Whitewater Bay showing 

sampling locations. Only every fifth station is noted, and 

each station represents an area approximately 400 m on a side. 
COOT BAY 

35 

5s . 

Figure 3. Diagram of Coot Bay showing location of sampling stations. Every 

fifth station is shown, and each station represents an area 

approximately 400 m on a side. 
mid-portion of the area (Stratum 11), and highest values in the western section 

(Stratum 111). In establishing these strata, it was recognized that there is 

variability'in Thalassia within each strata and from south to north. Channels 

(Stratum IV) between carbonate mud banks and between islands were selected from 

Nautical Chart-11451 and after on site inspection (Fig. 5). 

Potential sampling locations within Strata I, 11, 111, and V were determined 

using a grid system. In Whitewater Bay and in Coot Bay (Figs. 2,3) each grid 

cell represented a square area approximately 400 m on a side, whereas in Strata 

I, I1 and I11 in Florida Bay (Fig. 6) each cell represented a square area 

approximately 1800 m on a side. There were 159 and 67 potentially sampleable 

cells in Whitewater Bay and Coot Bay, respectively, and 93, 98 and 107 in Strata 

I, I1 and 111, respectively. Prior to each survey a random selection procedure 

was used to select six cells from each of the first three strata; from the fifth 

stratum, two were selected from Coot Bay and four were selected from Whitewater 

Bay. Three alternate cells also were selected for each stratum in the event 

that one or more of the six selected stations turned out, during the actual 

survey, to be unsampleable (i.e., if we were unable to reach the area due to 

shallow depths or the area was outside of sampling criteria we established, see 

below). We established a depth range of 0.5-2.3 m within which we would sample, 

and if the open water area fell outside the range, an alternate cell was used; 

this range did not pertain to channels. Prior to sampling we eliminated 8, 12 

and 23 sample grids in Strata I, 11, and 111, tespectively (Fig. 71, because 

they were either too shallow (< 0.5 m) or too deep (> 2.3 m). 

Additional samples from the open water habitat of Florida Bay were taken 

routinely at both Joe Kemp Key and Bradley Key. A single area was sampled on 

each occasion adjacent to and to the east of the Flamingo Channel on the Joe 

Kemp Key carbonate mud bank (JKK *l); several other locations on this bank (Fig. 

8) also were sampled periodically. Joe Kemp Key #1 was sampled at the request 

of Everglades National Park personnel. During our sampling we noted that the 

area off the western side of Bradley Key appeared to be "good target fish 

habitat" (i.e., had seagrass species combinations typical of where we were 

finding some target species), and we established a permanent station at that 

location. 

Biological, physical and chemical data were collected (during each sampling) 

(Table 1) from the approximate mid-point of the randomly-chosen grid cell. We 

sampled fish, shrimp, crabs, vegetation, and sediment. Surveys were carried out 

in May, June, July, September and November 1984 and January, March, May and June 

1985. 

Two types of trawls were used to sample the fish community. An otter trawl was 

deployed for benthic fishes and crustaceans and a surface trawl was deployed for 

natant fishes. Both trawl types were pulled at a speed of 2.0 + 0.2 m/s (3.5 - 

4.5 knots) between two 5-m-long boats with 25-hp outboard engings. The surface 

trawl, without doors to open the mouth of the net, was pulled by two boats each 

angled about 45' away from the intended trawl transect to fish properly. For 

the otter trawl, which uses doors to open the net, we also used two boats to (1) 

increase our pulling power and speed and (2) avoid disturbing the trawl transect' 

by the prop-wash. 

Each trawl was pulled for 2 minutes in a downwind direction (except when o confined to narrow channels). A floating marker, tethered to an anchor', was 
0 in 

u crr 

*r w 

Lu 
Figure 5. Diagram of Florida Bay depicting location of Channel stations (stratum v). 
Figure 6. Diagram of Florida Bay showin the location of,open water sampling ztations. 

Each block (station) represen a s an area appmxlmately 1800 m on a side. 
Figure 7. Diagram of Florida Bay. Darkened blocks indicate areas deemed unsamplepble due to depth. 
Table 1. Measurements made at each site. 

SEDIMENT 

Organic Content (%) 

Silt--Clay (%) 

Depth (m) 

VEGETATION 

Species Composition 

Standing Crop (grams dry weight em-2) 

Shoot Density (No. m-2) 

. WATER COLUMN 

Temperature (*C) 

Salinity (o/oo) 

Turbidity 

FISH COMMUNITY - SURFACE/BOTTOM 

Species Composition 

Total Biomass of Each Species 

Abundance of Each Species 

Size Range for Each Species (general) 

Target Species 

- Length-frequency distribution 

- Weights of individuals 

- Stomach contents 
thrown overboard at the beginning and another at the end of each tow from which 

the distance of each tow was measured with an optical range finder. The area 

covered by each trawl transect then was calculated knowing the distance and 

mouth opening of the net. The surface and bottom trawl samples were positioned 

at each station so as to not overlap and disturb the habitat for the subsequent 

trawl. During our sampling of non-channel areas in Florida Bay, Coot Bay and 

Whitewater Bay (stratified stations plus fixed stations at Joe Kem Key and 

Y Bradle Key), S the average area sampled by an otter trawl was 784 m (N = 229, SE 

= 14 m ) while the surface trawl covered an average 1148 m2 (N = 223, SE = 23 

m2). Surface samples were not taken in some areas because the otter trawl 

effectively sampled the entire water column. Res ective areas sampled in S channels were 795 m2 (N = 51, SE = 33) and 1213 m (N = 41, SE = 55). 

The otter trawl was made from tarred nylon netting, 6-mm (1/4") bar with a 3-mm 

(1/8" ) mesh tail bag. The net measured 3.4 m at the head rope and 3.8 m at the 

foot rope and was fitted with 3-mm galvanized tickler chain strung between the 

otter doors. The surface trawl was a modification of the net described by 

Massman et al. (1952). It measured 6.6 m at the head rope, 6.2 m at the foot 

rope, and was 0.7 m deep. Wing mesh was 6-mm (1/4") bar with a 3-mm (1/8") mesh 

tail bag. 

After each trawl, fish and macroinvertebrates were separated from plant material 

collected. Fish, shrimp and crabs were placed in labelled sample bags for each 

station and gear type and preserved in 10% Formalin. Occasionally, large blue 

crabs (Callinectes sa idus) were measured and returned to the water. All 

lobsters (Panulirus -7 arqus were counted, total length measured, and returned to 

the collection area. At the Beaufort Laboratory, fish and crustaceans were 

identified to species, counted, and each species wet weighed as a measure of 

biomass. A measure of the total length of the smallest, largest and 

average-sized individual of each species also was made, but the standard length 

and weight of each individual of the target species were measured. 

The stomach contents of target fish were analyzed in the laboratory. Stomach 

contents of spotted seatrout and gray snapper collected in all habitats 

(channels, red mangrove prop roots (Part 11), open water/grass beds of Florida 

Bay and of Whitewater Bay and Coot Bay) were identified to major groups of prey. 

These groups were copepods , amphipods , isopods , crustacean zoea/megalopa, 

penaeids, carideans, crabs, mysids, and fish; only crustaceans and fish were 

observed in trout and snapper stomachs. Although the number and size (maximum 

length) of each prey item was recorded, data analysis was reduced to a 

comparison of the frequency of occurrence of each major prey group in stomachs 

of fish in seven size classes. Gravimetric analysis was not appropriate because 

of a wide range of digestive decomposition and/or regurgitation caused by 

preservation time. For example, in some stomachs freshly ingested shrimp would 

appear whole and could be easily quantified, whereas in other fish stomachs, 

especially those captured later in the day, only remnants of shrimp body parts 

could be recovered. 

Surface and bottom temperature and salinity were measured (YSI model 33 S-C-T 

meter) at each station, midway along and adjacent to each trawl line. At 

salinities in excess of 37 O/oo a refractometer was employed. Water samples 

also were taken for turbidity; unfortunately, our Monitek Nephelometer never - * 

functioned successfully during the study period, and therefore turbidities are 

not reported. At each station a SCUBA diver took triplicate 100 cm2 samples 
Figure 80 Diagram of area near Flamingo, FL, in F1 orida Bay showlng location of 

Joe Kemp Key sampling stations and Bradley Key. Bradley Key was 

sampled on the west and only Joe Kemp Key Station 1 data are reported 

herei no 
(quadrat with 10-cm sides) of vegetation plus a sample of surface sediment. For 

each sample, an individual on board the vessel tossed a sample quadrat over his 

shoulder, and where the quadrat landed above-ground vegetation was totally 

removed from within the quadrat frame at the sediment water interface; this was 

repeated two more times. Each sample was rinsed of sediment, placed in a 

labelled bag, and stored on ice for analyses at the laboratory. The surface 

sediment sample also was placed on ice for later analysis. On each occasion a 

marked pole was pushed into the sediment in the vicinity of one of the seagrass 

samples, and the depth of penetration to bedrock recorded if - < 2 m. 

A different procedure was used in channels. All sampling for environmental 

characteristics in the channels took place prior to trawling; this was done as a 

iafety precaution since otter trawling made channels highly turbid. A single 

iediment and grass sample was taken at the anticipated start, mid-point and end 

~f a trawl. 

iediment samples were dried at 65T, and then analyzed for organic content and 

~ercent silt-clay. Pulverized and weighed subsamples were placed in a muffle 

 urnac ace at 500'C for 24 h and the loss of weight taken as a measure of organic 

content. The remaining sediment was weighed and wetted using saturated sodium 

hexametaphosphate solution, and wet sieved. Material retained on 4.00 mm 

(shell) and 0.063 mm (sand) sieves were redried, and the difference between the 

initial total dry weight and the sum of these two size fractions was taken as a 

measure of silt-clay content, This procedure is a modification from the . 

American Society for Testing and Materials (1963). 

The plant samples were kept chilled until seagrasses were sorted at the 

laboratory. Individual short shoots of each seagrass species were counted and 

separated from any belowground material that may have been accidently collected. 

To remove carbonate, epiphytes and sediment, the shoots were rinsed in 10% 

phosphoric acid until effervesence ceased and then rewashed in seawater. The 

plant material was dried at 80-C to a constant weight and weighed to the nearest 

0.001 g. Data were averaged for each sample site for each species: Thalassia 

testudinum, Syrinqodium filiforme, Halodule wriqhtii, and Ruppia marikima. 

RESULTS AND DISCUSSION 

r)escription of Environmental Characteristics of Strata 

luring the nine monthly sampling visits to Everglades National Park a total of 

164 stations were occupied, several on more than one occasion (Figs. 9 and 10). 

Table 2 provides information on the stations in each strata that were sampled on 

each occasion. A total of 35, 40, 41, 31 and 50 different stations were sampled 

in Stratum I, 11, 111, IV, and V, respectively, representing 41%, 46%, 49%, 79% 

ind 22% of the sampleable area in each stratum. Thus, this sampling design does 

~rovide an extensive geographic basis upon which to describe habitats and 

'ishery organisms of the study area, and Florida Bay in particular. Summary 

lata for the habitat characteristics we measured are presented for each stratum 

in Table 3. 

Temperature arid Salinity 

Water temperature was similar among strata. A typical seasonal cycle was I. 

observed with minimum values in winter and maximum values in July and September 
Figure 9. Diagram of sampling areas in Florida Bay. Number wi thin a block indicates 

the number of times that station was sampled. Blocks lacking numbers 

were not sampled. 
COOT DAV 

~UT~WO~~ CANAL 

Figure 10. Diagram of Whitewater Bay (upper) and Coot Bay (lower). Stations 

with open ci rcles were sampled once while darkened circles indicate 

stations sam~led twice. 
Table 2a. Stations that were sampled in Stratum I and mnth sampled. Refer to 

Figure 6 for station location. 

Station Mon t h/Year Station Mon t h/Year 

14-16 Jul 84, Mar 85 21-15 May 85, Jun 85 

14-17 Sep 84, Nov 84 21-16 Jun 84 

Jun 85 

I 

I 15-17 Nov 84 

16-14 Sep 84 I 

16-15 Jul 84 

May 85, Jun 85 

Sep 84, Mar 85 

22-12 Nov 84, Mar 85 

22-13 Sep 84 

22-16 Jun 84 

Jan 85 

16-18 Jul 84, Mar 85 23-15 Nov 84, Jan 85, 

16-19 . Jun 84 

Jun85 

17-12 Nov 84 

17-16 May 85 

23-17 Jun 85 

23-18 May 85 

Jan 85 

I I 18-14 Jun 84 

18-16 Jan 85, my 85 

1 1 18-18 Jul 84 

19-12 Mar 85 

20-9 Mar 85 

20-12 *P 84 

20-1,7 Nov 84 

20-14 Jun 84, May 85 

-20-15 JUn 84 

20-19 Jan 85 

I I 21-8 Jul 84, Sep 84 

21-12 Jul 84, Jan 85 
Table 2b. Stations that were sampled in Stratum I1 and month sampled. Refer 

to Figure 6 for station location. 

Station month/^ ear Station on t h/~ear 

Sep 84 

May 84, Jun 84 

Jun 84 

Jun 85 

Mar 85 

May 85 

Jun 84 

Sep 84 

May 84 

May 85 

May 85, Jun 85 

Nov 84 

Sept 84 

May 84, Jan 85 

Mar 85 

Jan 85 

Jul 84 

Mar 85 

Nov 84 

Jun 84, Mar 85 

Jan 85 

Nov 84 

Jul 84 

Jun 85 

Nov 84 

May 84, Jul 84, Mar 85 

Sept 84, Nov 84 

Jul 84 

Jul 84 

Jun 85 

May 85 

May 85 

Sep 84, Jan 85, Jun 85 

Jan 85 

Jun 84, Mar 85, Jun 85 

Nov 84 

Jul 84 

Jan 84 

Jun 84 

Sep 84 
Table 2c. Stations that were sampled in Stratum I11 and month sampled. Refer to 

Figure 6 for station location. 

Station Mont h/~ear 

- -- -- 

Stat ion Mont h/Y ear 

Jun 84 

Jun 84 

Nov 84 

Jun 84, Jul 84, 

Jan 85, Jun 85 I 

May 84, Jul 84 

May 84, Jul 84 

Sep 84, Jun 85 

Mar 85, May 85 

Sep 84, Jan 85, 

Jun 85 

May 85 

Jun 85 

Mar 85 

Nov 84 

Nov 84 

May 84 

May 85 

May 84 

Mar 85 

Jun 84, Mar 85 

Jan 85 

Sep 84, Jan 85 

Sep 84 

Jun 84, Jul 84 

&Y 84 

May 85 

Jan 85, Jun 85 

Nov 84 

Jun 85 

Jan 85 

Jul 84 

May 85 

Mar 85 

Nov 84 

Jun 84 

Nov 84 

Sep 84 

Mar 85 

16-8 May 85 

19-3 May 85 

19-4 Jul 84 
Table 2d . Stations that were sampled in Stratum IV and month sampled. Refer 

to Figure 5 for station location. 

Channel Mont h/~ear Channel Mont h/Year 

Jun 85 

May 84 

Jan 85 

Jun 84 

Mar 85 

Nov 84, Jun- 85 

Jul 84 

Jul 84 

Mar 85 

Nov 84 

Mar 85 

Jun 84 

May 85 

Jun 84, Jan 85 

May 85, Jun 85 

Jul 84, Sep 84, 

Nov 84, May 85 

Sep 84 

Jul 84 

May 84, Mar 85 

Jan 85 

May 84, Jun 85 

Jun 85 

Jun 84, Jul 84, Nov 84 

Sep 84, Jan 85, May 85 

Sep 84, Jan 85 

May 85 

Jul 84, Nov 84, Jun 85 

Mar 85 

Nov 84, Jan 85, May 85 

Sep 84, Jun 85 

Jun 84, Sep 84, Mar 85 
' Table 2e. .Stations that were sampled in Stratum V (Whitewater Bay) and month 

sampled. Refer to Figure 2 for station location. 

Station (WWB) Mon t h/Yea r Stat ion Month/~ear 

1 May 84 141 Jun 85 

8 Mar 85 142 Jan 85 

11 Jul 84 148 Mar 85 

18 3un 85 149 May 85 

23 I May 84, Jun 84 155 Nov 84 

24 Sep 84 157 Jun 85 

29 Sep 84 1 59 May 85 

34 May 84 

s 

44 Sep 84 

47 Nov 84 

54 Nov 84 

55 3ul 84, Jan 85 

56 Jun 84, Mar 85 

5 7 May 84 

61 Nov 84 

69 Jun 84 

88 May 85 

May 85 

106 Jul 84 

113 Jan 85 

Jun 84 

128 Jun 85 

Jan 85 

139 Jul 84, Sep 84 
Table 2f . Stations that were sampled in Stratum V (Coot Bay) and month sampled. 

Refer to Figure 3 for station location. 

Station (CB) Month/Year 

May 85 

Jun 85 

Yay 85 

Jun 85 

Sep 84 

Jun 84 

Jul 84 

May 84 

Mar 85 

Nov 84 

Mar 85 

sep 84 

Jan 85 

Jul 84 

May 84 

Jun 84 

NOV 84 

Jan 85 
(Table 4). Slightly greater differences in the average maximum and minimum 

water temperatures occurred in stratum I (12.5-C) and stratum I1 (14.7012) than 

elsewhere in our sampling area (10.1-11.6.C) (Table 3). This probably is a 

reflection of the shallowness and generally low water exchange that occurs in 

the eastern and central sections of Florida Bay (see Schomer and Drew 1982). 

There was a significant difference in mean salinity among strata, and also with 

season (ANOVA, p < 0.05). Coot Bay and Whitewater Bay (Stratum V) had 

significantly lower salinities (R = 17.2 o/oo; Table 3) than did the remaining 

strata (2 = 36.0 o/oo; Table 3) (p < 0.001). This difference supported our 

initial decision to separate the sampling area into two salinity zones. Coot 

Bay maintained a slightly higher salinity (18.8 o/oo) than did Whitewater Bay 

(16.9 o/oo) during our period of study. In general, all strata displayed lowest 

salinity between September and March and higher salinities during the remainder 

of the year (Table 4). 

In Florida ~ay: the largest extremes in salinity were encountered in the 

interior subenvironment (Strata I and 11). In Stratum I there was a maximum 

recorded range for stations of 21 o/oo during the year. Wide seasonal ranges in 

the interior region are common (Shorner and Drew 1982), and apparently are 

related to restricted circulation. It is possible that water control structures 

along the northern portion of Everglades National Park exacerbate the normal 

salinity extremes in this area by manipulations of deficits and excesses of 

freshwater inflow to the area. Stations, in Stratum I1 displayed less of a range 

(17.0 o/oo), from 28 o/oo in November to 45.0 o/oo in May. Within Stratum 111, 

near the Gulf of Mexico, the range was 16.0 o/oo, from 24 o/oo in September to 

40.0 o/oo in June. The range in salinity extremes was least (12 o/oo) for the 

channels (Fig. 5). 

Silt-Clay and Organic Content of Sediments 

The silt-clay and organic content of surface sediments reflect the overall 

hydrology and depositional characteristics of the environment. Both parameters 

also are influenced by the presence and density of seagrasses, in part because 

seagrasses modify hydrodynamic and depositional characteristics of flowing water 

(Fonseca et al. 1983; Fonseca and Fisher 1986) and because they are a source of 

organic matter. We found a great deal of variability among sampling stations in 

both silt-clay and organic matter content of the sediments, and a weak 

correlation between the two parameters (r = 0.397, p < 0.001). The weakness of 

this relationship was surprising since many studies in estuarine areas have 

demonstrated a strong relationship (Kenworthy et al. 1982; Chester et al. 

1983). Our observation may be a reflection of the large extents of seagrass 

meadows and the>generally low current regimes characteristic of Florida Bay, 

Coot Bay and Whitewater Bay (Tabb and Dubrow 1962; Shomer and Drew 1982). In 

general, low currents would result in a generally reduced flushing of 

allochthonous organic matter from the meadows, while a combination of low 

current circulation and extensive meadows would result in silt-clay being 

filtered from the overlying water near the leading edge of a meadow as it moves 

over the meadow. In addition, land drainage is primarily from the mainland 

lying to the north, and there are generally low currents in that area. Thus, 

material probably settles out close to shore. Therefore, a great deal of 

inorganic matter may be added along the mainland border, while in the grass 

meadows large quantities of seagrass organic matter may be added to the 

sediments with little added silt-clay inorganic particle sizes. 
Table 3. Mean values for environmental and biological variables that were 

measured during 1984 and 1985 in Whitewater Bay, Coot Bay and 

Florida Ray. Data are presented as mean stratum values (see Text 

for strata locations. 

-- 

Parameter Stratum 

I I I11 IV 

Temperature ( 'C) 26.7 

Salinity (o/oo) 36.2 

Organic matter (%) 8.5 

Silt-Clay (%) 54.1 

Sediment depth (m) 

Water depth (m) 

Thalassia shoots (No/m2) 514 

Thalassia standing crop 58.6 

( gdw/m2 

Halodule shoots (No/m2) 2 1 

Halodule standing crop 

( gdw/m2 1 

Syringodium shoots (~o/m2) 0 

Syr ingodium standing crop 0 

( gdw/m2 

Ruppia shoots (~o/m~) 

Ruppia standing crop (gdw/m2) 0 
Table 4. Avera2e monthly temperature and salinity values for each strata. 

Stratum Stratum St rat urn Stratum Stratum 

Year Month I I I I1 I . IV - v 
Our data on silt-clay and organic matter in the sediments suggest that 

Whitewater Bay, Coot Bay and Florida Bay are depositional environments. The 

mean silt-clay content of Florida Bay ranged from 47.0% to 62.9%, and for Coot 

Bay and Whitewater Bay it averaged 54.1% (Table 3). The central portion of 

Florida Bay (Stratum 11) had the lowest mean value (47%) while the channel 

stations (stratum Iv) had the highest silt-clay levels (63%). There was a 

difference among strata (ANOVA, p < 0.05), and a SNK range procedure indicated 

the differences were between these two strata alone. The Coot Bay-Whitewater 

Bay had silt-clay levels intermediate to but not different from Stratum I and 

I11 in Florida Bay. The high silt-clay levels of the channels were surprising 

but may be due to the fact that most channels sampled do not have high current 

flows and have relatively high densities of seagrasses (see later) that help to 

retain this particle size. The origin of this silt-clay material in the 

channels is unknown. 

A discernable pattern was observed in the distribution of silt-clay content in 

Florida Bay (Fig. 11) but not in Coot Bay or Whitewater Bay (Fig. 12). In 

Florida Bay, silt-clay values generally exceeding 55% were prevalent in a band 

along the northern and northeastern boundary (Fig. 11). The high silt-clay area 

to the north encompasses the northern subenvironment (Schomer and Drew 1982) but 

extends into Florida Bay to a greater extent than the boundary drawn for this 

subenvironment. These high values probably are a direct result of land 

drainage. 

With the exception of the eastern portion of Florida Bay (Stratum I), average 

organic levels generally exceeded 10%. There was a significant difference 

(ANOVA, p < 0.001) among strata with the eastern portion of Florida Bay 

displaying the lowest overall level (8.5%) and sediments of the Coot 

Bay-Whitewater Bay stratum having the highest mean organic matter content 

(18.4%). Strata 11, 111 and IV were similar and significantly different from 

stratum I (SNK, < 0.05). There was a great deal o? variability in data among 

stations (Fig. 13) with no discernable seasonal trends. We believe that the 

variability in part resulted from the variable densities and species of 

seagrasses in the habitats from which the sediment samples were taken. 

The high levels of organic matter in'the sediments of Coot Bay and Whitewater 

Bay probably result largely from decay of mangrove leaves, with some 

contribution by Ruppia maritima and Chara hornmanni, while seagrasses are the 

major contributor to the organic levels in Florida Bay. Sampling and stable 

carbon and nitrogen analyses by Harrigan (1986) support this suggestion. The 

relatively low organic content of Stratum I sediments is coincident with areas 

of lowest overall seagrass density and biomass (Table 3) and will be discussed 

later. 

General patterns of distribution of sediment organic content were evident in 

Florida Bay (Fig. 14) but not in Coot Bay and Whitewater Bay (Fig. 15). 

Sediments having organic levels < 15% were present primarily in the eastern and 

northeastern portion of Florida Fay and between Flamingo, East Cape and the 

western tips of Dildo Key Bank and First National Bank. Comparatively, high 

sediment organic levels (> 15%) exist in the western and northwestern portion of 

the bay (Fig. 14). We believe that these patterns in Florida Bay probably are a 

function of seagrass density and distribution. The area of < 15% organic carbon I generally occurs in areas of relatively low standing crops 07 seagrasses while 

the region having > 15% organic carbon has relatively high above-ground seagrass 

biomasses. 
Figure 11. Distribution of average percent sil t-clay of the sediments in the 

area of Fl ori da Bay sampled. Hatched areas represent si 1 t-cl ay 

levels - > 55%. 
I 0 1000 3 . . - motor. 

BUTTONWOOD 

CANAL 

Figure 12. Distribution of average percent sil t-clay content of the 

sediments of eastern Whitewater Bay (upper) and Coot Bay (lower), 
- F F r 

Y r v 

a 

tE H 0 

I 1 I VlVQ ON' o 

3. 

C, 0 0 0 

a L Cf) CU r 

a-F 

Lc, 

c, L 

wrc, 

~B'E -I- 
96 Organic Matter 

Figure 14. Distribution of average sediment organic matter in 

Florida Bay. 
% Organic Matter 

y-TARPON CRICK 

Figure 15. Distribution of percent organic matter in eastern Uhitewater Bay (top) and Coot Bay. Hatched area represents - > 15% organic matter* 

32 
Sediment Depth 

There was a significant difference in the depth of sediments among the five 

strata (ANOVA, p < 0.001) (Fig. 16 and 17). Western Florida Bay (Stratum 111) 

had thicker sediments than either the central area (11) or the channels (IV) 

sampled; both of these latter areas pdssessed thicker sediment veneers than 

either Stratum I or Stratum V (Table 3). Western Florida Bay generally had 

sediment depths > 1.0 m while the eastern portion had depths < 1.0 m. This 

western stratum has extensive, well developed carbonate mud bznks . Thick 

sediments (> 1.0 m) extend into the basin between Calusa Keys and Corinne Key 

(Fig. 16). Two pockets of shallower sediments (< 1.0 m) occurred in the area 

around Blue Bank and southwestern Rabbit Key Bas% and in western Johnson Key 

Basin. 

The distribution of sediments less than and greater than 1 m thick in Florida 

Bay generally coincided with the respective distribution of low (< 15%) and high 

(> 15%) sediment organic levels and low and high seagrass standing crops (see 

later). This suggests that, if seagrasses influence sediment organic levels 

significantly, grasses are not as well developed in the shallower sediments. 

Zieman and Fourqurean (1985) in a study of the distribution of seagrasses in 

Florida Bay, also noted that the western area had a much thicker sediment depth 

than does the eastern section. Our values and areas of various sediment 

thicknesses generally coincide with those of Zieman and Fourqurean (1985). 

Coot Bay and Whitewater Bay had sediments that did not exceed a thickness of 1.5 

m (Fig. 17). Sediments at Coot Bay stations only exceeded a thickness of 1.0 m 

at the mouth of Tarpon Creek. In Whitewater Bay, the northeast section had a 

consistently thin sediment veneer < 0.2 m, while many of the remaining stations 

had sediment thicknesses of >0.2 to 0.4 m. 

Standing Crop and Shoot Density of Seagrasses 

To be of significance as a nursery area, a habitat must provide protection from 

predators, a substrate for attachment of sessile stages, or a rich and varied 

food source (Thayer et al. 1978). Seagrass habitats fulfill these criteria 

with their high productivity and blade densities as well as the normally rich 

and varied flora and fauna that occur. Numerous publications have documented 

the use of seagrass meadows by fishery organisms (e.g., Adams 1976, Weinstein 

and Heck 1979, Orth and Heck 1980, Stoner 1982, Weinstein and Brooks 1983), and 

have demonstrated that plant density and species composition can influence the 

abundance and composition of fishes that utilize a seagrass habitat. The 

following section of this report provides a description of the distribution, 

abundance and biomasses of seagrasses we collected during our sampling program. 

Data are analyzed in conjunction-with previously discussed environmental 

parameters. Data are later utilized in our discussion of fish communities to 

describe interrelations among fishes, and specifically target species, and 

habitat variables. 

