U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2009-1145

Prepared in cooperation with the 

Florida Fish and Wildlife Conservation Commission

Composition of Age-0 Fish Assemblages in the Apalachicola 

River, River Styx, and Battle Bend, Florida

Prepared in cooperation with the

Florida Fish and Wildlife Conservation Commission 

Open File Report 2009–1145

U.S. Department of the Interior

U.S. Geological Survey

Composition of Age-0 Fish Assemblages 

in the Apalachicola River, River Styx, and 

Battle Bend, Florida

Stephen J. Walsh, Elissa N. Buttermore, O. Towns Burgess, and 

William E. Pine, III
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2009

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Suggested citation:

Walsh, S.J., Buttermore, E.N., Burgess, O.T., and Pine, W.E., III, 2009, Composition of Age-0 Fish Assemblages in the 

Apalachicola River, River Styx, and Battle Bend, Florida: U.S. Geological Survey Open-File Report 2009-1145, 28 p.

Detailed Geographic Information System (GIS) data for the St. Johns River Water Management District are available 

on the District’s spatial data web site (http://sjr.state.fl.us/gisdevelopment/docs/themes.html). Due to the way 

certain land-use codes were combined in this study, and differences in coding between years of available data, some 

differences exist between codes used for land-use and land-cover categories. For example, some of the percentages 

provided on figure 4 reflect a different overall pattern than would be evident from a broad landscape-scale area of 

coverage. Readers of this report and land-use and land-coverage data users are encouraged to utilize the original GIS 

sources for any in-depth applications requiring detailed spatial data.
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Study Area..............................................................................................................................................3

Methods...........................................................................................................................................................3

Results .............................................................................................................................................................7

Surface-Water Discharge ...................................................................................................................7

Age-0 Fish Assemblage Composition................................................................................................7

2006-2007 Sampling Period ........................................................................................................7

All Years.......................................................................................................................................17

Taxonomic Composition...................................................................................................17

Abundance and Dominance ...........................................................................................17

Chronological Appearance .............................................................................................18

Pre- and Post-Enhancement of Battle Bend..................................................................................21

Discussion.....................................................................................................................................................21

Acknowledgments.......................................................................................................................................25

References Cited..........................................................................................................................................26

Figures

1-2. Maps showing—

1. Apalachicola, Chattahoochee, and Flint River basin and Apalachicola 

River floodplain ....................................................................................................................4

2. Apalachicola River, River Styx, and associated sloughs ..............................................5

3. Photograph of the light trap used to collect age-0 fishes in the Apalachicola 

River and floodplain......................................................................................................................6

4-12. Graphs showing—

4. Annual discharge in the Apalachicola River at Blountstown during years of 

 age-0 fish sampling .............................................................................................................8

5. Mean monthly discharge in the Apalachicola River at Blountstown during 

years of age-0 fish sampling..............................................................................................9

6. Continuous discharge at the Blountstown gage and mean water temperature 

on light-trap sampling dates in the Apalachicola River and River Styx in 2006, 

and catch-per-unit effort by date for all age-0 fishes..................................................15

7. Continuous discharge at the Blountstown gage and mean water temperature 

on light-trap sampling dates in the Apalachicola River, River Styx, and Battle 

Bend in 2007, and catch-per-unit effort by date for all age-0 fishes.........................16

8. Species accumulation curve for all samples of age-0 fish collected in the 

Apalachicola River, River Styx, and Battle Bend for the years 2002-2007 ...............18

9. Percent composition by year of families representing greatest abundance of 

age-0 fishes collected by light trap in the Apalachicola River, River Styx, and 

Battle Bend .........................................................................................................................18

10. Mean catch-per-unit effort of most abundant age-0 fishes by family and all 

taxa in the Apalachicola River, River Styx, and Battle Bend by year........................19
iv

11. Mean catch-per-unit effort of dominant families and all taxa for combined 

years (2002-2007) of age-0 fish caught by light traps in the Apalachicola River 

and multiple floodplain water bodies by Julian date and month...............................20

12. Cumulative and partial ranked species abundance plots of age-0 fishes 

collected in Battle Bend in 2003 and 2007 .....................................................................22

 Tables

1. Light-trap collections of age-0 fishes made in the Apalachicola River and 

floodplain habitats, 2006-2007.....................................................................................................9

2. Number and percent composition by taxon of age-0 fishes collected by light 

traps in the Apalachicola River, River Styx, and Battle Bend in 2006-2007.................10-11

3. Summary by family for age-0 fishes collected by light trap in the Apalachicola 

River, 2003-2007...........................................................................................................................12

4. Summary by family for age-0 fishes collected by light trap in River Styx, 

2002-2007......................................................................................................................................13

5. Summary by family for age-0 fishes collected by light trap in Battle Bend, 

2002-2007......................................................................................................................................14

6. Number of traps, percent empty, and diversity metrics of samples combined 

by year of age-0 fishes taken by light traps in the Apalachicola River, River 

Styx, and Battle Bend from 2002-2007.....................................................................................17

7. Rank abundance by species of age-0 fishes collected in Battle Bend in 

2003 and 2007...............................................................................................................................23

 Conversion Factors

Multiply By To obtain

millimeter (mm) 0.03937 inch (in.)

centimeter (cm) 0.3937 inch (in.)

kilometer (km) 0.6214 mile (mi)

Acronyms and other abbreviations

C/f catch per unit effort

FPC Floodplain Pulse Concept

GPS global positioning system

PVC polyvinyl chloride

SE standard error

UF University of Florida

μm micrometer

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) 

as follows: °F = (1.8 × °C) + 32
Abstract

Light traps were used to sample the age-0 year class of 

fish communities in the Apalachicola River and associated 

floodplain water bodies of River Styx and Battle Bend, Florida, 

in 2006-2007. A total of 629 light traps were deployed during 

the spring and early summer months (341 between March 15 

and June 6, 2006; 288 between March 9 and July 3, 2007). For 

combined years, 13.8 percent of traps were empty and a total of 

20,813 age-0 fish were captured representing at least 40 taxa of 

29 genera and 16 families. Trap catches were dominated by relatively few species, with the most abundant groups represented 

by cyprinids, centrarchids, percids, and catostomids. Six taxa 

accounted for about 80 percent of all fish collected: Micropterus

spp. (28.9 percent), Notropis texanus (28.9 percent), Lepomis

macrochirus (7.9 percent), Carpiodes cyprinus (6.2 percent), 

Cyprinidae sp. (4.6 percent), and Minytrema melanops (4.2 

percent). Based on chronological appearance in light traps and 

catch-per-unit effort, including data from previous years of 

sampling, peak spawning periods for most species occurred 

between early March and mid-June. A complementary telemetry study of pre-reproductive adults of select target species 

(Micropterus spp., Lepomis spp., and M. melanops) revealed 

distinct patterns of habitat use, with some individual fish 

exclusively utilizing mainstem river habitat or floodplain habitat 

during spawning and post-spawning periods, and other individuals migrating between habitats. A comparison of light-trap 

catches between a pre-enhancement, high-water year (2003) 

and post-enhancement, low-water year (2007) for the oxbow at 

Battle Bend revealed some difference in community composition, with slightly greater values of diversity and evenness 

indices in 2007. Two dominant species, Lepomis macrochirus

and Micropterus salmoides, were substantially greater in 

relative abundance among all age-0 fish collected in 2007 in 

comparison to 2003. Excavation of sediments at the mouth 

of Battle Bend improved river-floodplain connectivity during 

low flows such as occurred in 2007 and likely provided greater 

access and availability of fish spawning and nursery habitats.

Introduction

Large rivers are extremely complex, dynamic, spatially 

and temporally variable ecosystems (Johnson and others, 

1995). The role of floodplains in the ecology of large rivers is 

extensively documented in the literature. The Floodplain Pulse 

Concept (FPC; Junk and others, 1989) is commonly used to 

explain large-river structure and function. The most important 

natural hydrologic feature of large floodplain rivers is considered to be the annual flood pulse, which extends a river onto 

its floodplain. The FPC emphasizes connectivity of the river 

channel and floodplain through annual flood pulses that influComposition of Age-0 Fish Assemblages in the 

Apalachicola River, River Styx, and Battle Bend, Florida

Stephen J. Walsh1, Elissa N. Buttermore2, O. Towns Burgess2, and William E. Pine III2

1U.S. Geological Survey, 7920 NW 71st St., Gainesville, FL 32653 (swalsh@usgs.gov)

2University of Florida, 7922 NW 71st St., Gainesville, FL, 32653
2 Composition of Age-0 Fish Assemblages in the Apalachicola River, River Styx, and Battle Bend, Florida

ence how physical and biological processes interact. The main 

tenet of the FPC is that floodplains are highly productive areas 

that provide critical habitats and energy sources required to 

sustain river communities (Bayley, 1995). Aquatic organisms 

exist in dynamic equilibrium with physical features of the 

annual cycle, especially the timing, duration, magnitude, and 

rate of rise and fall of water levels. Disruptions to the flood 

pulse may interfere with community or population dynamics 

by altering reproduction, survivorship, and trophic webs.

Tropical rivers have the largest floodplains and the best 

documented aquatic-terrestrial linkages (Welcomme, 1979, 

1985; Goulding, 1980; Lowe-McConnell, 1987). Rivers of the 

temperate zone are among the most substantially altered in the 

world, and have also received substantial study (Dodge, 1989; 

Bravard and others, 1992; Sparks and others, 1998; Galat 

and Zweimüller, 2001; Grift, 2001). Rivers with the most 

extensive forested floodplains in the United States are located 

primarily in the Midwest (Mississippi River basin), and in 

the southeastern Coastal Plain (Gulf of Mexico coast and 

Atlantic Slope). Floodplains of these systems are known to 

provide food, cover, spawning, and nursery habitats for fishes 

and other aquatic organisms during periods of inundation 

(Larson and others, 1981; Wharton and others, 1981, 1982; 

Crance, 1988; Leitman and others, 1991; Hackney and Adams, 

1992; Sparks, 1995; Galat and others, 1998; Light and others, 

1998; Matthews, 1998). Natural resource managers in the 

southeastern United States are concerned with how changes in 

water levels associated with regulated flows affect the ecology 

of floodplain-dependent aquatic communities. In particular, 

there is interest in determining how hydrologic alterations and 

reservoir release operations influence fish spawning, recruitment, survival, and sustainability.

