Abstract: Nutritional, structural, functional, and sensorial properties of protein isolate developed from salmon (Salmo salar), cod (Gadus morhua), and herring (Clupea harengus) by-products using the pH-shift method was studied. Function of the proteins in an emulsion system in terms of viscoelastic properties was also evaluated. Regardless of origin, the proteins showed satisfying nutritional value as reflected in their high essential amino acid content. The proteins contained significantly (p < 0.05) higher proportion of active sulfhydryl groups and surface hydrophobicity compared to whey and egg white protein reflecting conformational changes caused by the pH-shift process. Solubility, emulsion, and foaming capacity of the proteins showed a trend similar to soy protein and dependent on their origin. Cod protein had better emulsion and foaming capacity than salmon and herring proteins which was in line with its high surface hydrophobicity and myosin heavy chain content. Emulsions developed from cod and salmon proteins showed substantially better viscoelastic properties, with higher stability and viscosity compared to herring protein emulsions. Cod protein scored low for sensorial attributes related to lipid oxidation while herring protein showed high levels of fishy and rancid flavor and odor. Altogether, results showed that the proteins from fish filleting by-products have potential to be used as food ingredients, but their application would be governed by their origin and sensorial properties.

Abstract: Ocean acidification—the decrease in seawater pH due to rising CO2 concentrations—has been shown to lower survival in early life stages of fish and, as a consequence, the recruitment of populations including commercially important species. To date, ocean-acidification studies with fish larvae have focused on the direct physiological impacts of elevated CO2, but largely ignored the potential effects of ocean acidification on food web interactions. In an in situ mesocosm study on Atlantic herring (Clupea harengus) larvae as top predators in a pelagic food web, we account for indirect CO2 effects on larval survival mediated by changes in food availability. The community was exposed to projected end-of-the-century CO2 conditions (~760 µatm pCO2) over a period of 113 days. In contrast with laboratory studies that reported a decrease in fish survival, the survival of the herring larvae in situ was significantly enhanced by 19 ± 2%. Analysis of the plankton community dynamics suggested that the herring larvae benefitted from a CO2-stimulated increase in primary production. Such indirect effects may counteract the possible direct negative effects of ocean acidification on the survival of fish early life stages. These findings emphasize the need to assess the food web effects of ocean acidification on fish larvae before we can predict even the sign of change in fish recruitment in a high-CO2 ocean.

Abstract: In the coming decades, environmental change like warming and acidification will affect life in the ocean. While data on single stressor effects on fish are accumulating rapidly, we still know relatively little about interactive effects of multiple drivers. Of particular concern in this context are the early life stages of fish, for which direct effects of increased CO2 on growth and development have been observed. Whether these effects are further modified by elevated temperature was investigated here for the larvae of Atlantic herring (Clupea harengus), a commercially important fish species. Over a period of 32 days, larval survival, growth in size and weight, and instantaneous growth rate were assessed in a crossed experimental design of two temperatures (10°C and 12°C) with two CO2 levels (400 μatm and 900 μatm CO2) at food levels mimicking natural levels using natural prey. Elevated temperature alone led to increased swimming activity, as well as decreased survival and instantaneous growth rate (Gi). The comparatively high sensitivity to elevated temperature in this study may have been influenced by low food levels offered to the larvae. Larval size, Gi and swimming activity were not affected by CO2, indicating tolerance of this species to projected "end of the century" CO2 levels. A synergistic effect of elevated temperature and CO2 was found for larval weight, where no effect of elevated CO2 concentrations was detected in the 12°C treatment, but a negative CO2 effect was found in the 10°C treatment. Contrasting CO2 effects were found for survival between the two temperatures. Under ambient CO2 conditions survival was increased at 12°C compared to 10°C. In general, CO2 effects were minor and considered negligible compared to the effect of temperature under these mimicked natural food conditions. These findings emphasize the need to include biotic factors such as energy supply via prey availability in future studies on interactive effects of multiple stressors.