The distribution, abundance and species composition of the seagrasses differed 

among strata and, generally, there was high variability among stations in any 

single strata. The initial premise upon which we based our subdivision of areas 

into two major regions, i.e., Coot Bay-Whitewater Bay and Florida Bay, was that, I 

because of the greatly different salinity regimes of the two areas, seagrass 

composition and possibly fishery communities would differ. The further 

subdivision of open water areas in Florida Bay into three strata was based on 
Figure 16. Distribution of rangesin sediment thickness at Florida Bay 

sampling stations. Hatched area represents sediments - < 1.0 m thick. 
- 1000 

motors 

1 

COOT BAY 

BUTTONWO~~ CANAL 

Figure 17. Distribution of ranges in sediment thickness in eastern Whi tewater 

Bay (upper) and Coot Bay (lower) sampling stations. 6 
the premise that there was a general increase in the standing stock of Thalassia 

testudinum from the northern-northeastern portion of Florida Bay to the 

western-southwestern section of the sample area (Zieman pers. comm.). We had 

projected an average standing crop of Thalassia that would be lowest in 

Stratum I; intermediate in Stratum 11, and highest in Stratum 111. This 

premise, in fact, did not hold up for Thalassia standing crop or shoot numbers, 

both of which were higher in the central stratum (Stratum 11) (Table 3). 

When data for Thalassia, Syringodium filiforme, and Halodule wrightii were 

evaluated together, however, total plant standing crop and shoot density were 

highest in the western portion. Throughout the entire study area there were 

highly significant (p < 0.001) correlations between standino croD and shoot 

density for the four submerged aquatic species: Thalassia (r = 0'.7891), Halodule 

(r = 0.9188), Syringodium (r = 0.9142) and Ru im9804). Total seagrass 

standing crop averaged 221, 206 and 59 g dw*or Strata 111, 11, and I, 

respectively, with corresponding shoot density averages of 1719, 1024 and 

5350m-~ (Table 3). Mean values for the channel areas (Stratum IV) were 230 g 

dw~m-~ and 1866 shoots-w2. In the Coot Bay-Whitewater Bay stratum, where 

Halodule and Ruppia maritima predominated, values were 8.3 g-m-2 and 431 

~hoots-m-~ for all stations sampled. Strata V and I possessed significantly 

lower average seagrass standing crops than the other strata which did not differ 

from one another (SNK analysis; p < 0.05). 

Western Florida Bay (Stratum 111) and channel areas (Stratum IV) throughout the 

bay displayed the greatest diversity of seagrass species, and this plant species 

diversity may be important to the distribution of juvenile fishes. Although 

Thalassia dominated the standing crop biomass of seagrasses in Florida Bay (Fig. 

18 and 191, Syringodium and Halodulo contributed substantially to shoot 

densities in open water areas of western Florida Bay and i? channels, 

respectively (Figs. 20 and 21). Thalassia was present at almost every site in 

Florida Bay that had seagrasses, and it was only absent in our samples near 

Gibby Point in Snake Bight (pure stand of ~alodule), at the entrance to Sandy 

Key Basi? (station 5-2) and near Middle errnations 2-1, 3-2) where 

Syrinqodium occurred in pure stands or mixed with Halodule (Figs. 18 and 20). 

These areas are in the general vicinity of where larval spotted seatrout and 

juvenile seatrout were routinely collected. Yalodule dominated several of the 

channels and was present in most (Figs. 19 an-syringodium was the only 

species we collected in Man of War Channel, and was a major component of the 

eastern end of Rocky Channel, and in several other channols (Fig. 21). In many 

gf the channels we sampled, Thalassia was present at one or both ends while the 

other species frequently were more toward the center. 

Several stations had no seagrasses. Seagrasses were absent slang the 

northwestern shoreline (Fig. 20) between East Cape and Curry Key. Four channels 

(Fig. 21) also lacked seagrasses. Channels 3 and 5 are both high current areas 

with exposed bedrock, while channel 16 and channel 38 both had sediments about 1 

m thick but were highly turbid. Here, light penetration may limit the 

development of seagrasses. 

The largest seagrass standing crops that we sampled in Florida Bay coincided 

with relatively thick sediments characterized by elevated levels of organic 

matter (Figs. 14 and 16), suggesting that seagrasses tend to grow most 

luxuriously in deeper sediments. There were significant (p < 0.001) relations 

between total standing crop or shoot number and sediment organic content > 15%, - 
STANDING CROP (gem-3 

Habduk-Sdkl Black 

Thalassia - - cram Hatch 

Open 

Figure 18. Distribution of seagrass standing crop ranges in Florida Bay. 

Hatched represents Thal assi a tes tudi num, sol id represents' Halodule wrighti i and open represents ari ngodi urn fil iforne. 
Halodule - Solid Black 

Thalassia - Cross Hatch 

Syrinaodlum - Open 

Figure 19. Distribution of seagrass standing crops in channels sampled in 

Florida Bay. Hatched represents Thalassia testudi num, sol id 

represents Halodule wrighti i , and open areas represent 

Syri ngodi urn fi 1 i forme. 
although the correlations were not remarkable, r = 0.5154 and 0.4723 (N = 105), 

respectively. The overall shallowest veneer of sediment and lowest organic 

levels generally corresponded and occurred throughout Stratum I. Here, seagrass 

standing crops normally were < 50 gem-2. This stratum had a significantly lower 

(p < 0.001) overall standing crop of Thalassia (59 gem-2) than did the other 

areas in Florida Bay, while the remaining non-channel strata had high levels of 

organic matter and relatively deep sediments. 

Zieman and Fourqurean (1985), in their analysis of the seagrasses of Florida 

Bay, observed a generally increasing trend of Thalassiastanding crop in a 

northwesterly direction from the Florida Keys to the mainland. We observed a 

trend for increasing seagrass standing crops in a similar direction from the 

Florida Keys only in the central stratum (Stratum 11) (Fig. 18). In eastern 

Florida Bay (Stratum I), 13 of the 35 stations sampled had standing crop values 

> 50 These stations are not in the northern portion of this stratum, but 

instead are either south of Crane Keys or form an arc from Ramshorn Shoal to 

Captain Key and then to Calusa Key Basin and Black Betsy Key (Fig. 18). In 

western Florida Bay (Stratum 111), standing crop levels we observed were higher 

in Blue Bank Basin, southeastern Johnson Key Basin, and western Rabbit Key Basin 

than in the area to the west between Sandy Key Basin, Frank Key, Flamingo and 

East Cape. An area south of Barnes Key also had a relatively high standing crop 

of Thalassia (490 Thus, the trend observed by Zieman and Fourqurean 

(19malassia standing crops was not as evident in our study. This 

disparity may be a reflection of the stratified random sampling design we used 

and the fact that all seagrass samples were taken from the approximate center of 

each grid cell; triplicate samples taken, however, were similar and we believe 

give an accurate picture of plant characteristics at the stations sampled. 

There was a general trend for total seagrass shoot density to increase in a 

northerly direction in Stratum 111, and this was due to the presence of 

Syringodium and Halodule. 

Channel areas near the Florida Keys generally had higher seagrass standing crops 

than did channels on the north and northwestern portion of Florida Bay. In the 

northern portion of Florida Bay, only the channels leading from Johnson Key 

Basin had high standing crops. In the eastern portion, however ,.. channels 

between Cross Bank, Bob Allen Keys, Panhandle Key and Barnes Key contained a 

high abundance of seagrass, and normally had more than one seagrass species 

present (Fig. 19). 

Whitewater Bay and Coot Bay had the lowest overall abundances of seagrasses of 

the areas sampled. During the period of study, Halodule was the predominant 

species collected in Whitewater Bay (Figs. 22 anmere it had a mean 

standing crop of 6.0 g*m-2 and shoot density of 534-m-2. Lowest densities were 

in the northern portion of the sample area. Ruppia maritima also was present in 

Whitewater Bay, with an average standing crop of 3.4 g~m-~ and a shoot density 

of 366*md2. The northeast portion had a very large Ruppia population in March 

1985 when there was a shoot density of 8700-m-2 with a standing crop of 77 2 gem- . Other stations sampled in this northern portion either had low 

quantities of Halodule in sediment pockets among the bedrock, or were void of 

vegetation. Many stations in Coot Bay also were devoid of seagrasses (Fig. 22), 

and, where seagrasses were present, Ruppia was most prevalent. Ruppia had a 

mean standing crop of 5.3 g-m-2 and shoot density of 636.111'~ for the stations 

sampled. ~aiodule, which also was present, had a mean standing of 1.3 g-m-2 and 1) 

a shoot density of 109.m-2. 
Figure 20. Distribution of seagrass shoot density in Florida Bay. Hatched 

areas represent Thal assia tes tudi num, sol id represents Hal odule 

wri qhti i , and open represents S~ringodi um fi 1 i forme. 
SHOOT DENSITY (No.. mQ) ji 

CHANNELS 

Figure 21. Distribution of seagrass shoot densi t.y in channels sam~led in 

Florida Bay, ~atched represents ~halassia testudinurn,' sol id 

represents Hal odul e wri ghti i , and open represents Syri ngodi um 

fil Sforme. 
In March 1984, with the assistance of Everglades National Park personnel, we 

mapped the bottom characteristics of Coot Bay. A grid of concentric arcs spaced 

approximately 100 m apart was established. With guidance from a person using a 

theodolyte system on sh'ore, a bottom sample was taken with a clam rake every 

minute or 100 rn along the arc. The boat was kept in motion during the operation 

and one investigator identified the rake contents and recorded the data. Figure 

24 is a diagram of Coot Bay showing the results of this study. During the 

period May 1984 - June 1985, Chara had expanded its area to the east of Tarpon 

Creek to cover most of that embayment. This alga also had expanded to cover 

large extents of the bottom in the northeast portion of the bay, so much so that 

we were unable to sample several stations. 

Summary of Environmental Variables 

Water temperatures fo1,lowed a typical seasonal cycle with highest values in May 

through September, and lower values during autumn through spring. Salinity was 

significantly lower in Coot Bay and Whitewater Bay than in Florida Bay, and 

there were no significant differences in salinity among Florida Bay strata. 

There was a weak but significant positive correlation between the silt-clay 

content of sediments of the study area and their organic content. The highest 

silt-clay contents appeared to be related primarily to land runoff in that the 

northern boundary of the Florida Bay study area from Flamingo to Madeira Bay had 

the highest silt-clay'levels. Both Whitewater Bay and Coot Bay had high levels 

of silt-clay content suggesting depositional environments with land runoff as 

the primary source of this sediment particle size and probably a large portion 

of the sediment organic matter. Organic matter levels tended to correspond to 

sediment thickness and general seagrass density, at least in Florida Bay. 

There was an overall trend of comparatively low overall seagrass abundance in 

areas of shallow sediments (< 1 m thickness) having relatively low sediment 

organic content (< 15%). These data suggest that there is restricted seagrass 

population developdent in thinner veneer sediments and hence, a reduced organic 

matter buildup in the sediments. 

The five strata differed in environmental variables and habitat characteristics. 

Stratum V (Coot Bay and Whitewater Bay) had low salinities (R = 17.2 o/oo), 

intermediate silt-clay contents, and the highest overall sediment organic 

content of the entire study area (Table 3). Where seaarasses were ~resent. 

Halouule wright ii was more- common in whitewater Bay while Ruppia mar it ima was 

prevalent in Coot Bay for the study period as a whole. 

The channel habitat in Florida Bay (Stratum IV) was characterized by 

intermediate sediment organic levels and sediment depth relative to other 

strata, but the highest overall silt-clay content of the strata sampled (Table 

3). This stratum had the hiahest overall standina croD and densitv of 

seagrasses, and all three species of seagrasses (Thalassia, ~aloduie and 

Syringodium) we collected in Florida Bay were present in many of the channels. 

Halodule was more prevalent in this stratum than elsewhere. Channels in the 

southeastern and southwestern portion of the bay tended to have higher densities 

of seagrasses than channels sampled elsewhere. 

Stratum I11 represented an open water, non-channel area of western Florida Bay 

which has the mst direct exchange of water with the Gulf of Mexico. This area 

is characterized by extensive carbonate mud banks, and our sampling did not 

include these banks. The sediments of this area generally had high silt-clay 
Standing Crop 

0 1-10 

0 10-50 

... . . 100. 

0 

L 

1000 

meter* 

CREEK 

COOT BAY 

TO 

COOT BAY 

Figure 22. Ranges of seagrass standing crop -in eastern Whltewater-Bay (upper) , and Coot Bay (1 ower) . 

4 3 
Shoot Number per m2 

' o 1-500 

0 500- 1000 

01000-2000 

130. . -136' . 

COOT BAV 

. 10 loo0 

matan 

Figure 23. Ranges of seagrass shoot density in eastern Whi tewater Bay (upper) 

and Coot Bay (lower). 

and organic matter levels (Table 3). This stratum was the most diverse of the 

non-channel areas of Florida Bay in terms of seagrass species composition, and 

exhibited the highest overall densities of Syringodium but not Thalassia. 

Intermediate densities of Halodule also were present. No seagrasses were 

observed at sampling locations between East Cape and Curry Key north of Middle 

Ground. 

Stratum I1 represented the interior of our sampling universe in Florida Bay 

(Fig. 4). Sediments generally had intermediate organic levels and low overall 

silt-clay contents. However, stations along the northern boundary of this 

stratum had high silt-clay contents, presumably from land runoff. Both 

Thalassia and Halodule were present, and Thalassia standing crops were overall 

greater here than in other strata. This was the only stratum where an 

increasing standing crop of Thalassia in a northerly direction was observed. 

Stratum I, had the lowest overall sediment organic content, shallowest sediment 

veneer, and second lowest sediment silt-clay content. Thalassia was the 

dominant seagrass of this stratum and only small amounts of Halodule were 

present. The average shoot density and standing crop of seagrasses were lower 

here than in any other stratum in Florida Bay. 

Distribution of Fish Communities 

We first present general distributional trends of juvenile fish communities and 

then compare distributions of fishes among strata. We go on to examine the 

association of fishery organisms with environmental parameters in an attempt to 

discriminate their roles in structuring fish communities using habitats in 

estuarine and marine areas of the Park. These associations do not imply cause 

and effect but may provide the bases upon which to design experiments to test 

hypotheses derived from the study. As will be readily observed, the fishes we 

collected were dominated by juveniles as well as by adults of small forage 

species. 

Relative Abundance and Biomass 

There were 93 species and 43 families collected by surface and otter trawls 

during the nine stratified random surveys between May 1984 and June 1985 (Tables 

5 and 6). Of the total collected (43,578), 71% were taken by the two-boat otter 

trawl. A total of 41 families and 91 species were collected with the otter 

trawl, while 61 species representing 29 families were collected with the surface 

trawl. Only four species were exclusively collected in the surface trawls: 

bonnethead shark, balao , sharksucker and white mullet. Thirt y-four species were 

collected exclusively in the otter trawl. Thus, 56 species were common to the 

two gear types. The representation of the same species in surface and bottom 

samples may have been largely the result of our sampling in shallow waters where 

the two gears overlapped within the water column. 

There were only a few of the dominant species that were common to both trawl 

gear. Eleven species contributed 91.0% of the total number of fish collected by 

otter trawl: rainwater killifish (~ucania parva) (28.6%); silker jenny 

(Eucinostomus ula ) (27.7) ;- pinf ismdon rhomboides ) (15.5) ; bay anchovy 

(Anchoa mitchilll % (7.0); goldspotted killifish (Floridichth s car io) (2.8); 

w~r~ulon plumieri) (1.9; dusky pipe-h&ridae) 
Table 5. Listing of fishes collected by bottom trawl and their total abundance 

in each stratum sampled in Everglades National Park estuarine and 

marine waters during 1984 and 1985. Scientific and family names are 

shown. For strata locations see Figures 2-5 and text. AFS 

standardized names used throughout. 

STRATUM 

~arnily/Scient if ic Name -- Common Name I I1 I11 IV V TOTAL 

Dasyatidae - stingrays 

Dasyatis americana -- southern stingray - - - 1 - 1 

Elopidae - tarpons 

Elops saurus -- ladyfish - - - - 1 1 

Albulidae - bonef ishes 

Albula vulpes -- bonefish - - - 3 - 3 

Clupeidae - herrings 

Brevoortia smithi -- yellowfin - - - 15 - 15 

menhaden 

Opisthonema oglinum 

redear sardine 

scaled sardine 

dwarf herring 

Atlantic thread 

herring 

Sardinella aurita -- Spanish sardine 

Enqraulidae - anchovies 

-- striped anchovy - - 

-- bav anchovy 10 - 

Synodontidae - lizardfishes 

Synodus foetens -- inshore 20 10 

lizardfish 

Ariidae - sea catfishes 

-7 

Arius felis -- hardhead catfish 1 - 

Baqre marlnus -- gaf ftopsail - - -. catfish 

Batrachoididae - toadfishes 

Opsanus - beta -- gulf toadfish 5 100 

Gobiesocidae - clingfishes 

Gobiesox strumosus -- skilletfish - - 

Antennariidae - frogfishes 

Histrio histrio -- sargassumfish - 1 

Ogcocephalidae - batfishes 

Ogcocephalus radiatus -- polka-dot 

batfish 
Table 5. (Contd) 

Fmily/Scientific Name -- Common Name I I1 I11 IV V TOTAL 

Bythitidae - viviparous brotulas 

Gunterichthys longipenis-- gold brotula - - - 1 

Exocoetidae - flyingfishes Chriodorus at her inoides -- hardhead - - 14 - 3 

halfbeak 

Hemiramphus brasiliensis-- ballyhoo - 18 - - 

Hyporhamphus uni fasciatus- halfbeak - 2 117 - 

Belonidae - needlefishes 

Strongylura notata -- redfin 4 20 2 7 

needle fish 

Stronl~ylura timucu -- tirnucu 2 1 8 - 

Cyprinodontidae - killifishes 

Floridichthys carpio -- goldspotted 115 224 72 443 

killifish 

Lucania parva - rainwater 

killifish 

Poeciliidae - livebears 

Poecilia latipinna -- sailfin molly - 3 - 2 

Atherinidae - silversides 

Atherinomorus stipes -- hardhead silverside - 1 - 318 

H oatherina -- reef silverside - - - 

~e"sis 

1 

Membras martinica -- rough silverside - - 2 - 

Meniafa peninsulae - tidewater - - - - 

1 silverside 

Syngnathidae - pipefishes lined seahorse 

dwarf seahorse 

pugnose pipef ish 

dusky pipefish chain pipef ish 

gulf pipefish 

Serranidae - sea basses 

Di lectrum formosum -- sand perch - - 1 - - 

+U-Or -- barred hamlet 

1 

- - 4 - - 4 

'maWycterowrca dcrolepis -- gag - - 1 - - 1 
Table 5. (Contd) 

Famil y/Scient if ic Name -- Common Name I I1 I11 IV V TOTAL 

Carangidae - jacks 

Caranx + cr sos 

Caranx h ppos 

Oligoplltes saurus 

Trachinotus -nus 

Lutjanidae - snappers 

Lutjanus griseu; 

Lut anus synagr s 

Ocyurus chrysurus 

Gerreidae - mojarras 

Eucinostomus +- ar enteus 

Eucinostomus gu a 

-- blue runner - - 

-- crevalle jack - - 

-- leatherjacket - - 

-- Florida pompano - - 

-- gray snapper - - 

-- lane snapper 2 - 

-- yellowtail 3 - 

snapper 

-- spotfin mojarra 58 42 

-- silver jenny 1495 878 

Haemulidae - arunts 

Haemulon aurhineatum -- tomtate - - - 3 - 3 

Haemulon flavolineatum -- French,grunt - - - 7 - 7 

Haemulon p;rr;i -- sailor s choice 6 1 9 40 - 76 

Haemulon p urn eri -- white grunt - - 40 168 - 588 

Haemulon sciurus -- bluestr iped 5 - 173 - 89 

grunt 

Ortho ristis --dEG 

-- pigPish 1 1 28 136 7 393 

Sparidae - porgies 

Archosargus -- sheepshead 5 38 7 1 - 61 

probatocephalus 

Calamus arctifrons 

Calamus leucosteus 

Lagodon rhomboides 

grass porgy 

whitebone porgy ' 

pinfish 

Sciaenidae - drums 

Bairdiella chr soura -- silver perch 2 4 38 45 122 481 

C nosdionne u osus -- spotted seatrout 1 

-7- 

- 8 10 10 49 

Mentic rrhus americanus -- southern kingfish - - - - 2 2 

Ephippidae - spade fishes 

Chaetodipterus faber -- Atlantic spadefish - 1 1 4 - 6 

Scaridae - parrotfishes 

Cr totomus roseus -- bluelip parrot f ish - - - 2 - 

*us t a -- emerald parrotfish - - 2 4 - 

Mugilidae - mullets 

Wgil cephalus -- striped mullet - - 2 1 - 3 
- - - - - - - 

Fami ly/Scientif ic Name -- Common Name I I1 I11 IV V TOTAL 

Sphyraenidae - barracudas 

Sphyraena baracuda -- great barracuda 10 6 7 10 1 

Sphyraena guachancho -- guaguanche, 1 - - - - 

Clinidae - clinids 

Chaenopsis limbauqhi -- yellowface 1 - - - - 

pikeblenny 

Paraclinus fasciatus -- banded blenny 2 - 2 29 - 

Paraclinas marmoratus -- marbled blenny - - 2 23 - 

Blenniidae - combtooth blennies 

Chasmodes saburrae -- Florida blenny 2 - 5 17 2 

Callionymidae - dragonets 

Callion mus -- spotted dragonet 6 10 - 16 - 

&t us 

Gobiidae - gobies 

Gobiosoma robustum -- code goby 4 4 2 53 3 

-- Eg%E %%psis -- 

clown goby 13 6 - 23 33 

banner goby 9 - - 4 - 

Triglidae - searobins 

Prionotus scitulus -- leopard searobin - - 1 1 - 

Prionotus tribulus -- bighead searobin - - - 1 - 

Bothidae - lefteye flounders 

-- ocellated flounder - 1 1 - - 

Soleidae - soles 

Achirus lineatus -- lined sole - - 1 3 1 

~rinectem tus-- scrawled sole - - - 1 - 

Trinectes _fe macu atus -- hogchoker - - - - 1 I 

Cynoglossidae - tonguefishes 

Symphurus p1aqius.a -- blackcheek - - 1 2 - 

tonguefish 

Balistidae - leather jacks 

Aluterus schoe fi -- orange filefish - - 4 - - 

bbnacanthdtus -- fringed filefish - - 106 1 - 

Macanthus -- planehead filefish - 3 17 - - 
Table 5. (Contd) 

- 

Famil y/Scient i Pic Name -- Common Name I I1 I11 IV V TOTAL 

Ostraciidae - boxfishes 

Lacto hr s uadricornis -- scrawled cowfish 6 - 18 12 - 36 

-- trunkfish - - 1 - - 1 

Tetraodontidae - puffers 

S oeroides ne helus -- southern puffer 3 6 15 8 3 35 

i -- bandtail puffer 1 - 1 5 - 7 

Diodont idae - porcupinefishes 

Chilomycterus schoepfi -- striped burr fish 2 4 17 6 - 29 
silverside [Atherinomorus stipes) (1.0) ; and gulf toadfish (Opsanus beta) (1 

Bay anchovy dominated the surface trawl catches (26.7) followed by hmeak 

(Hyporhamphus unifasciatus) - (12.3),; reef silverside (Hypoatherina 

rainwater killifish (1.7); and- S~anish 5 

(Sardinella aurita) (1.3). 

The dominant fish species in our collections were similar to those observed in 

other studies that have been carried out on fish distribution in south Florida. 

Tabb and Manning (1961) reported that anchovies, mojarras and pinfish were 

dominant in trawl collections i? northern Florida Bay and Whitewater Bay. Tabb 

(unpubl. data), recorded a somewhat different species compliment from the area 

of Eagle Key and Murray Key during 1964-1966, including: fringed pipefish 

(Micro nathus crinigerus ) , silver jenny, spot f in mo jarra, (Eucinostornus 

ar ??7- enteus , piifish, planehead filefish (Monocanthus his idus), white grunt, 

lane snapper (Lutjanus syngaris) and pigfish. Schmidt -fT 1979 found that striped 

and bay anchovies constituted over 48% of the total trawl catch for western and 

southwestern Florida Bay, followed by mojarra, killifish, and pinfish. 

Together, these anchovies composed less than 15% of our total catch using two 

gears. Weinstein and Heck (1979) observed that silver perch, pinfish, silver 

jenny, white grunt, pigfish, and lane snapper were among the dominant species in 

seagrass beds near Cape Romano and Marco Island, similar to what Tabb and 

Manning (1962) observed for seagrass areas of Florida Bay. Carter et al. (1973) 

and Colby et al. (1985), working in the Ten Thousand Island area, reported a 

similar compliment of dominant species as those we found in the Everglades 

National Park, but both reported a preponderance of species with pelagic 

affinities even though several gear types were used. 

Those species that domiqated the overall catch numerically did not necessarily 

dominate the total wet weight gf fish collected. During the stratified random 

sampling phase of this study, 144 kg wet weight of fish were collected by otter 

trawls (Table 7) and 49.4 kg were collected in surface trawls (Table 8). Twelve 

species dominated the biomass of fishes collected by otter trawls: pinfish 

(29.3%), silver jenny (16.8), hardhead catfish (Arius 

7- 

felis), (10.3), pigfish 

(4.8), white grunt (4.1), gulf toadfish (3.7), sllver perch (3.1), gray snapper 

(2.8), gafftopsail catfish (Baqre marinus) (2.7), scrawled cowfish (~actophrys 

uadricornis) (2.11, inshore lizar~(~ynodus foetens) (1.8) and bluestriped 

'blon sciurus) (1.5). The gray snapper and the latter five species on 

this list were not among the numerically doininant species, but together 

represented greater than 21% of the total biomass collected by otter trawl 

sampling. Nine species represented 91.2% of the total biomass collected, and 

only three of these were not among the numerically domi~ant species. In 

decreasing order, the species which dominated the biomass collected by surface 

gear were: halfbeak (32.5%); redfin needlefish (28.2); hardhead halfbeak (9.5); 

ballyhoo ha emir am hus brasiliensis) (7.1) ; timucu (Stron lura timucu) (3.9); 

bay ancho~~ugh silverside 2.4 pin fish *silver jenny 

(1.9). 
dl3163 6. Listing of species and abundances of fish collected in Everglades ~ational 

Park during 1984 and 1985 using a surface trawl. Refer to text for 

strata locations. 

-- - - - -- 

Family/Scientific Name -- Common Name I 11 I11 I V V TOTAL 

Sphyrnidae - hammerhead sharks 

Sphyrna tiburo -- .bonnethead 

Clupeidae - herrinas - 

Brevoortia smithi -- yellowfin 

menhaden 

Harenqula humeralis -- redear sardine 

Harengula jaguana -- scaled sardine 

Jenkinsia lamprotaenia -- dwarf herring 

Opisthonema oqlinum -- Atlantic thread 

herr ina 

Sardinella aurita -- spanis6 sardine 

Enaraulidae - anchovies 

~nchoa he setus 

Anchoa -%- mltchl li 

-- striped anchovy 

-- bay anchovy 

Svndontidae - lizardfishes 

synodus foetens -- inshore 

lizardfish 

Ariidae - sea catfishes 

Arius felis -- -- - - - hardhead catfish - 5 5 

Bagre marinus -- gaf ftopsail - - - - 1 1 

c a t f i s h 

Batrachoididae - toadfishes 

Opsanus bet a -- gulf toadfish 3 9 2 5 120 

Antennariidae - frogfishes 

Histrio histrio -- saryassumfish 2 - - - - 2 

Exocoetidae - flyingfishes 

Chriodorus ather inof des -- hardhead 322 221 18 150 - 711 

halfbeak 

balao - 1 1 - - 2 

ballyhoo 10 7 45 40 - 102 

halfbeak 134 32 1083 276 7 1532 

Hemiramphus balao -- 

Hemiramphus brasiliensis -- 

Hyporhamphus unifasciatus-- 

Belonidae - needlef ishes 

Stronqylura notata -- 

needlef ish 

strongylura timucu -- t imucu 
Table 6. (Contd) 

Family/Scient if ic Name -- Common Name I I1 V TOTAL 

Cyprinodontidae - killifishes 

Floridichthys carpio -- goldspotted 

killifish 

rainwater 

killifish' 

Lucania parva -- 

Atherinidae - silversides 

Atherinomorus stipes -- hardhead 

silverside 

reef 

silverside 

rough 

silverside 

tidewater 

silverside 

Menidia peninsulae -- 

Syngnathidae - pipef ishes 

lined seahorse 

dwarf seahorse 

pugnose pipef ish 

dusky pipef ish 

chain pipef ish 

gulf pipef ish 

Serranidae - sea basses 

H o lectrus unicolor -- 

'habarred hamlet 

Echeneidae - remoras 

Echeneis naucrates -- shar ksucker 

Carangidae - jacks 

Caranx hi os rtPe -- 

-1 es saurus -- i&k!k~ anus -- 

crevalle jack 

leatherjacket 

Florida pompano 

Lut janidae - snappers 

~uEjanus griseu? 

