Biological Report 82(11.109) 

August 1989 

Species Profiles: Life Histories and 

Environmental Requirements of Coastal Fishes 

and Invertebrates (Mid-Atlantic) 

WEAKFISH 

Fish and Wildlife Service 

Coastal Ecology Group 

Waterways Ex~eriment Station 

U.S. Department of the Interior U.S. Army Corps of Engineers 
Biological Report 82( 11.109) 

TR EL-82-4 

August 1989 

Species Profiles: Life Histories and Environmental Requirements 

of Coastal Fishes and Invertebrates (Mid-Atlantic) 

WEAKFISH 

Linda P. Mercer 

North Carolina Division 

of Marine Fisheries 

Morehead City, NC 28557 

Project Officer 

David Moran 

U.S. Fish and Wildlife Service 

National Wetlands Research Center 

1010 Gause Boulevard 

Slidell, LA 70458 

Performed for 

Coastal Ecology Group 

U.S. Army Corps of Engineers 

Waterways Experiment Station 

Vicksburg, MS 39180 

and 

U.S. Department of Interior 

Fish and Wildlife Service 

Research and Development 

National Wetlands Research Center 

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

U.S. Fish and Wildlife Service. 1983-19-. Species profiles: 1 ife histories and 

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

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

This profile may be cited as follows: 

Mercer, L. P. 1989. Species profiles: 1 ife histories and environmental 

requirements of coastal fishes and invertebrates (Mid-Atlantic)--weakfish. U.S. 

Fish Wildl. Serv. Biol. Rep. 82(11.109). U. S. Army Corps of Engineers, 

TR EL-82-4. 17 pp. 
PREFACE 

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

principal ly fish, of sport, commercial, or ecological importance. The profil es 

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

comprehensive sketch of the biological characteristics and envi ronmental 

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

expected to react to environmental changes caused by coastal devel opnent. Each 

profile has sections on taxonomy, life hi story, ecological role, environmental 

requirements, and econani c importance, if appl i cab1 e. A three-ring 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. 

Millikin and Wi1 liams (1984) previously publistled a review of the 

nomenclature, taxononly, morphology, distribution, life history, population 

structure and dynamics, and the fishery of the blue crab. 

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

fol 1 owing addresses. 

Information Transfer Specialist 

National Wet1 ands Research Center 

U.S. Fish and Nil dli fe Service 

NASA-S 1 i dell Computer Compl ex 

1010 Gause Boulevard 

Slidell, LA 70458 

U .S. Army Engineer Waterways Experiment Station 

Attention: WESER-C 

Post Office Box 631 

Vicksburg, MS 39180. 
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CONTENTS 

Page 

PREFACE .................................. i i i 

CONVERSIONTABLE ............................. i v 

ACKNOWLEDGMENTS .............................. v i 

NOMENCLATURE/TAXONOMY/RANGE ........................ MORPHOLOGY/IDENTIFICATIONAIDS ...................... REASON FOR INCLUSION IN THE SERIES .................... LIFE HISTORY ............................... Spawning ................................ Fecundity ............................... Larvae ................................. Juveniles ........ .. ...................... Adults ................................. GROWTH CHARACTERISTICS .......................... COMMERCIAL AND RECREATIONAL FISHERIES ................... ECOLOGICAL ROLE .............................. Food Habits .............................. Community Ecology ........................... Diseases ................................ ENVIRONMENTAL REQUIREMENTS ........................ Temperature .............................. Salinity ................................ DissolvedOxygen ............................ Pollution ................................ LITERATURE CITED ............................. 
ACKNOWLEDGMENTS 

I am grateful to Stuart Wilk and Tony Pacheco of the National Marine 

Fisheries Service, Sandy Hook, New Jersey, for their reviews of the manuscript and 

helpful suggestions. 
Figure 1. Weakfish (Cynoscion regalis) (from Goode 1884). 