Abstract: This study addressed the lack of recovery of Pacific herring ( Clupea pallasii ) in Prince William Sound, Alaska, in relation to humpback whale ( Megaptera novaeangliae ) predation. As humpback whales rebound from commercial whaling, their ability to influence their prey through top-down forcing increases. We compared the potential influence of foraging humpback whales on three herring populations in the coastal Gulf of Alaska: Prince William Sound, Lynn Canal, and Sitka Sound (133–147°W; 57–61°N) from 2007 to 2009. Information on whale distribution, abundance, diet and the availability of herring as potential prey were used to correlate populations of overwintering herring and humpback whales. In Prince William Sound, the presence of whales coincided with the peak of herring abundance, allowing whales to maximize the consumption of overwintering herring prior to their southern migration. In Lynn Canal and Sitka Sound peak attendance of whales occurred earlier, in the fall, before the herring had completely moved into the areas, hence, there was less opportunity for predation to influence herring populations. North Pacific humpback whales in the Gulf of Alaska may be experiencing nutritional stress from reaching or exceeding carrying capacity, or oceanic conditions may have changed sufficiently to alter the prey base. Intraspecific competition for food may make it harder for humpback whales to meet their annual energetic needs. To meet their energetic demands whales may need to lengthen their time feeding in the northern latitudes or by skipping the annual migration altogether. If humpback whales extended their time feeding in Alaskan waters during the winter months, the result would likely be an increase in herring predation.

Abstract: A critical analysis of literature data on the distribution, morphology, and phylogeography of the Arctic lamprey (Lethenteron camtschaticum) and five species of marine and anadromous fish such as navaga (Eleginus navaga), pollock (Theragra chalcogramma), rainbow smelt (Osmerus mordax dentex), Pacific herring (Clupea pallasii), and pond smelt (Hypomesus olidus) has been performed. The results show that all these species have colonized Northern European seas, distributing along the Arctic coastline of Eurasia after the glacier retreat. The reasons that the dispersal of these species in the Atlantic Ocean may be impeded (preference for a cold environment, competition, and decrease of the evolutionary potential) are discussed.

Abstract: We modeled the biomass of Pacific herring ( Clupea pallasii ) consumed by humpback whales ( Megaptera novaeangliae ) to determine if whales are preventing the recovery of some herring populations in the Gulf of Alaska. We estimated consumption, by whales, of two depressed (Lynn Canal, Prince William Sound) and one robust (Sitka Sound) herring populations during fall/winter of 2007–2008 and 2008–2009. Consumption estimates relied on observations of whale abundance, prey selection, and herring energy content along with published data on whale size and metabolic rate. Herring biomass removed by whales was compared with independent estimates of herring abundance to assess the impact of predation on each population. Whales removed a greater proportion of the total biomass of herring available in Lynn Canal and Prince William Sound than in Sitka Sound. Biomass removals were greatest in Prince William Sound where we observed the largest number of whales foraging on herring. The biomass of herring consumed in Prince William Sound approximated the biomass lost to natural mortality over winter as projected by age-structured stock assessments. Though whales also focused their foraging on herring during the fall in Lynn Canal, whales were less abundant resulting in lower estimated consumption rates. Whales were more abundant in Sitka Sound than in Lynn Canal but foraged predominately on euphausiids. Herring abundance was greater in Sitka Sound, further reducing the overall impact on the herring population. These data indicate that the focused predation in Prince William Sound can exert top-down controlling pressure, but whale populations are not a ubiquitous constraint on forage fish productivity in the Gulf of Alaska at this time.

Abstract: Changes in lipids of herring (Clupea harengus) muscle during different smoking methods and 9 days of refrigeration at 4°C were investigated. The proximate analysis of raw herring revealed that the total lipid, the total protein content and the crude ash were 10.20%, 69.43%, and 19.42%, respectively. The results also indicated that during all processing free fatty acids (FFAs) and peroxide value (PV) increased, whereas iodine value (IV) and total triglycerides decreased. The change were more significantly (p < .05) during unbleached + hot smoking and refrigeration at more than 6 days. All these modification decrease the nutritional value of herring. Bleaching combined to smoking and refrigeration at <6 days had more desire effect on lipid oxidation of herring compared to other treatments. The fish obtained in these conditions are more suitable for feeding heath nutrition.

