ICES Journal of Marine Science

Feyrer, Laura J; Colbourne, Natalie; Lawson, Jack W; Moors-Murphy, Hilary B; Ferguson, Steven H

doi: 10.1093/icesjms/fsaf140pmid: N/A

Marine mammals adapt foraging strategies in response to human activities and environmental change, often resulting in conflicts with fisheries. Whale-fishery interactions, including depredation and entanglement, pose significant challenges for both marine conservation and fisheries management. This study presents the first comprehensive, multi-fishery analysis of marine mammal behaviour and gear-associated incidents using at-sea observer (ASO) records collected between 1990 and 2023 across Canada’s North Atlantic. The final dataset comprised 5184 marine mammal sightings reported by ASOs across multiple fisheries. The aims were to: (1) assess the severity of incident records, ranging from close approaches, depredation, injury, entanglement, and death; (2) calculate the minimum frequency of sightings and incidents by gear type and target species; and (3) identify trends in depredation incidents across species and fisheries. Results reveal widespread depredation behaviour by deep-diving northern bottlenose (Hyperoodon ampullatus) and sperm whales (Physeter macrocephalus), particularly in Greenland halibut (Reinhardtius hippoglossoides) fisheries. Gillnets and bottom trawls were responsible for most entanglement incidents, with small odontocetes like harbour porpoises (Phocoena phocoena) experiencing relatively higher rates of severe entanglement. Entanglement rates for endangered northern bottlenose whales exceeded limits considered sustainable under current recovery objectives. Minimum annual incident rates exceeded 3 observed events per year for long-finned pilot whales (Globicephala melas) and 1.8 for harbour porpoises, across all reported sightings. Risks varied across regions, gear types, and species. These findings highlight the need for fishery-specific mitigation, spatial management, and expanded observer coverage to reduce harmful interactions and promote long-term coexistence between marine mammals and fishing operations.

Andrade, Sidney M V; Bayse, Shannon M; Snook, Morgan; Kelly, David; Winger, Paul D; DeLouche, Harold; Araya-Schmidt, Tomas; Santos, Mark R

doi: 10.1093/icesjms/fsaf150pmid: N/A

Large Greenland sharks (Somniosus microcephalus) are captured as bycatch in northern shrimp (Pandalus borealis) bottom trawls by becoming stuck in the Nordmøre grid system. Grid systems do not easily exclude Greenland sharks due to their large size (up to 6 m in length). Thus, an additional or modified bycatch reduction device (BRD) should be considered to promote a quick escape. Two experimental BRD systems were designed and tested to facilitate the escape of large-sized Greenland sharks: 1) a large escape opening at the grid (increased from 113 to 250 cm) and 2) a sieve panel with a large escape opening before the traditional grid system. Catch rates (kg tow−1) and size selectivity were compared between the experimental and traditional treatments. Results for the large escape opening treatment versus the traditional gear showed no difference in northern shrimp catch rates (P-value = 0.237), however size selectivity was different between treatments (P-value = 0.033) with a slight reduction for large length sizes. Conversely, the catch rates of northern shrimp were significantly reduced for the sieve panel treatment (18% reduction; P-value < 0.001) but showed no difference in size selectivity (P-value = 0.388) across all length classes. No Greenland sharks were observed during sea trials, and total bycatch was minimal. In conclusion, the large escape opening showed promise as a technique to reduce megafauna bycatch, such as Greenland shark, by providing a large escape area while having minimal effects on northern shrimp catch. However, the sieve panel treatment, as tested, likely loses too much northern shrimp to be considered in the fishery.

