ICES Journal of Marine Science: Journal du Conseil

Davoren, Gail K

doi: 10.1093/icesjms/fsae021pmid: N/A

Forage fish species provide essential linkages for energy transfer within pelagic marine food webs. Capelin (Mallotus villosus), the focal forage fish in coastal Newfoundland, Canada, suffered a stock collapse in 1991 and has not recovered. Despite this collapse, capelin continue to provide locally abundant prey aggregations. Here, I synthesize the lessons learned from a long-term capelin-predator research program (2004–2022) on the northeast Newfoundland coast during the postcollapse period. I highlight the importance of simultaneously estimating forage fish biomass and predator responses in a multispecies and multiyear context. High interannual variation in capelin spawning timing and biomass was observed. Lower capelin biomass consistently resulted in predator species- and assemblage-level dietary shifts toward a higher diversity of lower trophic level, alternative prey. Energetic foraging costs of seabirds also increased under lower capelin biomass, but responses differed among species. Summer capelin consumption by dominant seabirds (9389 tonnes) and whales (778 tonnes) indicated predator energetic requirements and revealed higher natural mortality relative to fishery-based (1289 tonnes) mortality. Overall, this case study illustrated that, despite high observed behavioural plasticity, varying species-specific predator responses to changing capelin biomass integrated to increase potential competitive interactions under low capelin biomass, providing a basis for ecosystem-level change.

Hessen, Dag O

doi: 10.1093/icesjms/fsae027pmid: N/A

Any scientific career is a mix of planning and stochastic events, often with a fair share of the latter. I illustrate this by the evolution of my own career. Ecosystem studies of food webs under the impact of eutrophication (Master), and carbon cycling in DOC (Dissolved Organic Carbon)-rich lakes (PhD) led me to elemental ratios in organisms and the establishment of ecological stoichiometry. The role of phosphorus (P) in cellular processes again led to research on the evolution and regulation of genome size. As climate came higher on the agenda, it was time to apply the basic research on the C-cycle and climate in a wider context. As natural scientists, we should also engage in even wider contexts, and I have enjoyed discussions and co-operation with philosophers, psychologist, and social scientists. This helps seeing our own work in context. We should also reflect on why we do science. I have always felt that science should also add purpose to life by giving something back to society, and I have devoted much time to outreach, public talks, debates, and writing popular science books. It takes some time, but it is also rewarding and important—perhaps even more so than yet another paper.

Fiorentino, Fabio; Garofalo, Germana; Bono, Gioacchino; Vitale, Sergio

doi: 10.1093/icesjms/fsae031pmid: N/A

As deep-water red shrimp (DWRS) trawl fisheries gain importance in the Mediterranean, their impact on fragile deep-sea ecosystems requires careful management. We reviewed the historical development of DWRS fisheries in the Mediterranean to propose a harvest strategy that would enhance fishery sustainability, while preserving habitat and community integrity. We considered two representative typologies of DWRS fisheries: a domestic fleet operating within the Italian territorial waters of the Ligurian Sea, and a distant fleet operating mostly in international waters of the central-eastern Mediterranean and sharing shrimp stocks with non-European countries. Our proposed management approach is based on three main harvesting measures: (i) preventing the uncontrolled growth in number of trawlers, (ii) adopting a catch control regime, and (iii) identifying a network of deep-water areas designated alternately for fishing and conservation purposes. As with fisheries in other regions, new fishing grounds should be explored using “encounter protocols” to avoid areas hosting species indicators of Vulnerable Marine Ecosystems. Additionally, empirical indicators such as catch rate thresholds derived from fishers’ experience, could be used to move from one fishing ground to another to avoid local depletion of DWRS abundance and a decrease in fishery profitability.