The focus area of this study was the Apalachicola River, 

Florida―a large alluvial river of the southeastern Coastal 

Plain with an extensive forested floodplain (fig. 1). The 

Apalachicola River and its floodplain have been affected by 

changes in the landscape and decades of regulated flows, 

primarily as a result of increased urbanization and agriculture 

in Georgia. Adverse ecological effects stem from altered 

flows from upriver reservoir operations, changes in sediment 

transport, navigational dredging, spoil disposal, and geomorphic modifications to the channel. A major consequence of 

these changes is that conditions that normally govern riverfloodplain connectivity are compromised at low river flows. 

The floodplain is thought to provide important habitat to 

fishes and other aquatic organisms, yet few empirical data are 

available to document how physical and hydrologic changes 

have affected these biological communities. Light and others 

(1998) suggested that floodplain habitats may be used by 

as many as 80 percent (91 species) of freshwater fishes in 

the Apalachicola drainage. Based on other large floodplain 

rivers, it is likely that disconnection and prolonged isolation of floodplain habitats from the river channel interrupts 

natural processes that affect the ecology of many species. 

Such physical habitat changes may alter spawning, recruitment, movements, growth, and other aspects of the ecology 

of species that utilize the floodplain temporally and spatially. 

As demands for water resources continually increase in the 

Apalachicola-Chattahoochee-Flint basin, there is a growing 

need to assess floodplain utilization by fishes during spawning 

and nursery periods.

This investigation builds on previous studies of fish 

recruitment and habitat associations in the Apalachicola River 

and floodplain water bodies. The objectives of the study were 

the following:

1. To document spawning of fishes in the Apalachicola River 

mainstem and floodplain. Emphasis was to determine 

spatial and temporal peak distributions of larval fishes in 

the context of associating these patterns with hydrologic 

conditions and seasonal inundation of the floodplain.

2. To relate larval production and abundance with adult 

fish movement patterns and spawning among floodplain 

and main channel habitats. A corollary of this objective 

was to assess, to the extent possible, a habitat enhancement project that consisted of reconnecting the mouth of 

an artificial oxbow (Battle Bend) with the river channel 

during low-flow conditions. Due to scheduling of the 

habitat enhancement project, a natural floodplain system 

(River Styx) was used as a proxy during the first year of 

the study (2006) for evaluating adult movement patterns 

and determining peak abundances of larval fishes. Similar 

sampling was conducted in Battle Bend in 2007 following 

excavation of sand and debris at the mouth of the oxbow.

This study developed as a collaborative effort with 

investigators from the University of Florida (UF), and was 

designed to complement a simultaneous investigation of 

movement patterns of pre- and post-reproductive adults of 

four target fish species/guilds: black basses (Micropterus

spp.), particularly largemouth bass (M. salmoides), sunfishes 

(Lepomis spp.), particularly redear sunfish (L. microlophus), 

spotted sucker (Minytrema melanops), and channel catfish 

(Ictalurus punctatus). The movement study conducted by UF 

researchers consisted of tracking adult fishes that had been 

implanted with sonic or radio telemetry tags over the course 

of two spawning and post-spawning seasons in 2006-2007. 

The results of the tracking study in combination with selected 

components of this study are provided in a separate summary 

report (Pine and others, 2008). Concurrent with the tracking 

study, larval fish communities were sampled to explore for 

possible correlates between movement patterns of adult 

fishes and the appearance, peak timing, and abundance of 

age-zero (herein, “age-0”) cohorts of the target species. As 

a consequence of sampling for the target species, data were 

obtained on the entire community of age-0 fishes within the 

study area. This report summarizes community data for the 

concurrent telemetry/larval recruitment investigation, as well 

as retrospective (2002-2004) community data for the study 

area, including chronological appearance and peak abundance 

of age-0 cohorts.
Methods 3

Study Area

The Apalachicola River is formed by the confluence of 

the Chattahoochee and Flint rivers at the borders of Florida, 

Georgia, and Alabama; collectively, the system is referred to 

as the Apalachicola-Chattahoochee-Flint basin (fig. 1). The 

Apalachicola River is the largest river that discharges into 

the coastal waters of Florida (Nordlie, 1990). Large annual 

fluctuations in flow of the Apalachicola River dictate the 

character and function of the forested floodplain system (Elder 

and others, 1988). The river forms a vast meandering and 

braided system with an extensive network of tributaries and 

distributaries that extend laterally onto the forested floodplain, 

especially in the middle and lower reaches. Light and others 

(1998) summarized the historical, physical, and biological data 

for the Apalachicola River floodplain, and characterized the 

diverse aquatic habitats and connectivity between the main 

channel and floodplain under different flow conditions. Light 

and others (2006) summarized the extent of habitat modifications as a function of channel morphology changes and 

water-level declines since construction of Jim Woodruff Lock 

and Dam at the Florida-Georgia border. Livingston (2008) 

provided a general overview of environmental and ecological 

issues pertaining to the Apalachicola River.

The study area is in the non-tidal lower reach of the 

Apalachicola River as described by Light and others (1998), 

in the region around Battle Bend and River Styx. Battle Bend 

is an oxbow lake on the eastern shoreline of the Apalachicola 

River near river mile 28.5 (river kilometer 45.9) that was 

formed as a backwater habitat in 1969 when the U.S. Army 

Corps of Engineers excavated a cut to bypass a meander in 

the river. Subsequent to its formation as a backwater lake, the 

mouth of Battle Bend became filled with sand and debris, and 

was disconnected during low flows. In 2006, the Florida Fish 

and Wildlife Conservation Commission contracted a project 

to remove depositional sediments to restore connectivity of 

the former river channel to the current river channel during 

low flows.

River Styx is a large tributary system that flows into the 

Apalachicola River near river mile 35.5 (river kilometer 56.9). 

A series of perennial to intermittently flowing streams connect 

the Apalachicola River and River Styx depending on flows in 

the main channel (fig. 2). The largest of these are Swift Slough 

and Moccasin Slough; the smaller connecting streams are 

Hog, Grayson, and Everett Sloughs. Information on depths, 

elevations, and connecting flows was provided by Light and 

others (1998). River Styx was selected as an unaltered control 

site for larval fish recruitment and adult fish movement studies 

in 2006-2007 for comparison to post-enhancement sampling in 

Battle Bend. 

During 2006, light traps were set throughout River Styx 

and in the Apalachicola River at various sites between river 

miles 35.0 and 40.5, downstream of the mouth of River Styx 

(30.08590°N, 85.13700°W) to just upstream of the head of 

Swift Slough (30.12146°N, 85.13144°W). In 2007, light trap 

collections were made in the same areas of River Styx and 

the surrounding mainstem channel as in 2006. In addition, 

collections were made in 2007 throughout the Battle Bend 

oxbow and in the river channel between river miles 28.5 and 

29.0, downstream of the mouth of Battle Bend (30.01396°N, 

85.09751°W) to near the upstream segment of the former river 

channel (30.01992°N, 85.10279°W).

Methods

Light traps are efficient for collecting small fishes in 

a broad range of habitats (Doherty, 1987; Secor and others, 

1992; Kissick, 1993; Ponton, 1994; Knight and Bain, 1996; 

Hernandez and Lindquist, 1999; Hickford and Schiel, 

1999). Niles and Hartman (2007) determined that light traps 

were more effective than benthic sleds or activity traps for 

determining species presence and relative abundance in a 

navigable river. A custom-designed floating light trap based on 

a modification of the quatrefoil trap described by Floyd and 

others (1984) and Kissick (1993) was used to collect larval, 

postlarval, and juvenile fishes (fig. 3). The top and base of 

each trap consisted of flat, opaque polyvinyl chloride (PVC) 

panels (30 cm × 30 cm × 6.4 mm thick). Sides (funnels) of 

the trap consisted of eight clear, flat plexiglass panels (15 cm 

wide × 30 cm high) mounted diagonally from the trap corners 

with ~5 mm vertical slots through which fish could pass. 

Traps were soaked for a minimum of 12 hours between about 

1800-0800 ± 4 hours using a battery-operated submersible 

light. Each night of light-trap sampling consisted of deploying 

a series of 8 to 18 traps, divided about evenly between sites 

in the river and the floodplain. Fish and invertebrates were 

retrieved using a collection bag (350-μm mesh) affixed to an 

open PVC ring at the trap bottom. The contents of each trap 

were fixed in 4-percent buffered formalin (Lavenberg and 

others, 1984) and returned to the laboratory.

In the laboratory, specimens were transferred through 

solutions of 30- and 50-percent ethanol, with final storage in 

70-percent ethanol. Larval and postlarval fish were separated 

from other aquatic organisms and identified to the lowest 

practicable taxonomic category. Sources used as aids in taxonomic identifications were Lippson and Moran (1974), Hogue 

and others (1976), Hardy (1978), Jones and others (1978), 

Auer (1982), McGowan (1984), Conrow and Zale (1985), 

Scheidegger (1990), Wallus and others (1990), Kay and others 

(1994), and Simon and Wallus (2003, 2006a,b). The total 

length (TL, in millimeters) of each fish was measured with 

an ocular micrometer or ruler, or a random subsample of 30 

specimens was measured when the number of individuals of 

the same taxon from a single trap exceeded that count.

