Search

BACKGROUND: As a result of climate change (reduced the oxygen content and food available in the waters) and overfishing, ever larger batches of the herring catch are classified as low‐value fish and used for feedstuff or canned food production. Fast and complete ripening of marinated fillets, especially from low‐value Baltic herring, poses a problem because of the low muscle protease activity and changes in muscle tissue proteins. RESULTS: For the first time, a crude digestive proteases preparation (CDPP) was obtained from herring viscera using a two‐stage method consisting of ethanol extraction and then salt precipitation. CDPP had a reduced hemoglobin content, with optimum activity at pH 7.5–8.8 or 60–120 g kg−1 NaCl. At pH 4–5, it still exhibited 24–68% of proteolytic activity. CDPP was used for 4–24 h of brining of fresh and frozen–thawed fillets or injection of fresh fillets before marinating. CDPP‐brining increased especially cathepsin D and carboxypeptidase A activities, whereas it decreased cathepsin B and L activities in the marinades. CDPP‐brining mitigated the negative effect of freezing–thawing on mass‐yield, protease activity, protein hydrolysis, texture profile, colour and sensory quality of the marinated fillets. CDPP‐injection was found to be the best method because it increased mass‐yield and ripeness of the marinated fillets to a greater extent than CDPP‐brining did. The marinades from the CDPP‐treated fillets had no bitter taste as a result of the presence of hemoglobin or chymotrypsin, and there were no results indicating lipid oxidation. CONCLUSION: The application of CDPP in marinating technology is a viable approach to enable the use of low‐value herring in food production, shorten the marinating time, and improve the ripeness and sensory quality of meat. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Pacific pink salmon (Oncorhynchus gorbuscha) were deliberately introduced to rivers surrounding the White Sea and has spread to Norway and several other countries surrounding the North Atlantic Ocean. In August 2021, a female pink salmon displaying pale gills and abnormal behaviour was captured in River Lakselva in Northern Norway and later submitted to the Norwegian Veterinary Institute (NVI) for post‐mortem examination. Histological examination of organ samples revealed structures indicative of systemic ichthyophoniasis, caused by Ichthyophonus sp. The parasites appeared to be especially abundant in the heart and skeletal musculature, and local tissue responses were assessed to be absent or very mild. Sequences of the ribosomal 18S rRNA and the mitochondrial cytochrome oxidase 1 (CO1) genes confirmed the diagnosis and identified the pathogen as Ichthyophonus sp. The CO1 sequence further established that the isolate from pink salmon was most similar to sequences of Ichthyophonus sp. from Atlantic salmon, Salmo salar, from the Atlantic Ocean on the east coast of the US and from Atlantic herring, Clupea harengus, from Iceland. We here report the first detection of Ichthyophonus sp. in pink salmon in the North Atlantic Ocean. [ABSTRACT FROM AUTHOR]

Consumption of fish eggs is a major component of the trophodynamics of several marine ecosys)tems. Nevertheless, demonstrating the consumption by stomach content analysis is complex, notably due to the high digestibility of eggs. Atlantic herring (Clupea harengus) of the Downs substock migrate from the North Sea to spawn in the Eastern English Channel during winter. On the basis of an opportunistic sampling of 5 red mul)lets (Mullus surmuletus) displaying herring eggs in their stomachs, this paper was the opportunity to document for the first time the trophic importance of herring eggs in the English Channel, by combining automated analy- sis of prey images with stable isotope and C:N ratios measurement. Eggs represented more than 90% of the prey items observed in the stomachs. In addition, low δ13C and high δ15N andC:N ratios demonstrated that this obser- vation does not reflect occasional consumption of eggs, but that eggs are a common prey all through the entire spawning season. Automated image analysis demonstrated efficiency to produce semi-quantitative indicators of the diet, but manual post processing should be implemented if accuracy is needed. This work was nevertheless the opportunity to start the development of a learning set adapted to benthic organisms and available for further similar applications. This work also demonstrated the importance of a holistic approach of trophic interactions to manage exploited species. [ABSTRACT FROM AUTHOR]

Simple Summary: The Steller sea lion (SSL) is the largest Otariidae family species widely distributed in the cold North Pacific Ocean. SSLs also migrate to Hokkaido, Japan, in the winter. SSLs travel south along the Sea of Japan coast for winter to catch the herring that spawn near the coast. SSLs utilize haulouts as rest sites during herring season, but this can be affected by weather- and human-related pressures. In this study, we investigated the haulout use patterns of SSLs and the effect of human disturbance over a period of three years. The behavior of the SSLs on the haulouts differed from when they were on rookeries. Furthermore, the number of SSLs on the haulout and the duration of time they spent there reduced from the first year (lower human pressure) to the third year (human presence increased). Based on these findings, the SSLs may adjust the timing of when they enter the water to around sunrise, following the ecology of the herring and to avoid human disturbance. Therefore, it is necessary to continue investigating the relationship between the ecology of the SSLs and environmental changes in order to determine the damage that the SSLs cause to fishery interests. Steller sea lions (SSLs) migrate to the Hokkaido coast to spend the winter there, leading to conflicts arising with fishermen over herring. This study analyzed the trends in the SSLs' use of a haulout as a rest site under human pressure. From January to March in 2017, 2018, and 2019, we recorded the SSL behavior at the haulout site off Otaru City, Hokkaido, for 24 h a day using a fixed-point video recorder. We investigated three years of data to analyze the relationships between the SSL behaviors (attendance/landing–entry timings/remaining on land) and herring caught. We also monitored the SSL behaviors during changes in weather conditions and under human pressure. Throughout the three years, the SSLs used the haulout site during harsher weather or under human pressure. In 2017 and 2018, there was a correlation between the herring caught and the maximum number of SSLs on the haulout, but not in 2019. The number of SSLs on the haulout increased from evening to night; most individuals entered the water in the morning. The SSLs probably return to the water around sunrise not only for foraging but also to avoid anthropogenic pressure. The damage caused to the herring fishery by the SSLs was severe, but it is also clear that human pressure changed their behavior in response. [ABSTRACT FROM AUTHOR]

Simple Summary: The Atlantic herring is one of many migratory fish that may use the geomagnetic field to navigate on its annual migration. The exact mechanism used for detecting the geomagnetic field in fish is still an open discussion, and the two main theories on magnetic sensing in animals are in the main focus: magnetite-based or radical pair-based. Here, we explore whether the cryptochrome 4 protein of fish would be able to carry out the necessary electron transfer activation to create a radical pair to be used for magnetic sensing. Marine fish migrate long distances up to hundreds or even thousands of kilometers for various reasons that include seasonal dependencies, feeding, or reproduction. The ability to perceive the geomagnetic field, called magnetoreception, is one of the many mechanisms allowing some fish to navigate reliably in the aquatic realm. While it is believed that the photoreceptor protein cryptochrome 4 (Cry4) is the key component for the radical pair-based magnetoreception mechanism in night migratory songbirds, the Cry4 mechanism in fish is still largely unexplored. The present study aims to investigate properties of the fish Cry4 protein in order to understand the potential involvement in a radical pair-based magnetoreception. Specifically, a computationally reconstructed atomistic model of Cry4 from the Atlantic herring (Clupea harengus) was studied employing classical molecular dynamics (MD) and quantum mechanics/molecular mechanics (QM/MM) methods to investigate internal electron transfers and the radical pair formation. The QM/MM simulations reveal that electron transfers occur similarly to those found experimentally and computationally in Cry4 from European robin (Erithacus rubecula). It is therefore plausible that the investigated Atlantic herring Cry4 has the physical and chemical properties to form radical pairs that in turn could provide fish with a radical pair-based magnetic field compass sensor. [ABSTRACT FROM AUTHOR]