Cooke, Steven J; Arlinghaus, Robert

doi: 10.1093/icesjms/fsae026pmid: N/A

Fisheries science and practice are challenging and require learning, thinking, and sharing across boundaries. The idea of boundary crossing can be described as some form of multiple disciplinarity (e.g. interdisciplinarity, transdisciplinarity), yet that inherently implies that the boundaries crossed are purely disciplinary in nature. After working across various other boundaries (i.e. realms, regions, disciplines, sectors, domains, and knowledge systems) for most of our educational journeys and professional careers, we reflect on our lived experiences with a focus on identifying the benefits and challenges of engaging in different types of boundary crossing. We submit that our personal and professional lives have been enriched by stepping outside of our immediate comfort zones and expertise (i.e. fish ecology) and engaging in active listening and learning with colleagues in other disciplines (i.e. various social sciences) and with stakeholders and policymakers. We have learned much from working across boundaries and encourage others, especially early career professionals, to do the same. What may superficially appear to be a bridge too far may in fact provide novel ways of thinking about a given issue or topic that generates actionable science for sustainable fisheries management and conservation. Many of the projects that we consider to be our greatest successes represent ones that involved boundary crossing, examples of which we provide in this essay. There is a need to prepare the next generation of problem solvers for engaging in boundary crossing and celebrating examples of where such efforts have led to meaningful advances in fisheries science and practice. Ensuring that institutional and cultural barriers that may constrain boundary crossing are addressed while also supporting those doing such work will be key to address the many fisheries and aquatic science challenges of today and tomorrow in both marine and freshwater systems.

Schiavon, Luca; Ceballos, Santiago G; Matschiner, Michael; Trucchi, Emiliano; La Mesa, Mario; Riginella, Emilio; Lucassen, Magnus; Mark, Felix C; Bilyk, Kevin; Franch, Rafaella; Wallberg, Andreas; Boscari, Elisa; Zane, Lorenzo; Papetti, Chiara

doi: 10.1093/icesjms/fsae019pmid: N/A

Cayetano, Arjay; Stransky, Christoph; Birk, Andreas; Brey, Thomas

doi: 10.1093/icesjms/fsae020pmid: N/A

Determination of individual age is one essential step in the accurate assessment of fish stocks. In non-tropical environments, the manual count of ring-like growth patterns in fish otoliths (ear stones) is the standard method. It relies on visual means and individual judgment and thus is subject to bias and interpretation errors. The use of automated pattern recognition based on machine learning may help to overcome this problem. Here, we employ two deep learning methods based on Convolutional Neural Networks (CNNs). The first approach utilizes the Mask R-CNN algorithm to perform object detection on the major otolith reading axes. The second approach employs the U-Net architecture to perform semantic segmentation on the otolith image in order to segregate the regions of interest. For both methods, we applied a simple postprocessing to count the rings on the output masks returned, which corresponds to the age prediction. Multiple benchmark tests indicate the promising performance of our implemented approaches, comparable to recently published methods based on classical image processing and traditional CNN implementation. Furthermore, our algorithms showed higher robustness compared to the existing methods, while also having the capacity to extrapolate missing age groups and to adapt to a new domain or data source.

Rand, Peter S; Ruggerone, Gregory T

doi: 10.1093/icesjms/fsae022pmid: N/A

In response to ocean heating and hatchery production, pink salmon (Oncorhynchus gorbuscha) returning from the North Pacific Ocean steadily increased after 1975, leading to concerns about their influence on food webs and competition with other species. Using measurements of distance between scale annuli of 24 584 individual sockeye salmon (O. nerka), we examined growth during their 2 or 3 years at sea from 1977 to 2015 for eight populations in Alaska. We found significant, negative autocorrelations at 1 lag year in annual growth of sockeye salmon, with a consistent pattern of lower growth in odd years, i.e. opposite to the biennial pattern of pink salmon abundance. Peak pink salmon abundances reduced growth of sockeye salmon from 7 to 14% during the second year in the ocean compared with growth when pink salmon abundance was low, while third-year growth was reduced up to 17%. The overall effect of pink salmon abundance on sockeye growth was over two times greater than the effect of sockeye salmon abundance. Production hatcheries and ocean heating contribute to the competitive dominance of pink salmon, underscoring the need to consider this unintended anthropogenic effect on the growth and productivity of sockeye salmon throughout the North Pacific.