Lu anus synagrls 

gray snapper 

lane snapper 

Gerreidae - mojarras 

spotfin mojarra 

silver jenny 

Eucinostomus ar enteus -- 

Eucinostomus gu -f- a -- 
Table 6. (Contd) 

Family/Scient if ic Name -- Common Name I I1 I11 IV V TOTAL 

Haemulidae - grunts 

Haemulon p;rr;i -- sailor's choice - - 13 

lG6iiZ% p urn eri -- white grunt - - 4 

Haemulon sclurus -- bluestriped grunt - - 3 

Orthoprischrysoptera -- pigf ish - - 4 

Sparidae - porgies 

Archosargus robatoce hal-- sheepshead 

Laqodon rho o des -- pinfish 

Sciaenidae - drums 

Bairdiella chr soura -- silver perch - - 6 

Cynoscion ne ulosus -- spottedseatrout - 1 - 

Muqilidae - mullets 

Kq!1 cephalus 

Ngll curema 

-- striped mullet - - 1 

-- white mullet 1 - 9 

Sphyraenidae - barracudas 

Sphyraena barracuda -- great barracuda - - - 

Callionymidae - dragonets 

Callionymus pauciradiatus-- spotted dragonet 4 2 - 

Gobiosoma robust um -- code goby - 3 1 

Micr ogobiu-s -- clown goby 6 2 - 

Soleidae - soles 

Achirus lineatus -- lined sole - - 1 1 1 3 

Balistidae - leather jacks 

Monacanthus ciliatus -- fringed filefish 1 - - - - 1 

Ostraciidae - boxfishes 

Lactophrys quadricornis -- scrawled cowfish 1 - - - - 1 

Tetraodontidae - puffers 

Sphoeroides nephelus -- southern puffer 1 1 11 1 - 4 

Diodontidae - porcupinefishes 

Chilomycterus schoepf i -- striped burr fish - - 1 - - 1 
Distribution of Fish Among Strata 

The distribution of total numbers and weight of fish varied among strata for 

species collected by the two gear (Tables 5-8). Western Florida Bay and the 

channels (Strata I11 and IV) consistently displayed a similar and larger fish 

community (otter trawl) ,in terms of numerical abundance, biomass and species 

composition relative to other areas in Florida Bay, Whitewater Bay and Coot Bay. 

Approximately 70% of the total number and wet weight of fish from the Otter 

trawl collections was from these two strata, with a slightly greater overall 

biomass of fish being taken from the channels (Stratum IV). Of the other three 

strata, eastern Florida Bay (Stratum I) exhibited the numerically smallest 

demersal fish community while the interior stratum (I I )displayed the smallest 

demersal fish community in terms of total weight (Tables 5 and 7). Thus, the 

overall fish community collected by otter trawl was numerically larger and 

exhibited a higher overall biomass in those strata (Strata I11 and IV) that 

generally exhibited the largest and most diverse seagrass assemblages (see Fig. 

18). 

The composition of the fish community varied among strata for species collected 

by both gear types (Tables 5-8) but there were numerous species in common. The 

near-gulf and channel strata (Strata I11 and IV) had the largest number of 

species collected by either gear type, while Whitewater and Coot Bay (Stratum V) 

had the lowest. Thus, the Margalef diversity index (S-l/ln N, where S = number 

of species and N = number of individuals) was greatest for Strata I11 and IV 

(6.240 and 7.105, respectively, for bottom trawls and 5.675 and 4.176 for 

surface trawls, respectively) and least for the Whitewater Bay and Coot Bay 

stratum (3.981 for otter trawls and 3.128 for surface trawlsj. 

Venn diagrams were developed to depict the co-occurrence of fish species among 

strata for the survey as a whole. A species-by-strata matrix was constructed 

based on data presented in Tables 5 and 6. Only those species for which there 

were more than 10 individuals in any single stratum were included. Each stratum 

or strata-combination is represented by a ring in the Venn diagram and the rings 

intersect so that the number of species found in all strata is indicated within 

the intersection of all three rings; the number of species found in two of the 

three strata is indicated within the corresponding intersection of those two 

respective rings; and those species unique to a particular stratum are indicated 

within the appropriate ring outside of intersections with,the other two. Two 

comparisons each were made for the otter trawl and surface samples (Figs. 25 and 

26): 1) a comparison of the low salinity stratum composed of Coot Bay and 

Whitewater Bay (V), channels in Florida Bay (IV), and the open water strata of 

Florida Bay (I, I1 and I11 combined); and 2) a comparison of Strata I, I1 and 

I11 in Florida Bay. 

A comparison of open water, low and high salinity, strata with the high salinity 

channel stratum demonstrated that there were numerous species common to all 

areas and that the open water area of Florida Bay (Strata I, I1 and I11 

combined) had a larger complement of co-occurring species than did the other 

areas sampled (Figs. 25 and 26). Ten species were truely ubiquitous in the fish 

community sampled by otter trawl: bay anchovy, rainwater killifish, redf in 

needlefish, spotfin mojarra, silver jenny, pinfish, spotted seatrout 

noscion nebulosus ) , clown goby (~icrogobius ~ulosus ) , hardhead catfish and 

s (?- lver perch. Nine species collected bv surface trawls were common to all of 

these areas: yellowfin (Brevoortia sinithi), menhaden, striped anchovy, bay 

anchovy, redfin needlefish, timucu , rainwater killifish, rough silverside, gulf 
Table 7. Listing of fishes collected by bottom trawl and their total biomass (grams 

wet weight) in each stratum sampled in Everglades National Park estuarine and ;$,~

marine waters during 1984 and 1985. Scientific and family names are shown. -2 

For strata locations see Figures 2-5 and text. AFS standardized names used. 

STRATUM 

Famil y/Scient if ic Name -- Common Name I I1 I11 IV V TOTAL 

Dasyatidae - stingrays 

Dasyat is americana -- southern 

st ingray 

Elopidae - tarpons 

Elops saurus -- ladyfish - - - - 15.2 15.2 

Albulidae - bonef ishes 

Albula vulpes -- bonefish - - - 19.8 - 19.8 

Clupeidae - herrings 

Brevoortia smithi -- yellowfin - - - 73.3 - 73.3 

menhaden 

Harenqula humeralis -- redear - 0.6 - - - 0.6 

sardine 

Harenqula ja~uana -- scaled 0.6 52.3 75.9 25.0 - 153.8 

sardine 

Jenkinsia -- dwarf 1.1 - 0.7 5.8 - 7.6 

herrina - 

lamprotaenia 

Opisthonema oglinum -- Atlantic 64.6 - - 25.9 18.4 108.9 

thread herring 

Sardinella aurita -- Spanish sardine - - - 36.9 - 36.9 

Engraulidae - anchovies 

Anchoa hepsetus -- striped anchovy -. - 11.9 0.2 12.8 24.9 

Anchoa mltchllli -- bay anchovy 1.8 - 13.3 145.7 1624.0 1784.8 

Synodont idae - lizardfishes 

Synodus foetens -- inshore 1418.4 637.0 286.2 71.7 118.2 2531.3 

lizardfish 

Ariidae - sea catfishes 

-- Arius felis -- hardhead 86.9 - 2704.4 3695.2 8314.8 4801.3 

catfish 

Baqre marinus 

- - 

-- gafftopsail 

catfish 

~atrachoididae - toadfishes 

Opsanus beta -- gulf toadfish 41.0 653.7 2702.6 2006.3 2.0 5405.6 

Gobiesocidae - cling fishes 

Gobiesox strumosus -- skilletfish - - 0.9 2.6 - 3.5 

Antennariidae - frogfishes 

Histrio histrio -- sargassumfish - 1.4 - - - 1.4 
Table 7 (Contd). 

STRATUM 

~amily/Scientific Name -- Common Naine I I1 I11 IV V TOTAL 

Ogcocephalidae - bat fishes 

Ogcocephalus radiatus -- polka-dot - - 333.4 - - 333.4 

bat fish 

Bythitidae - viviparous brotulas 

-- gold brotula 

Exocoet idae - flyingf ishes 

Chriodorus -- hardhead 

halfbeak 

ather inoides 

Ts?%is 

ballyhoo 

halfbeak 

Belonidae - needlefishes 

Stronqylura notata -- redfin 0.7 651.7 1.2 2.4 2.6 682.0 

needlefish 

Stronaylura timucu -- timucu 0.8 0.2 3.8 - 42.7 

Cyprinodont idae - killi fishes 

Floridichthys carpio -- goldspot ted 50.7 137.7 82.1 248.4 9.5 

killifish 

~ucania parva -- rainwater 7.9 401.8 637.1 792.6 49.3 

killifish .% 

Poeciliidae - livebears 

Poecilia latipinna -- sailfin molly - 0.9 - 2.4 - 3.3 

Atherinidae - silversides 

Ather inomorus st ipes -- hardhead 

silverside --- - ~ ~- 

Hypoatherina harringtonensis - reef - - - 0.5 - 0.5 

sfiverside 

Membras martinica -- rough silverside - - 1.0 - 13.3 14.3 

Menidia peninsulae -- tidewater - - - - 0.4 0.4 

silverside 

Syhgnathidae - pipefishes 

lined seahorse 

pugnose pipefish 

dusky pipefish 

chain pipef ish 

gulf pipefish 
Table 7 (Contd). 

STRATUM 

Family/Scientific Name -- Common Name I I I 111 IV V TOTAL 

Serranidae - sea basses 

-- sand perch - - 77.9 - - 77.9 

-- barred hamlet - - 43.3 - - 43.3 

Mycteroperca microlepis- gag - - 1.9 - - 1.9 

Carangidae - jacks 

Caranx crysos -- Qlue runner - - 5.8 - - 5.8 

Caranx Qippos -- crevalle jack - - - 1.5 - 1.5 * Oli o lltes saurus -- leatherjacket - - - - 0.2 0.2 

=nus -- Florida pompan - - - 172.2 - 172.2 

Lutjanidae - snappers 

Lu-janus griseu? -- gray snapper - - 934.6 2966.0 200.4 4101.0 

Lu anus synaqris -- lane snapper 30.0 - 418.4 171.8 - 620.2 

Ocyurus chrysurus -- yellowtail 40.7 - - 70.4 - 111.1 

snapper 

Gerreidae - rno jarras 

Eucinostomus arqenteus-- spot f in 255.2 53.8 94.9 350.6 250.3 1004.8 

mo jarra 

Eucinostomus gula -- silver jenny 652.9 2760.0 3087.0 3757.7 4981.0 24238.6 

Haemulidae - grunts 

Haemulon aurolineatum -- tomtate - - - 28.8 - 28.8 

Haemulon -- French grunt - - - 261.4 - 261.4 

flavolineatum 

Haemulon parrai -- sailor's 2.0 0.8 15.3 433.3 - 261.4 

choiceHeemulon plumieri -- white grunt - - 3500.5 2379.7 - 5880.2 iGiiZE sciurus -- bluestriped 24.1 - 37.8 2284.0 - 2345.9 

grunt 

Orthopristis -- pigfish 139.8 72.2 2642.6 3833.9 266.5 6955.0 

chr ysoptera 

Sparidae - porgies 

-- sheepshead - 35.3 292.7 1277.2 107.2 1712.4 

-- grass porgy 65.0 - 692.4 975.9 - 1733.3 

.- ~eucosteus -- whitebone 37.7 - - - - 37.7 

POrQY 

Laqodon rhomboides -- pin?ish 2260.4 2710.8 18677.3 17299.7 1205.5 42153.7 
I STRATUM 

Family/Scientific Name -- Common Name I I I I11 IV V TOTAL 

Sciaenidae - drums 

Bairdiella -- silver perch 97.6 20.5 2724.3 230.2 1658.7 4731.3 

Cynosc v on nebulosus -- spotted 76.4 - 253.1 756.3 29.5 1115.3 

seatrout 

Menticirrhus -- southern - - - - 396.8 396.8 

kingfish 

amer icanus 

Ephippidae - spadefishes 

Chaetodipterus - faber -- Atlantic - 196.1 79.2 331.2 - 606.5 

I spadef ish 

Scaridae - parrotfishes 

Cryptotomus roseus -- bluelip - - - 5.2 - 5.2 

parrot fish 

Nicholsina - usta -- emerald - - 24.5 160.7 - 185.2 

parrot fish 

Wgilidae - mullets 

Wail cephalus -- striped mullet - - 53.9 394.4 - 448.3 

SDhvraenidae - barracudas 

Sphyraena barracuda -- great 

barracuda 

Sphyraena guachancho -- guaguanche 1.0 - - - - 1.0 

Clinidae - clinids 

Chaenopsis limbaughi -- yellowface 1.1 - - - - 1.1 

pi keblenny 

Paraclinus fasciatus -- banded blenny 1.3 - 0.9 27.7 - 29.9 

Paraclinus marmoratus-- marbled blenny - - 16.1 24.0 - 40.1 

Blenniidae - combtooth blennies 

Chasmodes saburrae -- Florida blenny 5.8 - 6.2 32.4 2.0 46.4 

Callionymidae - dragonets 

Callionyrrius -- spotted 2.9 2.8 - 7.2 - 12.9 

dragonet 

pauciradiatus 

I Gobiidae - gobies 

Gobiosoma robusturn -- code goby 1.4 2.9 4.6 18.2 0.7 27.8 

COQ 

-- clown goby 3.0 1.9 - 6.0 17.2 28.1 

-Ehzs 

-- banner goby 2.5 - - 1.2 - 3.7 
Table 7 (Contd). 

STRATUM 

Family/Scientific Name -- Common Name I I1 111 IV V 

Triglidae - searobins 

Prionotus scitulus -- leopard - - 3.9 3.2 - 

searobin 

Prionotus tribulus -- bighead - 

searobin 

Bothidae - lefteye flounders 

Ant lo setta 

*t a 

-- ocellated - 23.9 42.6 - 

flounder 

Soleidae - soles 

Achirus lineatus -- lined sole - - 0.6 30.6 3.9 

Trinectesptus -- scrawled - - - 17.4 - 

stole 

Trinectes maculatus -- hogchoker - - - - 4.1 

Cynoglossidae - tonguefishes 

Symphurus plaqiusa -- blackcheek - - 3.9 6.3 - 

tonguef ish 

Balist idae - leatherjacks 

AAuterus schoepfi -- orange - - 174.5 - - 3 

filef ish 

Monacanthus ciliatus -- fringed - - 544.6 8.8 - a 

filefish --- - 

Monacanthus hispidus -- planehead - 2.1 93.4 - - 

filefish 

Ostraciidae - boxfishes 

Lacto hr s -- scrawled 545.7 - 1279.9 1160.4 - 25 

&nis 

cowfish 

Lactophrys triqonus -- trunkfish - - 98.3 - - 

Tetraodontidae - puffers 

Sphoeroides nephelus -- southern 19.3 271.9 197.7 133.6 217.4 E 

auf fer 

Sphoeroides spenqleri -- bandtail 5.1 - 4.6 175.5 - 1 

Oiodontidae - porcupinefishes 

C~LI.;;Y;~~~US -- striped 46.9 168.8 691.3 460.6 - U 

P burr fish 
Stratum V Strata I, 11, 111 

Stratum IV 

Stratum Ill 

SURFACE TRAWLS 

Figure 25. Diagramnatic representation of the overall simi lari ties and 

differences in numbers of fish specdes collected from within 

Coot Bay-Whi tewater Bay (Stratum V) , open-water areas of Florida 

Bay (Strata, I, 11, 111) and channel areas of Florida Bay (Stratum 

IV) (upper), and among the three open-water strata in Florida 

Bay (lower) for surface trawl samples. 

62 

4 
Stratum V Strata I, 11, 111 

Stratum IV 

Stratum I Stratum II 

Stratum Ill 

OTTER TRAWLS 

Figure 26. Diagrammatic representation of the overall similarities and 

differences in numbers of fish species collected by otter trawl 

within Coot Bay-Whi tewater Bay (Stratum V) , open-water areas of 

Florida Bay (Strata I, 11, 111) and channel areas of Florida Bay 

(Stratum IV) (upper), and among the three open-water strata in 

Florida Bay (lower). I 
pipefish, and silver jenny. Only four of these ubiquitous species were common 

to both gear types. Three demersal species were common to the two open water 

strata (V and 111, 11, I combined), while 17 demersal species were common to the 

channels and open water areas of Florida Bay. No demersal (otter trawl) or 

pelagic (surface trawl) species co-occurred only between the channel stratum and 

the low salinity Coot Bay-Whitewater Bay stratum. By far, there were a greater 

number of unique species collected in the open water areas of Florida Bay than 

were unique to either the channels (Stratum IV) or Whitewater Bay and Coot Bay 

(Stratum V). 

Our analysis of the otter and surface trawl collections (Fig. 25 and 26) for the 

three open water strata of Florida Bay (Strata I, I1 and 111) demonstrated that, 

while many demersal and pelagic species co-occurred in these three strata, 

western Florida Bay (Stratum 111) contained the greatest number of unique 

species, or species collected solely in that stratum. Of the 38 species 

collected by otter trawl used in this analysis, 18 were collected only in 

Stratum 111; of the 24 species collected by surface trawls, seven were present 

only in Stratum 111 (Figs. 25 and 26). There were no species that were found 

both Strata I and I1 but not 111, and only one species occurred in stratum I and 

I11 but not 11. 

Because there was overlap of species among gear types, a third species by strata 

matrix was developed combining total abundances of fishes collected by both gear 

to examine stratum occurrance (Fig. 27). The same criteria (> 10 individuals) 

was used for inclusion of a species into the co-occurrence anglyses. Comparison 

of low (Stratum V) and high salinity (Strata I, 11, 111 combined) open water 

areas and high salinity channels (Stratum IV) revealed few species unique to any 

one habitat class. Of the 49 species included, the tidewater silverside 

(Menidia peninsulae) was collected only in Stratum V, while no species was 

collected only from the channels (Stratum IV). Those species found only in open 

water areas of Florida Bay (Stratum I, 11, 111) included: lined seahorse 

(Hi ocam us erectus), sheepshead 

filefish sef Monacanthus ciliatus) , 

puffer (Sphoeroides nem 

Two species were common only to 

11, 1111, the leatherjacket- (Oligoplites saurus), and gafftopsail catfish, while 

there were no species common only to the channels or the low salinity area of 

Coot Bay and Whitewater Bay. The greatest number of species co-occurred between 

the high salinity open water strata (I, 11, 111) and the channel stratum (48%), 

and included one of the target species, gray snapper (Lutjanus griseus). As was 

pointed out earlier, these areas generally have higher standing crops and 

densities of seagrasses than elsewhere. A second target species, spotted 

seatrout, was among the 16 species that were present i n a l l three areas (Fig. 

27). 

Analysis of pooled data for the open water areas of Florida Bay (Fig. 27, bottom) demonstrated that there were more species unique to Stratum I11 than to 

either Stratum I or I1 or that co-occurred among the three strata. Species 

prevalent to the eastern-most stratum (Stratum I) included: scaled sardine, 

Spanish sardine, great barracuda, and clown goby. One species (hardhead 

silversides) was prevalent only in the central stratum of Florida Bay. Four 

species co-occurred between Stratum I1 and Stratum 111: striped anchovy, gulf 

toadfish, pugnose pipefish (Syngnathus dunckeri) , and sheepshead. A large 

proportion of the species that showed a preference to high salinity open water 
Stratum V 

Stratum I 

Stratum IV 

Strata I, 11, 111 

Stratum II 

Stratum Ill 

COMBINED TRAWL DATA 

Figure 27. Diagrammatic representation of the overall simil ari ties and differences 

in numbers of fish species collected by both surface and otter trawls I within Coot Bay-Whi tewater Bay (Stratum V) , open-water areas of Florida 

Bay (Strata I, 11, 111) and channel areas of Florida Bay (Stratum IV) t (upper), and among the three open-water strata in Florida Bay (lower). 
Table 8. Listing of species and total biomass (grams wet weight) of fish collected 

in Everglades National Park during 1984 and 1985 using a surface trawl. 

Refer to text for strata locations. 

Fami 1 y/Scient i fic Name -- Common Name I I1 I11 IV V TOTAL 

Sphyrnidae - hammerhead 

sharks 

Sphyrna tiburo -- bonnethead - - 

Clupeidae - herrings 

Brevoortia smithi -- yellowfin - 

menhaden 

Harenqula humeralis -- redear sardine - 

Harengula *- -- scaled sardine 58.0 

Jenkinsla lamprotaenia -- dwarf herring 0.2 

Opisthonema oglinum -- Atlantic thread - 

herring 

Sardinella aurita -- Spanish sardine - 

Engraulidae - anchovies 

Anchoa he setus 

--+T 

-- striped anchovy - 7.8 154.6 5.9 59.0 227.3 

Anchoa mltchl i -- bay anchovy - 6.2 48.0 394.4 1192.1 1640.7 

Syndont idae - lizardfishes 

Synodus foetens -- inshore 106.3 - 1.1 0.1 26.6 134.1 

lizardfish 

Ariidae - sea catfishes 

-- Arius felis -- hardhead catfish - - - - 305.3 305.3 

Bagre marinus -- gafftopsail - - - - 48.8 48.8 

catfish 

Batrachoididae - toadf ishes 

Opsanus beta -- gulf toadfish 6.3 30.5 93.0 14.4 0.3 144.5 

Antennariidae - frogfishes 

Histrio histrio -- sargassum fish 5.2 - - - - 5.2 

Exocoet idae - flying fishes 

Chriodorus atherinoides-- hardhead 1351.5 2693.7 209.5 470.6 - 4725.3 

halfbeak 

Hemiramphus - balao -- balao - 1.2 108.8 - - 110.0 

-- ballyhoo 364.9 263.1 1253.0 1648.8 - 3529.8 

H orham hus 

*s 

-- halfbeak 2071.4 508.1 9253.0 3998.2 228.5 16059.2 

Belonidae - needlefishes 

Stronaylura notata -- redfin 936.4 6138.1 863.3 2131.5 3866.3 13935.6 

needlefish 

Strongylura timucu -- timucu - 46.7 1124.8 57.3 708.7 1937.5 
Table 8. (Contd) 

Family/Scientific Name -- Common Name I I I I11 IV V TOTAL 

Cwrinodontidae - killi fishes 

ploridichthys carpio -- goldspotted 3.4 44.2 17.1 6.8 - 71.5 

killifish 

Lucania parva -- rainwater 

killifish 

Atherinidae - silversides 

Atherinomorus stipes -- hardhead 2.0 319.7 5.2 272.3 - 599.2 

silverside 

H oatherina -- reef 137.9 3.3 18.4 244.7 - 404.3 

-ns is silverside 

Mernbras martinica -- rough 184.6 155.3 236.5 53.1 574.1 6203.6 

silverside 

Menidia peninsulae -- tidewater 

silverside 

Syngnathidae - pipef ishes 

Hi ocam us erectus -- lined seahorse - 16.6 - 0.1 - 16.7 '-f%%% msterae -- dwarf seahorse 0.6 1.0 0.3 - 0.1 2.0 

-6nckerl -- pugnose 0.3 0.5 0.4 - - 1.2 

oioef ish 

Synqnathus floridae -- 

Synpnathus louisianae -- 

Syngnathus scovelli -- 

Serranidae - sea basses 

lectrus unicolor -- 

haEcheneidae - remoras 

Echeneis naucrates -- 

Carangidae - jacks 

Caranx hi os -pe 

-- 

Eli es saurus -- 

Trachinotus carolinus --- 

.- . dusky 

pipefish 

chain pipefish 

gulf pipefish 

barred hamlet 

sharksucker 

crevalle jack 

leatherjacket 

Florida 

pompano 

Lut janidae - snappers 

~utjanus ~riseu! -- gray snapper - - 25.8 - - 25.8 

LU anus synagris -- lane snapper 78.0 - 11.9 - - 89.9 

Gerreidae - mojarras 

Eucinostomus araenteus-- spotfin - - - - 5.5 5.5 

mo jarra 

Eucinostomus gula -- silver 160.5 4 66.7 119.0 64.4 193.3 1003.9 

jenny 

areas of Florida Bay (Fig. 27, top) were also among the 22 species that showed a 

decided preference for the near-gulf open water stratum (Stratum 111) (Fig. 27, 

botfom). Of these 22 species, 9 species were common to both channels (Stratum 

Iv) an; the near-gulf stratum (Stratum 111): gray snapper, lane snapper, 

sailor s choice (Haemulon arrai ) , white grunt, bluestriped grunt, pigfish, 

grass porgy (Calamus arctifrons 5 , code goby, and scrawled cowfish. 

Distribution of Fish Within and Between Strata 

The distribution of numbers of individuals and biomass of fishes per unit area 

and numbers of species per station varied within strata as well as between 

strata. Numerical abundance of the demersal community (otter trawl) averaged 

17.3 individuals-100 m-2 and ranged from a low 0.08 individuals-100 m-2 (station 

17-7 in January 1985) to 215.3 individuals~100 m-2 (channel 6 in June 1984). 

The distribution of numbers of fish collected by otter trawls is shown in 

Figures 28, 29, and 30. Overall, Stratum I had the lowest density of fish while 

channel stations had the highest densit . In increasing order the strata are Y ranked: Stratum I (2 = 4.4 indiv-100 m- ; range = 0.1-24.0), Stratum V (X = 

9.1-100 m-2; range = 0.2-161.8), Stratum I1 (E = 13.2*100 m-2; range = 

0.1-102.21, Stratum I11 (x = 26.50100 m-2; range = 0.4-182.1), and Stratum IV (2 

= 33.3.100 m-2; range = 0.8-215.3). For the open water strata of Florida Bay 

(Strata 1-111) there was a trend for the density of fish to increase in a 

northerly direction in all but Stratum I, with maximum fish numbers at stations 

generally between First National Bank and Snake Bight (Fig. 28). 

With the exception of one large catch of bay anchovy near the entrance to the 

Buttonwood Canal in Coot Bay in November 1984, the catches of fish were 

generally low and uniform (i.e., 1-15 indiv.100 m-2) in Stratum V (Fig. 30). 

The overall fish catch and species composit ion, however, differed between Coot 

Bay and Whitewater Bay (Tables 9 and 10). A greater number and biomass of 

fishes were collected in Coot Bay than in Whitewater Bay. The differences were 

due largely to greater catches of bay anchovy in Coot Bay. The demersal 

component of the fish community also was more diverse in Coot Bay than in 

Whitewater Bay, with a total of 30 species collected in Coot Bay and 22 species 

in Whitewater Bay. 

The distribution of numbers of species within and between strata (Figs. 31, 32, 

and 33) followed a trend similar to that observed for total standing stock 

numbers. There was an average of seven species collected at each station 

throughout the study area, and the five strata were ranked as follows: Stratum I 

(4.7), Stratum V (4.8), Stratum I1 (5.7), Stratum I11 (10.1) and Stratum IV 

(11.7). Of the three non-channel strata in Florida Bay, only stations in 

Stratum I11 showed a trend for the number of species collected to increase in a 

northerly direction. This trend of increasing species numbers in a northerly 

direction coincided with an increase in seagrass shoot density and seagrass 

species diversity. Channels also had relatively high densities of mixed 

seagrass species and, with the exception of three (channels 3, 26 and 38), 

channels also harbored relatively large and diverse fish communities. 

The average biomass of fishes (Figs. 34, 35, and 36) varied within strata, and 

the distribution was similar to that of both number of species and individual 

abundances. Wet weight biomass of fish collected by otter trawl ranged from 2 

mg-100 m-2 at station 17-7 (Stratum 11) to 621 g-100 m-2 at station 5-6 (Stratum 

111), and averaged 73 g-100 m-2 for the entire study area. There was a definite 
Table 9. Total abundance of fish taken in bottom trawls from stratum 

V broken into its component Whitewater Bay and Coot Bay areas. 

- - -- 

Species Code Whitewater Bay Coot Bay 

Lady fish 

Atlantic thread herring 

Striped anchovy 

Bay anchovy 

Inshore lizardfish 

Hardhead catfish 

Gafftopsail catfish 

Gulf toadfish 

Redfin needlefish 

T imucu 

Goldspotted killifish 

Rainwater killifish 

Rough silverside 

Tidewater silverside 

Dwarf seahorse 

Dusky pipefish 

Gulf pipefish 

Leather jacket 

Gray snapper 

Spot fin mo jarra 

Silver jenny 

Pigtish 

Sheepshead 

Pinf ish 

Silver perch 

Spotted seatrout 

Southern kingf ish 

Great barracuda 

Florida blenny 

Code goby 

Clown goby 

Lined sole 

Yellowface pikeblenny 

Southern puffer 

TOTAL 
Table 10. Surface trawl data for total catches of each species in 

Stratum V separated into data for Whitewater Bay and 

Coot Bay. 

