NOAA National Marine Fisheries Service Alaska Fisheries Science Center

Abstract Stock assessment methods vary among regions, reflecting local conditions, fishery management systems, available data, and historical developments. Contributions from the scientific community of the International Council for the Exploration of the Sea (ICES) had global impact on the advancement of stock assessment methods and applications. In the early to mid-1900s, single species demographic models were applied to industrial fisheries throughout the northern hemisphere. In this period, ICES played a central role by contributing foundational concepts and developing conventional methods for stock assessment. In the late 1900s, trends in assessment methods diverged among regions because of differences in fisheries, available data, exploitation histories, management systems, cultural factors, and previously applied methods in each region. Monitoring programs were established for many commercial fisheries in the North Atlantic by the mid-1900s, including collection of fishery statistics, port samples of size and age composition, and fishery-independent surveys, which supported development and application of virtual population analysis (VPA) with yield-per-recruit reference points. In contrast to early deterministic models, integrated statistical models were developed in the 1980s for fisheries in the Pacific and southern hemisphere, many of which had insufficient data to support VPA approaches. The general differences in assessment methods between the North Atlantic and other regions persisted for decades, despite the exchange of ideas and people. In the 21st century, with broader inter-regional collaborations and the evolution of management systems, integrated statistical models were more commonly adopted as best practice for stock assessment throughout the world, primarily for their statistical advantages and flexibility to represent a wide range of fisheries and the available data. The history of stock assessment offers lessons for promoting the communication of advancements and application of appropriate methods for meeting the needs of fishery management.

Abstract The Bering Sea is a highly productive subarctic ecosystem with some of the most valuable commercial fisheries in the United States. This seasonally ice‐covered sea has been rapidly changing due to ocean warming with impacts to the ecosystem structure and fisheries. The long‐term effects of these shifts on primary producers, however, are still unknown. Continuous monitoring of primary productivity in the Bering Sea is critical, yet observations that capture the ephemeral nature of plankton are challenging to sustain. To address this gap, high temporal resolution primary productivity rates were quantified at a mooring site (M2) in the southeastern Bering Sea in 2021. From a suite of sensors at M2 (fluorescence, dissolved oxygen, temperature, and total dissolved gas pressure), we calculated gross primary productivity (GPP), net primary productivity (NPP), and net community productivity (NCP), the latter based on net biological oxygen saturation using dissolved oxygen/nitrogen (O 2 /N 2 ) ratios. These estimates elucidate weekly patterns from the spring bloom through fall, when the water column becomes well‐mixed. In 2021, we observed average productivity during the spring bloom, yet wind patterns and mixing dynamics during the spring contributed to low productivity during summer and fall. The 2021 productivity metrics (GPP, NPP, and NCP) were compared across the growing season and contrasted with seasonal productivity estimates at M2 in previous years with consideration given to variability of ice conditions (warm/cold years) and wind stress.

Abstract Using of calcium carbonate (CaCO 3 ) structures as an ecological tool relies on the assumption that, for some elements, their composition is influenced by the water in which an organism lives. However biological processes including, growth rates, diet, ontogeny, reproductive state, or genetics can also influence their composition. It is essential we understand how intrinsic biological factors, external environmental conditions, and interactions impact the composition of CaCO 3 structures to make ecological inferences. We examined how temperature, pH, growth, and body size influenced elemental composition of staghorn sculpin ( Leptocottus armatus ) otoliths. We held animals (108–183 mm length) under three pH (7.60, 7.75, and 7.96) and two temperature (11.5°C and 14.0°C) treatments and examined relationships of three trace element:calcium ratios (Sr:Ca, Ba:Ca, B:Ca) to experimental conditions and body size. Sr:Ca ratios showed a temperature × size interaction, with smaller fish at 11.5°C having higher values than those at 14.0°C, while differences between temperatures diminished at larger sizes. Ba:Ca ratios were lower at 14.0°C across sizes, indicating consistent temperature effects. B:Ca ratios showed weak but statistically significant negative relationships with size. No consistent effects of pH or growth rate were observed. Results highlight that trace element:calcium ratios vary in sensitivity to intrinsic and extrinsic factors, with Sr:Ca influenced by both temperature and body size, Ba:Ca reflecting moderate environmental effects, and B:Ca responding primarily to biological variation. Findings reinforce the value of otolith chemistry as an ecological tool, while emphasising the importance of considering individual-level variation when interpreting elemental signatures.

