Abstract
The European lobster (Homarus gammarus) forms the base of an important fishery along the coasts of Europe. However, stocks have been in decline for many years, prompting new regulations in the fishery and also restocking efforts. An important feature of any restocking effort is the assessment of success in the number of released juveniles that stay and become adult over time. Here, we tested the power of a single nucleotide polymorphism (SNP) DNA marker panel developed for population assignment to correctly infer parentage on the maternal side of lobster larvae, in the absence of known fathers, using lobsters included in a current restocking effort on the Swedish west coast. We also examined the power to reconstruct the unknown paternal genotypes, and examined the number of fathers for each larval clutch. We found that the 96-SNP panel, despite only containing 78 informative markers, allowed us to assign all larvae to the correct mother. Furthermore, with ten genotyped larvae or more, confident paternal genotypes could be reconstructed. We also found that 15 out of 17 clutches were full siblings, whereas two clutches had two fathers. To our knowledge, this is the first time a SNP panel of this size has been used to assess parentage in a crustacean restocking effort. Our conclusion is that the panel works well, and that it could be an important tool for the assessment of restocking success of H. gammarus in the future.
Highlights
The world’s oceans are continuously experiencing stronger and stronger fishing pressure, and presently there are few fisheries that are exploited less than to the maximum sustainable yield
Many fisheries have introduced restocking efforts, where fish or shellfish are raised in aquaculture environments from eggs to juvenile life stages, and released into the wild
The mean genotyping rate per locus was 95.7%. 27 out of the 78 polymorphic single nucleotide polymorphism (SNP) were significantly deviating from Hardy–Weinberg equilibrium (Supplementary Table S2), which was expected as the dataset does not consist of randomly mating individuals
Summary
The world’s oceans are continuously experiencing stronger and stronger fishing pressure, and presently there are few fisheries that are exploited less than to the maximum sustainable yield. About 30% of the world’s marine fish stocks are currently fished at biologically unsustainable levels (FAO 2020), a fraction which is currently increasing. A number of actions have been undertaken in order to minimize unsustainable practices, including implementation of no-take zones, fishing quotas, size limits, along. Many fisheries have introduced restocking efforts, where fish or shellfish are raised in aquaculture environments from eggs to juvenile life stages, and released into the wild In order to distinguish hatchery-reared individuals from wild ones in later life stages, a variety of different methods have been used, including different types of staining (Camp et al 2013) and electronic tags (Nzau Matondo et al 2019). The large-scale effects of restocking efforts have to date been difficult to assess, and in many small-scale efforts where evaluations have been possible the costs seem to outweigh the benefits (Kitada 2018)
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