Species Whitewater Bay Coot Bay 

Yellowfin menhaden 

Scaled sardine 

Atlantic thread herring 

Striped anchovy 

Bay anchovy 

Inshore lizardfish 

Hardhead catfish 

Gaf ftopsail catfish 

Gulf toadfish 

Halfbeak 

Redfin needlefish 

T imucu 

Rainwater killifish 

Rough silverside 

Tidewater silverside 

Drawf seahorse 

Chain pipefish 

Gulf pipefish 

Leather jacket 

Spot fin mo jarra 

Silver jenny 

Silver perch 

Spotted seatrout 

Striped mullet 

Code goby 

Clown goby 

Lined sole 

Total 
Figure 28. Distribution af average number of individuals collected by otter 

trawl in Florida Bay during 1984-1 985. 
-Figure 29. 'Distribution of average number of individual s coll ected by otter 

trawl from channels fn Florida Bay during 1984-1985. 
0 

L 

1000 

meters 

TARPON 

CREEK 

COOT BAY 

Figure 30. Distribution of average number of individuals collected by otter 

trawls at stations in eastern Whi tewater Bay (upper) and Coot 

Bay duri ng 1984-1 985. 
trend for higher biomasses of fish to be at stations in the northern portion of 

Stratum 111, between First National Bank, Johnson Key Basin and Flamingo (Fig. 

34); these areas also generally displayed the most diverse and dense seagrass 

communities. The standing crop biomass of demersal fishes tended to be greater 

in Coot Bay than Whitewater Bay (Fig. 36), and in both areas station values 

generally were greatest near shore. 

Our data on numerical abundance of fishes and their wet weight biomasses fall 

within the range of values reported in the literature, but are on the low end of 

the spectrum. Because of the recognized biases associated with various 

collecting gear (see discussions by Kjelson and Johnson 1978; Weinstein and 

Brooks 1983; Thayer et al., 1987) few comparisons of numbers and biomasses are 

possible. Our estimate of fishes from bottom trawls averaged about 0.2.m-2 

with a range of 8xl0-~ to 2.2 individuals-m-2. Adams (1976), using drop nets, 

observed a standing stock average for two eelgrass beds in North Carolina of 

about 1.8 individ~als*rn-~ with a range of - 0.06-6.0*m-~ . Using otter trawls 

in the Chesapeake Bay, Weinstein and Brooks (1983) observed juvenile fish 

abundances regularly of less than a single individual per m2. Sogard (1982) 

observed densities of 0.2-2.0 fishem-* using a push net in Biscayne Bay seagrass 

beds, but, using a throw trap, Sogard et al. (In press) reported mean densities 

of 11 fi~h-m-~ on several carbonate mud banks in Florida Bay. These authors 

also have computed values of 0.3-1.5.m-2 in Apalachee Bay and <0.6-m-~ in Indian 

River based on available literature. The average wet weight standing crop of 

fish we collected by otter trawl was 0.73 g-m-2 with a range of 2x10'4 to 6.2 

g*m-2. Standing crop biomass of fish reported from other seagrass beds include: 

6.0 g wet weight in Laguna Madre (Hellier 1962); 0.4-2.5 g wet weight em-2 in 

a Thalassia bed in Texas (Hoese and Jones 1963); 0.2-2.0 g wet weight-m-2 in an 

eelgrass bed in Rhode' Island (Nixon and Oviatt 1972); and 7.5 g wet ~eight-m-~ 

in two eelgrass beds near Beaufort, N.C. (Adams 1976). Thus, the average 

numerical abundance and standing crop biomass values we observed are similar to 

but at the low end of the range of several published reports on fishes in 

seagrass meadows. Individual stations in the study area provided values that 

equaled or exceeded (e.g., Figs. 28 and 34), many published abundance and 

biomass values. For the most part, the stations falling into this category were 

located in Stratum I11 and Stratum IV, and have generally dense stands of mixed 

-- seagrass. 

Similarity Among Stations 

With respect to the juvenile fish community, the degree of similarity among 

st at ions occupied during the study was examined using numerical classification 

(cluster analysis). Initially, the number of species included in the analysis 

was reduced from 93 to 44 by requiring that each species be present at least 10% 

of the stations during any one of the surveys. Species-specific numerical 

abundance data then were transformed by applying the loge(R + 1) function. 

Following construction of a station by station (249x249) Bray-Curtis 

dissimlarit y matrix, a group-average clustering algorithm (Bloom et a1 . 1977) 

_was used to aggregate stations. Although numerous associations emerged, 2 

geographically distinct station clusters were obvious at a level of similarity 

of 0.45 (Figs. 37,38). 

Cluster 1 was associated with vegetated areas primarily in Stratum I11 and 

selected channels in Stratum IV (Fig. 37). Approximately 39% of the stations 

sampled in Stratum I11 and Stratum IV were clustered in this group (Table 11). 
NO. SPECIESISTATION 

Figure 31. Distribution of average species numbers collected by otter trawl 

in Florida Bay during 1984-1985. 
. .:, 

CHANNELS 

NO-SPECIESISTATION 

Figure 32. Distribution of average species numbers collected by otter trawl 

from channels in Florida Bay during 1984-1985. 
0 - 1000 

meters 

1400 . 145 . 

,TARPON 

CREEK 

COOT DAV 

~UTTONWO~~ CANAL 

Figure 33. Distribution of average number of species collected by otter 

trawl at eastern Whitewater Bay (upper) and Coot Bay sampling 

stations duri ng 1984-1 985. 
MEAN BIOMASS 1 100m2 

Figure 34. Mean wet weight biomass of fish collected by otter trawl in Florida 

Bay duri ng 1 984-1 985. 
Figure 35. Mean wet wef ght biomass of fish collected by otter trawl in 

Florida Bay channel s during 1984-1 985. 
MEAN BIOMASS1 100m2 

.>0-10 

100. . . 

CREEK 

COOT BAY 

BUTTONWOOD 

CANAL 

Figure 36. Mean wet weight biomass of fish collected by otter trawl in 

eastern Whitewater Bay (upper) and Coot Bay (lower) during 

1984-1 985. 
This cluster was characterized by species that occurred frequently and in large 

numbers compared to the rest of the sampling area. Rainwater killifish, 

pinfish, silver jenny, goldspotted killifish, pigfish and dusky pipefish were 

most abundant in this cluster (Table 12). Two of the target species, spotted 

seatrout and gray snapper, were more prevalent at stations in this cluster than 

elsewhere. 

The plant communities associated with this cluster tended to contain a mixture 

of seagrass species, with standing crops in excess of 250 g-m-2 and shoot 

densities' in excess of 2000*m-~- (Figs. 18-21). With the exception of Man of War 

Channel, which had pure Syringodium in the area we sampled (Fig. 19), the 

channel stations contained either Thalassia and Halodule or mixtures of 

Thalassia, Halodule and ~yringodium9). Generally, the non-channel 

stations in this cluster contained all three seagrass species or mixtures of 

Thalassia and Syringodium and only occasionally mixtures of Thalassia and 

Halodule. The majority of the non-channel areas in this cluster also were 

adjacent to a carbonate mud bank. Thus. based on the densitv of fish. it would 

appear that areas with mixed seagrass species, including ~~rinqodium,'and areas 

adjacent to banks and channels containing Thalassia and Halodule potentially 

offer greater juvenile nursery habitat than do other areas. 

Cluster 2 was located primarily in Stratum I and Stratum V with only a few 

stations in Stratum I1 (Fig. 38a,b and Table 11). Fish species that were 

present in this cluster (Table 12) were characterized by comparatively low 

abundances and relatively low frequencies of occurrence relative to Cluster 1. 

Silver jenny, rainwater killifish, pinfish and spot fin mo jarra were present. 

The seagrasses associated with Cluster 2 tended to be monotypic. The seagrass 

community at these stations was almost pure Thalassia for the non-channel areas 

of Strata I and I1 with standing crops less than 250 g-m-2 and shoot densities 

generally of 5 2000*m-2; in Stratum I seagrass shoot densities generally were < 

1000-m-~. Two channel stations also were associated with this low fish densitycluster; channel 13 south of Joe Kemp Key was pure Halodule while channel 27 at 

Bob Allen Key was primarily Thalassia with a small amount of Halodule. The 

majority of Cluster 2 stations were located in basins and onl-were 

adjacent to carbonate banks. In Stratum V, the stations within this cluster 

generally were characterized by intermediate to low standing crops of pure 

Ruppia (Coot Bay) or Halodule (Whitewater Bay) or a total lack of vegetation. 

Thus, it appears that stations within our sampling area with relatively sparce 

monotypic stands of seagrass provide a lower nursery value to juvenile fish in 

general and to the target species in particular than do mixed seagrass habitats 

near carbonate banks and in channel areas. 

The diversity of plant species and their density as well as the location of 

habitats may be influential in regulating fish abundance and the complement of 

species utilizing habitats in the bay systems we sampled. This complexity may 

be a function of total plant biomass or surface area (Heck and Orth 1980, Stoner 

1980); whether the meadow is generally in a high current or low current area 

(Thayer et al. 1984, Fonseca and Fisher 1986); or seagrass species composition 

(Stoner 1982, 1983, Virnstein and Howard In press). Virnstein and Howard (In 

press) have shown that food resource density (epifauna and gastropods) were 

greater on Halodule while crustacean resource density was greatest on Thalassia 

on a per mL basis. However, when data were evaluated in terms of plant surface 

area, crustaceans were most abundant on Syringodium. Stoner (1982) noted that 
Table 11. Stations grouped into two prominent clusters derived from BrayCurtis dissimilarity index analyses (see Text). See Figure 37 

and 38 for location of stations. 

Cluster 1 Cluster 2 

Stratum I11 Stratum IV Stratum I Stratum I1 Stratum V 

5-5 6 14-17 12-8 1007 

6-2 7 14-18 12-10 1008 

6 -3 8 15-17 12-12 1020 

6 -4 9 16-18 13-9 1039 

6 -6 14 17-12 13-13 1044 

6-7 21 17-16 13-17 2001 

7-3 22 18-13 14-15 2009 

9-1 23 18-16 15-9 2018 

9-2 31 19-16 15-13 20 54 

9-4 34 20-12 16-10 2055 

10-2 40 20-13 20-7 2095 

10-3 44 20-14 2107 

10-4 20-19 2131 

12-3 21-83 21 39 

13-1 21 -1 2 2142 

19-4 21-16 2148 

22-12 2149 

22-16 2155 

22-17 2157 

21 59 
Table 12. Abundance (no. per 100 m2) and number of occurrences for fishes grouped 

in the Strata 111-IV and Strata I-11-V clusters. Only those species 

that occurred in at least 10 cases in one of the clusters are included. 

Species 

Strata 111-IV 

Abundance Occurrence 

Strata I-11-V 

Abundance Occurrence 

Sheepshead 0.i5 

Silver perch , 0.63 

Spotted seatrout 0.10 

Spot fin mojarra 0.47 

Silver jenny . 13.51 

Goldspotted killifish 2.10 

Code goby 0.20 

White grunt 0.94 

Dwarf seahorse 0.55 

Pin fish 15.36 

Rainwater killifish 25.10 

Gray snapper 0.20 

Gulf toadfish 0.36 

Pigfish 1.15 

Southern puffer 0.05 

Pugnose pipefish 0.13 

Ousky pipefish 1.15 

Gulf pipefish 0.72 

Inshore lizardfish 0.07 
Open Water 

A Channels 

Figure 37. Distribution of stations associated with Cluster 1 developed from 

Bray-Curtis dissimilari ty index analysis (see text for discussfon). 
Open Water 

AChamels 

Figure 38a. Distribution of stations in Florida Bay associated with Cluster 2 

developed from Bray-Curti s di ssimi 1 ari ty i ndex analysis (see text 

for discussion). 
Cluster 2 

145 . 

-TARPON 

CREEK 

COOT BAV 

BUTTONWOOD 

Figure 38b. Distribution of stations in Stratum V associated with Cluster 2 

(see text for discussion). 
fish foraging efficiency for crustaceans was lower in Syrinqodium meadows than 

in Halodule meadows. Stoner (cited in Virnstein and Howard In press) also has 

notnpinfish (L. rhomboides) tend to be more prevalant in Halodule beds 

than' in either ~yrinzodium or Thalassia. Such relations probably also exist for 

other fish. Thus, food resources and foraging efficiency and possibly fish 

species apparently are affected by seagrass species composition and probably by 

such factors as plant blade width, height and density. These studies pertain to 

almost pure seagrass meadows, and little information is available on mixed 

species communities and the influence of different mixtures of seagrasses on 

faunal abundance and distribution. Both channel and non-channel areas adjacent 

to banks present relief which adds to the complexity of the habitat and may be 

important in resource and refuge availability potential. Additionally, the 

stations in the,northwestern portion of Florida Bay at which there were 

comparatively high densities and diversities of fishes also are in the vicinity 

of the major water exchange between East Cape and First National Bank. This 

appears to be a major entrance area into the western bay for larval fishes 

spawned in the Gulf of Mexico (see Powell et al. 1987). The presence of 

extensive banks in the vicinity probably reduces the scouring effects of tidal 

currents providing a relatively quiescent environment in which larvae can settle 

out of the plankton. The varied seagrass association in this area would provide 

a wide diversity for refuge and sources of food. 

Distribution of Target Species Among Strata 

Gray snapper (Lutjanus griseus) and spotted seatrout (Cynoscion nebulosus ) were 

the most abundant of the target species collected. Snook were collected only 

during the mangrove phase of our study (see the next section of this report). 

Only three red drum juveniles were collected; all were taken by seine at the 

boat ramp on the Coot Bay side of the Buttonwood Canal plug in March 1985 (< 80 

mm) and May 1985 (110-130 mm) . Trout and gray snapper, however, were collected 

regularly, but in small numbers, during the stratified sampling phase of our 

study as well as at Joe Kmp Key and Bradley Key (see later). Data presented 

here pertain only to the stratified phase of our study. We will use 

environmental parameters associated with these target species to develop 

discriminant functions that describe parameters most characteristic of preferred 

juvenile trout and snapper habitat. These functions will be used to evaluate 

whether the area around Joe Kemp Key and Bradley Key are "good juvenile gray 

snapper and spotted seatrout habitat". 

Previous sampling in the Park (Starck and Schroeder 1970) has suggested that 

gray snapper probably have a spawning peak in June-July based on the presence of 

small juveniles in July and August. Sampling for larvae during 1984-1985 

indicated that snapper larve were present in mid-summer (Powell et al. 1987), 

which tends to support Starck and Schroeder (1970). Whether these larvae are 

gray snapper is subject to question since there are related species potentially 

in the vicinity that have not been adequately described (see Powell et al. 

1987). We collected juvenile gray snapper on every sampling trip, with the 

largest numbers in September 1984 (18), March (15), and May 1985 (23); in total 

we collected 101 juvenile gray snapper weighing 4.1 kg (an additional 52 

individuals weighing 2.6 kg were taken from Joe Kemp Key and Bradley Key). 

Smallest specimens were collected in January (7 g) and June (18-30 g) while 

larger specimens were collected in July (41 g) through November (88 g). These 

data also suggest that spawning may occur in late spring and extend into the 

fall. 
Juvenile gray snapper were collected almost exclusively in two of the four 

strata in Florida Bay. Only two gray snapper were collected in the low salinity 

stratum (V) and both were in Coot Bay. Channel habitats appeared to be used 

most frequently by this species; onry 35% of these target fish were taken from 

non-channel environments. 4lthough collected in western Florida Bay, gray 

snapper were most abundant i~ channels in southeastern Florida Bay, principally 

between Twin Key Bank and the Russell Key and Cross Bank area (Fig. 39). The 

habitats where this species was mast frequently collected tended to have total 

seagrass densities of 1000-4000 shoots-m-2 (68% of the 41 occasions and 83% of 

the gray snapper). Channel stations iq southeastern Florida Bay generally 

contained mixtures of Thalassia and Halodule while non-channel stations in 

western Florida Bay tended to contain mixtures of Thalassia and Syrinqodium or 

Syrinqodium and Halodule. 

It is possible that channels iq southeastern Florida Bay represented the only 

suitable habitat (other than mangrove prop root habitats; see part 11) for 

juvenile gray snapper in this area of our study. The southeastern part of the 

bay is dominated by generally shallow sediments that are low in organic matter 

and on which has developed relatively sparce monotypic Thalassia communities. 

The relief and varied seagrass habitat present in channels in southeastern 

Florida Bay apparently is preferred (along with the mangrove habitat) by 

juvenile gray snapper that are spawned offshore on reefs such as Alligator Reef 

(Starck and Schroeder 1970). The relief and varied seagrass habitat of these 

channels may provide protection and abundant food resources for juvenile gray 

snapper when they are not utilizing the mangrove prop root habitat. 

Juvenile spotted seatrout were collected in all sampling strata, but never in 

large numbers. 4 total of 52 seatrout weighing 1.1 kg wet weight were 

collected; only two were collected in Strata I and 11. This species was present 

primarily in Stratum I11 (Table 5), and specifically in the northwest portion of 

this area (Fig. 39). This is the same geqeral area that the larval phase of the 

Beaufort Laboratory study found to be a major area of larval seatrout abundance 

(Powell et al. 1987). (An additional 72 seatrout weighing 0.6 kg wet weight 

were collected in 15 2-min bottom trawls at. Joe Kemp Key and Bradley Key during 

the year; see later). 

We found juvenile seatrout present i~ every month sampled but May 1984 and 

January 1985. Smallest juveniles (0.4-1.4 go individual-l) were observed in 

Whitewater Bay in June. The smallest juveniles in Florida Ba were present 

between June (0.8 g*individual-l) and July (7.9 g*individual-y), and these were 

taken in seagrass meadows. These data suggest that trout probably spawn 

primarily in early summer and settle out of the plankton into seagrass meadows. 

Individuals collected in channel qabitats always were larger than those 

collected in basin seagrass meadows; this observation may suggest that net 

avoidance differs in these habitat types or that small individuals tend to 

prefer seagrass meadows to channels. Powell et al. (1987) observed the greatest 

frequency of spotted seatrout larvae in passes leading into western Florida Bay. 

Based on these data and our juvenile collections, we hypothesize that larvae 

settle out of the plankton into mixed seagrass beds in the vicinity of their 

point of entrance iqto the Park. 1~ 

Juvenile spotted seatrout, although prevalent primarily in the western part of 

Florida Bay adjacent to the Gulf of Mexico, apparently utilize a wide variety of 

seagrass community types. Juvenile trout were m-ost frequently collected and 

6 
0 Trout 

O Snapper 

0 Both 

Figure 39. Distribution of collections of gray snapper and spotted seatrout 

in Florida Bay. Darkened areas represent channel stations. 
present in higher numbers (- 60% of those collected) in seagrass meadows with 

1000-4000 shoots*m-2. More individuals (19) were collected from mixed 

Thalassia, Syringodium and Halodule meadows having lush growths of Syringodium 

than were collected from any single monotypic seagrass habitat type. 

Discriminant function analysis was carried out in an attempt to identify those 

environmental characteristics most important in determining gray snapper and 

spotted seatrout habitat in Florida Bay. For each analysis, all Florida Bay 

stations (202) were divided empirically into two groups: those at which target 

species were captured and those at which target species were not captured. A 

multivariate analysis of variance (M~NOVA) then was conducted using 

environmental parameters (temperature, salinity, percent organic matter in the 

sediments, sediment thickness, depth of the water column, and logarithms of 

Thalassia abundance and biomass, Halodule abundance and biomass, and Syringodium 

abundance and biomass) to verify that the two station groups had, in fact, 

divergent environmental characteristics. These analyses included data from all 

surveys. Therefore, any seasonal patterns in environmental characteristics 

would constitute added sources of variation. Upon finding a significant MANOVA, 

discriminant functions were derived in a stepwise fashion (BMDP 1983) to 

identify those parameters most important in differentiating the station groups. 

Finally, the efficacy ,of using the measured environmental parameters to disclose 

the presence or absence of target species at a particular station was evaluated 

with a relatively unbiased "jackknife" classification technique (Snapinn and 

Knoke 1984). 

In the first analysis, stations at which seatrout were caught had significantly 

higher organic matter content, thickness of sediment, and numbers and biomass of 

Syringodium (ANOVA, ~~0.05) (Table 13). The overall WNOVA test was 

significant, and a discriminant function was derived. Temperature, organic 

matter, sediment thickness, and Syringodium density were included in the 

function, with high densities of Syringodium and high percentages of organic 

matter being particularly diagnostic of spotted seatrout habitat (Table 13B). 

(Relative importance of discriminating variables was judged by the magnitude of 

the absolute value of discriminant function coefficients and the strength of 

correlation between each variable and the derived function). Subsequent 

evaluation of the linear discriminate functions (2) revealed a relatively 

accurate separation of spotted seatrout habitat based on these variables. Of 23 

stations where we actually collected seatrout, 61% were correctly identified as 

88 seatrout habitat" on the basis of these combined environmental conditions; of 

179 non-seatrout stations, 82% were so classified. With the classification 

gnalysis employed (BMDP 1983) a total of 47 stations were classified as 

seatrout habitat" (regardless of whether we collected seatrout there or not). 

The majority of these potential or actual seatrout habitat occurred in western 

Florida Bay (Stratum 111) and in channels (Stratum Iv) generally located in the 

western and southern portions of Florida Bay (Fig. 40). Larval entrance into 

the Park, at least into Florida Bay, appears to be at passes between Ninemile 

Bank and East Cape (Powell et al. 1987). No stations along the extreme 

northwestern shoreline of Stratum I11 were classified as "seatrout habitat". 

This was an area that we found basically void of benthic vegetation. 

The second analysis, using the same approach employed for seatrout, defined 1~ 

station groups by the presence or absence of gray snagper. Significant 

environmental differences again were found, and gray snapper habitat" was 

characterized by higher densities of shoots and biomass of Halodule and 
a 

> I m 

0 rn 4 

ZQ,U -13 I 

scnsg.zg u -4Ccc 

*- al (Uo m 

@UOO>U 

occ C alom3Cnm 

0 auk C 

cmc -40 

3UOY ou13 c m 0 -4 Y m mc4 L, 

-I 60730- E m.4m -4ma 

Ccu E ace Q) O 

al m CcCb Li.4 

>u Oc, Q) Oce 

omcc 0fJ.d 

(Us4 > 0C 0 a, >'13al(UCOCk 

Q, dnc~ 

0 v,.rlcc* E 

Q) om.4u OmCmCcc 

cwmmomm OUlUk(nCC 

0 3 -4 0.4 -4 0 

z ",2, gu.zs *4Q)ccnuCc m c40 woo 

t3)m.4Q- N cn v, *4 m m 0 -4 -4 

cn -4 UDo 

k mk 3 

-m *cnnJ(UO m >o mu[3 Ll C 3ECU,c, mk00m m 

?!fE$Z%$$ 

TI a0 

N C -4 w 

-0 -4 

U 

m -4 

uce c'c 

(0 Q, u 0 

tn u 
Syringodium (ANOVA, p<0.05). Following significant WNOVA, a discriminant 

function utilizing salinity, sediment thickness, numbers and biomass of 

Thalassia, and biomasses of Halodule and Syringodium was developed (Table 14). 

Halodule and Syringodium biomasses were the most informative variables (Table 

.-tations were correctly assigned to groups in 68% of cases (40) where 

gray snapper were collected and 79% of cases (162) without gray snapper. Of 61 

stations classified as "snapper habitat1' (whether or not snapper were caught 

there), 29 (48%) occurred in western Florida Bay (Stratum 3) and 27 (44%) 

occurred in channels (Stratum IV) (Fig. 41). Channels appeared to be good 

habitat for gray snapper virtually everywhere in the Bay, particularly where 

seagrass communities included substantial stands of Halodule and/or Syringodium. 

Gray snapper habitat appeared to be focused primarily in grass beds and channels 

located between Ninemile Bank and East Cape and in channels in the near vicinity 

of the Florida Keys. As was the case for spotted seatrout, these data suggest 1 

to us that early stage juvenile gray snapper generally settle out of the I 

plankton after entrance into Florida Bay, and only move into interior areas of 

the Bay after an unknown period of growth. As noted earlier, smaller snapper 

appeared more frequently in grass meadows while larger juveniles were more ) 

characteristic of channels. 

For the final analysis, we pooled stations at which either gray snapper or 

spotted seat rout occurred and compared them to stat ions where neither target 

species was caught. The stat ion groups differed significantly (WNOVA, p<0.05), 

stations with target species having more organic matter in the sediments, 

greater sediment thickness, and greater abundances and biomasses of Halodule and 

Syringodium ( ANOVA, ~~0.05). Discriminant analysis identified temperature, 

salinity , water depth, abundance and biomass of Thalassia, and biomasses of 

Halodule and Syringodium as important discriminating variables (Table 15A). 

Halodule and Syringodium biomasses were most influential (Table 158). 

Classification analysis successfully grouped 72% of 54 snapper-seatrout stations 

and 83% of 118 non-target stations. This analysis of pooled snapper-seatrout 

habitat yielded results similar to those of the two single-species analyses. 

That is, best habitats for juvenile target fish appear to lie in open waters of 

western and northwestern Florida Bay (most of Stratum 111) and in channels 

(Stratum IV), especially those to the west and south (Fig. 42). 

Seasonality of Environmental Parameters and Fishes at Joe Kemp Key and Bradley Key 

T NO stat ions were regularly sampled independent of the stratified random design 

to provide insight into the seasonality of fishes and seagrasses. Joe Kemp Key 

+l (JKK), located east of the flamingo Channel near day marker '@12'', was sampled 

nine times from May 1984 - June 1985. Bradley Key Station (BK), located about 

200 meters SW of Bradley Key, was sampled six times from September 1984 - June 

1985. The sampling procedure was exactly the same at these two stations as it 

was for all other stations; surface trawl data have not been included in the 

analyses. 

The areas sampled near Joe Kemp Key (station 1) and Bradley Key (Fig. 8) are 

shallow, carbonate mud areas adjacent to islands and had a thick sediment layer 

with relatively high silt-clay (73%) and organic matter (15-16 %) contents in 

the surface sediments. The sediments for these two general sites are 

characteristic of those in much of the northwest portion of Florida Bay (Figs. 
Table 14. Means, significance levels for univariate ANOVA, and overall significance of WNOVA for 

variables used to distinguish stat ions with from stations without gray snapper. Significance 

levels are for loglo (x+l) transformations of abundance and biomass of seagrass species; 

8. variables comprising the discriminant function, standardized discriminant coefficients, 

correlation coefficients relating variables to the discriminant function, and mean discriminant scores for snapper and non-snapper stations. * refers being considered significant. 

Snapper 

A. Variable (n = 40) 

Temperature (*C) 27.1 

Salinity (ppt ) 35.5 

Organic matter (%) 14.1 

Sediment thickness (m) 0.9 

Water deoth (m) 1.6 

~halassia (shoots/m2) 722 

(gdwt/m24) 195.2 

Halodule shoot 

tgdwt~~~ 

914 

19.5 

~yr ingodium (shoots/m2) 713 

( gdwt/m2 > 56.0 

0. Discriminant 

Fwlct ion 

No. snapper 

(n = 162) Significance 

MANOVA ilk's Lamda = 0.77 

Equivalent F = 9.82 

Standardized Correlation 

Coefficient Coefficient 

Salinity -0.24 

Sediment thickness -0.40 

Thalassia abundance -1.22 

Thalassia biomass 1.36 

Halodule biomass 0.52 

Syringodium biomass 0.58 

Mean scorer snapper stations = + 1.10 

non-snapper stations = -0.217 
Table 15. Means, significance levels for univariate ANOVA, and overall significance of MANOVA for 

variables used to distinguish stat ion with from stat ions to without target species (spotted 

seatrout and/or gray snapper). Significance levels are for loglo (x+l) transformations 

of abundance and biomass of seagrass species; 6. variables comprising the discriminant 

function, standardized discriminant coefficients, and correlation coefficients relating 

variables to the discriminant function. * refers to variables considered significant. 

