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Introduction: Like in many parts of the world, the Baltic Sea experiences a multitude of processes and stressors that influence fish stock dynamics. This paper compartmentalizes 250 publications that examine the cumulative effects and trade-offs of some of the most significant environmental drivers (temperature change, hypoxia, nutrient enrichment, acidification, low salinity, and food-web dynamics) on the ecology of top commercial fish species in the Baltic Sea (cod, sprat, whiting, herring, flounder, and plaice). Methods: A systematic review method was applied to ensure rigorous coverage of existing literature and to provide a comprehensive synthesis of the current knowledge on the subject. Results: The results illustrate the extent of scientific research applicable to commercial fisheries knowledge in the Baltic Sea and identify which pressures have the greatest negative impacts on which stocks. Additionally, the findings demonstrate how well top commercial fish species have adapted to the changing environmental conditions of the Baltic Sea. In doing so, the review illustrates the upcoming challenges and underscores which stocks are likely to dominate in the future and which will face difficulties. Discussion: By considering ecosystem-based fisheries management, this paper emphasizes the need to account for complex ecosystem interactions beyond single-stock monitoring. With increased natural hazards, top commercial fish species have reacted differently, depending on the region and their adaptive capabilities. In most cases, Clupeidae species have adapted the best to their new surroundings, Pleuronectidae resilience is varied, while Gadidae species are finding the Baltic Sea increasingly challenging. [ABSTRACT FROM AUTHOR]

Policies aiming to restore ecosystems, achieve thriving fisheries and reverse biodiversity loss require knowledge of their former status and long‐term variation. As quantitative fish data is typically only available for recent decades long after changes may have occurred, a greater use of qualitative sources has been encouraged in marine historical ecology. We examined diverse historical information (including maritime history, fisheries reports, naturalists' accounts, recipes, nautical charts and newspapers) across a multi‐century time span (13th–20th century) for a wide range of species to document their long‐term trajectories in an understudied Northeast Atlantic ecosystem (Irish Sea coast of Wales). We find strong evidence of the loss of both a pelagic fishery for herring, which was of fundamental socio‐ecological importance since at least the 13th century, and the loss of significant multi‐species demersal and intertidal fisheries. Local, commercial and/or functional extinction has occurred for taxa spanning a wide range of diversity (crustacean, elasmobranchs, sturgeon, and teleosts), body size and ecological role, suggesting far‐reaching changes to food webs. This raises fundamental questions about the present‐day health and integrity of this coastal ecosystem and the long‐term viability of current fisheries which depend on a few shellfish species. Our century‐scale synthesis of qualitative data for multiple taxa allows the collective breadth of losses to be fully appreciated and may reduce the risk of 'shifting baselines'. Restoration to historical baselines may not be achievable, but our findings provide evidence of long‐term change relevant to policies for recovery, and prevention of further decline of fishes, fisheries and ecosystems. [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]

IntroductionLike in many parts of the world, the Baltic Sea experiences a multitude of processes and stressors that influence fish stock dynamics. This paper compartmentalizes 250 publications that examine the cumulative effects and trade-offs of some of the most significant environmental drivers (temperature change, hypoxia, nutrient enrichment, acidification, low salinity, and food-web dynamics) on the ecology of top commercial fish species in the Baltic Sea (cod, sprat, whiting, herring, flounder, and plaice).MethodsA systematic review method was applied to ensure rigorous coverage of existing literature and to provide a comprehensive synthesis of the current knowledge on the subject.ResultsThe results illustrate the extent of scientific research applicable to commercial fisheries knowledge in the Baltic Sea and identify which pressures have the greatest negative impacts on which stocks. Additionally, the findings demonstrate how well top commercial fish species have adapted to the changing environmental conditions of the Baltic Sea. In doing so, the review illustrates the upcoming challenges and underscores which stocks are likely to dominate in the future and which will face difficulties.DiscussionBy considering ecosystem-based fisheries management, this paper emphasizes the need to account for complex ecosystem interactions beyond single-stock monitoring. With increased natural hazards, top commercial fish species have reacted differently, depending on the region and their adaptive capabilities. In most cases, Clupeidae species have adapted the best to their new surroundings, Pleuronectidae resilience is varied, while Gadidae species are finding the Baltic Sea increasingly challenging.

Norwegian killer whales (Orcinus orca) are thought to be generalists that feed primarily on fish, but some individuals have been observed targeting pinnipeds. In the study reported here, field observations of foraging behaviours formed the basis of a priori classification as either seal-eaters or fish-eaters. Concurrent collection of photographic identification and biopsies for stable isotope analysis were used to validate prey choice classification. We found through satellite tracking that whales classified as seal-eaters took different paths south after leaving the northern fjords seemingly optimized for pinniped predation. Specifically, we found that seal-eaters took paths that tightly followed the coastline, remaining on average 6.9 ± 10.7 km (mean ± SD, n = 315) from the coast, whereas fish-eaters moved offshore along the continental shelf, travelling on average 45.1 ± 30.2 km (n = 1534) from the coast. We also found that, compared to fish-eaters, seal-eaters displayed more movements directed towards harbour seal haul-outs (p = 0.001). As expected, our data suggest that the fish-eaters feed primarily on fish, whilst seal-eaters appear to opportunistically use diverse foraging strategies optimized for either fish or seals based on availability and preference. Our findings demonstrate that tracking data can elucidate Norwegian killer whale movements associated with different prey types and selection.