WEAKFISH 

Scientific name . . . . . . Cynoscion 

regal is 

Preferred common name . . . . Weakfish 

(Figure 1) 

Other common names . . . . Gray trout, 

squeteague, sea trout, trout, tiderunner 

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

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

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

Geographical range ......... Weakfish 

occur along the Atlantic coast of 

the United States from southern 

Florida to Massachusetts Bay, 

straying occasionally to Nova Scotia and into the eastern Gulf of 

Mexico (Goode 1884; Hi 1 debrand and 

Schroeder 1928; Bigelow and Schroeder 1953; Guest and Gunter 1958; 

Leim and Scott 1966; Struhsaker 

1969; Weinstein and Yerger 1976; 

Chao 1978). They are most abundant 

from North Carolina to New York 

(Figure 2). 

MORPHOLOGY/IDENTIFICATION AIDS 

The following description is that of 

Johnson (1978), summarized from Jordan 

and Evermann (1896), Eigenmann (1901), 

Hildebrand and Schroeder (1928), 

Ginsburg (1929), Perlmutter (1939), 

Massmann ( 1963), Tagatz ( 1967), Mi 11 er 

and Jorgenson (1973), and Chao (1978). 

Dorsal rays 24-29, modally 27. Anal 

rays 10-13, modally 12. Vertebrae 25. 

Gill rakers 4-5 upper,lO-12 lower, and 

typical ly 5 + 12. A pair of large 

canine-1 i ke teeth at the tip of upper 
jaw and a row of distinctly enlarged 

teeth in the lower jaw. Body elongate, moderate1 y compressed. Head 

long, snout pointed. Mouth large, 

oblique, lower jaw projecting, maxillary reaching to posterior margin of 

pupil or beyond. Dorsal fin with a 

deep notch between the spinous and 

soft portions. Caudal emarginate in 

individuals less than 300 mm total 

length (TL). Color dark olive green 

above with the back and sides 

variously burnished with purple, 

lavender, green, blue, gold or copper, 

and marked with a large number of 

small dark spots which appear as 

oblique streaks running along scale 

rows above lateral 1 ine. Lower 

surface forward to tip of jaw white 

or silvery, sometimes iridescent. 

Dorsal fins dusky, the lower edge 

yellowish at base. Pelvic and anal 

fins yellow; pectoral fin olive on 

outer side, usually yellow on inner 

side. 

REASON FOR INCLUSION IN THE SERIES 

The weakfish is one of the most 

abundant fishes in the estuarine and 

nearshore waters of the Atlantic coast 

(Wi 1 k 1979). It is a valuable recreational species and a major component 

of the gill-net, pound-net, haulseine, and trawl fisheries along the 

coast (Hildebrand and Schroeder 1928; 

Wil k 1981). Periods of high landings 

have generally been followed by sudden 

and precipitous declines in catch, 

the causes of which are not known. 

Overf i shi ng and habitat a1 terations 

have been suggested as possible 

causes. 

LIFE HISTORY 

Spawning 

Weakfish mature at age I throughout their geographic range; however, 

Figure 2. General distribution of the length at maturity differs between 

weakfish along the Atlantic coast of northern weakfish (Delaware Bay and 

the United States (from Wilk 1976). north) and weakfish from North Caro- 
lina. In northern fish, females 

matured at 256 mm and males at 251 mn 

TL (Shepherd and Grimes 1984); in 

North Carolina females spawned at 230 

rnm and ma1 es at 180 mm TL (Merriner 

19'76). 

Weakfish spawn in the nearshore 

and estuarine areas of the coast after 

the spring inshore migration (Welsh 

and Breder 1923; Hildebrand and 

Schroeder 1928). The spawning season 

of weakfish is earl.ier and somewhat 

longer in North Carolina than in areas 

to the north; it extends from March to 

September, and peaks from April to 

June (Merriner 1976). In the New York 

Bight (Delaware Bay to New York), the 

season extends from May to mid-July 

(Shepherd and Grimes 1984). Two 

spawning peaks are reported for 

weakfish in New York Bight estuaries: 

the earlier mid-May peak, attributed 

to the largest individuals or "tiderunners," is followed by a June peak 

developed by small er f.i sh (Shepherd 

and Grimes 1984). 

