ICES Journal of Marine Science

Brodte, Eva-Maria; Boersma, Maarten; Croot, Peter; Dummermuth, Angelika; Krug, Lilian Anne; Lemke, Peter; McGrane, Pauhla; Seeyave, Sophie; Wiltshire, Karen Helen

doi: 10.1093/icesjms/fsaf165pmid: N/A

The significance of global marine education in ocean science and management is critical, especially in regions with weak infrastructure and economies. Therefore, knowledge generation as basis to establish and maintain essential research infrastructure, expertise, and management systems is crucial. In this context, we present the Polarstern Atlantic Transect Training (PSATT) as a versatile and proven shipboard training programme. This training is suitable for medium (50-100 m length, duration of at least5 days) and large (>100 m length, duration of > 14 days) research vessels, by scaling the modular nature of the educational concept. This programme can be adjusted to cater for vessels of various sizes and cruise durations, making it a valuable blueprint for similar marine education initiatives at sea. As a result, this tested concept provides an effective and adaptable framework for training at sea; it hasbeen conducted four times on board the research vessel (RV) Polarstern in 2015, 2016, 2019 and 2022 and trained so far 97 scholars on board. In this paper, we present a straightforward yet efficient framework for training at sea, designed to be inclusive, intercultural and international, as well as transdisciplinary and operational on research vessels. This approach aims to contribute to the development of skilled professionals in the field of ocean science and management.

Takemura, Shion; Na, Hanna; Boldt, Jennifer L; Bograd, Steven J; Hasegawa, Daisuke; Hunter, Karen L; Kang, Sukyung; Katugin, Oleg N; Kim, Saeseul; Lobanov, Vyacheslav B; Lorenzo, Emanuele Di; Mazur, Mackenzie; Oyaizu, Hitomi; Qiao, Fangli; Rykaczewski, Ryan R;

Frederiksen, Morten; Layton-Matthews, Kate; Bennett, Sophie; Funder Castenschiold, Johan H; Cruz-Flores, Marta; Edney, Alice J; Fauchald, Per; Franklin, Kirsty A; Guímaro, Hugo R; Hereward, Hannah F R; Johnston, Daniel T; Merkel, Benjamin; Molværsmyr, Sindre; Sauser, Christophe; Snell, Katherine R S; Humphreys, Elizabeth M

Delaval, Aurélien; Clegg, Tom; Lynghammar, Arve; Bruvold, Ingrid M; Tranang, Caroline A; Williams, Tom

doi: 10.1093/icesjms/fsaf172pmid: N/A

Skates (Class Chondrichthyes, Order Rajiformes) are locally abundant in high latitude ecosystems that are experiencing rapid environmental change, increasing interests of primary industries, and changes in fishing activity. Effective management of these and other marine features depends on robust biological baselines from which ecological and demographic trends can be evaluated. Skates along the Norwegian continental shelf and slope, a biologically and commercially important region in the Nordic Seas, are severely underrepresented in the scientific literature compared to neighbouring seas. Despite being a regular feature of fisheries bycatch, skates are seldom identified to species in landings statistics, which impedes monitoring efforts. This has been attributed to issues of taxonomic confusion and the low commercial value of skates. Following recent taxonomic revisions within the Rajiformes and improved identification keys aboard research surveys, we evaluated the occurrence, geographic and size distributions of skates from 5005 demersal trawl hauls across the Norwegian continental shelf and slope (north of 62°N) in the period 2015–2024. The results were compared to existing literature from the surrounding seas. We confirm the occurrence of at least ten skate species in the region, half of which are threatened with extinction (IUCN Red-List). The skate fauna was dominated by the widely distributed Amblyraja radiata, A. hyperborea, Rajella fyllae, and Bathyraja spinicauda, for which all size classes were locally present. Their occurrence was modelled using generalized additive mixed models, which indicated species-specific but overlapping distributions in three-dimensional space. Six other species were occasionally caught (Rajella lintea, Dipturus oxyrinchus, D. nidarosiensis, Leucoraja circularis, Raja clavata, and Leucoraja fullonica). Rare catches of other members of the Dipturus, Leucoraja, and Raja genera could not be verified; however, D. intermedius has been confirmed from citizen science reports. The results fill an important knowledge gap concerning the skate community assemblage in the Norwegian Sea, highlighting its role as a transition zone between temperate (e.g. the North Sea) and Arctic community assemblages. The results can serve as a baseline to assess fisheries catches, habitat use, and future distribution and community shifts in this rapidly changing region.