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Smoked fish roes within cold smoked herring are considered a very popular ready-to-eat food in Egypt. Therefore, the microbial quality of fish roes should be of concern. The purposes of this study were to conduct bacterial analysis and the possibility of detection of foodborne pathogens. With limited application of dry heating at 85°C for 1 and 5 minutes to improve the safety of roes. To study the biogenic amines (BA) including spermine, putrescine, cadaverine, histamine, tyramine, and spermidine in fresh, heated at 85°C for 5 min, and stored at 0°C for 6 months smoked roes. Vibrio spp. including Vibrio vulnificus, Vibrio furnissii, and Vibrio carcbariae were found in 5 samples (9.6%). One Salmonella spp. (1.9%) and one Listeria monocytogenes (1.9%), 4 Staphylococcus aureus (7.7%), and 3 Bacillus cereus (5.8%) pathogens. While Clostridium botulinum (vegetative forms) was not detected. None of the aerobic, anaerobic, or selective bacterial counts existed after heating smoked roes at 85°C for 5 minutes. The average of each BA in all samples was below 3mg/100g, which is less than the 5.0 mg/100g acceptable limit recommended by the US Food and Drug Administration. Histamine and tyramine only appeared after cold storage of roes at 0°C for 6 months. Cold smoked herring roe was low in acidity (pH: 5.92), high in moisture (68.5%), protein (61.37%), and lipid content (28.7%), thus it could support the bacteria growth. Additional measures are needed to reduce the possible health risks for fish roe consumers. [ABSTRACT FROM AUTHOR]

The spatial distribution of the Pacific herring Clupea pallasii in the Sea of Okhotsk waters at the northeastern coast of Sakhalin Island is described on the basis of data of the surveys using bottom and midwater trawls and a Danish seine conducted in June–October 1989 and 1997–2020. Herring are distributed widely, with the main aggregations forming in the area with depths of less than 100 m between Lunsky Bay and Piltun Bay, where herring of the North-East Sakhalin population feed. Herring in deeper waters presumably belong to the Okhotsk population. [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]

Two specimens of Baltic herring Clupea harengus membras with anatomically different signs of synchronous hermaphroditism, discovered for the first time in the eastern part of the Gulf of Finland, are described. Individuals with abnormal gonads did not differ from ordinary representatives of the species in other biological characteristics and external morphology. Possible causes of disturbances in the reproductive functions of herring in the studied region are discussed. [ABSTRACT FROM AUTHOR]

Spatial distribution of pacific herring Clupea pallasii in the Okhotsk Sea waters at the northeastern coast of Sakhalin Island is described on the data of surveys conducted in June-October of 1989 and 1997-2020 using bottom and midwater trawls and Danish seine. The herring distribute widely, with the main aggregations in the area with depth up to 100 m between the Lunsky Bay and Piltun Bay. These aggregations are formed by the native herring of the North-East Sakhalin population, whereas the herring in the deeper waters belong to the Okhotsk population.

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.

The temperature has a significant effect on cathepsin activity, but the effect of temperature on the ripening of marinades, and the formation of protein hydrolysis products, is less studied than other technological factors. The results of this study showed that herring marinated at 2 °C showed a higher mass yield, but lower non-protein nitrogen (NPN), peptides, and free amino acid fraction content, than after marinating at 7 and 12 °C. The higher temperature increased the free amino acid content the most, and decreased the hardness, as measured via sensory assessment, of the marinated meat. This was confirmed by the hardness measurement in the texture profile analysis. The highest activity of cathepsins D and B in the meat was found at 7 °C, while cathepsin L was found at 2 °C. Increasing the temperature by 10 °C increased the diffusion/loss of nitrogenous substances from the meat to the brine by 36%. The meat and brine showed high antioxidant activity, which depended on the marinating temperature, and originated mainly from the 5–10 or <5 kDa fraction. The meat had a higher ABTS (2,2′-azinobis-3-ethylbenzothiazoline-6-sulfonate) activity than the brine, opposite to the DPPH (2,2-diphenyl-1-picrylhydrazyl radical) activity, while the FRAP (Ferric Reducing Antioxidant Power) capacity was similar for meat and brine. The fractionation of the meat and brine extracts increased the antioxidant potential of FRAP and ABTS only for the brine. The most hydrophobic peptides were released during marinating at 7 °C. The meat and brine were dominated by 2–4 kDa peptides, followed by 4–6 and 0.5–2 kDa. The higher temperature favored a higher proportion of <4 kDa than >4 kDa peptides in the brine. [ABSTRACT FROM AUTHOR]

North American bird populations have declined significantly since 1970 due to a variety of causes. We estimated long term changes in abundance of wintering waterbirds at Tomales Bay, Marin Co., CA, from 1992-2022. Average total waterbird numbers decreased 11.8%. The most concerning declines for taxa whose numbers in 1992 accounted for at least 5% of the combined numbers of waterbirds were for Surf Scoter (Melanitta perspicillata), Brant (Branta bernicla), Ruddy Duck (Oxyura jamaicensis), American Coot (Fulica americana), and Western (Aechmophorus occidentalis) and Clark's (Aechmophorus clarkii) Grebe. Of 29 taxa that we estimated trends for, 13 declined across our study period. Fourteen taxa had negative trends of ≥2% year–1 for at least 10 consecutive years, meeting the IUCN's Red List criteria for Near Threatened or higher. We accounted for two influencers of primary productivity in the bay: the Northern California Multivariate Oceanic and Climatic (MOCI) index and winter freshwater inflow. MOCI was included in the best model for six taxa while freshwater inflow was informative for eight taxa. A local wetland restoration project led to increases in three of the seven species we modeled. The dynamics of waterbird numbers on Tomales Bay are linked partly to herring but other local to global factors are important. [ABSTRACT FROM AUTHOR]

Global warming has a complex impact on the Scottish fishery. This research studies this impact using reported data and proposes appropriate solutions to minimise its impact. First, climate models are used to predict temperature changes over the next 50 years based on past data; from the known living temperatures for fish such as mackerel and herring, their future migration routes are predicted. Researchers note that this model is probably overly conservative, and our predictions should be considered a best-case scenario: the impact of climate change will be worse if, as expected, the pace of climate change continues to accelerate. Second, building a model to determine when fishery vessels will no longer be able to locate fish under different circumstances. Third, building economic models to determine the relationships between profits, the distances fishery vessels must travel and project these to the future. This research projects that small Scottish fishing companies will go bankrupt during the next 50 years if they do not change their business strategy.