Rosciszewski-Dodgson, Michael J; Cirella, Giuseppe T

doi: 10.1093/icesjms/fsaf136pmid: N/A

Global fish stock collapses caused by overfishing have led to increasingly stringent regulatory measures, posing serious challenges to the livelihoods of fishing communities. This study examines the resilience of different fishing sectors—categorized by vessel size (fishing boat, cutter, supercutter) and target species (demersal, mixed, small pelagic)—in response to changes induced by management measures, using the 2019 cod ban in the Baltic Sea as a case study. A mixed-methods approach was employed, combining a Likert-scale survey of 129 respondents across 17 fishing harbours with semi-structured interviews of 28 fishermen to obtain detailed quantitative and qualitative insights into the impact of the cod ban across different vessel sizes and fishing activity groups. Fishing boats, the smallest vessels, emerged as the least resilient due to their limited gear and target species flexibility. In contrast, cutters and supercutters involved in mixed or small pelagic activities demonstrated moderate resilience. A notable finding was that the cod's ban had direct and indirect impacts across all fishing types, highlighting how regulatory decisions targeting a single stock can trigger ripple effects throughout the entire fisheries sector. Stocks are carefully allocated across registered vessels, removing access to one species such as cod, not only affects those who directly depended on it, but also leads to redistribution of quotas and restrictions that influence all groups. The reduction in small pelagic quotas to support cod recovery has also added pressure to sectors that did not directly target cod. Cutter operators reported the greatest economic distress, with many facing difficulties adapting to new quota limits due to high operational costs and low profitability. Conversely, some fishing boats and supercutters displayed greater flexibility, though reduced quota access of sprat and herring stocks and the limited economic viability of alternative fisheries such as flounder continue to pose challenges for many fishermen. The Friedman test reinforced the notion that vessel size and target species function together to determine how fishermen respond to change. The study highlights the need for more nuanced policy responses that account for the wider effects of stock closures on different vessel types and fishing activities.

Preti, Antonella; Muhling, Barbara A; DiNardo, Gerard T; Pierce, Graham J; Lyons, Kady; Stohs, Stephen M

doi: 10.1093/icesjms/fsaf139pmid: N/A

Marine heatwaves are periods of anomalously warm ocean temperatures that can substantially impact marine ecosystems. These events can lead to changes in trophic interactions, food webs, and ecosystem structure, even after they have subsided. In this study, we described changes in swordfish (Xiphias gladius) foraging ecology in the California Current Large Marine Ecosystem (CCLME) over a period of rapid oceanographic and ecosystem change. We used 17 years of data (2007–23) to examine how swordfish diet composition varied through time in the CCLME before, during, and after the severe marine heatwave of 2014–16. Stomachs were collected by fishery observers aboard commercial vessels using drift gillnet and deep-set buoy gear. Prey were identified to the lowest taxonomic level possible and diet composition was analysed using univariate and multivariate methods. Our results showed a shift in diets occurred from cephalopods to epipelagic teleosts in 2014–16. While jumbo squid (Dosidicus gigas) was the most important prey during the early years of the study, Pacific hake (Merluccius productus) and northern anchovy (Engraulis mordax) dominated the diets in more recent years. The diet shifted towards teleosts in 2014–16 coincided with warm sea surface temperature anomalies, stronger stratification and shallower isothermal layer depths, negative North Pacific Gyre Oscillation, and higher anchovy biomass in the study region. Overall, swordfish diets appeared to integrate prey availability, environmental forcing, and spatiotemporal patterns in the CCLME. Our results showed that swordfish are generalist and opportunistic predators that have many characteristics of useful ‘ecosystem sentinels’ such as conspicuousness, sensitivity to ecosystem processes, and timely response to ecosystem shifts. Our findings can inform ongoing ecosystem monitoring efforts in the CCLME, as well as the development of ecosystem models. We also provide a unique perspective on how marine heatwaves may impact trophic connections and marine ecosystems.

Gauthier, Charlotte; Reis-Santos, Patrick; Gillanders, Bronwyn M; Fisher, Jonathan A D; Robert, Dominique; Sirois, Pascal

doi: 10.1093/icesjms/fsaf132pmid: N/A

Partial migration is a common strategy in marine fishes, enhancing resilience through diversified movement patterns that buffer the effects of environmental changes. A key ecological outcome of migration behaviour is growth variability, which provides insights into the adaptive value of different migratory strategies. Using otolith back-calculation, we investigated how growth patterns of Atlantic halibut (Hippoglossus hippoglossus) in the Gulf St. Lawrence (Canada) varied among resident and migratory individuals whose migration histories were determined previously via otolith chemistry. Von Bertalanffy growth models fitted with nonlinear mixed-effects models revealed that migrants exhibited faster growth rates and greater theoretical maximum lengths compared to residents of both sexes, with significant differences in length-at-age emerging from the age of six. However, both contingents showed good condition, with no differences in relative condition. Overall, growth differences likely reflect the benefits of warmer temperatures and increased prey abundance or quality in shallow summer habitats for migrants, contrasted with potential increased competition in denser halibut populations in deeper channels. Overall, this observed difference in growth suggests that increased habitat quality in shallow areas can overcompensate for energy costs associated with an annual migration, which can exceed 1000 km. The complex growth dynamics between migratory and resident contingents highlight the challenges of managing species with partial migration, where specific components may disproportionately contribute to stock biomass, particularly in the context of changing environmental conditions.

