Biological Report 82(11.91) 

January 1989 

Species Profiles: Life Histories and 

Environmental Requirements of Coastal Fishes 

and Invertebrates (South Atlantic) 

SPOT 

Fish and Wildlife Service 

- 

Coastal Ecology Group 

Waterways Experiment Station 

U.S. Department of the Interior U.S. Army Corps of Engineers 
Biological Report 82(11.91) 

TR EL-82-4 

January 1989 

Species Profiles: Life Histories and Environmental Requirements 

of Coastal Fishes and Invertebrates (South Atlantic) 

SPOT 

L. S. Hales 

and 

M. J . Van Den Avyl e 

Georgia Cooperative Fish and Wildlife Research Unit 

School of Forest Resources 

University of Georgia 

Athens, GA 30602 

Project Officer 

David Moran 

National Wetlands Research Center 

U.S. Fish and Wildlife Service 

1010 Gause Boulevard 

Sl idel 1 , LA 70458 

Performed for 

Coastal Ecology Group 

Waterways Experiment Station 

U.S. Army Corps of Engineers 

Vicksburg, MS 39180 

and 

U.S. Department of the Interior 

Fish and Wildlife Service 

Research and Development 

National Wetlands Research Center 

Washington, DC 20240 
This series can be referenced as follows: 

.S. Fish and Wildlife Service. 1983-19 . Species profiles: life histories 

and environmental requirements of coast3 fishes and invertebrates. U.S. Fish 

Wildl . Serv. Biol . Rep. 82(11). U.S. Army Corps of Engineers TR EL-82-4. 

This profile can be cited as follows: 

Hales, L.S., and M.J. Van Den Avyle. 1989. Species profiles: life histories 

and environmental requirements of coastal fishes and invertebrates (South 

Atlantic)--spot. U.S. Fish Wildl . Serv. Biological Report 82(11.91). U.S. Army 

Corps of Engineers TR EL-82-4. 24 pp. 
PREFACE 

This species profile is one of a series on coastal aquatic organisms, 

principally fish, of sport, commercial, or ecolo'gical importance. The profiles 

are designed to provide coastal managers, engineers, and biologists with a brief 

comprehensive sketch of the biological characteristics and environmental 

requirements of the species and to describe how populations of the species may be 

expected to react to environmental changes caused by coastal development. Each 

prof i le has sections on taxonomy, 1 ife history, ecological role, environmental 

requirements, and economic importance, if applicable. A three-ri ng binder is 

used for this series so that new profiles can be added as they are prepared. 

This project is jointly planned and financed by the U.S. Army Corps of Engineers 

and the U.S. Fish and Wildlife Service. 

Suggestions or questions regarding this report should be directed to one of 

the foll owing addresses. 

Information Transfer Special ist 

National Wetlands Research Center 

U.S. Fish and Wildlife Service 

NASA-Slidell Computer Complex 

1010 Gause Boulevard 

Slidell, LA 70458 

U.S. Army Engineer Waterways Experiment Station 

Attenti on: WESER-C 

Post Office Box 631 

Vicksburg, MS 39180 

iii 
CONVERSION TABLE 

Metric to U.S. Customary 

Multiply 

millimeters (mm) 

centimeters (cm) 

meters (m) 

meters (m) 

ki lometers (km) 

kilometers (km) 

square meters (m2) 

square kilometers (km2) 

hectares (ha) 

liters (1) 

cubic meters (m3) 

cubic meters (m3) 

milligrams (mg) 

grams (g) 

ki lograms (kg) 

metric tons (t) 

metric tons (t) 

kilocalories (kcal) 

Celsius degrees (OC) 

inches 

inches 

feet (ft) 

fathoms 

statute miles (mi) 

nautical miles (nmi) 

square feet (ft2) 

square miles (mi2) 

acres 

gallons (gal) 

cubic feet (ft3) 

acre-feet 

ounces (02) 

ounces (02) 

pounds (lb) 

pounds (lb) 

short tons (ton) 

British thermal units (Btu) 

Fahrenheit degrees (OF) 

U.S. Customary to Metric 

25.40 

2.54 

0.3048 

1.829 

1.609 

1.852 

To Obtain 

inches 

inches 

feet 

fathoms 

statute miles 

nautical miles 

square feet 

square miles 

acres 

gal lons 

cubic feet 

acre-feet 

ounces 

ounces 

pounds 

pounds 

short tons 

British thermal units 

Fahrenheit degrees 

millimeters 

centimeters 

meters 

meters 

kilometers 

kilometers 

square meters 

square kilometers 

hectares 

1 i ters 

cubic meters 

cubic meters 

milligrams 

grams 

kilograms 

metric tons 

metric tons 

kilocalories 

Celsius degrees 
CONTENTS 

Page 

PREFACE .................................................................. CONVERSION TABLE ......................................................... ACKNOWLEDGMENTS .......................................................... 

NOMENCLATURE/TAXONOMY/RANGE .............................................. MORPHOLOGY AND IDENTIFICATION AIDS ....................................... REASON FOR INCLUSION IN SERIES ........................................... LIFE HISTORY ............................................................. Spawning ............................................................... Eggs and Larvae ........................................................ Juveniles and Adults ................................................... GROWTH CHARACTERISTICS .................................................... Length-Weight Relationship ............................................. Larvae and Postlarvae .................................................. Juveniles and Adults ................................................... Size and Age at Maturity ............................................... THE FISHERY .............................................................. History ................................................................. Management ............................................................. Population Dynamics .................................................... ECOLOGICAL ROLE .......................................................... Food and Feeding Habits ................................................ Production and Energetics .............................................. Predation and Parasitism ............................................... ENVIRONMENTAL REQUIREMENTS ............................................... Temperature. Salinity. and Dissolved Oxygen ............................ Substrate and System Features .......................................... Contaminants ........................................................... Other Factors .......................................................... 

LITERATURE CITED ......................................................... 

iii 

i v 

v i 
ACKNOWLEDGMENTS 

The authors wish to thank Charles Wenner, Marine Resources Institute, 

Charleston, South Carolina; and Will iam Hettler, National Marine Fisheries 

Service, Beaufort, North Carolina for reviewing the manuscript. Figure 1 was 

prepared by Janice Kerr. 
Figure 1. Spot. 

SPOT 

Scientific name.. .......... .Leiostomus 

xanthurus Lacepede 1803 

Preferred common name.. .......... .Spot 

(Robins et al. 1980), Figure 1. 

Other common names ....... flat croaker, 

go1 den croaker, s i 1 ver gudgeon, 

goody, Lafayette, chub, roach, 

Jimmy, oldwife, spot croaker, post 

croaker, chopa blanca, Norfolk spot, 

Cape May goody (Dawson 1958) 

Class ................... Osteichthyes 

Order .................... Perciformes 

Family .................... Sciaenidae 

Geographic Range: The spot is common 

in temperate Atlantic coastal waters 

from Cape Cod southward (Figure 2) 

and along the Gulf of Mexico to the 

Bay of Campeche (Bigelow and 

Schroeder 1953; Springer and Bullis 

1956). It occurs rarely in the 

Florida Keys (Chao 1978) and north 

of Cape Cod (Bigelow and Schroeder 

1953). 

MORPHOLOGY AND IDENTIFICATION AIDS 

The following general description 

of spot was sumnarized from Johnson 

1978. The body of the spot is rather 

deep and compressed, with a strongly 

elevated back; the head is obtuse and 

short; mouth is inferior and small, 

the maxi 11 ary extends posteriorly to 

about the middle of the eye. The 

dorsal fin is continuous with a notch 

between the anterior spinous portion 

(9-11 spines) and the posterior soft 

portion (29-35 rays); the anal fin has 

2 spines and 12-13 rays. There are 

72-77 lateral line scales and 24-25 

vertebrae. Spot are bluish-gray above 
NORTH CAROLINA 

SOUTH CAROLINA 

- 

- 

- 

MILES 

KILOMETERS 

A TL A N TIC OCEAN 

Nursery areas 

Fl Spawning areas 

Figure 2. Spawning and nursery areas of the spot in the South Atlantic Region, 

Southeastern United States. 

