Evaluation of Atlantic cod predation on American lobster in the southern Gulf of St. Lawrence, with comments on other potential fish predators

Dermersal fishes are widely thought to be an important source of natural mo rtality for juvenile American lobster Homarus americanus. There were no sig nificant relationships between abundance indices of American lobster and th e dominant demersal fish species, Atlantic cod Gadus morhua, in the souther n Gulf of St. Lawrence. American lobster was found in only one of 22,625 At lantic cod stomachs collected between 1955 and 1980-a period of low America n lobster abundance. Only six of 12,008 Atlantic cod collected between July 1990 and October 1996 (a period of high American lobster abundance) had ea ten American lobster. Most size-classes of the two species were spatially s eparate from early July to early September and November to May. American pl aice Hippoglossoides platessoides, the second most abundant demersal fish s pecies, did not eat American lobster (n = 1,800 stomachs). Again, the two s pecies were spatially isolated for most of the year. More limited studies ( in terms of spatial or seasonal coverage) on the diets of eight shallow-wat er fish species (n = 4,674 stomachs) detected consumption of American lobst er by shorthorn sculpin Myoocephalus scorpius, cunner Tautogolabrus adspers us, and white hake Urophysis tenuis but not by winter Bounder Pleuronectes americanus, yellowtail Bounder P. ferruginea, thorny skate Raja radiata, sp iny dogfish Squalaus acanthias, or Greenland cod Gadus ogac. This study eli minated Atlantic cod, Greenland cod, American plaice, yellowtail Bounder, w inter flounder, and thorny skate as important predators of American lobster in the southern Gulf of Sr. Lawrence; however, the question of which of th e remaining demersal fish species are important predators of American lobst er remains largely unresolved.