Abstract: Thiamine (vitamin B1) deficiency in salmonids related to a lipid-rich fish diet causes offspring mortality in the yolk-sac fry phase. A low free thiamine (THIAM) concentration in eggs is an indication of this syndrome. Thiamine deficiency of salmon (Salmo salar) feeding in the Baltic Sea, called M74, was connected to the principal prey fish and feeding area using fatty acid (FA) signature analysis. The FAs of feeding salmon from two areas of the Baltic Sea, the Baltic Proper (57°10′ 19°30′) and the Bothnian Sea (61°30′ 20°00′) in 2004, reflected the principal prey species in these areas, sprat (Sprattus sprattus) and herring (Clupea harengus), respectively. Arachidonic acid (ARA, 20:4n-6) and 18:1n-7 indicated dietary herring, 18:1n-9 dietary sprat and 14:0 feeding in the Baltic Proper. The muscle FA profile of non-M74 female spawners of the River Simojoki in a year (1998) with a moderate M74 incidence and salmon of a non-M74 year (2004) reflected herring FAs, whereas the FAs in the M74 year and specifically in M74 females displayed characteristics of sprat. In the M74 year, the THIAM concentration had the strongest positive correlation with the proportion of muscle ARA, and the strongest negative correlations with 14:0 and the ratios 18:1n-9/ARA and 14:0/ARA. Thus, ARA along with 14:0 and these ratios were the most sensitive FA indicators of the dietary species and origin of the M74 syndrome. Despite the pre-spawning fasting, tissue FA signatures were consequently able to connect dietary sprat in the Baltic Proper with thiamine deficiency in Baltic salmon.

Abstract: In the North of Europe two sister species of herring—the Atlantic Clupea harengus and Pacific Clupea pallasii have post-glacially come into secondary contact. Although the breeding areas of the two species are thought to be separate, previous genetic studies based on allozyme and mitochondrial DNA data have supported the existence of introgression from the Atlantic herring to the Pacific herring. In this study, we employed microsatellite markers to explore the extent of introgressive hybridization between these fishes. Bayesian methods for assigning individuals to populations and identifying admixture proportions were applied to the genetic data based on ten microsatellites. Results indicated that 18 out of 464 Pacific herring (3.88%) were likely admixed. Some of the hybrid individuals contained genotypes suggesting that introgressive hybridization is an ongoing process. Despite some admixture, the Atlantic and Pacific herring gene pools remain sharply distinct (the average proportions of membership to “Atlantic” and “Pacific” clusters were QA = 0.998 and QP = 0.974, respectively), suggesting that hybridization was not frequent. The discovery of introgression among herring species opens new questions about the mechanisms underlying the observed pattern of genetic population differentiation in the North European Pacific herring.

Abstract: Atlantic herring (Clupea harengus) populations in Newfoundland, Canada, are characterized by springand autumnspawning components, targeted as a mixed fishery. The spring-spawning component accounted for ~90% of the total catch until the early 2000s, but autumn-spawning herring now dominate the catch in most areas. We explored the links between recruitment of autumn-spawning herring and variability in larval prey and temperature during first winter. The main prey during the early larval stage was nauplii of the copepods Temora longicornis and Oithona similis. In the midlarval stage, Pseudocalanus sp. strongly dominated the diet. In the late-larval stage, larvae shifted to the larger calanoid copepods Calanus sp. The phenology of Pseudocalanus sp. shifted from a spring to autumn bloom during the mid-2000s, concurrent with the change of the springand autumn-spawning components. This change in zooplankton phenology suggests that conditions for herring larval survival have improved during autumn, although no significant relationships were found between recruitment and prey abundance or temperature. Our results suggest that multiple factors, rather than a single driver, interact in the regulation of herring year-class strength. Survival is the outcome of growth and mortality, making it important considering predation pressure along with prey availability in future studies.

Abstract: Shallow shore zones are generally considered to provide juvenile habitats for many invertebrate and fish species and additionally serve as spawning grounds for important components of oceanic food webs and fishery resources such as herring (Clupea spp.). Herring attach their demersal eggs to benthic substrates, rendering reproduction success vulnerable to environmental changes and local habitat alterations. However, little information is available on the effects of different substrates on the survival of demersal eggs. Hypothesizing that the structural complexity of spawning substrates generally affects herring egg survival and that the effect magnitude depends on the suitability of ambient environment, field experiments were conducted on a major spawning ground of C. harengus in the Southwestern Baltic Sea. Herring eggs were artificially spawned on substrates of different structural complexities and incubated in situ under differing temperature regimes, at the beginning and the end of the natural herring spawning season, to include the full suite of stressors occurring on littoral spawning beds. Results of this study indicate a positive relation between high structural complexity of spawning substrates and herring egg survival. Mean egg mortality was three times higher on substrates of lowest complexity than on highly complex substrates. These differences became even more prominent under unfavorable conditions that appeared with rising water temperatures later in the spawning season. Although the mechanisms are still unclear, we conclude that structural complexity, particularly formed by submerged aquatic vegetation, provides a crucial prerequisite for the successful reproduction of substrate spawning marine fishes such as herring in the Baltic Sea.