Climate warming is affecting the suitability and utilization of coastal habitats by marine fishes around the world. Phenological changes are an important indicator of population responses to climate‐induced changes but remain difficult to detect in marine fish populations. The design of large‐scale monitoring surveys does not allow fine‐grained temporal inference of population responses, while the responses of ecologically and economically important species groups such as small pelagic fish are particularly sensitive to temporal resolution. Here, we use the longest, highest resolution time series of species composition and abundance of marine fishes in northern Europe to detect possible phenological shifts in the small pelagic North Sea herring. We detect a clear forward temporal shift in the phenology of nearshore habitat use by small juvenile North Sea herring. This forward shift might be linked to changes in water temperatures in the North Sea. We next assessed the robustness of the effects we found with respect to monitoring design. We find that reducing the temporal resolution of our data to reflect the resolution typical of larger surveys makes it difficult to detect phenological shifts and drastically reduces the effect sizes of environmental covariates such as seawater temperature. Our study therefore shows how local, long‐term, high‐resolution time series of fish catches are essential to understand the general phenological responses of marine fishes to climate warming and to define ecological indicators of system‐level changes. [ABSTRACT FROM AUTHOR]

Understanding how marine organisms adapt to local environments is crucial for predicting how populations will respond to global climate change. The genomic basis, environmental factors and evolutionary processes involved in local adaptation are however not well understood. Here we use Atlantic herring, an abundant, migratory and widely distributed marine fish with substantial genomic resources, as a model organism to evaluate local adaptation. We examined genomic variation and its correlation with environmental variables across a broad environmental gradient, for 15 spawning aggregations in Atlantic Canada and the United States. We then compared our results with available genomic data of northeast Atlantic populations. We confirmed that population structure lies in a fraction of the genome including likely adaptive genetic variants of functional importance. We discovered 10 highly differentiated genomic regions distributed across four chromosomes. Nine regions show strong association with seasonal reproduction. One region, corresponding to a known inversion on chromosome 12, underlies a latitudinal pattern discriminating populations north and south of a biogeographic transition zone on the Scotian Shelf. Genome–environment associations indicate that winter seawater temperature best correlates with the latitudinal pattern of this inversion. The variation at two so‐called 'islands of divergence' related to seasonal reproduction appear to be private to the northwest Atlantic. Populations in the northwest and northeast Atlantic share variation at four of these divergent regions, simultaneously displaying significant diversity in haplotype composition at another four regions, which includes an undescribed structural variant approximately 7.7 Mb long on chromosome 8. Our results suggest that the timing and geographic location of spawning and early development may be under diverse selective pressures related to allelic fitness across environments. Our study highlights the role of genomic architecture, ancestral haplotypes and selection in maintaining adaptive divergence in species with large population sizes and presumably high gene flow. [ABSTRACT FROM AUTHOR]

Body size is a key component of individual fitness and an important factor in the structure and functioning of populations and ecosystems. Disentangling the effects of environmental change, harvest and intra‐ and inter‐specific trophic effects on body size remains challenging for populations in the wild. Herring in the Northwest Atlantic provide a strong basis for evaluating hypotheses related to these drivers given that they have experienced significant warming and harvest over the past century, while also having been exposed to a wide range of other selective constraints across their range. Using data on mean length‐at‐age 4 for the sixteen principal populations over a period of 53 cohorts (1962–2014), we fitted a series of empirical models for temporal and between‐population variation in the response to changes in sea surface temperature. We find evidence for a unified cross‐population response in the form of a parabolic function according to which populations in naturally warmer environments have responded more negatively to increasing temperature compared with those in colder locations. Temporal variation in residuals from this function was highly coherent among populations, further suggesting a common response to a large‐scale environmental driver. The synchrony observed in this study system, despite strong differences in harvest and ecological histories among populations and over time, clearly indicates a dominant role of environmental change on size‐at‐age in wild populations, in contrast to commonly reported effects of fishing. This finding has important implications for the management of fisheries as it indicates that a key trait associated with population productivity may be under considerably less short‐term management control than currently assumed. Our study, overall, illustrates the need for a comparative approach within species for inferences concerning the many possible effects on body size of natural and anthropogenic drivers in the wild. [ABSTRACT FROM AUTHOR]

Management strategy evaluation (MSE) provides a mechanism to test the relative performance of alternative management strategies on a fishery. For Pacific herring in Prince William Sound, Alaska, no directed fisheries have occurred in over 30 years, providing an opportunity to evaluate potential management strategies before a fishery is opened. Here we evaluate and compare 10 harvest control rules (HCRs) ranging from simple threshold rules to rules accounting for population age structure, biomass trends, and weight distribution using an MSE integrated with a fully Bayesian stock assessment estimation model. We developed a utility function that shows simple threshold HCRs outperform the more complex rules, especially for catch stability. According to this utility function, the best rule had a lower limit threshold than the current default rule, while the worst rule had a higher limit threshold. Our simulations demonstrate that sufficient computing power exists for MSEs based on Bayesian estimation methods, thus opening a pathway for MSEs to simulation test probabilistic control rules, which provide a buffer against scientific uncertainty and should reduce the risk of overfishing. [ABSTRACT FROM AUTHOR]

Lipid-related thiamine (vitamin B1) deficiency of Baltic salmon (Salmo salar), the M74 syndrome, is generally caused by feeding on abundant young sprat (Sprattus sprattus) in the Baltic Proper, the main foraging area of these salmon. In 2014, a strong year-class of sprat was hatched in the Baltic Proper, and a strong herring (Clupea harengus) year-class was hatched in the Gulf of Bothnia, where herring is the dominant salmon prey. The fatty acid (FA) signatures of prey fish in muscle or eggs of second sea-year spawners suggested that 27% of wild River Simojoki and 68% of reared River Dal salmon remained in the Gulf of Bothnia in 2014 instead of continuing to the Baltic Proper. In 2016, 23% of the M74 females of the River Simojoki and 58% of the River Dal originated from the Gulf of Bothnia, and 13% and 16%, respectively, originated from the Baltic Proper. Some salmon from the River Neris in the southern Baltic Proper had also been feeding in the Gulf of Bothnia. In general, low free thiamine (THIAM) concentration in eggs was associated with high lipid content and high docosahexaenoic acid (DHA, 22:6n−3) and n−3 polyunsaturated FA (n−3 PUFA) concentrations in muscle but not in eggs. A higher THIAM concentration and lower proportions of DHA and n−3 PUFAs in Arctic Ocean salmon eggs, despite higher egg lipid content, indicated that their diet contained fewer fatty fish than the Baltic salmon diet. Hence, M74 originated by foraging heavily on young fatty sprat in the Baltic Proper or herring in the Gulf of Bothnia. [ABSTRACT FROM AUTHOR]

