LATVIA
The round goby challenge in Latvia
Researchers help create a resource from an invader Research by scientists at the National Institute of Food Safety, Animal Health, and Environment (BIOR) identiďŹ ed the best season to target round goby, and led to the development of specialised ďŹ shing gear.
Exponential increase in abundance from 2011 In Latvia it was first found in 2004 when some specimens were caught near the Liepaja coast, in the southern part of Latvian waters. The species abundance has since increased, and it became a target species for coastal fisherman. According to Latvian commercial fishery logbooks, it was first recorded in 2006 when the total annual catch was 6.3 kg. The catch climbed gradually till 2011 but increased sharply thereafter—from less than 1 tonne in 2011 to over 1,100 tonnes in 2018. By total landings, in recent years round goby is the second most fished species after herring in the Latvian coastal fishery. In all
likelihood, several factors contribute to this striking development—an increase in population size, market opportunities, and national fisheries policy. In the Baltic Sea, there are no catch quotas or other limitations on the round goby fishery. Thus, all management activities depend on national legislation and initiatives. In the beginning, round goby in Latvia was mostly fished as bycatch in the herring trap net fishery. To effectively utilise the abundant round goby resource, several management activities have been implemented in Latvia including the definition of specialised fishing gears and terms of use to minimise the bycatch of non-target species.
Gillnet surveys lead to useful insights The results from scientific coastal gillnet surveys were analysed by the Institute of Food Safety, Animal Health and Environment (BIOR). The analysis revealed that the best mesh size and fishing season for round goby was in spring (April-June) using nets with a 60-70Â mm (diagonal width) mesh. This information led to the start of a dedicated round goby fishery back in 2015. Additionally, in cooperation with local fishermen, the researchers tested the
E. Knospina
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he round goby (Neogobius melanostomus) is a demersal benthivorous fish species of Ponto-Caspian (the region around the Black Sea, Caspian Sea, and Sea of Azov), origin. Since its introduction via ship ballast water discharge in the early 1990s it has successfully spread in the coastal waters of the Baltic Sea, and today is considered one of the top invasive species. One of the highest round goby commercial landings in the Baltic Sea is observed currently in Latvian coastal waters.
The round goby (Neogobius melanostomus) is an invasive species in the Baltic Sea. Scientists from BIOR have helped to develop a commercially viable fishery for the invader.
effectiveness of fyke nets specialised for round goby fishing. As a result, a new fishing gear—the round goby fyke net—has been used in Latvia since 2018. Both gears in combination with the spatial and seasonal boundaries led to an increase in round goby fishing selectivity and significantly contributed to the record catch of 2018. Since then, landings have decreased and it seems the first wave of the invasion is over, but the main reason, however, is unclear. One the one hand, it can be related to the increased fishing effort, but on the other hand, it can also reflect changes in the ecosystem.
An invasive species that is both predator and prey Local studies in Latvia suggest that round goby distribution is related to depth and bottom substrate. The highest round goby densities with 1-3 fish per m2 were found at rocky and mixed substrate bottoms at depths ranging from 10 to 15 meters in the southern coastal regions. Round goby diet composition depends on the fish size and depth zone (habitat type). At all depths, the bivalves Mytilus spp. (blue mussels) and Limecola balthica are the preferred prey. The decreasing
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