2 
and somewhat golden below. 'They have 

12-15 oblique dark streaks (these may 

be indistinct in large specimens), a 

large black spot above the upper edge 

of the gill cover, and the fins are 

generally pale to yellowish. 

Adults are not 1 ikely to be 

confused with other species of 

sciaenids, but juveniles superficially 

resemble the juveni 1 es of several 

other s~ecies. includina the Atlantic 

croaker; ~icro~o~onias Gndul atus; the 

star drum, Stel 1 ifer 1 anceol atus; and 

the silver perch, Bairdiella 

chrysoura. The following characteristics distinauish otherwise mor~hologically simijar sciaenids from spot 

(Chao 1978): the Atlantic croaker has 

many barbels on the lower jaw and a 

strongly serrate preopercle; the star 

drum has a strongly serrate 

preopercl e, we1 1 -developed denti tion, 

and a lanceolate caudal fin; the 

silver perch has we1 1 -developed 

dentition and a rounded caudal fin. 

Although eggs and larvae of most 

sciaenids are not likely to occur with 

those of spot (Powles and Stender 

1978), the eggs and larvae of the 

silver seatrout, Cynoscion nothus, 

Equetus spp., the banded drum, Larimus 

fasciatus, and the Atlantic croaker 

may co-occur with spot. The eggs of 

most sciaenids have not been 

described, but several characters are 

useful for distinguishing larval spot 

from other species (Lippson and Moran 

1974; Fruge and Truesdale 1978; 

Johnson 1978; Powles and Stender 1978; 

Powell and Gordy 1980). The spot has 

fewer vertebrae (24-25) than the 

silver seatrout (26-27), and for fish 

lon er than 5 mm in standard length 

(SLY, the spot has fewer precaudal 

vertebrae (10) than any other species 

of Cynoscion. For specimens at least 

6 mm SL, spot have more anal fin 

pterygiophores (14-15) than the banded 

drum (8-10); individuals shorter than 

6 mm SL are not likely to co-occur 

with small spot larvae. (Pterygiophores are the skeletal elements of 

fin support.) The larvae of spot have 

fewer dorsal fin rays (29-35) and more 

anal fin rays (12-13) than any of the 

described species of Equetus (36-55 

and 5-8 rays, respectively). At 

about 4 mm SL, spot differ from the 

Atlantic croaker only in pigmentation. 

The spot has a large melanophore in 

the peritoneum anterior to the 

visceral mass between the cl ei thra, a 

triangular or diamond-shaped pigment 

pattern on the ventral abdomen, and a 

continuous pigment row along the anal 

fin base. The pigmentation differences between spot and Atlantic croaker 

are retained up to about 20 mm SL. 

Larvae of spot differ from those of 

Atlantic croaker in a number of other 

characteristics: by 4.0 mm SL, the 

eye diameter of spot is larger (>lo% 

of SL); by 7.0 mm SL, spot have more 

anal fin pterygiophores (14-15 vs. 

9-11); by 8.5 mm SL, spot have a 

shorter preanal length (<5% of SL); by 

20-30 mm SL in Atlantic croaker 

the mandibular barbels are evident in 

some specimens, and by 50 mm SL they are 

present in all. 

REASON FOR INCLUSION IN SERIES 

The spot is one of the most abundant demersal fishes in coastal waters 

of the South Atlantic Region, and is 

both commercially and recreational ly 

important. In commercial catch, this 

species in dollars or pounds has 

generally ranked among the top five 

finfish species. In addition, the 

spot is a popular sport fish, and the 

recreational catch may exceed the 

commercial catch. Because of its 

abundance, the spot is important as 

prey of other fishes and is a 

seasonal ly important component of 

estuarine and shelf fish assemblages. 

The spot depends on several different 

habitats during its life history 

(Figure 2), and it may provide a 

direct link for energy exchange 

between estuarine and nearshore marine 

environments (see Weinstein 1981). 
LIFE HISTORY 

Spawni ng 

In the South Atlantic Region, 

spawning occurs from October to March 

and peaks in December and January 

(Townsend 1956; Dawson 1958; Springer 

and Woodburn 1960; Powles and Stender 

1978; Lewis and Judy 1983; Warlen and 

Chester 1985). This spawning period 

is later than that in the Mid Atlantic 

Region (Pacheco 1962; Chao and Musick 

1977) and somewhat earlier than that 

in the northern Gulf of Mexico, where 

spawning begins in December and peaks 

in January and February (Pearson 1929; 

Nel son 1969). 

Spot typical ly migrate offshore 

to spawn in moderately deep water 

along the South Atlantic Region 

(Dawson 1958; Fahay 1975; Powles and 

Stender 1978; Lewis and Judy 1983). 

This behavior is similar to that of 

the species in other parts of its 

range (Nelson 1969; Fruge 1977; 

Berrien et a1 . 1978). A comparison of 

the frequency distributions of the 

lengths of spot larvae caught off 

Beaufort, North Carolina, indicates 

that spawning occurs over the outer 

she1 f throughout most of the spawning 

season but over the mid-shelf early 

and late in the spawning season 

(Warlen and Chester 1985). Off North 

Carolina most spawning probably occurs 

75-90 km offshore (Warlen and Chester 

1985). A limited amount of spawning 

has been documented in inshore waters 

(Smi th 1907 ; Pearson 1929; Hi 1 debrand 

and Cable 1930; Jannke 1971; Music 

1974). Spawning apparently occurs at 

all latitudes throughout the South 

Atlantic Region, at least as far south 

as Cape Canaveral , judging from the 

occurrences of small 1 arvae (Fahay 

1975). 

Spawning activity begins in fall, 

when ripening adults collect off 

beaches (Hi 1 debrand and Cable 1930; 

Roelofs 1954; Dawson 1958) and then 

begin to migrate southward shortly 

before or during their offshore 

spawning migration. Dawson (1958) 

suggested that spot migrating 

southward a1 ong South Carol i na beaches 

were the primary source of fish caught 

in the commercial haul -seine fishery. 

Spot from more northern waters may 

use coastal waters of the South 

Atlantic Region during winter as 

spawning or feeding grounds (Chao and 

Musick 1977). Spot tagged in 

Chesapeake Bay (Pacheco 1962) and 

Delaware Bay (Pearson 1932) have been 

recaptured off North Carol i na. 

There is little published 

information on the fate of spot after 

they are spent. Pearson (1929) 

suggested that few spot survive 

spawning; however, Gunter (1945) and 

Dawson (1958) coll ected spent fish. 

After spawning, adult spot may remain 

offshore, but they are rarely taken by 

bottom trawling in these areas (Wenner 

et a1 . 1979a, b, c, d, 1980). 

A1 though the spot spawns in fall 

and winter, it appears to spawn only 

in relatively warm water. Hettler and 

Powell (1981) reported that spot held 

in a laboratory spawned only at 

17.5-25.0 "C. Warlen and Chester 

(1985) collected young larvae (< 16 

days old) only at water temperatures 

higher than 19.3 "C. Fahay (1975) 

col 1 ected 1 arvae in waters with 

surface temperatures of 7.4-17.3 "C. 

The distribution of masses of warm 

water across the continental shelf may 

affect the spawning locations of spot 

during the course of the spawning 

season. 

