ABSTRACT. Body condition indices were assessed for pelagic juvenile cod (14 to 31 mm standard length, SL) over 2 cruises in spring 1987 in Canadian Atlantic waters on the southern Scotian Shelf. Three different indices determined from the residuals of univariate regressions were (1) triacylglycerol (TAG) content on standard length (SL), (2) dry body weight on SL, and (3) back-calculated change in SL from the peripheral 14 daily growth increments of the otolith on SL; hereafter referred to as TAGSL, DWTSL, and OTOSL respectively. Correlations between indices declined from TAGSL:DITSL (0.69, 0.64, cruises 87-1 and 87-2 respectively), to TAGSL:OTOSL (0.38. -0.05), to DWTSL:OTOSL (0.05, 0.03), a surprisingly low correlation considering that the indices were derived from the same individual. This pattern was also demonstrated by a principal component analysis (PCA), showing that after the first (size) component, otolith-based growth alone loaded on PC 2, then TAG contrasted with SL loaded on PC 3, and dry body weight showed the highest correlation with the starvation-independent SL. Supplementary analyses from 4 other cruises during 1985 and 1986 confirmed the weak correlation between DWTSL, OTOSL and other morphometric measures. All indlces were positively correlated with zooplankton biomass, but of the 16 separate cruise by index comparisons, only 6 were significantly correlated with zooplankton, of which 3 were the OTOSL. The rapld somatic/otollth growth of pelagic juvenile cod may respond rapidly to prey abundance, and rapid growth may preclude accumulation of Lipids (TAG), indicating that the utility of a con&tion lndex will depend on the species and life stage examined. Indices of recent otolith growth appear good measures of pelagic juvenile cod condition.

We examined the effect of natural variations in the concentration and size composition of plankton in coastal waters on the growth and survival of recently hatched larval capelin Mallotus villosus. Known numbers of larvae were stocked into 4 m3 j n sjtu enclosures, containing plankton communities whose size composihon and total particle concentration mirrored those occurnng naturally dunng times when the nearshore waters were alternately dominated by deep upwelled waters, and by warmer surface waters. Daily growth of larvae was unrelated to total plankton concentrahon, but strongly correlated with the concentrahon of plankton in the 40 to 51 pm (esd) size range. Daily mortality was negatively correlated with concentrations of plankton <81 pm (esd). This correlation was strongest with prey in the 32 to 40 pm and 40 to 51 pm (esd) size classes. The in situ concentration of plankton in the optimum size range for growth and survival was temporally dynamic and strongly influenced by wind-driven water mass exchange. The relevance of these findings to previous studies of the effect of prey concentration on growth and survival in larval fishes is discussed.