Geographic coordinates were recorded with a geographic 

positioning system (GPS) for each trap location, and the 

following physicochemical properties were measured when 

each trap was set and again when retrieved: water depth, 

Secchi depth, temperature, dissolved oxygen, pH, specific 

conductance, and turbidity. 
4 Composition of Age-0 Fish Assemblages in the Apalachicola River, River Styx, and Battle Bend, Florida

FLORIDA

SC

Location of the

Apalachicola,

Chattahoochee, and

Flint River Basin

ALA

GA

A p a l a c h i c o l a B a y

Base from U.S. Geological Survey digital data, 1972

Albers Equal-Area Conic projection

Standard Parallels 29°30 ́ and 45°30 ́, central meridian -83°00 ́

30°00’

30°15’

30°30’

30°45’

85°15’ 85°00’ 84°45’

29°45’

85° 84° 83° 86° 35°

34°

33°

32°

31°

30°

29°

0

50 MILES

50 KILOMETERS

0

Base from U.S. Geological Survey digital data, 1972

Albers Equal-Area Conic projection

Standard Parallels 29°30 ́ and 45°30 ́, central meridian -83°00 ́

Chattahoochee

Sumatra

20

30

40

50

90

100

Wewahitchka

FLORIDA GEORGIA

Jim Woodruff Dam

Lake Seminole

Lower

Chipola

River

60

70

Bristol

80

Blountstown

Chipola River

10

0

Apalachicola

Brothers

River

Gulf of Mexico

Columbus

Albany

Atlanta

ALABAMA

GEORGIA

GEORGIA

ALA

FLORIDA

FLA

SC

River

Chattahoochee

Lake

Seminole

Lake

Sidney

Lanier

A a pal chicola

Chipola

River

Apalachicola

Bay

River

Ch

i

attahoochee R ver Flint River

Tallahassee

Gulf of Mexico

Apalac

r

h

e ic

v

ol Ri a

River Styx

Battle Bend

0

0

5

5

10

10 15 MILES

15 KILOMETERS

Drainage basin for

the Apalachicola,

Chattahoochee,

and Flint Rivers

Location of

Inset Map

EXPLANATION

APALACHICOLA RIVER

FLOODPLAIN

RIVER MILE—Number is

distance from mouth in

miles

60

Inset Map

Blountstown

Gage

Figure 1. Apalachicola, Chattahoochee, and Flint River basin (left) and Apalachicola River floodplain (right).
Methods 5

Gra

n

yso

Slough

Everett Slough

Everett S

ol ugh

Swift Slough

H

Sl

og

ough

Moc

n

casi

Slough

River

Styx

River Styx

Apalachicola River

Ap

alachicola River

Chipola C

f

utof

30°08’ 30°06’

85°08’

85°06’

85°04’

Base from U.S. Geological Survey digital data, 1972

Albers Equal-Area Conic projection

Standard Parallels 29° 30’ and 45°30’, central meridian -83°00’

APALACHICOLA RIVER

FLOODPLAIN

EXPLANATION

0

0

5,000 FEET

1,200 METERS

Florida

River

Figure 2. Apalachicola River, River Styx, and associated sloughs.
6 Composition of Age-0 Fish Assemblages in the Apalachicola River, River Styx, and Battle Bend, Florida

Light traps were deployed weekly from March 15 to 

June 6, 2006, in the Apalachicola River channel and River 

Styx, and biweekly from March 9 to July 3, 2007, in these 

two systems plus Battle Bend. River Styx was selected 

as a proxy floodplain system for sampling in 2006 due to 

delays in habitat enhancement (channel-mouth dredging) 

of the Battle Bend oxbow. The River Styx and Battle Bend 

sites are referred to herein as the “floodplain,” whereas the 

Apalachicola River is referred to as the “river channel” or 

“mainstem.” Light trapping of age-0 fishes similar to that 

conducted in this study was previously done in various areas 

of the Apalachicola River and floodplain during the years 

2002-2004 to document temporal and spatial occurrence 

of spawning (Walsh and others, 2006). The previous work 

included sampling in River Styx and Battle Bend, and those 

data are included herein for selected comparisons with data 

obtained in this study.

Kwak and Peterson (2007) recommend providing 

specific equations used in reporting community indices of 

species diversity, evenness, and dominance, because there 

are many variants and occasional inconsistent use of terminology. The Shannon-Wiener index (H′), a Type I index 

sensitive to the abundances of rare species in a community 

(Shannon and Weaver, 1949; Krebs, 1999), was calculated 

using the logarithmic base e as:

, (1)

where

s is number of species,

pi is proportion of the total sample represented by the 

ith species.

Based on the Shannon-Wiener index of diversity, 

evenness (Pielou, 1966), a measure of equitability in relative 

abundance among taxa, was calculated as:

, (2)

where

H′max is loge s = maximum possible diversity.

Simpson’s index of diversity (1 – Dˆ ), a Type II index 

that is influenced to a greater extent by abundant species 

(Simpson, 1949; Clarke and Warwick, 2001; Kwak and Peterson, 2007), was calculated as:

, (3)

where

ni is number of individuals of species i in the sample,

N is total number of individuals in the sample = ∑ i n ,

s is number of species in the sample.

Bray-Curtis similarity (1-B) (Bray and Curtis, 1957) was 

calculated as:

, (4)

where

B is Bray-Curtis measure of dissimilarity,

Xij, Xi k are number of individuals in species i in each

 sample (j, k),

n is number of species in samples.

Diversity metrics were computed with Primer-E© (ver. 6.1.6) 

software (Clarke and Warwick, 2001; Clarke and Gorley, 

2006) on raw numbers of fishes collected by year in each 

water body. Relative abundance (percent composition) data 

were upward collapsed by distributing numbers of fish identified only to genus or family level to those identified to species 

in their relative proportions based on site and year, with a 

few exceptions (cyprinids and Lepomis sp. were considered 

to be unique taxa from others identified to species). Diversity 

indices were assumed to under-represent age-0 assemblages 

due to phototaxic response differences among individual 

species and because some species exhibit a negative or no 

behavioral response to light.

Figure 3. Light trap used to collect 

age-0 fishes in the Apalachicola 

River and floodplain. Luminescent 

chemical sticks were used in 2002-

2004; a battery-operated white light 

was used in 2006-2007.

( )( ) e i

s

i

H' pi log p 1

∑=

= −

max '

' ' HH J =

∑=





 





−

− − = −

s

i

i i

N N

n n D 1 ( 1)( 1) 1 ˆ 1

 

1

 

1

( )

n

i j i k

i

n

i j i k

i

X X

B

X X

=

=

−

=

+

∑

∑
Results 7

Catch-per-unit effort (C/f) is reported as numbers of fish 

per trap (or means among traps per sampling event), because 

trap collections were considered to represent approximately 

the same effort; that is, dusk-to-dawn sampling periods of 

similar duration.

Results

Surface-Water Discharge

Discharge data were obtained from the National Water 

Information System (http://waterdata.usgs.gov/fl/nwis/rt/) for a 

gage on the Apalachicola River near Blountstown, operated by 

the U.S. Army Corps of Engineers. Discharge in the Apalachicola 

River during 2002-2007 was highly variable (fig. 4). Except for 

2003, mean monthly discharge during the peak periods of lighttrap sampling (March-June) were below average for the period 

of record (fig. 5); 2002 and 2006-2007 experienced substantial 

drought conditions throughout late spring, summer, and early fall 

months. Because no light trapping was conducted during 2005, 

hydrologic data for that year were omitted.

Age-0 Fish Assemblage Composition

2006-2007 Sampling Period

A total of 629 light traps were deployed in the 

Apalachicola River, River Styx, and Battle Bend during spring 

and early summer months between March 15, 2006, and July 

3, 2007 (table 1). Of these, 87 (13.8 percent) were empty. 

During both years, the number of empty traps was much 

greater in the river channel than in floodplain water bodies. 

For samples pooled by water body and year, the following 

percentages of traps were empty: Apalachicola River, 20.7 

percent (2006; n = 169) and 19.4 percent (2007; n = 144); 

River Styx, 5.2 percent (2006; n = 172) and 9.7 percent (2007; 

n = 72), and; Battle Bend, 11.1 percent (2007; n = 72).

A total of 20,813 fish were collected by light traps during 

this time period—12,560 in the Apalachicola River and River 

Styx in 2006, and 8,253 in the Apalachicola River, River Styx, 

and Battle Bend in 2007 (table 1). Nearly all specimens were 

age-0 fish, although a few subadult and adult specimens of 

slim-bodied species were also collected (mainly cyprinids, 

Labidesthes sicculus, and Anchoa mitchilli); regardless of size, 

all specimens collected in light-trap samples were included 

in summaries and analyses presented here. Samples for each 

water body and year were binomially distributed, because 

few traps contained large catches and many traps contained 

small catches. Two traps, in particular, skewed samples for 

each year: 695 yolk-sac and post-yolk sac larvae of Carpiodes

cyprinus were captured in a single trap placed downstream 

of a sandbar in the Apalachicola River on March 3, 2006, 

and 4,012 postlarval Micropterus (presumably a single clutch 

of M. salmoides) were captured in a single trap placed in an 

upstream section of River Styx on April 9, 2007.

Excluding specimens identified only to family level and 

Micropterus sp. (assignable to either M. salmoides or M. punctulatus), about 40 distinct taxa representing at least 29 genera and 

16 families were collected by light traps in 2006-2007 (table 2). 

Unidentified cyprinids likely included one or more additional 

species, especially in collections from the river channel, and 

were thus treated as a single taxon in the computation of 

diversity metrics and other analyses. Lepomis sp. were counted 

as distinct because most or all probably represented L. punctatus

or L. microlophus, and the larvae of neither species could be 

definitively identified. Six taxa individually comprised greater 

than 5 percent of the total composition of light-trap catches for 

2006-2007: Notropis texanus (28.9 percent), Micropterus spp. 

(28.9 percent, which includes both M. salmoides and a few 

specimens provisionally identified as M. punctulatus), Lepomis

macrochirus (7.9 percent), Carpiodes cyprinus (6.2 percent), 

Cyprinidae sp. (4.6 percent), and Minytrema melanops (4.2 

percent). Three taxa, based on small numbers, were collected in 

the Apalachicola River channel but not taken in the floodplain 

water bodies: Anquilla rostrata (n = 1), Strongylura marina

(n = 3) and Opsopoeodus emiliae (n = 6). Conversely, based on 

small numbers, eight taxa were collected in the floodplain but 

not from the river channel: Lepisosteus osseus (n = 3), Cyprinus 

carpio (n = 69), Notropis chalybeus (n = 3), N. maculatus (n = 4), 

Ictalurus punctatus (n = 4), Erimyzon sucetta (n = 3), Fundulus sp. 