There are no published accounts 

of the fecundity of spot in the South 

At1 antic Region. Dawson (1958) found 

77,000 and 84,000 potential ova in two 

females (unspecified size and state of 

maturity). Hildebrand and Cable 

( 1930) reported several different 

sizes of ova in ripening spot and 

suggested that individual fish may 

spawn repeatedly over a period of 

several weeks. The fecundity of spot 
in other parts of its range is also 

poorly known (Parker 1971). 

Eggs and Larvae 

Eggs of the spot are pelagic. At 

20 "C they hatch in about 48 h and the 

yo1 k sac and oil globule are absorbed 

within the next 5 days (Powell and 

Gordy 1980). There are no published 

accounts of the distribution of eggs 

from any part of the spot's range. 

This lack of data is related to the 

lack of adequate taxonomic descriptions of eggs of spot and other 

sympatric species of sciaenids. 

The larvae of spot are widely 

distributed along the South Atlantic 

Region during late fall and early 

winter; however, the size distribution 

and relative abundance vary across the 

continental shelf (Powles and Stender 

1978; Lewis and Judy 1983; Warlen and 

Chester 1985). A1 though size 

general ly increases (and re1 ative 

abundance decreases) in nearshore 

areas (Lewis and Judy 1983; Warlen and 

Chester 1985), small larvae have been 

collected in nearshore waters early 

and late in the spawning season 

(Warlen and Chester 1985). 

The mechanisms by which spot 

larvae are transported to estuarine 

nursery areas from the offshore 

spawning grounds are not known; 

however, both active behavior and 

passive transport mechanisms have been 

demonstrated in other species of 

fishes (Norcross 1983; Norcross and 

Shaw 1984). Because the eggs and 

larvae of spot are buoyant and usually 

near the surface of the water, the 

offshore distributions of early life 

history stages may be affected by 

Ekman transport, tides, and temperature (see Norcross and Shaw 1984). 

Wind-induced Ekman transport may 

initially affect the abundance of 

1 arvae in offshore waters; however, 

1 arvae become more demersal during 

later stages (Hildebrand and Cable 

1930; Lewis and Judy 1983). As later 

larval stages settle out of the upper 

water column, they probably become 

less affected by Ekman transport and 

are more affected b other forces 

(inertia and ~oriolisf that occur at 

greater depths (Lewis and Judy 1983). 

The 1 i m i t e d swimming abi 1 i ty of small 

sciaenid larvae (0.25-1.0 m/s for 

brief periods; Lewis and Judy 1983) 

suggests that spot larvae move into 

estuaries primarily by drifting. 

Larvae 10-24 mrn SL first appear 

in coastal estuaries in January 

(Hildebrand and Cable 1930; Music 

1974; Lewis and Judy 1983), but 

movement into estuaries probably peaks 

in February and March (Dawson 1958; 

Hildebrand and Cable 1930; Music 1974; 

Meinstein et al. 1980a). Because of 

the extended spawning season, larval 

and juvenile spot continue to enter 

many estuaries throughout the first 

half of the calendar year. This prolonged spawning and recruitment period 

may provide a buffering effect against 

unusual climatic conditions. 

Warlen and Chester (1985) found 

that larvae and postlarvae (fish that 

have not completed metamorphosis to 

the juvenile stage, and are still 

planktonic) entered North Carol ina 

estuaries at ages of 40-74 days (mean 

= 59 days). They observed little 

within-sample variation in age, and 

hypothesized that spot entered the 

estuary in somewhat distinct age 

cohorts. In addition, small individuals arrived at the estuary near both 

the beginning and end of the recruitment period; this occurrence probably 

is a result of nearshore spawning at 

both the beginning and end of the 

spawning season or from more rapid 

transport mechanisms at these times. 

Postlarval spot entering Chesapeake 

Bay appear to be somewhat older 

(Joseph 1972) than spot migrating into 

estuaries in North Carolina. This 

observation provides additional evidence that populations in the Mid 

Atlantic Region may use the South 

Atlantic Region for spawning. 
Temperature may affect the 

ingress of larvae and postlarvae to 

estuaries; however, the roles of 

temperature and other environmental 

factors are not well known. Swimming 

speeds of spot larvae and juveniles 

have been positively correl ated with 

temperature (Rul ifson 1977). In 

addition, some early workers observed 

mass mortal ity of spot during periods 

of low water temperatures (5-10 "C), 

although it has been suggested that 

larvae and postlarvae may be more 

tolerant than older fish to such 

temperatures (Hildebrand and Cab;e 

1930; Dawson 1958; Hodson et al. 

1981a). 

The relative importance of 

passive and behaviorally mediated 

transport of larvae within estuaries 

is poorly understood. Because peak 

recruitment for winter-spawned larvae 

in most Atlantic coast estuaries 

occurs at a time when estuarine 

thermal stratification and tidal 

exchange ratios are at' a yearly 

maximum, active migration and use of 

tidal water movements are be1 ieved 

important in the dispersal of spot and 

other estuarine species (Weinstein et 

al. 1980a). During migration in the 

Cape Fear River (North Carolina) 

estuary, post1 arval and juvenile spot 

occur in the middle and lower layers 

of the water column during the day and 

concentrate near the surface at night 

(Lewis and Wilkens 1971; Weinstein et 

a1 . 1980a). This behavior may enable 

spot to use tidal currents to augment 

their lateral movement into the shallow areas of estuaries (Weinstein 

1979). In another study, Weinstein et 

al. (1980b) found that abundance of 

small spot in ichthyopl ankton col lections was much lower near the mouths 

of tidal creeks than in areas closer 

to the headwaters in the Cape Fear 

estuary. Spot, thus, appeared to congregate in the shallow-water portions 

of estuaries. Unfortunately, behavioral mechanisms that augment movement 

in some estuaries do not always apply 

in other estuaries having different 

hydrographic characteristics. 

Postlarval spot have been 

col 1 ected in 1 arge numbers throughout 

estuaries and apparently are tolerant 

of a wide range of physical, chemical, 

and biotic factors. Simi 1 ar numbers 

of spot have commonly been collected 

during the period of peak recruitment 

in estuarine areas having very 

different physicochemical conditions 

(Weinstein 1979; Bozeman and Dean 

1980; Rogers et al. 1984; and Rozas 

and Hackney 1984). Some studies 

(Kilby 1955; Reid 1957; Weinstein 

1983; Weins tein and Brooks 1983) have 

suggested that other habitat features 

such as substrate and sea grass beds 

are important in determining the 

distribution of spot in localized 

areas. 

Several investigators have studied 

the effects of river discharge 

(especially high water conditions) on 

the recrui tment of spot and estuarine 

community structure. Weinstein et al. 

(1980a) reported that, a1 though 

postlarvae were absent in sections of 

the main channel of the Cape Fear 

River during high water, the fish 

recovered rather rapidly to pre-high 

water densities. The structural 

patterns of the shall ow-water fish 

assemblages in the Cape Fear River 

estuary were not affected by annual 

differences in river discharge 

(Weinstein et al. 1980b). Rogers et 

a1 . (1984) concluded that recruitment 

of spot and other fishes may be 

inhibited during discharge peaks of 

the Ogeechee River in Georgia, but 

that upper-estuary nursery areas were 

used during high water. Kobyl inski 

and Sheridan (1979) found no correlation between the abundance of spot 

and annual variation in river discharge in Apal achicola Bay, Florida. 