Target No. Snapper 

A. Variable (n = 54) (n = 148) Significance 

Temperature ( 'C) 27.2 26.6 

Salinity (ppt ) 35.6 36.2 

Organic matter (%) 14.4 12.2 

Sediment thickness (m) 1.0 0.9 

Water depth (m) - 1.6 1.5 

Thalassia (shoots/m2) 736 

(gdwt/m24) 209.2 

Halodule shoots 751 

tadwt/m47 16.6 

El. Discriminant 

Function 

Temperature 

Salinity 

De~th 

T hHlassia abundance 

Thalassia biomass 

Halodule biomass 

Syringodium biomass 

MANOVA ilk's Lamda = 0.70 

Equivalent F - = 11.61 

Standardized Correlation 

Coefficient Coefficient 
0 Open Water 

Figure 40. Results of discriminant analysis depicting seatrout habitat. 
SNAPPER HABITAT 

Figure 41. Results of discriminant analysis depicting gray snapper habitat. 
11, 14, and. 16). We did not sample the exact area each time, and this is 

exemplified by the highly variable sediment parameters. There was no seasonal 

pattern in sediment characteristics evident at either locat ion. Sediment depth 

averaged 1.3 m at Joe Kemp Key (JKK) and ranged from 1.0 - 1.6 m, while at 

Bradley Key it averaged 1.4 m and ranged from 1.1 - 1.9 m. Mean water depth was 

1.1 m. 

The seagrass communities at both Joe Kemp Key (station 1) and Bradlev Kev were 

dominated by S rin odium filiforme and ~halassia testudinum, although ~aiodule 

wriqhtii was % co ecte at both sites. Total seagn density was similar 

at both sites, averagi~g approximately 1400 shoots* m-2, values intermediate to - - 

those observed throughout the Bay. seagrass standing crop at Joe Kemp Key, 

however, was almost three times that collected at Bradley Key; standing crop 

biomass averaged 247 and 81 gw2, respectively. Thalassia was much more 

abundant at,Joe Kemp Key than at Bradley Key, and tended to display an increase 

in shoot numbers during summer with maximum values in November (Table 16). 

Plant standing crop, however, decreased at the same time, between July and 

November. Highest standing stocks of Thalassia at Bradley occurred in spring. 

Syringodium contributed more to the average shoot density at both sites than 

did Thalassia, and tended to have its maximum density in autumn and winter. At 

Joe Kemp Key we collected Halodule only in January 1985 (1067 shoots-m-2; 13, 

1 while this species was collected at Bradley Key in both May 1100 

shoots*m-2 ind 22 and June 1985 (3100 shoots*m-2 and 67 gem- ). 

The temperature and salinity patterns at the two stations showed some seasonal 

variation (Fig. 43). Both stations exhibited decreases in temperature in June, 

which was unexpected, ,and significant decreases, as expected, in January and 

March. Both stations had similar annual average temperatures (26.7*, 26.9.C) 

and salinities (33, 39/00). Salinities dropped in September as a result of 

heavy rains. The decrease in salinity at JKX in March is unexplained. 

Both Joe Kemp Key and Bradley Key exceeded the average of other stations 

throughout the study area in numerical abundance of individual fish per unit of 

area, fish wet weight per area, and number of fish species collected (Table 17). 

The average number of fish collected by otter trawl from the stratified random 

sampling was 17.3 fish.100 m-2, with a maximum of 215.3, compared to an average 

of 124.6 for JKK. The average number of species throughout the stratified study 

was seven, compared to 19 for JKK. The average wet weight biomass was 73 g from 

the other strata compared to an average of 579 g-100 m-2. The maximum biomass 

of 1170 g.100 m-2 in May 1985 from JKK far exceeded the maximum of 621 g.100 m-2 

we collected at any station (station 5-6) during the stratified survey. These 

data suggest that bank habitats may be among the most diverse habitats in terms 

of fish, at least relative to the basin and channel habitats we sampled. Powell 

et al. (1986), sampling on the banks, also observed fish abundances exceeding 

those we generally observed in the basin-channel areas of the Bay. 

Joe Kemp Key had about twice the number of fish for each 100 m2 (124.6 vs. 64.6) 

and about 60% more biomass for each 100 m2 (579.0 vs. 362.7) than at Bradley 

Key. JKK also averaged about two more species in each sample than did Bradley 

Key (19 vs. 17). These species numbers are higher than those for most of the 

stratified sampling phase of our study. 

Seasonal trends in both fish numbers and biomass were evident at both Joe Kemp 

Key and Bradley Key (Table 17 and Fig. 44). Overall, total fish numbers and 
11, 14, and. 16). We did not sample the exact area each time, and this is 

exemplified by the highly variable sediment parameters. There was no seasonal 

pattern in sediment characteristics evident at either location. Sediment depth 

averaged 1.3 m at Joe Kemp Key (JKK) and ranged from 1.0 - 1.6 m, while at 

.Bradley Key it averaged 1.4 m and ranged from 1.1 - 1.9 m. Mean water depth was 

1.1 m. 

The seagrass communities at both Joe Kemp Key (station 1) and Bradley Key were 

dominated by S rin odium filif orme and ~halassia testudinum, although ~aiodule 

wriqhtii was 3?-- co lected at both sites. Total seagrass shoot density was similar 

at both sites, averagi~g approximately 1400 shoots- TI-2, values iitermediate to 

those observed throughout the Bay. Seagrass standing crop at Joe Kemp Key, 

however, was almost three times that collected at Bradley Key; standing crop 

biomass averaged 247 and 81 respectively. Thalassia was much more 

abundant at 'Joe Kemp Key than at Bradley Key, and tended to display an increase 

in shoot numbers during summer with maximum values in November (Table 16). 

Plant standing crop, however, decreased at the same time, between July and 

November. Highest standing stocks of Thalassia at Bradley occurred in spring. 

Syringodium contributed more to the average shoot density at both sites than 

did Thalassia, and tended to have its maximum density in autumn and winter. At 

Joe Kemp Key we collected Halodule only in January 1985 (1067 shoots-ms2; 13 

while this species was collected at Bradley Key in both May 1100 

shoots-m-2 and 22 and June 1985 (3100 shoots-m-2 and 67 g-TI- 1 1. 

The temperature and salinity patterns at the two stations showed some seasonal 

variation (Fig. 43). Both stations exhibited decreases in temperature in June, 

which was unexpected, and significant decreases, as expected, in January and 

March. Both stations had similar annual average temperatures (26.70, 26.9-C) 

and salinities (33, 350/00). Salinities dropped in September as a result of 

heavy rains. The decrease in salinity at JKK in March is unexplained. 

Both Joe Kemp Key and Bradley Key exceeded the average of other stations 

throughout the study area in numerical abundance of individual fish per unit of 

area, fish wet weight per area, and number of fish species collected (Table 17). 

The average number of fish collected by otter trawl from the stratified random 

sampling was 17.3 fish.100 m-2, with a maximum of 215.3, compared to an average 

of 124.6 for JKK. The average number of species throughout the stratified study 

was seven, compared to 19 for JKK. The average wet weight biomass was 73 g from 

the other strata compared to an average of 579 g-100 m-2. The maximum biomass 

of 1170 g.100 m-2 in May 1985 from JKK far exceeded the maximum of 621 g.100 m-2 

we collected at any station (station 5-6) during the stratified survey. These 

data suggest that bank habitats may be among the most diverse habitats in terms 

of fish, at least relative to the basin and channel habitats we sampled. Powell 

et al. (19861, sampling on the banks, also observed fish abundances exceeding 

those we generally observed in the basin-channel areas of the Bay. 

Joe Kemp Key had about twice the number of fish for each 100 m2 (124.6 vs. 64.6) 

and about 60% more biomass for each 100 m2 (579.0 vs. 362.7) than at Bradley 

Key. JKK also averaged about two more species in each sample than did Bradley 

Key (19 vs. 17). These species numbers are higher than those for most of the 

stratified sampling phase of our study. 

Seasonal trends in both fish numbers and biomass were evident at both Joe Kemp 

Key and Bradley Key (Table 17 and Fig. 44). Overall, total fish numbers and 
Table 17. Catcn data from the two permanent stations - Joe Kemp Key *l (JKK) and Bradley Key 

(BK) i~ 1984, 1985. Margalef index of diversity is (S-l)/ln N, where S = number 

of species and N = number of fish. . - 

No. Wet wt. Fish/ $100 m2 "40. Diversity 

Fish (3) 130 m2 species Index 

JKK May 

Jun 

Ju l 

S~P 

Nov 

Jan 

Mar 

May 

Jur: 

TOT9L 74 54 

AVERAGE 828.2 

S~P 6 16 

No v 134 

Jan 139 

Mar 588 

Ma)/ 793 

Jun 973 

TOTAL 3123 

AVERAGE 520.5 
Figure 42. Results of discriminant analysis of preferred trout-snapper habitat and non-trout-snapper habitat. 
Figure 43. Temperatures and salinities at Joe Kemp Key (JKK) and Bradley Key (BK) during study period. 

102 
biomass were highest from May through September and lowest in November through 

March. Except for the January collection at Bradley Key, the number of species 

was fairly consistent and showed no seasonal trend. 

There was a seasonal trend in biomass of the most abundant species at these two 

stations (Tables 17-20, Figs. 45 and 46). Most species displayed a decline in 

biomass from November through March. Spotted seatrout and silver jenny 

displayed the least seasonal change, whereas pinfish and pigfish showed the 

greatest seasonal differences decreasing from about 300 go100 m-2 in May and 

June to less than 10 g.100 m-5 in November and January. There was a greater 

biomass of silver jenny, sheepshead, and spotted seatrout at Bradley Key in 

March than at JKK whereas in September, silver jenny, sheepshead and gray 

snapper displayed a greater biomass at JKK than at Bradley Key. It was 

difficult to discern an annual pattern to the changes in biomass when May and t 

June of 1984 and 1985 are compared. For example, gray snapper biomass was less 1 

than 25 g.100 m-2 in May-June 1984, but exceeded 125 g-100 m-2 one year later. 

Silver jenny and pinfish were more abundant in the spring of 1985, whereas 

pigfish were less abundant in 1985 than 1984. These temporal variability in 

fish data shown here were characteristic of data for the stratified survey; our 

analyses incorporate these patterns which have been accepted as a source of 

variation. 

Pinfish were the most abundant species (in terms of biomass) at both stations. 

Tables 18 and 19 list the eight most abundant species collected at the two 

stations. Both gray snapper and spotted seatrout were among the most abundant 

species. Tables 20 and 21 list these top eight species, plus about 20 

additional species which provided at least 1 g-100 m-2 wet weight biomass during 

one or more of the sampling trips. When these data are summed, there is no 

apparent overall seasonal pattern. Some species were absent in the winter from 

both stations, which indicates perhaps that they migrate to deeper or offshore 

waters. These are pigfish, gray snapper, gulf toadfish, striped mullet, white 

mullet, southern flounder, and gulf pipefish. 

Gray snapper ranged in biomass from 0 (January) to 134.2 g-100 m-2 (June) with 

an average biomass of 25.4 g-100 m-2 year around. Spotted seatrout ranged from 

3 se arch) to 18.2 (May) and provided an average of 5.4 g.100 m-2. Thus, these 

two grass bed stations appear to provide almost five-fold more snapper than 

trout biomass. More trout biomass was observed at Bradley Key than at Joe Kemp 

Key, while more gray snapper biomass was observed at Joe Kemp Key than Bradley 

Key. These station biomasses as well as numerical abundances for both gray 

snapper and seatrout are larger than were taken from most of the stations 

sampled during our stratified phase of this study. 

Joe Kemp Key and Bradley Key may be inhabited by different sizes of target 

species. Smallest individual seatrout were collected in May through July (0.3 

9-2.9 g) at both JKK and Bradley Key. These data are similar to those observed 

in our stratified survey, where we collected early stage juvenile trout in June. 

Overall, JKK appeared to maintain a seatrout population that was either smaller 

or more recently settled out of the plankton than did Bradley Key. The average I 

size individual at JKK weighed 3.9 g wet weight whereas at Bradley Key it was 

18.4 g wet weight. Snapper, on the other hand, individually were smaller at 

Bradley Key (15.5 g*individual-l) that at Joe Kemp Key (76.4 g-individual). 

Smallest individual snapper generally occurred in autumn at Bradley Key (0.5 g) 

and in winter at JKK (3.9 g); in general, this agrees with our findings in the 
Table 18. Bimss [g wet wt/lOO m2) of species with greatkt frequency oi occurrence at Joe 

Kemp Key #l station. 

May 3un Jul SP Nov Jan Mar May Jun Total 

Pinfish 182.2 

-P igfish 284.1 

Silver perch 77.1 

Silver jenny - 

Gray snapper 22.5 

Sheepshead 13.3 

Inshore lizard- 12.1 

fish 

Spotted sea- 1.6 

trout 
Table 19. Biomass (g wet wt/100 m2) of species with greatest frequency of 

occurrence at Bradley Key Station. 

Pinfish 

Silver perch 

Silver jenny 

Pig f ish 

Spotted seatrout 

Gray snapper 

Sheepshead 

Inshore lizardfish 

Nov Jan Mar May Jun Total 
Table 20. Frequency of occurrence on Joe Kemp Key of fish species exceeding 1 g. 

(wet wt )/lo0 m2. 

May Jun July Sept Nov Jan Mar ~ay Jan Total 

Silver ~erch x x x x x x x x x 9 

Silver jenny 

Pinfish x 

Sheepshead x 

Pigf ish x 

Inshore lizardfish x 

Spotted seatrout x 

Gray snapper x 

Southern puffer x 

Gulf pipefish , x 

Hardhead catfish 

Spot fin mo jarra x 

Fringed filefish 

Gulf toadfish x 

IXlsky pipefish 

aay anchovy 

Striped burrfish 

White grunt 

Rainwater killifish 

Gulf flounder x 

Gafftopsail cat fish 

Grass porgy 

Planehead f ilefish 

Gag 

Southern flounder 

Leopard searobin x 

Red drum 

Blackcheek tongue- x 

fish 

TOTAL 14 13 10 9 7 12 9 11 12 
Figure 44. Total number of fish, biomass, and numbers of species at Joe 

Kemp Key (JKK) and Brad1 ey Key (BK) , 1 


, 

stratified survey, although small individuals at Bradley Key in autumn 

(September) occurred earlier than we observed in the survey. Although the data 

are limited, the differences we observed in size distribution between these two 

sites may be an indication of different patterns of settlement and use by 

seatrout and gray snapper at sites only about a nautical mile apart. 

Classification of habitat was performed on data taken at the Joe Kemp Key #1 and 

Bradley Key sites by using the discriminant function environmental variables 

developed from target-fish vs. non-target-fish stations during the stratified 

survey of Florida Bay (see previous section). We classified the habitat 

conditions recorded during each JKK and BK collection as target or non-target 

species habitat on the basis of environmental conditions alone, without 

considering whether target specimens actually were or were not captured (in 

fact, target specimens occurred on all 15 sample occasions). This provided a 

useful, though imperfect, gauge of 1) whether the function derived for the bay 

as a whole was applicable (i.e., had predictive value) for JKK and BK, and/or 2) 

whether the factors helping to define "good seatrout and snapper habitat8' at JKK 

and BK are generally those factors favoring the presence of target species 

throughout the Bay. 

Using the criteria developed above 7 of 8 JKK sample occasions and all 5 BK 

sampling periods were classified as good target species habitat. The one 

exception at JKK occurred for a sampling period in which very little seagrass 

was found. The distribution of discriminant scores by station provides some 

index of the relative "suitability" of various habitats for target species. At 

Joe Kemp Key, the average discriminant score (for the 7 correctly classified 

stations) was greater than those of 94% of other Florida Bay stations (>68% of 

those stations with target species). At Bradley Key, the average discriminant 

score was greater than those of 81% of other Florida Bay stations (but only >32% 

of those for stations with target species). 

Feeding Habits of Target Fish 

Spotted Sea Trout 

Stomachs from 173 trout, 15 to 315 rnrn in standard length (mean length of 60.4 

mm), were examined. These trout were collected from all phases of the study 

(open water and mangrove). Trout were placed in one of seven standard length 

size classes for data analysis, and segregated by area of capture into four . 

habitat groups: (1) grass bed/open water in Florida Bay; (2) mangrove prop 

root; (3) Whitewater Bay and Coot Bay; (4) channels in Florida Bay (Fig. 47-51). 

Overall, most of the trout captured had recently fed and only 17% had empty 

stomachs (Fig. 47). The single most important food for trout above 30 mm from 

all habitats were penaeids (Penaeus duorarum, pink shrimp). Trout less than 30 

mm ate almost equal numbers ofipods, mysids, copepods, carideans, and fish. 

Fish, primarily rainwater killifish, increased in dietary importance as trout 

reached 50 mm, where they contributed to about one-third of the frequency of 

prey occurrence. Although penaeids were very common in trout captured in open 

water/seagrass habitats (Fig. 48), and present in the diet of a few trout 

collected in channels (Fig. 51), penaeid shrimp were absent in the four fish 

from mangroves(Fig. 49). Spotted seatrout captured in Whitewater Bay and Coot 

Bay, however, fed more on fish than shrimp (Fig. 50). An increasingly larger 

proportion of trout had empty stomachs as their size increased; this may be 
Table 21. Frequency of occurrence on Bradley Key of fish species exceeding 

1 g (wet wt)/100 m2. 

MONTH 

Species Sept Nov Jan Mar MY Jun Total 

Silver jenny x 

Pin f ish x 

Inshore li zardf ish x 

Silver perch x 

Spotted seatrout x 

Sheepshead x 

Pigf ish x 

Lane snapper x 

Hardhead cat fish x 

White grunt x 

Gray snapper 

Gulf toadf ish 

Fringed filefish 

Ousty pipefish 

Bay anchovy x 

Striped burrfish 

Planehead filefish x 

Striped mullet 

White mullet 

Southern flounder x 

Look down 

Southern puffer 

Gulf pipef ish 

Total 13 
CtnU*" 

*r a 

-0 *-E 

U fU'C1.r 

Sf- 0 L 

3 CT) nc 

a- OL, 

Ul-U? SaaE 

aJ S 

L E -r- ll 

LOE 

3 U't L at X 

U w *- 

ow P 

a ul fa C,+'c L 

SUUU 

aaJa 

Uf-E II 

Lv 0 

aJ oC,e n U ulU 
Figure 48. Percent occurrence of food i tems found in the stomach of 131 spotted 

seatrout collected from seagrass and open water habitats of Florida Bay. 

N = number of stomachs examined, Code: A = amphipod; C = caridean shrimp; 

Z = zoea/megalopa. 

SIZE 

CLASS 

mm(SL) 

< 30 

30-50 

50-75 

75-100 

100-150 

150-250 

PERCENT 

EMPTY 

STOMACHS 

8 

19 

12 

17 

50 

43 

N 

36 

42 

24 

12 

10 

7 

1 

PERCENT 

20 40 60 80 I I v I I I I I I 

AMPHIPOD I MYSlD I C I co IFISH~~ 

PENAEID [MYSID~FISH~ c I A 

PENAEID I FISH I C IA 

PENAEID I FISH I C 

PENAEID 

PENAEID I FISH 

100 
SIZE PERCENT 

CLASS N EMPTY PERCENT 

mm(SL) STOMACHS 20 40 ' 60 - 80 100 I I 1 I u I I r 

30-50 1 0 CARIDEAN I FISH 

50-75 2 AMPHIPOD I MY SlD 

75-100 1 0 FISH 

Figure 49. Percent occurrence of food i tems in stomachs of four spotted seatrout 

collected from mangrove prop root habitats in Florida Bay. N = number 

of stomachs exami ned. 
Figure 50. Percent occurrence of food items found in the stomachs of 29 spotted 

seatrout from Whi tewater Bay and Coot Bay. N = number of stomachs examined. 

Code: A = emphipod; CO = copepod; CR = crab; M = mysid shrimp; P = penaeid; 

PERCENT 

EMPTY 

STOMACHS~ 

0 

0 

0 

33 

PERCENT 

I 20 40 60 I 80 I I 100 

N 

9 

7 

7 

6 

@ 

-I 

4 

V1 

I # I I I 

PENAEID I FISH ICOIM 

FISH I PENAEID I z 

FISH I P I A /CR 

FISH I P I A 

SIZE 

CLASS 

mm (SL) 

<30 

30-50 

50-75 

75-100 

i - 
Figure 51. Percent occurrence of food items found in the stomachs of nine spotted 

seatrout collected from channel habitats in Florida Bay. N = number of 

stomachs exami ned. 

SIZE 

CLASS 

mm(SL) 

< 30 

30-50 

100-150 

150-250 

> 250 

I 

N 

2 

4 

1 

1 

1 

PERCENT 

EMPTY 

STOMACHS 

50 

100 

100 

PERCENT 

20 40 60 80 100 

I 1 I 1 I 1 I 1 I 

COPEPOD - 

PENAEID I FISH 

FISH 
related to a decrease in feeding frequency with increasing size. The four 

individuals captured in mangroves had food in their stomachs, suggest that this 

habitat provides food for trout although the small sample size precludes any 

significant conclusion regarding trout feeding in mangroves. 

The food habits of spotted seatrout reported in this study are exactly as would 

be predicted from the literature. Perret et al. (1980) list eleven 

investigations between 1929 and 1975 reporting on spotted seatrout food types 

and food preferences. Moody (1950), working on trout from Cedar Key, Florida, 

found that juvenile trout ate copepods, mysids, penaeids, and carideans. As 

trout increased in size (above 250 mm) fish became the most important component 

of the diet. Rutherford et al. (1982) in the Flamingo area sampled 60 seatrout 

less than 271 mm and found the percent frequency of occurrence of prey to be, in 

decreasing abundance: shrimp (go%), fish (22%), algae (12%) , molluscs (8%), 

crabs (3%) and other (3%). Large trout in their study (> 370 mm) consumed fish 

and shrimp equally in frequency, and consumed almost twice as much fish as 

shrimp when percent volume of stomach contents was compared. In our study, we 

never captured fish above 250 rnm that contained food, and thus did not observe a 

dietary shift to fish. In Florida Bay, Stewart (1961) found that pink shrimp 

was the principal food item of adult trout. In general, several studies cited 

by Perret (1980) found that shrimp were more common in seatrout stomachs during 

?r than during winter ; this corresponds to shrimp seasonal abundance. 

;ray Snapper 

Stomachs from 215 gray snapper, from 26 to 280 mm SL (107.9 mm mean length), 

were examined and analyzed in seven standard length size classes by three 

habitat groups. No snapper were examined from the Whitewater Bay/Coot Bay open 

water/grassbed habitat. 

Snapper fed primarily on penaeid and caridean shrimp until they reached a length 

of 50 mm (Fig. 52). 4 food component of nearly equal importance to penaeid and 

caridean shrimp in the diet of snapper larger than 50 mm. Fish species 

identified in snapper stomachs included rainwater killifish, pipefish, gulf 

toadfish, goldspotted killifish, goby, seahorse, and silver jenny. Amphipods 

constituted approximately 20% of the occurrence observations in fish less then 

50 mm, but on a volume basis amphipods contributed much less than 5% to the diet 

of small snapper. Plant material (Thalassia blades) appeared in stomachs of 

fish larger than 150 mm, perhaps as a result of aggressive feeding attacks on 

prey in grass beds. 

As we found for spotted seatrout, the absence of penaeid shrimp in the diet was 

the major qualitative difference in the gut contents of the snapper taken from 

mangrove prop root habitats rather than from open water in Florida Bay (see part 

XI) (Fig. 53, 54, and 55). The primary food items for fish from the mangrove 

habitats were isopods, amphipods, xanthid crabs, caridean shrimp and demersal 

fish, observations similar to Stark (1971) who carried out a detailed study of 

the food habits and feeding of gray snapper collected from grass meadows, coral 

reefs and areas adjacent to mangroves. He reported that small juveniles 

collected from seagrass areas consumed crustaceans (93%), primarily amphipods 

and caridean shrimp, while larger juveniles collected near mangroves and in 

seagrass beds also consumed crustaceans (69%), primarily pink shrimp (Penaeus 4 duorarum) and xanthid crabs. Rutherford et al. (1983) reported that juvenile 

gray snapper, found mainly in grass-bed areas inshore, ate shrimp, crabs, and 
Figure 52. Percent occurrence of food i tems in the stomachs of 21 5 gray snapper 

from all habitats sampled in Everglades National Park. N = number of 

stomachs examined. Code: A = emphipod; C = caridean shrimp; CR = crab; 

I = isopod; M = mysid shrimp; Z = zoea/megalopa. 

L 

SIZE 

CLASS 

mm(SL) 

< 30 

PERCENT 

20 40 60 80 100 

I f I I I I 

PENAEID I CARIDEAN I z -1 A 

30-50 

50-75 

75-100 

100-150 

150-250 

>250 

N 

6 

J PERCENT 

EMPTY 

STOMACHS 

0 

8 

54 

64 

45 

35 

3 

25 PENAEID I A I I 

35 

34 

40 

31 

100 

amphipods, while adults offshore ate mainly fish and shrimp. Sixty five percent 

of the snappers examined in our study contained food items compared with 42% 

found by Rutherford et al. (1983). Their fish stomachs were collected from 

sport fishermen catches at Flamingo which may have been the cause of the higher 

percentage of fish with empty stomachs. They found that pink shrimp contributed 

to about 77% of the prey by frequency of occurrence for all sizes. Within a 

particular fishing area, they found no significant differences in the diet due 

to season or snapper size. In our study, fish replaced amphipods in the diet as 

snapper size increased, but otherwise, all sizes of snapper had primarily a 

penaeid/caridean shrimp diet. The frequency of occurrence of penaeid shrimp in 

fish we collected from seagrass meadows was 34%, similar to the overall 

frequency reported by Stark (1971), while it was zero for the fish collected 

from the mangroves. We rarely collected penaeid shrimp in the mangrove habitat 

while rotenoning, but they were common in the adjacent habitat trawl samples and 

are reported to be the dominant large invertebrate in the Florida Bay seagrass 

meadow/carbonate mud bank habitat (Tabb and Dubrow 1962). Therefore, either 

snapper in our mangrove samples were not foraging on penaeids in the nearby 

9 r the small sample of 32 fish. lance missed analyzing fish 

t ntly ingested pena 

Stark ~~Y/LJ also reported a hign incidence i~z%) or empcy s~omachs, all" stated 

that juvenile snappers in grass beds fed during the day whilel larger snappers 

fed at night; stomachs of fish collected in late afternoon were generally empty. 

In our study the three snapper over 250 mm SL were collected from the mangrove 

prop root habitat, and they had empty stomachs (Fig. 54). Sixty percent of the 

snapper collected in channels (Fig. 55) had empty stomachs compared to an 

average of 21% that were empty in grass beds and 31% that were empty in 

mangroves (Figs. 53, 54). Although our data set is small, channels apparently 

do not provide as satisfactory a feeding habitat as grass beds or mangroves for 

snapper under 250 mm. Thus, although snapper were collected most frequently in 

channel areas, particularly in eastern Florida Bay (Fig. 39), and mangrove prop 

root areas, this species apparently is not feeding to a large extent in the 

channels, at least during daylight. The mangrove prop root habitat and seagrass - I appear to provide food sources for gray snapper. 

!ding Habits of Other Species 

teadows 

Fee 

igrove 

:imp 

. A 

1s of three snook, 370-390 mm SL, captured in Whitewater Bay in mar 

lot habitats were examined. Two contained one 50-60 mm penaeid sh~ 

dach and the third was empty. Three red drum were captured and analyzed. 

330-n individual from the grass bed west of Joe Kemp Key (station *1) had an 

empty stomach. Two drum, 70 and 82 mm SL, from the boat ramp in Buttonwood 

Canal, contained 20-mm rainwater killifish. Nine sheepshead, four from Coot Bay 

and five from Florida Bay, contained a wide variety of food items including 

serpulid polychaete tubes, mussel shell fragments, gammarid and caprellid 

amphipods, isopods, 5 to 10-m oysters, coral fragments, Thalassia blades and 

rhizomes, and brown algae. 

Distribution of Macroinvertebrates 

Four soecies of crustaceans that were collected by otter trawl from July 1984 

through June 1985 were enumerated and weighed or measured: Panulirus ar us 

(spiny lobster), Callinectes ornatus (ornate crab), Callinectes sapidhlue 
Figure 54. Percent occurrence of food i tems in the stomachs of 32 gray 

snapper collected from the mangrove prop root habitat in 

Everglades National Park. N = number of stomachs examined. 

Code: A = amphipod; CR = caridean shrimp; I = isopod; P = 

6 

plant (Thalassia). 

. 