Understanding the molecular mechanisms underlying individual responses to environmental changes is crucial for species conservation and management. Pelagic fishes including Atlantic herring (Clupea harengus) are of particular interest because of their key ecological and economic roles and their susceptibility to a changing ocean from global warming. Temperature and photoperiod have been linked with spawning time and location in adult herring, but no study has thus far investigated the role of environmental factors on gene regulation during the vulnerable early developmental stages. Here, we examine DNA methylation patterns of larval herring bred under two temperatures (11°C and 13°C) and photoperiod (6 and 12 h) regimes in a 2 × 2 factorial design. We found consistently high levels of global methylation across all individuals and a decline in global methylation with increased developmental stage that was more pronounced at 13°C (p ≤ 0.007) than at 11°C (p ≥ 0.21). Most of the differentially methylated sites were in exon and promoter regions for genes linked to metabolism and development, some of which were hypermethylated at higher temperature. These results demonstrate the important role of DNA methylation during larval development and suggest that this molecular mechanism might be key in regulating early‐stage responses to environmental stressors in Atlantic herring. [ABSTRACT FROM AUTHOR]

Typically, in Ireland, male/female marine fish gonads are discarded at sea or processed onshore for low-value fishmeal. This study aimed at a) developing two new ready-to-eat fish spread products from underutilized herring milt with either cod roe or plaice roe and b) testing the products acceptance with consumers. Chi-square tests on contingency tables were used to analyze open-ended questions relating to consumer likes and dislikes of the products. The main characteristics showed sensory drivers for liking was flavor, color, and texture with similar characteristics also used for disliking. Colorimetry and texture analysis showed significant differences (P <.05) between the products which were also detected by panelists during sensory evaluation (color, texture, appearance, P <.05). Penalty analysis of JAR showed overall liking was most impacted by level of fishiness. Positive acceptance of products suggests that underutilized fish by-products could be used successfully in Irish ready-to-eat foods thereby adding value while reducing waste. [ABSTRACT FROM AUTHOR]

Oil spills threaten the productivity of marine forage fish that spawn in shallow shoreline habitats. In western North America, this includes Pacific herring (Clupea pallasii), a keystone species for marine food webs. Crude oil-derived polycyclic aromatic hydrocarbons (PAHs) are highly toxic to herring embryos and larvae. Despite our understanding of individual-based toxicity, the impacts of oil spills at the population-scale remain uncertain. We modeled the response of Puget Sound herring stocks to simulated oil spills and found that declining stocks are less likely to withstand the short-term impacts of a small, localized spill. Moreover, conventional stock assessment methods may only detect large population declines in response to high rates of mortality in a single year, or sustained losses across multiple year classes. We discuss the importance of herring life history and environmental variation on the predictive usefulness of conventional population modeling as a basis for estimating injury to highly variable marine forage fish resources. [ABSTRACT FROM AUTHOR]

Investigating the movements and site fidelity of individuals enhances our understanding of population ecology and structure. Killer whales occur around the coast of Iceland; however, information on the connectivity between different regions is limited to herring grounds, where they are observed frequently. In this study, we used photo-identification data to investigate the movements and site fidelity of whales within (South and West) and outside (Southwest, Northwest, Northeast and East) Icelandic herring grounds. Additionally, we used a 10-year photo-identification dataset in the South to investigate long-term site fidelity patterns to a single location. Of the 440 individuals sighted more than once, nearly half (48%) moved between herring grounds and site fidelity was higher within, compared to outside, herring grounds. Outside herring grounds, individuals showed: more movement from Southwest to West compare to South, indicating this region is not exclusively a passage between herring grounds; low site fidelity to the Northeast with fewer photographic matches to other regions, suggesting individuals found here may be part of an offshore population that occasionally visits the area; and low proportion of matches to other regions in the Northwest and East, although small sample sizes precluded firm conclusions. Finally, long-term residency of killer whales in the South showed dynamic patterns, likely caused by prey availability and/or environmental changes. This study elucidates the complexities of killer whale occurrence and connectivity within the North Atlantic and suggests population structure that should be further investigated for appropriate regional conservation assessments. [ABSTRACT FROM AUTHOR]

Aim: Bergman patterns, the tendency of organisms to be larger at higher latitudes and lower temperatures, are a well‐studied biogeographic pattern. Yet, there is no consensus on the driver or underlying mechanisms. We aim to scrutinize the influence of several key proposed drivers of Bergmann patterns (temperature, seasonal light availability, prey size and seasonal abundance) on optimal body size in planktivorous fishes across high latitudes in the Northeast Atlantic. Location: Northeast Atlantic between 55 and 75° N, with implications for high‐latitude oceans globally. Time period: Present day. Major taxa studied: Pelagic planktivorous fishes, with Atlantic herring (Clupea harengus) as model organism. Methods: We use a model that incorporates explicit mechanisms for vision‐based feeding and temperature‐dependent physiology of a planktivorous fish to explore how intrinsic and extrinsic constraints affect energy budgeting and thereby expected optimal body size based on bioenergetics. We run the model at latitudes with increasing seasonality and test the individual and joint effects of relevant drivers. Results: A Bergmann pattern emerges from the interaction between visual feeding opportunities and temperature‐dependent physiology. Small individuals profit from faster energy processing at higher temperatures in the south, whereas large individuals benefit from a lower metabolic cost at colder temperatures and more daylight hours for feeding in the north. In isolation temperature, daylight hours, and prey size each produced Bergmann patterns, but the most pronounced pattern arose from all drivers combined. Main conclusions: Studying biogeographic body size patterns requires a holistic view, accounting for interactions between drivers and both intrinsic and extrinsic constraints on energy budgeting. Across latitudes, temperature effects on digestion and metabolism interact with effects of light availability, prey size and abundance on food accessibility, and thereby shape the optimal size. Our study highlights how details of ecological mechanisms and lifestyles are important for improving predictive ability. [ABSTRACT FROM AUTHOR]

Clupeid fish species are widely distributed and of highly variable stock sizes. In the North Sea, the common clupeid species are herring (Clupea harengus) and sprat (Sprattus sprattus), but during recent decades, the generally more southerly distributed sardine (Sardina pilchardus) have been more frequently observed. Comparative studies of early life stages of small pelagic clupeids are scarce, and their abilities to co‐exist and relations to environmental characteristics are vastly understudied. We here investigated and compared distributional patterns of co‐occurring larval sprat and sardine in the North Sea, hypothesizing that they are separated into spatial niches linked to specific hydrographical characteristics. Sampling was carried out by a large ring‐net during standard fish surveys (IBTS Q3) in August 2018, 2019, and 2020. Sprat larvae were found widespread across the area of investigation, with the highest concentration in the central North Sea off the eastern and northern flanks of Dogger Bank, where abundances could reach 20 larvae/m2. Sardine larvae, on the other hand, showed their highest abundances in the Southern and German Bights. Distributions of the two species appeared complementary, and statistical correlations were indicative of separate hydrographical niches, where sardine larvae resided in relatively warmer and fresher water. The relative abundances of sardine versus sprat varied between years. Sardine larvae were especially abundant in 2020, twice as abundant as sprat, and observations indicate increasing importance of sardines in the North Sea. [ABSTRACT FROM AUTHOR]

