Nucleic acid contents and growth of first-feeding walleye pollock larvae in response to prey densities typical of sub-Arctic ecosystems

Abstract

The growth, nucleic acid and protein contents of walleye pollock Theragra chalcogramma larvae reared at prey densities of 10, 30, 50, and 500 prey 1-1 were measured for the first 9 days after the feeding initiation at 6° C. Incremental growth rates of larvae (mm day-1) were low and variable for the first 7 days after feeding initiation. Growth rates and rates of RNA, DNA, and protein accumulation by larvae reared at 500 prey 1-1 were positive while those of larvae reared at the lower prey levels did not differ significantly from zero. The RNA/DNA ratio was variable and exhibited no significant trend among food treatments. Estimates of instantaneous protein growth rates ranged from - 6·7 to 13·2% day-1 at food densities of 10 and 500 prey 1-1, respectively, and were moderately correlated with larval RNA/DNA ratios (r= 0·628). The results suggest that in situ protein growth rates of first-feeding pollock larvae may be influenced by prey fields within the range of ambient food densities reported for sub-Arctic ecosystems.