TROPHIC RELATIONSHIPS AMONG DEMERSAL FISHES IN 

 A COASTAL AREA OF THE GULF OF MAINE' 



John S. Hacunda^ 



ABSTRACT 



Food resource utilization was investigated among eight demersal fish species (longhorn sculpin, 

 Myoxocephalus octodecemspino.ms; winter flounder, Pseudopleuronectes americanus; windowpane, 

 Scopthalmus aquosus; yellowtail flounder, Limanda ferruginea; little skate, Raja erinacea; Atlantic 

 cod, Gadus morhua\redhake, Urophycischuss: ocean pout, Macrozoarces americanus) over a 13-month 

 period in an area of Johns Bay, Maine. Despite the dominance of polychaetes and mollusks in the 

 benthos, crustaceans composed the major prey group in all predators. There was considerable trophic 

 similarity among the fishes and the amphipods Unciola sp. and Leptocheirus pinguis were the most 

 important prey in seven of the eight predators. The results indicate that resource partitioning by prey 

 size is related to different mouth morphologies for closely related species (winter flounder, yellowtail 

 flounder, windowpane), and that unrelated species with similar mouth morphologies may overlap in 

 prey size use (longhorn sculpin, Atlantic codl. 



Recent studies have revealed the complexity of 

 feeding relations among marine organisms ( Isaacs 

 1972; Lange and Hurley 1975). The concept of un- 

 structured food webs necessitates a detailed 

 knowledge of the food habits of component species 

 in order to establish their trophic connections and 

 to determine energy flow pathways through the 

 ecosystem. Fish food habit studies are helpful in 

 deciphering some of the higher level trophic rela- 

 tions in an ecosystem. From a practical 

 standpoint, information on the quantity and qual- 

 ity of food consumed by fish is needed for estimat- 

 ing fish production (Paloheimo and Dickie 1970; 

 Mills and Fournier 1979). In addition, knowledge 

 of the feeding ecology of noncommercial, as well as 

 commercial species, is essential for implementing 

 a multispecies approach to fishery management 

 (Gulland 1977; Larkin 1978). 



Studies of the food habits offish communities in 

 the marine environment are becoming increas- 

 ingly popular. Most of the early effort was centered 

 on freshwater fish communities (e.g., Nilsson 

 1967; Keast 1970; Zaret and Rand 1971), but there 

 is now a growing literature on marine systems 

 (e.g., Tyler 1972; Hobson and Chess 1976; Kis- 

 lalioglu and Gibson 1977; Langton and Bowman 

 1980; Hunter^). These fish population studies are 



'Contribution No. 151, Ira C. Darling Center, University of 

 Maine at Orono, Walpole, ME 04573. 



^Graduate School of Oceanography, University of Rhode Is- 

 land, Kingston, RI 02881. 



part of a broader area of research in modern ecol- 

 ogy concerned with the question of how closely 

 related species coexist in communities. Patterns of 

 resource utilization by cooccurring species have 

 been studied to assess interspecific competition 

 and gain insight into community organization (see 

 review by Schoener 1974). 



The purpose of the present study is to examine 

 feeding relationships among demersal fishes in a 

 coastal area of the Gulf of Maine. Specifically, the 

 objectives are 1) to determine quantitatively the 

 principal prey species of the demersal fishes, 2 1 to 

 examine food resource division and interrelation- 

 ships among the predator species, and 3) to com- 

 pare predator diets with food resources potentially 

 available in the benthic infauna. 



METHODS 



I made monthly trawl collections of demersal 

 fishes in Johns Bay, Maine, from April 1978 

 through April 1979. A 5.5 m otter trawl was used 

 during the initial 3 mo of sampling. For the re- 

 mainder of the study I used a 9.1 m otter trawl. The 

 trawl had a 50.8 mm #15 nylon mesh with a 38.1 

 mm cod end. Trawls were made in approximately 



Manuscript accepted June 1981. 



FISHERY BULLETIN: VOL. 79, NO. 4, 1981. 



''Hunter, M. 1979. Food resource partitioning by demersal 

 fishes from the vicinity of Kodiak Island, Alaska. In S. J. 

 Lipovsky and C. A. Simenstad (editors!. Fish food habits studies 

 (Proc. 2d Fac. NW. Tech. Workshopi, p. 179-186. Wash. Sea Grant 

 Publ. WSG-WO-79-1. 



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