Interactions between marine mammals and fisheries: Assessing impacts and possible solutions

To achieve a sustainable and viable coastal fishery, it is essential to assess and find solutions for the interactions between marine mammals and fisheries. These interactions are reciprocal: marine mammals can impact fisheries, and fisheries can affect marine mammal populations. The most common marine mammal in Swedish waters is the grey seal. Harbour seals, ringed seals, and harbour porpoises also inhabit the area. As the seal populations has grown, seal-induced damage to catches and fishing gear has increased, causing significant costs to coastal fishers. Conversely, fisheries can negatively impact marine mammals. Bycatch is a significant threat to many species, such as the harbour porpoise in the Baltic Sea.

The overall objective of my future research is to determine if and how small-scale fisheries in the Baltic can be economically viable, sustainable, and supportive of ecosystem-based management. This involves assessing interactions with marine mammals and fisheries as well as developing solutions towards a sustainable and viable coastal fishery.

It is crucial to assess the impact of increasing seal populations on various coastal fisheries to implement effective mitigation strategies that ensure a sustainable and viable coastal fishery. These assessments, along with science-based evaluations of the effectiveness of proposed measures, are key focus areas of my research. Mitigation measures are tested for their efficiency in targeting specific species and their overall impact on the ecosystem. Given that seal depredation and damage are major threats to small-scale fisheries, future fishing gear development must prioritize being both seal-safe and environmentally sustainable. Passive gears such as pots, fyke-nets, or trap-nets are considered selective and environmentally friendly, and they can also be made seal-safe. The effectiveness of these passive gears largely depends on the behavior of the target fish in relation to the gear, an area that remains unexplored for many fish species. Future research will focus on assessing the impact of seals on fisheries and developing potential seal-safe gears, including fyke-nets and trap-nets designed for multiple species such as cod, turbot, whitefish, and perch. Additionally, it will involve gaining new insights into the behavior of target fish relative to the gear to optimize gear design for maximum efficiency.

There is a widespread need to estimate the impact of fisheries on marine mammals to improve management, better protect populations, and reduce bycatch. Since marine mammal bycatch occurs sporadically, large sample sizes over extended periods are necessary to obtain reliable estimates of bycatch rates. My future research will focus on developing effective methods for monitoring marine mammal bycatch. Electronic Monitoring (EM), which uses cameras, is considered a reliable alternative to onboard observers and has been implemented within the national data collection framework. EM and other electronic devices offer several benefits, including high compliance rates and the ability to collect large amounts of data needed to assess bycatch. However, collecting, storing, and analyzing this data can be costly and time-consuming. One promising area of future research is using machine learning (ML) to automate species identification in onboard electronic monitoring systems. More reliable monitoring data on bycatch can provide new insights into the key factors influencing bycatch rates of marine mammals in small-scale fisheries, which is another area of my research. Identifying these factors will enable the development of effective management strategies to minimize bycatch.

Assessing the interaction between marine mammals and fisheries helps identify where mitigation methods are needed to reduce these interactions. One effective mitigation method is to find alternative fishing gears for fisheries that experience high levels of interaction. Another mitigation measure involves using acoustic deterrent devices to reduce bycatch or seal depredation. When these devices are used to decrease bycatch of harbour porpoises, they are called pingers. When used to deter seals from fishing areas, they are known as seal scarers. While some pingers and seal scarers have proven effective, newly developed devices using novel sound frequencies require evaluation of their impact and effectiveness. In addition, there is a critical need for research into the long-term use of acoustic deterrents, assessing both their effectiveness and potential negative impacts. This knowledge is crucial to determine their viability as future mitigation measures. Therefore, my future objective is to gain knowledge on the longterm impact and effectiveness of acoustic deterrent devices, including seal scarers and pingers, in reducing bycatch and deterring seal depredation in fishing areas.