Fecundity 

Lstimates of fecundity for southern 

weakfish differ from those for fish 

from the New York Bight. A weakfish 

500 mm TL from North Carolina produced 

2,051,080 ova, whereas a northern fish 

of the same length produced only 

306,159 ova (Merriner 1976; Shepherd 

and Grimes 1984). The fo1 lowing 

relationships between fecundity (F) 

and standard length (SL) in millimeters, total length (TL) in millimeters, weight (W) in grams, and gutted weight (GW) in grams, where In is 

the natural logarithm and r is the 

coeff i cient of determination, were 

presented for weakfish in North 

Carolina (Merriner 1976): 

In F = -2.154 + 2.776 In SL; 

In F = -1.884 + 2.642 In TL; 

and the New York Bight (Shepherd and 

Grimes 1984) : 

In F = -16.322 + 4.659 In TL; 

In F = 1.975 + 1.542 In GW; 

Larvae 

The embryology and larval development of weakfish were described by 

Welsh and Breder (1923), Pearson 

(1941), Harmic (1958), Scotton et al. 

(1973), Lippson and Moran (1974), 

Johnson (1978), and Powles and Stender 

(1978). Hdtching occurs in 36-40 

hours at 20-21 OC (Welsh and Breder 

1923). Weakfish larvae range from 1.5 

to 1.75 mm TL at hatching and become 

demersal by 8 mm TL (Welsh and Breder 

1923; Pearson 1941). Weakfish larvae 

have been collected in nearshore 

waters to 70 km offshore in coastal 

ichthyoplankton surveys (Berrien et 

al. 1978). 

Juveni 1 es 

The use of estuarine areas as 

nursery grounds by weakfish is well 

documented. Juveniles are collected 

most frequently in trawl sampling of 

the deeper waters of rivers, bays, and 

sounds, rather than in beach seine 

col lections from shoal areas (Greel ey 

1939; Massmann et al. 1958; Schwartz 

1961, 1964a; Richards and Castagna 

1970; Thomas 1971; Chao and Musick 

1977). 

Extensive sampling of North Carolina sounds revealed that juvenile 

weakfish were most abundant in areas 

designated by the North Carolina 

Division of Marine Fisheries as secondary nursery areas (usual 1 y shall ow 

bays or navigation channels character- 
ized by moderate depths, slightly 

higher salinities, and presence of 

sand and/or sand-grass bottoms) rather 

than in primary nursery areas (shallow 

tributaries of low salinity and mud 

and/or mud-grass bottom) (Spitsbergen 

and Wolff 1974; Purvis 1976). In 

Chesapeake Bay and Delaware Bay 

juvenile weakfish migrate from high to 

low salinity areas throughout the 

summer, return to high salinity waters 

in fall, and leave the estuaries by 

December (Hildebrand and Schroeder 

1928; Massmann et al. 1958; Thomas 

1971; Chao and Musick 1977). 

Juvenile weakfish are distributed 

along the coast from Long Island to 

North Carolina at depths of 9-26 m in 

late summer and fa11 (Clark et al. 

1969). Young-of-the-year weakfish 

were caught in ocean trawl surveys 

along the coast of North Carolina in 

1968-1981 at depths of 9-18 m during 

fall and winter, and from North 

Carolina to Florida at depths of 9-11 

m in winter and early spring (Wilk and 

Silverman 1976). 

Adults 

Adult weakfish migrate seasonal 1 y 

between inshore and offshore waters 

(Welsh and Breder 1923; Merriner 1973; 

Wi 1 k 1976, 1979, 1980). Warming of 

coastal waters in spring prompts an 

inshore and northerly migration of 

adults from their wintering grounds to 

sounds, bays, and estuaries (Figure 

3). The larger fish move inshore 

first and tend to congregate in the 

northern part of the range ( W i l k and 

Silverman 1976; Wil k et al. 1977). 

Catch records from the pound-net and 

haul-seine fisheries in Delaware Bay, 

Chesapeake Bay, and Pamlico Sound 

indicate that the large fish are followed by a second group of smal ler 

weakfish in summer (Higgins and 

Pedrson 1928; Massmann 1963; Daiber 

and Smith 1971; Sholar 1979; DeUries 

1980, 1981). Shortly after their Figure 3. Movements of the weakfish 

initial appearance, weakfish return to along the Atlantic coast of the United 

the larger bays and possibly to the States during spring and summer (from 

ocean to spawn. In northern areas a Wil k 1976). 

