Food of Fifteen Northwest Atlantic Gadiform Fishes 



RICHARD W. LANGTON and RAY E. BOWMAN' 



ABSTRACT 



The food of l.i spocies of Ciidiform fishes occurring in the northwest Atlantic, from Cape Halteras. 

 N.C., to Nova Scotia, have been investigated for the years l'J(>9-72. The populations of Atlantic cod. 

 Gaitus morhua; pollock, I'otlachius iirens; silver hake, Merluccius biiinearis; white hake, Vrophycis 

 tenuis: offshore hake, Merluccius albidus; and eusk, Brosme brosme; have reasonably similar diets, 

 being primarily piscivorous. The red hake, Vrophycis chuss, and spotted hake. I'rophycLi rcnius, also 

 have similar diets and are mixed feeders, preying on both fish and invertebrates. The final seven 

 species, haddock. Melanogrammus aeglefinus; longfin hake, Phycis chesleri; fourbeard rockling. 

 Enchelyopus cimbrius: marlin-spike, Neiumia bairdi; longnose grenadier, Coelorhynchus car- 

 minatus; fawn cusk-eel. Lepophidium cervinum; and ocean pout, Macrozoarccs americanus; prey 

 almost exclusively on invertebrates. 



INTRODUCTION 



Investigations on the food habits of fish have been a 

 major topic of research since the beginning of fishery re- 

 search as a scientific discipHne. Since food availability 

 ultimately controls production, the literature has be- 

 come replete with papers describing, in detail, the prey of 

 numerous species of fish. This vast literature has concen- 

 trated on the more common commercially important 

 species, often at the expense of the lesser known but eco- 

 logically interesting fish. Among the Gadiformes de- 

 scribed in this report the literature on the cod and had- 

 dock was found to be the most extensive (see Literature 

 cited), reflecting the importance of the fishery for these 

 two animals, while comparative data on the food habits 

 of fish such as the spotted hake, red hake, and the gren- 

 adiers is either scanty or completely lacking, especially 

 for fish from the northwest Atlantic. 



In recent years some authors have suggested that man- 

 agement of a single fish species is untenable and that, in- 

 stead, the ecosystem must be considered as a whole (Gul- 

 land 1977). The commercially important species must be 

 considered in relation to their role in the total marine 

 environment. Edwards (1976) has gone so far as to say 

 that, in the context of total ecosystem management, fish 

 could be ignored as individual species and considered as 

 a group occupying a specified feeding niche. These niches 

 are dependent upon the fishes' food habits which are, in 

 turn, related to the morphology and size of the fish. Food 

 related size classes for fish have been identified as 

 "threshold lengths" by Parker and Larkin (1959) or 

 "feeding stanzas" by Paloheimo and Dickie (1965) and 

 Tyler (1972). In order to develop such a management 

 plan, however, it is first necessary to describe quantita- 

 tively the food of all the major fish populations occurring 

 within the bounds of the ecosystem and evaluate the role 



of each stock relative to the other fish in that same 

 system. 



This report describes the food of 15 northwest Atlantic 

 gadiform fish populations. 



METHODS 



Fish utilized for stomach contents analysis were 

 collected during six bottom trawl survey cruises con- 

 ducted on the following dates: 8 October-23 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. 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 belly were lined with 13 mm mesh netting to retain 

 smaller fish. A scheme of stratified random sampling was 

 conducted within the five geographic areas of the north- 

 west Atlantic (Fig. 1) and sampling continued over 24 h 

 per day." 



A total of 9,158 stomachs was collected from 15 spe- 

 cies of the Gadiformes. The fish were selected randomly 

 from the bottom trawl survey catch. Stomachs were ex- 

 cised aboard ship; labeled according to species, cruise, 

 and station; and preserved in 109c Formalin. The gen- 

 eral plan was to obtain a random sample of the popu- 

 lation for each species, without bias toward a specified 

 length or sex. Juvenile fish were preserved whole. Only 

 fish above a specified length are considered in this paper. 

 The species collected and their minimum fork lengths 

 are as follows: Atlantic cod, (ladus morhua (Linneaus), 

 >20 cm; haddock, Melanogrammus aeglefinus (Lin- 

 naeus), >20 cm; silver hake, Merluccius biiinearis (Mit- 

 chill), >20 cm; pollock, Pollachius uirens (Linnaeus), 



Northeast Fisheries Center Woods Hole Laboratory, National Marine 

 Fisheries Service, NOAA, Woods Hole, MA 02543. 



'Further details of the bottom trawl techniques may be obtained from 

 the Resource Surveys Investigation, Northeast Fisheries Center Woods 

 Hole Laboratory. National Marine Fisheries Service, NOAA, Woods 

 Hole, MA 02543. 



