290 Abstract—From 2008 through 2010, Diet composition, feeding strategy, and the diets of 3 sciaenid species, the weakfish (Cynoscion regalis), south- diet overlap of 3 sciaenids along the ern kingfish (Menticirrhus america- nus), and Atlantic croaker (Micropo- southeastern United States gonias undulatus), were examined. Stomach contents were identified, C. Michelle Willis (contact author) enumerated, and weighed to deter- Jonathan Richardson mine the diet composition and feed- ing strategy of each species and diet Tracey Smart overlap among species. Bony fishes Joseph Cowan were the most frequently consumed Patrick Biondo prey of weakfish. Decapods, nonde- capod crustaceans, and polychaetes were the most commonly consumed Email address for contact author: [email protected] prey of southern kingfish and Atlan- tic croaker. Some individuals of all Southeast Area Monitoring and Assessment Program –South Atlantic species consumed specific prey types Marine Resources Research Institute and others consumed varying prey South Carolina Department of Natural Resources types; however, specialization was 217 Fort Johnson Road a more common trait for weakfish Charleston, South Carolina 29412 than for the other 2 species. Weak- fish diets had minimal overlap with diets of the other 2 species; however, the Morisita-Horn index indicated considerable overlap between south- ern kingfish and Atlantic croaker. Ecosystem-based fisheries manage- the South Atlantic component of the Potential for competition could oc- ment is dependent on defining not Southeast Area Monitoring and As- cur between these 2 species, but, because both are often opportunistic only target species but the species sessment Program (SEAMAP-SA), as feeders, it is unlikely that competi- and habitats with which they inter- part of its Coastal Survey (a long- tion would occur unless shared re- act. Ecosystem-based management term, fishery-independent, shallow- sources become scarce. Descriptions models ideally would account for the water trawl survey from Cape Ca- of feeding strategies, prey resources, complexities of ecosystems, allowing naveral, Florida, to Cape Hatteras, and the potential for competition managers to incorporate ecosystem North Carolina), began collecting among co-occurring species can pro- relationships in management strat- stomachs from 3 common species vide a framework for management of egies and decisions (Brodziak and of Sciaenidae: weakfish (Cynoscion these species, particularly for ecosys- Link, 2002). The Magnuson-Stevens regalis), southern kingfish (Men- tem-based management. Fishery and Conservation Reau- ticirrhus americanus), and Atlantic thorization Act of 2006 (Magnuson- croaker (Micropogonias undulatus). Stevens…Act, 2007) highlighted the Weakfish, southern kingfish, and need for research detailing interde- Atlantic croaker commonly occur pendence among fisheries; trophic along the eastern coast of the United relationships can play a key role in States, residing in shallow waters understanding ecosystem composi- over bottoms of sand or sandy mud. tion, status, and energy linkages Distributions of these species greatly within the system (Link, 2002; Mag- overlap, sharing a geographic range nuson-Stevens…Act, 2007; Ainsworth from Cape Cod, Massachusetts, to Manuscript submitted 3 September 2014. et al., 2008). As a result, the South Florida and into the Gulf of Mexico Manuscript accepted 1 May 2015. Atlantic Fishery Management Coun- (only occasionally in the Gulf of Mex- Fish. Bull. 113:290–301. cil (SAFMC) has prioritized efforts ico in the case of weakfish) (Goode, Online publication date: 15 May 2015. to characterize fish diets, define rela- doi: 10.7755/FB.113.3.5 tionships between predator and prey, agement Council). 2009. Fishery Eco- and to better understand how these system Plan of the South Atlantic Re- The views and opinions expressed or gion. Volume V: South Atlantic research implied in this article are those of the relationships affect economically im- portant species (SAFMC1). Therefore, programs and data needs, 177 p. South author (or authors) and do not necessarily Atlantic Fishery Management Council, reflect the position of the National North Charleston, SC. [Available at Marine Fisheries Service, NOAA. 1 SAFMC (South Atlantic Fishery Man- website.] Willis et al.: Feeding behavior of 3 sciaenids along the southeastern United States 291 1884; Chao, 2002). In the southeastern United States, of prey items seemed to be dependent on season, prey these species have a similar life history; they grow rap- item composition was not found to be significantly dif- idly and are capable of spawning as early as 1 year of ferent among species within a season in that study. A age (Walton, 1996). diet study of species of Menticirrhus, conducted near Weakfish generally spawn from March through July the Patos Lagoon in Brazil, has shown both low species in estuarine and nearshore waters, and juveniles use diversity and seasonal differences in prey consumption, the estuary as nursery grounds. From 2008 through