ICES Journal of Marine Science: Journal du Conseil

Bryndum-Buchholz, Andrea

doi: 10.1093/icesjms/fsac180pmid: N/A

Human-caused climate change is real. A message the scientific community has documented and disseminated for decades. Yet, after equally long inaction by global leadership to address climate change, the world is facing a climate emergency with unprecedented consequences for all aspects of life. As an early career researcher from a generation whose future seems quite dire, I ask myself repeatedly, how can I continue my research without losing hope that science matters, that my research matters? In this Rising tides article, I aim to illustrate my own experience and perspective of keeping up hope to continue doing purposeful research on the background of the ubiquitous social and political challenges we are facing under ongoing climate change. All with the conviction that individual and collective hope needs to be amplified to achieve the climate action, needed for a liveable future.

Smoliński, Szymon; Ottmann, Daniel; Outinen, Okko; Schadeberg, Amanda; Melli, Valentina; Funk, Lara; Denechaud, Côme; Wieczorek, Alina; Orio, Alessandro; Mussgnug, Robert; Morkūnė, Rasa; Vereide, Emilie Hernes; Zdulska, Maja; Phillips, Genevieve; Lishchenko, Fedor;

Townhill, B L; Artioli, Y; Pinnegar, J K; Birchenough, S N R

doi: 10.1093/icesjms/fsac177pmid: N/A

Ocean acidification has become one of the most intensively studied climate change topics and it is expected to have both direct and indirect impacts on species, ecosystems, and economies. Experiments have been performed on different taxa, life stages, and at different pH levels. Despite this wealth of information, several key challenges remain, including (1) uncertainty about how to incorporate current pH ranges and variability experienced by organisms into experiments, and (2) how to bring this information together to support analysis and assessments at the broader ecosystem level. Sophisticated modelling tools are needed to ‘scale-up’ from experimental results to regional-scale insights. This paper highlights the challenges of combining information to determine how commercially exploited species may be affected under future pH levels, and how modelling and experimental results might be better aligned, using northwest Europe and the waters around the British Isles as an example. We argue that in most cases the current evidence does not offer sufficient information into impacts at projected pH levels, and that future experiments should be designed to consider the pH levels actually experienced by organisms, as well as variability in pH. These types of study are key in safeguarding commercially exploited shellfish stocks.

Trathan, P N; Fielding, S; Warwick-Evans, V; Freer, J; Perry, F

doi: 10.1093/icesjms/fsac168pmid: N/A

We used 22 years of seasonally and spatially consistent monitoring data to explore marine predator–prey numerical response relationships. Specifically, we tested whether indices of offspring performance (e.g. offspring mass near the time of their independence and/or growth rate) from three Antarctic krill-dependent predators, showed positive relationships with estimates of krill density, determined using fishery-independent acoustic surveys undertaken towards the middle of the predator breeding season. Results showed that indices of predator reproductive performance had little relationship with krill density. In most years, average krill densities were higher on-shelf than off-shelf, potentially providing ecological buffering for predators provisioning offspring. Interestingly, positive response relationships were evident between predator offspring mass and the spatial distribution of krill, measured using indices that represent levels of inequality (patchiness) in krill distribution. These relationships were strongest using indices that reflected the off-shelf krill spatial distribution. We found that krill density and predator offspring mass were also both negatively influenced by sea surface temperature and the Southern Annular Mode, indicating that the environment exerts strong control over ecosystem processes. Finally, we consider the relevance of our results to the ecological framework used by managers responsible for setting catch limits for the regional fishery for krill.

Dahle, Geir; Sainte-Marie, Bernard; Mincks, Sarah L; Farestveit, Eva; Jørstad, Knut E; Hjelset, Ann Merete; Agnalt, Ann-Lisbeth

doi: 10.1093/icesjms/fsac172pmid: N/A

After the initial opening of the Bering Strait  5.5–-5.0 My ago, there occurred several periods with exchange of marine species between the Pacific and Atlantic Oceans. The snow crab ( Chionoecetes opilio) was first reported in the Barents Sea (BAR) in 1996, presumably following introduction via Ballast water. Since then, the population has increased in size and distribution and has become self-reproducing and of economic importance. We implemented genetic analysis to identify the origin and pathway of introduction of BAR snow crab. Samples from BAR, Alaska, eastern Canada, and west Greenland were genotyped with 12 microsatellite loci. Pairwise FST between 15 samples showed three geographic clusters, each significantly different from one another. Unexpectedly, the largest genetic distance was between the BAR and Greenland clusters. This clustering may be the result of dispersals through Bering Strait from the North Pacific Ocean and passage through the Arctic Ocean. The BAR samples did not show signs of a bottleneck in population size, as would be expected after introduction of small numbers of individuals. Presence of snow crab in the BAR may thus be the result of recent natural range expansion from around Alaska.

Brinkhof, Jesse; Sistiaga, Manu; Herrmann, Bent; Grimaldo, Eduardo; Larsen, Roger B

doi: 10.1093/icesjms/fsac174pmid: N/A

Two decades of use of the compulsory selectivity gear configuration in the Northeast Atlantic bottom trawl fishery, which consists of a rigid sorting grid followed by a diamond mesh codend, have revealed problems with performance and efficiency. Size selectivity gear alternatives to this configuration are being pursued, and recent studies of codends with shortened lastridges have reported promising results. In this study, we compared the size selectivity and catch efficiency for cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) caught using a sorting grid with 55 mm bar spacing followed by a 130 mm knotted diamond mesh codend (i.e. the compulsory gear) that same configuration but considering only the catch in the 130 mm diamond mesh codend (regular codend), and an alternative knotless codend with shortened lastridge ropes and a thinner twine. We also addressed the question of whether size-selective gear is even needed to avoid exceeding the bycatch limits of the fishery. Our results demonstrated that the alternative codend improved size selectivity by reducing the loss of fish above minimum legal size (MLS), with a minor increase in the retention of fish below MLS, compared to the compulsory combined grid and codend configuration. The regular codend also reduced the loss of fish above MLS, but the retention of haddock below MLS approached the legal limit of 15% by number. Our results also showed that the abundance of cod below MLS in the fishing area during the trials was low. They also suggested that spatial and seasonal closures in combination with a flexible choice of selection device and modern monitoring tools could be an alternative to rigid enforcement of the use of selective fishing gear.

