The population dynamics and energetics of a species of pelagic Antarctic fish, Pagothenia borchgrevinki - length, weight, stomach content, parasites, fecundity, pattern of feeding, respiration experiments

The population dynamics and energetics of a species of pelagic Antarctic fish, Pagothenia borchgrevinki was studied. Fish were captured using silver lures with treble hooks and fish traps baited with seal meat or dead fish. Fish were processed after capture. The length of each fish was measured, eviscerated and viscerated weights taken and parasites and stomach contents collected. Scales and otoliths were collected from the first 160 fish caught to determine the age structure of the fish population. Ovaries were collected and preserved in some fish for the analysis of fecundity and productivity. On two days, a series of fish were caught at six hourly intervals to see if there was any diurnal pattern in feeding behaviour. A reference collection of under-ice plankton was made for comparison with stomach contents of the fish and other plankton were frozen for later determination of their calorific values. An additional 200 fish were caught, frozen whole and returned to New Zealand to obtain further information on populaton dynamics and bomb calorimetry. Respiration experiments were carried out using different size class of fish placed in a respirometer and lowered 2m below the sea ice. Respiration rate was determined by measuring the oxygen depletion in a closed system. Parasites were collected from some of the fish caught including copepods, leeches, cestodes, trematodes, nematodes and monogenea. Parasites were prepared for identification and for demonstration slides used in teaching.