Maturation at a young age and small size of European smelt (Osmerus eperlanus): A consequence of population overexploitation or climate change?

Timo Arula,Markus Vetemaa,Tiit Raid,Heli Shpilev,Anu Albert

doi:10.1186/s10152-017-0487-x

Timo Arula, Markus Vetemaa + Show 3 more

Open Access

https://doi.org/10.1186/s10152-017-0487-x

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Abstract

Age of fish at maturation depends on the species and environmental factors but, in general, investment in growth is prioritized until the first sexual maturity, after which a considerable and increasing proportion of resources are used for reproduction. The present study summarizes for the first the key elements of the maturation of European smelt (Osmerus eperlanus) young of the year (YoY) in the North-eastern Gulf of Riga (the Baltic Sea). Prior to the changes in climatic conditions and collapse of smelt fishery in the 1990s in the Gulf of Riga, smelt attained sexual maturity at the age of 3–4 years. We found a substantial share (22%) of YoY smelt with maturing gonads after the collapse of the smelt fisheries. Maturing individuals had a significantly higher weight, length and condition factor than immature YOY, indicating the importance of individual growth rates in the maturation process. The proportion of maturing YoY individuals increased with fish size. We discuss the factors behind prioritizing reproduction overgrowth in early life and its implications for the smelt population dynamics.

Highlights

Age of fish at maturation depends on the species and environmental factors but, in general, investment in growth is prioritized until the first sexual maturity, after which a considerable and increasing proportion of resources are used for reproduction, and growth rates decrease from maturity onwards [1]
We detected a number of changes in winter air temperature, Sea surface temperature (SST) and prey abundance in the environment inhabited by Gulf of Riga (GoR) smelt in early life stages in Pärnu Bay (PB) that could be linked to the relatively high number of maturing young of the year (YoY) smelt observed in 2012
In the current study, we demonstrated for the first time a relatively high (22%) proportion of YoY smelt with maturing gonads during November and December of 2012

Summary

Introduction

Age of fish at maturation depends on the species and environmental factors but, in general, investment in growth is prioritized until the first sexual maturity, after which a considerable and increasing proportion of resources are used for reproduction, and growth rates decrease from maturity onwards [1]. Exploited fish stocks have been shown to produce individuals that start first maturation at a younger age and smaller size [4]. This phenomenon can be accompanied by size-selective harvesting that eliminates the faster-growing genotypes, favouring slow-growing individuals that mature at smaller sizes. A decreasing population growth rate resulting from high exploitation might lead to individuals maturing earlier, with this trait retained by future generations even when the population size increases again. This indicates that size-selective harvesting has removed the faster-growing

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