(n = 2), and Elassoma okefenokee (n = 2). For all age-0 fish 

collected in 2006-2007, species of four families dominated 

samples in percent composition and catch-per-unit effort (C/f, 

the mean number of fish per trap for the total sampling period): 

centrarchids (38 percent; 12.7 C/f), cyprinids (37 percent; 

12.3 C/f), catostomids (11 percent; 3.7 C/f), and percids 

(7 percent; 2.4 C/f). The high relative abundance of centrarchids 

was due in part to the aforementioned single-trap catch of a 

large number of Micropterus sp. in River Styx in 2007, and for 

cyprinids due to the large numbers of Notropis texanus taken 

in the River Styx in 2006 and a large number of unidentified 

cyprinids taken in the river channel in 2006. Tables 3-5 provide 

relative abundances by family and summaries for all years of 

effort in the Apalachicola River channel (throughout a more 

extensive portion of the middle reach, as described in Walsh and 

others, 2006), and for River Styx and Battle Bend.

Traps placed in River Styx captured greater numbers of individuals than the other two sites (tables 3-5). For the 2006-2007 

study period, catch-per-unit effort was lowest in the Apalachicola 

River and intermediate in Battle Bend. For the following water 

bodies and years shown, the mean numbers of all fish (C/f ± 

1SE) were: Apalachicola River, 22.3 ± 5.7 (2006) and 7.0 ± 1.4 

(2007); River Styx, 51.1 ± 7.3 (2006) and 76.4 ± 55.5 (2007); and 

Battle Bend, 24.3 ± 3.7 (2007). In 2006, catch rates decreased 

over time with decreasing discharge and increasing water 

temperature, although a few weekly samples from March to May 

had low catch rates in comparison to preceding or subsequent 

weeks (fig. 6). Such a trend was not evident for 2007 based on 

non-transformed data, in part because traps were set biweekly and 

catch rates were much lower than in 2006 (fig. 7).
8 Composition of Age-0 Fish Assemblages in the Apalachicola River, River Styx, and Battle Bend, Florida

J F M A M J J A S O N D J F M A M J J A S O N D

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

J

2002 2003 2004

F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

MEAN DAILY DISCHARGE, IN CUBIC FEET PER SECOND

2006 2007

MEAN DAILY DISCHARGE, IN CUBIC FEET PER SECOND

Figure 4. Annual discharge in the Apalachicola River at Blountstown during years of age-0 fish sampling.
Results 9

JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPT. OCT. NOV. DEC. 5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

45,000

50,000

55,000

60,000

2002

2003

2004

2006

2007

1928-2007

MEAN MONTHLY DISCHARGE, IN CUBIC FEET PER SECOND

Figure 5. Mean monthly discharge in the Apalachicola River at Blountstown during years of age-0 fish 

sampling.

Table 1. Light-trap collections of age-0 fishes made in the Apalachicola River and floodplain habitats, 2006-2007.

Data category

2006 2007

Apalachicola 

River

River

Styx

Apalachicola 

River

River

Styx

Battle

Bend

Dates sampled 15 March-6 June 15 March-6 June 9 March-3 July 9 March-3 July 10 March-2 July

Total number of traps 169 172 144 72 72

Number of empty traps 35 9 28 7 8

Percent empty traps 20.7 5.2 19.4 9.7 11.1

Total number of fish 3,763 8,797 1,005 5,497 1,751
10 Composition of Age-0 Fish Assemblages in the Apalachicola River, River Styx, and Battle Bend, Florida Table 2. Number and percent composition by taxon of age-0 fishes collected by light traps in the Apalachicola River, River Styx, and Battle Bend in 2006-2007. [LPIL, lowest practicable identification level; n, number of specimens; %, percent composition by year; families arranged in approximate ascending phylogenetic sequence and species listed alphabetically within each family] Family Taxon Apalachicola River River Styx Battle Bend All sites 2006 2007 2006 2007 2007 2006 2007 2006-2007

n % n % n % n % n % n % n % n %

Lepisosteidae Lepisosteus oculatus 2 0.05 3 0.30 2 0.02 4 0.03 3 0.04 7 0.03

Lepisosteus osseus 3 0.03 3 0.02 3 0.01

Anguillidae Anguilla rostrata 1 0.10 1 0.01 1 <0.01Engraulidae Anchoa mitchilli 56 5.57 3 0.05 59 0.71 59 0.28Clupeidae Clupeidae LPIL 4 0.11 1 0.01 1 0.06 5 0.04 1 0.01 6 0.03

Dorosoma cepedianum 1 0.03 3 0.03 1 0.06 4 0.03 1 0.01 5 0.02Dorosoma petenense 2 0.05 40 3.98 6 0.07 16 0.29 108 6.17 8 0.06 164 1.99 172 0.83

Cyprinidae Cyprinidae LPIL 784 20.83 16 1.59 137 1.56 21 0.38 8 0.46 921 7.33 45 0.55 966 4.64

Cyprinella venusta 10 0.27 131 13.03 5 0.06 14 0.25 77 4.40 15 0.12 222 2.69 237 1.14Cyprinus carpio 2 0.02 67 3.83 2 0.02 67 0.81 69 0.33Notemigonus crysoleucas 3 0.08 1 0.10 312 3.55 42 0.76 93 5.31 315 2.51 136 1.65 451 2.17Notropis chalybaeus 3 0.03 3 0.02 3 0.01Notropis maculatus 4 0.23 4 0.05 4 0.02Notropis texanus 696 18.50 123 12.24 3,985 45.30 528 9.61 686 39.18 4,681 37.27 1,337 16.20 6,018 28.91Opsopoeodus emiliae 6 0.16 6 0.05 6 0.03

Catostomidae Catostomidae LPIL 1 0.03 3 0.30 5 0.09 11 0.63 1 0.01 19 0.23 20 0.10

Carpiodes cyprinus 1,156 30.72 20 1.99 6 0.07 2 0.04 107 6.11 1,162 9.25 129 1.56 1,291 6.20Erimyzon sucetta 2 0.02 1 0.02 2 0.02 1 0.01 3 0.01Minytrema melanops 424 11.27 125 12.44 283 3.22 31 0.56 3 0.17 707 5.63 159 1.93 866 4.16Moxostoma sp. 133 3.53 3 0.30 4 0.05 1 0.02 137 1.09 4 0.05 141 0.68

Ictaluridae Ictalurus punctatus 2 0.02 2 0.04 2 0.02 2 0.02 4 0.02

Noturus gyrinus 1 0.10 1 0.01 1 0.01 1 0.01 2 0.01Noturus leptacanthus 11 0.29 9 0.90 9 0.10 4 0.07 1 0.06 20 0.16 14 0.17 34 0.16

Aphredoderidae Aphredoderus sayanus 14 0.37 2 0.20 405 4.60 3 0.05 419 3.34 5 0.06 424 2.04Atherinopsidae Labidesthes sicculus 6 0.16 12 1.19 157 1.78 99 1.80 33 1.88 163 1.30 144 1.74 307 1.48Belonidae Strongylura marina 2 0.05 1 0.10 2 0.02 1 0.01 3 0.01
Results 11

Family Taxon

Apalachicola River River Styx Battle Bend All sites

2006 2007 2006 2007 2007 2006 2007 2006-2007

n % n % n % n % n % n % n % n %

Fundulidae Fundulus sp. 1 0.01 1 0.06 1 0.01 1 0.01 2 0.01Poeciliidae Gambusia holbrooki 1 0.03 7 0.70 28 0.32 4 0.07 17 0.97 29 0.23 28 0.34 57 0.27

Heterandria formosa 1 0.10 1 0.01 1 0.02 1 0.06 1 0.01 3 0.04 4 0.02

Centrarchidae Lepomis auritus 1 0.03 85 8.46 17 0.19 22 1.26 18 0.14 107 1.30 125 0.60

Lepomis gulosus 1 0.03 1 0.10 67 0.76 10 0.18 1 0.06 68 0.54 12 0.15 80 0.38Lepomis macrochirus 42 1.12 29 2.89 718 8.16 575 10.46 291 16.62 760 6.05 895 10.84 1,655 7.95Lepomis sp. 20 1.99 4 0.05 11 0.20 2 0.11 4 0.03 33 0.40 37 0.18Micropterus punctulatus 5 0.13 17 0.19 22 0.18 22 0.11Micropterus salmoides 76 2.02 11 1.09 429 4.88 14 0.25 89 5.08 505 4.02 114 1.38 619 2.97Micropterus sp. 74 1.97 184 18.31 952 10.82 4,047 73.62 114 6.51 1,026 8.17 4,345 52.65 5,371 25.81Pomoxis nigromaculatus 3 0.08 99 1.13 1 0.02 1 0.06 102 0.81 2 0.02 104 0.50

Percidae Percidae LPIL 16 0.43 2 0.20 264 3.00 280 2.23 2 0.02 282 1.35

Ammocrypta bifascia 1 0.03 2 0.20 1 0.02 1 0.01 3 0.04 4 0.02Etheostoma fusiforme 53 1.41 35 3.48 273 3.10 17 0.31 4 0.23 326 2.60 56 0.68 382 1.84Etheostoma swaini 120 3.19 8 0.80 464 5.27 35 0.64 3 0.17 584 4.65 46 0.56 630 3.03Percina nigrofasciata 71 1.89 49 4.88 105 1.19 2 0.04 176 1.40 51 0.62 227 1.09

Elassomatidae Elassoma okefenokee 2 0.02 2 0.02 2 0.01

Elassoma zonatum 24 0.64 28 0.32 2 0.11 52 0.41 2 0.02 54 0.26

Achiridae Trinectes maculatus 20 0.53 24 2.39 7 0.13 3 0.17 20 0.16 34 0.41 54 0.26Total 3,763 1,005 8,797 5,497 1,751 12,560 8,253 20,813

Table 2. Number and percent composition by taxon of age-0 fishes collected by light traps in the Apalachicola River, River Styx, and Battle Bend in 2006-2007.—Continued[LPIL, lowest practicable identification level; n, number of specimens; %, percent composition by year; families arranged in approximate ascending phylogenetic sequence and species listed alphabetically within each family]
12 Composition of Age-0 Fish Assemblages in the Apalachicola River, River Styx, and Battle Bend, Florida Table 3. Summary by family for age-0 fishes1 collected by light trap in the Apalachicola River, 2003-2007. 