Juveni 1 es and Adul ts 

Juvenile spot that have congregated in the shallow water of tidal 

creeks tend to disperse as they 

increase in size (Weinstein and 

Wal ters 1981) ; this emigration into 

deeper waters after growth appears 
to occur throughout estuaries (Herke 

1971; Chao and Musick 1977), and 

results in the size-specific use of 

shallow estuarine habitats (Turner and 

Johnson 1973; Weinstein et al. 1980b; 

Rogers et al. 1984). Differences in 

gear bias (Kjelson and Johnson 1978), 

sampl ing methods, and experimental 

design have probably contributed to 

reports that various size classes of 

spot are ubiquitous in estuarine 

areas. 

Juvenile spot live in different 

habitats for different periods of time 

(Weinstein 1983; Weinstein and Brooks 

1983; Rozas and Hackney 1984). Tagged 

individuals remained in tidal creeks 

of the York River estuary for an 

average of 91 days, and the population 

remained there as long as 6 months 

(Weinstein 1983). This observation 

suggests that the exchange of juvenile 

spot between marsh habitats is 

relatively minor during the first 

summer. In another study, Rozas and 

Hackney (1984) concluded that the 

period of residency is much shorter in 

oligohaline marshes of the Cape Fear 

River. It is not known whether these 

differences are related to the productivity or structural complexity of the 

habitat. Older fish may be "tracking" 

their epibenthic and infaunal food 

supply in the estuary, or they may be 

moving to avoid increased predation by 

wading birds and crabs in shallow 

water (Weinstein and Brooks 1983). 

Large juveni 1 es apparently move 

into deeper portions of estuaries. 

Trawling in South Carolina (Shealy et 

al. 1974) and Georgia (Music 1974) 

resulted in the capture of large 

numbers of advanced juveniles in late 

summer and fa1 1. Young-of-the-year 

spot overwinter in the deeper portions 

of most estuaries (Music 1974; Chao 

and Musick 1977). Relatively 1 ittle 

is known about the importance of 

environmental factors, habitat features, and biological processes in 

determining the distribution and 

movements of juveniles. 

The distribution patterns of some 

estuarine fishes have recently been 

ascribed to differing mortal ity rates 

in various parts of estuaries (Polgar 

1982). Weinstein and Wal ters (1981) 

suggested that a similar phenomenon 

may explain the distribution of young 

spot in the Cape Fear estuary. 

Mortality was higher in polyhaline 

tidal creeks than in less saline 

creeks due to the presence of 

seasonal ly abundant marine predators. 

GROWTH CHARACTERISTICS 

Length-Weight Relationship 

Dawson (1958) reported the 

following relationship between weight 

(W, in grams) and standard length (SL, 

in millimeters) for spot 45-205 mn 

long in South Carolina: loglOW = 

-4.544 + 2.958 loglOSL. He also 

determined that total length (TL) 

could be calculated from standard 

length as TL = 1.233 SL + 2.0 mm. 

Larvae and Postlarvae 

Warlen and Chester (1985) counted 

daily growth increments on otol i ths 

(sagitta) to determine the age and 

growth history of larvae and postlarvae collected off Beaufort Inlet, 

North Carolina, during fall and winter 

in 1978-1980. Growth of young spot 

was biphasic; it was rapid in the 

ocean and appeared to coincide with a 

winter peak of plankton productivity 

(Turner et al. 1979; Yoder et al. 

1981), slowed during the early months 

of estuarine residence (unti 1 about 

Apri 1 ) , and then accelerated after 

metamorphosis of 1 arvae to the 

juvenile stage, at lengths of about 25 

mm SL. 

Warlen and Chester (1985) found 

no significant differences in growth 

rates between years. Age-speci fic 

growth rates declined from 5% per day 

at age 10 days to <1% per day at age 

90 days. Back-calculated lengths at 
each age were significantly greater in 

older than in younger fish of the same 

cohort, leading the authors to suggest 

that size-sel ective mortal i ty favored 

survival of faster growing 1 arvae. 

Weinstein and Walters (1981) also 

found that growth rates of postlarvae 

in the estuary were slow in late 

winter and early spring. The long 

recruitment period of spot necessitated a complicated methodology for 

measuring growth; however, estimated 

average daily growth rates of 0.14- 

0.16 mn/day in the Cape Fear River 

estuary (Weinstein and Wal ters 1981) 

were similar to the 0.1% specific 

growth rate for late larval and early 

juvenile spot entering Beaufort Inlet 

estuary (Warlen and Chester 1985). In 

addition, the sizes of postlarvae 

coll ected early in their estuarine 

residency correspond closely to the 

asymptote predicted by the Gompertz 

growth equations for larvae, derived 

by Warlen and Chester (1985). This 

observation indicates that larvae may 

enter estuaries at a similar size 

throughout the South Atlantic Region. 

Juveniles and Adults 

In early studies from the 

Atlantic coast and Gulf of Mexico, 

somewhat variable estimates of spot 

growth rates were shown (Table 1). 

Many studies probably underestimated 

growth because of the protracted 

spawning season, the extended 

recruitment period, si ze-dependent 

emigration, and biased sampl ing 

methods (Herke 1971). In addition, 

the use of scales to age spot was 

admitted to be problematic, or not 

validated, in some studies (Welsh and 

Breder 1923; Pacheco 1962). 

Estimates of the growth of spot 

in the South Atlantic Region show good 

agreement. Using modal analysis of 

the lengths of fish caught in South 

Carol ina, Dawson (1958) found that 

spot reached 115-130 mm SL in their 

first year of growth and 150-175 mn SL 

in their second year. Using the same 

method, Music (1974) estimated that 

spot attained lengths of 140-145 mm TL 

(about 110-115 mm SL) during their 

first year in Georgia estuaries. 

Welsh and Breder (1923) assigned a 

total length of 140 mm TL to age I 

spot at Fernandina Beach, Florida. 

Weinstein and Wal ters (1981) found 

that spot reached at least 100 mm SL 

by September of their first year in 

the Cape Fear estuary. 

Growth rates show seasonal and 

annual variation. Growth in young 

juveniles is ra i d i n late spring and 

early sumner f Weinstein and Walters 

1981), but juvenile and adult spot 

grow very slowly during winter (Dawson 

1958; Pacheco 1962). Weinstein and 

Walters (1981) found that growth of 

spot in the Cape Fear estuary was 

rapid in late sumner in 1978 but 

depressed during the sumner of 1977. 

High temperatures in July 1977 reduced 

feeding and retarded growth to the 

extent that the ultimate sizes 

achieved by the spot at the end of the 

growing season that year may have been 

comparatively small. 

Size and Age at Maturity 

The smallest size at which 

advanced gonadal development was 

observed was 170-175 mm TL (Dawson 

1958; Music 1974). Other researchers 

indicated that spot reach sexual 

maturity at sizes of 185-210 mn TL 

(Hi ldebrand and Schroeder 1928; 

Hildebrand and Cable 1930; Gunter 

1945; Townsend 1956). Music (1974) 

indicated that males may mature at a 

slightly smaller size (170 mn TL) than 

females (205 mm TL) . 

Most spot reach sexual maturity 

in 2 years; but some may require 3 

years. Some adults are captured in 

estuaries throughout the year (Music 

1974; Shealy et al. 1974; Chao and 

Musi ck 1977). Length frequency 

distributions of spot caught by 

trawling led Dawson (1958) to conclude 

that most fish that spawned off South 

Carolina were 2 or 3 years old. 
Table 1. Total length (mm) of spot at different ages, in different areas. 