Abookire, Alisa A; Copeman, Louise A; Litzow, Michael A; Laurel, Benjamin J

doi: 10.1093/icesjms/fsae023pmid: N/A

Warming temperatures in the Gulf of Alaska have been linked to recruitment failure in Pacific cod (Gadus macrocephalus), but the mechanisms and timing of mortality events for juveniles are unclear. To date, limited research has focused on overwintering success, and the knowledge of juvenile ecology and physiology is based entirely on summer observations. Here, we investigate the changes in body condition, diet composition, and tissue-specific fatty acid (FA) storage for age-0 Pacific cod in Kodiak, Alaska, from February to December during 2018 and 2020. We observed protracted nearshore residency from June to December. Cod body condition (Kdry) and predicted weight at length were lowest in October, November, and December. Although not different interannually, diet composition varied seasonally, which corresponded to an increase in cod length. A range of condition metrics (HSIwet, FA concentration in liver tissue, and the % of whole body FAs stored in the liver) began to increase in September. Cod prioritized growth during the summer, while in the autumn and pre-winter they allocated more energy into lipid storage. We conclude that seasonal changes in tissue-specific FA storage and pre-winter fish conditions are important factors to consider for understanding overwintering potential of juvenile Pacific cod.

Duplisea, Daniel E; Roux, Marie-Julie; Plourde, Stéphane; Galbraith, Peter S; Blais, Marjolaine; Benoît, Hugues P; Sainte-Marie, Bernard; Lavoie, Diane; Bourdages, Hugo

doi: 10.1093/icesjms/fsae024pmid: N/A

Open data that can be easily incorporated into analyses are essential for developing ecosystem approaches to marine ecological management: a common goal in fisheries policy in many countries. Although it is not always clear what constitutes an ecosystem approach, it always involves scientists working with a large variety of data and information, including data from physical and oceanographic sampling, multispecies surveys, and other sources describing human pressures. This can be problematic for analysts because these data, even when available, are often held in disparate datasets that do not necessarily correspond at appropriate temporal and spatial scales. Data can often only be obtained by specific requests to individuals in governmental agencies who are delivering on an increasing number of data requests as interest grows in practical ecosystem approach implementation. This data access model is not sustainable and hinders the momentum for ecosystem approach development. We describe a data bundling R package that makes data and climate projections available at appropriate scales to facilitate development of an ecosystem approach for the Gulf of St. Lawrence, Canada. This approach integrates closely with the present workflow of most government analysts, academics in fisheries, and scientists in private industry. The approach conforms with open data initiatives and makes data easily available globally while relieving some of the burden of data provision that can fall to some individuals in government laboratories. The structure and approach are generic, adaptable, and transferable to other regions and jurisdictions.

Skjærven, Kaja H; Alix, Maud; Kleppe, Lene; Fernandes, Jorge M O; Whatmore, Paul; Nedoluzhko, Artem; Andersson, Eva; Kjesbu, Olav Sigurd

doi: 10.1093/icesjms/fsae025pmid: N/A

Although early embryonic protein production relies exclusively on maternal molecules such as messenger RNAs (mRNAs) incorporated into ovarian follicles, knowledge about any thermally induced, intergenerational effects is scarce in ectotherms. Here, we investigated how elevated temperatures (9°–12°C vs. 6°C) during oogenesis influenced the next generation by targeting maternal mRNAs in Atlantic cod (Gadus morhua) embryos, in view of up- and down-regulated genes in ovarian follicles of pre-spawning adults. Overall, the spawning female liver showed significantly higher levels of free amino acids and N-metabolites at 9°C than at 6°C. Higher-than-optimal temperatures induced adjustments in embryo transcriptome proportional to the temperature increase relative to the control group. The adjustments included alterations in maternal-effect genes, which are developmentally conserved among vertebrates. The transcriptomic differences for a selection of genes in embryos were reflected in ovarian follicles (containing multiple cell types) several months ahead of the spawning season, implying that environmental conditions of the adults are key for adjusting the genetic instructions for offspring development. This programming of fundamental traits from mother to offspring appears part of a sophisticated process to adapt the offspring to a changing ocean, though within life stage-specific, physiological thermal tolerance windows.