Demanèche, Sébastien; Bachiller, Eneko; Adamowicz, Maciej; Mugerza, Estanis; Vasconcelos, Rita P; Kovsars, Maksims; Egekvist, Josefine; Armstrong, Mike; Bekaert, Karen; Canha, Angela; Carlshamre, Sofia; Couperus, Abraham S; Elson, Jon; Fernandes, Ana Cláudia; Gitarakos, Giorgos; Glemarec, Gildas; Orfanidis, Georgios A; Kavadas, Stefanos; Krumme, Uwe;

Chérubin, Laurent M; Woodward, Caroline; Schärer-Umpierre, Michelle; Nemeth, Richard S; Appeldoorn, Richard; Appeldoorn-Sanders, Eric; Tuohy, Evan; Ibrahim, Ali K

doi: 10.1093/icesjms/fsaf138pmid: N/A

Fish spawning aggregations (FSAs) are elevated concentrations of conspecific fish, often predictable in time and space, that gather for the main purpose of reproduction. For some grouper species, distinct courtship sounds are associated with specific reproductive behaviors, and this association has yet to be elucidated. If known, long-term trends in courtship sounds can thus be used as indicators of change in spawning aggregations. Red hind (Epinephelus guttatus) form spawning aggregations annually at recurring locations and times. Red hind have the ability to produce four distinct types of sounds (labeled RH1–4) that are most commonly heard during FSAs. Of these courtship-associated sounds (CAS), mostly two, produced by males, are used during courtship displays toward gravid females (RH1) and territorial/harem defense with other males (RH2), respectively. To elucidate the role of these two CAS in the red hind reproductive behaviors we analyzed the evolution of the partitioning between RH1 and RH2 call types in acoustic recordings spanning 12 years of spawning seasons, between 2011 and 2022 at a Caribbean FSA, off western Puerto-Rico. The relative temporal variations of call types were linked to the dynamics of the spawning population and suggests that daily to hourly variations in call numbers are linked to changes in sex ratios associated with egress and ingress from and to the spawning site, respectively. Specifically, RH2 was the most common call type during FSA. However, RH1 call type numbers peaked at the time of presumed spawning, while RH2 call type numbers decreased, confirming RH1 association with courtship display toward a female or a harem. At the interannual scale, the evolution of the relative variation of the two call types suggests either a significant change in the sex ratio tending toward a male dominated population or a spatial shift of the spawning site away from the location of the acoustic recorder. Understanding the relative role of call types and monitoring the relative variations of call type numbers in the reproductive dynamics of socially structured populations enables the understanding of potential changes in a spawning aggregation over time that could result from fishing pressure or environmental changes.

Zupa, Walter; Carbonara, Pierluigi; Bitetto, Isabella; Casini, Michele; Maiorano, Porzia; D'Onghia, Gianfranco; Isajlovic, Igor; Spedicato, Maria Teresa; Van Hoey, Gert; Rindorf, Anna

doi: 10.1093/icesjms/fsaf148pmid: N/A

Fishing activities with mobile bottom-contacting gears can heavily impact the seafloor, disrupting marine life and potentially leading to a loss of biodiversity. The impact of fishing pressure on benthic habitats depends on their natural sensitivity, the type of fishing gear, and the frequency and intensity of fishing. This study focused on assessing the health of benthic habitats in the Adriatic and Western Ionian Seas (Mediterranean Geographical Sub-Areas 17, 18, and 19), using the relative benthic status indicator, which quantifies the interaction between fishing pressure and habitat sensitivity. Results obtained provide relevant insights to help balance conservation goals with the need for sustainable fishery activities. The results revealed differences between the two studied areas. The Adriatic Sea, with its high concentration of fishing activity in muddy continental shelf habitats, showed significant degradation of the benthic state. In contrast, the Western Ionian Sea, characterized by a higher proportion of deeper waters, appeared to be in better condition due to comparatively lower fishing intensity. These findings highlight the critical need for spatially targeted management to mitigate the fishing impact. Two management scenarios were explored to support sustainable fisheries. The first scenario focused on introducing spatial closures in areas of ecological importance, reallocating banned fishing activities to less sensitive areas. The second scenario implemented a gradual reduction in fishing effort over five years, aligning with the regional management plan in force in the study area. While spatial closures resulted in localized improvements in benthic health, broader effort reductions offered more widespread benefits across the region. These findings underscore the importance of spatial planning and adaptive fishery management to protect marine habitats and their long-term productivity and diversity.