Alginate/pectin films supplemented with extracts from cranberry pomace (CE) or grape seeds (GE) were developed and applied to herring fillets that were stored for 18 days at 4 °C. Herring coated with films containing GE and CE inhibited the growth of Listeria monocytogenes and Pseudomonas aeruginosa during the storage period, whereas pure alginate/pectin films did not show an antimicrobial effect against the tested pathogens. The application of alginate/pectin films with CE and GE minimised pH changes and inhibited total volatile basic nitrogen (TVN) and the formation of thiobarbituric acid-reactive substances (TBARS) in the herring fillets. The coating of herring fillets with films with CE or GE resulted in three- and six-fold lower histamine formation and one-and-a-half- and two-fold lower cadaverine formation, respectively, when compared to unwrapped herring samples after 18 days of storage. The incorporation of 5% extracts isolated from cranberry pomace or grape seeds into the alginate/pectin film hindered herring spoilage due to the antimicrobial and antioxidant activity of the extracts. [ABSTRACT FROM AUTHOR]

Managing social–ecological systems that benefit both humans and nature is the central challenge of natural resource management. Integrating multiple perspectives into decision-making adds flexibility to social–ecological systems by reducing rigidity and promoting adaptability. Our objective was to assess expert perceptions of the structure, content, and function of the Puget Sound stormwater social–ecological system. We interviewed Puget Sound stormwater experts to document their mental models of the system and compared the network structure of expert maps. We also assessed differences among experts in the components of the social–ecological system which were included in mental models. Our analyses revealed differences between genders, as well as between managers, in how experts characterized the system. Notably, female participants tended to characterize the social–ecological system as one in which there were many system drivers generating multiple impacts across the system. The mental models of the scientists tended to include more resource units than those of the managers, which focused more on governance compared to those of the scientists. Finally, we incorporated the diverse input from mangers and scientists to create a single mental model to represent a consensus on the Puget Sound stormwater social–ecological system. This work highlights the fact that addressing the stormwater problem requires that we embrace the varied perspectives of scientists, managers, and stakeholders. We contend that incorporating the diverse perspectives of experts within the context of social–ecological systems provides a promising path towards a lasting and durable recovery for the ecosystem. [ABSTRACT FROM AUTHOR]

Atlantic herring (Clupea harengus) has a complex population structure and displays a variety of reproductive strategies. Differences in reproductive strategies among herring populations are linked to their time of spawning, as well as to their reproductive investment which can be an indicator for migratory vs. stationary behavior. These differences are reflected in the number of oocytes (fecundity) and the size of the oocytes prior spawning. We studied potential mixing of herring with different reproductive strategies during the spring spawning season on a coastal spawning ground. It has been hypothesized that both spring and autumn spawning herring co-occur on this specific spawning ground. Therefore, we investigated the reproductive traits oocyte size, fecundity, fertilization success as well as length of the hatching larvae during the spring spawning season from February to April. We used a set of 11 single nucleotide polymorphism markers (SNPs), which are associated with spawning season, to genetically identify autumn and spring spawning herring. Reproductive traits were investigated separately within these genetically distinct spawning types. Furthermore, we used multivariate analyses to identify groups with potentially different reproductive strategies within the genetic spring spawners. Our results indicate that mixing between ripe spring and autumn spawners occurs on the spawning ground during spring, with ripe autumn spawners being generally smaller but having larger oocytes than spring spawners. Within spring spawners, we found large variability in reproductive traits. A following multivariate cluster analysis indicated two groups with different reproductive investment. Comparisons with other herring populations along the Norwegian coastline suggest that the high variability can be explained by the co-occurrence of groups with different reproductive investments potentially resulting from stationary or migratory behavior. Fertilization success and the length of the hatching larvae decreased with progression of the spawning season, with strong inter-individual variation, supporting our findings. Incorporating such complex population dynamics into management strategies of this species will be essential to build its future population resilience.

Ocean Acoustic Waveguide Remote Sensing (OAWRS) enables fish population density distributions to be instantaneously quantified and continuously monitored over wide areas. Returns from seafloor geology can also be received as background or clutter by OAWRS when insufficient fish populations are present in any region. Given the large spatial regions that fish inhabit and roam over, it is important to develop automatic methods for determining whether fish are present at any pixel in an OAWRS image so that their population distributions, migrations and behaviour can be efficiently analyzed and monitored in large data sets. Here, a statistically optimal automated approach for distinguishing fish from seafloor geology in OAWRS imagery is demonstrated with Neyman–Pearson hypothesis testing which provides the highest true-positive classification rate for a given false-positive rate. Multispectral OAWRS images of large herring shoals during spawning migration to Georges Bank are analyzed. Automated Neyman-Pearson hypothesis testing is shown to accurately distinguish fish from seafloor geology through their differing spectral responses at any space and time pixel in OAWRS imagery. These spectral differences are most dramatic in the vicinity of swimbladder resonances of the fish probed by OAWRS. When such significantly different spectral dependencies exist between fish and geologic scattering, the approach presented provides an instantaneous, reliable and statistically optimal means of automatically distinguishing fish from seafloor geology at any spatial pixel in wide-area OAWRS images. Employing Kullback–Leibler divergence or the relative entropy in bits from Information Theory is shown to also enable automatic discrimination of fish from seafloor by their distinct statistical scattering properties across sensing frequency, but without the statistical optimal properties of the Neyman–Pearson approach. [ABSTRACT FROM AUTHOR]

This study formulates a qualitative image-based approach to establishing cetacean sightings' effort at an ecosystem scale in the Gulf of Maine. As a first step, I investigate a rare set of long-term sightings (2008–2017, the study period) of a male killer whale (Orcinus orca) representing unusually consistent occurrences, without considering observation effort. Largely unknown, killer whale populations in the NW Atlantic are tiny, travelling over vast areas, and at risk of human-caused extinction. The synthesis uses opportunistic observations, reported mainly by recreational mariners and commercial fishers incorporated into data manipulations anonymously. Adding an effort index using the qualitative image-based approach, I then investigate the hypothesis that the killer whale sightings constitute seasonal-spatial fidelity to the greater GoM, the first documentation of fidelity patterns in the western Atlantic hemisphere. The analysis includes comparisons to frequency distributions of single killer whales in the gulf in the historical past as a baseline, i.e. post mid 1940s. Finally, the fidelity analysis reveals a substantial spatial anomaly in the recent sightings data for the northeastern GoM. An explanation for the emergent anomaly is pursued by analyses of indicators of the availability of Atlantic herring (Clupea harengus) [fisheries landings, Atlantic puffin (Fratercula arctica) chick diets] as potential prey in the NE gulf. With the development of complementary corroborative approaches to the analysis of incidental sightings, it is possible to chip away at impediments to the understanding of ecosystem attractants and deterrents with respect to cetacean distributions. [ABSTRACT FROM AUTHOR]

