Abstract
During the last decades the number of grey seals Halichoerus grypus has increased more than tenfold in the Baltic Sea. having reached 38 000 in 2019, which has created increasing problems to the coastal fisheries. In the current study, 151 Estonian coastal fishermen were interviewed to sum all direct and indirect monetary losses. The total cost of the damage caused by seals to the Estonian fisheries was around 0.9 million euros in 2009. With the aim of mitigating seal impact, Acoustic Harassment Devices (AHDs, Lofitech) were tested. This study presents quantitative data on seal damage in Estonian trap-net fisheries and analyses the results of the attempts made to mitigate the damage by means of AHDs. It can be concluded that AHDs provided sufficient protection against the seal attacks.
Highlights
Following the ban of several harmful substances (DDT, PCB, etc.), the number of grey seals Halichoerus grypus in the Baltic Sea has grown more than tenfold from ca 2000 in the 1970s to ca 38 000 counted seals in 2019 (HELCOM 2020)
This study presents quantitative data on seal damage in Estonian trap-net fisheries and analyses the results of the attempts made to mitigate the damage by means of Acoustic Harassment Devices (AHDs)
Based on the interviews with fishermen, it was calculated that the economic loss caused by seals to the Estonian coastal fisheries was around 0.9 million euros in 2009
Summary
Following the ban of several harmful substances (DDT, PCB, etc.), the number of grey seals Halichoerus grypus in the Baltic Sea has grown more than tenfold from ca 2000 in the 1970s to ca 38 000 counted seals in 2019 (HELCOM 2020). If compared to other Baltic fisheries, the problem is most severe in the coastal gill-net and trap-net fisheries for salmon Salmo salar, sea trout Salmo trutta and whitefish Coregonus lavaretus, where grey seals frequently visit the traps (Lehtonen and Suuronen 2004). Since the monetary losses severely impact fisheries, there is an acute need for solutions that could prevent or discourage seals from entering the traps, where they eat catch or scare it out. Another way to address the problem is by the removal of so-called “problem seals”, animals specializing in raiding e.g. salmon traps (Graham et al 2011; Königson et al 2013; Suuronen and Lehtonen 2012). Instant and timedependent effects may differ considerably between the type of the AHD, fishing gear, seal species, and many other factors (Fjälling et al 2006)
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