ICES Journal of Marine Science: Journal du Conseil

Gallagher, John Barry; Shelamoff, Victor; Layton, Cayne

doi: 10.1093/icesjms/fsac011pmid: N/A

Global seaweed carbon sequestration estimates are currently taken as the fraction of the net primary production (NPP) exported to the deep ocean. However, this perspective does not account for CO2 from the consumption of external subsidies. Here, we clarify: (i) the role of export relative to seaweed net ecosystem production (NEP) for a closed system and one more likely open to subsidies; (ii) the importance of subsidies by compiling published estimates of NEP from seaweed-dominated ecosystems; and (iii) discuss their impact on the global seaweed net carbon balance and other sequestration constraints as a mitigation service. Examples of seaweed NEP (n = 18) were sparse and variable. Nevertheless, the average NEP (−4.0 mmol C m–2 d–1 SE ± 12.2) suggested that seaweed ecosystems are a C source, becoming increasingly heterotrophic as their export is consumed. Critically, mitigation of greenhouse gas emissions was mixed relative to their replacement or baseline states, and where CO2 is supplied independently of organic metabolism and atmospheric exchange, we caution a sole reliance on NEP or NPP. This will ensure a more accurate seaweed mitigation assessment, one that does exceed their capacity and is effective within a compliance and carbon trading scheme.

DeMartini, Edward E

doi: 10.1093/icesjms/fsac022pmid: N/A

What follows is a look back over a long and productive career and avocation in a field that I love, but one that has also been struck occasionally by personal tragedy, including the loss of my father at an early age, the unexpected death of my beloved wife and life partner in 2010, and a stroke in 2020 that has left me partially disabled. But impactful events can be serendipitous in prompting productive research. The lesson learned by such experiences is that opportunities—and the self-imposed responsibilities—to make positive contributions to the world, and to thereby honor the memories of those lost, continue beyond such events. The lessons I have learned along the way should inspire others at the start of and during their own personal life trajectories, particularly in developing the ability to recognize and appreciate opportunities for mentorship and to inspire emerging scholars and junior researchers to both respond to such opportunities to be mentored and subsequently to be mentors themselves. Everyone, especially students and junior scientists, in particular those who will become resource managers, should realize that they are links in a chain—an important one connecting the past and the future! My goal herein is to use my story to advise students and young scientists, and remind my older colleagues, of the importance of keeping this perspective as they go forward. I have tried to weave this message together with justification for motivation.

Zuercher, Rachel; Motzer, Nicole; Magris, Rafael A; Flannery, Wesley

doi: 10.1093/icesjms/fsac009pmid: N/A

Many coastal nations have embraced marine spatial planning (MSP) as a solution to maintaining ecological integrity of marine environments, while ensuring continued provisioning of economic, social, and cultural benefits. However, evidence supporting the idea that plans achieve—or are likely to achieve—these goals is limited. One gap in our understanding stems from questions surrounding the metrics against which MSP success is measured. Evaluation can be based on explicitly stated objectives, or might include metrics corresponding to broad social–ecological goals. This paper compares aspirational MSP goals gleaned from a literature review to the objectives extracted from 50+ finalized and implemented plans to better understand: (1) how well these two groupings align, and (2) in what ways any misalignment may shape MSP evaluation. Findings show that plans prioritize the environment, economy, and governance, while often excluding objectives related to cultural heritage, human well-being, Indigenous rights, human safety, and climate change. Social and cultural objectives have become more prevalent over time, yet overall stated objectives remain distinct from theorized MSP goals. As international efforts aim to expand MSP, narrowing the gap between how it is perceived and how its outcomes are evaluated is critical to better understanding what it is likely to achieve.

Chaput, Romain; Sochala, Pierre; Miron, Philippe; Kourafalou, Vassiliki H; Iskandarani, Mohamed

doi: 10.1093/icesjms/fsac021pmid: N/A

The impacts of seven uncertain biological parameters on simulated larval connectivity in the Florida Keys are investigated using Polynomial chaos surrogates. These parameters describe biological traits and behaviours—such as mortality, swimming abilities, and orientation—and modulate larval settlement as well as dispersal forecasts. However, these parameters are poorly constrained by observations and vary naturally between individual larvae. The present investigation characterizes these input uncertainties with probability density functions informed by previous studies of Abudefduf saxatilis. The parametric domain is sampled via ensemble calculations, then a polynomial-based surrogate is built to explicitly approximate the dependence of the model outputs on the uncertain model inputs, which enables a robust statistical analysis of uncertainties. This approach allows the computation of probabilistic dispersal kernels that are further analyzed to understand the impact of the parameter uncertainties. We find that the biological input parameters influence the connectivity differently depending on dispersal distance and release location. The global sensitivity analysis shows that the interactions between detection distance threshold, orientation ontogeny, and orientation accuracy, are the dominant contributors to the uncertainty in settlement abundance in the Florida Keys. Uncertainties in swimming speed and mortality, on the other hand, seem to contribute little to dispersal uncertainty.

