A changing North Sea: The potential effects of marine heatwaves on shrimp abundances in the Belgian part of the North Sea
Vertongen, B. (2024). A changing North Sea: The potential effects of marine heatwaves on shrimp abundances in the Belgian part of the North Sea. MSc Thesis. UGent. Faculteit Bio-ingenieurswetenschappen: Gent. 96 pp.
The European brown shrimp ( Crangon crangon) is deeply embedded in the Belgian culture. Since the Middle Ages, people have fished this coastal dweller to consume or to sell as food source. Despite a diminishing fishing fleet, the brown shrimp fishery remains a vital economic sector along the Belgian coast. However, in recent years, the availability of shrimp was subjected to some severe fluctuations. Years with large commercial landings were altered by years of markedly low catches. For instance, in 2023, reduced commercial landings led to a substantial increase in shrimp prices, resulting in economic challenges for fishermen and vendors. To date, neither fishermen nor scientists have been able to identify the cause(s) of these fluctuations. This dissertation aims to identify the major influences on the recruitment process of Crangon crangon and to correlate recent fluctuations of shrimp abundance with prevailing environmental conditions. Initially, the occurrence of marine heatwaves (MHWs) in the Belgian Part of the North Sea (BPNS) was hypothesized to be one of the main drivers behind the variating abundances. Marine heatwaves are events during which water temperature exceeds a certain threshold value over a certain time period, resulting in anomalously high water temperatures. The majority of these MHWs have an anthropogenic origin as they are associated with climate change. Globally, MHWs are occurring with increasing frequency, thereby impacting marine life and associated ecosystem services. In the BPNS , it was observed that in years marked by intense MHWs (e.g. 2018, 2022), an increased number of commercial landings was noted. Therefore, the correlation between (elevated) water temperatures and shrimp abundances was initially investigated. However, as Crangon crangon stocks do not solely depend on water temperature, several other environmental parameters such as food availability or predator abundance were also included.
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