Based on research 1995–2020, abundant and potentially commercial fish in Russian watersof the Chukchi Sea have been identified. In total, 72 species were recorded in trawl catches, 16 species from six families were abundant, among which smelts (Osmeridae), salmons (Salmonidae), and herrings (Clupeidae) accounted for an average of 1.5, 0.2, and 0.1% of the total commercial marine fish biomass, respectively. For the species of the analyzed families, the size-age and weight characteristics, features of linear and weight growth, timing, scale and conditions of spawning were considered. The biological indicators of fish from the Chukchi and Bering seas and other water bodies were compared. Saffron cod Eleginus gracilis, Arctic rainbow smelt Osmerus mordax dentex, Pacific cod Gadus macrocephalus, Greenland halibut Reinhardtius hippoglossoides, and some species of sculpins were represented mainly by juveniles and immature individuals, older fish appeared in climatically warm years. Walleye pollock Gadus chalcogrammus, Pacific salmons, Alaska plaice Pleuronectes quadrituberculatus, and starry flounder Platichthys stellatus were characterized by the presence of older individuals. In polar cod Boreogadus saida, Bering flounder Hippoglossoides robustus, yellowfin sole Limanda aspera, Sakhalin sole L. sakhalinensis, longhead dab L. proboscidea, Pacific herring Clupea pallasii, Pacific capelin Mallotus villosus catervarius, and warty sculpin Myoxocephalus verrucosus smaller body sizes were recorded for the specimens caught at the Chukchi Sea shelf comparing to those from the Bering Sea. [ABSTRACT FROM AUTHOR]

Aim: The latitudinal diversity gradient of increasing species richness from poles to equator is one of the most striking and pervasive spatial patterns of biodiversity. Climate appears to have been key to the formation of the latitudinal diversity gradient, but the processes through which climate shaped species richness remain unclear. We tested predictions of the time for speciation, carrying capacity and diversification rate latitudinal diversity gradient hypotheses in a trans‐marine/freshwater clade of fishes. Location: Global in marine and freshwater environments. Taxon: Clupeiformes (anchovies, herrings, sardines and relatives). Methods: We tested predictions of latitudinal diversity gradient hypotheses using a molecular phylogeny, species distribution data and phylogenetic comparative approaches. To test the time for speciation hypothesis, we conducted ancestral state reconstructions to infer the ages of temperate, subtropical and tropical lineages and frequency of evolutionary transitions between climates. We tested the carry capacity hypothesis by characterizing changes in net diversification rates through time. To test the diversification rate hypothesis, we qualitatively compared the diversification rates of temperate, subtropical and tropical lineages and conducted statistical tests for associations between latitude and diversification rates. Results: We identified four transitions to temperate climates and two transitions out of temperate climates. We found no differences in diversification rates among temperate and tropical clupeiforms. Net diversification rates remained positive in crown Clupeiformes since their origin ~150 Ma in both tropical and temperate lineages. Climate niche characters exhibited strong phylogenetic signal. All temperate clupeiform lineages arose <50 Ma, after the Early Eocene Climatic Optimum. Main conclusions: Our results support the time for speciation hypothesis, which proposes that climate niche conservatism and fluctuations in the extent of temperate climates limited the time for species to accumulate in temperate climates, resulting in the latitudinal diversity gradient. We found no support for the carrying capacity or diversification rate hypotheses. [ABSTRACT FROM AUTHOR]

The low-technological quality of herring caught during the feeding season makes it impossible to achieve full ripeness of the meat in marinades. One solution may be to assist ripening using herring digestive tract proteases. Therefore, whole herring, headed herring and fillets were marinated for 2–14 days using the German (direct) and Danish (pre-salted) methods. The results showed that the mass of marinades from fillets was lower than from herring with intestines and correlated strongly with salt concentration in the Danish method, in contrast to the German method. Marinades from whole and headed herring had significantly higher trypsin, chymotrypsin, carboxypeptidase-A and cathepsin activities than marinated fillets. The herring marinated with viscera had 2–3 times higher non-protein nitrogen, peptide and amino acid fractions, as well as ripened 3 days faster than the marinated fillets. After 2 weeks of marinating, the fillets did not achieve full ripeness of the meat, unlike marinades made from whole and headed herring. The pre-salting stage in the Danish method significantly reduced cathepsin D activity by the tenth day of marinating, which was compensated by digestive proteases only in the case of whole or headed herring. The digestive proteases activity in the fillets was too low to achieve the same effect. Sensory evaluation of texture and hardness-TPA correlated strongly with several proteases in whole herring marinades, in contrast to a weak correlation with only one protease when marinating fillets. Marinating with intestines makes it possible to produce marinades faster, more efficiently and with higher sensory quality from herring of low-technological quality. [ABSTRACT FROM AUTHOR]

Abstract Both the Norwegian Spring Spawning herring (Clupea harengus) and the Northeast Arctic (NEA) cod (Gadus morhua) are examples of strong stock reduction and decline of the associated fisheries due to overfishing followed by a recovery. Cod and herring are both part of the Barents Sea ecosystem, which has experienced major warming events in the early (1920–1940) and late 20th century. While the collapse or near collapse of these stocks seems to be linked to an instability created by overfishing and climate, the difference of population dynamics before and after is not fully understood. In particular, it is unclear how the changes in population dynamics before and after the collapses are associated with biotic interactions. The combination of the availability of unique long‐term time series for herring and cod makes it a well‐suited study system to investigate the effects of collapse. We examine how species interactions may differently affect the herring and cod population dynamic before and after a collapse. Particularly we explore, using a GAM modeling approach, how herring could affect cod and vice versa. We found that the effect of cod biomass on herring that was generally positive (i.e., covariation) but the effect became negative after the collapse (i.e., predation or competition). Likewise a change occurred for the cod, the juvenile herring biomass that had no effect before the collapse had a negative effect after. Our results indicate that the population collapses may alter the inter‐specific interactions and response to abiotic environmental changes. While the stocks are at similar abundance levels before and after the collapses, the system is potentially different in its functioning and may require different management action.