Age 

Area I I I I11 Source 

New Jersey 165-220 240-290 We1 sh and Breder 1923 

Chesapeake Bay Hildebrand and 

Schroeder 1928 

Beaufort, North 

Carol ina 

Hi 1 debrand and 

Cable 1930 

Chesapeake Bay 195-270 Pacheco 1962 

Glynn County, 

Georgia 

224 242 Music and Pafford 1984 

Fernandi na , Welsh and Breder 1923 

Florida 

Alligator Harbor, 

Florida 

190-230 Townsend 1956 

Lake Pontchartrai n, 

Louisiana 

200-210 225 Sundara j 1960 

Lake Borgne, Parker 1971 

Louisiana 

Laguna Madre, 

Texas 

190-210 Pearson 1929 

Gal veston Bay, 

Texas 

Parker 1971 

Gunter (1945) and Townsend (1956) 

reported similar findings for the Gulf 

of Mexico . 

reports of the U.S. Fish and Wildlife 

Service show that the commercial catch 

of spot has fluctuated widely since 

1939 and was too sporadic to support a 

we1 1 -developed fishery in most states 

along the Atlantic seaboard. The 

commercial catch has been consistently 

high only in the Carolinas and 

Virginia, where nearly 75% of the 

total annual catch is made. 

THE FISHERY 

History 

Historical data available in 

publications of the U.S. Bureau of 

Commercial Fisheries and statistical 

Spot are taken in large numbers 

in fa1 1 by haul-seine fishermen along 
the beaches of North and South 

Carolina. Catches consist predominantly of maturing adults that are 

beginning to migrate offshore to 

spawn. From April to October 1979, 

spot was the most abundant fish 

species by number (44%) and weight 

(40%) caught by long haul -seine fishing in Pam1 ico Sound, its tributaires, 

and Core Sound, North Carolina 

(DeVries 1982). Most of these spot 

were age I or 11. Spot are also taken 

by shrimp trawlers, but the fish are 

usually small and useful only for pet 

food or fish meal; sometimes they are 

discarded. Spot are sought by sport 

fishermen because they take bait 

readily and can be caught near 

bridges, piers, and wharves. Small - 

scale commercial gill -netters also 

catch substantial numbers of spot in 

fall in Sout'h Carolina (E.B. Joseph, 

South Carolina Wild1 ife and Marine 

Resources Department, Char1 eston, 

pers. comm.). 

In the 19701s, the commercial 

catch of spot ranged from 3 to 11 

mill ion pounds with a value of 

$400,000 to $1,275,000 (Table 2). 

Most of this catch was taken with haul 

seines, and some of it with otter 

trawls, pound nets, gill nets, and 

hook-and-line. There has been no 

steady trend in the catches with 

time--a feature characteristic of 

short-lived species. Most of the 

catch has consisted of 2- and 3-year 

old fish. 

In the late 1970'~~ the 

recreational harvest of spot was about 

907 metric tons (2 million pounds 

annually) (National Marine Fisheries 

Service 1980, 1984), but the catch may 

be much larger. In 1982 over 6.7 

milllon spot weighing 559 metric tons 

(1.2 mill ion pounds) were caught by 

marine recreational fishermen in the 

South Atlantic Region (NMFS 1985). 

Trends are difficult to define because 

surveys have been inadequate in some 

years, and methods have occasionally 

changed. The recreational catch 

is also composed mostly of 2- and 

3-year old fish. 

Management 

There are no current state or 

federal restrictions on the commercial 

or recreational catch of spot. 

Population Dynamics 

Population levels of spot 

fluctuate tremendously; such changes 

are typical of species with short life 

spans. Year-class strength is probably determined during the larval and 

post1 arval stages (Norcross 1983) ; 

however, estimates of mortality for 

the larval stage have not been 

reported. 

Weinstein and Wal ters (1981) 

found that rates of mortality in 

postlarval and juvenile spot varied 

among years and among areas. 

Mortality was significantly higher in 

1977 than in 1978 in polyhaline 

marshes due to predation by the 

Atlantic silverside, Menidia menidia, 

and the striped kill ifish, Fundulus 

majal is. High mortal i ty rates 

observed in 1978 in 01 iaohal ine 

marshes were be1 ieved due to eitremely 

high freshwater flows in winter and 

spring, which displaced spot from 

their preferred habitats. 

No information is available on 

the status or structure of populations 

in the South Atlantic Region. Given 

the short life span of the species, 

the extensive offshore spawning 

grounds, and the prolonged spawning 

period, it is likely that spot 

inhabiting the South Atlantic Region 

compose a single population. 

ECOLOGICAL ROLE 

Food and Feeding Habits 

Spot display two distinct feeding 

modes. Larvae are size-selective 
Table 2. Commercial landings (thousands of pounds) of spot, and catch values 

(thousands of dollars) in the South Atlantic Region from 1969 to 1977 (National 

Marine Fisheries Service 1972, 1974, 1975a,b, 1976, 1978a,b, 1980, 1984). 

North Carol i na South Carolina Florida 

Year pounds value pounds value pounds value 

plankton feeders, and juveni 1 es and 

adults are predators on infaunal and 

epibenthic invertebrates. There have 

been no studies to date of the feeding 

habits of larval spot in the South 

Atlantic Region, but general patterns 

may be inferred from studies in the 

northern Gulf of Mexico (Govoni et al. 

1983). Larvae initially eat small 

prey (tintinnid ciliated protozoans, 

invertebrate eggs, and copepod 

naupl ii) and then eat progressively 

1 arger food ( 1 arval pel ecypods, copepodi tes , pteropods , and adul t copepods) as they grow to 10-15 mm SL. 

Larvae of all sizes seemingly feed 

diurnally (Govoni et a1 . 1983). 

Regional differences in the diets 

of larval spot appear to reflect prevailing hydrographic conditions. 

Larvae col lected near river mouths had 

fed on taxa typical of estuarine 

waters and 1 arvae col 1 ected offshore 

had fed on taxa representative of more 

oceanic areas (Govoni et al. 1983). 

Regardless of geographic area, major 

prey categories remai ned fairly 

simi 1 ar. 

'The zooplankton of the South 

Atlantic Region sometimes shows tremendous geographic variation (Bowman 

1971), due in part to the periodic 

intrusion of cold-water upwellings 

onto the continental shelf. The diets 

of 1 arval spot, therefore, probably 

vary according to geographic distribution of the zooplankton. Differences 

in diets associated with upwell ings 

may affect the survival of larval 

spot; however, the larvae have relatively high assimilation efficiencies, 

and dependence on zooplankton patches 

appears to be less than that of some 

other abundant fishes (Govoni et al. 

1982, 1985). 

Postlarval spot entering the 

estuary apparently feed much like 
larvae. Early accounts showed that 

individuals up to 25 mm SL fed 

primarily on planktonic copepods and 

ostracods (Welsh and Breder 1923; 

Hi 1 debrand and' Schroeder 1928; Hi 1 debrand and Cable 1930). Postlarval 

spot, 17-24 mm SL, fed mainly on 

copepods (mostly Harpacticoida, 

spp., Temora spp., and 

in the Newport River 

estuary (Kjelson et al. 1975). 

Postlarvae feed throughout day1 ight 

hours (Kjelson et al. 1975; Peters and 

Kjel son 1975). but feedinq rates are 

highest in late morning (kjelson and 

Johnson 1976). Field and laboratory 

data have indicated that the size of 

prey increases with the size of the 

postlarvae (Kjelson and Johnson 1976). 

The transformation from postlarvae to juveniles (at about 25 mn 

SL) marks a change from a sightfeeding planktivore to a partly 

01 factory-dependent benthic feeder. 

The bodies of transforming postlarvae 

become deeper, their mouths and eyes 

small er, and their sensory appendages 

more developed (Chao and Musick 1977). 

The diet of large postlarvae and small 

juveniles reflects this change; small 

juveni 1 es prey on i nsect 1 arvae, 

polychaetes, harpacticoid copepods, 

and other crustaceans (Welsh and 

Breder 1923; Hildebrand and Cable 

1930; Roelofs 1954; Townsend 1956; 

Stickney et al. 1975; Sheridan 1979; 

Hodson et a1 . 1981b). 