Huang, Yansong; Girardin, Raphaël; Oliveros-Ramos, Ricardo; Travers-Trolet, Morgane; Quennevat, Antoine; Safi, Georges; Ben Rais Lasram, Frida; Halouani, Ghassen

doi: 10.1093/icesjms/fsaf153pmid: N/A

Offshore wind energy is in great expansion around the world. Considerable gaps in scientific knowledge on ecological impacts of offshore wind farms (OWFs), including the lack of standardized operational tools to conduct cumulative impact assessment, could lead to delays in the consent process. Ecosystem models are useful tools for cumulative impact assessments because they consider various ecosystem components and their interactions, and therefore are able to provide integrative evaluations. In this study, we improved an existing individual-based ecosystem model (OSMOSE), aiming to assess the cumulative effects of OWFs on various biological groups and fishing activities in the Eastern English Channel (EEC). This work presents substantial technical developments on the existing OSMOSE model application, enhancing its capability to evaluate OWF effects. Technical model improvements included new species, a better representation of the fishing process, prey field forcing updates to include climate change projections, and inter-annual calibration over the period 2002–2021. These developments were essential for improving the depiction of OWFs cumulative impacts, encompassing effects from underwater noise emission, sediment resuspension, and fishing access restriction. We simulated the EEC ecosystem during construction and operational phases under a factorial plan combining OWFs deployment and fishing regulation scenarios. At the scale of the entire EEC ecosystem, total fish biomass and catch were slightly reduced under all scenarios. The most significant biomass declines were observed for cuttlefish, herring, and red mullet, primarily driven by changes in predation and fishing pressure, especially during the construction phase. However, at the local scale (model grid resolution), these changes appear to be OWF-specific, as no consistent spatial patterns in fish biomass were observed across OWFs deployment sites. The differences among scenarios suggest a trade-off between energy production, fishery resource exploitation, and environmental protection goals. The most probable OWF spatial deployment scenario that balanced on regulatory and socio-economic considerations also represented a balance of ecological factors.

Delgado, M Lisette; Van Wyngaarden, Mallory; Einfeldt, Anthony L; McCracken, Gregory R; Paterson, Ian; Morris, Corey; Bradbury, Ian; Bentzen, Paul; Ruzzante, Daniel E

doi: 10.1093/icesjms/fsaf155pmid: N/A

The loss of genetic diversity during a population collapse may have important implications for fisheries management and conservation. However, the identification of the underlying changes to genetic diversity can be challenging. The 1990s collapse of the Atlantic cod (Gadus morhua) fishery in the northwest Atlantic, which included the largest population complex known as Northern Cod, raised questions regarding the potential biological consequences for the stock’s genetic diversity. Using low-coverage whole genome sequencing (lcWGS) on collections from the 1990s and 2010s, we detected a decline in genetic diversity of Atlantic cod in the Canadian portion of the species range. A comparison between 1990s and 2010s collections showed less variation in the 2010s, fewer distinguishable genetic clusters, and a significantly lower genetic diversity in the contemporary populations. Our results demonstrate a loss in genetic diversity at the population and individual levels following the fishery collapse and indicate that genetic diversity can be lost even in numerically large populations.

Caserta, Valentina; Punt, André E; Arneri, Enrico; Berginc, Tim; Kec, Vanja Cikes; Costantini, Ilaria; De Felice, Andrea; Donato, Fortunata; Leonori, Iole; Santojanni, Alberto; Angelini, Silvia

