FISHERY BULLETIN: VOL. 81. NO. 1 



of this predator. The purpose of the present 

 paper is to describe the stomach contents of yel- 

 lowtail flounder and quantitatively evaluate fac- 

 tors influencing the quantity and composition of 

 the animal's stomach contents. 



METHODS 



Yellowtail flounder stomachs were collected 

 on eight bottom trawl survey cruises conducted 

 from 1973 through 1976. The dates of the cruises 

 are as follows: 16 March-15 May 1973; 26 Sep- 

 tember-20 November 1973; 12 March-4 May 

 1974; 20 September-14 November 1974; 4 March- 

 12 May 1975; 15 October-18 November 1975; 4 

 March-8 May 1976; 20 October-23 November 

 1976. Fish collections were made from the RV 

 Albatross IV or RV Delaware II, using a #36 

 Yankee otter trawl for autumn surveys and a #41 

 Yankee otter trawl for spring surveys. A scheme 

 of stratified random sampling was carried out in 

 the continental shelf waters between Nova Scotia 

 and Cape Hatteras, N.C. For survey purposes 

 this region has been divided into five geographic 

 areas, which are further subdivided into depth 

 strata as depicted in Clark and Brown (1977) and 

 described by Grosslein (1969 4 ). 



Yellowtail flounder were selected from the 

 catch in, primarily, two of the five geographic 

 areas, i.e., southern New England and Georges 

 Bank which include the three major fishing 

 grounds and major yellowtail flounder stocks in 

 U.S. waters (Lux 1963). Stomachs were labelled 

 according to vessel, cruise, station, length, sex, 

 and sexual maturity and were preserved individ- 

 ually in a gauze wrapping in 10% Formalin 5 . The 

 sampling strategy was designed to collect fish, 

 more or less at random, from the population with- 

 out bias towards a specific length, except as de- 

 scribed below. We attempted to collect 50 fish 

 per geographic area per cruise for fish both 

 above and below 12 cm TL (total length). Twelve 

 centimeters in length approximates the length of 

 1- to 2-yr-old fish, and these smaller fish were 

 preserved intact after the body cavity was cut 

 open to insure fixation of the contents. 



In the laboratory, individual stomachs were 

 opened, and the contents emptied onto a fine 

 mesh screen and rinsed with seawater. The vari- 



4 Grosslein, M. E. 1969. Groundfish survey methods. 

 Northeast Fisheries Center Woods Hole Laboratory Reference 

 No. 69-2, 34 p. 



5 Reference to trade names does not imply endorsement by 

 the National Marine Fisheries Service, NOAA. 



ous items were sorted and identified to the lowest 

 possible taxa. Each distinct group was blotted 

 dry and immediately weighed. In the text and 

 tables these weights have been expressed as a 

 percentage of the total weight of stomach con- 

 tents. In the text these percentages are often 

 given in brackets after the mention of taxa to 

 quantify their relative importance. 



Twelve percent of the fish collected fell into the 

 three smallest size classes (Table 1) with a mean 

 length of 7.6 cm. Fish >15 cm TL were equally 

 distributed around the 31-35 cm size class with 

 70% (h =715) of all fish examined falling between 

 26 and 40 cm TL. The average length of all fish 

 comprising this peak is 32.8 cm. For some analy- 

 ses two size-related groupings of fish, represen- 

 tative of this bimodal distribution, have been 

 differentiated while in other cases the data are 

 presented by 5 cm length classes or expressed as 

 a percentage of the fishes' body weight according 

 to the length/weight equation in Wilk et al. 

 (1978). [W=aL h where a = 0.4514" 5 , 6 = 3.1257, 

 and L is in millimeters.] 



RESULTS 

 Food 



Of the 1,021 stomachs examined, 684 contained 

 prey which weighed in total 422 g. The overall 

 mean fish length and standard deviation was 

 29.4+10.5 cm. The prey were allocated into 148 

 different categories, which included all taxonom- 

 ic levels of identification and such miscellaneous 

 categories as sand and unidentifiable animal re- 

 mains. The most important major taxonomic 

 groupings were polychaetes and crustaceans 

 (Table 1). 



Polychaetes accounted for 43% of the stomach 

 contents. The families Spionidae (13.27%), Lum- 

 brinereidae (1.90%), Sabellidae (1.42%), and 

 Nephtyidae (1.19%) were all of some importance. 

 Spiophanes bombyx was the major prey, making 

 up 9.68% of the weight of the total stomach con- 

 tents. Other polychaetes (17.24%) and polychaete 

 tubes (7.94%) accounted for the remainder of the 

 prey in this taxon. 



Crustaceans (18.0%) were second in impor- 

 tance, the amphipods (13.65%) being the major 

 prey group. Unciola sp. (4.41%), Leptocheirus 

 pinguis (2.25%), and Byblis serrata (1.72%) were 

 important amphipod prey. Other gammarids 

 (1.92%), ampeliscids (1.56%), and corophiids 

 (0.3%) made up most of the remaining amphipod 



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