SIZE 

CLASS 

mm(SL) 

< 30 

30-50 

50-75 

75-100 

100-150 

150-250 

>250 

N 

1 

2 

5 

5 

5 

11 

3 

PERCENT 

EMPTY 

STOMACHS 

O 

0 

40 

20 

40 

18 

100 

PERCENT 

20 40 60 80 1 1 

AMPHlPbw 

AMPHIPOD I ISOPOD 

FISH I CRAB 

CARIDEAN I FISH I A I I 

CARIDEAN I FISH I ISOPOD 

FISH I CRAB ICIP 

100 
Figure 55. Percent occurrence of food i terns in the stomachs of 68 gray 

snapper collected from channel habitats in Florida Bay. 

N = number of stomachs examined. Code: A = amphipod; CR = crab; M = mysid; PE = penaeid shrimp; Z = zoea/megalopa. 

SIZE 

CLASS 

mm(SL) 

<30 

30-50 

50-75 

75-100 

100-150 

150-250 

N 

2 

I 

28 

13 

14 

10 

PERCENT 

EMPTY 

STOMACHS 

0 

o 

50 

62 

100 

50 

2 

PERCENT 

20 40 60 80 I I I I 1 1 I I 

ZOEA/MEGALOPA I CARIDEAN 

CARIDEANPENAEID CAR DEAN^ FISH I M I A ( z 

FISH I CARIDEAN I Z 

FISH I PLANT I PE I CR 

100 
crab), and Penaeus duorarum (pink shrimp). With the exception of C. ornatus, 

all are of both commercial and recreational importance, and in somG instances 

fishermen do not make a distinction between the two ~allinectes species. 

Spiny lobsters were taken in five of the seven months of sampling between July 

1984 and June 1985 (September, November, January, March and May). During this 

period, 76 spiny lobster were collected, measured and returned. Total length 

(tip of horns to tip of telson) ranged from 7.2 cm a arch) to 27.5 cm 

(September). The majority of lobsters were collected in September 1984 (28) and 

May 1985 (25) (Table 22). Mean monthly individual lengths were: September 

1984-13.4 cm; November 1984 - 16.2 cm; January 1985-18.5 cm; March 1985-11.0 cm; 

and May 1985-23.7 cm. Lobsters within the size captured by our gear were most 

prevalent (Table 22, Fig. 56) in channels along Twin Key Bank (Channel 21 and 

23), in channels cutting through carbonate mud banks between Panhandle Key and 

Crab Keys (Channel 40 and 34), and in a channel between Bob Allen Keys (Channel 

27). These channels are dominated by Thalassia with mixtures of Halodule or 

Halodule and Syringodium (Fig. 19). One spiny lobster was taken from a pure 

stand of Syringodium in Man of War Channel (Channel 7) and two from a 

Halodule-dominated channel (Channel 33), but in general there appeared to be no 

preference for particular seagrass species. Twenty specimens were taken in 

non-channel samples, one immediately adjacent to Twin Key Bank and 19 adjacent 

to Captain Key a able 22). Both areas are almost pure Thalassia meadows. Our 

observation of lobsters preferring channel areas to open seagrass meadows is 

consistent with Hudson et al. (1970). 

Two s~ecies of callinectid crabs were collected, returned to the laboratory and 

weighed wet: the ornate crab (C. ornatus) and blue crab (L sapidus). 1nseveral instances, lame crabsof the species were returned to the water and not 

weighed. The ornate crab was most numerous (76 taken), and was collected only 

in Florida Bay (Fig. 57), whereas blue crabs (35 collected) were present in 

I Florida Bay, Coot Bay and Whitewater Bay (Figs. 57, and 58). C. ornatus 

apparently moves into shallow waters of the Park during summersince it was1 

I collected only from May through September (Table 23). Although collected in 

channels, this species appeared to prefer seagrass meadows (Table 23), 

particularly those in the vicinity of Bradley and Joe Kemp Key and those in an 

arc transcribed by Cross Bank, Whipray Keys and Panhandle Key in eastern Florida 

Ony (Fig. 57). 

lthough collected throughout the year, the majority (46%] of blue-crabs were 

collected in July 1984 (Table 24). Only four blue crabs were taken ir? Coot Bay 

and Whitewater Bay (Fig. 58) and most were from Halodule beds. In Florida Bay, 

bJue crabs were taken by otter trawl in both channels and seagrass meadows 

(Table 24, Fig. 57), but never were abundant. 

I 

I Florida Bay is considered the primary nursery area for juvenile pink shrimp, 

Penaeus duorarum, which enter the Tortugas shrimp fishery (Allen et al. 1980, 

Schomer and Drew 1982, and references cited therein). Pink shrimp were present 

in collections in every sample month between July 1984 and June 1985, and were 

collected in seagrass beds and channels in Florida Bay, in Coot Bay and in 

Whitewater Bay (Table 25). In both Coot Bay and Whitewater Bay shrimp were most 

frequently collected from vegetated areas (Fig. 58). In neither area, however, 

were shrimp abundant within our trawl catches, never exceeding 20-trawl-l. Pink 

shrimp were collected throughout Florida Bay and generally in low numbers at any 

station; they were in samples at 27 different seagrass and 17 different channel 
Table 22. Wmbers and size range (measured from tip of horn to tip of telson) 

of lobster, Panulirus argus, collected from September 1984 through 

June 1985 in Florida Bay. See Figures 5, 6, and 59 for station 

1 

locations. 

i 

STAT ION DATE lrUMBER SIZE RANGE (cm) 

Channel 7 , Channel 8 

Channel 21 

Channel 22 

Channel 23 

Channel 23 

Channel 23 

Channel 27 

Channel 33 

Channel 34 

Channel 34 

Channel 35 

Channel 40 

Channel 40 

Channel 40 

Channel 44 

20-7 

Captain Key 

Captain Key 

Mar 84 

Nov 84 

 an‘ 85 

May 85 

Sep 84 

Nov 84 

May 85 

Mar 85 

Nov 84 

Sep 84 

May 85 

Sep 84 

Nov 84 

Jan 85 

May 85 

May 85 

Sep -84 

Sep 84 

May 85 
ernulkur~~~q 

Channdo 

Seagraeo a 

Figure 56. Distribution of spiny lobster collected in Florida Bay. 
Table 23. Numbers and total wet weight of Callinectes ornatus collected from 

July 1984 through June 1985 in Florida Bay. See Figures 5, 6, and 

. 59 for station locations. 

Station 

5-6 

10-4 

14-17 

15-16 

15-13 

15-12 , 15-11 

16-17 

16-17 

16-10 

18-9 

18-16 

19-16 . 20-12 

20-14 

21-12 

21-15 

21-15 

23-18 

Oyster Key 

Murray Key 

Captain Key 

Captain Key 

Captain Key 

Crane Key 

Crane Key 

Bradley Key 

Bradley Key 

Joe Kemp Key 

Joe Kemp Key 

Channel 32 

Channel 32 

Channel 35 

Channel 41 

Channel 41 

Channel 22 

Channel 38 

Date 

Jun 85 

May 85 

Jun 85 

Sep 84 

May 85 

Jun 85 

Jul 85 

May 85 

Jun 85 

Jun 85 

Jul 84 

May 85 

3un 85 

Sep 84 

May 85 

Jul 84 

May 85 

Jun 85 

May 85 

Jun 85 

Jun 85 

Jul 84 

Sep 84 

Jun 84 

Jul 84 

May 84 

May 85 

Jun 85 

Jul 84 

Sep 84 

Jul 84 

Jun 85 

Sep 84 

Sep 84 

Jun 85 

Jun 85 

Jun 85 

Number 

1 

2 

1 

1 

5 

3 

1 

3 

2 

1 

1 

2 

1 

2 

1 

5 

2 

2 

4 

1 

3 

2 

1 

7 

1 

2 

3 

1 

2 

1 

2 

3 

1 

1 

1 

1 

3 

Total weight (g) 

35.0 

119.0 

39.0 

54.5 

188.0 

95.2 

22.0 

129.2 

77.1 

23.4 , 

9.2 

M.0 

29.5 

10.9 

16.4 

55.6 

14.5 

16.2 

161.4 

1.0 

4.5 

24.4 

35.2 

78.0 

16.7 

25.8 

76.2 

13.8 

71.4 I 

61.7 

43.0 

140.5 

18.1 

13.8 

6.8 

1.0 

151.9 

TOTAL 
Tame 24. Numbers and total wet weight of Callinectes sapidus collected by otter 

trawl from July 1984 through June 1985 in Florida Bay, Coot Bay and 

Whitewater Bay. See Figures 2,3,5 and 6 for station locations. 

NW = no weight measurement taken. 

STAT ION DATE WFBER TOTAL WEIGHT (9) 

Florida Bay 

4-4 

5-9 

11-10 

14-15 

14-16 

14-1 7 

15-16 

16-10 

18-9 

19-4 . Joe Kemp Key 

Joe Kemp Key 

Joe Kemp Key 

Joe Kemp Key 

Joe Kemp Key 

Murray Key 

Oyster Key 

Channel 32 

Channel 12 

Channel 14 

Channel 33 

Whitewater Bay 

139 

155 

Coot Bay 

32 

65 

Sep 84 

Sep 84 

Sep 84 

Jul 84 

Jul 84 

Sep 84 

Jul 84 

Sep 84 

Jul 84 

Sep 84 

Jul 84 

Sep 84 

Nov 84 

Jan 85 

Mar 85 

Nov 84 

Jul 84 

Jul 84 

Jul 84 

Nov 84 

Nov 84 

Jul 84 

Nov 84 

Jul 84 

Nov 84 

TOTAL =34 
Calhectes ornatus 

Channels 0 

Seagrass 0 

CaMnectes saddus 

Channels rn 

Seagass 

Figure 57. Distribution of ornate crabs and blue crabs collected in 

Florida Bay. 
sites for the stratified random sampling effort (Table 25). They also were 

taken in trawls made at Joe Xemp Key, Bradley Key, Murray Key, Oyster Key, 

Captain Key and Crane Key (Table 25). Shrimp were present in Thalassia, 

Syringodium, Halodule and mixed species meadows, and appeared most abundant at 

the stratified sample stations in November and March. A relatively large number 

(1260trawl-~), however, were collected in September 1984 from a Dure stand of 

Halodule in Snake Bight (Station 5-9) (Table 25). Pink shrimp were relatively 

abundant during all of our routine sampling at Joe Kemp Key +l and Bradley Key, 

but they displayed somewhat different trends in seasonal abundance (Table 25). 

At Joe Kemp Key *1, pink shrimp abundance was maximum in January and March, 

while at Bradley Key it was maximum in March and May. During 1981-1983, Park 

Service personnel sampliqg for shrimp at Joe Kemp Key generally observed peaks 

in May-June and October-November, rather than during winter as we observed 

(Table 26). 

Overall, pink shrimp in the area we sampled displayed a unimodal distribution in 

abundance and a bimodal distribution in mean individual length and wet weight. 

When data from all samples were combined, pink shrimp abundance was observed to 

be maximum in January and March 1985 (Table 26). This trend is not dissimilar 

to trends at some stations observed by Park personnel (M. Robblee, ENP, pers. 

comm. ). Estimates of mean individual wet weight and total length, however, 

displayed bimodal distributions with peaks in November 1984 and March 1985 but a 

depression of valoes during an intermediate sampling in January 1985 (Table 26). 

Allen et al. (1980) also noted a bimodal distribution i~ abundances of 16-25 mm 

total length piqk shrimp at permanent stations in Florida Bay and the Florida 

Keys. The observed peaks in this size class occurred in August and November, 

data points which are 3 months and 4 months earlier than those we observed for 

60 and 65 mm (TL) shrimp, respectively (Table 26). It is possible that the 

16-25 mm shrimp captured in August and the 60 mm shrimp captured in November are 

the same cohorts. Likewise, the November 16-25 mm shrimp and 65 mm March shrimp 

also may be cohorts. If we assume that the shrimp we collected in November and 

March, were around 15 mm (TL) during the preceedinq August and November, 

respectively, this would imply an average growth rate of about 15 mm per month. 

This agrees with Eldred et al. (1961) who showea a 45-20 mm monthly growth rate 

for pink shrimp in Florida waters. 

11. FISH COMMUNITIES UTILIZING RED MANGROVE PROP ROOT HABITATS 

Mangroves dominate the shorelines of south Florida, constituting an estimated 

174,000-202,400 hectares (430,000 to 500,000 acres) of estuarine and coastal 

habitat (Odum et al. 1982). Fringi~g forests of red mangroves, Rhizo hora 

mane, dominate the outer perimeter of protected shorelines and*<Lugo 

and Snedaker 1974). The red mangroves that predominate in this fringe habitat 

have a well-developed prop root system that is flooded semidiurnally by tides 

and may provide habitat to fishes. 

In recent years there has been an increasiig recognition of the general 

importance of the fringing red mangrove habitat to estuari~e-dependent fishes 

(e.g . , Heald 1969, Odum 1970, Carter et a1 . 1973, Lugo and Snedaker 1974, Odum 

and Heald 1975, Yokel 1975, Weinstein et al. 1977, Odum et al. 1982). 

By-and-large, the emphasis has been on the detrital contribution of the I 

mangroves to estuaries and to fishes. Mangrove leaves are a primary source of 

plant detritus in subtropical-tropical systems, and in certain systems many 
Table 25. Numbers, tota1,wet weight and average length (measured from rostrum 

to end of telson) of Penaeus duorarum collected by otter trawl in 

Florida Bay, Coot Bay and Whitewater Bay from July 1984 through June 

1985. See Figures 6, 8, and 59 for station locations. 

- 

Stat ion Date Number x length (mm) Total weight (g) 

. Florida Bay 

3-2 Nov 84 

5-2 Jul 84 

5-5 Sep 84 

5-6 Mar 85 

5-6 May 85 

5-6 Jun 85 

6-2 Sep 84 

6 -2 Jan 85 

6-3 , May 85 

6-4 Jun 85 

6 -6 Mar 85 

6-8 Jun 85 

7-3 NOV 85 

8-10 Jun 85 

9-1 Mar 85 

9-2 . Mar 85 

9-4 Sep 84 

10-4 May 85 

10-9 May 85 

11-1 Jun 85 

14-5 NOV 84 

14-13 Jun 85 

14-16 Mar 85 

15-9 Sep 85 

15-1 2 Jun 85 

16-1 Sep 85 

16-10 Sep 85 

i 7-1 1 NOV 84 

18-16 May 85 

19-5 Jan 85 

22-10 Sep 84 

Joe Kemp Key #l Jul 84 

Joe Kemp Key #l Sep 84 

Joe Kemp Key *l Nov 84 

Joe Kemp Key #l Jan 85 

Joe Kemp Key #l Mar 85 

Joe Kemp Key #1 May 85 

Joe Kemp Key *1 Jun 85 

Joe Kemp Key #2 May 85 

Joe Kemp Key #3 Jul 84 

Joe Kemp Key #4 Sep 84 

Joe Kemp Key #5 Nov 84 

Joe Kemp Key #5 Jan 85 

Joe Kemp Key #5 Jun 85 
Table 25 (Contd). 

Stat ion 

Bradley Key 

Bradley Key 

Bradley Key 

Bradley Key 

Bradley Key 

eradley Key 

Murray Key 

Murray Key 

Murray Key 

Murray Key 

Murray Key 

Oyster Key 

Oyster Key 

Oyster Key 

Oyster Key 

Oyster Key 

Oyster Key 

Crane Key 

Captains Key 

Captains Key 

Channel 7 

Channel 7 

Channel 8 

Channel 8 

Channel 9 

Channel 12 

Channel 13 

Channel 14 

Channel 16 

Channel 21 

Channel 22 

Channel 23 

Channel 23 

Channel 23 

Channel 27 

Channel 29 

Channel 31 

Channel 37 

Channel 38 

Channel 40 

Channel 40 

rCIannel 41 

Date 

Sep 84 

Nov 84 

Jan 85 

Mar 85 

May 85 

.Jun 85 

Jul 54 

Nov 84 

Jan 85 

Mar 85 

May 85 

Jul 84 

Sep 84 

Nov 84 

Jan 85 

Mar 85 

May 85 

Jun 85 

Nov 84 

3un 85 

Nov 84 

Mar 85 

Nov 84 

Jun 85 

Jul 84 

Jul 84 

Mar 85 

Nov 84 

Mar 85 

Jan 85 

Jun 85 

Jul 84 

Sep 84 

Nov 84 

Mar 85 

Jan 85 

Jun 85 

Mar 85 

Jun 85 

Jan 85 

May 85 

Jurl 85 

Z length (mm) 

53 

58 

98 

60 

44 

50 

48 

37 

4 7 

38 

45 

48 

55 

39 

45 

61 

59 

41 

5 7 

63 

60 

66 

49 

44 

44 

40 

66 

50 

66 

127 

35 

58 

64 

67 

62 

82 

139 

72 

38 

90 

71 

63 

Total weight (g) 
Table 26. Total number and wet weight of Penaeus duorarum and weighted 

individual mean wet weights and lengths. Oata are for shrimp 

collected from July 1984 through June 1985 in Florida Bay, 

Coot Bay and Whitewater i3ay r~sirlg an otter rrawl. Val~~es in 

parentheses represent the number of stations at which penaeid 

shrimp were collected. 

Mean Weighted Individual 

Month Number Wet weight (g) Weight Length 

(9) (mm 

Jul 1984 (9) 102 84.8 0.83 46 I 

Sep 1984 (17) 389 384.9 0.99 53 

Nov 1984 (22) 364 499.2 1.34 60 

Jan 1985 (14) 662 534.5 0.81 51 

Yay 1985 (13) 326 348.4 1.07 54 

Jun 1985 (22) 26 5 305.2 1.15 51 
Figure 58. Distribution of blue crabs and penaeid shrimp in eastern 

Whi tewater Bay (upper) and Coot Bay (lower). 
consumers appear to depend primarily on mangrove-derived detrital carbon as an 

energy source (Zieman et al. 1984). The presence of decaying plant matter and 

invertebrate detritivores probably provide rich food sources for foraging 

fishes, but quantitative data on energy transfer are lacking. Since dense 

aquatic vegetation can interfer with predators (e. g., Boesch and Turner 1984, 

Orth et al. 1984), the mangrove prop root habitat also may serve as a refuge 

for fish and invertebrates. 

The use of fringing mangrove habitats by commercial and recreational fishery 

organisms has not been well documented. In a recent review of the ecology of 

mangrove systems in south Florida, Odum et al. (1982) pointed out that while 

fish communities of estuarine bays fringed by red mangroves have been sampled 

and described, fish utilizing the mangrove prop root habitat have not been 

quantitatively sampled. Visual observations abound, but quantitative data are 

lacking. Undoubtedly, the paucity of information on the mangrove habitat has 

been partly due to the inherent difficulty in quantitatively sampling this 

habitat type.' 

The objecties of this st'udy were to quantitatively measure the fish communities 

utilizing the fringing red mangrove habitat over a relatively broad area; and 

compare these fish communities with those in the immediately adjacent habitat 

characterized by rooted aquatic plants. 

i,/li i . AREA AND FETHODS 

Our study was conducted within Everglades National Park in south Florida. Eight 

permanent stations were established, two each in Whitewater Bay, Coot Bay, 

northwestern Florida Bay and southeastern Florida Bay (Fig. 59). Whitewater Bay 

stations were located approximately 1000 m apart in a northeastern embayment 

near East River. Coot Bay stations were located approximately 1800 m apart 

between Tarpon Creek and Buttonwood Canal on the southwestern shore. In 

northwestern Florida Bay, sites were selected about 1500 m apart on the shores 

of Murray Key and Oyster Keys, while in southeastern Florida Bay stations were 

chosen on the shores of Captain Key and Crane Key, about 3000 m apart. 

We used several criteria to select the mangrove stations. All stations were 

intertidal to subtidal with about 1 m water depth at the leading edge of 

mangrove prop roots at high tide. A berm was present 5-10 m shoreward of this 

leading edge, and the prop root habitat continued up to the shoreline. The 

sites were all dominated by Rhizophora mangle, and adjacent to each area were 

seagcss habitats. 

In March 1984, areas were selected and sample sites were prepared. Pipes 

(2.5-cm diameter, 2.8-m long) were driven into the sediment 4-8 m apart at the 

leading edge of each mangrove area. The width of this separation was dictated 

by the expanse of prop roots issuing from a single mangrove clump. Next, a 0.5 

m path was cleared to the berm from each stake perpendicular to the shoreline. 

This activity entailed cutting prop roots to the sediment surface as well as 

removing some overhanging limbs so that a net could be positioned to prevent 

ingress and egress of fish. The data reported are for eight sample periods 

between May 1984 and May 1985. 

All sampling was carried out during daylight at high tide + 2 h using the 

following procedure. In each instance, a 32 m x 2 m net wyth 3-mm mesh was 
Figure 59. Diagram of Florida Bay and adjacent area showing the location of 

mangrove sample sites in Hhitewater Bay, Coot Bay, northwestern 

Ic Florida Bay and southeas tern Florida Bay (underscored). 
used. The bottom of the net was fitted with 6-mm galvanized chain and the top 

of the net with a cork line; wooden staffs were fixed to each end of the net. 

Boats were brought to within 5 m of the site, and 2 individuals initiated 

deployment of the net. The net was carried rolled up to the center of the front 

stakes, unfurled, and spread out by passing around the outside of the stakes. 

Each individual then moved the net up the cut path between mangroves onto the 

shore, pulling the net tight as they moved. The chain line was checked 

immediately and pushed into the sediment to prevent escapement. Thus, the net 

blocked the front and sides of each area with the shore forming the interior 

border. A second net then was set at the nearby second mangrove site. 

Once the two nets were set, rotenone was applied within the blocked area, with 

only one site being treated at a time. Liquid emulsifiable Noxfish (Penic 

Corp) containing 5.0% rotenone (w/w) was diluted approximately 1 :4 with water 

from the area and usually dispensed below the water surface by sprayer, although 

on occasion it wbs applied by bucket and stirred. Four people positioned 

themselves adjacent to the net and/or within the blocked area, and fish 

surfacing were dipped over the next 30 min and preserved in 10% formalin. Very 

few fish surfaced after 20 min, and after 30 min, the chain line of the net was 

gently lifted and additional fish were collected from the wall of the net. It 

was our experience that this latter collecting process provided numerous fish 

that had not been taken by dipping. . We carried out mark and recapture studies to estimate our efficiency of recovery 

using the block net procedure. Silver jenny (Eucinostomus gula) were collected 

by trawl, fin clipped, and held in water for a minimum of 15 min to ensure no 

immediate handling mortality. Approximately 30 live fish then were released 

into each blocked area prior to rotenone application. Other species such as 

gray snapper (Lut janus griseus) , sheepshead (Archosar us robatoce halus ) , 

pigfish (Ortho ristls chrysoptera), barracuda S h raena baracuda , pinfish 

(Laqodon ---IT rhomboides and goldspotted killifish -7- Floridichth s carpio) also were 

used, but silver jenny was the primary species. Mean recovery in January was 

58% (range = 33-82%), while on other occasions it was 75% (range = 66-88%). 

After each mangrove site was sampled, a trawl was deployed to sample the fishes 

of the adjacent seagrass habitat. A one minute otter trawl towed between two 

boats at a speed of approximately 2.0 2 0.2 m/s (3.5-4.5 knots) was taken at 

each station. This trawl was taken as close to the mangroves as was feasible, 

and normally took place 8-10 m from the shoreline in an area that had not been 

disturbed by earlier boat movement to the mangrove site; these samples were 

taken approximately 1-1.5 h after the start of the mangrove samplings. The 

trawl measured 3.4 m at the head rope and 3.8 m at the foot rope and was made of 

6-mm bar mesh with a 3-mm mesh tail bag. The net was fitted with 3-mm 

galvanized tickler chain strung between the trawl boards. One tethered float 

was deployed at the beginning and another at the end of the trawl, and the 

distance between the floats measured with an optical range finder. 

Ancillary data were collected at both mangrove and adjacent trawl stations to 

characterize the habitat. A sample was taken of the surface sediments for 

analysis of organic content (loss of weight upon i g n i t i o n a t 500-C for 24 h) and 

for silt-clay content. The sediment was dried (70°C), weighed, rewetted with 

saturated sodium hexametaphosphate, and wet sieved. Material retained on 4.00 

mm (shell) and 0.063 mm (sand) sieves was redried and the difference between 

initial total dry weight and the sum of these two size fractions taken as a 
measure of silt-clay content; this is a modification of ASTM 11963). Water 

temperature and salinity, and sediment depth (by penetration with a marked pole) 

also were measured. Adjacent to the mid-point of the trawl path a diver took 

three, 100-cm2 quadrate samples of bot-torn vegetation for species identification, 

shoot enumeration, and determination of decalcified (5% phosphoric acid) dry 

weight biomass. 

In January 1985, additional measurements of the root systems were made at each 

mangrove site. All mangrove roots at the level of the water surface (at 

mid-tide) were counted; prop roots exposed in the upper intertidal zone of each 

area also were enumerated. In addition, the diameter of 50 prop roots issuing 

from one or two randomly selected main roots off the trunk were measured using 

vernier calipers. The average diameter of prop roots at the mid-tide water 

surface and the number of prop roots were used to estimate the prop root surface 

area of the site occupied by prop roots. The circumference of each measured 

root also was calculated as an indication of potential surface available for 

epibiotic growth and for grazing by fishes. All measurements were made at a 

water depth of approximately 0.5 m at the leading edge of the mangrove prop 

roots. Thus, in some instances, measurements were made at or near the 

sediment-water interface close to shore. 

Collected fish were identified to species and counted. The maximum, minimum and 

standard length of a 88typical" individual species was measured and the total wet 

weight of each species was determined. In the case of gray snapper (~utjanus 

griseus) standard lengths of all individuals were recorded. Stomach contents of 

gray snapper collected in the mangroves were identified to major taxonomic 

groups : copepods , amphipods , isopods , shrimp, crabs, and fish; only crustaceans 

and fish were observed in snapper stomachs. The number and length of each food 

item was recorded. Gravimetric analysis was not appropriate because of a wide 

range in digestive decomposition and/or regurgitation caused by preservation 

time. These analyses were compared to similar analyses made on gray snapper 

collected from seagrass meadows and channels in Coot Bay, Whitewater Bay and 

Florida Bay collected within the same time frame in a separate phase of our 

study (US NMFS Beaufort Laboratory 1985). These ratter samples were taken by 

two-boat otter trawl. 

Day-night comparisons were conducted during June and September 1985. Only 

September data are presented here since all sites were visited in September. 

Two approaches were employed during the day-night sampling. In September 1985, 

one station in Coot Bay and one in Whitewater Bay were sampled during day while 

the second station of each pair was sampled at night. A second approach was 

used at the four sites in Florida Ray. Each site was used for either a day or a 

night sampling and approximately 60 h later each station was sampled in reverse. 

Thus, a day and a night sample were taken at each of the four Florida Bay sites. 

A total of six comparisons were made, four in Florida Bay and one each in Coot 

Bay and Whitewater Bay in September 1985. 

During the afternoon, prior to sampling a site at night, four 100 watt lights 

with reflectors were placed in the mangroves at each corner of the site and a 

fifth was suspended in the center of the area to be enclosed. Headlamps were 

used by the individuals deploying the blocknet. Once the area was blocked with L 

the sample net, the lights were turned on, powered with a portable generator. 

Sampling was otherwise identical to the daylight technique, and tagged fish 

recoveries did not differ between day and night. 

* 
RESULTS AND DISCUSSION 

Habitat Characteristics 

The areas sampled ranged from generally low salinity and turbid to high salinity 

and clear. Coot Bay and Whitewater Bay sampling areas were characterized by low 

to intermediate salinities with a range of 5.5 o/oo in November 1984 to 20.0 

o/oo in June 1985, and averages of 13.5 o/oo and 16.3 o/oo, respectively (Tables 

27 and 28). Both areas also are characterized by "brown water" presumably 

resulting from dissolved organic matter leaching from mangroves. The Flamingo 

and upper Florida Keys sides of Florida Bay were characterized by high salinity 

water averaging 33 o/oo during our sampling period (range 27-42 o/oo). The area 

in the vicinity of Murray Key and Oyster Keys in the northwestern part of 

Florida Bay is highly turbid as a result of suspension of fine carbonates (Tabb 

and Dubrow 1962). In contrast, water clarity was always high at Crane Key and 

Captair, Key in'the southeastern region of the Florida Bay. Additional . 

characteristics of Whitewater, Coot and Florida Bays have been described by 

numerous individuals (e.g., Ginsburg 1956, Tabb and Manning 1961, Tabb and 

Dubrow 1962, Schomer and Drew 1982, Zieman 1982). 