4 
greater proportion of the adults spend 

the summer in ocean waters rather than 

in estuaries. 

As water temperatures decline in 

fa1 1, weakfish form aggregations and 

move offshore and generally southward 

along the coast (Nesbit 1954; Massmann 

et a). 1958; .Wil k 1976; Wi 1 k and Si lverman 1976) (Figure 4). The Continental Shelf from Chesapeake Bay to 

Cape Lookout, NC, appears to be the 

major wintering ground for weakfish. A 

study of the winter trawl fishery off 

the Virginia and North Carolina coasts 

indicated that most weakfish were 

caught in the southern fishing area 

between Ocracoke Inlet and Bodie 

Island, NC, at depths of 18-55 m 

(Pearson 1932). Some weakfish may 

remain in inshore waters throughout 

the winter from North Carol ina 

southward (Goode 1884; Higgins and 

Pearson 1928; Hildebrand and Cable 

1934). 

GROWTH CHARACTERISTICS 

Weakfish growth is particularly 

rapid during the first year. In Delaware Bay, juveniles may grow from 20 

to 35 mm/month during June-September 

(Ichthyological Associates 1980) and 

may attain lengths ranging from 100 to 

175 mm TL throughout the range. The 

variability of sizes within year 

classes results from the extended 

spawning season. Massmann et a1 . (1958) and Thomas (1971) found two 

distinct size groups of young-of-theyear weakfish in fa1 1 in Chesapeake 

Bay (45 and 85 mm) and Delaware Bay 

(30-40 and 110-130 mm). This apparently reflects two separate spawning 

peaks. Thomas (1971) did not find a 

bimodal length distribution for adult 

weakfish which may be due to differential mortality of late-spawned weakfish or to compensatory growth. 

Weakfish age and growth studies Figure 4. Movements of the weakfish 

indicated geographic variations in along the Atlantic coast of the United 

growth, with a pattern of increasing States during fall and winter (from 

size toward the northern end of the Wil k 1976). 
range (Table 1). Shepherd and Grimes 

(1.983) found that northern weakfish 

collected between Cape Cod, MA, and 

Ocean City, MD, were largest at each 

age and attained a greater maximum 

size and longevity (810 mm TL at age 

XI). Size at age of weakfish collected between Virginia Beach, VA, and 

Cape Fear, NC, was lowest (370 mm TL 

at age 111) and similar to that 

reported by Taylor (1916) and Merriner 

(1973). In weakfish from Chesapeake 

Bay (Ocean City, MD, to Virginia 

Beach, VA) size at age and maximum 

size were intermediate and were 

comparable to what Seagraves (1981) 

reported for Delaware Bay in 1979. 

Shepherd and Grimes (1983) suggested 

that these growth variations may 

result from differing a1 locations of 

energy to somatic growth according 

to environmental and migratory 

requirements. Growth of weakfish of 

southern origin may also be limited by 

prey avai labi 1 i ty or by genetic 

differences. 

Records of weakfish size at various 

ages show differences over time (Table 

2). A comparison of female weakfish 

from the New York Bight showed that 

age-IV females in 1929 averaged 340 mm 

TL compared to 480 mm TL in 1952 and 

580 mm TL in 1980 (Perltnutter et al. 

1956; Shepherd and Grimes 1983). 

Known longevity was 8 yr in 1929, 6 yr 

in 1952, and 11 yr in 1980. Similar 

changes in growth and longevity were 

reported for weakfish in Delaware Bay 

(Seagraves 1981). 

Growth of weakfish was described by 

the von Bertalanffy growth curve: 

where It is length at age t, Lm is the 

asymptotic length, K is the Brody 

growth coefficient, t is age, and t 

is the hypothetical age at which th? 

fish would have been zero length. Von 

Bertal anffy growth parameters showed 

a trend of decreasing values of Lm 

from north to south, with the 

exception of Delaware Bay weakfish 

in 1979 (Seagraves 1981; Shepherd and 

Grimes 1983) (Table 3). A larger 

asymptotic .length was obtained for 

Delaware Bay weakfish in 1979 than in 

1956. 

Length-weight relationships have 

been developed for weakfish from 

throughout the Mid-Atlantic Region 

Table 1. Mean total lengths (mm) at age of weakfish from three regions (from 

Shepherd and Grimes 1983). 

