Publication Abstract

Feeding dynamics of cod larvae, Gadus morhua, on copepods in the western Irish Sea

A.B. Thompson and R. Harrop

Cod and other species of fish larvae, and nauplii and copepodite copepods, were sampled in the western Irish Sea in April/May 1988 and 1989. The diet of cod larvae was determined by gut analysis, and consisted almost entirely of copepods. The daily energy requirements of 3 sizes of cod larvae were determined from modified forms of published energetic models, and used to estimate numbers of copepods eaten per larva per day. The volume of water searched by larvae is modelled as a power function of larvae length. Modelling predictions indicate that cod larvae of < 5 mm length require high densities of copepod nauplii as they can search only small volumes of water. Larger larvae, 7.5 mm length, consume large numbers of copepodites and so require high densities of copepods to avoid depletion of the food resource. Observed copepod densities were sufficient for the energy requirements of the cod larvae populations at the densities observed in the western Irish Sea. However, when all species of larvae are considered, the model predicts that competition for food is likely to occur among larger larvae at observed copepod densities.

Reference:

A.B. Thompson and R. Harrop, 1991. Feeding dynamics of cod larvae, Gadus morhua, on copepods in the western Irish Sea. Marine Ecology Progress Series, 68: 213-223.