MEPS 412:189-205 (2010)  -  DOI: https://doi.org/10.3354/meps08687

ABSTRACT: Biodiversity can play an important role in the stability and resilience of ecosystems when these are faced with environmental change or anthropogenic impacts. Historically, the northwest Gulf of St. Lawrence had high fish egg and larval productivity. To assess changes in the ichthyoplankton community of this region, data from sampling surveys that were carried out in spring from 1985 to 1987 were compared with data from spring 2005 to 2007. Significant differences in ichthyoplankton abundances between the 2 decades and sampling times (May versus June) were revealed by multivariate analyses (nMDS, ANOSIM, PERMANOVA, and SIMPER) and univariate (ANOVA) analyses. Total ichthyoplankton abundance was lower in the 2000s than during the mid-1980s. Although larval sandlance Ammodytes spp. abundances did not change significantly, other taxa, such as Stichaeidae larvae and H4B eggs (gadids and merlucciid hakes, rocklings, butterfish Peprilus triancanthus, windowpane Scophthalmus aquosus and Gulf Stream flounder Citharichthys arctifrons), became more abundant; the abundance of CHW eggs (cod Gadus morhua, haddock Melanogrammus aeglefinus, witch flounder Glyptocephalus cynoglossus), and redfish Sebastes spp. larvae generally declined by more than an order of magnitude. Greenland halibut Reinhardtius hippoglossoides larvae also appeared in the 2000s assemblages. This dominance shift in the ichthyoplankton community reflects the demise of large fish predators and the response of the non-commercial species. Our study provides much-needed new information concerning current biodiversity and productivity of the fish community in the Gulf of St. Lawrence and insights into changes influenced by groundfish collapse and environmental fluctuations.

KEY WORDS: Ichthyoplankton assemblages · Community change · Multivariate analyses · Regime shift · Gulf of St. Lawrence