Moyes, Faye; Smout, Sophie; Thomas, Len; Kingston, Al; Northridge, Simon

doi: 10.1093/icesjms/fsaf146pmid: N/A

The accidental capture (‘bycatch’) of marine animals can pose a conservation threat to populations of endangered, threatened, and protected species. We evaluated the factors influencing or associated with estimated bycatch-per-haul (BpH) using a unique long-term data set with almost 20 000 monitored static net fishing operations collected between 1996 and 2023 as part of the UK Bycatch Monitoring Programme. We developed statistical models to explore relationships between BpH and potential explanatory variables for two small cetacean species, harbour porpoise (Phocoena phocoena) and common dolphin (Delphinus delphis), and a pinniped category [which included grey seal (Halichoerus grypus) and harbour seal (Phoca vitulina)]. Explanatory variables were spatio-temporal [ICES Division, season (day of year), year], environmental (depth), and operational [metier, effort, presence of acoustic deterrent devices (ADDs)]. Harbour porpoise and common dolphin BpH were relatively stable up to 2014, but since then have generally shown opposing trends with harbour porpoise BpH decreasing and common dolphin BpH increasing. Seal BpH has been gradually increasing across the time-period. Seasonal patterns in BpH were also evident, with harbour porpoise rates highest in spring and autumn, and common dolphin and seal rates highest in winter. Harbour porpoise and seal BpH generally decreased with increasing depth; no clear association with depth was found for common dolphin BpH. BpH exhibited an increasing trend as haul effort increased (effort being estimated per haul based on soak time and net length), and there was a tendency for bycatch rates to increase more slowly at high effort levels. The use of ADDs was associated with lower BpH of harbour porpoise (approximately a 75% reduction) but no clear effect was seen for common dolphin. BpH of seals was positively associated with use of ADDs. Model predictions for ICES Divisions, metiers and seasons with relatively higher BpH for the different species can be used to refine current bycatch estimation procedures and inform the development of targeted bycatch mitigation.

Ryan, Karina L; Lai, Eva K M; Smallwood, Claire B; Lyle, Jeremy M; Stark, Kate E; Tracey, Sean R

doi: 10.1093/icesjms/fsaf131pmid: N/A

Recreational fishing is popular worldwide and understanding variability in participation can inform policies that seek to improve sustainability of recreational fisheries and amenity for recreational fishers. However, not all recreational fishers are alike in their demographics or behaviours. This study explores temporal and spatial variability in licensed boat-based recreational fishing participation in Western Australia using data from a consistent survey design delivered 12 times from 2011 to 2024. Five fisher participation typologies were identified across four marine bioregions (North Coast, Gascoyne Coast, West Coast, and South Coast) and four fishery types (demersal, nearshore, pelagic, and invertebrate) with varied fisher characteristics (residence, age, gender, and avidity) associated with the likelihood of membership to each typology. West Coast casual fishers (32% of licensed fishers) were typically older, metropolitan residents that fished rarely or occasionally and were not associated with any fishery type, while West Coast specialist fishers (26%) were typically younger, metropolitan residents and avid fishers that were associated with nearshore, invertebrate, and demersal fisheries. The remaining groups were typically younger, regional residents that fished in South Coast nearshore (16%), North Coast demersal (14%), and Gascoyne demersal (11%) fisheries. This study contributes to global issues regarding the impact of fisher heterogeneity on recreational fisheries, particularly in the context of increasing and ageing populations, which impacts fisher representation for monitoring and management, and perceived equity in resource allocation. Improved understanding of fisher typologies can be used to address management objectives and to develop appropriate education and communication strategies.