Multidecadal dynamics of larval gobies Pomatoschistus spp. in response to environmental variability in a shallow temperate bay

Compared to commercial fish, there is relatively limited information available about the dynamics of non-commercial fish that very often play important structural and functional roles in marine ecosystems. Long-term investigations that provide quantitative estimates of the population dynamics as a function of environmental variability are needed to understand the ecology and role of the non-commercial fish in the ecosystem, and assist the ecosystem management where relevant. Here we analyze the inter-annual variability and long-term trends of the abundance of the larval non-commercial gobies Pomatoschistus spp. in a shallow coastal bay (Pärnu Bay, northeastern Baltic Sea) in 1959-2010, in relation to climate and prey field related variables. The abundance of larval Pomatoschistus spp. decreased over the last 50 years along with the concomitant decrease in the water transparency. The first appearance of larvae has shifted for about two weeks earlier and is mostly related to the timing of ice cover breakdown. However, some of the effects of the environmental forcing on larval fish may be obscured by the uncertainty of species identification of individuals of the genus Pomatoschistus at larval stage, and the investigated population of Pomatoschistus spp. consists of at least two species with slightly different ecologies and also environmental preferences.