Abstract: Environmental genotoxicity in the Gulf of Riga was assessed using different bioindicators (fish, clams, and isopods) collected from 14 study stations. Comparison of genotoxicity responses (micronuclei (MN) and nuclear buds (NB)) in blood erythrocytes of herring (Clupea harengus), eelpout (Zoarces viviparous), and flounder (Platichthys flesus) revealed the species- and site-specific differences. For the first time, the analysis of genotoxicity was carried out in gill cells of isopods Saduria entomon. The highest inductions of MN and NB in gill cells of investigated S. entomon and clams (Macoma balthica) were evaluated in specimens from station 111A (offshore zone). In fish, the highest incidences of MN were measured in eelpout and in herring collected in the southern part of Gulf of Riga (station GOR3/41S). Moreover, in the southern coastal area, the assessment of genotoxicity risk (according to micronuclei levels) indicated exceptionally high risk for flounder, eelpout, and clams.

Abstract: Distributions of eggs, larvae and juveniles of Pacific herring Clupea pallasii were surveyed in Lake Akkeshi and the connecting Akkeshi Bay on the Pacific coast of eastern Hokkaido. Eggs were found attached to seagrasses and seaweeds in the densely vegetated eastern inner lake. Larvae (7.1–34.9 mm total length) were distributed in the less densely vegetated inner lake during April and June. Juveniles (35.0–89.6 mm) were collected in the central and western parts of the lake. The sites containing juveniles were less densely vegetated with water temperatures lower than 20 °C from June to August. When the water temperature of the entire lake rose to 20 °C in late summer, juveniles appeared to move from the lake to the bottom layer of Akkeshi Bay, which has lower temperatures. Thus, in Akkeshi waters, C. pallasii successively used different habitats during its egg, larval and juvenile stages. A comparison of the current limited distribution of eggs and larvae with the distribution over the entire lake and bay areas in the 1950s and 1960s (periods of large catch size) indicates that the spawning grounds and larval habitats of C. pallasii have contracted to the lake area due to low spawning stock biomass in recent years.

Abstract: Fatty acids (FAs) were analysed in Baltic herring (Clupea harengus membras) stored in the Swedish Environmental Specimen Bank for up to 40 years. The purpose was to evaluate the retrospective use o ...

Abstract: The Baltic Sea is a frontrunner in ecosystem analysis and assessment, which have been used also in multispecies fisheries management advice. In the Baltic Sea, the multispecies assessment and management advice have been focused on the pelagic interactions between cod (Gadus morhua), sprat (Sprattus sprattus) and herring (Clupea harengus), by virtue of their well-known ecology. However, the fish in-teractions occurring in the benthic habitat are largely unknown. This study investi-gates, for the first time, the feeding interactions between the most important de-mersal fish species, cod and flounder (Platichthys flesus), in three areas of the eastern Baltic Sea. In this study I use stomach data from 2015 and 2016, collected in the ICES subdivisions 25 – 28 by the Swedish University of Agricultural Sci-ences, Department of Aquatic Resources. The diet of cod differs between the areas but, overall, shows an ontogenetic shift with a decrease of benthic prey and an in-crease of fish preys with size. In the coastal area the amount of benthic prey is al-ways > 50% irrespective of predator size, while in the offshore areas the amount of fish prey increase > 50% with increasing cod size. Conversely, the diet of flounder is relatively constant between sizes and areas. Cluster analyses revealed similarity between the diet of flounder and small-medium size cod in the offshore areas. A significant diet overlap was found between cod 20 cm in the offshore area in SD 25, which is mainly driven by similar benthic prey, espe-cially Saduria entomon, in the diet of both predators. These results point to a food competition between cod and flounder, likely augmented by recent increased abundance of Baltic flounder stocks. This competition could decrease the availa-bility of benthic prey for cod, which, in turn, can lead to low condition factor, a re-duction of cod growth and ultimately accentuate the negative effects of hypoxia on cod. Because of all of these reasons, cod and flounder competition could be an-other factor explaining the current bad status of the Eastern Baltic Cod stock.