Juveni 1 es seemingly switch to 

nocturnal feeding shortly after transformation, which may be a strategy for 

predation avoidance (Hodson et a1 . 1981b). Recent evidence attributes 

some distribution patterns to differential mortality due to size-selective 

predation (Pol gar 1982). Another 

possible explanation for nocturnal 

feeding may involve avoidance of high 

daytime temperatures in shallow marsh 

areas (Hodson et al. 1981b). Finally, 

prey availability may be much greater 

at night than during the day because 

many invertebrate prey species are 

nocturnal . 

Plant material and detritus noted 

in stomachs of juvenile and adult spot 

probably provide 1 i ttle nutritional 

value because spot lack cellulase 

activity in their gut (Stickney and 

Shumway 1974). However, the microbial 

flora associated with this material 

may provide some nutritive value 

(Cammen et al. 1978). This material 

is probably ingested incidentally, as 

juveniles and adults occasionally feed 

by scooping up or diving into the 

substrate (Roelofs 1954; Chao and 

Musick 1977). 

Diets of larger juveniles are 

variable. Studies within the South 

Atlantic Region (Stickney et al. 1975, 

Hodson et al. 1981b) showed no pattern 

in the diet of spot, and similar 

findings have been reported in other 

areas (Sheridan 1979). Regional 

differences in the diets are probably 

due to differences in the availability 

of prey in the variety of habitats in 

which spot 1 ive. 

The prey of adults in estuarine 

or coastal waters of the South 

Atlantic Region has not been reported, 

but adult spot probably feed much as 

they do in other areas. Chao and 

Musick (1977) reported that adult spot 

in Chesapeake Bay were nocturnal 

predators on zooplankton, benthic 

infauna, and epifauna. Organisms most 

frequently consumed were polychaetes 

(mostly Pectinaria gouldi i, Glycinde 

sol i taria, Amphi tri te spp., Nereis 

succinea, and Ne th s spp.), amphipods 

ws spp.)Jmaceans, gastropods,ecypods , nematodes, the mysid 

~eomysis americana, and several copepods. Livingston (1984) reported 

similar findings for two populations 

of spot in the Gulf of Mexico. 

Production and Energetics 

Because spot migrate offshore in 

fa1 1, their production may represent a 

considerable energy exchange between 

estuarine and she1 f ecosystems. 

Weinstein and Wal ters (1981) estimated 

production on a monthly basis from 
collections in the Cape Fear estuary. 

Estimates pooled from several sampl ing 

sites for the entire 7-month period of 

marsh residence for young-of-the-year 

resulted in a value of 0.17 g wet 

weight/m2. This was equivalent to 

0.05 g dry weight/m2 or 257 

calories/m2 (Weinstein and Wal ters 

1981). Adams (1976) estimated 

production for spot in two seagrass 

(Zostera marina) habitats at Bogue 

Sound andPhil 1 ips Island, North 

Carolina. His study included all age 

classes, though it probably emphasized 

young-of-the-year because of the 

winter and spring sampling periods. 

Monthly production estimates ranged 

from 37 to 356 calories/m2. These 

studies suggest that marshes and 

seagrass beds are similarly productive 

as nursery areas for spot. 

Estimates of the daily ration of 

postlarvae relative to the fish's wet 

body weight have ranged from 4.3% to 

9.0% (Kjelson et al. 1975; Kjelson and 

Johnson 1976). The lower ration 

estimates (4.3%) are less than some 

predictions of metabolic need based on 

oxygen consumption requirements 

(Kjelson et al. 1975; Kjelson and 

Johnson 1976) ; the discrepancy between 

the ration and metabolic need was 

believed to be due to an inadequate 

food supply during the sampling period 

(Kjelson et al. 1975). The higher 

daily ration estimates (9.0%) were 

obtained from larvae captured a year 

later, when the food supply was 

greater. Such findings support the 

critical period concept which maintains that year-class strength is 

determined by the availability of food 

after the larval yolk supply has been 

used (see May 1974), and are simi 1 ar 

to studies of other marine fishes 

(Houde 1978). The tremendous 

fluctuations observed in spot 

populations in the past (Joseph 1972) 

may thus be due to variations in 

survival of larvae. In addition, such 

estimates indicate that 1 arval and 

postlarval spot entering estuaries may 

significantly affect copepod popul ations (Thayer et al. 1974; Kjelson and 

Johnson 1976). 

Predation and Parasitism 

There is little published information about predation on spot. 

Because of their abundance and wide 

distribution they are probably preyed 

upon by a large number of other 

fishes. Weinstein and Wal ters (1981) 

reported that si lversides (Menidia 

spp.) preyed heavily on postlarvae in 

estuaries; their data suggested that 

predation affects distribution 

patterns of post1 arvae. 

Juvenile and adult spot are 

eaten by many other fishes, including 

striped-bass, Morone saxatil is; silky 

shark, Carcharhinus falciformis; 

seatrout, Cynoscion spp.;, 

Pomatomus saltatrix; mackerels, 

Scomberomorus spp.; longnose gar, 

Lepisosteus osseus; and flounders, 

Para1 ichth s spp.-(~oll is 1952; Dawson 

he 1978: Rozas and Hacknev 

Few external parasites of spot 

have been re~orted. The ~arasitic 

copepods ~ernaeenicus radiatus and 

Ergasi lus 1 izae (Dawsoni have 

been report-rom spot col 1 ec ted off 

South darolina and 'in the Gulf of 

Mexico, respectively. The marine 

leech ~~zobdella 

re~orted from 

The spot serves as host to many 

different types of internal parasites, 

including a microsporidean, Ichthyosporidium sp.; the monogenetic trematodes Tagia bairdiel la, Pedocot le 

minima, and Diclidophora cauda e is; the 

digenetic trematode Aphanurus sp.; and 

the acanthocephal an Telosentis 

tenuicornis (Koratha 1955; Bullock 

1957; Hargis 1957; Schwartz 1963; 

Sprague 1966; Sprague and Hussey 1980; 

Govoni 1983). 
ENVIRONMENTAL REQUIREMENTS 

Temperature, Sal inity, and Dissolved 

Oxygen 

Spot occur throughout a wide 

range of physicochemical conditions; 

however, relatively 1 i ttle is known 

about the effects of physicochemical 

conditions on different stages of 

spot. In most studies, only the 

limits of tolerance of a particular 

life stage to one or two environmental 

variables have been determined; 

virtual ly nothing is known about 

interactive or chronic effects. 

Tolerance to thermal shock and 

other environmental extremes varies 

with developmental stage (Hettler and 

Clements 1978; Hartwell and Hoss 1979; 

Hodson et al. 1981a). Laboratory 

studies indicated that spot embryos do 

not develop at temperatures be1 ow 14 

"C, but that larvae can tolerate 

temperatures as low as 5 "C (Hettler 

and Clements 1978). Burton (1979) 

reported that venti 1 ation rates 

indicative of cold stress occurred in 

juveniles held at 5 "C. Tolerance of 

spot eggs to thermal shock varies 

seasonally; the eggs are affected 

more by heat shock than are early 

embryos and larvae (Hettler and 

Clements 1978). The rate of postshock cooling also affected egg and 

1 arval mortal i ty; rapid cool i ng 

increased mortality. 

Early field observations (Hildebrand and Cable 1930; Dawson 1958) 

suggested that juveniles may be more 

to1 erant of 1 ow temperatures than 

adults. "Cold shock" has been 

reported in larval fish returned to 

accl imation temperatures fol 1 owing 

thermal shock (Hoss et al. 1974; 

Hettl er and Cl ements 1978). However, 

the temperature to1 erance of 1 arge 

juvenile and adult spot is not known. 