Comparative analysis of cetacean and fish species distribution in the Barents Sea is conducted on the data of joint Russian-Norwegian ecosystem surveys in August-October of 2005–2014. The number of observed minke whale (Balaenoptera acutorostrata), humpback whale (Megaptera novaeangliae), fin whale (Balaenoptera physalus), white-beaked dolphin (Lagenorhynchus albirostris), and harbor porpoise (Phocoena phocoena), as well as the acousticmeasured distribution density of fishes, as capelin (Mallotus villosus), polar cod (Boreogadus saida), herring (Clupea sp.), cod (Gadus morhua), haddock (Melanogrammus aeglefinus), saithe (Pollachius virens), blue whiting (Micromesistius poutassoumes), redfish (Sebastes sp.), norway pout (Trisopterus esmarkii), and fish fingerlings are summarized by the squares 50 x 50 km and maps of their distribution are drawn. A degree of overlapping between distributions of cetacean and fish species is estimated for each pair of species, as ratio of number of the squares where the species were presented together to total number of the squares where the species were found. Associations between cetaceans and their potential prey are determined by the methods of principal components and correlation analysis applied to the log-transformed data. Distribution of the widely distributed cetaceans, as minke whale and white-beaked dolphin, overlapped largely (up to 42 %) with many of studied fish species, therefore their possible predation on these species was significant. On the contrary, locally distributed cetaceans, such as harbor porpoise, had possibly lesser impact on fish because of low overlapping with their distribution (< 11 %). By the results of correlation analysis, capelin and polar cod were the priority potential prey for baleen whales (p < 0.01 and p = 0.02, respectively), whereas cod, haddock, blue whiting, and redfish – for toothed whales (p = 0.02, 0.01, 0.02, and < 0.01, respectively), in particular for white-beaked dolphin.

In this study, ensilaging of herring (Clupea harengus) filleting co-products was taken from lab-scale to pilot scale (1500 L) while monitoring the protein degree of hydrolysis (DH) and lipid oxidation. Subsequently, the possibility of recovering fish oil and protein hydrolysates using batch centrifugation at different g-forces/times was investigated. Around 38% DH was recorded after 2-day pilot-scale ensilaging of herring co-products at ambient temperature (i.e., ~ 22 °C), which was similar to the DH found in lab-scale (40% after 2 days; 22 °C). The lipid oxidation marker 2-thiobarbituric acid reactive substances (TBARS) reached 20 µmole TBARS/kg silage after 2-day ensilaging. Centrifugation of the silage at 3000–8500 × g for 2–20 min revealed successful separation into fish oil and protein hydrolysates. Heat-treating the silage (85 °C; 30 min) prior to centrifugation resulted in significantly higher oil and hydrolysates recoveries; the same being true for increased g-force. At 8500 × g, the recovery of oil and hydrolysates were 9.7 and 53.0% w/w, respectively, from heat-treated silage, while recoveries were 4.1 and 48.1% w/w, respectively, from non-heat treated silage. At 4500 × g, being a more scalable approach, corresponding numbers were 8.2 and 47.1% (w/w) as well as 2.0 and 40.2% (w/w). The recovered fish oil contained 8% EPA and 11% DHA of total fatty acids. Free fatty acids (FFA), peroxide value (PV), p-anisidine value (p-AV), and total oxidation (TOTOX) values of oils were in the range of 4–7% (FFA), 3.6–3.7 meq/kg oil (PV), 2.5–4.0 (p-AV), and 9.9–11.1 (TOTOX), respectively, which were within the acceptable limits for human consumption specified by the GOED voluntary monograph. The recovered protein hydrolysates contained peptides in the molecular weight range 0.3–6 kDa (~ 37%) and 11–34 kDa (~ 63%). Also, the remaining solids contained 15–17% (w/w) protein, having 44–45% essential amino acids. Overall, the results suggest that herring co-product silage is a valuable source of fish oil and protein hydrolysates, paving the way for ensilaging based-biorefining of herring co-products into multiple products. [ABSTRACT FROM AUTHOR]

Climate change and deoxygenation are affecting fish stocks on a global scale, but disentangling the impacts of these stressors from the effects of overfishing is a challenge. This study was conducted to distinguish between climate change and mismanagement as possible causes for the drastic decline in spawning stock size and reproductive success in cod (Gadus morhua) and herring (Clupea harengus) in the Western Baltic Sea, when compared with the good or satisfactory status and reproductive success of the other commercial species in the area. Available data on water temperature, wind speed, and plankton bloom during the spawning season did not reveal conclusive correlations between years with good and bad reproductive success of cod or herring. Notably, the other commercial species in the area have very similar life history traits suggesting similar resilience against stress caused by climate change or fishing. The study concludes that severe, sustained overfishing plus inappropriate size selectivity of the main fishing gears have caused the decline in spawning stock biomass of cod and herring to levels that are known to have a high probability of impaired reproductive success. It is pointed out that allowed catches were regulated by management and adhered to by the fishers, meaning that unregulated fishing did not occur. Thus, mismanagement (quotas that were too high and gears that selected too small sizes) and not climate change appears to be the primary cause of the bad status of cod and herring in the Western Baltic Sea. [ABSTRACT FROM AUTHOR]

The temperature has a significant effect on cathepsin activity, but the effect of temperature on the ripening of marinades, and the formation of protein hydrolysis products, is less studied than other technological factors. The results of this study showed that herring marinated at 2 °C showed a higher mass yield, but lower non-protein nitrogen (NPN), peptides, and free amino acid fraction content, than after marinating at 7 and 12 °C. The higher temperature increased the free amino acid content the most, and decreased the hardness, as measured via sensory assessment, of the marinated meat. This was confirmed by the hardness measurement in the texture profile analysis. The highest activity of cathepsins D and B in the meat was found at 7 °C, while cathepsin L was found at 2 °C. Increasing the temperature by 10 °C increased the diffusion/loss of nitrogenous substances from the meat to the brine by 36%. The meat and brine showed high antioxidant activity, which depended on the marinating temperature, and originated mainly from the 5–10 or 4 kDa peptides in the brine.

