Food of Eight Northwest Atlantic Pleuronectiform Fishes 



RICHARD W. LANGTON' and RAY E. BOWMAN' 



ABSTRACT 



The food of eight species of pleuronecUd fishes, occurring in Ihe northwest Atlantic, from Cape Hatteras, 

 N.C., lo Nova Scotia have been investigated for the years 1969-72. 



Gulf Stream flunder, Citharkhthys arclifrons, are annelid and arthropod predators. Summer and fourspot 

 flounders, Paralichthys denlalus and P. obhngus, prey on fish, squid, and arthropods. The diet of the window- 

 pane, ■SVf'/7/)r/itj/mm ayuosui, consists of arthropods with mysids, pandalid shrimp, and sand shrimp being espe- 

 cially important pre>. Witch flounder, Giypfocephalus cynoglosius. are predators of benlhic invertebrates, prey- 

 ing heavily on annelids. The primary prey of American plaice, Hippoglossoides plalessoides, is echinoderms. 

 Yellow tail flounder, Limanda ferruginea, are annelid and amphipod predators. Winter flounder, 

 Pseudopieuronectes americanus, prey on annelids, coelenlerates, and bivalve molluscs. 



EMTRODUCnON 



Since a fish's food and feeding habits influence the productivity 

 of the standing stock, and therefore the fishing yield, there have 

 been a numba of studies of the diets of the commercially important 

 flatfishes. Feeding behavior, and consequently the food of many of 

 these fish, also relates to the morphology of the alimentary system 

 and this has led to a number of other studies (reviewed by De Groot 

 1967, 1969, 1971). Furthermore, the realization that successful 

 management of the various fish stocks must include an understand- 

 ing of the interactions between the fish populations and their prey 

 (May et al. 1979; Ursin In press) has stimulated much recent study 

 of what and how much fish eat, particularly off the U.S. coast in 

 the northwest Adantic (Edwards and Bowman 1979; Grosslein et 

 al. 1980; Langton and Bowman 1980). 



This paper is the second of two publications (Langton and 

 Bowman 1980) to deal specifically with the food of northwest 

 Atlantic fish populations, and it concentrates on eight species of the 

 Pleuronectiformes. 



METHODS 



A total of 8,008 stomachs were collected from eight species of 

 flatfish on six bottom trawl survey cruises conducted on the follow- 

 ing dates: 8 October- 22 November 1969; 3 September- 20 November 

 1970; 9 March-1 May 1971; 30 September-19 November 1971; 8 

 March-24 April 1972; and 27 September-20 November 1972. Fish 

 collections were made with a #36 Yankee otter trawl with rollers, 9 

 m legs, and standard 544 kg oval doors. The cod end and upper bel- 

 ly of the net were lined with 13 mm mesh netting to retain smaller 

 fish. A scheme of stratified random sampling was carried out within 

 the five geographic areas of the northwest Atlantic (Fig. 1), and 

 sampling continued over 24 h/d. 



Flatfish were selected haphazardly from the bottom trawl catch 



'Northeast Fisheries Center Woods Hole Laboratory, National Marine Fisheries Ser- 

 vice, NOAA, Woods Hole, Mass.; present address; Department of Manne Resources, 

 WcM Boothbay Harbor, ME CM575. 



'Northeast Fisheries Center Woods Hole Laboratory, Nadonal Marine Fisheries Ser- 

 vice. NOAA, Woods Hole, MA 02543. 



'More detailed cruise mlbmialion can be obtained from the Resource Surveys Inves- 

 tigation, Northeast Fishenes Center Woods Hole Laboratory, National Marine Fisheries 

 Service, NOAA, Woods Hole, MA 02M3. 



and the stomachs excised aboard ship. The stomachs were labeled 

 according to species, cruise, and station, and preserved in 10"% 

 Formalin. It is assumed that, using this procedure, we obtained a 

 representative sample of the entire fish population without bias 

 towards a specified length or sex for each species. In this report, 

 however, only data on fish above a specified length have been in- 

 cluded. The species considered and their minimum total lengths are 

 as follows: Gulf Stream flounder, Citharkhthys arctifrons (Goode), 

 >3 cm; summer flounder, Paralichthys dentatus (Linnaeus), >18 

 cm; fourspol flounder, Paralichthys oblongiis (Mitchill), >7 

 cm; windowpane, Scophihalmus aquosus (Mitchill), > 10 cm; 

 witch fiounder, Glyptocephalus cynoglossus (Linnaeus), > 7 

 cm; American plaice, Hippoglossoides platessoides (Fabricius), 

 >7 cm; yellowtail flounder, Limanda ferruginea (Storer), >12 

 cm; and winter flounder, Pseudopleuronecies americanus 

 (Walbaum), > 15 cm. 



In the laboratory the various prey items, and parasites, were 

 manually sorted and identified to the lowest possible taxa. Each 

 taxonomically distinct category of prey was damp dried and im- 

 mediately weighed with the precision of 0.001 g. 



The prey was summarized on a weight basis as a percentage of 

 the total weight of the stomach contents for each flatfish species. 

 This creates a bias in the data toward the larger individuals but 

 nevertheless is representative of the population as a whole. In the 

 text the broader taxonomic groupings are discussed in detail, and 

 the percentage weight is included in parentheses after the first men- 

 tion of a prey group to quantify that particular prey's significance in 

 the diet. 



RESULTS 



Food 



Gulf Stream Flounder, Citharichthys arctifrons. — A relatively 

 small total quantity of prey was found in the Gulf Stream flounder 

 stomachs that were examined, but the complete prey list includes 

 200 different categories. The majority of prey, however, was either 

 annelids (51.2%) or arthropods (42.2<5'o) (Table 1). Twenty-one 

 families of polychaete worms were identified, but the Nephthyidae 

 (24.9%) accounted for almost one-half of the annelid prey. Eleven 

 percent of the polychaetes were identified as Nephtys incisa, 0.5% 

 as N. picta, and 12.9% at the generic level, Nephtys. Other 

 polychaetes of some significance as prey are Aphrodita hastata 