The upper temperature tolerance 

and the thermal shock tolerance of 

early life history stages also vary 

with a c c l i m a t i o n temperature (Hoss et 

al. 1974; Hettler and Clements 1978; 

Hartwell and Hoss 1979; Hodson et al. 

1981a). As a c c l i m a t i o n temperatures 

increase, tolerance to heat shock 

decreases. The upper temperature 

tolerance for postlarval and small 

juvenile spot is about 35 "C, 

depending on the size of the fish, its 

condition, and the accl imation 

temperature (Hodson et a1 . 1981a). 

Hodson et al. (1981a) found that 

as acclimation temperature increased, 

critical thermal maxima (CTM) of spot 

also increased. However, a significant interaction effect was evident 

between temperature and salinity, such 

that CTM values increased with 

decreased salinity at low acclimation 

temperature (10 "C), but decreased 

with decreasing salinity at high 

acclimation temperature (30 "C). Thus 

because young spot are initially 

accl imated to cold ocean temperatures, the decrease in salinity as 

they move into estuaries increases 

their CTM and tolerance to higher 

temperatures that often occur there. 

In addition, spot entrained in power 

plant cool ing water may have an 

increased chance of survival if that 

water is of low salinity (Hodson et 

al. 1981a). 

Sal ini ty may affect development 

of spot. Powel 1 and Gordy (1980) 

reared spot successfully at 30-35 

parts per thousand (ppt), and found 

only mi nor differences (probably temperature-re1 ated) between 1 aboratoryreared larvae and those collected in 

the South Atlantic Region and the Gulf 

of Mexico. Low salinities do not 

appear to be necessary for development 

and metamorphosis into juveni 1 es; 

however, the effects of salinity on 

survivorship of larvae and indirect 

effects on later stages are not known. 

Perez (1969) found that spot were more 

active at a higher rate of salinity 

change (10 pptlh) than at lower rates 

(5 pptlh, 1 pptlh) and suggested that 

spot may avoid areas with rapidly 

changing salinity. 
The tolerance of postlarval and 

juvenile spot to low oxygen concentrations is intermediate in comparison 

with other estuarine species (Burton 

et al. 1980; Subrahmanyam 1980; 

Neumann et a1 . 1981). Exposure of 90 

mm TL spot to a dissolved oxygen 

concentration of 0.8 mg/l for 96 h at 

27 "C resulted in 5% mortality; an 

oxygen concentration of 0.6 mg/l 

resulted in 95% mortality (Burton et 

al. 1980). These results should not 

be interpreted as indicating safe 

levels because the chronic effects of 

depressed oxygen levels on growth and 

survival are unknown. Concentrations 

greater than 0.6-0.8 mg/l could be 

below the tolerance level under 

conditions of increased activity, 

higher temperature, or other factors 

affecting metabol ism (Burton et a1 . 1980). A1 though the metabolic rate of 

spot is relatively low, their oxygen 

requirements (per unit body weight) 

may render them unfit to survive 

hypoxia in shallow tidal pools 

(Subrahmanyam 1980). 

Substrate and Svstem Features 

Spot use inshore estuarine and 

offshore marine environments during 

their ontogeny. Various 1 ife history 

stages are differentially distributed 

in estuaries and are critically 

dependent on different habitats. 

Thus, a1 terations of the sal i n i t y or 

temperature regimes of an estuary may 

have significant impacts on the 

pcpulation of spot in any particular 

estuary. Increased mortal ity or 

displacement and subsequent failure to 

recolonize some estuarine habitats 

have been observed after periods of 

altered river flow in North Carolina 

(Weinstein 1979; Weinstein and Brooks 

1983). 

Habitat a1 terations resulting 

from industrial effluents affect the 

abundance of spot in coastal seagrass 

systems (Livingston 1975, 1984). The 

composition and structure of the 

benthic community upon which larger 

spot feed were substantially altered, 

and the size-specific feeding patterns 

of spot were changed. 

Studies by Kil by (1955), Springer 

and Bull is (1956), and Simmons (1957) 

suggested that substrate features are 

important in affecting the distribution of spot. Data from offshore 

cruises (Springer and Bull is 1956) 

showed higher catches over mud and 

sand bottom than over live bottom 

(sponge-coral ) areas. In estuaries, 

spot appear to prefer substrates with 

lower organic content than those 

preferred by some other species of 

sciaenids (Weinstein 1979). Because 

current patterns affect settl i ng of 

organic and inorganic particulates , a1 teration of the current patterns in 

estuaries may a1 ter substrate features 

and other characteristics sufficiently 

to affect the distribution of spot and 

other estuarine species. Not all such 

changes may be harmful to the population of spot in any particular area; 

however, the effects in any given area 

would be difficult to predict. 

Contaminants 

Many pesticides, herbicides, 

heavy metals , and chlorination byproducts have been found to have signif icant lethal or sublethal effects 

on a17 stages of the life history of 

spot. Developing eggs and larvae may 

be especially sensitive to environmental contaminants (Engel and Sunda 

1979). Furthermore, because of their 

relatively long residence period in a 

particular tidal creek and the adjacent marsh (Weinstein 1983), postlarval and juvenile stages may be 

repeatedly exposed to various 

contaminants. 

Several heavy metal s (copper, 

lead, cadmium, and mercury) are known 

to be toxic to various life stages of 

spot (Engel and Sunda 1979; Hawkins et 

a1 . 1980), but no one has investigated the effects of a given metal on 

a1 1 developmental stages. Different 

metal forms (ions, free metal, etc.) 
vary in toxicity and may change within 

estuaries. Copper ions inhibit 

hatching and development of spot 

(Engel and Sunda 1979), and cadmium 

levels of 10 parts per million (ppm) 

cause renal failure and death of 

juveniles (Hawkins et al. 1980). The 

toxicity of some metal s to phytopl ankton and invertebrates (Sunda and 

Guillard 1976; Anderson and Morel 

1978; Sunda et al. 1978) may have 

deleterious effects on early life 

history stages of spot that rely on 

these organisms for food. 

Many pesticides and herbicides 

have lethal and sublethal effects on 

spot (Bahner et al. 1977; Schimnel and 

Wilson 1977; Stehlik and Merriner 

1983). Runoff from agricultural 1 ands 

has caused widespread as well as 

localized fish kills in several South 

Carolina estuaries (J. Settle, South 

Carol ina Wi ldl ife and Marine Resources 

Commission, Char1 eston, pers. comm.) . Agrochemical s have been imp1 icated in 

fish kills in many estuarine areas 

(Stehlik and Merriner 1983). Sublethal quantities accumulating through 

chronic exposure can produce skeletal 

deformities. Many of these compounds 

are relatively persistent in the 

aquatic environment, as they remain in 

sediments and animal tissues for long 

periods. Because spot appear to 

remain in a particular creek or area 

of marsh throughout most of the summer 

growth period, they may be more 1 i kely 

than many other estuarine fishes to 

suffer from repeated exposure to 

these compounds. 

Chl ori ne-produced oxidants (CPO) 

from secondary sewage treatment wastes 

and e l e c t r i c generating pl ants a1 so 

can have significant deleterious 

effects on juvenile spot (Tsai 1968; 

Middaugh et al. 1977, 1980). High 

concentrations (>0.13 mg CPO/liter) 

were acutely toxic in flowing water 

tests conducted at 29-31 OC and 

salinities of 26-31 ppt. Sublethal 

concentrations (<0.12 mg CPO/l i ter) 

depressed feeding during an 8-day 

period of exposure (Middaugh et al. 