Finnish fisheries are regulated first and foremost by the EU Common Fisheries Policy (CFP) and quotas determined by the EU. Certain fisheries have also been certified according to the international Marine Stewardship Council (MSC) standard. The aim of this article is to study the added value that the MSC brings to the governance of the ecological sustainability of Finnish marine fisheries. This is achieved by scrutinizing how the MSC addresses the ecosystem approach and how different experts and stakeholders see the role of the MSC in contributing to sustainable fisheries. We endeavor to unravel the sustainability benefits that non-state regulations can offer for a fishery in the Baltic Sea that is heavily regulated and controlled by the EU. We found that the MSC has led to some minor positive changes in fishing and that the indirect support the MSC provides when following scientific advice is even more important. [ABSTRACT FROM AUTHOR]

The collapse of the Norwegian spring spawning herring in the late 1960s is one of the most spectacular and well known fish stock collapses in the world. It is widely recognized that the collapse was due to a severe stock depletion in the wake of a sudden leap in technology, the consequences of which were not fully understood, together with open access exploitation by fleets from several nations. It took about twenty years for the stock to recover. We estimate a recruitment function for the herring stock from data beginning in the early 20th century, including the period of the collapse, and build a simulation model for the stock based on serially correlated random fluctuations around this recruitment function. In a deterministic model, fishing mortality rates in excess of 0.22 are not sustainable, but driving the stock to virtual extinction could be a matter of decades, for moderately excessive mortality rates. A rate of discount in excess of 23 percent could make such non-sustainable exploitation attractive, from an economic point of view, if the cost per unit of fish does not depend on the size of the stock. Random effects in recruitment can produce widely variable outcomes for the development of the stock, affecting the length of time it takes to deplete the stock to some reference level or its recovery from depletion. We investigate the effects of uncertainty in stock assessment, finding that it matters little, despite causing large variations in fishing mortality. [ABSTRACT FROM AUTHOR]

The development in the late eighteenth century of a successful herring fishing and curing industry based on Isleornsay on the Isle of Skye and its ultimate collapse one hundred years later is analysed. The start of this commercial venture coincided with the end of the tacksman system and the formation of crofts in the townships close by. The failure of the port is examined, focusing on a local petition for a grant from the Congested Districts Board to construct a deep-water pier to replace the inefficient tidal pier which dated from circa 1805.The petition is viewed in the context of the proposal to build a Light Railway from Isleornsay to Uig and Portree, thence by boat to the Outer Isles, a proposal that was little more than a pipe dream. The railway extensions to Kyle and Mallaig, both constructed to convey fish to the south and supported by Government funding, were expected to bring increased prosperity to the fishermen of the nearby localities but had a calamitous effect on the port of Isleornsay: local fishermen took their catches directly to the railhead and then the arrival of fish curers and trawlers from the East Coast, eager to profit from the new facilities, completed the ruin of a once profitable economy. [ABSTRACT FROM AUTHOR]

Acoustic surveys are the standard approach for evaluating many fish stocks around the world. The analysis of such survey data requires the accurate echo-classification of target species. This classification is often challenging as many organisms exhibit overlapping characteristics in terms of shape, acoustic amplitude, and behavior. In this study, a random forest approach was used to distinguish juvenile Pacific salmon (Oncorhynchus spp) from Pacific herring (Clupea pallasii) aggregations using the acoustic and morphological characteristics of their echo traces. The acoustic data was collected with an autonomous, multi-frequency echosounder deployed on the seafloor in the Discovery Islands, British Columbia from May to September 2015. The model was able to differentiate juvenile Pacific salmon from Pacific herring with a 98% accuracy. School depth and school mean volume backscattering strength were the most important predictors in determining the school classification. This study supports other publications suggesting that random forests represent a promising approach to acoustic target classification in fisheries science.

Demand for n-3 polyunsaturated fatty acids (n-3 PUFAs) exceeds supply. Large-scale studies on effects of season and geography of n-3 PUFAs in marine fish from the Northeast Atlantic Ocean (NEAO) may be used to optimize utilization and improve nutrition security. Using a sinusoid model, seasonal cycles of n-3 PUFAs were determined and found to be species-specific and clearly pronounced for the pelagic zooplankton feeding species. The Greenland halibut showed very little seasonal variation. The n-3 PUFA content in North Sea autumn-spawning (NSAS) herring peaked in summer, while Norwegian spring-spawning (NSS) herring and mackerel had their peak in autumn. A time shift of peaks in n-3 PUFAs between the two herring stocks was detected, likely due to different spawning strategies in addition to a delay of n-3 PUFAs flux in the northern regions of the NEAO. This study demonstrates that consideration of nutrient contents, such as n-3 PUFAs, when organizing and structuring fishery approaches may improve overall nutritional yield. Based on total annual Norwegian fish landings and seasonal variation in n-3 PUFA contents, n-3 PUFAs yield could theoretically be increased from 13.79 kilo ton per year from the current fishing tactics, to 15.54 if the pelagic species were only caught during the time of their seasonal n-3 PUFA peaks. Pelagic fish is a good source for dietary n-3 PUFAs, but harvest timing will also influence n-3 PUFAs intake by human consumers. One portion of fatty fish harvested during winter/spring may not meet the weekly intake reference nutritional guidelines for n-3 PUFAs. Marine n-3 PUFAs yields also varied geographically and decreased southwards, with the lowest values in Skagerrak. This study can serve as a model to understand patterns of reproductive cycles and geographical distribution of n-3 PUFAs in fatty fish from the NEAO and the novel approach may be useful to support sustainable, seasonal fishing programmes for optimization of n-3 PUFAs yields. [Display omitted] • Seasonal cycles of n-3 PUFAs were species-specific and pronounced for pelagic fish. • Catching pelagic fish at their n-3 PUFAs peaks may increase nutrient yields. • A weekly portion of fish caught in winter/spring may not provide sufficient n-3 PUFAs. • n-3 PUFAs in marine fish varied geographically and decreased southwards. [ABSTRACT FROM AUTHOR]

Alginate/pectin films supplemented with extracts from cranberry pomace (CE) or grape seeds (GE) were developed and applied to herring fillets that were stored for 18 days at 4 °C. Herring coated with films containing GE and CE inhibited the growth of Listeria monocytogenes and Pseudomonas aeruginosa during the storage period, whereas pure alginate/pectin films did not show an antimicrobial effect against the tested pathogens. The application of alginate/pectin films with CE and GE minimised pH changes and inhibited total volatile basic nitrogen (TVN) and the formation of thiobarbituric acid-reactive substances (TBARS) in the herring fillets. The coating of herring fillets with films with CE or GE resulted in three- and six-fold lower histamine formation and one-and-a-half- and two-fold lower cadaverine formation, respectively, when compared to unwrapped herring samples after 18 days of storage. The incorporation of 5% extracts isolated from cranberry pomace or grape seeds into the alginate/pectin film hindered herring spoilage due to the antimicrobial and antioxidant activity of the extracts.