[C/f, catch-per-unit effort (mean number of fish per trap); n, number of specimens; %, percent composition by year; families arranged in approximate ascending phylogenetic sequence and species listed alphabetically within each family]

Family 2003 2004 2006 2007 All years

n %

C/f n %

C/f n %

C/f n %

C/f n %

C/f

Lepisosteidae 5 0.08 0.05 2 0.05 0.01 3 0.30 0.02 10 0.09 0.02Anguillidae 1 0.10 0.01 1 0.01 <0.01Engraulidae 12 0.20 0.11 56 5.57 0.39 68 0.64 0.16Clupeidae 441 7.46 3.97 7 0.19 0.04 40 3.98 0.28 488 4.56 1.15Cyprinidae 1 4.54 0.50 3,682 62.28 33.17 1,499 39.84 8.87 271 26.97 1.88 5,453 50.95 12.80Catostomidae 742 12.55 6.68 1,714 45.55 10.14 151 15.02 1.05 2,607 24.36 6.12Ictaluridae 8 0.14 0.07 11 0.29 0.07 10 1.00 0.07 29 0.27 0.07Aphredoderidae 1 0.02 0.01 14 0.37 0.08 2 0.20 0.01 17 0.16 0.04Atherinopsidae 4 18.18 2.00 29 0.49 0.26 6 0.16 0.04 12 1.19 0.08 51 0.48 0.12Belonidae 2 0.03 0.02 2 0.05 0.01 1 0.10 0.01 5 0.05 0.01Fundulidae 1 0.02 0.01 1 0.01 <0.01Poeciliidae 6 0.10 0.05 1 0.03 0.01 8 0.80 0.06 15 0.14 0.04Centrarchidae 17 77.27 8.50 777 13.14 7.00 202 5.37 1.20 330 32.84 2.29 1,326 12.39 3.11Percidae 203 3.43 1.83 261 6.94 1.54 96 9.55 0.67 560 5.23 1.31Elassomatidae 24 0.64 0.14 24 0.22 0.06Achiridae 3 0.05 0.03 20 0.53 0.12 24 2.39 0.17 47 0.44 0.11Total n 22 5,912 3,763 1,005 10,702Number of traps 2 111 169 144 426Number of empty traps 0 6 35 28 69Percent empty traps 0 5.4 20.7 19.4 16.2Total C/f 11.00 53.26 22.27 6.98 25.12

1Subadults and adults of relatively few specimens of slim-bodied taxa included (for example, engraulids, cyprinids, atherinopsids).
Results 13

Table 4. Summary by family for age-0 fishes1 collected by light trap in River Styx, 2002-2007. [C/f, catch-per-unit effort (mean number of fish per trap); n, number of specimens; %, percent composition by year; families arranged in approximate ascending phylogenetic sequence and species listed alphabetically within each family]

Family 2002 2003 2004 2006 2007 All years

n % C/f n % C/f n % C/f n % C/f n % C/f n % C/f

Lepisosteidae 4 0.04 0.04 1 0.09 0.06 5 0.06 0.03 10 0.04 0.02AnguillidaeEngraulidae 5 0.45 0.28 3 0.05 0.04 8 0.03 0.02Clupeidae 9 0.09 0.09 16 1.45 0.89 10 0.11 0.06 16 0.29 0.22 51 0.20 0.12Cyprinidae 76 27.44 1.38 7,778 78.30 76.25 284 25.82 15.78 4,444 50.52 25.84 605 11.01 8.40 13,187 51.50 31.47Catostomidae 63 0.63 0.62 6 0.55 0.33 295 3.35 1.72 40 0.73 0.56 404 1.58 0.96Ictaluridae 2 0.72 0.04 3 0.03 0.03 3 0.27 0.17 12 0.14 0.07 6 0.11 0.08 26 0.10 0.06Aphredoderidae 79 0.80 0.77 405 4.60 2.35 3 0.05 0.04 487 1.90 1.16Atherinopsidae 15 5.42 0.27 68 0.68 0.67 23 2.09 1.28 157 1.78 0.91 99 1.80 1.38 362 1.41 0.86Fundulidae 1 0.01 0.01 1 0.00 0.00Poeciliidae 2 0.72 0.04 64 0.64 0.63 1 0.09 0.06 29 0.33 0.17 5 0.09 0.07 101 0.39 0.24Centrarchidae 179 64.62 3.25 706 7.11 6.92 728 66.18 40.44 2,303 26.18 13.39 4,658 84.74 64.69 8,574 33.49 20.46Percidae 781 7.86 7.66 33 3.00 1.83 1,106 12.57 6.43 55 1.00 0.76 1,975 7.71 4.71Elassomatidae 1 0.36 0.02 371 3.73 3.64 30 0.34 0.17 402 1.57 0.96Achiridae 2 0.72 0.04 8 0.08 0.08 7 0.13 0.10 17 0.07 0.04Total n 2277 9,934 1,100 8,797 5,497 25,605Number of traps 55 102 18 172 72 419Number of empty traps 27 15 1 9 7 59Percent empty traps 49.1 14.7 5.6 5.2 9.7 14.1Total C/f 5.04 97.39 61.11 51.15 76.35 61.11

1Subadults and adults of relatively few specimens of slim-bodied taxa included (for example, engraulids, cyprinids, atherinopsids).2Low catch rate attributable to large number of empty traps retrieved in February, May, and October (58 percent empty; n = 43; remaining 12 traps all set in July) and overall low richness (11 or fewer taxa). 
14 Composition of Age-0 Fish Assemblages in the Apalachicola River, River Styx, and Battle Bend, Florida Table 5. Summary by family for age-0 fishes1 collected by light trap in Battle Bend, 2002-2007. 

[C/f, catch-per-unit effort (mean number of fish per trap); n, number of specimens; %, percent composition by year; families arranged in approximate ascending phylogenetic sequence and species listed alphabetically within each family]

Family

2002 2003 2004 2007 All years

n %

C/f n %

C/f n %

C/f n %

C/f n %

C/f

Lepisosteidae 3 0.15 0.05 3 0.08 0.02AnguillidaeEngraulidae 23 11.92 3.83 23 0.58 0.15Clupeidae 2 0.10 0.03 110 6.28 1.53 112 2.80 0.75Cyprinidae 21 10.88 3.50 1,285 63.27 20.40 935 53.40 12.99 2,241 56.04 14.94Catostomidae 1 0.05 0.02 121 6.91 1.68 122 3.05 0.81Ictaluridae 1 0.06 0.01 1 0.03 0.01Aphredoderidae 1 0.05 0.02 15 62.50 1.67 16 0.40 0.11Atherinopsidae 22 1.08 0.35 1 4.17 0.11 33 1.88 0.46 56 1.40 0.37Fundulidae 1 0.06 0.01 1 0.03 0.01Poeciliidae 1 0.52 0.17 58 2.86 0.92 7 29.17 0.78 18 1.03 0.25 84 2.10 0.56Centrarchidae 148 76.68 24.67 580 28.56 9.21 520 29.70 7.22 1,248 31.21 8.32Percidae 41 2.02 0.65 1 4.17 0.11 7 0.40 0.10 49 1.23 0.33Elassomatidae 29 1.43 0.46 2 0.11 0.03 31 0.78 0.21Achiridae 9 0.44 0.14 3 0.17 0.04 12 0.30 0.08Total n 193 2,031 32.41 224 3.22 1,751 24.43 3,999Number of traps 6 63 9 72 150Number of empty traps 1 11 5 8 25Percent empty traps 16.7 17.5 55.6 11.1 16.7Total C/f 32.17 32.24 2.67 24.32 26.66

1Subadults and adults of relatively few specimens of slim-bodied taxa included (for example, engraulids, cyprinids, atherinopsids).2Low catch rate and large proportion of empty traps due to limited number set in early March.
Results 15

0

50

100

150

200

5,000

10,000

15,000

20,000

25,000

30,000

16

18

20

22

24

26

28

30

DISCHARGE, IN CUBIC FEET PER SECOND

TEMPERATURE, IN DEGREES CELSIUS

CATCH-PER-UNIT EFFORT

5 10 15 20 25 31 5 10 15 20 25 30 5 10 15 20 25 31 5 10

MARCH APRIL MAY JUNE

2006

DISCHARGE

TEMPERATURE

A

B

Figure 6. (A) Continuous discharge at the Blountstown gage (solid black line) and mean water 

temperature (dashed blue line) on light-trap sampling dates in the Apalachicola River and River 

Styx in 2006, and (B) catch-per-unit effort (C/f; mean number fish per trap ± 1SE) by date for all 

age-0 fishes (bottom graph).
16 Composition of Age-0 Fish Assemblages in the Apalachicola River, River Styx, and Battle Bend, Florida

0

50

100

150

500

5,000

10,000

15,000

20,000

25,000

30,000

16

18

20

22

24

26

28

30

DISCHARGE, IN CUBIC FEET PER SECOND

TEMPERATURE, IN DEGREES CELSIUS

CATCH-PER-UNIT EFFORT

1 10 15 20 25 31 5 10 15 20 25 30 5 10 15 20 25 31 5 10

MARCH APRIL MAY JUNE

2007

DISCHARGE

TEMPERATURE

5

JULY

15 20 25 30 5 10

200

250

35,000

40,000

A

B

Figure 7. (A) Continuous discharge at the Blountstown gage (solid black line) and mean water 

temperature (dashed blue line) on light-trap sampling dates in the Apalachicola River, River Styx, 

and Battle Bend in 2007, and (B) catch-per-unit effort (C/f; mean number fish per trap ± 1SE) by 

date for all age-0 fishes (bottom graph).
Results 17

All Years

Taxonomic Composition—Species richness, diversity, 

and evenness varied within each water body across all years 

of study (table 6). A species accumulation curve for all fish 

collected in the river channel, River Styx, and Battle Bend 

during 2002-2007 was asymptotic at about 40 to 45 taxa 

for 6 to 13 cumulative samples (fig. 8). Therefore, diversity 

metrics were relatively uninformative for the Apalachicola 

River in 2003, River Styx in 2002, and Battle Bend in 

2002 and 2004 due to limited sample sizes. In 2006-2007, 

species richness at each of the sites was generally lower 

than total species richness across all years. Among water 

bodies and across all years, richness was similar between 

the Apalachicola River channel and River Styx, and lower 

in Battle Bend. Within each water body, the value of the 

Shannon-Wiener diversity index was highest in 2006 for 

River Styx, and highest in 2007 for the Apalachicola River 

and Battle Bend. River Styx had more species than the other 

sites, but samples were numerically dominated by relatively 

few species. Thus, evenness was lowest for River Styx among 

all years combined, whereas the river channel had the highest 

evenness, with Battle Bend intermediate between the two.