doi: 10.1093/icesjms/fsaf171pmid: N/A

Recent advancements in integrated single-species models allow for the inclusion of environmental drivers in stock assessment models, improving stock evaluation and better explaining fish population dynamics. This study applies Stock Synthesis (SS) to assess the European anchovy (Engraulis encrasicolus) stock in the Adriatic Sea, allowing for time-varying growth, recruitment, mortality, and survey catchability. These processes were linked to sea surface temperature (SST), river runoff, chlorophyll-a concentration, and salinity. Model selection, based on AIC and parameter significance, revealed that higher SST is significantly associated with reduced mean length-at-age. Two-variable models further revealed that SST strongly influences growth, while freshwater input modulates mortality at age one and survey catchability. Integrating these environmental factors reduced unexplained recruitment variability and improved model fit to length- and age-composition data, enhancing stock status estimates such as spawning biomass and fishing mortality. Diagnostic evaluations indicate that the integration of environmental covariates, despite inherent challenges associated with data quality, offers valuable insights into the observed declines in anchovy size and recruitment. The findings emphasize the importance of environmental conditions—particularly temperature and freshwater discharge—in driving life-history traits and population dynamics.

doi: 10.1093/icesjms/fsaf169pmid: N/A

Pioch, David; Karlsen, Ørjan; Fjelldal, Per Gunnar; Dalvin, Sussie

doi: 10.1093/icesjms/fsaf176pmid: N/A

The marine ectoparasitic copepod Lepeophtheirus salmonis, commonly known as the salmon louse, poses a significant risk to Atlantic salmon (Salmo salar L.) in farm-intensive areas in the North Atlantic. Previous studies have documented the direct effects of the lice on hatchery-reared salmon in laboratory studies and wild salmon as part of ecosystem-level modeling approaches. However, the effects of L. salmonis on wild post-smolt salmon in a controlled environment remain poorly understood. In this study, we investigated the impact of the parasite on individual fish in two separate laboratory infection studies with wild post-smolt salmon caught during smolt migration from two rivers in western Norway (n = 47, average body weight 24.3 ± 6.0 g). We found negative correlations between L. salmonis infection intensity and host-specific growth rate (β1: -1.15% d−1, p < 0.001) and condition factor (β1: -0.08, p < 0.001). We observed significant positive correlations between infection intensity and salmon heart size (β1: 4.022e-04% body weight, p = 0.002) and liver size (β1: 0.03% body weight, p < 0.001), suggesting a trend toward increased organ size. However, the poor model fit and minimal β1 estimates limit the ability to draw conclusions about wild host fitness. Mortality (n = 11) was observed between 18 and 35 days post-infection at 9°C water temperature. This time frame coincided with the female preadult lice stages. Obtained lice-induced mortality estimates were determined in the absence of additional natural environmental stressors such as predators, which are likely to preferentially target fish weakened by infection. Notably also, the use of UV-treated water excluded opportunistic pathogens that may infect fish through lice-associated wounds. This study confirms the established link between reduced condition and higher mortality due to L. salmonis as observed in laboratory experiments using hatchery-reared fish also extends to wild post-smolt salmon entering the fjords, underscoring the considerable risk the parasite poses to these populations.

Hagen, Ingerid J; Skaala, Øystein; Quintela, María; Dahle, Geir; Fiske, Peder; Foldvik, Anders; Glover, Kevin A; Hindar, Kjetil; Knutsen, Halvor; Lo, Håvard; Sodeland, Marte; Sægrov, Harald; Karlsson, Sten

doi: 10.1093/icesjms/fsaf151pmid: N/A

Sea trout is the anadromous form of brown trout (Salmo trutta) and is culturally, economically, and ecologically important across its native distribution. Here, we describe the genetic structure of sea trout caught in 105 rivers from the 2600 km long Norwegian coast using >3000 individuals genotyped for 93 SNPs. Our results indicated that most of the study populations are genetically different from each other with a mean pairwise FST of 0.067. While most genetic variation was found within the different populations (93.2%), around 4.5% variation was found between rivers within the different fjord systems and neighbor joining analysis generally grouped together populations from the same fjord or geographic region. Isolation by distance (IBD) for the 105 populations was significant (r2 = 0.21), but the same analysis on three smaller spatial scales revealed different patterns: significant IBD in the Hardangerfjord, moderate IBD in the Sognefjord, and no IBD for the 28 most northern populations, altogether suggesting that there is not a simple relationship between geographic distance and genetic isolation. This documentation of sea trout intra-specific biodiversity must be considered in conservation of the intra-specific diversity of sea trout, including prioritizing habitat restoration, stocks included in genebank, and protection from negative impacts from aquaculture.