Since 1960, landings of Atlantic herring have been the greatest of any marine species in Canada, surpassing Atlantic cod and accounting for 24% of the total seafood harvested in Atlantic Canada. The Scotian Shelf‐Bay of Fundy herring fisheries (NAFO Division 4VWX) is among Canada's oldest and drives this productivity, accounting for up to 75% of the total herring catch in some years. The stocks' productivity and overall health have declined since 1965. Despite management measures to promote recovery implemented since 2003, biomass remains low and is declining. The factors that drive the productivity of 4VWX herring are primarily unresolved, likely impeding the effectiveness of management actions on this stock. We evaluated potential drivers of herring variability by analyzing 52 time‐series that describe the temporal and spatial evolution of the 4VWX herring population and the physical, ecological, and anthropogenic factors that could affect them using structural equation models. Variation in herring biomass was best accounted for by the exploitation rate's negative effect and the geographic distribution of fishing and recruitment. Thermal phenology and temperature adversely and egg predation positively impacted the early life stage mortality rate and, ultimately, adult biomass. These findings are broadly relevant to fisheries management, but particularly for 4VWX herring, where the current management approach does not consider their early life stage dynamics or assess them within the ecosystem or climate change contexts. [ABSTRACT FROM AUTHOR]

Both the Norwegian Spring Spawning herring (Clupea harengus) and the Northeast Arctic (NEA) cod (Gadus morhua) are examples of strong stock reduction and decline of the associated fisheries due to overfishing followed by a recovery. Cod and herring are both part of the Barents Sea ecosystem, which has experienced major warming events in the early (1920–1940) and late 20th century. While the collapse or near collapse of these stocks seems to be linked to an instability created by overfishing and climate, the difference of population dynamics before and after is not fully understood. In particular, it is unclear how the changes in population dynamics before and after the collapses are associated with biotic interactions. The combination of the availability of unique long‐term time series for herring and cod makes it a well‐suited study system to investigate the effects of collapse. We examine how species interactions may differently affect the herring and cod population dynamic before and after a collapse. Particularly we explore, using a GAM modeling approach, how herring could affect cod and vice versa. We found that the effect of cod biomass on herring that was generally positive (i.e., covariation) but the effect became negative after the collapse (i.e., predation or competition). Likewise a change occurred for the cod, the juvenile herring biomass that had no effect before the collapse had a negative effect after. Our results indicate that the population collapses may alter the inter‐specific interactions and response to abiotic environmental changes. While the stocks are at similar abundance levels before and after the collapses, the system is potentially different in its functioning and may require different management action. [ABSTRACT FROM AUTHOR]

The Gulf of Maine, USA is home to four colonial co-nesting tern species: Least Tern (Sternula antillarum), Common Tern (Sterna hirundo), Arctic Tern (Sterna paradisaea), and the federally endangered Roseate Tern (Sterna dougallii). Over three decades of visual observations of chick provisioning were compiled for a comparative dietary study in the region, including the first detailed descriptions of Least and Roseate Tern chick diets. Three prey groups comprised the majority of chick diets among tern species between 1986–2017: hake (Urophycis spp. or Enchelyopus cimbrius) 28–37% frequency of occurrence (FO), sand lance (Ammodytes americanus or A. dubius) 8–22% FO, and herring (Clupea spp. or Alosa spp.) 3–30% FO. Dietary contributions varied across species and islands. At two inshore colonies, Common Tern diets contained higher amounts of sand lance (30–42% FO), while offshore islands contained lesser amounts (5–9% FO). Overall dietary diversity (H′) was similar between Common (H′ = 1.57) and Arctic Terns (H′ = 1.74) and notably lower in Roseate (H′ = 1.24) and Least Terns (H′ = 1.37), whose diets were primarily piscivorous. The degree of dietary plasticity and general feeding ecology provided by baseline dietary information can inform holistic assessments of risk to ongoing and future disturbances from fishing and climate change. [ABSTRACT FROM AUTHOR]

This study represents the first attempt to assess genotoxicity and cytotoxicity effects in herring (Clupea harengus membras), flounder (Platichthys flesus), and cod (Gadus morhua callarias) caught at 47 study stations, located close to chemical munition dumpsites in the Gotland Basin, the Baltic Sea. Herring sampled from stations located in the center of chemical munition dumpsites exhibited the highest levels of micronuclei (MN) and total genotoxicity (ΣGentox), which is defined as the sum of frequencies of such nuclear abnormalities as micronuclei, nuclear buds, nuclear buds on the filament, and bi-nucleated erythrocytes with nucleoplasmic bridges. Exceptionally high and high ΣGentox risks were determined for flounder (89.47%), herring (79.31%), and cod (50%) caught at the stations located close to the chemical munition dumpsites. [ABSTRACT FROM AUTHOR]

Managing social–ecological systems that benefit both humans and nature is the central challenge of natural resource management. Integrating multiple perspectives into decision-making adds flexibility to social–ecological systems by reducing rigidity and promoting adaptability. Our objective was to assess expert perceptions of the structure, content, and function of the Puget Sound stormwater social–ecological system. We interviewed Puget Sound stormwater experts to document their mental models of the system and compared the network structure of expert maps. We also assessed differences among experts in the components of the social–ecological system which were included in mental models. Our analyses revealed differences between genders, as well as between managers, in how experts characterized the system. Notably, female participants tended to characterize the social–ecological system as one in which there were many system drivers generating multiple impacts across the system. The mental models of the scientists tended to include more resource units than those of the managers, which focused more on governance compared to those of the scientists. Finally, we incorporated the diverse input from mangers and scientists to create a single mental model to represent a consensus on the Puget Sound stormwater social–ecological system. This work highlights the fact that addressing the stormwater problem requires that we embrace the varied perspectives of scientists, managers, and stakeholders. We contend that incorporating the diverse perspectives of experts within the context of social–ecological systems provides a promising path towards a lasting and durable recovery for the ecosystem.