Climate-driven changes in the Subarctic will directly impact capelin populations and the ecosystem they inhabit, including their predators, prey, and physical habitats. Consequently, incorporating ecosystem considerations in future capelin fisheries management is crucial. In this study, a multidisciplinary group of experts critically evaluated whether the current capelin stock assessment and management frameworks for the four main capelin stocks in the Barents Sea (BS), Iceland-East Greenland-Jan Mayen (IEGJM), Newfoundland and Labrador shelf (NL) and Alaska (AK) align with the principles of an Ecosystem Approach to Fisheries Management (EAFM). An evidence-based ranking of our knowledge on current capelin dynamics across ecological, economic, and social dimensions was conducted, using expert knowledge supported by literature. This exercise also identified data currently used for assessment and management, which highlighted that the existing capelin assessment frameworks include varying degrees of EAFM elements across stocks, such as considerations of trophic interactions, bottom-up processes, accounting for ecosystem uncertainty, and stakeholder engagement in the advisory process. Nonetheless, there is room for improvement where data and knowledge are lacking. We provide some key tactical (short-term) and strategic (long-term) recommendations from our perspective on what is required to ensure the sustainable management of capelin in the circumpolar region over the coming decades.

ABSTRACT Sea otters ( Enhydra lutris ) exhibit morphological and physiological adaptations supporting a mass‐specific resting metabolic rate (RMR) 2.9‐fold higher than predicted for terrestrial mammals of similar size. Their elevated metabolism results primarily from thermogenic mitochondrial proton leak to compensate for heat loss in the marine environment because of their high surface‐area‐to‐volume ratio, combined with their reliance on fur insulation rather than blubber. Key respiratory adaptations include an enlarged lung volume, 3.5‐fold greater than predicted allometrically, and a proportionately elevated tidal volume, enabling efficient oxygen uptake and carbon dioxide elimination. Complementary cardiovascular adaptations include a heart mass 1.3‐fold greater than the allometric prediction, a correspondingly elevated stroke volume, normal heart rate, increased hemoglobin concentration, and enhanced arterial oxygen content. Together, these adaptations result in an elevated cardiac output and enhanced convective oxygen transport to support the elevated RMR. These multi‐level adaptations, present even in young animals, likely evolved under selective pressures favoring thermogenesis over increased insulation by blubber, representing a convergent evolutionary strategy consistent with the principle of symmorphosis, similar to terrestrial athletic mammals adapted for sustained aerobic performance rather than energy conservation. Additional benefits of enlarged lungs, such as enhanced buoyancy and pulmonary oxygen stores, may also have contributed to their evolution.

Context Fish daily age information provides insight into growth, phenology and recruitment but is rarely incorporated into the decision-making process for management because of labor-intensive data collection. Aims We tested Fourier transform–near-infrared (FT-NIR) spectroscopy as a rapid method (~1.0 v. ~60 min per otolith for microscopic methods) to determine daily age of walleye pollock (pollock; Gadus chalcogrammus), which supports an important fishery. Methods We reared two annual cohorts of pollock over 3 years to accrue a comprehensive dataset for calibration models. Key results FT-NIR spectroscopy provided an improvement over predicting daily age from otolith weight, fish weight or fish length. A calibration model developed using microscopically aged fish had a root mean square error (RMSE) from cross validation (CV) of 12.2 days. Models developed from the full dataset with ages assigned from cohort hatch dates had a test dataset RMSE of 35.4–40.7 days and a CV RMSE of 29.4–36.9 days. Conclusions Spectra were affected by size-at-age, which could affect model efficacy because growth and size are influenced by environmental variability. This can be addressed with robust calibration datasets, model testing and model updating. Implications FT-NIR spectroscopy age prediction is likely to be sufficient to capture population-scale shifts in hatch dates of pollock.