We characterized a natural sea louse epizootic of Caligus clemensi and the effects of parasitism on Pacific herring Clupea pallasii in Port Angeles Harbor, WA, USA. Infestation prevalence on newly metamorphosed age 0 Pacific herring reached 100% prevalence by mid-August. At this time, the mean louse intensity was 4.6 lice/fish, and a positive correlation occurred between louse intensity and herring body length. The epizootic then waned, with infestation prevalence decreasing to less than 25% and the mean parasite intensity falling below 1 louse. While skin injuries were not detected, motile lice preferentially aggregated around head and anterior dorsal areas. However, louse tropism became evenly distributed over the body as the parasite intensity increased. Louse-induced mortality in herring was negligible in controlled experiments. These results indicate that Caligus clemensi epizootics reach high prevalence, but also fade from mid-summer to early fall. Due to the predominant presence of motile copepod stages, we suggest that the epizootic fades because lice complete their life cycle and dislodge from the host; however, multiple explanations for epidemic fading are possible. [ABSTRACT FROM AUTHOR]

Migration can have a profound influence on rates and patterns of phenotypic evolution. Diadromy is the migration between marine and freshwater habitats for feeding and reproduction that can require individuals to travel tens to thousands of kilometers. The high energetic demands of diadromy are predicted to select for ecomorphological traits that maximize swimming and locomotor efficiency. Intraspecific studies have shown repeated instances of divergence among diadromous and nondiadromous populations in locomotor and foraging traits, which suggests that at a macroevolutionary scale diadromous lineages may experience convergent evolution onto one or multiple adaptive optima. We tested for differences in rates and patterns of phenotypic evolution among diadromous and nondiadromous lineages in Clupeiformes, a clade that has evolved diadromy more than 10 times. Our results show that diadromous clupeiforms show convergent evolution for some locomotor traits and faster rates of evolution, which we propose are adaptive responses to the locomotor demands of migration. We also find evidence that diadromous lineages show convergence into multiple regions of multivariate trait space and suggest that these respective trait spaces are associated with differences in migration and trophic ecology. However, not all locomotor traits and no trophic traits show evidence of convergence or elevated rates of evolution associated with diadromy. Our results show that long-distance migration influences the tempo and patterns of phenotypic evolution at macroevolutionary scales, but there is not a single diadromous syndrome. [ABSTRACT FROM AUTHOR]

Applying simple linear regression models, an economist analyzed a published dataset from an influential annual ranking in 2016 and 2017 of consumer outlets for Dutch New Herring and concluded that the ranking was manipulated. His finding was promoted by his university in national and international media, and this led to public outrage and ensuing discontinuation of the survey. We reconstitute the dataset, correcting errors and exposing features already important in a descriptive analysis of the data. The economist has continued his investigations, and in a follow‐up publication repeats the same accusations. We point out errors in his reasoning and show that alleged evidence for deliberate manipulation of the ranking could easily be an artifact of specification errors. Temporal and spatial factors are both important and complex, and their effects cannot be captured using simple models, given the small sample sizes and many factors determining perceived taste of a food product. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess the impact of smoking processes applied in the Ivory Coast on the quality of sea herring (Sardinella maderensis) collected from fishermen in the port of Abidjan. The samples were divided into three groups and smoked using three smoking processes. The first two processes are based on including two artisanal smoking kilns with the use of mangrove wood as combustible for one, and the rubber wood for the other. The third process is based on improved kiln using FAO-Thiaroye processing Technique (FTT) with the combination of mangrove wood and coconut shells as combustible. The results revealed that the highest values for pH (6.57 ± 0.09), moisture (54.14 g/100 g ± 1.61), peroxide value (31.75 ± 1.89 meq O2/kg of fish), and total volatile basic nitrogen (37.03 ± 2.78 mg/100 g of fish) were found in samples made with traditional smoking systems using rubberwood. The factorial discriminant analysis (FDA) applied to the concatenated fluorescence spectra of aromatic amino acids and nucleic acids (AAA + NA) resulted in a 78.52% correct classification rate of samples. Samples treated with rubberwood were the best discriminated, while those treated with mangrove wood and mangrove wood combined with coconut shell remained confused due to the common used fuel: mangrove wood. [ABSTRACT FROM AUTHOR]

Causes of population collapse and failed recovery often remain enigmatic in marine forage fish like Pacific herring (Clupea pallasii) that experience dramatic population oscillations. Diseases such as ichthyophoniasis are hypothesized to contribute to these declines, but lack of long-term datasets frequently prevents inference. Analysis of pathogen surveillance and population assessment datasets spanning 2007–2019 indicate that the age-based prevalence estimate of Ichthyophonus infection was, on average, 54% greater among a collapsed population of Pacific herring (Prince William Sound, Alaska, USA) as compared to a nearby population (Sitka Sound, Alaska, USA) that is relatively robust. During the study years, the age-based infection prevalence ranged from 14 to 44% in Prince William Sound and 5 to 33% in Sitka Sound. At both sites, the age-based infection prevalence declined over time, with an average decrease of 7% per year. Statistical analyses indicated that infection prevalence between the two populations was reduced by regional factors affecting both sites, and that these factors were independent of herring density. Infection prevalence in both populations was positively correlated with herring age and negatively correlated with the Pacific Decadal Oscillation. This study demonstrates how synthesis of environmental, stock assessment, and disease assessment data can be leveraged to elucidate epidemiological trends in diseases of wild fish. [ABSTRACT FROM AUTHOR]

Repetitive DNA make up a considerable fraction of most eukaryotic genomes. In fish, transposable element (TE) activity has coincided with rapid species diversification. Here, we annotated the repetitive content in 100 genome assemblies, covering the major branches of the diverse lineage of teleost fish. We investigated if TE content correlates with family level net diversification rates and found support for a weak negative correlation. Further, we demonstrated that TE proportion correlates with genome size, but not to the proportion of short tandem repeats (STRs), which implies independent evolutionary paths. Marine and freshwater fish had large differences in STR content, with the most extreme propagation detected in the genomes of codfish species and Atlantic herring. Such a high density of STRs is likely to increase the mutational load, which we propose could be counterbalanced by high fecundity as seen in codfishes and herring. [ABSTRACT FROM AUTHOR]

Despite the importance of recruitment for population dynamics and assessing stock status, limited information exists on the relative influence of various ecosystem and demographic factors on the recruitment dynamics of marine fishes. We develop a statistical framework to identify the ecosystem and demographic factors influencing the recruitment of marine fishes and facilitate improved predictions of recruitment. We demonstrate the approach by examining the relative influence of ecosystem and demographic factors on the recruitment of southern Gulf of St. Lawrence spring- and fall-spawning Atlantic herring (Clupea harengus) stocks, highlighting the benefit of considering multiple factors to better understand recruitment trends. We found that different combinations of biological and physical ecosystem factors along with demographic factors had a significant influence on the recruitment and recruitment rate of spring- and fall-spawning herring. The study emphasizes the value of considering ecosystem characteristics when examining recruitment, provides a framework for researchers to investigate and model recruitment of other fish populations, and supports the continued development and implementation of ecosystem-based fisheries management approaches for species, such as Atlantic herring. [ABSTRACT FROM AUTHOR]