Lira, Alex Souza; Le Loc'h, François; Andrade, Humber Agrelli; Lucena-Frédou, Flávia

doi: 10.1093/icesjms/fsac004pmid: N/A

Tropical fisheries tend to be multispecies and require management approaches adapted to high diversity but scarce and poorly informative data. Productivity and Susceptibility Analysis-PSA is particularly useful where catch or biological data are incomplete, aggregated across species or insufficient for quantitative stock assessment. We applied PSA to estimate vulnerability and potential risk to target and non-target species caught by the small-scale shrimp fishery in northeast Brazil, adapting the method to regional conditions and incorporating an assessment of uncertainties caused by its subjective choices. Our findings suggest that non-target species can be more vulnerable than target ones. Bagre marinus, Pseudobatos percellens, Micropogonias furnieri, Hypanus guttatus, Macrodon ancylodon, Polydactylus virginicus, Rhizoprionodon porosus, Cynoscion virescens, Larimus breviceps, and Menticirrhus americanus, were the top 10 species potentially at risk due to their low productivity (long lifespans, low spawning), high capture rates of juveniles and overlap of feeding and breeding grounds with fishing areas. Most species (76%) maintained the same risk category (low, moderate, or high) regardless of the score weighting or productivity and susceptibility attribute boundaries applied. Overall, the target species are not currently the main ones threatened, but bycatch such as elasmobranchs, catfishes and Scianidae should be prioritized for assessment and data collection.

Cocking, Jennifer; Narayanaswamy, Bhavani E; Waluda, Claire M; Williamson, Benjamin J

doi: 10.1093/icesjms/fsac006pmid: N/A

Plastic pollution in the marine environment is a pervasive, global problem that threatens wildlife and human health. Routine monitoring is required to determine pollution hotspots, focus clean-up efforts, and assess the efficacy of legislation implemented to reduce environmental contamination. The shoreline represents an accessible area, relative to open water, from which to monitor this. Unmanned aerial vehicles (UAVs) offer a low-cost platform for remote sensing that operates below cloud coverage, which can interfere with satellite imagery. Detection of plastic using visible light is limited however, and results may be improved by using short-wave infrared (SWIR) imagery to collect chemical information. Within the commercial recycling industry, plastic items are sorted successfully based on their composition using SWIR instrumentation that measures the chemical spectra of waste items under controlled illumination. Here, proof of concept is established for aerial detection of domestic and shoreline-harvested plastic items on a beach under natural sunlight with a lightweight (800 g), hyperspectral SWIR camera deployed at an altitude of ∼ 5 m over ∼ 30-m transects. The results of spectral correlation mapping to compare imagery spectra to polyethylene and polypropylene reference spectra demonstrate that these two polymers can be successfully detected with this novel method.

Haase, Kevin; Weltersbach, Marc Simon; Lewin, Wolf-Christian; Zimmermann, Christopher; Strehlow, Harry Vincent

doi: 10.1093/icesjms/fsac012pmid: N/A

Globally, marine recreational fishing is a popular activity that contributes substantially to fishing mortality for some stocks and therefore should be considered in stock assessments and fisheries management. Using the example of the German western Baltic Sea recreational cod fishery, this study examines the effects of the first-time introduction of a bag limit on a previously largely unregulated marine recreational fishery. Furthermore, the study simulates and compares effects of different bag limits, seasonal closures, minimum length, and harvest slot limits to inform scientists, stakeholders, and managers about alternative management strategies and their potential effects on the fishery. After the first-time introduction of the bag limit, recreational removals decreased more than expected and the fishing participation slightly declined. The simulations showed that management measures adapted to the fishing methods reduced recreational removals but with different effects on cod length distributions and angler welfare. A combination of a high bag limit, seasonal closure and size/slot limits were most suitable for limiting cod removals with minimal impacts on angler welfare. This study demonstrates that recreational fisheries management measures need to be evaluated considering fishing methods and angler preferences before their implementation to avoid unexpected biological, social, and economic consequences.

