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

The growth, nucleic acid and protein contents of walleye pollock Theragra chalcogramma larvae reared at prey densities of 10, 30, 50, and 500 prey l-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 l-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 l-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.