Thread herrings (Opisthonema spp.) are economically important fish species in the Tropical Eastern Pacific. Knowledge of the parasitofauna of commercially exploited species is useful as it can increase our understanding of fish biology and ecology. However, our knowledge of the parasites of Opisthonema spp. is limited. During a fisheries exploration survey in April 2022, samples of Opisthonema bulleri and O. libertate were collected from three oceanographic stations in the Gulf of Tehuantepec in the Mexican Pacific. Parasitological analysis of these materials uncovered four parasite species: Myosaccium ecaude (Trematoda), Cribromazocraes sp. (Monogenea), Pseudoterranova sp. (Nematoda), and an unidentified crustacean of the family Pennellidae (Copepoda). All these species appeared rarely, except for M. ecaude, which reached a prevalence of 100%. The median intensity of M. ecaude infection was significantly higher in O. bulleri than in O. libertate. We analyzed the relationship between parasitic infection intensity and three host traits (fork length, body weight, and age). Only body weight showed a significant positive association with intensity. Future studies are required to analyze the possible effects of seasonality, locality, and host ontogeny on the occurrence of M. ecaude in thread herrings in the Tropical Eastern Pacific. [ABSTRACT FROM AUTHOR]

Recruitment success of marine fishes is generally considered to be highly dependent on larval growth and survival. In temperate ecosystems, fish larvae are sensitive to food limitation during the low productivity seasons, particularly if water temperatures and concomitant larval metabolic costs increase due to climate change. We combined 7 years of in situ sampling of larval fish, novel observations on zooplankton via automated image analyses, and larval physiological modeling to explore feeding conditions of Atlantic herring larvae (Clupea harengus) in the North Sea. The observed plankton size‐structure was close to the theoretical optimum for larval foraging, but not the biomass. Our results for autumn larvae supported Hjort's critical period hypothesis: small first‐feeding larvae were predicted to have a high probability of starvation, whereas larvae > 13 mm were able to reach their maximal growth capacity. In winter, the majority of herring larvae of all tested sizes (5–27 cm) experienced food‐limitation with over 35% probability of starvation. Sensitivity analysis suggested that young herring larvae improve their growth performance and probability of survival if feed not only on copepods and their life‐stages but include other microplankters in their diet. Given projected warming of the North Sea, our model predicts that herring larvae would require 28% (35%) more prey biomass in autumn (winter) to sustain their growth and survival in the future. This finding together with the ongoing low recruitment of North Sea herring underscore the importance of future micro‐ and mesoplankton monitoring within a scope of wintertime larval fish surveys. [ABSTRACT FROM AUTHOR]

Annual life history events, such as migration and spawning in fish, are often timed to match seasonal fluctuations in environmental conditions. Understanding phenological patterns and their drivers is needed to conserve vulnerable fish populations, particularly as climate change is disrupting seasonal transitions. In this study, we examined the phenology of spring spawning migrations of river herring, the alewife (Alosa pseudoharengus) and the blueback herring (A. aestivalis), in 4 rivers of Chesapeake Bay over 7 years (2013-2019). We used imaging sonar and weekly biological samples to estimate species-specific hourly fish counts in the Choptank River, Deer Creek (a tributary of Susquehanna River), Marshyhope Creek (a tributary of Nanticoke River), and the Patapsco River. Our results indicate that patterns of water temperature in spring drive spawning migrations at seasonal, daily, and hourly scales. The relationship between fish counts and other environmental factors, such as streamflow, lunar phase, turbidity, wind stress, and tides, were annually inconsistent, and their influences on migrations may be river specific. For both species, distinct diel patterns in movement were observed. Migrations were diurnal in the Choptank River and Marshyhope Creek but nocturnal in Deer Creek and the Patapsco River. Observed interannual and inter-river variation in phenology and the influence of non-temperature factors on migrations highlight the need for long-term, multi-river monitoring of river herring in Chesapeake Bay. [ABSTRACT FROM AUTHOR]

A limit reference point (LRP) is defined as a level of biomass to be avoided with high probability, which should be selected to protect fish stocks from "serious harm". We present an evidence-based approach for diagnosing serious harm and apply it to the selection of LRPs for five Pacific herring (Clupea pallasii) stocks in British Columbia (BC). Natural mortality (M) is estimated to be time varying and has increased more than it declined over the past three decades, which presents a challenge for estimation of equilibrium reference points based on maximum sustainable yield. We present a semi-empirical approach for developing LRPs, which examines surplus production in relation to spawning biomass to determine whether there is evidence for low productivity, low biomass (LP-LB) states consistent with serious harm. Three stocks showed evidence of persistent LP-LB states that resulted in periods of fishery closures. Based on these results, an LRP of 30% of unfished spawning biomass (0.3B0) was recommended and adopted for management of all five major stocks of BC Pacific herring. [ABSTRACT FROM AUTHOR]

The Pacific thread herring, Opisthonema libertate, is a fishery resource in the eastern tropical Pacific, yet its population dynamics are poorly understood. The aims of this work were to document the metazoan parasite species in O. libertate from the Gulf of California in Mexico, determine latitudinal changes in their infection levels, and assess their potential as biological tags. Six parasitic species were identified: Myosaccium ecaude and Parahemiurus merus digeneans, Cribromazocraes cf. travassosi and Mazocraeoides georgei monogeneans, Pseudoterranova sp. nematodes, and Lepeophtheirus sp. copepods. The monogenean and copepod species are reported for the first time in O. libertate. Many fish were infected with digeneans, and there was a rare occurrence of other parasites. While the prevalence and median intensity of M. ecaude and P. merus significantly varied among sampling localities, a multivariate analysis revealed a distinct separation between some localities; these results suggest that individual fish form several discrete populations. However, the utility of these parasites as biological tags will be further probed because they cannot satisfy all requirements for good biological tags. The present results might be helpful in complementing other techniques to determine the movement and stock structure of O. libertate, albeit with certain limitations. [ABSTRACT FROM AUTHOR]

In this paper, we have studied the dynamics of two species, ecological model, considering two economically beneficial marine species herring (Clupea harengus) as predator and mysida (Hemimysis anomala) as its prey with Beddington–DeAngelis functional response, the effect of prey refuge and linear harvesting in both populations. The local and global stability of the equilibrium points has been established here. The axial equilibrium point goes through transcritical bifurcation depending on the harvesting effort of both species. The interior equilibrium point goes through super critical Hopf bifurcation depending on prey intrinsic growth rate. Additionally, we have determined the suitable value of the MSY policy for the harvesting and find suitable harvesting level using the optimal control theory, such that both the species persist simultaneously. Finally, numerical simulations have been performed to justify the theoretical findings. It is clear from the numerical simulations that the prey refuge and mutual interference between predators stabilized the unstable system to a stable one. This finding could give some clue to the experimental biologist and business personnel for making management decisions in controlling the harvesting strategies of the two economic beneficial fish populations, mysida and herring. [ABSTRACT FROM AUTHOR]

Jack Herring had three mid-1960s numerical papers on Rayleigh-Bénard thermal convection that might seem primitive by today's standards, but already encapsulated many of the questions that are still being asked. All of them use severely truncated versions of the incompressible Navier–Stokes–Boussinesq equations with only one, or just a few, horizontal Fourier modes. In the first two papers, 1963 and 1964, the presented results used only one Fourier mode  α  and three variables. The single mode's variables are its vertical velocity profile  w α (z , t) , its temperature profile  θ α (z , t)  and the horizontally uniform vertical profile of the background temperature  ψ (z , t) . All of the second- and third-order terms are ignored except the convective heat flux  w θ ¯ . The objective was to find asymptotic steady-state solutions. Each paper found evidence for the one-third Nusselt versus Rayleigh scaling of  N u ∼ R a 1 / 3 , originally derived from Malkus' maximum flux principle. The 1963 paper uses free-slip upper and lower boundaries, with magnitudes of  N u  that are a factor of three larger than the experiments. In the 1964 paper, by introducing no-slip/rigid boundary conditions, the magnitude of  N u  dropped to within 20% of the experimental values. Both  N u (R a)  relations are in good agreement with circa-1990 direct numerical simulations (DNS). This dependence upon the boundary condition at the walls suggests that to obtain physically realistic scaling, no-slip boundary conditions are necessary. The third paper is discussed only in terms of what it might have been aiming to accomplish and its relation to the earlier free-slip results. [ABSTRACT FROM AUTHOR]