Ocean City, MD Virginia Beach, VA Cape Fear, NC 

to to to 

Cape Cod, MA Ocean City, MD Virginia Beach, VA 

Age 1979-81 1979-81 1979-81 

qroup Ma1 e Female Ma1 e Femal e Male Fema 1 e 
Table 2. Mean total lengths (mm) at age of weakfish. 

Chesapeake 

a Perlmutter et al. (1956). c Taylor (1916). 

b Seagraves (1981). d Merriner (1973) * TL approximated by: TL = 1.21 SL. 

Table 3. Von Bertalanffy growth parameters for weakfish (sexes combined) where 

L is the asymptotic length in millimeters (SL) (Standard length approximated by: 

sE=TL/~.z~), to is the hypothetical age at which the fish would have been zero 

length, K is the Brody growth coefficient, and W is weight in grams. 

Area 

Cape Cod, MA - 

Ocean City, MD~ 

Ocean City, MD - Virginia Beach, VA~ 567 0.051 0.350 3026.0 

Virginia Beach, XA - Cape Fear, N.C. 331 -1.270 0.550 608.3 

Delawgre Bay 

1956 315 - 

Delawgre Bay 

1979 735 0.084 0.236 - 

a Shepherd and Grimes (1983). 

b Seagraves (1981). 
(Table 4). Merriner (1973) found Merriner 1973; Wilk 1981). During 

significant length-weight differences the period 1940-49, pound nets, haul 

between males and females which he seines, gill nets, and trawls took 

attributed to proportionately greater approximately 63%, 11%, 3%, and 23% of 

development of ovarian tissue relative the total catch, respective1 y. Durto testicular tissue. ing 1970-79, the contribution of these 

same four gear types was 20X, 11%, 9%, 

and 60%, respectively (Wilk 1981). 

COMMERCIAL AN11 RECREATIONAL FISHERIES 

The principal commerci a1 methods 

used to harvest weakfish include 

trawls, pound nets, haul seines, and 

gill nets. In addition, weakfish are 

caught in purse seines, floating 

traps, trammel nets, fyke nets, hoop 

nets, and hand lines. Generally these 

fisheries can be classified as mixed 

opportunistic fisheries that concentrate direct1 y on weakfish for brief 

periods (Wilk and Brown 1982). During 

the mid-19701s, high-speed pelagic 

trawls in the form of paired trawls 

and mid-water trawls were introduced 

in the New Jersey-Delaware area. 

Although the methods used to harvest 

weakfish for food have essentially 

remained the same, there have been 

significant shifts in the contributions of trawls and pound nets during 

the past 40 yr (Perlmutter 1959; 

Commerci a1 1 andi ngs of weakfish 

have fluctuated widely since the late 

1800's. Two peaks in landings have 

occurred since 1940, an all-time high 

of 18,800 t in 1945 and 16,300 t in 

1980. The distribution of weakfish 

landings has shifted historical ly from 

one geographic area to another (Wilk 

1980) (Figure 5). The Chesapeake Bay 

region (Maryland and Virginia) contributed most to the total weakfish landings in the 19401s, followed by the 

Mid-Atlantic Region (New York, New 

Jersey, and Delaware), and the South 

Atlantic Region (primarily North Carolina). Weakfish landings remained low 

in all regions throughout the 1950's 

and 1960's. Since 1971, South 

Atlantic Region landings have exceeded 

those in one or both of the northerly 

regions. The shift in catch to the 

South Atlantic Region is probably more 

Table 4. Length-weight relationships for weakfish using the equation: log W (g) 

= log a + b log L (mm), where W is weight in grams, L is length in millimeters 

(*TL, +SL), and a and b are constant. 