Abundance and Dominance―As percent composition of 

taxa combined by family, cyprinids, and centrarchids were the 

most abundant age-0 fish in samples obtained from floodplain 

habitats, followed to a lesser extent by percids, clupeids, and 

catostomids (fig. 9). Cyprinids were also dominant in the river 

channel (including different species than those found in the 

floodplain), and centrarchids were variable among years, but 

generally second or third in abundance in mainstem habitats. 

The most notable difference between the floodplain and the 

river channel was the greater relative abundance of catostomids in the latter. Similar trends were evident in plots of 

catch-per-unit effort for individual families across years, and 

extensive variation occurred within water bodies and among 

years (fig. 10). Most of the variation is directly attributable 

to the effects of outliers as a result of one or a few traps that 

captured unusually large numbers of an individual taxon. For 

example, for all traps in River Styx, C/f for all centrarchids 

was greatest in 2007 among years as a result of the single 

trap that captured 4,012 Micropterus salmoides, with a value 

of 105.8 ± 90.9SE, followed by 2004, which had C/f = 60.7 

± 36.9SE. The large SE value for 2004 also indicated that 

there may have been outliers in that year; upon reexamination of raw data, it was determined that a single trap captured 

Table 6. Number of traps, percent empty, and diversity metrics of samples combined by year 

of age-0 fishes taken by light traps in the Apalachicola River, River Styx, and Battle Bend from 

2002-2007. 

[H¢, Shannon-Wiener diversity index; J¢, Pielou’s evenness; n, number of traps; N, number of age-0 fish; 

S, total number of taxa; 1-Dˆ , Simpson’s index of diversity. Taxonomic data were upward collapsed; that 

is, specimens not identified to species were redistributed in proportion to relative numbers of identified 

species per water body by year (excluding cyprinids and Lepomis sp.).

Year

Traps

S N H¢ 1-Dˆ J¢ n Percent 

empty

Apalachicola River

2003 2 0 4 22 1.01 0.57 0.73

2004 111 5.4 34 5,912 1.69 0.63 0.48

2006 169 20.7 28 3,763 1.99 0.81 0.60

2007 144 19.4 28 1,005 2.55 0.90 0.77

All Years 426 16.2 39 10,702 2.31 0.84 0.63

River Styx

2002 55 49.1 11 277 1.58 0.75 0.66

2003 102 14.7 32 9,934 1.18 0.43 0.34

2004 18 5.6 21 1,100 1.60 0.68 0.53

2006 172 5.2 34 8,797 1.96 0.75 0.55

2007 72 9.7 26 5,497 1.00 0.43 0.31

All Years 419 14.1 40 25,605 1.89 0.72 0.51

Battle Bend

2002 6 16.7 5 193 1.26 0.68 0.78

2003 63 17.5 27 2,031 1.70 0.64 0.52

2004 9 55.6 4 24 0.92 0.54 0.66

2007 72 11.1 25 1,751 1.99 0.79 0.62

All Years 150 16.7 35 3,999 2.06 0.75 0.58
18 Composition of Age-0 Fish Assemblages in the Apalachicola River, River Styx, and Battle Bend, Florida

448 Lepomis macrochirus. When both of these outliers 

were removed, the C/f for all centrarchids was much more 

consistent with other years of sampling in River Styx (that is, 

C/f = 24.9 ± 10.1SE in 2006, and 15.0 ± 3.8SE in 2007). For 

all taxa, River Styx had the greatest overall catch rates and 

yielded the most fish (table 4 and fig. 10). The Apalachicola 

River and Battle Bend sites had comparable overall catch 

rates, although catch-per-unit effort was much smaller for 

these sites than River Styx (tables 3 and 5).

Chronological Appearance―Prior to 2006, light-trap 

sampling was done from February to the late summer and 

early fall months (Walsh and others, 2006). Based on those 

results, it was determined that greatest spawning activity for 

most species extended from March through June, although 

some habitat generalists (for example, Lepomis macrochirus) 

continued to spawn throughout summer months. For the 

current study, the appearances of age-0 cohorts (as cumulative 

proportion appearing in traps) of target species (Micropterus

salmoides, Minytrema melanops, Lepomis spp.) were summarized in a complementary report (Pine and others, 2008). 

Walsh and others (2006) summarized data for additional 

species of centrarchids and combined subordinate taxa of other 

families. 

To summarize data for all years and all taxa of age-0 fish 

collected in the Apalachicola River and multiple floodplain 

water bodies, catch-per-unit values were calculated across 

Julian dates for the most abundant families of fishes and for all 

taxa combined, disregarding interannual and spatial variability 

(fig. 11). The resulting plots reveal the range of peaks and 

temporal extent of appearance of age-0 fish in traps. Temporal 

variation in some of the peaks is due in part to interspecific 

differences in the timing of spawning. For example, among 

centrarchids, Pomoxis nigromaculatus spawns relatively 

early in the spring, whereas Lepomis macrochirus has a very 

protracted spawning period and may exhibit peaks within 

0 5 10 15

SAMPLES

20

25

30

35

40

45

SPECIES COUNT

Figure 8. Species accumulation curve for all samples of age-0 

fish collected in the Apalachicola River, River Styx, and Battle 

Bend for the years 2002-2007.

2004 2006 2007

A Apalachicola River

B River Styx

C Battle Bend

2003 2004

2002 2003 2004 2006 2007

0

20

40

60

80

100

PERCENT COMPOSITION

0

20

40

60

80

100

PERCENT COMPOSITION

0

20

40

60

80

100

PERCENT COMPOSITION

EXPLANATION

OTHERS

ENGRAULIDAE

PERCIDAE

CLUPEIDAE

CATOSTOMIDAE

CENTRARCHIDAE

CYPRINIDAE

Figure 9. Percent composition by year of families representing 

greatest abundance of age-0 fishes collected by light trap in the 

Apalachicola River (A), River Styx (B), and Battle Bend (C).
Results 19

APALACHICOLA

RIVER

RIVER

STYX

BATTLE

BEND

2004 2006 2007 2003 2006 2007 2007 0

5

10

15

20

25

Percidae

2003

MEAN CATCH-PER-UNIT EFFORT

APALACHICOLA

RIVER

RIVER

STYX

BATTLE

BEND

2004 2006 2007 2002 2003 2004 2006 2007 2003 2007 0

50

100

150

200

Cyprinidae

MEAN CATCH-PER-UNIT EFFORT MEAN CATCH-PER-UNIT EFFORT

0

50

100

150

200

Centrarchidae

APALACHICOLA

RIVER

RIVER

STYX

BATTLE

BEND

2004 2006 2007 2002 2003 2004 2006 2007 2003 2007

0

5

10

15

20

25

30

35

40

45

Catostomidae

MEAN CATCH-PER-UNIT EFFORT

APALACHICOLA

RIVER

RIVER

STYX

BATTLE

BEND

2004 2006 2007 2003 2004 2006 2007 2007

MEAN CATCH-PER-UNIT EFFORT

0

25

50

75

100

125

150

All Taxa

APALACHICOLA

RIVER

RIVER

STYX

BATTLE

BEND

2004 2006 2007 2002 2003 2004 2006 2007 2003 2007

Figure 10. Mean catch-per-unit effort (C/f + 1SE) 

of most abundant age-0 fishes by family and all 

taxa in the Apalachicola River, River Styx, and 

Battle Bend by year.
20 Composition of Age-0 Fish Assemblages in the Apalachicola River, River Styx, and Battle Bend, Florida

Figure 11. Mean catch-per-unit effort (C/f) of dominant families and all taxa for combined 

years (2002-2007) of age-0 fish caught by light traps in the Apalachicola River and multiple 

floodplain water bodies by Julian date and month. Catch data based on 64,164 fish 

representing 1,247 traps (empty traps excluded). 

J F M A M J J A S O N D

0

15

30

45

60

75

J F M A M J J A S O N D

0

50

100

150

200

J F M A M J J A S O N D

0

50

100

150

500

505

J F M A M J J A S O N D

0

10

20

30

40

0 50 100 150 200 250 300 350

J F M A M J J A S O N D

0

100

200

300

0 50 100 150 200 250 300 350

0 50 100 150 200 250 300 350

0 50 100 150 200 250 300 350

0 50 100 150 200 250 300 350

MONTH

JULIAN DATE

MONTH

JULIAN DATE

MONTH

JULIAN DATE

MONTH

JULIAN DATE

MONTH

JULIAN DATE

MEAN CATCH-PER-UNIT EFFORT MEAN CATCH-PER-UNIT EFFORT MEAN CATCH-PER-UNIT EFFORT

Catostomidae

Cyprinidae

Centrarchidae

Percidae

All Taxa
Discussion 21

specific windows of time based on large catches of one or a 

few traps. Catostomids appeared to have a relatively narrow 

window of time in which the age-0 cohorts recruited to light 

traps in comparison to the other dominant families. The 

greatest amount of spawning activity, as inferred by recruitment to light traps, was between March and July (approximate 

Julian dates 60-210, fig. 11). Pine and others (2008) noted 

that there was probably a minimum 1-2 week period between 

hatching and recruitment to light traps for the target species. 

For some taxa, however, recruitment may have occurred in a 

matter of days or less, as evidenced by the collection of very 

small yolk-sac larvae.