Omori, Kristen L; Thorson, James T

doi: 10.1093/icesjms/fsac015pmid: N/A

Data-limited species are often grouped into a species complex to simplify management. Commonalities between species that may indicate if species can be adequately managed as a complex include the following: shared habitat utilization (e.g., overlapping fine-scale spatial distribution), synchrony in abundance trends, consistent fishing pressure or gear susceptibility, or life history parameters resulting in similar productivity. Using non-target rockfish species in the Gulf of Alaska as a case study, we estimate spatial and temporal similarities among species to develop species complexes using the vector autoregressive spatio-temporal (VAST) model, which is a joint dynamic species distribution model. Species groupings are identified using Ward's hierarchical cluster analysis based on spatial and temporal species correlations. We then compare the spatial and temporal groupings with cluster analysis groupings that use exploitation and life history characteristics data. Based on the results, we conclude that there are some rockfish species that consistently group together, but the arrangement and number of clusters differ slightly depending on the data used. Developing species complexes for fisheries management requires a variety of analytical approaches including species distribution models and cluster analyses, and these can be applied across the full extent of available data sources.

Svedäng, Henrik; Savchuk, Oleg; Villnäs, Anna; Norkko, Alf; Gustafsson, Bo G; Wikström, Sofia A; Humborg, Christoph

doi: 10.1093/icesjms/fsac017pmid: N/A

Hypoxia is presently seen as the principal driver behind the decline of the former dominating Eastern Baltic cod stock (EBC; Gadus morhua). It has been proposed that both worsening conditions for reproduction and lower individual growth, condition, and survival are linked to hypoxia. Here, we elucidate the ecological envelope of EBC in terms of salinity stratification, oxygen content, and benthic animal biomasses, and how it has affected EBC productivity over time. The spawning conditions started deteriorating in the Gotland Deep in the 1950s due to oxygen depletion. In contrast, in the Bornholm Basin, hydrographic conditions have remained unchanged over the last 60 years. Indeed, the current extent of both well-oxygenated areas and the frequency of hypoxia events do not differ substantially from periods with high EBC productivity in the 1970s–1980s. Furthermore, oxygenated and therefore potentially suitable feeding areas are abundant in all parts of the Baltic Sea, and our novel analysis provides no evidence of a reduction in benthic food sources for EBC over the last 30 years. We find that while reproduction failure is intricately linked to hydrographic dynamics, a relationship between the spread of hypoxia and the decline in EBC productivity during the last decades cannot be substantiated.

Jiang, Long; Blommaert, Lander; Jansen, Henrice M; Broch, Ole Jacob; Timmermans, Klaas R; Soetaert, Karline

doi: 10.1093/icesjms/fsac023pmid: N/A

Kelp cultivation receives increasing interest for its high-value products and ecological services, especially in Europe and North America. Before industrial kelp farming in marine ecosystems continue to scale up, evaluation of the site-wide production relative to ecological carrying capacity (CC) of the identified system is essential. For this purpose, a mechanistic kelp model was developed and applied for hypothetical numerical experiments of expanding the farming area in a Dutch coastal bay (the Eastern Scheldt), where cultivation of Saccharina latissima (sugar kelp) is emerging. The kelp model was implemented within a three-dimensional hydrodynamic–biogeochemical model to account for the environmental interactions. The model captured the seasonal growth dynamics of S. latissima, as well as its carbon and nitrogen contents measured at the Eastern Scheldt pilot sites. The model results suggest that expanding the kelp farming area to ∼1–30% of the bay (representing ∼3.4–75 kt harvest dry weight in the 350-km2 bay) had the potential to weaken the spring bloom, and thereby affected the coexisting shellfish culture in the bay. Competition between S. latissima and phytoplankton mostly occurred in late spring for nutrients (dissolved inorganic nitrogen). The ecological CC should be weighed according to these negative impacts. However, the production CC was not reached even when farming ∼30% of the Eastern Scheldt, i.e. harvesting totally 75 kt dry mass, given that the simulated overall S. latissima production kept increasing with the farming activity. Our modelling approach can be applied to other systems for S. latissima cultivation and assist in assessing CC and environmental impacts.