Length 

Location Sex Log a b r n range (mm) 

New York Bighta* Combined -4.877 2.948 0.99 666 59-768 

Cape Cod, MA b, 

Ocean City, MD Combined -5.030 2.976 0.99 418 

Delaware BayC+ Combined -4.423 2.861 0.99 182 195-725 

North Carolina d+ Male -4.558 2.851 0.99 482 

Femal e -4.343 2.946 0.99 610 

Combined -4.374 2.934 0.99 1,650 

a From Wilk (1979)l. b From Shepherd and Grimes (1983). 

c From Seagraves (1981). d From Merriner (1973). 
8 

4- MIDDLE ATLANTIC 

10- CHESAPEAKE 

z 8- SOUTH ATLANTIC 

(North Carolina) 

6- 

4- 

YEARS 

Figure 5. U.S. commercial landings of 

weakfish by geographic region. 

a reflection of the increased mobil i ty 

of the North Carolina f.ishitig fleet, 

and a concomitant shift in the center 

of landings to North Carolina, rather 

than an actual shift in distribution 

of weakfish (Wilk 1981). 

Weakfish have also been important 

to the recreational fishery since at 

least the 1800's (Goode 1884). Anglers 

take weakfish from boats while trolling and drift fishing, and from boats 

and shore while casting, live bait 

fishing, jigging, still fishing, and 

chumming, primari ly during the warmer 

months of the year (Freeman and Walford 1974a, b, c, 1976a, b). Data 

from the National Marine Fisheries 

Service Marine Recreational Fishery 

Statistics Survey also indicate a peak 

in twcreational 1 andings in 1980 

(20,544 t) followed by a sharp decline 

by 1982 (Table 5). 

Table 5. Estimated number and weight 

of weakfish caught by recreational 

fishermen in the Mid-Atlantic Region 

(New York-Virginia) 1979-87. (National 

Marine Fisheries Service Marine Recreational Fishery Statistics Survey, 

Atlantic and Gulf Coasts 1979-87). 

Year Number Weight 

(thousands) (t) 

* Preliminary data 

ECOLOGICAL ROLE 

Food Habits 

Weakfish feed predominantly on 

penaeid and mysid shrimps, anchovies, 

and clupeid fishes (Welsh and Breder 

1923; Thomas 1971; Merriner 1975; 

Stickney et al. 1975; Michaels 1984). 

A shift of food habits with growth was 

reported by Thomas (1971), Merriner 

(1975), and Stickney et al. (1975). 

Young weakfish feed mostly on mysid 

shrimp and anchovies; older weakfish 

feed on whatever clupeid species are 

abundant in an area. Michaels (1984) 

reported that anchovies (rather than 

clupeids) were the single most important prey fish of weakfish 

collected offshore (depths > 6 m). 

Cannibalism was reported to be significant in weakfish (Thomas 1971; 

Merriner 1975). Weakfish feed primarily between dusk and dawn (Lascara 

1981; Michaels 1984). Chao and Musick 

(1977) correlated feeding structures 

with the food habits of juvenile 

sciaenids. The weakfish has an 

oblique mouth that enables it to cap- 
ture pelagic prey from above and in 

front of it. Other adaptations for 

successful predation include a pair of 

large canine teeth at the tip of the 

upper jaw for grasping larger swimming 

prey and a fusiform body shape for 

fast pursuit. 

A study of fish predator-prey 

interactions in areas of eel grass 

(Zostera marina) in Chesapeake Bay 

indicated that weakfish are important 

top carnivores in this habitat 

(Lascara 1981). Field data and laboratory observations have suggested 

that weakfish forage along the periphery of eel grass beds during periods 

of low light (dusk to dawn). The 

high percentage of blue crabs (Call inectes sapidus) (40) and spot (Leiostomus xanthurus) (18) in weakfish 

stomachs indicated that some feeding 

occurred in eelgrass beds, since these 

animals were considerably more abundant there than at adjacent non-vegetated sampling sites. The lack of 

eelgrass in stomachs and the oblique 

mouth position of the species suggested, however, that weakfish feed pelagically and not deep within the vegetation. In laboratory experiments, 

weakfish captured fewer prey as the 

percentage of vegetative cover increased (Lascara 1981). 