The Lower Cretaceous (Albian) clupeomorph fishes of the Pietraroja Plattenkalk were among the first fishes described for this celebrated Italian Konservat-Lagerstätte. However, a detailed anatomical and phylogenetic study has never been carried out on these fishes in order to clarify their taxonomic status, systematic position, and relationships within the Clupeomorpha. The specimens examined herein exhibit diagnostic features that clearly support their alignment with the extinct double-armoured herring order Ellimmichthyiformes. Based on the presence of an incomplete series of heart-shaped predorsal scutes, a new combination, Armigatus elatus (Costa, 1850), and the new species Armigatus plinii sp. nov. are recognized as the oldest representatives of the family Armigatidae, whereas a unique combination of features allows us to recognize most of the specimens as a new representative of the family Paraclupeidae, Paraclupea pietrarojae sp. nov. The presence of lower Albian species of Armigatus and Paraclupea in the Western Tethys extends the temporal and biogeographical range of these widely distributed genera, providing additional information for our understanding of the evolutionary and biogeographical history of the double-armoured herrings. [ABSTRACT FROM AUTHOR]

Historical loss of river and stream habitats due to impassable dams has contributed to the severe decline of many fish species. Anadromous fishes that migrate from the sea to freshwater streams to spawn have been especially impacted as dams restrict these fish from accessing ancestral spawning grounds. In 2018, Bloede Dam was removed from the Patapsco River near Baltimore, Maryland, restoring approximately 100 km of potential habitat for migratory fish. We assessed the response of anadromous river herring, alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis), to this dam removal by monitoring environmental DNA (eDNA) and eggs from 2015 to 2021 at locations upstream and downstream of the dam site during their spawning migrations. We additionally assessed the presence of fish by collecting electrofishing samples and tracked the movements of individual adult fish within the river using passive integrated transponder (PIT) tags. No adult river herring, eDNA, or eggs were detected upstream of Bloede Dam in the four years prior to its removal despite the presence of a fish ladder. Our results suggest initial habitat use recovery by spawning river herring in the first year post-removal, although a relatively small proportion of the population in the river used the newly accessible habitat. In the three years post-removal, the likelihood of detecting river herring eDNA upstream of the former dam site increased to 5% for alewife and 13% for blueback herring. Two adult fish were also collected in electrofishing samples upstream of the dam site in 2021. We found no evidence of changes in egg abundance and no tagged fish were detected upstream of the dam site post-removal. While long term monitoring is needed to assess population changes, this study highlights the value of integrating methods for comprehensive understanding of habitat use following dam removal. [ABSTRACT FROM AUTHOR]

Atlantic herring (Clupea harengus) and Pacific herring (C. pallasii) are sister species that split from a common ancestor about 2 million years ago. Balsfjord, a subarctic fjord in Northern Norway, harbors an outpost population of Pacific herring within the range of the Atlantic herring. We used whole genome sequencing to show that gene flow from Atlantic herring into the Balsfjord population has generated a stable hybrid population that has persisted for thousands of generations. The Atlantic herring ancestry in Balsfjord was estimated in the range 25–26%. The old age and large proportion of introgressed regions suggest there are no obvious genetic incompatibilities between species. Introgressed regions were widespread in the genome and large, with some in excess of 1 Mb, and they were overrepresented in low-recombination regions. We show that the distribution of introgressed material is non-random; introgressed sequence blocks in different individuals are shared more often than expected by chance. Furthermore, introgressed regions tend to show elevated divergence (F ST) between Atlantic and Pacific herring. Together, our results suggest that introgression of genetic material has facilitated adaptation in the Balsfjord population. The Balsfjord population provides a rare example of a stable interspecies hybrid population that has persisted over thousands of years. [ABSTRACT FROM AUTHOR]

In a warming world, both the metabolic rates of ectotherm predators and the phenology of their prey organisms is subject to change. Knowledge on how intrinsic and extrinsic factors govern predator–prey interactions is essential in order to understand how the environment regulates the vital rates of consumers. Controlled experiments, however, simultaneously testing behavioural and growth responses of the larvae of fish and other ectotherm organisms in different feeding regimes are scarce.Prey size (PS) selection was determined for young Atlantic herring Clupea harengus L. larvae offered 100‐ to 850‐μm copepods Acartia tonsa at five different concentrations. In separate, 4‐ (13°C) or 7‐day (7°C) trials, the effect of prey size on larval foraging behaviour, specific growth rate (SGR) and biochemical condition (RNA:DNA, RD, a proxy for individual instantaneous growth) was tested.Preferred (selected) PS was similar at all prey concentrations but increased from 3% to 5% predator length with increasing larval size. At various temperatures, dome‐shaped relationships existed between PS and larval RD (and accordingly SGR). Compensatory changes in foraging behaviour (pause and feeding strike frequencies) existed but were not adequate to maintain positive SGR when available prey were substantially smaller than those preferred by larvae.A physiology‐based model predicted that larvae depended more heavily on optimal prey sizes at the colder versus warmer temperature to grow well and that the profitable prey niche breadth (the range in prey sizes in which growth was positive) increased at warmer temperatures.Seemingly subtle match‐mismatch dynamics between ectotherm predators and their preferred prey size can have large, temperature‐dependent consequences for rates of growth and likely survival of the predator. To the best knowledge, this was the first study to directly quantify the "costs and trade‐offs" of optimal foraging in marine fish larvae. [ABSTRACT FROM AUTHOR]

The thread herring Opisthonema oglinum (Lesueur, 1818) is a small pelagic fish distributed in the western margin of the Atlantic Ocean from the United States to Argentina. It is a target species for diverse commercial fisheries, including the Brazilian industrial purse seine fleets that operate in the Southeastern Brazilian Bight. To investigate the geographic variation in the thread herring populations in this fishing ground, sagittal otoliths were collected from two areas: Rio de Janeiro (RJ: 23°04′ S, 44°03′ W) and Santa Catarina (SC: 26°05′ S, 48°18′ W). Otolith shape analyses and multi-elemental signatures were statistically evaluated using elliptical Fourier descriptors and elemental/Ca ratios. Remarkable differences in the thread herring otoliths between the two areas were found. The previous scenario in which the thread herring constitutes a single panmictic population in the Atlantic Ocean is now debatable. The implications of these results in terms of rational fisheries management for this species are highlighted. [ABSTRACT FROM AUTHOR]