Characteristics of mangrove and adjacent seagrass sites varied regionally 

(Tables 27 and 28). Blocked mangrove areas varied iq size by 2.7-fold with the 

largest in Coot-Bay and the smallest in Whitewater Bay. At all sites, red 

mangrove prop roots dominated the physical structure of the blocked habitat with 

a range of from 660 to 2293 prop roots or from 13.7 to 45.0 prop roots per m2 

of blocked area (Table 27). With the exception of the more northerly Whitewater 

Bay mangrove site (WE-2; Fig. 59), the total number of mangrove prop roots was 

related to the size of the area blocked. At the four Florida Bay sites, the 

area of open water within each blocked area that was outside the mangrove prop 

rcots was similar, 16.3-20.5 m2. Thus, of the two smaller sites (Captain Key 

and Murray Key) water interdigitated with prop roots represented half the 

blocked area while at the two larger sites water interdigitated with mangrove 

prop roots occupied >60X of the blocked area. Similar measurements were not 

taken in Coot Bay or Whitewater Bay. At the surface of the water at mid-tide 

(or sediment if the area was exposed at the time of measurement), prop root 

diameter ranged from 0.8-4.9 cm with the mean for individual stations ranging 

from 2.3-3.2 cm. These prop roots occupied a total of 0.3-1.6 in2 of water 

surface area at the sites and had collective perimeters ranging from 0.48-2.16 m 

(Table 27); this latter measure may be indicative of the surface available for 

browsing fishes to graze. 

At the trawl sites, located approximately 8-10 m from the mangrove fringe, 

submerged aquatic plants were prevalent. Ruppia maritima, widgeon grass, 

occurred at both of the low salinity areas In Whitewater Bay and Coot Bay, but 

did not occur in Florida Bay (Table 28). This plant also was more abundant at 

the Whitewater Bay areas than at Coot Bay, and during most of the study was 

characterized by having shoots extending to the water surface at the 

southernmost Whitewater Bay site (WB-1). Occasionally, large quantities of the 

alga Chara hornemanni also were present in Whitewater Bay. Halodule wrightii, 

Cuban shoalgrass, was present at both Coot Bay sites, and at Murray Key and 

Oyster Key (Table 28). The density and biomass of shoalgrass was much greater 

at the latter two sites than at the lower salinity Coot Bay areas. A third 

species, Thalassia testudinum, turtlegrass, was present only in Florida Bay and 

was most abundant at the Crane Key and Captain Key sites (Table 28) where it 
Table 27. Characteristics of the mangrove habitats sampled for fishery communities 

WB = Whitewater Bay, CB = Coot Bay. 

Characteristic Mangrove Station 

NC = not completed 

-- WB-1 WB-2 

Sediment 

% organic matter 31 38 

% silt-clay 25 34 

Depth (m) 0.9 0.7 

Water depth (m) 0.9 0.8 

Total Blocked 21.7 53.8 

Area (m2) 

Open water (rn2)l NC NC 

Mangrove Roots 

Total No. 660 735 

- 

X Dia. (cm) 2.3 2.8 

Surface area (m2) 0.27 0.45 

Perimeter (m) 0.48 0.65 

Salinity (o/oo ) 13.1 13.6 

This is a calculation of the area of each blocked habitat that does not have 

mangroves. The difference between the total and this value is the area of 

each blocked habitat surrounded by mangrove prop roots. 

Crane Captain 

26 10 

44 47 

1.7 2.0 

0.8 0.8 

47.6 35.3 

16.5 16.5 

1443 91 5 

3.2 2.6 

1.19 0.49 

1.45 0.75 

33.9 35.5 

-- CB-1 CB-2 

34 40 

28 32 

1.3 1.4 

0.8 0.8 

58.2 30.7 

NC NC 

1745 803 

2.4 2.3 

0.79 0.33 

1.32 0.58 

16.3 16.3 

Murray Oyster 

10 7 

60 3 1 

0.4 2.0 

0.8 0.8 

35.4 51.0 

16.3 20.5 

942 2293 

2.9 3.0 

0.63 1.63 

0.86 2.16 

30.0 33.4 
Table 28. Characteristics of frinqinq - - seaqrass stations sampled adjacent - to manqrove 

prop root habitat sampled. 9M = Ruppia maritima;' HW = Glodule wrightiir 

TT = Thalassia testudinum; CH = Chara hornemanni. 

Characteristic 

-- WB-1 WB-2 

Sediment 

% organic matter 19 20 

% silt clay 57 53 I 

Depth (m) 0.4 0.5 

Water depth (m) 1.1 1.1 

Plant Components 

Species RM RM 

shoot s/m2 3310 493 

g dry weight/m2 52.1 26.0 

Species (cont 'dl CH CH 

shoots/m2 - - 

g dry wt/m2 26.3 10.9 

Salinity (o/oo) 13.2 13.5 

Stat ion 

- CB-1 - CB-2 Murray Oyster Crane Captain 
grew into the outer edge of the mangrove prop root habitat. Adjacent to Crane 

Key, turtlegrass was dense but fairly short, resulting in only a slightly higher 

dry weight biomass than occurred at Captain Key, which displayed almost half the 

number of short shoots per m2. Thus, there was a great deal of variability in 

plant species composition, shoot density and biomass at paired sample sites as 

well as among regions. 

Sediments varied in organic content and silt-clay content both within and 

between habitat types. Both Coot Bay and Whitewater Bay mangrove sediments were 

similar and had high organic contents ranging from a mean of 31-40% (Table 27), 

while adjacent seagrass areas had values markedly lower (Table 28). The high 

and similar organic contents in the mangrove imply a quiescent environment with 

a build up of peat. Murray Key, Oyster Keys and Captain Key, on the other hand, 

had comparatively low organic matter values. Greater tidal amplitude and 

current was measured at Murray Key and Oyster Keys than elsewhere and, thus, 

these areas may be flushed of detrital matter more than other stations. Sand 

and shell particle sizes dominated the sediments of all mangrove habitats except 

Murray Key. The sediments in the adjacent seagrass was dominated by silt-clay 

particle sizes except at Crane Key. 

Relative Abundance of Fish 

A total of 18,482 fish distributed among 87 species and 39 families were 

collected from the mangrove and adjacent trawl stations between June 1984 and 

May 1985. Table 29 provides a listing of species and total numbers collected 

between June and May 1985; May 1984 data have been omitted from this table and 

subsequent analyses to avoid confounding temporal and site differences since we 

were unable to sample Crane Key and Captain Key sites in May 1984. 

Substantially greater numbers and biomass of fish were collected from the 

mangrove sites than from the adjacent seagrass habitats, with approximately 75% 

of the numbers (Table 29) and 68% of the wet weight biomass of fish (36.8 of the 

total 54.2 kg) being taken from the mangroves. 

Data on numbers and biomass for each site and sample date were converted to 

density and standing crop per m2 for further comparisons by dividing total 

values by respective areas sampled by the two gears. The areas of each mangrove 

site ranged from 21.7 m2 to 58.2 m2 (Table 27). The area covered by the otter 

t raw1 in 1 min ranged from 260 m2 to 540 m2 and averaged 351 m2 (SE = 7.7; N = 

62). The effective opening of the otter trawl of approximately 3 m was used in 

calculating area sampled. Numbers and biomass of fish per unit area were summed 

over the survey periods and evaluated using ANOVAs. The model for the ANOVAs 

was that for a split plot design where the "whole-plot" factor was regions in 

the Park sampled (e.g., Whitewater Bay, Coot Bay, northwestern Florida Bay and 

southeastern Florida Bay), and the subplot factor was sampled habitat (mangrove 

vs. adjacent seagrass). Because of heterogeneity of variances, the data were 

transformed to logarithms prior to calculations. 

There were significantly higher numbers and biomass of fish per m2 in the 

mangrove habitats than in the immediately adjacent fringing seagrass habitats 

(Table 3Oa, b). The average (geometric mean) density of fish collected in the 

mangroves (8.0/m2) was about 35-times that collected in the immediately adjacent 

habitat (0.22/m2) on an areal basis. There was no evidence of an interaction 

between region and habitat type or of differences among the four regions (Table 

$ 
Table 29. List of families and species of fish collected in mangrove prop 

root and adjacent seagrass sites in Coot Bay, Whitewater Bay, and Florida Bay during June 1984-May 1985 and the total numbers 

of each species collected. 

Family-Species Mangrove Trawl Total 

Oas yat idae kt ingray;( Dasyatis americana - southern stingray 

Elopidae [tarpons] Elops saurus - ladyfish 

Anguillidae Grehwat er eeld 

Anguilla rostrata - American eel 

Ophichthidae hake eels] 

Myrophis punctatus - speckled worm eel 

Clupeidae herrings] Brevoortia smithi - yellowfin menhaden 

Harengula Jaguana - scaled sardine 

- H. humeralis - redear sardine 

Jenkinsia lamprotaenia - dwarf herring 

Engraulidae - hchovied 

Anchoa he setus - striped anchovy 

- A. mitc * 1111 bay anchovy 

Synodontidae hi zardfished 

Synodus foetens - inshore lizardfish 

Ariidae Lea catf ished 

-- Arius felis - hardhead catfish 

Batrachoididae rtoadf ished 

Opsanus beta - gulf toadfish 

Gobiesocidae [clingfished Gobiesox strumsus - skilletfish 

Exocoet idae [flyingf ished 

Chriodorus atherinoides - hardhead halfbeak 

Hyporharnphus unifasciatus - halfbeak 

Belonidae beedlef ished 

Strongylura marina - Atlantic needlefish 

S. notata - redfin needlefish -. 

- S. timucu - timucu 
Table 29 (~ont'd) 

Famil y-Species Mangrove Trawl Total 

Cyprinodontidae [killif ished 

Cyprinodon variegatus - sheepshead minnow 

Floridichthys carpio - goldspot killifish 

Fundulus confluentus - marsh killifish 

- F. grandis - gulf killifish 

- F. similis - longnose killifish 

- F. seminolis - seminole killifish 

Lucania parva - rainwater killifish 

Poecili idae hivebearers1 

Gambusia af finis - mosquitofish 

Poecilia latipinna - sailfin molly 

Atherinidae [silversidesl 

Atherinomorus stipes - hardhead silverside 

Hypoatherina harringtonensis - reef silverside 

Membras martinica - rough silverside 

Menidia peninsulae - tidewater silverside 

Syngnathidae bipefishesI 

Hippocampus erectus - lined seahorse 

- H. zosterae - dwarf seahorse 

Synqnathus dunckeri - pugnose pipe fish 

- S. floridae - dusky pipefish 

- S. louisianae - chain pipefish 

- S. scovelli - gulf pipefish 

Centropomidae [snookd 

Centropomus undecimalis - snook 

Centrarchidae [sunfishesl 

Lepomis macrochirus - bluegill 

- L. punctatus - spotted sunfish 

Carangidae [jacks] 

Caranx hippos - crevalle jack Oligoplltes saurus - leatherjacket 

Selene - vomer - lookdown 

Lut janidae [snappers] 

Lutjanus griseus - gray snapper 

- L. synagris - lane snapper 

- L. apodas - schoolmaster 

Gerreidae bo.iarras1 

~ucinostomk arqenteus - spot f in mo jarra 

- E. gula - silver jenny 
Table 29 (~ont'd) 

Family-Species Mangrove Trawl Total 

~aemulidae [grunts] 

Haemulon aurolineatum - tomtate 

-- H. uarrai - sailors ~ -~- choice - 

- H. plumieri - white grunt 

- H. sciurus - bluestriped grunt Orthopristis chrysoptera - pigfish 

Sparidae borgiesl 

Archosargus probatocephalus - sheepshead Calamus arcti'frons - grass porgy 

Lagodon rhomboides - pinfish 

Sciaenidae [drums] 

Bairdiella chrysoura - silver perch - 

Cynoscion nebulosus - spotted seatrout 2 

Menticirrhus 'littoralis - gulf kingfish - 

Pogonias cromis - black drum 

Sciaenops ocellatus - red drum 

Scar idae barrot f ishesl 

Sparisoma rubripinne - redfin parrotfish - 1 1 

Mugilidae bullets] 

Mugil cephalus - striped mullet 32 - 32 

- M. curema - white mullet 45 1 46 

Sphyraenidae barracudas~ 

Sphyraena barracuda - great barracuda 

Clinidae [clinidd 

Paraclinus fasciatus- banded blenny 

Blenniidae [combtooth blennies] 

Chasmodes saburrae - Florida blenny 

Callionymidae [dragonets] 

Callionymus pauciradiatus - spotted dragonet 10 4 14 

111 1 G&i idae [gobiesl Bath obius so orator - frillfin goby 

hoked goby 

7 

G. robustum - code goby 

Lophogobius cyprinoides - crested goby Microgobius gulosus - clown goby 
Table 29 (~ont'd) 

Famil y-Species Mangrove Trawl Total 

Acanthuridae [5urgeonf ished 

Acanthurus chirurgus - doctorfish 1 - 1 

Triglidae [searobins] 

Prionotus scitulus - leopard searobin 

- P. tribulus - tighead searobin 

Bothidae [lefteye flounders] 

Paralichthys lethostigma - southern flounder 

- P. albigutta - gulf flounder 

Soleidae [soles] 

Achirus lineatus - lined sole 

Trinectes maculatus - hogchoker 

Cynoglossidae [tonguefishes] 

Symphurds plagiusa - blackcheek tonguefish 1 

Balistidae [triggerfishesl 

Aluterus schoepfi - orange filefish 

Monacanthus ciliatus - fringed filefish 

- M. hispidus - Planehead filefish 

Tetraodont idae buffers] 

Sphoeroides nephelus - southern puffer 

Diodont idae [porcupin~f ishes] 

Chilomycterus schoepfi - striped burrfish 
3Oa). The densities of fish collected in the red mangrove prop root habitat 

exceeded those from the adjacent habitat in all 62 collections (Table 3la). 

Analysis of biomass on an areal basis similarly detected significant differences 

among habitats and no evidence of an interaction between region and habitat or 

of differences amon regions (Table 3Ob). The average biomass of fish in the 

mangroves 9. (15.0 g/m ) was about 19 times greater in the mangroves than in the 

adjacent habitat (0.8 g/m2). The biomass of fish taken from the mangroves 

exceeded those values from the adjacent seagrass meadows in 57 of the 62 

samples, and the occasions when values for the adjacent habitat exceeded the 

mangroves were at Coot Bay (Table 3lb). Here, catches of hardhead catfish 

(Arius felis) were responsible for the higher seagrass-trawl standing crops of 

fish. Fish taken from the mangroves were considerably smaller than those taken 

from the adjacent seagrass area, i.e., 1.9 g (wet weight) fish-1 vs. 3.5 

g*fish-l. In as much as we might expect some larger fish to be more adept at 

avoiding the trawl even at this high tow speed but not less susceptible to the 

rotenone, the actual difference in mean size may be greater than the data 

indicate. 

We recognize that some of the differences observed between densities and 

standing crops of fish collected in the two habitats may be the result of 

differences in the efficiency of the two gears used. Our estimates of the 

efficiency of the block net-rotenone technique are based on tagged fish released 

into each blocked-area prior to rotenone application. These estimates provided 

a mean recovery of approximately with a mean of 58% in January and 75% 

thereafter. In January when water temperatures were about 17-2O0C, fish tended 

to sink rather than surface when rotenone was applied. We have no estimate for 

the efficiency of the two-boat otter trawl. Trawl efficiencies vary among 

species and sizes of fish. Kjelson and Colby (1977) estimated that the gear 

efficiency of a 6.1 m otter trawl towed by a single boat at about 0.8 m/s during 

the day ranged from 16-69% for juvenile pinfish and spot. Increasing the tow 

speed as we did to 1.8 to 2.2 m/s should have reduced the ability of fish to 

avoid the trawl, but even if the trawl had an efficiency of only 20%, our data 

would still imply much lower fish densities and standing crops in the adjacent 

seagrass meadows then in the mangrove habitats. The use of two boats greatly 

aids in attaining and maintaining this speed in trawling through grass beds as 

well as in maintaining the doors open to the maximum possible extent. The 

estimates of density obtained by this trawl method (1 min, 2 boat, 3.5-4.5 

knots) over submerged grass beds are not dissimilar to those obtained throughout 

Florida Bay, Coot Bay and Whitewater Bay in over 250 trawls (2 min, 2 boat) over 

both vegetated and unvegetated bottoms (Part I of this report). We conducted 

some preliminary trials using a 4.0 m2 Wegener ring and rotenone in the fringing 

seagrass habitat, but this approach normally yielded very low numbers of fish 

per ring and very low diversity. The estimates we obtained for the fringing 

seagrass areas, while low, are in the range collected from other meadows in 

Florida: 0.2-2.0 m2 in Biscayne Bay seagrass beds (Sogard 1982); 0.3-1.5 m2 in 

Apalachee Bay and ~0.6 m2 in Indian River (computed by Sogard et al. MS In 

press). Sogard et al. (In press), however, reported mean densities of 11 

fish=m2 on several carbonate banks in Florida Bay using 1 m2 in throw traps. 

We observed an overall seasonal trend in both mean numbers and biomass of fish 

at mangrove and adjacent seagrass sites. The overall density and standing crop 

of fish were maximum in fall in the mangrove habitat; this habitat type also 

displayed the greatest month-to-month variation in mean values (Fig. 60). 

There was an increase in abundance during autumn and again in spring; mean 
Table 30a. Analysis of variance of total numbers of fishes per square meter 

taken in the surveys conducted between June and May. The data are 

transformed to logarithms of total number + 1.0 prior to the 

calculations. 

Source d f Mean Square F 

Among Regions 3 0.4002 2.57 

Among Blocks 1 0.0067 

Mainplot Error 3 0.1554 

Mangrove vs. Seagrass 1 11.4274 94.73* 

Region X Mangrove-Seagrass 3 0.6129 5.08 

Subplot Error 4 0.1206 

Table 30b. Analysis of variance of total biomass of fishes per square meter 

taken in the surveys conducted between June and May. The data 

were transformed to logarithm of total'biomass + 1.0 prior to 

the calculations. 

Source d f Mean Square F 

Among Regions 3 0.4398 3.54 

Among Blocks 1 

Mainplot Error 3 

Mangrove vs. Seagrass 1 

Region X Mangrove-Seagrass 3 

Subplot Error 4 
> ,'-- -\ 

-vadjacent seagrass ----.- -\ 

,HA-----. --./@# 

. 

I 1 I 1 I I I 

MJJ S N J M M 

1984 1085 

---- * ----- 4 /'- I I --- adjacent seagrass \ 

0)---' 

-. ---- - ----- 

2 Figure 60. Average abundance and biomass of fishes (per m ) taken from eight 

mangrove prop root habitats and eight adjacent seagrass habitats in 

Everglades National Park. 

1 48 
biomass also increased in autumn but decreased between March and May 1985. The 

precipitous decrease in the mean standing crop biomass of fishes collected among 

the mangrove prop roots in January 1985 coincided with a predominance of early 

stage juvenile (17-21 mm, standard length) silver jenny (Eucinostomus 91, 

rainwater killifish (Lucania parva) and sailfin mlly (Poecilia latipinna , and 

a decrease in the average wet weight per individual (0..g).hese data suggest 

spawning occurs during late autumn for these species in the Florida Bay area, 

and that the mangrove prop root habitat may provide refuge from predators. 

Although small individuals also were present two months later in March, the 

average individual was larger and ranged in size from 27-47 mm for silver jenny, 

19-27 mm for rainwater killifish and 22-35 mm for sailfin molly further 

suggesting that this habitat may be important in the growth and survival of 

these species. In the adjacent seagrass habitat there was a slight trend for 

density and standing crop values to be higher in summer and decrease during 

fall. The wet weight of an average individual was minimum in November (1.9 g). 

Small (c 20 mm) silver jenny and rainwater killifish were present in the 

seagrass habitat during January and March, but larger individuals (> 30 mm) were 

the rule. We believe that the abundance of early stage juvenile silver jenny, 

rainwater killifish and sailfin molly among the red mangrove prop roots relative 

to the adjacent seagrass habitat implies a major refuge role for the prop root 

habitat. 

Species Composition and Habitat Comparisons 

The ten dominant species for the overall study period (June 1984-May 1985) in 

decreasing order of abundance were: hardhead silverside (Atherinomores stipes), 

silver jenny, bay anchovy (Anchoa mitchilli), goldspotted killifish, rainwater 

killifish, spot fin mojarra -Gqentus),ode goby (Gobiosoma robustum), 

striped anchovy (A. he setus7, gulf pipefish (Syngnathus scovelli), clown 

goby (~icrogobius gulosus +r Silver jenny, bay anchovy and gulf pipefish were 

more abundant in the adjacent seagrass meadows than in the mangrove sites. The 

other seven dominants, however, were relatively more abundant among the mangrove 

prop roots (Table 29), and hardhead silverside were taken only among the 

mangrove prop roots. Only a few of these ten species are listed among the 

dominant species i~ previous collections in Florida Bay, Coot Bay and Whitewater 

Bay, although most occur frequently but not in abundance (Tabb and Manning 1961, 

1962; Odum et al. 1982; Sogard et al. in press). We believe that this general lack of information on prevalent species in south Florida is in part due to the 

paucity of information on mangrove and shore communities in south Florida. 

Carter et al. (1973), however, do report that the mojarras (Eucinostomus spp. ), 

were among the dominant species collected in areas of the Ten Thousand Islands, 

Florida. 

The overall composition of the mangrove-fish community collected during the day 

was more diverse than .that we collected in the immediately adjacent seagrass 

habitat. The families Atherinidae, Cyprinodontidae, Gerreidae, Engraulidae and 

Gobiidae were represented most abundantly among the mangrove prop roots, while 

the Gerreidae, Engraulidae, Cyprinodontidae and Sparidae were most prevalent in 

the seagrass (Table 29). Thirty-six species were collected exclusively in the 

fringing mangrove habitat while 24 species were taken exclusively in adjacent 

waters. Another 27 species were collected in both habitats (Table 29). 

Thirty-one species were collected only once and 17 of these were collected in PI 

the mangroves. Based on a few day-night comparisons (see later), the diversity 

in the mangrove habitat appear to increase at night. 

6 
Table 3la. Density of fish (number m2) collected from mangrove and adjacent 

seagrass sites in Everglades National Park, Florida. 

- Date 

Murray Key 

Mangrove '1.2 

Seagrass 0.07 

Oyster Keys 

Mangrove 0.9 

Seagrass 0.09 

Crane Key . Mangrove NS 

Seagrass NS 

Captain Key 

Mangrove NS 

Seagrass NS 

Whitwater Bay - 1 

Mangrove 3.1 

Seagrass 0.09 

Whitewater Bay - 2 

Mangrove 1.9 

Seagrass 0.21 

Coot Bay - 1 

Mangrove 0.9 1.0 2.6 9.0 2.7 1.9 0.3 3.7 

Seagrass 0.14 0.03 0.12 0.21 0.63 0.02 0.21 0.39 

Coot Bay - 2 

Mangrove 0.8 0.6 1.4 6.5 7.4 1.4 0.9 4.0 

Seagrass 0.09 0.22 0.37 0.71 1.4 0.05 0.08 0.03 

NS = no sample 
Table 31b. Wet weight standing crop of fish (g/m2) collected from mangrove and adjacent seagrass sites in Everglades National Park, Florida. 

- Oat e 

Murray Key 

Mangrove 

Seagrass 

Oyster Keys 

Mangrove 

Seagrass 

Crane Key 

Mangrove 

Seagrass 

Captain Key 

Mangrove 

Seagrass 

Whitewater Bay- 1 

Mangrove 

Seagrass 

Whitewater Bay- 2 

Mangrove 

Seagrass 

Coot Bay - 1 

Mangrove 

Seagrass 

Coot Bay - 2 

Mangrove 

Seagrass 

6 = no sample 

b 
Fish communities among the geographic regions and between the mangrove and 

adjacent seagrass habitats were compared using data on 56 species that were 

collected from at least two of the eight sampling areas during the course of 

this study. Our initial analysis was based on the presence and absence of 

species. We used the absolute value of the correlation as a measure of 

similarity (BMDP 19831, and followed a complete or maximum distance linkage rule 

as recommended by Gauch (1982) in forming clusters. There was a clear 

separation of the mangrove and adjacent seagrass fish communities we collected 

during daylight (Fig. 61). With the exception of the adjacent seagrass 

communities in Coot Bay and Whitewater Bay (Fig. 61), replicates within a given 

habitat and region resembled one another more closely than communities within 

that habitat in other geographical regions. 

Eleven species,were collected in every region and in both habitats. Three of 

these species, silver jenny, rainwater killifish and spotfin mojarra, were 

collected at every one of the 16 sites and were among the dominants we collected 

during the study (Table 29). The mojarras (Eucinostomus spp.) are reported to 

be dominant species in the mangrove-lined bays in the Ten Thousand Islands 

(Carter et al. 1973; Colby et al. 1985), and Tabb and Manning (1961), sampling 

in mitewater Bay, Coot Bay, and Florida Bay, reported the two mojarra present 

but not abundant in the brackish waters of Coot Bay and Whitewater Bay. In our 

collections, hawever, both were among the dominants in the mangrove and adjacent 

seagrass fish communities, with densities in Coot Bay and Whitewater Bay 

frequently exceeding those at the high salinity sites in Florida Bay. The 

rainwater killifish, reportedly abundant in low salinities (Tabb and Manning 

1961; Carter et al. 19731, was most abundant in our study among the mangrove 

prop roots and was collected in greater abundance in higher salinity in 

southeastern Florida Bay sites at Crane Key than at either of the lower salinity 

Coot Bay or Whitewater Bay sites. Other species, normally associated with grass 

flats or bay bottoms (e.g., pinfish, code goby, gulf pipefish) and open water 

conditions (e.g., bay anchovy, timucu) were taken in both habitats. Juvenile 

gray snapper, an important recreational species in Everglades National Park, was 

taken in both mangrove and seagrass habitat types but most frequently in the 

mangrove prop root area. The only site we did not collect gray snapper among 

the mangroves was at Murray Key, and our only samples of gray snapper in the 

adjacent seagrass meadows were at Captain Key and Crane Key. Although densities 

of gray snapper were low, when one considers the linear extent of mangrove 

fringe present in south Florida, the prop root habitat must be considered 

important to the production of this sport fish. 

There were fourteen species of fish collected on more than one occasion (Fig. 

61). The hardhead silverside was the most abundant fish collected, and was 

taken almost exclusively from mangrove habitats in Florida Bay at Crane Key and 

Captain Key during autumn and spring; this species did appear once in Whitewater 

Bay collections, and therefore does not show up on this figure. Two killifish 

and one needlefish were collected in all four geographic regions. Both species 

of killifish were reported as rare in the area by Tabb and Manning (1961) and 

were not collected in the bay system of the Ten Thousand Island region by Carter 

et al. (1973) or Colby et al. (1985); it must be remembered that none of these 

investigations sampled the mangrove habitat per se. Among these mangrove sites, 

the sail fin rnolly , mosquitofish (Gambusia af finig and skillet fish (Gobiesox 

strumsus) did not appear to be restricted by salinity, being collected at the 

high salinity southeastern Florida Bay mangrove sites as well as at the much 

lower salinity mangrove sites (see Table la, b for salinity values) in Coot Bay 
H H 

Marsh Killlflsh Florida Blenny 

Crested Ooby Redear Sardine 

Atlantic - Needlefish Banded Blenny 

Leatherjacket 

M 

Pigflsh 

Chain Plpefish - Tomtate 

s w 

Pugnose Plpefish 

Sailfin Molly Sllver Perch 

Skllletflsh 

Mosquitofish 

I I 

Redfln Needlefish 

Longnose Killlfl~h 

Gulf killifish 

I Tlmucu 4 

Gray Snapper 

code ~oby Pinfish 

Bay Anchovy 

Gulf Toadfish 

Goldspotted Kllllflsh 

Gulf Plpeflsh 

Rainwater Killlflsh* 

Sllver Jenny* 

Spotfln MojarraS 

*taken at each of the 18 sampling sltea 

Figure 61. Cluster analysis of sixteen sample sites in Everglades National 

Park based on occurrence of 56 species of fish. Species common 

to the various regions and habitats are shown in the lower portion 

of the fiwre. 
and Whitewater Bay. Odum et al. (1982), however, do not report the sailfin 

molly from low salinity mangrove-lined habitats in south Florida. Marsh 

ki 11 if ish (Fundulus conf luentus ) , crested goby (Lophogobias cyprinoides ) and 

Atlantic needlefish (Strongylura marina), all collected o~ly in low numbers 

among the mangrove prop roots, were restricted to the low salinity sample sites, 

while the redear sardine (Harengula humeralis) (119 individuals) as well as two 

blennies were present only in the mangrove habitats near the Florida Keys (high 

salinity). Mullet (Mugil spp.), a commercial fish in Florida Bay, was collected 

only at Oyster Keys and Murray Key. Of the 72 mullet collected (Table 29), 71 

were taken among the mangrove prop roots, but, in this instance we know that 

trawling would under-sample juvenile and adult mullet. These fish presumably 

feed on sediments and detritus. Thus, our data show that several of the species 

using the fringing prop root habitat are of commercial or recreational value, 

while many are important forage organisms for predatory fish. 

