INTRASEASONAL AND INTERSEASONAL CHANGES IN THE RELATIVE CONDITION ANDPROXIMATE BODY-COMPOSITION OF BROAD WHITEFISH FROM THE PRUDHOE BAY-REGION OF ALASKA

A relative weight approach was used to rest the hypothesis that the co ndition of broad whitefish Coregonus nasus in the Prudhoe Bay region o f Alaska increases during the summer feeding season in conjunction wit h their increasing lipid and protein contents and decreases during win ter as fish consume these energy reserves. The conditions of individua l fish collected across 12 summer dissection periods from 1988 to 1993 were indexed in terms of their residual values relative to a single w hole-population, least-squares regression of log(e)(weight) against lo g(e)(length). Proximate body analyses of lipid and protein contents co llected from individual fish across six dissection periods from 1991 t o 1993 were also examined. Data pooled for individual year-classes wer e used to test for increasing mean residual value, mean lipid content, and mean protein content during summer and for decreasing values of e ach during winter. Of the 68 cases examined (14 year-classes over 6 ye ars), mean residual value changed in the expected direction in 56 inst ances (P < 3.0 E-7). Of 24 cases in which seasonal changes in lipid an d protein contents were available, lipid content changed in the expect ed direction in 23 instances (P < 3.0 E-6), and protein content change d in the expected direction in all 24 instances (P < 3.0 E-7). Mean re sidual value changed as expected in all 24 cases. The merits of relati ve condition-relative weight in the study of fish ecology are discusse d.