Community Ecology 

Surveys along the Atlantic coast 

indicated that estuaries provide feeding areas and spawning grounds for 

adult weakfish and are important 

nursery areas for the young. Studies 

in Delaware Bay (Thomas 1971) and 

Chesapeake Bay (Chao and Musi ck 

1977) showed that several species of 

sciaen.ids, including weakfish, si lver 

perch (Biirdiel la -chrysoura)-, spot, 

croaker (Micropogonias undulatus), and 

black drum (Pogoni as cromis) were 

able to coexist in the estuaries: 

probable reasons include differences 

in spatial and temporal distribution, 

re1 ative abundance (abundances of 

dominant competitors may be reduced by 

physical disturbance or predation), 

and food habits. Juveniles of these 

species enter the estuaries at 

different times of the year, and within a given period, the highest catches 

of each species are in different 

areas and depths. Although weakfish 

and croaker both prefer the deeper 

water in or near channels, croaker 

do not enter estuarine areas until 

fall after most weakfish have left. 

Differences in the morphology of the 

feeding apparatus enable each species 

to feed at different levels of the 

water column. 

Diseases 

Mahoney et al. (1973) reported that 

weakfish, especial 1 y juveniles, are 

one of the most susceptible species to 

the "fin rot" disease of marine and 

euryhal ine fishes in the New York 

Bight. The consistent and most 

striking feature of the disease in 

weakfish is necrosis of the caudal fin 

followed by involvement on the other 

fins. Pollution is suspected to have 

a role in the disease. This disease 

has also been observed in weakfish 

from Delaware Bay and Georgia. 

ENVIRONMENTAL REQUIREMENTS 

Temperature 

Weakfish eggs in a1 1 stages of 

development were col lected in Peconic 

Bay, NY, and Narragansett Bay, RI, at 

temperatures of 12-24 "C (Perlmutter 

1939; Herman 1963). Laboratory tests 

indicated that hatching of weakfish 

eggs was optimal between 18 and 24 "C 

(tiarmic 1958). 

Weakfish have been collected over a 

temperature range of 9.5 to 30.8 "C 

(Massmann et al. 1958; Richards and 

Castagna 1970; Merriner 1976). In 

areas of highest abundance of juvenile 

weakfish in Delaware Bay, water 

temperatures ranged from 28.0 "C in 

July to 17.2 "C in October ('Thomas 
1971). Decreasing water temperatures 

in fall appear to initiate movement 

of most weakfish out of the estuaries 

to deeper water. Older weakfish 

appear to precede the young of the 

year in moving out of the estuaries 

(Hildebrand and Cable 1934; Massmann 

et al. 1958; Thomas 1971). 

Only a few weakfish have been 

collected at temperatures below 10 OC 

in Delaware Bay or Chesapeake Bay 

(Massmann et al. 1958; Abbe 1967; 

Thomas 1971). Hildebrand and Cable 

(1934) reported that some small 

weakfish (122-182 mm TL) remained in 

North Carolina estuaries and nearshore 

coastal waters year-round except during brief cold snaps. Dead and numb 

weakfish were seen in shallow waters 

when water temperatures sudden1 y 

dropped to 5 OC (Smith 1907; Hildebrand and Cab1 e 1934 ) . 

Schwartz (1964b) subjected five 

weakfish collected at 20.7 OC to 

normal winter water temperatures. 

Swimming speed slowed drastically as 

the water temperature approached 10 

oC, feeding ceased at 7.9 oC, and all 

fish died at 3.3 OC. Wilk (1979) 

reported that as temperature was gradually increased (0.05 oC/~) from the 

accl imated temperature range of 19-20 

OC to almost 29 oC, weakfish showed a 

35% increase in swimming speed accompanied by tighter and more frequent 

school i ng; however, as the fish became 

acclimated to 29 OC their activity 

decreased to a point similar to that 

before the temperature was increased. 

This increased activity may help to 

move the animals from regions of adverse high temperature. 

Salinity 

Weakfish are euryhaline and have 

been collected at sal ini ties ranging 

of 0.1 to 32.3 ppt (Massmann et al. 

1958; Richards and Castagna 1970; Wilk 

and Silverman 1976; Wilk et al. 1977). 

Harmic (1958) collected eggs and 

larvae in Delaware Bay at salinities 

of 12.1 to 31.3 ppt. Juveniles have 

been taken in salinities from 0.1 to 

31.7 ppt, but areas of most abundant catches had salinities of 2.0 ppt 

in June to 10.8 ppt in August (Massmann et al. 1958; Richards and Castagna 1970; Thomas 1971). Adults were 

collected over a salinity range of 6.6 

to 32.3 ppt (Richards and Castagna 

1970; Wilk and Silverman 1976; Wilk et 

al. 1977). 

