European lobster stocking requires comprehensive impact assessment to determine fishery benefits

Abstract

Historically, hatcheries in Europe and North America attempted to contribute to the conservation and enhancement of clawed lobster stocks, but lacked monitoring programmes capable of assessing success. In the 1990s, this perspective was changed by the results of restocking and stock enhancement experiments that inserted microwire tags into hatchery-reared juvenile European lobsters (Homarus gammarus) before release. This allowed recapture in sufficient numbers to prove that lobsters had survived and recruited to the mature fishable stock. However, evidence of recruitment still failed to answer key questions about the ultimate ecological and economic benefits. As a result, a growing number of lobster stocking ventures remain hindered by a lack of clear evidence of the effects of their stocking schemes. This review evaluates these experiments and related studies on other fished species, summarizes key findings, and identifies data and knowledge gaps. Although studies of fitness in cultured lobsters provide some of the most encouraging results from the wider field of hatchery-based stocking, the limitations of physical tagging technology have significantly hindered appraisals of stocking impacts. We lack basic knowledge of lobster ecology and population dynamics, especially among prerecruits, and of the impact of stocking on wild lobster population genetics. We advocate the use of genetic methods to further our understanding of population structure, rearing processes, and stocking success. We also recommend that more focused and comprehensive impact assessments are required to provide a robust endorsement or rejection of stocking as a viable tool for the sustainable management of lobster fisheries.

Population genetic structure in European lobsters: implications for connectivity, diversity and hatchery stocking

“…The European lobster Homarus gammarus L. is a decapod crustacean inhabiting the coastal shelf seas of the eastern North Atlantic and has been the subject of hatchery stocking in recent decades (Ellis et al 2015a). The lobster ranges from Arctic Norway to Morocco, including the semi-enclosed seas of the Mediterranean and the Kattegat, bounded by the Black Sea and Baltic Sea, respectively (Jørstad et al 2004, Triantafyllidis et al 2005.…”

“…The lobster ranges from Arctic Norway to Morocco, including the semi-enclosed seas of the Mediterranean and the Kattegat, bounded by the Black Sea and Baltic Sea, respectively (Jørstad et al 2004, Triantafyllidis et al 2005. The species' market value makes it highly prized by trap fishers, so stocks are of great importance to inshore ecosystems and the traditional fishing communities that they support (Ellis et al 2015a). However, overexploitation during the 20th century led to severe stock depletions across regions including Scandinavia and the Mediterranean, from which recovery has since been slow or absent (Ellis et al 2015a).…”

“…The species' market value makes it highly prized by trap fishers, so stocks are of great importance to inshore ecosystems and the traditional fishing communities that they support (Ellis et al 2015a). However, overexploitation during the 20th century led to severe stock depletions across regions including Scandinavia and the Mediterranean, from which recovery has since been slow or absent (Ellis et al 2015a). This has encouraged the rearing of H. gammarus larvae in aquaria-based hatcheries to produce juvenile lobsters for release to supplement productive fisheries and restore yields in heavily depleted areas (Addison & Bannister 1994).…”

“…Larvae from these females are reared, and then later released, in communal cohorts based on the date of hatch (Ellis et al 2015a). This risks the introduction of individuals beyond the natural spatial range of their subpopulations.…”

SNP discovery in European lobster (Homarus gammarus) using RAD sequencing

“…Scandinavia, Mediterranean) and from which recovery has been slow or stagnant (Kleiven et al 2012). This has led to the rearing of H. gammarus larvae in lobster hatcheries to produce juveniles which are released into the wild to supplement productive stocks where the risk of over-exploitation is high (Ellis et al 2015).…”