Distribution and Lipid Composition of Pandalus Shrimp Larvae in Relation to Hydrography in West Greenland Waters

Abstract

The abundance and distribution of shrimp larvae were studied along four transects off West Greenland in June–July 1996. Zooplankton samples and vertical profiles of temperature, salinity, and fluorescence were obtained along the transects in order to relate larval distribution to hydrographical and biological characteristics. Eight species of shrimp larvae occurred in the samples; Pandalus montagui and Pandalus borealis were the most numerous constituting 61 and 29% of the larvae, respectively. Other species of shrimp larvae were, in declining order of abundance, Sabinea septemcarinata , Lebbeus groenlandicus, Spirontocaris spinus, Eualus galmardi, Pontophilus (norvegicus?), and Argis dentata. Pandalus shrimp larval density showed a significant positive association with mean fluorescence (5–80 m), but no association with mean temperature, or densities of copepod eggs and nauplii. However, most larvae were caught in water columns with temperatures and salinities of ~2°C. and ~33 psu, respectively. Abundance of P. montagui was negatively correlated with mean salinity and the proportion of P. montagui was higher in stations closest to the coast. Catches of P. montagui and P. borealis larvae were positively correlated (r = 0.729). Analysis for lipid class composition in P. montagui and P. borealis zoea stage 3 and 4 revealed that phospholipids were the most abundant lipid class (~80% of total lipid weight) followed by triacylglycerols (TAG) (10–15%), and wax esters (3–6%). TAG wet-weight ratios of P. montagui and P. borealis larvae were used as indices of feeding condition, and showed differences between larval species, zoeal stage, sampling station, and transect. In the same zoeal stage P. montagui larvae had higher TAG condition indices than P. borealis larvae suggesting that P. montagui may have a greater growth and survival potential. The TAG condition indices showed a significant negative association with fluorescence and indices of copepod productivity for stage 4 P. montagui larvae and no associations for P. borealis stage 3 and 4 larvae. Future studies should investigate lipid condition of the earliest stages of P. borealis and P. montagui larvae and establish trophic relationships (lipid nutrition) using food web tracer lipids. Such studies could be important to achieve better recruitment predictions for both species.