Dissolved Oxygen 

Information on relationships between dissolved oxygen and weakf i sh 

to1 erance or preferences is scarce. 

Thomas (1971) reported that upriver 

movement of juvenile weakfish in the 

Delaware River was blocked by low 

oxygen concentrations (1.0-2.3 ppm). 

In areas of the most abundant catches 

of juvenile weakfish in Delaware Bay, 

mean dissolved oxygen ranged from 4.2 

ppm in July to 7.4 ppm in October. 

Pollution 

In a model of the effects of 

pollution on a multispecies group of 

coastal fishes, weakfish showed 

re1 a'tively 1 arge depressions in 

abundance in response to chronic or 

acute pol 1 ution, but then recovered 

relatively quickly (in 6-10 years) 

(Schaaf et al. 1987). 

LITERATURE CITED 

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Berrien, P. L., M. P. Fahay, A. W. 

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152 pp. 

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74: 18-26. 

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312. 

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PP - 
Richards, C. E., and M. Castagna. 

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4. litla and Subtltle L Ramst Date 

Species Profiles: Life Histories and Environmental Requirements of 

Coastal Fishes and Invertebrates (Mid-Atlantic)--Weakfish 

10272 -101 

7. Au(hor(s) I L Petformin# Orlanlzatlon Re@. No. 

REPORT DOCUMENTATION 1. RE'Om 2. 

PAGE IB~ 01Ogi cdl Report 82( 11.109)d 

North Carolina Division of Marine Fisheries 

P.O. Box 769 

S. Raclpl*nt's Accasslon No. 

I Morehead City, NC 28557 I -- 

12. Spon.orln8 O~anlzatlon Name 

-- 

and Addmsn (I2) 

U.S. Department of the Interior U. S. Army Corps of Engineers 

Washington, DC 20240 Waterways Experiment Station 

Fish and Wildlife Service P.O. Box 631 

National Wetlands Research Center Vicksburp, MS 39180 

I 

13. Supplementafy Note* I 

U.S. Army Corps of Engineers Report No. TR EL-82-4 16. Ahtract (Limit: 200 word.) I 

Species profiles are literature summaries of the taxonomy, morpholog.~, range, life 

history, and environmental requirements of coastal aquatic species. They are designed 

to assist in environmental impact assessment. Weakfish are one of the most abundant 

fishes in the estuarine and nearshore waters of the Atlantic coast. Weakfish mature 

at age I throuqhout their range and spawning takes place in coastal and estuarine waters 

from March to September. Juveniles utilize the deeper areas within estuaries as 

nursery grounds, migrate from high to low salinity areas throuqhout the summer, return 

to high salinity areas in fall, and most leave the estuaries by late fall. Some may 

remain in estuarine and nearshore coastal waters in winter, particularly in southern 

areas. Adult weakfish migrate seasonally, north in spring and south in fall and between 

inshore and offshore waters. Growth rates, maximum size, and longevity of weakfish are 

higher at the northern end of the range. Weakfish are an important recreational and 

commercial species in the Mid-Atlantic. Weakfish feed predominantly on mysid shrimp 

and anchovies as juveniles, and on clupeids and anchovies as adults. Weakfish have 

been found over a temperature range of 9.5 to 30.8 "C. Juvenile weakfish have been 

found over a wider salinity range (0.1-31.7 ppt) than adults (6.6-32.3 ppt). 

Estuaries Temperature Fishes 

Growth Salinity Habitat requirements 

Life cycles Dissolved oxygen 

Food habits Fisheries 

b. IdentlRen/OD.n.Ended Terms 

Weakfish 

Cynoscion reqalis 

Spawning 

I 1 Unclassified 

(5.- ANSI-239.IO OPTIONAL FORM 272 (4-71 

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Unl imi ted 

19. Scurity Class (This R*mrO 

Unclassified 

20. kcurity Class (This Paw) 
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the Interior has responsibility for most of our nationally owned 

public lands and natural resources. This includes fostering the 

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and wildlife, preserving the environmental and cultural values of our 

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our energy and mineral resources and works to assure that their 

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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 

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