Pre- and Post-Enhancement of Battle Bend

In 2006, contractors for the Florida Fish and Wildlife 

Conservation Commission completed a habitat enhancement project at Battle Bend that consisted of excavating and 

removing sand and debris at the mouth in order to reestablish 

connectivity of the oxbow with the main river channel 

during low flows. An objective of this study was to compare 

data on the age-0 fish assemblage collected prior to habitat 

enhancement, with post-enhancement data collected in 2007. 

Pre-enhancement data included light trap samples that were 

placed in Battle Bend in 2002, 2003, and 2004. The amount of 

effort in the first and last of those years was limited to a total 

of 15 trap nights, and yielded few numbers of species and low 

overall diversity (table 6). Therefore, it was concluded that 

the only possible meaningful comparison of pre- and postenhancement data would be for 2003 and 2007. Hydrologic 

conditions between these 2 years differed substantially; 2003 

was a relatively high-water year and 2007 was a year of 

extreme drought (fig. 5). 

A ranked species-abundance plot based on cumulative 

percent dominance (k-dominance curve) indicated that the 

samples taken in 2003 and 2007 had similar richness, and that 

2007 had greater evenness (lower dominance) of the most 

abundant taxa (fig. 12A). However, a partial dominance curve 

(fig. 12B) revealed that 2007 had greater unevenness than 2003 

for a suite of taxa lower in the dominance ranks, only slightly 

evident in the cumulative plot above the six most abundant 

taxa. Overall, values for the Shannon-Wiener diversity 

index, Simpson’s index of diversity, and Pielou’s evenness 

were slightly greater in 2007 than in 2003 (table 6), possibly 

indicating a shift in community characteristics between 

pre- and post-enhancement conditions. A tabular summary of 

taxa ranked by percent composition by year indicated notable 

differences in assemblage composition and relative abundance 

(table 7). Although the total number of species collected in 

2003 and 2007 were comparable (25 and 27 respectively), the 

species present or absent in samples from each year differed 

among both low- and high-abundance taxa. Three species 

were among the top five in abundance in light-trap catches 

of both years: Notropis texanus, Lepomis macrochirus, and 

Micropterus salmoides (cumulative percent composition of 

74 percent and 67 percent in 2003 and 2007, respectively). 

Nine species were collected in 2003 but not collected in 2007, 

all at percent composition values of 0.3 percent or less: Percina

nigrofasciata, Elassoma okefenokee, Opsopoeodus emiliae, 

Lepisosteus oculatus, Centrarchus macropterus, Micropterus

punctulatus, Alosa sp., Erimyzon sucetta, and Aphredoderus

sayanus. In contrast, six species were collected in 2007 but 

not in 2003: Carpiodes cyprinus, Cyprinidae sp., Notropis

maculatus, Minytrema melanops, Fundulus sp., Dorosoma

cepedianum, and Noturus leptacanthus. The Bray-Curtis 

similarity coefficient between years was 69.2 for samples 

transformed to presence-absence, and 65.8 when transformed 

as fourth-root. For species in the mid- to low-range of rank 

abundance for either year, the most notable differences were 

for the following species (percent composition, year): Lepomis

auritus (7.2 percent, 2003; 1.3 percent, 2007), Lepomis

gulosus (2.7 percent, 2003; <0.1 percent, 2007), Pomoxis

nigromaculatus (2.4 percent, 2003; <0.1 percent, 2007), 

Dorosoma petenense (<0.1 percent, 2003, 6.2 percent, 2007), 

and, Cyprinus carpio (<0.1 percent, 2003; 3.8 percent, 2007). 

Among dominant species in both years, the most substantial 

difference was that Carpiodes cyprinus was not collected in 

2003, but represented 6.7 percent of the catch in 2007.

Discussion

A primary objective of this study was to examine age-0 

cohort recruitment and abundance in relation to patterns of 

adult fish movements in mainstem and floodplain habitats 

of the Apalachicola River in 2006-2007 for targeted species 

of management interest (Micropterus spp., Minytrema melanops, Lepomis spp., and Ictalurus punctatus). Results of the 

telemetry study and aspects of larval catch data, as cumulative 

proportions of light traps per week containing age-0 cohorts 

of the target species over time and in relation to discharge, 

were summarized in a complementary report (Pine and others, 

2008). Discrete movement patterns of tagged reproductive 

adults of Micropterus spp. were characterized by individual 

fish that utilized mainstem or floodplain habitats only, as well 

as individuals that moved between both habitats during the 

spawning season and at other times of the year. Among the 

target species, Ictalurus punctatus appears to be negatively 

phototaxic and was rarely collected in light traps, hence no 

conclusions could be drawn regarding age-0 cohorts of this 

species. Age-0 cohorts of Micropterus spp. and Lepomis spp. 

were taken in large numbers in mainstem and floodplain 

habitats in 2006 and 2007, and appeared with greater frequency 

in light traps and were collected in greater abundance in both 

the latter habitat and year. Minytrema melanops was also 

collected in in the mainstem and floodplain but exhibited variation between habitats as well as years. In 2006, proportions of 

light traps containing M. melanops were similar between the 

Apalachicola River and River Styx, whereas in 2007, M. melanops was found in a higher proportion of light traps in the river 
22 Composition of Age-0 Fish Assemblages in the Apalachicola River, River Styx, and Battle Bend, Florida

channel near River Styx than in the latter water body itself. 

Also in 2007, M. melanops was found in a much higher proportion of light traps in the the Apalachicola River than in Battle 

Bend, and the total number of age-0 fish collected in the latter 

was very low (n = 3; table 2). These results suggest that M. 

melanops appears to spawn in floodplain habitats (that is, River 

Styx) in some if not all years, but in 2007 at least, this species 

may not have substantially utilized Battle Bend for spawning. 

A possible explanation for these observations may relate to 

habitat requirements for successful spawning of M. melanops

(for example, flow and/or substrate) and differences between 

floodplain habitats or hydrologic conditions in any given year.

Floodplain habitats in the Apalachicola River support 

a rich assemblage, as evidenced by light-trap catches of 

age-0 fishes during this study as well as in previous years 

(Walsh and others, 2006). Not unexpectedly, catches in 

2006-2007 were dominated by relatively few species of 

cyprinids, centrarchids, percids, and catostomids (table 2 

Figure 12. (A) Cumulative and (B) partial ranked species abundance (k-dominance) plots of age-0 

fishes collected in Battle Bend in 2003 (black line and circles) and 2007 (blue line and diamonds). 

10

20

30

40

50

60

1 10 100

20

40

60

80

100

CUMULATIVE DOMINANCE, IN PERCENT

SPECIES RANK

PARTIAL DOMINANCE, IN PERCENT

1 10 100

SPECIES RANK

Battle Bend

2003

Battle Bend

2007

A

B

Battle Bend

2003

Battle Bend

2007
Discussion 23

and fig. 9). For all light trap samples in 2006-2007, the 

following species accounted for 80.8 percent of all individuals 

collected: Notropis texanus (28.9 percent), Micropterus spp. 

(28.9 percent), Lepomis macrochirus (7.9 percent), Carpiodes

cyprinus (6.2 percent), Cyprinidae sp. (4.6 percent), and 

Minytrema melanops (4.2 percent). Some differences between 

mainstem and floodplain catches of these dominant species 

were apparent. The catostomids C. cyprinus and M. melanops

constituted a greater proportion of fish collected in light traps 

set in the river. Percent composition of L. macrochirus was 

generally similar between years in the Apalachicola River 

and in River Styx, and this species made up a substantial 

portion of the catch (16.6 percent) in Battle Bend in 2007, 

thus showing an overall greater relative abundance in lentic 

floodplain habitats. Percent composition of Notropis texanus

was quite variable between years within each water body. 

Likewise, Micropterus spp. abundance was variable within 

and between sites and years (especially due to skewed catches 

in River Styx in 2007); like L. macrochirus and N. texanus, 

the spatial occurrence and catch rates of Micropterus spp. in 

both mainstem and floodplain water bodies indicate that these 

taxa are habitat generalists, as noted by Kinsolving and Bain 

(1993) and others.

Despite the dominance of relatively few species in all 

light trap catches during this study, including both habitat 

generalists and apparent fluvial specialists (for example, 

C. cyprinus), the richness of taxa represented by age-0 

cohorts in floodplain water bodies attests to the importance 

of these habitats in providing spawning and nursery areas for 

a broad suite of species. Similar results have been reported 

in many other studies; that is, that floodplain communities 

may be dominated by relatively few species, but that diverse 

Table 7. Rank abundance (n and percent composition) by species of age-0 fishes collected in Battle Bend in 

2003 and 2007.

[n, number of specimens; percent, percent composition by year]

Species

2003

Species

2007

n Percent n Percent

Notropis texanus 1,191 58.64 Notropis texanus 686 39.18

Micropterus salmoides 182 8.96 Lepomis macrochirus 291 16.62

Lepomis auritus 147 7.24 Micropterus salmoides 203 11.59

Lepomis macrochirus 130 6.40 Carpiodes cyprinus 118 6.74

Lepomis gulosus 55 2.71 Dorosoma petenense 109 6.23

Pomoxis nigromaculatus 48 2.36 Notemigonus crysoleucas 93 5.31

Gambusia holbrooki 46 2.26 Cyprinella venusta 77 4.40

Cyprinella venusta 41 2.02 Cyprinus carpio 67 3.83

Notemigonus crysoleucas 32 1.58 Labidesthes sicculus 33 1.88

Etheostoma fusiforme 29 1.43 Lepomis auritus 22 1.26

Labidesthes sicculus 22 1.08 Gambusia holbrooki 17 0.97

Elassoma zonatum 22 1.08 Cyprinidae sp. 8 0.46

Lepomis sp. 16 0.79 Etheostoma fusiforme 4 0.23

Cyprinus carpio 16 0.79 Notropis maculatus 4 0.23

Heterandria formosa 12 0.59 Etheostoma swaini 3 0.17

Trinectes maculatus 9 0.44 Trinectes maculatus 3 0.17

Percina nigrofasciata 7 0.34 Minytrema melanops 3 0.17

Elassoma okefenokee 7 0.34 Lepomis sp. 2 0.11

Etheostoma swaini 5 0.25 Elassoma zonatum 2 0.11

Opsopoeodus emiliae 5 0.25 Fundulus sp. 1 0.06

Lepisosteus oculatus 3 0.15 Heterandria formosa 1 0.06

Centrarchus macropterus 1 0.05 Lepomis gulosus 1 0.06

Micropterus punctulatus 1 0.05 Pomoxis nigromaculatus 1 0.06

Alosa sp. 1 0.05 Dorosoma cepedianum 1 0.06

Dorosoma petenense 1 0.05 Noturus leptacanthus 1 0.06

Erimyzon sucetta 1 0.05

Aphredoderus sayanus 1 0.05
24 Composition of Age-0 Fish Assemblages in the Apalachicola River, River Styx, and Battle Bend, Florida

assemblages are characteristic of floodplain habitats and that 

spawning and recruitment of age-0 cohorts are intricately 

linked to the hydrologic cycle (for example, Guillory, 1979; 

Holland, 1986; Finger and Stewart, 1987; Scheidegger, 1990; 

Baker and others, 1991; Killgore and Baker, 1996; Knight and 

Bain, 1996; Winemiller and others, 2000; Miranda, 2005).