Ocean Acoustic Waveguide Remote Sensing (OAWRS) enables fish population density distributions to be instantaneously quantified and continuously monitored over wide areas. Returns from seafloor geology can also be received as background or clutter by OAWRS when insufficient fish populations are present in any region. Given the large spatial regions that fish inhabit and roam over, it is important to develop automatic methods for determining whether fish are present at any pixel in an OAWRS image so that their population distributions, migrations and behaviour can be efficiently analyzed and monitored in large data sets. Here, a statistically optimal automated approach for distinguishing fish from seafloor geology in OAWRS imagery is demonstrated with Neyman–Pearson hypothesis testing which provides the highest true-positive classification rate for a given false-positive rate. Multispectral OAWRS images of large herring shoals during spawning migration to Georges Bank are analyzed. Automated Neyman-Pearson hypothesis testing is shown to accurately distinguish fish from seafloor geology through their differing spectral responses at any space and time pixel in OAWRS imagery. These spectral differences are most dramatic in the vicinity of swimbladder resonances of the fish probed by OAWRS. When such significantly different spectral dependencies exist between fish and geologic scattering, the approach presented provides an instantaneous, reliable and statistically optimal means of automatically distinguishing fish from seafloor geology at any spatial pixel in wide-area OAWRS images. Employing Kullback–Leibler divergence or the relative entropy in bits from Information Theory is shown to also enable automatic discrimination of fish from seafloor by their distinct statistical scattering properties across sensing frequency, but without the statistical optimal properties of the Neyman–Pearson approach.

Temporal and spatial variability of per- and polyfluoroalkyl substances (PFASs) in herring, cod, eelpout, and guillemot covering four decades and more than 1000 km in the Baltic Sea was investigated to evaluate the effect of PFAS regulations and residence times of PFASs. Overall, PFAS concentrations responded rapidly to recent regulations but with some notable basin- and homologue-specific variability. The well-ventilated Kattegat and Bothnian Bay showed a faster log-linear decrease for most PFASs than the Baltic Proper, which lacks a significant loss mechanism. PFOS and FOSA, for example, have decreased with 0-7% y -1 in the Baltic Proper and 6-16% y -1 in other basins. PFNA and partly PFOA are exceptions and continue to show stagnant or increasing concentrations. Further, we found that Bothnian Bay herring contained the highest concentrations of >C 12 perfluoroalkyl carboxylic acids (PFCAs), likely from rivers with high loads of dissolved organic carbon. In the Kattegat, low PFAS concentrations, but a high FOSA fraction, could be due to influence from the North Sea inflow below the halocline and possibly a local source of FOSA and/or isomer-specific biotransformation. This study represents the most comprehensive spatial and temporal investigation of PFASs in Baltic wildlife while providing new insights into cycling of PFASs within the Baltic Sea ecosystem.

Life-history traits of Pacific (Clupea pallasii) and Atlantic (Clupea harengus) herring, comprising both local and oceanic stocks subdivided into summer-autumn and spring spawners, were extensively reviewed. The main parameters investigated were body growth, condition, and reproductive investment. Body size of Pacific herring increased with increasing latitude. This pattern was inconsistent for Atlantic herring. Pacific and local Norwegian herring showed comparable body conditions, whereas oceanic Atlantic herring generally appeared stouter. Among Atlantic herring, summer and autumn spawners produced many small eggs compared to spring spawners, which had fewer but larger eggs—findings agreeing with statements given several decades ago. The 26 herring stocks we analysed, when combined across distant waters, showed clear evidence of a trade-off between fecundity and egg size. The size-specific individual variation, often ignored, was substantial. Additional information on biometrics clarified that oceanic stocks were generally larger and had longer life spans than local herring stocks, probably related to their longer feeding migrations. Body condition was only weakly, positively related to assumingly in situ annual temperatures (0–30 m depth). Contrarily, body growth (cm × y−1), taken as an integrator of ambient environmental conditions, closely reflected the extent of investment in reproduction. Overall, Pacific and local Norwegian herring tended to cluster based on morphometric and reproductive features, whereas oceanic Atlantic herring clustered separately. Our work underlines that herring stocks are uniquely adapted to their habitats in terms of trade-offs between fecundity and egg size whereas reproductive investment mimics the productivity of the water in question. [ABSTRACT FROM AUTHOR]

The low-technological quality of herring caught during the feeding season makes it impossible to achieve full ripeness of the meat in marinades. One solution may be to assist ripening using herring digestive tract proteases. Therefore, whole herring, headed herring and fillets were marinated for 2–14 days using the German (direct) and Danish (pre-salted) methods. The results showed that the mass of marinades from fillets was lower than from herring with intestines and correlated strongly with salt concentration in the Danish method, in contrast to the German method. Marinades from whole and headed herring had significantly higher trypsin, chymotrypsin, carboxypeptidase-A and cathepsin activities than marinated fillets. The herring marinated with viscera had 2–3 times higher non-protein nitrogen, peptide and amino acid fractions, as well as ripened 3 days faster than the marinated fillets. After 2 weeks of marinating, the fillets did not achieve full ripeness of the meat, unlike marinades made from whole and headed herring. The pre-salting stage in the Danish method significantly reduced cathepsin D activity by the tenth day of marinating, which was compensated by digestive proteases only in the case of whole or headed herring. The digestive proteases activity in the fillets was too low to achieve the same effect. Sensory evaluation of texture and hardness-TPA correlated strongly with several proteases in whole herring marinades, in contrast to a weak correlation with only one protease when marinating fillets. Marinating with intestines makes it possible to produce marinades faster, more efficiently and with higher sensory quality from herring of low-technological quality.