To provide insights into the challenging problem of turbulent convection, Jack Herring used a greatly truncated version of the complete Boussinesq equations containing only one horizontal wavenumber. In light of later observations of a robust large-scale circulation sweeping through convecting enclosures at high Rayleigh numbers, it is perhaps not an implausible point of view from which to reexamine high-Rayleigh-number data. Here we compare past experimental data on convective heat transport at high Rayleigh numbers with predictions from Herring's model and, in fact, find excellent agreement. The model has only one unknown parameter compared to the two free parameters present in the lowest-order least-squares power-law fit. We discuss why the underlying simplistic physical picture, meant to work at Rayleigh numbers slightly past the critical value of a few thousand, is consistent with the data when the single free parameter in it is revised, over some eleven decades of the Rayleigh number—stretching from about a million to about 10 17 . [ABSTRACT FROM AUTHOR]

The pioneering applications of the methods of theoretical physics to the turbulence statistical closure problem are summarised. These are: the direct-interaction approximation (DIA) of Kraichnan, the self-consistent-field theory of Edwards, and the self-consistent-field theory of Herring. Particular attention is given to the latter, in terms of its elegance and its pedagogical value. We then concentrate on the assessment of these theories and take the historical route of Kraichnan's diagnosis of the failure of DIA, followed by Edwards's analysis of the failure of his self-consistent theory, when compared to the Kolmogorov spectrum. As all three theories are closely related, these analyses also shed light on Herring's theory. The second-generation theories that grew out of this assessment are then discussed. First, there were the Lagrangian theories, initially stemming from the work of Kraichnan and Herring, and later the purely Eulerian local energy-transfer (LET) theory. The latter is significant because its development exposes the underlying problems with the pioneering theories in terms of the basic physics of the inertial energy transfer. In particular, later work allows us to assign a unified explanation of the incompatibility of all three pioneering theories with the Kolmororov spectrum, in that they are all Markovian approximations (in wavenumber) to the non-Markovian phenomenon of fluid turbulence. In the interests of completeness, we briefly review the formalisms of Wyld and Martin, Siggia, and Rose. More recent developments are also discussed, in order to bring the subject up to the present day. [ABSTRACT FROM AUTHOR]

Among all human-induced pressures, ocean warming is expected to be one of the major drivers of change in marine ecosystems. Fish species are particularly vulnerable during embryogenesis. Here, the impact of temperature was assessed on embryonic stages of Atlantic herring (Clupea harengus), a species of high socio-economic interest, with a particular focus on the under-studied eastern English Channel winter-spawning component (Downs herring). Key traits linked to growth and development were experimentally evaluated at three temperatures (8°C, 10°C and 14°C), from fertilization to hatching, in standardized controlled conditions. Overall negative impacts of increased temperature were observed on fertilization rate, mean egg diameter at eyed stage, hatching rate and yolk sac volume. A faster developmental rate and a change in development stage frequency of newly hatched larvae were also observed at higher temperature. Potential parental effects were detected for four key traits (i.e. fertilization rate, eyed survival rate, mean egg diameter and hatching rate), despite a limited number of families. For instance, a large variability among families was shown in survival rate at eyed stage (between 0 and 63%). Potential relationships between maternal characteristics and embryo traits were therefore explored. We show that a substantial proportion of variance (between 31 and 70%) could be explained by the female attributes considered. More particularly, age, traits linked to life history (i.e. asymptotic average length and Brody growth rate coefficient), condition and length were important predictors of embryonic key traits. Overall, this study constitutes a stepping-stone to investigate potential consequences of warming on Downs herring recruitment and provides first insights on potential parental effects. [ABSTRACT FROM AUTHOR]

Atlantic herring (Clupea harengus) are economically and ecologically significant but have been in decline in Atlantic Canada due to an uncertain combination of environmental recruitment controls, predation, and fishing (commercial fishery and poorly documented bait removals). Fisheries and Oceans Canada partially closed Atlantic mackerel (Scomber scombrus) and herring fisheries in March 2022 amid controversy and disagreement. Here, we develop a conceptual model for natural and anthropogenic controls on herring abundance centered on the southern Gulf of St. Lawrence (sGSL) and evaluate the likely importance of each. We provide the first estimates of the magnitude of bait fishery withdrawals in the sGSL. The decline in sGSL herring is likely driven by natural predation exacerbated by fishing. Bait fishery removals were 182 tonnes in 2021, suggesting that previous estimates for removals of spring-spawning herring were ∼30% too low. Fisheries closure is consistent with a precautionary approach given uncertainties and irreversibility of stock collapse. Ecosystemic models are needed but will be difficult to develop given the incomplete understanding of prey substitutability and net effect of interacting environmental processes. [ABSTRACT FROM AUTHOR]

The incidental catch of non-target species in fishing gear (i.e., bycatch) is a global threat to sustainability and conservation in marine systems. Seabirds experience substantial bycatch mortality, with gillnets having the greatest impacts of any fishing gear. Widespread mitigation to reduce seabird bycatch in gillnet fisheries is tenuous, and information on bycatch in inshore surface-set gillnets remains a major knowledge gap. To help address these issues, we collaborated with commercial fishers to test the efficacy of high-contrast banners designed to alert seabirds. In waters of Newfoundland, Canada, banners were attached to surface-set gillnets for Atlantic Herring Clupea harengus and were compared with simultaneously unmodified control nets within the foraging ranges of major seabird colonies. The banners reduced target catch, creating a nonviable option for fishers. Seabird bycatch was low, although it may have been more substantial than indicated by local information sources. Bycatch included fish species of concern (Atlantic Salmon Salmo salar and Porbeagle Shark Lamna nasus). Owing to the episodic nature of seabird and other non-target catch, collaboration with fishers is needed to continue long-term monitoring of inshore gillnet bycatch. [ABSTRACT FROM AUTHOR]

Examining temporal changes in the growth and generation time of fish species can be valuable for understanding population responses to different management measures and environmental conditions. Atlantic herring (Clupea harengus-Linnaeus, 1758) is an ecologically and commercially important pelagic forage fish species that occupies the southern Gulf of St. Lawrence. Here, we developed von Bertalanffy growth curves and estimated yearly values of generation time for NAFO Division 4TVn Atlantic herring for the years from 1988 to 2021. The results indicate a temporal reduction in the growth and generation time of both spring and fall spawning herring. Over the time series, the generation time of spring and fall spawners reduced by approximately 1 and 2 years, respectively. Furthermore, the average generation time of spring spawners across the time series (6.23 years (95% CI: 5.78–6.85 years)) was approximately 1 year lower than that of fall spawners (7.52 years (6.82–8.34 years)). Overall, the findings of this study can be used to better inform stock assessments and rebuilding plans for 4TVn spring and fall spawning Atlantic herring and highlight the importance of examining temporal trends in growth and generation time for more effective management of fish stocks. [ABSTRACT FROM AUTHOR]

Fisheries management needs to ensure that resources are exploited sustainably, and the risk of depletion is at an acceptable level. However, often uncertainty about resource dynamics exists, and data availability may differ substantially between fish stocks. This situation can be addressed through tiered systems, where tiers represent different data limitations, and tier‐specific stock assessment methods are defined, aiming for risk equivalence across tiers. As case studies, we selected stocks of European plaice, Atlantic cod and Atlantic herring, where advice is provided by the International Council for the Exploration of the Sea (ICES). We conducted a closed‐loop simulation to compare risk equivalence between the data‐rich ICES MSY rule, based on a quantitative stock assessment, and the revised data‐limited empirical management procedures of the ICES advice framework. The simulations indicated that the data‐limited approaches were precautionary and did not lead to a higher risk of depletion than the data‐rich approach. Although the catch based on generic data‐limited approaches was lower, stock‐specific optimisation improved management performance with catch levels comparable with the data‐rich approach. Furthermore, the simulation indicated the ICES MSY rule can fail to meet management objectives due to increased depletion risk when management reference points are set suboptimally. We conclude that the recent revisions of the ICES system explicitly account for risk equivalence for data‐limited fisheries management and are a major step forward. Finally, we advocate further consideration of simple empirical management procedures irrespective of data limitations due to their ability to meet fisheries management objectives with greater simplicity. [ABSTRACT FROM AUTHOR]