1980). It is not known whether such 

sub1 ethal concentrations affect 

growth. The toxicity of bromochl orinated seawater to spot appears to be 

greater than that of chlorinated 

seawater. At high operating levels, 

some sewage treatment plants may 

re1 ease quantities of bromochl orinated 

sewage sufficient to cause death of 

juveni 1 e spot (Roberts and Gl eeson 

1978; Roberts 1980). Not all stages 

of spot have been examined with regard 

to toxicity, and almost no information 

is available about the effects of 

longterm exposure of spot to these 

compounds. 

Other Factors 

Spot have significantly slower 

swimming speeds than other abundant 

estuarine fishes (Hettl er 1979). 

Small spot (<2.7 cm SL) cannot maintain their orientation in currents 

exceeding 15 cm/s, and somewhat larger 

spot (2.5-5.0 cm SL) cannot maintain 

their orientation in currents exceeding 30 cm/s (Rulifson 1977; Hettler 

1979). These low swimming speeds and 

endurance levels could result in 

significant mortal i ty of spot caught 

in intake structures at industrial or 

power generating plants. 

Swimming and orientation behavior 

of spot vary with size. Spot <5 cm SL 

orient into weak currents (<I5 cm/s), 

whereas larger spot drift with them. 

Thus, despite their increased swimming 

capabil ities, the larger spot are also 

vulnerable to impingement on intake 

structures (Rul ifson 1977). A1 terations in the design or careful placement of intake structures may reduce 

impingement and entrainment of spot. 
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eel grass, Zostera marina, fish 

communities. 11. Functional ~ . ~ 

analysis. J. Exp. Mar. Biol. Ecol. 

22:291-311. 

Anderson, D.M., and F.M.M. Morel. 

1978. Copper sensitivity of 

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Goodman, and G.E. Walsh. 1977. 

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estuarine food chains. Chesapeake 

Sci . 18: 299-308. 

Berrien, P.L., M.P. Fahay, A.M. Kendall , Jr., and W.G. Smith. 1978. 

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1953. Fishes of the Gulf of Maine. 

U.S. Fish Wildl. Serv. Fish. Bull. 

74: 1-577. 

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Smithson. Contrib. Zool. No. 96. 58 

PP. 

Bozeman, E .L., and J .M. Dean. 1980. 

The abundance of estuarine 1 arval 

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Sci. Univ. Texas 4:278-283. 

Burton, D.T. 1979. Ventilation frequency compensation responses of 

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exposed to moderate temperature 

increases. J. Fish Biol . 15:589-600. 

Burton, D.T., L.B. Richardson, and 

C.J. Moore. 1980. Effect of oxygen 

reduction rate and constant 1 ow 

dissolved oxygen concentrations on 

two estuarine fish. Trans. Am. 

Fish . Soc. 109: 552-557. 

Cammen, L., P. Rublee, and J. Hobbie. 

1978. The significance of microbial 

carbon in the nutrition of the polychaete Nereis succinea and other 

aquatic deposit feeders. Sea Grant 

Publ . UNC-SG-78-12, University of 

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classifying western Atlantic 

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Chao, L.N., and J.A. Musick. 1977. 

Life history, feeding habits, and 

functional morphology of juvenile 

sciaenid fishes in the York River 

estuary. U.S. Natl. Mar. Fish. 

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spot ,-~eiostomus xanthurus- Lacepede, 

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Dep. Contrib. Bears Bluff Lab. No. 

28. 48 pp. 

DeVane , J .C. . Jr. 1978. Food of kina 

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50272 -101 

REPORT DOCUMENTATION 1. REPORT NO. 2. 

PAGE i3ioloqical Report 82111.91)* 1 3. Rec~p~eni's Accesston No. 

I, I I 

4. Title and Subtltla 5, Reoon Data 

Species Profiles: Life Histories and Environmental Requirements 

of Coastal Fishes and Invertebrates (South At1 antic)--Spot 

7. Author(%) 

L. S. Hales and M. J. Van Den Avyle 

9. Performing Organization Name and Address 10. PmlectlTasklWorh Unit No. 

Georgia Cooperative Fish and Wildlife Research Unit 

School of Forest Resources 

University of Georgia 

12. 

Athens, 

Soonsoring Or@anizatlon 

GA 30602 

Name and Address 

-- 

National Wetlands Research Center U.S. Army Corps of Engineers 

Fish and Wildlife Service Waterways Experiment Station 

U.S. DepartmentoftheInterior P.O. Box631 

Washington, DC 20240 Vicksburg, MS 39180 

Contract(C) or Grant(G1 No. 

13. Type of Repon 6 Period Coven 

IS. Supplementary Notes 

, *U.S. Amy Corps of Engineers Report No. TR El-82-4 1 16. Abstract (Limit: 200 words) 

Species profiles are 1 iterature sumraries of the 1 ife history, distribution, and 

environmental requirements of coastal fishes and invertebrates. Profiles are prepared 

to assist with environmental impact assessment. The spot (Leiostomus xanthurus) is an 

abundant fish in coastal waters of the South Atlantic Region. It is important to 

commercial and recreational fisheries. In the South Atlantic Region, spot spawn 

offshore from October to March. The larvae are transported from the offshore spawning 

grounds to estuarine nursery areas. Juvenile spot initially conoreCate in shallow 

tidal creeks, but then disperse into deeper water as they get larger. Spot mature at 

2-3 years of age. As larvae, spot feed on plankton, but switch to benthic invertebrates 

as juveniles and adults. Juvenile and adult spot are eaten by many other fishes. 

Tolerance to thermal shock and other environmental extremes varies with developmental 

stage. Alterations of the salinity or temperature regimes of an estuary may affect 

populations of spot; disturbances that affect the benthic community upon which spot 

feed may also affect spot abundance. Spot are not strong swimmers and may, therefore, 

suffer significant mortality due to intake structures at industrial or power 

generation plants. 

17. Document Analysis a. Deacripton 

Estuaries 

Fi shes 

Growth 

Feeding habi ts b. IdentlRenlOPen.Ended Terms 

Spot Temperature requi remen ts 

Leiostomus xanthurus Spawni ng 

Habitat Fisheries 

Salinity requirements c. COSATI FieldlCroup 

18. Availability Statement I 19. Sacurnty Class Chis ReooR) 

Unlimited Distribution 20. Sacur~ty Class Chis Page) 

Unclassified 

21. No. of Pagas 

24 -- 22. Price 

(See ANSI-239.18) OPTIONAL FORM 272 (4-7; 

(Formerly NTIS-31) 

Dopanmant d Cornmarc- 
As the Nation's principal conservation agency, the Department of 

the Interior has responsibility for most of our nationally owned 

public lands and natural resources. This includes fostering the 

wisest use of our land and water resources, protecting our fish 

and wildlife, preserving the environmental and cultural values of our 

national parks and historical places, and providing for the enjoyment of life through outdoor recreation. The Department assesses 

our energy and mineral resources and works to assure that their 

development is in the best interests of all our people. The Department also has a major responsibility for American Indian reservation 

communities and for people who live in island territories under U.S. 

administration. 

U.S. DEPARTMENT OF THE INTERIOR 

FlSH AND WILDLIFE SERVICE 

TAKE PRIDE 

in America 

UNITED STATES 

DEPARTMENT OF THE INTERIOR 

FlSH AND WILDLIFE SERVICE 

National Wetlands Research Center 

NASA-Slidell Computer Complex 

101 0 Gause Boulevard 

Slidell, LA 70458 

MAaE AND RE8 PAID 

UA DEPARTMENT Of THE INTERIOR 

INT-423 

OFFICIAL BUSINESS 

PENALTY FOR PRIVATE USE, 5300