Prey size selection through larval development in Irish Sea cod (Gadus morhua), haddock

No abstracts are to be cited without prior reference to the author.

Diets of cod, haddock and whiting were studied in terms of prey size throughout development from the yolk-sac to juvenile stage. Cod and whiting consumed prey of a similar size at the onset of feeding (late yolk-sac stage), while haddock selected smaller sized prey. As expected larger sized prey were taken with increasing larval development. This increase in prey size was consistent between cod and whiting but at a greater rate in haddock. Due to this more rapid prey size increase at a length of ~11mm haddock took the largest prey size. When the difference between maximum and minimum prey sizes through development were studied it was suggested that haddock would have a larger prey niche breadth. However, the calculation and analysis of niche breadth data suggested that cod and haddock did not differ in niche through development, though the relationship to the data was poor in both cases. The general suggestion from these data are that the interspecific competition for food between these closely related gadoid species may be reduced as a result of differing prey size selection by haddock.