Multidecadal dynamics of larval gobies Pomatoschistus spp. in response to environmental variability in a shallow temperate bay Kerli Laur a, * , Henn Ojaveer a , Mart Simm b , Riina Klais a a Estonian Marine Institute, University of Tartu, Lootsi 2a, 80012 Pärnu, Estonia b Estonian Marine Institute, University of Tartu, Mäealuse 14,12618 Tallinn, Estonia article info Article history: Received 13 May 2013 Accepted 11 November 2013 Available online 18 November 2013 Keywords: fish larvae long-term changes abiotic factors prey density Baltic Sea coastal waters abstract 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 1959e2010, 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 envi- ronmental preferences. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction In-depth knowledge of the abundance and distribution of early life-history stages provides important insights to the ecology of fish populations and communities. The most critical time in the life history of fish is the larval stage when the highest mortality occurs (Hjort, 1914; Cushing, 1975). The early life history stages of fish are particularly susceptible to the variability of the environment and are affected by both, the biological (e.g. abundance of food) as well as the physical factors such as water transparency, temperature and salinity (e.g. Fiedler, 1986; Somarakis et al., 2002; Genner et al., 2010). Temperature is an important factor controlling seasonal abundance pattern of larval fish through various mechanisms and processes (e.g. Marques et al., 2006; Genner et al., 2010). Abiotic factors, food limitation and starvation together can explain high mortality in the early larval stage, and the decline of abundance of fish larvae (e.g. Bochdansky et al., 2008), resulting either from declining abundance of prey or mismatch with prey due to earlier/ later appearance. Gobies Pomatoschistus spp. are small-sized short-living abun- dant fish (Fonds, 1973). They constitute a significant part of demersal fish communities form the Mediterranean up to Norway including the Baltic Sea (e.g., Hesthagen, 1977; Psuty-Lipska and Garbacik-Wesolowska, 1998). In the Baltic Sea, there are at least two Pomatoschistus species: sand goby P . minutus and common goby P . microps. They are well-adapted to the brackish conditions prevailing in the estuaries (e.g. Bouchereau and Guelorget, 1998). Temperature requirements differ between the adults as P. microps is more of a warm water species (Fonds, 1973). As a consequence of lower spawning temperature, P. minutus may reproduce earlier in the season and benefit from longer period of growth before the onset of winter (Wiederholm, 1987). In northern areas gobies are known to avoid low temperatures and migrate to deeper offshore areas in winter and return to shallower areas again in March when the water temperature increases (Fonds, 1973). P. minutus is prob- ably the first to migrate back to shallower areas to spawn and P. microps dominates in summer when the water temperature is above 20  C. Pomatoschistus spp. are batch spawners that develop and releases multiple batches of eggs within a spawning season * Corresponding author. E-mail address: kerli.laur@ut.ee (K. Laur). Contents lists available at ScienceDirect Estuarine, Coastal and Shelf Science journal homepage: www.elsevier.com/locate/ecss 0272-7714/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ecss.2013.11.011 Estuarine, Coastal and Shelf Science 136 (2014) 112e118