The Norwegian High Seas Reference Fleet (HSRF) reported one minke whale (Balaenoptera acutorostrata) by-caught in demersal trawl fisheries and one in a longline in the period 2011–2020. The HSRF comprises 25–30 concurrent fishing vessels larger than 15 m total length, contracted by the Institute of Marine Research to provide detailed reports on fishing effort, catch, and by-catch. The HSRF is designed to be as representative as possible for large fishing vessels in all of Norway. By-catch per effort for demersal trawl and longline fisheries was calculated based on data from the HSRF and extrapolated using effort data from the corresponding non-observed fleet (vessels ≥ 15 m) to obtain fleet-wide total by-catch estimates. The total by-catch in demersal trawl and longline fisheries was 57 whales for the 10-year period (95% CI: 0–157). No by-catch of minke whales was observed in other gear types (purse seine, Danish seine, and gillnets), but information from various sources indicates that there is an unknown amount of cryptic minke whale by-catch in other gears that we cannot currently quantify. Pot and creel fisheries, for example, were not covered by the HSRF, and there is a need to quantify by-catch in these fisheries. Notwithstanding undocumented sources of by-catch, the results show that even if 100% of minke whale by-catches are fatal, documented by-catch in Norwegian fisheries is only about 0.5% of the PBR and can be considered negligible from a sustainability perspective. Even so, minke whale by-catch is still a serious animal welfare issue.
This study reviews the reintroduction and development of grey seal (Halichoerus grypus) hunting in Sweden from 2001 to 2024, together with regional development of the seal population. Implementation of the hunting, together with geographical and temporal trends, as well as implications for management and ecosystem dynamics have been examined. The results provide an overview and support future assessments of protective and licensed hunting as potential tools to reduce conflicts between grey seals and coastal fisheries, while considering implications for ecosystem-based management and conservation. Data were compiled from national management documents, hunter-submitted records and national environmental monitoring programmes. Spatial and temporal patterns of hunting, quota allocations, retrieval rates, and grey seal population trends were examined. Results show that hunting began as protective hunting in northern counties and progressively expanded southwards, becoming nationwide along the Baltic coast by 2014. Seasonal timing of the hunting bag shifted from spring and autumn to late summer, and quota systems evolved from county-specific limits to nation-wide licensed hunting. Despite increased quotas and relaxed restrictions since 2020, the hunting bag did not increase, and the national quota was only fully utilized in 2024 when it was significantly reduced. Retrieval rates declined from 89% (2002–2013) to 57% (2014–2024), raising concerns about hunting efficiency and animal welfare. High regional hunting pressure relative to seal abundance was noted in several counties, with unclear implications for local population trends. Scientific support of grey seal hunting as an effective management measure to reduce seal-induced damage to fishing gear and catches is weak, and evidence of positive impacts on fish stocks is absent. The findings suggest that although grey seal hunting has been widely implemented, its demographic and ecological consequences remain uncertain. Key knowledge gaps persist regarding seal population dynamics, age and sex composition of hunted individuals, and broader ecosystem effects. As grey seals have low reproductive rates and face multiple anthropogenic threats, sustainable management requires improved data collection, spatially explicit ecological modelling, and an ecosystem-based approach. Continued monitoring and research are essential to evaluate long-term impacts of hunting and inform adaptive management strategies.
Over the past decade, anthropogenic noise from activities such as shipping has significantly increased in the ocean, raising questions on their potential impact on coastal species such as harbour seals. In this study, we assessed the spatial overlap between ships (equipped with AIS transmitters) and harbour seals (tracked using telemetry) in the English Channel, one of the densest shipping areas in the world. We then studied how their habitat selection varied according to environmental parameters taking into account shipping noise as a potential driver. A total of 28 harbour seals were captured and equipped with GPS-GSM tags. AIS data (ships > 15 m length) was used to estimate shipping traffic density and model the associated shipping noise. We then used generalised additive mixed models to assess harbour seals’ habitat selection using distance to haulout, distance to shore, bathymetry, tidal current, sediment type, and shipping noise as explanatory variables. The model selected had an explained deviance of 71.8%. Our findings indicate that distance to haulout sites was the primary driver of habitat selection (~91.5% deviance), while other environmental factors such as bathymetry (~4.4%), distance to shore (~3.1%), tidal current (~0.3%), sediment type (~0.6%), and shipping noise (~0.1%) had only minor influences on their selection. Despite a high spatial overlap between shipping activity and tracked seals (73% of overlap), the weak contribution of shipping noise suggests that either seals may be habituated to chronic noise exposure or that noise levels rarely exceed tolerance threshold levels. To the best of our knowledge, this is the first article integrating shipping noise into harbour seals’ habitat selection models. These findings provide an understanding of harbour seal habitat selection in anthropogenic environments.
We report results from follow-up field trials testing acoustic deterrents (pingers) as a measure to reduce harbour porpoise (Phocoena phocoena) by-catch rates in coastal gillnet fisheries in Norway. Twelve gillnet fishers conducted a total of 308 fishing trips, fishing with and without pingers in alternating weeks between January and April 2024. Harbour porpoises were by-caught in both pingered (9 porpoises) and control nets (25 porpoises), with most (~73%) taken in control nets. Average by-catch rates were calculated using a generalised linear mixed model (GLMM) approach. The average harbour porpoise by-catch rate was estimated at 0.061 (95% CI 0.034 – 0.098) porpoises per net km day in control nets and 0.031 (95% CI 0.011 – 0.060) porpoises per net km day in pingered nets. This shows that the by-catch rate in pingered nets was about 50% lower than in control nets (95% CI 0 – 83%). This estimate is lower (i.e. the pinger effect size is smaller) than a directly comparable study (Moan & Bjørge, 2023). Possible causes include limited sample size, the use of bait bags to attach pingers to the nets, reporting biases, and/or desensitisation/habituation of porpoises to the pinger sounds. Extra time use due to pingers was low, about two minutes per haul. The use of bait bags seems to have mitigated some, but not all the practical issues reported earlier. The pooled pinger effect size estimate using data from both Moan and Bjørge (2023) and the present study, was estimated at 72% (95% CI 44 – 89%).
Every year pinnipeds from five different species—gray (Halichoerus grypus), harbour (Phoca vitulina), harp (Pagophilus groenlandicus), hooded (Cystophora cristata), and ringed (Pusa hispida) seals—haul out on New York’s beaches. The locations of these animals are often in areas with high human density, resulting in negative interactions between humans and pinnipeds. These human interaction (HI) cases can include harassment, entanglement, and vessel trauma. Live pinniped strandings in New York, U.S.A., from 1996 through 2021 were examined to summarise characteristics, quantify the frequency and types of HI cases and assess overall spatiotemporal stranding trends. Of the 1,407 live strandings, 135 HI cases (55% involving gray seals) were documented. Notably, half of the HI cases involved entanglement in fishing gear or debris. The frequency of HI cases increased significantly over the study period, with more than one-third of cases occurring within the last 4 years. A significant positive correlation (p < 0.05) was observed between pinniped strandings (non-HI and HI) and boat access points, such as ramps and marinas, along a west-to-east gradient on Long Island. Understanding both non-HI and HI strandings is crucial to support the conservation of pinnipeds, as it provides essential insights into population trends, habitat changes, and the impact of human activities. These findings can inform targeted initiatives, such as training procedures for stranding response staff and volunteers, as well as the development of directed outreach materials, to foster greater awareness and proactive measures for species protection.