Lindstedt, Daniel G; Langlois, Tim; Prince, Jane; de Lestang, Simon

doi: 10.1093/icesjms/fsac175pmid: N/A

It is unknown whether lobster behaviour is sensitive to fishing, as has been previously suggested for fish. This study investigated the impacts of recreational fishing on the wariness of western rock lobster (Panulirus cygnus, George) through comparisons between fished sites and no-take reserves (NTRs) at Rottnest Island. We used visual census to survey the density and size structure of lobster at sites inside and outside three comparable NTRs, and baited remote underwater video to study the behaviour of lobster at comparable sites. The density of legal-sized P. cygnus was twice as high within NTRs (0.34 ± 0.05) than fished sites (0.16 ± 0.03). P. cygnus also spent less time with bait in fished sites (0.42 ± 0.15 min) than NTRs (1.15 ± 0.28 min). This study provides the first evidence that behaviour of decapods, namely P. cygnus, is sensitive to noninjury-related disturbance associated with recreational fishing, with higher wariness in fished areas. Investigation is required into potentially confounding biotic and abiotic factors to further explore the applicability of lobster wariness as an indicator for fishing pressure.

Ward, Eric J; Barnett, Lewis A K; Anderson, Sean C; Commander, Christian J C; Essington, Timothy E

doi: 10.1093/icesjms/fsac179pmid: N/A

Ecologists and fisheries scientists are faced with forecasting the ecological responses of non-stationary processes resulting from climate change and other drivers. While much is known about temporal change, and resulting responses vis-à-vis species distributional shifts, less is known about how spatial variability in population structure changes through time in response to temporal trends in drivers. A population experiencing decreasing spatial variability would be expected to be more evenly spatially distributed over time, and an increasing trend would correspond to greater extremes or patchiness. We implement a new approach for modelling this spatiotemporal variability in the R package sdmTMB. As a real-world application, we focus on a long-term groundfish monitoring dataset, from the west coast of the USA. Focusing on the 36 species with the highest population densities, we compare our model with dynamic spatiotemporal variance to a model with constant spatiotemporal variance. Of the 36 species examined, 13 had evidence to support increasing patchiness, including darkblotched rockfish, lingcod, and petrale sole. Species appearing to be more uniformly spatially distributed over time included: Dover sole, Pacific ocean perch, and Dungeness crab. Letting spatiotemporal variation change through time generally results in small differences in population trend estimates, but larger estimated differences in precision.

Johannesen, Edda; Keith, Dave; Fogarty, Michael J; Shackell, Nancy; Frank, Kenneth T

doi: 10.1093/icesjms/fsac181pmid: N/A

Knowledge of recruitment and its variability in marine fish populations contributes to sustainable fisheries but a full understanding remains elusive. An earlier study showed that haddock (Melanogrammus aeglefinus) stocks exhibited consistently higher variability and lower reproductive rates compared to cod (Gadus morhua) stocks in the geographic regions where they co-occurred. Thus, cod may have a higher resilience to overexploitation, whereas haddock stocks may be more likely to be rescued by chance strong recruitments events. Since that initial study, the ecosystems and stocks have experienced large structural and functional changes, as well as changes in management practice and ocean warming. Here, we updated the previous earlier analysis with new data and found that despite large changes in the ecosystems explored, the patterns of recruitment variability have persisted. Recruitment variability remains higher in haddock than in cod, and the maximum annual reproduction rate at low spawning stock biomass (SSB) remains higher in cod than in haddock, although the latter difference is now less pronounced. Despite the economic and ecological importance of cod and haddock, and their long history of scientific scrutiny, the persistent difference in their reproductive biology remains unexplained.

O'Sullivan, Ronan James; Ozerov, Mikhail; Bolstad, Geir H; Gilbey, John; Jacobsen, Jan Arge; Erkinaro, Jaakko; Rikardsen, Audun H; Hindar, Kjetil; Aykanat, Tutku

doi: 10.1093/icesjms/fsac182pmid: N/A

While it is known that the oceans around the Faroe Islands support an Atlantic salmon (Salmo salar) feeding ground, the relative use of this resource by different age classes and populations remains largely unexplored. Using genetic stock identification and run–reconstruction modelling, we observed a consistent pattern whereby the proportion of multi-sea winter salmon (MSW—fish that have spent multiple winters at sea) for a reporting group was substantially greater around the Faroes than the MSW proportion among that group’s corresponding pre-fisheries abundance. Surprisingly, MSW fish from Ireland and the United Kingdom were as likely to occur around the Faroes as were MSW fish from more north-eastern regions. While 1SW salmon (single sea-winter fish) from Ireland and the United Kingdom as well as Southern Norway occurred in similar proportions around the Faroes, 1SW fish from the north-eastern regions were virtually absent. Our results indicate that the oceans around the Faroes host a predominantly MSW feeding ground and use of this resource varies across age classes and reporting groups. Furthermore, these results suggest that MSW fish from some reporting groups preferentially migrate to the Faroes. Variation in spatial resource use may help buffer salmon populations against localized negative changes in marine conditions via portfolio effects.