Abstract: The humpback whale (Megaptera novaeangliae) has a cosmopolitan distribution: it occurs in all oceans and in many seas. Remarkably, the species was missing from the southern North Sea until recently. Even strandings of dead animals have always been very rare but from the 1990s onward this started to change. A trickle of dead humpback whales was the first sign that things were about to change, followed by sightings of live whales from 2001 on. Many of the first whales to arrive in the southern North Sea did not survive, and stranded, but this too has changed. Today, humpback whales visit the region every year in small numbers and both adults and juveniles are involved. The whales rarely fluke in the shallow coastal waters where they are mostly seen but a few wellmarked individuals have been seen in different years and some stayed up to several months in the area. It remains unclear what might have triggered this range extension. Numbers of humpback whales in the Atlantic are increasing after the cessation of whaling, but numbers are still short of the pre-whaling population size (when the species was absent from the southern North Sea). Some forage fish species, like herring (Clupea harengus) are also on the increase, but stocks are still depleted compared to the past. Most likely, therefore, something has changed in the whales themselves, causing them to be more inquisitive and to explore new waters. Once they have arrived in the southern North Sea, their behaviour shows that they can find sufficient food here.

Abstract: A widespread ichthyophoniasis epizootic occurred in the Icelandic summer-spawning herring (Clupea harengus) stock during the years 2008–2014. The spatial and temporal variation in prevalence of hea...

Abstract: We studied the at-sea distribution of two auks (Common Murre Uria aalge, Razorbill Alca torda), two gulls (Lesser Black-backed Gull Larus fuscus, Herring Gull Larus argentatus), and Great Cormorant Phalacrocorax carbo during the peak breeding season of 2014 around Stora Karlso, the main Baltic Sea seabird colony. Simultaneously, we quantified forage fish abundance and distribution using hydro-acoustics and pelagic trawling. The auks and gulls had a roughly similar distribution, foraging mainly about 40 km west-northwest from the colony. Great Cormorants were found only in inshore areas, close to the colony. Sprat Sprattus sprattus and herring Clupea harengus biomass was, respectively, 1.38 and 2.68 mt/km2 averaged over the whole study area. These estimates represent a total biomass for small pelagic fish of 17 900 t in the 4 408 km2 study area. The estimated prey consumption over the breeding season was 2 310 t for Common Murre and Razorbill combined. Thus, auks may have a non-negligible impact on their prey sources in the region. Common Murres foraged closer to the colony (median 36.3 km) than Razorbills (median 41.1 km), but we found no significant correlation between auk at-sea numbers and fish densities. We discuss how new technology can contribute to detailed monitoring of the interactions between seabirds and fish at different spatial and temporal scales, with the ultimate aim of providing a scientific basis for ecosystem-based management. (Less)

Abstract: The Icelandic summer‐spawning herring (Clupea harengus) stock overwinters in large, dense schools like other herring stocks. In the winter of 2012/2013 around 300 thousand tonnes, or ~70% of the spawning stock, overwintered in a fjord west of Iceland. The inner part of the fjord, where the herring was located, is separated from the outer part with a natural barrier and a built‐up road with a 210 m long bridge. This creates strong tidal currents under the bridge. On 14 December and again on 1 February mass mortalities of herring took place in this location, and the sea floor and the shores were covered with dead herring. Fieldwork, including camera and video recordings on the shore and on a small boat, was conducted 3 and 4 days after the incidents. Results from this indicated that a total of 55 thousand tonnes had died during these two incidents, an amount nearly equal to the total catch from the stock that year. Measurements of environmental conditions in the days following the incidents showed that the oxygen saturation was generally 20%–40% but was as low as 15% (1.1 ml/L). The most likely explanation for the mortalities was oxygen depletion resulting from respiration of the large herring biomass, limited atmospheric‐water gas exchange due to calm and cold weather prior to both incidents and sea ice on part of the fjord, and limited renewal of water coming in and out via tidal currents. Aerobic decomposition of dead herring came additionally in the latter incident.

Abstract: The genetic variability of ten microsatellite loci was examined in samples of the herring from the Sea of Okhotsk and the Bering Sea. All loci were polymorphic; the expected heterozygosity estimates varied in the range of 0.3–94.3% (mean 66.7%). The degree of genetic differentiation of the herring was statistically significant (θ = 1.38%). The level of pairwise genetic differentiation FST was–0.002–0.046; RST was–0.003–0.166. Genetic differentiation of the herring from the Sea of Okhotsk and the Bering Sea correlated with the spatial-geographic structure of the species in the studied range on the basis of FST (P = 0.001).