with polychaetes, amphipods, and various crustaceans 2010, weakfish with an average age <1 year old and being consumed most frequently (Rodrigues and Vieira, a mean of 21 cm in total length (TL) were captured in 2010). Overstreet and Heard (1978) studied Atlantic SEAMAP-SA trawl surveys, but this species reportedly croaker diets in the Gulf of Mexico and found a high lives to 8 years and can reach a length of 90 cm TL diversity of prey items, including polychaetes, mysids, (Shepherd and Grimes, 1983; Chao, 2002). Adult weak- blue crabs, amphipods, and penaeids, among other prey fish migrate seasonally between nearshore and offshore items. waters, and forage throughout the water column. Each of these fish species is important both commer- Southern kingfish are bottom foragers that spawn cially and recreationally, and each commonly occurs as on the continental shelf from April through August, bycatch in the shrimp trawl fishery (Smith and Wenner, live up to 6 years, and can grow to lengths of 60 cm 1985; Murray et al., 1992; Diamond et al., 2000). In ad- TL (Bearden, 1963; Smith and Wenner, 1985; Chao, dition, Atlantic croaker is harvested for use in the bait 2002). For southern kingfish captured by SEAMAP-SA industry (Ross, 1988). Management of these species has from 2008 to 2010, the average age was 1 year and become necessary as these industries evolve and catch the average size was 18 cm TL. Atlantic croaker are levels increase. shelf-spawners during October–January and can reach We investigated the diets of weakfish, southern king- an age of 15 years and length of 46 cm TL (Hales fish, and Atlantic croaker off the southeastern United and Reitz, 1992; Barbieri et al., 1994; Richardson States to provide current regional information on their and Boylan2). From 2008 to 2010, the mean age and diets. We also assessed the overlap in prey among the length for specimens of Atlantic croaker collected by 3 species and examined several factors that may influ- SEAMAP-SA were 1 year and 22 cm TL, respectively. ence this assessment, including spatial and temporal Atlantic croaker are demersal and use their inferior- variation in sampling. located mouth to suck prey from the substrate (Over- street and Heard, 1978). Juveniles of both southern kingfish and Atlantic croaker use estuaries as nurser- Materials and methods ies, a characteristic similar to weakfish (Musick and Wiley, 1972; Harding and Chittenden, 1987). Field sampling Although the life history of these 3 species has been studied extensively, quantitative diet information from Fishes were collected from 2008 to 2010 during the southeastern United States is either lacking or was shallow-water trawl hauls conducted as part of the collected 2 or more decades ago. The potential for diet SEAMAP-SA Coastal Survey by staff of the South Car- overlap among sciaenids with similar feeding strate- olina Department of Natural Resources. Paired 22.9- gies has not been addressed in this region to date. Mer- m mongoose-type Falcon3 trawl nets (Beaufort Marine riner (1975) examined the diet of weakfish captured in Supply, Beaufort, SC), which had a net body of no. 15 North Carolina waters and found that penaeid and twine with 4.8-cm stretch mesh and a cod end of no. mysid shrimps, anchovies, and clupeid fishes were the 30 twine with 4.1-cm stretch mesh, were deployed from most common food items. He noted a gradual onto- the RV Lady Lisa, a 23-m wooden-hulled, double-rigged genetic shift from shrimp to clupeids, specifically the St. Augustine Trawlers (St. Augustine Trawlers Inc., Atlantic thread herring (Opisthonema oglinum), begin- St. Augustine, FL) shrimp trawler. Trawl hauls were ning when weakfish were about 19 cm standard length conducted during daylight hours at target speeds of 1.3 (SL) and 1 year of age. McMichael and Ross (1987) m/s (2.5 kn) for 20 min and at depths between 4 and analyzed the diets of southern kingfish, northern king- 10 m (Hendrix and Boylan4). For the Coastal Survey, fish (Menticirrhus saxatilis), and gulf kingfish (M. lit- trawl hauls are conducted at randomly selected loca- toralis) in the Gulf of Mexico and found that southern tions within 6 regions from Cape Canaveral, Florida, kingfish most frequently consume bivalve siphons and to Cape Hatteras, North Carolina (Fig. 1). Regions are cumaceans, followed by mysids, polychaetes, brachy- urans, and gammarid amphipods. Although frequency 3 Mention of trade names or commercial companies is for iden- tification purposes only and does not imply endorsement by the National Marine Fisheries Service, NOAA. 2 Richardson, J., and J. Boylan. 2013. Results of trawling 4 Hendrix, C., and J. Boylan. 2011. Results of trawling efforts in the coastal habitat of the South Atlantic Bight, efforts in the coastal habitat of the South Atlantic Bight, 2012. Report SEAMAP-SA-CS-2012-004, 101 p. [Available 2010. Report SEAMAP-SA-CS-2010-004, 108 p. [Available from Mar. Resour. Res. Inst., Mar. Resour. Div., South Caro- from Mar. Resour. Res. Inst., Mar. Resour. Div., South Caro- lina Dep. Natl.