Marine larval fish assemblages in the nearshore Canadian Beaufort Sea during July and August

The distribution and composition of marine larval fish were investigated during a three-year multidisciplinary project conducted in the nearshore Canadian Beaufort Sea in July and August, 2003-2005. Larvae were sampled using replicated bongo net (500mum) tows within 50 m water depth. A total of 454 larval fish were captured from seven families. Arctic cod ( Boreogadus saida) was the most abundant species and the most widely distributed within the estuarine zone (20-50 m). Other larval fish families that were represented in this zone were Cottidae, Stichaeidae, Liparidae and Agonidae. Pacific Herring (Clupea pallasii pallasii) were dominant in the coastal, shallow waters (<20 m).;Multivariate statistical analyses revealed two distinct larval assemblages that were closely correlated to water masses. The two assemblages were defined as coastal and estuarine. The coastal assemblage was found in the shallow (<20 m) Intense plume water mass. This area is greatly influenced by the Mackenzie River outflow and was dominated by Pacific Herring. The estuarine assemblage was dominated by Arctic cod and was often found in stratified waters in areas beyond the Mackenzie Plume frontal zone (>20 m). This assemblage also had the greatest species richness.;In addition to determining the current status of larval fish distributions (2003-2005) this study also examined historic (1985-1987) Northern Oil & Gas Action Program (NOGAP) larval fish data for a hotspot and biogeographic analysis. Results indicated that both species richness and larval density was greatest in Kugmallit Bay (20-50 m) suggesting that this area was an important nursery ground for larval fish and requires enhanced protection and monitoring.;Parametric and non-parametric analyses revealed no significant differences in larval fish densities or diversity at stations identified by sea floor features and those which did not have a feature present. Features identified in this study were not found to be areas of retention for larval fish and therefore were found to be opportunistically transported to these areas by currents and water masses.