I 

Unlike the prop root community, no species collected from the adjacent seagrass 

habitat was present in all four sampling regions. Silver perch (Bairdiella 

chrysoura) was the most ubiquitous, being collected i n a l l seagrass areas except 

at Captain Key and Crane Key. This species is reported as the most abundant 

sciaenid in the Florida Bay area (Tabb and Manning, 1961). Although not one of 

the dominant fish collected in our study, it was shown to be among the most 

abundant organisms in the mangrove-lined bay system of the Ten Thousand Islands 

on the west coast of Florida (Carter et al. 1973; Colby et al. 1985). Several 

species (i.e., pigfish, chain pipefish, tomtate) were restricted to the high 

salinity seagrass sites adjacent to the mangroves in Florida Bay or just to 

those fringing seagrass meadows we sampled in northwestern Florida Bay (Fig. 

61). Their distribution was consistent with the observation of Tabb and Manning 

(1961) that these species generally are most prevalent on vegetated bottoms in 

high salinity areas of Florida Bay rather than in Coot Bay or Whitewater Bay. 

A second analysis, based upon logarithms of species abundances, resulted in a 

somewhat different grouping of the 16 sampling sites (Fig. 62). The major 

difference from our first approach (analysis of presence) was that the mangrove 

fish communities in northwestern Florida Bay more closely resembled the seagrass 

communities than they did the other mangrove communities when data on total 

abundance were employed. Interestingly, these two stations were more similar to, 

the seagrass communities of Whitewater Bay and Coot Bay than to the seagrass 

communities immediately adjacent to them in western Florida Bay. With several 

exceptions, there was again a tendency for replicates to more closely resemble 7 

one another than samples from other habitats or other regions. 

Examination of the species abundance data suggested that the main reason the two 

mangrove communities of northwestern Florida Bay more closely resemble the 

adjacent fringing seagrass communities than mangrove communities in other 

regions was that these two sites contained few species that were markedly 

abundant in the other mangroves sites sampled, i.e., striped anchovy, 

mosquitofish, skillet fish, naked goby (Gobiosoma bosci) , code goby, gulf 

toadfish (Opsanus - beta), clown goby (Microgobius gulosus) , and sail fin molly . These two sites also contained certain species, such as the inshore lizardfish 

(Synodus foetens), that were otherwise found only in fringing seagrass sites. 
WATER BAY FLORIDA 

WHITE- COOT WESTERN WESTERN EASTERN 

WATER BAY FLORIDA FLORIDA FLORIDA 

BAY (M) BAY BAY (s) BAY BAY BAY 

(1111) (MI (S) (MI (S) (S) 

Figur% 62. Cluster analysis of 16 samples sites in Everglades National Park based on logarithm of 

abundance of 56 fish species. Mangrove and seagrass sites denoted by (m) and (s), respectively. 
Day-Night Comparisons 

Those species that dominated mangrove samples collected in daytime between June 

1984 and May 1985 .(Table 29) also were the dominant species collected during 

both' the day and night in September 1985 (Table 32). There was, however, a 

tendency for Opsanus beta (gulf toadfish), Strongylura notata (redfin 

needlefish), and Menidia peninsulae (tidewater silversim be important 

components of the community sampled during the day-night phase of the study. 

Four species, Diapterus lumieri (striped mo jarra) , Ortho ristis chrysoptera 

(pigfish), Haemulon plumieri + white grunt), and -- Arius * fells hardhead catfish) 

were taken in the day-night sampling but had not been collected ~reviously. All 

but the striped mojarra are considered recreational species, and' all were 

collected at night; only the white grunt was collected during both day and night 

(Table 32). These data suggest that some recreational and/or commercial fish 

may move into the prop root habitat at night to either feed or rest, and that 

extensive night sampling might provide additional species of fish to our list of 

those frequenting mangrove habitats. 

An examination of the data in Table 32 reveals that while fish densities tended 

to be higher during daylight, this was not invariably true, even for a given 

species. Similqrly, the numbers of species in samples taken at night were 

greater than in those taken during the day in five of the six paired comparisons 

(Table 32); often these differences are the consequence of the addition of 

relatively uncommon species of higher trophic levels. Finally, Shannon-Weiner 

diversity indices computed for the twelve samples also fail to show a consistent 

relation to the two temporal periods; in four cases they were higher at night 

whereas in the other two comparisons they were higher for the daytime samples 

(Table 32). 

The binomial theorem provides a basis for testing the null hypothesis that a 

given species has an equal likelihood of being collected from the mangrove 

habitat during either the day or night. For example, if a species was taken on 

four different occasions, then the probability (under the null hypothesis) that 

all four samples were either night samples or were day samples is 0.125. To 

demonstrate a consistent day-night difference in a species' use of the mangrove 

prop root habitat then, we would require a consistency extending over at least 

six independent observations, wherein the probability would be less than 0.05 

(actually it would be 0.0313 for six observations). We only had six paired 

observations from our samples, which is the minimum required number. Not one of 

the 34 species taken in the six pairs of samples demonstrated that level of 

consistency. The species that had the highest consistency with respect to being 

taken exclusively during either the day or the night was S h raena barracuda. 

It was taken only during the day and on three occasions (& Although only 

suggestive, Floridichthys carpio was most frequently more abundant (5 our of 6 

collections) during the day as were Eucinostomus ar enteus (3 of 4 collections), 

Menidia peninsulae (2 of 2), and Strongylura timucu +- 2 of 3). Strongylura 

notata was collected only at night on four of five occasions; on the fifth 

occasion more were captured during the day than at night. Lutjanus griseus also 

was encountered more frequently at night in these trials. 

It should be apparent that the geographical differences in the fish communities 

of the mangrove prop-root habitat observed in the earlier sampling make our 

investigation of day-night differences in u t i l i z a t i o n o f the habitat very 

conservative, because the test of the day-night hypothesis for a given species 
Table 32. Density of fish (no. m-2) collected in day-night sampling in Everglades National Park in September 1985. 

Whitewater Coot hrray Oyster Captain Crane 

Bay Bay Key Keys Key Key 

Day Night Day Night Day Night Day Night Day Night Day Night 

(9/6/85) (9/6/85) (9/6/85) (9/6/85) (9/5/85) (9/7/85) (9/7/85) (9/5/85) (9/8/85) (9/10/85) (9/10/85)(9/8/85;1 

Anquilla rostrata 

'Harengula jacuana 

Anchoa hepsetus 

- Anchoa. mitchilli 

-- Arius felis 

Opsanus beta 

Table Continued 
am 

COD n\ 

..I b => 
requires a consistency of behavior over six paired comparisons. In this case, 

this means the test is only appropriate and applicable to those ubiquitous 

species that were found in all geographical locations encompassed by the study 

since only six paired comparisons were made. The fact that the geographical 

'ifferences confounded the day-ni-ght comparisons implies that a better strategy 

3r a future investigation would be to confine sampling to one general locale 

~d to increase the number of paired day-night collections well beyond a minimum 

##dmber of six. The use of rotenone may have influenced the results, although 

this was not apparent from an examination of Table 32. In areas where there is 

sufficient-tidal amplitude, the block net technique can be used without rotenone 

provided that a reservoir or cod end of the net is placed on the outer-most side 

in which to collect fish. 

Ogden and Zieman (1977), McFarland et al. (19791, Zieman (1982), and Robblee and 

Zieman (19841, have described interactions among reef and seagrass communities, 

and noted that fish exhibit both diurnal and nocturnal patterns of migration 

from reefs and exploitation of adjacent seagrass meadows. Ogden and Zieman 

(1977) reported that foraging out from reefs during the day is primarily by 

small (< 15 cm) or large (> 40 cm) herbivorous fish and that nocturnal feeding 

migrations occur primarily among carnivorous fish species. They also suggest 

++at intermediate-sized fish (20-40 cm) appear to be excluded from daylight 

zeding in seagrass meadows by predatory fish and the lack of sufficient hiding 

lace within the 2-dimensional seagrass canopy. Starck and Davis (1966) noted 

~nat many fish species may not be present or present only in low numbers over 

potentially available forage areas due to the absence of diurnal resting areas 

such as patch reefs. In support of this hypothesis, Zieman (1982) noted that 

when artificial reefs were placed in the Virgin Islands they were rapidly 

colonized by juvenile grunts indicating the importance of shelter in the 

vicinity of the seagrass feeding grounds. 

In a review of seagrass-mangrove interactions, Zieman (1982) pointed out that, 

although it is known that some species of fish recruit initially into seagrass 

habitats and move into mangrove-dominated areas as juveniles, little information 

was available on the interaction between mangrove habitats and seagrass meadows. 

It is well known that mangrove-lined estuaries and bays are utilized by a wide 

variety of juvenile and adult fish (e.g., Odum et al. 1982, Colby et al. 1985), 

and we have earlier (Thayer et al. In press a) hypothesized that relations 

observed between seagrass and coral habitats also may exist in the 

mangrove-seagrass dominated systems. 

The fish species we collected among the red mangrove prop roots were primarily 

small forage species or juveniles of large-sized species (e.g., S. barracuda, 

- S. timucu, L. m, S. notata, A. rostrata). Occasional large adults were 

collected bx this was not a commonoccurrence. Most of the individuals 

collected were less than 15 cm and should be able to exploit adjacent seagrass 

beds during daylight because the grass blades can provide protective refuge. 

Most of the species we collected among the mangrove prop roots during the day 

also were present in our limited night sampling. It is possible that the prop 

root habitat serves as a refuge during the day even for these small species and 

that members may forage out into the adjacent seagrass meadows at night. It is 

possible that the prop root habitat serves as a refuge during the day even for 

these small species and that members may forage out into the adjacent seagrass 

meadows at night. A few species, however, were only present at night. The 

day-night comparisons we conducted were sufficiently few in number that they do 
not provide significant consistent results on diurnal or nocturnal patterns of 

use, although they are suggestive in some cases. Hypotheses can be developed 

and tested based on these data. 

Conclusions 

within' the geographical area encompassed by our study, the intertidal fringing 

red mangrove prop root habitat and immediately adjacent seagrass meadows support 

different fish communities during daylight and night hours. Despite the fact 

that both sampling techniques employed were less than 100% efficient, the data 

show fringing red mangrove prop root habitat is of major importance for a wide 

variety of fishes. This habitat appears to support an overall greater density 

and standing crop biomass of fishes than the adjacent fringing seagrass habitat. 

Several species utilizing the mangroves are of commercial and recreational 

importance, while many are forage foods for predatory fishes. There also appear 

to be trends toward higher abundances of fishes among the prop roots during 

daylight and a greater diversity of fishes at night. It seems likely that 

increasing the sample size either by sampling additional examples of each 

habitat within each region, or by extending the sampling period in time, might, 

to some extent, blur some of the boundaries of the fish communities that have 

emerged from this analysis. It is nevertheless clear that these two major 

habitats fulfill different functions for different species of fishes during the 

day and that both-are essential to the viability of fish production in this 

region. 

The data do demonstrate that forage fishes predominate and that, as would be 

expected, juveniles of high trophic level carnivores represent only a small 

fraction of the organisms utilizing this habitat. Although the numerical 

abundance of commercial and recreational fish utilizing this prop root habitat 

was never large, when one considers the fact that 60-70% of tropical shorelines 

are mangrove-lined, they must be viewed as an important nursery area. The 

importance of the forage fish component to piscivorous fish and birds cannot be 

overstated. Since the maintenance of fishery resources requires adequate 

spawning, feeding and refuge habitat, it is probable that the cumulative loss of 

fringing mangroves to any development eventually will result in reduced fishery 

populations in subtropical and tropical environments. A great deal more is to 

be learned about the role of mangroves in the production of fishery organisms, 

and the techniques and data we have presented provide a basis on which to 

develop testable hypotheses. 

Overall losses of mangroves in south Florida have not been great but there have 

been substantial losses in specific locations (Odum et al. 1982). Because 

degredation of these habitats is continuing to occur both through natural and 

man-induced events, it is important that we recognize the values of- fringing 

mangroves as nursery areas for commercial and recreational fishes and their food 

resources in order to predict impacts of alterations before they occur. Efforts 

need to be expended to evaluate this and more extensively flooded mangrave 

habitats for their relative value to fish and crustaceans. 
1 ACKNOWLEDGMENTS I 

I This study is part of a larger study on early life history of fish funded 

I through a cooperative agreement between the National Park service's Everglades 

National Park and the National Marine Fisheries Service, Southeast Fisheries 

Center, Beaufort Laboratory. Numerous individuals spent many hours discussing 

sampling approaches, collecting samples while swatting mosquitoes, and in 

analyzing the samples and data. Particular thanks are expressed to Michael 

LaCroix, Patti McElhaney, Keith Rittmaster, Don Field, Jud Kenworthy, and Dave I 

Peters of the Beaufort Laboratory and Jim Tilmant , Mike Robblee, Ed Rutherford 

)) and Peggy Harrigan of Everglades National Park. Herb Gordy drew the figures and 

Jeanie Fulford typed the paper. We also express our thanks to William Odum for 

comments and with whom we had discussions concerning approaches to sampling 

mangrove habitats, and Samuel Snedaker, and Armando de la Cruz and Michael 

Robblee for reviewing parts of the manuscripts. 
'LITERATURE CITED 

Adams, S.M. 1976. The ecology of eelgrass, Zostera marina (L.), fish 

communities. I. Structural analysis. J. Exp. Mar. Biol. Ecol. 22: 

269-291. 

Allen, D.M., J.H. Hudson, and T.J. Costello. 1980. Postlarval shrimp 

(~enaeus ) in the Florida Keys r Species, size, and seasonal abundance. 

Bull. Mar. Sci. 30: 21-33. 

American Society for Testing and Materials. 1963. Standard methods for 

particle size analysis of soils. A.S.T.M. designation 0422-63. American 

Society for Testing and Materials, Philadelphia, Pa. 

Beaufort Laboratory., 1987. Ichthyoplankton and juvenile fish studies in 

Everglades National Park: Executive Summary. Everglades National Park. 7 p. 

Bloom, S.A., S.L.,Santos and J.G. Field. 1977. A package of computer programs 

for benthic community analyses. Bull. Mar. Sci. 27:577-580. 

BMDP statistical software. 1983. University of California Press, Berkeley, 

733 p. 

Boesch, D.F., and R.E. Turner. 1984. Dependence of fishery species on salt 

marshes: The ple of food and refuge. Estuaries 7: 460-468. 

Carter, M.R., L.A. Burns, T.R. Cavinder, K.R. Duggen, P.C. Fore, D.B.. Hicks, 

H.L. Revelles, and T.W. Schmidt. 1973. Ecosystem analysis of the Big 

Cypress Swamp and estuaries. U.S. Environmental Protection Agency, 

Atlanta, Ga. 

Chester, A.J., R.L. Ferguson and G.W. Thayer. 1983. Environmental gradients 

and benthic macroinvertebrate distributions in a shallow North Carolina 

estuary. Bull. Mar. Sci. 33: 282-295. 

Colby, D.R., G.W. Thayer, W.F. Hettler, and D.S. Peters. 1985. A comparison 

of forage fish communities in relation to habitat parameters in Faka 

Union Bay, Florida and eight collateral bays during the wet season. 

NOAA Tech. Memo. NMFS-SEFC-162. 87 p. 

Eldred, 0.: R.M. Ingle, K. D. Woodburn, R.F. Wtton and H. Jones. 1961. 

Biological observations on the commercial shrimp, Penaeus duorarum 

Burkenroad, in Florida waters. Fla. Board Cons. 3: 1-139. 

Fonseca, M.S., and J.S. Fisher. 1986. A comparison of canopy friction and 

sediment movement between four species of seagrass with reference to their 

ecology and restoration. Mar. Ecol. Pror. Ser. 29:15-22. 

Fonseca, M.S., J.C. Zieman, G.W. Thayer and J.S. Fisher. 1983. The role of 

current velocity in structuring eelgrass (Zostera marina t . ) meadows. 

Est. Coast. Shelf Sci. 17: 367-380. 

Gauch, H.G., Jr. 1982. Multivariate analysis in community ecology. 

Cambridge University Press., New York. 298 p. 
I "'~sburg, R.N. 1956. Environmental relationships of grain size and 

constituent particles in some south Florida carbonate sediments. Bull. Am. 

Assoc. Petrol. Geol. 40: 2384-2427. 

Heald, E.J. 1969. The production of organic detritus in a south Florida 

estuary. Ph.0. thesis, University of Miami, Fla. 110 p. 

Heck, K.L., Jr., and R.J. Orth. 1980. Structural com~onents of eelaass a 

(~ostera marina) meadows in the lower Chesapeake 8'ay - decapod crustacea. 

Estuaries 3: 289-295. 

Hellier, T.R. 1962. Fish production and biomass studies in relation to phytosynthesis in the Laguna Madre of Texas. Publs. Inst. Mar. Sci. Univ. 

Texas. 8: 212-215. 

Hoese, H.D., and R.S. Jones. 1963. Seasonality of larger animals in a Texas 

grass community. Publs. Inst. Mar. Sci. Univ. Texas. 9: 37-46. 

Hudson, J.H.? D.M. Allen, and T.J. Costello. 1970. The flora and fauna of 

a basin In central Florida Bay. U.S. Fish Wildl. Serv. Spec. Sci. Rep. 

Fish. 604: 1-14. 

"-lworthy, W. J., J.C. Zieman, and G.W. Thayer. 1982. Evidence for the influence of seagrasses on the benthic nitrogen cycle in a coastal plain 

estuary near Beaufort, North Carolina (USA). Oecologia 54: 152-158. 

Kjelson, M.A.? and D.R. Colby. 1977. The evaluation and use of gear 

ef ficiencles in the estimation of estuarine fish abundance, p. 416-424. 

7 

In M.A. Wiley (ed. ), Estuarine Processes, Vol. 2. Academic Press, New York. 

Kjelson, M.A., and G.N. Johnson. 1978. Catch efficiencies of a 6.1-meter 

otter trawl for estuarine fish populations. Trans. Am. Fish Soc. 

107: 246-254. 

Lugo, A.E., and S.C. Snedaker. 1974. The ecology of mangroves. Annu. Rev. 

Eco~. Syst. 5: 39-64. 

Massman, W.H., E.C. Ladd, and H.N. McCurcheon. 1952. A surface trawl for 

sampling young fishes in tidal rivers. Trans. 17th N. Am. Wildl. Conf. 

386-392. 

McFarland, W.N., J.C. Ogden and V.N. Lythgoe. 1979. The influence of light 

on the twilight migration of grunts. Environ. Biol. Fishes. 4:9-22. 

Moody, W.D. 1950. A study of the natural history of the s~otted seatrout, 

~ynoscion nebulosus, in the Cedar Key, ~lorida area. Q'. J. Fla. Acad. ' 

Sci. 12: 147-171. 

Nixon, S. W., and C.4. Oviatt . 1972. Preliminary measurements of midsummer 

metabolism in beds of eelgrass, Zostera marina. Ecology 53: 150-153. 
Qdum, W.E. 1970. Pathways of energy flow .in a south Florida estuary. Ph.D. 

thesis, University of Miami, Fla. 162 p. 

Odum, W.E., and E.J. Heald. 1975. The detritus-based food web of an estuarine 

mangrove community, p. 265-286. In L.E. Cronin (ed. ) , Estuarine Research, 

Vol. 1. Academic Press, New ~orkr 

Odum, W.E., C.C. McIvor, and T. J. Smith, 111. 1982. The ecology of the 

mangroves of south Florida: A community profile. U.S. Fish Wildl. Serv., 

Biol. Serv. Prog. F~S/0BS-81/24. 144 p. 

Ogden, J.C. and J.C. Zieman. 1977. Ecological aspects of coral reef-seagrass 

bed contacts in the Caribbean. Proc. 3rd Int. Symp. Coral Reefs. Univ. 

Miami. Miami, FL. 32377-382. 

Orth, R.J., and K.A. Heck, Jr. 1980. Structural components of eelgrass 

(Zostera marina ) meadows in the lower Chesapeake Bay fishes. Estuaries 

3: 278-288. . 

Orth, R. J., K.L. Heck, Jr., and J. van Montfrans. 1984. Faunal communities 

in seagrass beds: A review of the influence of plant structure and 

prey characteristics on predator-prey relationships. Estuaries 7: 

339-350. 

Perret, W.S., J.F. Weaver, R.O. Williams, P.L. Johnson, T.D. McIlwain, R.C. 

Raulerson, and W.M. Tatum. 1980. Fishery profiles of red drum and spotted 

seatrout. Gulf States Marine Fisheries Commission. Pub. No. 6: 60 p. 

Powell, A.B., D.E. Hoss, W.F. Hettler, D.S. Peters, Larry Simoneaux, and 

Stephanie Wagner. 1987. Abundance and distribution of ichthyoplankton 

in Florida Bay and adjacent waters. South Florida Res. Cent. Report 

~~~C-87/01. 

Powell, G.V.N., .S.M. Sogard and J.G. Holmquist. 1986. Ecology of shallow water 

bank habitats in Florida Bay. Final Report to Everglades National Park, 

Contract No. CX5280-3-2339. 259 p. 

Robblee, M.B. and J.C. Zieman. 1984. Die1 variation in fish fauna of a 

tropical seagrass feeding ground. Bull. Mar. Sci. 34:335-345. 

Rutherford, E., E. Thue, and D. Duker. 1982. Population characteristics, 

food habits and spawning activity of spotted seatrout, Cynoscion nebulosus, 

in Everglades National Park, Florida. South Florida Res. Cent., Rept .- 

668-48 p. 

Rutherford, E.S., E.B. Thue, and D.G. Buker. 1983. Population structure, food 

habits, and spawning activity of gray snapper, Lutjanus griseus, in 

Everglades National Park. South Florida Res . Cent. Rept . ~~~C-82/02. 41 p . Schomer, N.S., and R.D. Drew. 1982. An ecological characterization of the 

lower Everglades, Florida Bay and the Florida Keys. U.S. Fish Wildl. 

sedv. Biol. Serv. Prog. FWS/OBS-82/58.1. 246 p. 

Schmidt, T.W. 1979. Ecological study of fishes and the water quality 

characteristics of Florida Bay, Everglades National Park, Florida. Everglades National Park, Final Project Report No. RSP-EVER-N-36. 145 p. 
Snapinn, S.M. and J.D. Knoke. 1984. Ciassificat ion error rate estimators 

evaluated by unconditional mean square error. Technometrics 26:371-378. 

Sogard, S. M. 1982. Feeding ecology, population structure, and community 

relationships of a grassbed fish, Callionymus pauciadiatus, in 

southern Florida. M.S. thesis, U. Miami, Coral Gables. 103 p. 

Sogard, S.M., G.V.N. Powell and J.G. Holmquist. In press. Epibenthic fish 

communities on Florida Bay banks: Relationships with seagrass cores and 

physical environment. Mar. Ecol. Prog. Ser. 

Starck, W.A., 11. 1971. Biology of the gray snapper, Lutjanus riseus 

(~inneaus ) , in the Florida Keys. Stud. Trop . Oceanogr . (Mi?mO. 

150 p. 

Starck, W.A., 11, and R.E. Schroeder. 1970. Investigations on the gray 

snapper, Lutjanus qriseus. Stud. Trop. Oceanogr. Miami 10: 224 p., 44 

figs . Stewart, K.W. 1961. Contributions to the biology of the spotted seatrout 

(Cynoscion nebulosus) in the Everglades National Park, Florida. M.S. 

Thesis, Univ. Miami, Coral Gables: 103 p. \ 

Stoner, A.W. 1980. The role of seagrass biomass in the organization of 

benthic macrofaunal assemblages. Bull. Mar. Sci. 30: 537-551, 

Stoner, A.W. 1982. The 

behavior of pinfish, 

Eco~. 58: 271-284. 

influence of benthic macrophytes on the 

Lagodon rhomboides (Linnaeus ) . J. Exp. 

foraging 

Mar. Biol. 

Stoner, A.W. 1983. Distribution ecology of amphipods and tanaidaceans 

associated with three seagrass species. J. Crust. Biol. 3: 505-518. 

Tabb, D.C., and D.L. Dubrow. 1962. The ecology of northern Florida Bay and 

adjacent estuaries: Part I - Aspects of the hydrology of northern Florida 

Bay and adjacent estuaries. Fla. Board Conserv. Mar. Res. Lab. Tech. 

Ser. 39: 6-38. 

Tabb, D.C., and R.B. Manning. 1961. A checklist of the flora and fauna of 

northern Florida Bay and adjacent brackish waters of the Florida mainland 

collected during the period July, 1957 through September, 1960. 

Bull. Mar. Sci. Gulf Caribb. 11: 552-649. 

Tabb, D.C., and R.B. Manning. 1962. The ecology of northern Florida Bay and 

adjacent estuaries: Part I1 - Aspects of the biology of northern Florida 

say and adjacent estuaries. Fla. Board Conserv. Mar. Res. Lab. Tech. 

Ser. 39: 39-79. 

Thayer, G.W., D.R. Colby, and W.F. Hettler. Jr. 1987. Utilization of 

the red mangrove prop root habitat by fishes in south Florida. Mar. Ecol. 

Prog. Ser. 35:25-38. 

L 
5 

Day-Night Comparisons 

Those species that dominated mangrove samples collected in daytime between June 

1984 and May 1985 (Table 29) also were the dominant species collected during 

both the day and niaht in September 1985 (Table 32). There was, however, a 

tendency for 0psanuE beta (gulf toadfish), Strongylura notata (redfin 

needlefish), and Menidiapeninsulae (tidewater silversiw be important 

components of the community sampled during the day-night phase .of the study. 

FOU~ species, Diapterus (striped-mjarra), 

(pigfish), Haemulon grunt), and -- 

were taken in the day-night sampling but had not been collected previously. All 

but the striped mojarra are considered recreational species, and all were 

collected at night; only the white grunt was collected during both day and night 

(Table 32). These data suggest that some recreational and/or commercial fish 

may move into the prop root habitat at night to either feed or rest, and that 

extensive night sampling might provide additional species of fish to our list of 

those frequenting mangrove habitats. 

t 

An examination of the data in Table 32 reveals that while fish densities tended 

to be higher during daylight, this was not invariably true, even for a given 

species. Similarly, the numbers of species in samples taken at night were 

greater than in those taken during the day in five of the six paired comparisons 

(Table 32); often these differences are the consequence of the addition of 

relatively uncommon species of higher trophic levels. Finally, Shannon-Weiner 

diversity indices computed for the twelve samples also fail to show a consistent 

relation to the two temporal periods; in four cases they were higher at night 

whereas in the other two comparisons they were higher for the daytime samples 

(Table 32). 

The binomial theorem provides a basis for testing the null hypothesis that a 

given species has an equal likelihood of being collected from the mangrove 

habitat during either the day or night. For example, if a species was taken on 

four different occasions, then the probability (under the null hypothesis) that 

all four samples were either night samples or were day samples is 0.125. To 

demonstrate a consistent day-night difference in a species use of the mangrove 

prop root habitat then, we would require a consistency extending over at least 

six independent observations, wherein the probability would be less than 0.05 

(actually it would be 0.0313 for six observations). We only had six paired 

observations from our samples, which is the minimum required number. Not one of 

the 34 species taken in the six pairs of samples demonstrated that level of 

consistency. The species that had the highest consistency with respect to being 

taken exclusively during either the day or the night was S h raena barracuda. 

It was taken only during the day and on three occasions (p=0.25 9 Although only 

suggestive, Floridichthys carpio was most frequently more abundant (5 our of 6 

collections) during the day as were Eucinostomus ar enteus (3 of 4 collections), 

Menidia peninsulae (2 of 2), and Strongylura timucu -3.- 2 of 3). Strongylura 

notata was collected only at night on four of five occasions; on the fifth 

occasion more were captured during the day than at night. Lutjanus griseus also 

was encountered more frequently at night in these trials. 

It should be apparent that the geographical differences in the fish communities 

of the mangrove prop-root habitat observed in the earlier sampling make our 

investigation of day-night differences in utilization of the habitat very 

conservative, because the test of the day-night hypothesis for a given species