We developed and validated a mixed-stock analysis (MSA) method with 59 single-nucleotide polymorphisms selected from genome-wide data to assign individuals to populations in mixed-stock samples of Atlantic herring from the North and Baltic seas. We analysed 3734 herring from spawning locations and scientific catches of mixed feeding stocks to demonstrate a "one-fits-all" tool with unprecedented accuracy for monitoring spatio-temporal dynamics throughout a large geographical range with complex stock mixing. We re-analysed time-series data (2002–2021) and compared inferences about stock composition with estimates from morphological data. We show that contributions from the western Baltic spring-spawning stock complex, which is under management concern, have likely been overestimated. We also show that a genetically distinctive population of western Baltic autumn spawners, ascribed low fisheries importance, contributes non-negligible and potentially temporally increasing proportions to mixed-stock aggregations, calling for a re-evaluation of stock definitions. MSA data can be implemented in stock assessment and in a variety of applications, including marine ecosystem description, impact assessment of specific fleets, and stock-rebuilding plans. [ABSTRACT FROM AUTHOR]

Understanding the drivers behind fluctuations in fish populations remains a key objective in fishery science. Our predictive capacity to explain these fluctuations is still relatively low, due to the amalgam of interacting bottom-up and top-down factors, which vary across time and space among and within populations. Gaining a mechanistic understanding of these recruitment drivers requires a holistic approach, combining field, experimental and modelling efforts. Here, we use the Western Baltic Spring-Spawning (WBSS) herring (Clupea harengus) to exemplify the power of this holistic approach and the high complexity of the recruitment drivers (and their interactions). Since the early 2000s, low recruitment levels have promoted intense research on this stock. Our literature synthesis suggests that the major drivers are habitat compression of the spawning beds (due to eutrophication and coastal modification mainly) and warming, which indirectly leads to changes in spawning phenology, prey abundance and predation pressure. Other factors include increased intensity of extreme climate events and new predators in the system. Four main knowledge gaps were identified related to life-cycle migration and habitat use, population structure and demographics, life-stage specific impact of multi-stressors, and predator–prey interactions. Specific research topics within these areas are proposed, as well as the priority to support a sustainable management of the stock. Given that the Baltic Sea is severely impacted by warming, eutrophication and altered precipitation, WBSS herring could be a harbinger of potential effects of changing environmental drivers to the recruitment of small pelagic fishes in other coastal areas in the world. [ABSTRACT FROM AUTHOR]

Johan Hjort's "critical period" hypothesis, which postulates that year‐class strength is determined in the short period following the onset of exogenous feeding, has rarely been supported by empirical data. Instead, the current understanding is that recruitment is determined by cumulative mortality throughout early life. Recent studies relied on the measure of growth autocorrelation derived from otolith daily increment widths to test the link between growth rate achieved during the post‐hatch period and during subsequent phases of the larval stage. Based on this approach, we revisit the role of larval growth in driving survival potential in three clupeoid species: Japanese sardine Sardinops melanostictus, Japanese anchovy Engraulis japonicus, and Pacific round herring Etrumeus micropus throughout the larval stage, using a combination of published datasets of otolith increment widths. Strong growth autocorrelation was detected for all three species throughout the larval stage, suggesting that initial growth determines to some extent growth rates achieved later in life. The extent of autocorrelation was reduced in sardine relative to anchovy and round herring at older ages. This interspecific difference could be attributed to differences in sensitivity to variability of environmental factors such as water temperature and food availability. The present findings suggest that the effect of early growth rate persists into later life stages for driving survival potential, which could reconcile the classic concept of "critical period" and the current "growth–survival" paradigm. [ABSTRACT FROM AUTHOR]

Recruitment is a critical component of population dynamics and variability in recruitment underpins large fluctuations in population abundances of commercially valuable marine fishes. Marine pelagic fishes such as Atlantic herring (Clupea harengus) experience relatively high variability in recruitment that is driven by a wide range of biotic and abiotic factors. The relative importance and interaction of each factor for determining recruitment is poorly understood, and consequently, recruitment estimates are one of the largest uncertainties in fisheries management and predictions of future population sizes. Poor recruitment of Atlantic herring has been identified as a major issue and bottleneck for the species; therefore, factors influencing successful recruitment are of great interest to fisheries managers. Here we review studies that have examined the factors influencing survival at the egg stage, early larval stage, late larval stage, and juvenile stage to develop a more comprehensive understanding of the recruitment of Atlantic herring and provide recommendations to guide future research. We identified nine biotic and eight abiotic factors that have been found to substantially impact the recruitment of Atlantic herring, with temperature, prey availability, and predation being the most commonly investigated factors. We conclude it is not one factor that primarily determines recruitment, but rather a collection of many factors that vary temporally and spatially that drive the large variation observed in Atlantic herring recruitment year over year. A holistic approach is required to better understand recruitment and improve fisheries management decisions regarding Atlantic herring. [ABSTRACT FROM AUTHOR]

Fisheries are important sources of nutrients for people, but fisheries science and management do not consider nutrient information. The result is that fisheries are conducted without knowledge of how exploited species portfolios produce nutrients, how these yields have changed over time, and how they may change in the future. Here, we develop approaches for nutrient-informed analysis, and illustrate their use by applying them to catches from northwest Atlantic fisheries from 1950 to 2014. Relative to catch weights, nutrient yields showed more change over time and greater degrees of concentration in fewer taxa. Species that were minor from a weight perspective were identified as key sources of specific nutrients. Atlantic herring (Clupea harengus) emerge as a cornerstone of regional nutrient yields, with recent yields of some nutrients so disproportionately reliant upon herring as to indicate a potential lack of resilience. Insights such as these emphasize the need for nutrient informed approaches to fisheries assessment. [ABSTRACT FROM AUTHOR]

Anadromous river herring (alewife and blueback herring) persist at historically low abundances and are caught as bycatch in commercial fisheries, potentially preventing recovery despite conservation efforts. We used newly established single-nucleotide polymorphism genetic baselines for alewife and blueback herring to define fine-scale reporting groups for each species. We then determined the occurrence of fish from these reporting groups in bycatch samples from a Northwest Atlantic fishery over four years. Within sampled bycatch events, the highest proportions of alewife were from the Block Island (34%) and Long Island Sound (22%) reporting groups, while for blueback herring the highest proportions were from the Mid-Atlantic (47%) and Northern New England (24%) reporting groups. We then quantified stock-specific mortality in a focal geographic area (∼3500 km2, including Block Island Sound) of high bycatch incidence and sampling effort, where the most accurate estimates of mortality could be made. During this period, we estimate that bycatch took about 4.6 million alewife and 1.2 million blueback herring, highlighting the need to reduce bycatch mortality for the most depleted river herring stocks. [ABSTRACT FROM AUTHOR]