Water managers in the Apalachicola-Chattahoochee-Flint 

basin are challenged with identifying critical flows required 

to sustain aquatic biological communities while balancing 

other resource needs. Light and others (1998) and Walsh and 

others (2006) reported that as many as 80 percent of about 91 

freshwater fishes in the Apalachicola River may use floodplain 

habitats during some aspect of their life history. For fishes 

that use floodplain habitats, information about spawning times 

and recruitment periods for the most vulnerable life-history 

stage, the age-0 cohort, is necessary to evaluate how changes 

in the timing, magnitude, and duration of hydrologic pulses 

may influence population dynamics. Specifically, these 

changes may affect spawning success, survivorship, year-class 

strength, and the resiliency of species and communities to 

intra- and inter-annual variation. The chronological appearance of age-0 fish in river and floodplain water bodies of the 

Apalachicola River provides but just one aspect to consider 

in assessing how hydrologic conditions influence aquatic 

communities. Nevertheless, understanding the chronology is 

a necessary step in identifying resource needs using a holistic 

approach. Thus, data on the chronological appearance and 

relative abundance of age-0 fish obtained in this study and 

in prior years is useful for determining the relative timing in 

which floodplain conditions are optimal for maximizing the 

success of year-class recruitment. However, these data were 

collected over a limited time period and under extreme hydrologic conditions (including the low-water years of 2006-2007) 

and show no clear trends for the species targeted as part of the 

simultaneous adult-movement investigation (Pine and others, 

2008). This finding suggests that data collection over multiple 

years, under differing hydrologic conditions, would be 

informative to better evaluate how variable flows and habitat 

conditions affect fishes that utilize the floodplain. Based on 

multiple years of study, it is evident that families represented 

by the most abundant species utilize both floodplain and river 

habitats as spawning and nursery areas for an extended period 

of time throughout the spring and summer, with peak recruitment of age-0 cohorts from early March through mid-June 

(fig. 11).

Temporal shifts in the appearance and relative abundance of individual taxa in this study were concordant with 

trends observed in other studies. Gallagher (1979) collected 

ichthyoplankton representing 10 families from March to 

September in the lower Mississippi River, with peak abundances from late May through early July. Floyd and others 

(1984) documented larval fish in a Kentucky stream from 

March through July; there was spatial and temporal overlap 

among taxa, and individual species were taken as larvae for 

periods of 3 to 12 weeks. In the upper Mississippi River, 

Holland (1986) found that fish eggs and larvae appeared from 

April to August, with seasonal shifts in dominant taxa and 

peak abundances that varied with discharge and temperature. 

Finger and Stewart (1987) found that age-0 abundance 

varied between 2 years with different flooding regimes in a 

lowland hardwood wetland in Missouri, although they did not 

quantify temporal appearance of larvae. Scheidegger (1990) 

found that the chronological appearance of larvae of different 

families was consistent over a 2-year period in the Cahaba 

and Tallapoosa Rivers in Alabama, and the following general 

sequence was observed: percids, catostomids, centrarchids, 

cyprinids, clupeids, poeciliids, fundulids, and atherinopsids. In the Tallahatchie River, Mississippi, larvae of early 

spawners (for example, Dorosoma cepedianum, Pomoxis spp., 

Etheostoma spp., Percina spp.) were dominant from spring to 

mid-summer, and late spawners (centrarchids, Notropis spp., 

Cyprinella venusta) were present on the floodplain from May 

through October (Turner and others, 1994). Killgore and 

Baker (1996) collected ichthyoplankton in the floodplain of 

the Cache River, Arkansas, from March through early June, 

and found the greatest abundance of dominant taxa (percids, 

aphredoderids, cyprinids, centrarchids) in late spring (April to 

early May), corresponding to water temperatures of 18-22 °C. 

The aforementioned studies specifically chronicle the timing 

and abundance of larval fish in large rivers and/or their floodplains in conjunction with hydrologic fluctuations (backwater 

indundation), habitat use, or both. An extensive body of 

literature documents the exploitation of floodplain habitats by 

cohorts other than age-0 fish (and/or age-0 fish at postlarval 

stages). These studies address adult spawning, resource use, 

assemblage characteristics, interannual variation, and other 

factors associated with hydrologic conditions, especially 

the annual flood pulse or altered flow regimes. Examples of 

these studies for rivers in the United States include Beecher 

and others (1977), Guillory (1979), Ross and Baker (1983), 

Schlosser (1985), Sheaffer and Nickum (1986), Kwak (1988), 

Baker and others (1991), Winemiller and others (2000), 

Rutherford and others (2001), Koel and Sparks (2002), Barko 

and others (2004), and Koel (2004).

In the present study, the appearance of age-0 fish of 

different taxonomic groups was similar to that reported by 

Gallagher (1979) and Scheidegger (1990), although the range 

of dates when cyprinids and centrarchids were most abundant 

varied depending on species. These two groups were dominant 

in spring to early-summer samples as in the study by Turner 

and others (1994), thus corroborating protracted spawning in 

floodplain habitats. In the present study, backwater habitats 

were identified as especially important nursery areas for 

centrarchids (fig. 9). 

Ross and Baker (1983) recognized two groups of fish 

species based on response to flooding: quiescent and exploitative. Flood-exploitative species opportunistically capitalize 

on resources made available when the floodplain is inundated. 

Such species are typically habitat generalists that may delay 

reproduction in order to feed in productive floodplain habitats 

and acquire energy stores for spawning. In the Mississippi 

stream studied by Ross and Baker (1983), two of the dominant 
Acknowledgments 25

taxa that exhibit these characteristics were also floodplaindominant species in the present study: Lepomis macrochirus

and Notropis texanus. As noted by Ross and Baker (1983), 

flood-exploitative species often have breeding seasons that 

extend well beyond the time of spring flooding. Results 

from the present study confirm that the Apalachicola River 

floodplain assemblage includes a guild of dominant species 

exhibiting this pattern of spawning phenology. The concept of 

flood-exploitative fishes proposed by Ross and Baker (1983) 

illustrates the importance of how reproductive patterns of individual species determine responses to hydrologic conditions. 

Fractional spawners (fishes that produce multiple clutches 

in a single season) are less likely to be adversely affected by 

disruptions in timing and/or duration of flooding than batchspawning species with reproductive cycles that are tightly 

synchronized to hydrologic pulses (Welcomme, 1985).

In rivers at temperate latitudes, water temperature is 

generally considered to promote the reproductive activity 

of adult fishes, and may also influence critical resources for 

early life-history stages. Walsh and others (2006) plotted mean 

water temperature for light traps containing representatives 

of individual fish families for samples in the Apalachicola 

River and floodplain, and found relatively narrow temperature ranges by family for the appearance of age-0 fishes. 

The activity of dominant freshwater groups was observed over 

ascending temperatures to infer the chronology of the appearance of the age-0 cohort in the following order: Catostomidae, 

Percidae, Cyprinidae, and Centrarchidae. Esocids and aphredoderids appeared at low temperatures (early spawners) and 

poeciliids and ictalurids appeared at high temperatures (late 

spawners). Water temperatures during the peak spawning 

period from mid-March through April 2006 in River Styx 

ranged from about 16-26 °C (fig. 6).

Habitat enhancement at Battle Bend improved connectivity between the oxbow (old river channel) and the current 

river channel during low-flow conditions. River flows were 

relatively low during the spring and summer months of 2006 

and 2007. Consequently, ingress and/or egress of pre-reproductive adults between the mainstem and backwater habitat 

should have been improved relative to pre-enhancement, lowwater years. It is notable that percent composition of age-0 

individuals of two of the dominant species, Lepomis macrochirus and Micropterus salmoides, was much greater in 2007 

in comparison to 2003 (table 7). Moreover, the appearance 

of Carpiodes cyprinus in Battle Bend in 2007 suggests that 

the habitat enhancement may have provided more river-like 

nursery refugia.

Acknowledgments

We especially thank Charlie Mesing of the Florida Fish and Wildlife 

Conservation Commission (FFWCC) for guidance and support throughout the 

project. This work could not have been completed without the dedicated efforts 

of Edward Camp, Drew Dutterer, Jared Flowers, Colin Hutton, Kevin Johnson, 

Michal Jones, and Darren Pecora of the University of Florida. Additional 

assistance in the field and laboratory was provided by Sherry Bostick of the 

U.S. Geological Survey (USGS), and Matthew Glicco of Sante Fe College. 

Howard Jelks and Walter Courtenay (USGS) provided helpful comments on an 

earlier draft of the report.

This study was conducted as part of the USGS-FFWCC Joint Funding 

Agreement 07E0FL207217 (USGS) and 06196 (FFWCC).
26 Composition of Age-0 Fish Assemblages in the Apalachicola River, River Styx, and Battle Bend, Florida

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Walsh and others—Composition of Age-0 Fish Assemblages in the Apalachicola River, River Styx, and Battle Bend, Florida—Open-File Report 2009-1145