Abstract: From 1996 to 2011, researchers observed Phoca vitulina concolor (Western Atlantic Harbor Seal) on regional overwintering grounds in the Great Bay–Mullica River estuary in southern New Jersey. Over this 15-y time series, 299 observations were completed, with maximum local abundance increasing from 100 individuals in 1996 to 160 individuals in 2011. Our study did not document the presence of Atlantic Harbor Seal pups. In addition, we analyzed 142 scat samples, resulting in 1419 sagittal fish otoliths recovered and identified. Dominant recovered otoliths were as follows: 48% Phycidae (Urophycis regia [Spotted Hake]/Urophycis chuss [Red Hake]; 25% Clupeidae (Clupea harengus [Atlantic Herring], Alosa sapidissima [American Shad], Brevoortia tyrannus [Atlantic Menhaden], A. pseudoharengus [Alewife], and A. aestivalis [Blueback Herring]); 13% Ammodytidae (Ammodytes americanus/A. dubius [sandlance]); 6% Pseudopleuronectes americanus (Winter Flounder); and 4% Scophthalmus aquosus (Windowpane Flounder). Average back-calculated prey lengths across all prey groups (min–max = 5–41 cm, average = 19.75 cm) indicated that Western Atlantic Harbor Seals might utilize both estuarine and ocean environments for foraging. This temperate estuary currently represents the southern limit of routine Western Atlantic Harbor Seal occupancy in the Northeast. As such, our results are valuable in monitoring future changes in habitat use potentially resulting from climate change.

Abstract: Pacific herring Clupea pallasii inhabiting around Japan migrate to coastal areas to spawn and are often caught by gill and set nets of coastal fisheries. For sustainable resource management, it is necessary to understand the behavioral patterns of such spawning migration in coastal spawning grounds. In this study, the migration of herring found in the Akkeshi region in eastern Hokkaido was revealed using acoustic telemetry. Individuals showed two movement patterns, viz. migration to Akkeshi Lake and remaining in Akkeshi Bay. For those migrating, most individuals entered the lake within 12–48 h. Two individuals reached the end of the lake within 1–3 days, and herring eggs and individuals in the process of spawning were found there. Consequently, this migration is likely related to spawning in the lake. The timing of migration to the lake appeared to be related to tidal dynamics. For those remaining in the bay, pings were detected at several locations, but none in any area beyond the relatively short period of 1–4 days. It is therefore possible that individuals moved more widely and quickly than the detection range of the receiver and the frequency of the survey in the bay.

Abstract: ТИХООКЕАНСКАЯ СЕЛЬДЬ, ДИНАМИКА БИОМАССЫ, ПРОДУКТИВНОСТЬ, ОХОТСКОЕ МОРЕ На основе собственных материалов и литературных данных исследованы динамика биомассы и формирование соматической продукции сельди Тауйской губы и других популяций вида Охотского моря и прилегающих акваторий. Установлено, что в зависимости от особенностей темпов весового роста и естественной убыли сельди, с возрастом между популяциями вида наблюдаются различия, выражающиеся в асимметрии параболических кривых динамики биомассы, характеризующих разную скорость ее нарастания и убыли. По этому показателю сельдь Тауйской губы близка к гижигинско-камчатской популяции и вместе с ней образует крупный кластер с сельдями Юго-Восточной Камчатки. Все они характеризуются сравнительно медленным нарастанием биомассы с возрастом и поздним наступлением кульминации биомассы. Напротив, географически близкая к тауйской сельди охотская популяция вида близка к сельди зал. Де Кастри. Обе они обнаруживают сходство с группировками сельди побережья Восточного Сахалина. По показателю удельной продукции (Р/В-коэффициент) сельдь Тауйской губы уступает гижигинско-камчатской и охотской популяциям вида, что может быть исторически обусловлено ее небольшим ареалом, ограниченным с востока и запада районами распространения этих крупных по численности популяций.

Abstract: Coastal ecosystems provide essential spawning and nursery areas for numerous economically important marine fish species. At the same time they are extremely exposed to anthropogenic modifications and habitat degradation. Potentially, effects of hazards acting on the local scale of coastal fish nursery habitats might become directly transported to the level of adult fish populations, eventually affecting population dynamics on far broader spatial scales. Atlantic herring (Clupea harengus) is among the most intensely studied fish species in the world, but owing its high plasticity, there are still numerous uncertainties on the drivers of herring population dynamics and habitat dependency, emphasizing the risk to jeopardize population resilience by on-going habitat alterations. Atlantic herring in the Western Baltic Sea is an extraordinarily important fishery target and simultaneously representing a crucial link between different trophic levels of the food web. Since herring recruitment decreased within the last 17 years for widely unknown reasons, it is assumed that multiple hazards have a cumulative impact on a local scale of important spawning grounds, being vital for Western Baltic herring reproduction. However, the quantitative contribution of single spawning areas to the overall population has not been empirically investigated. Western Baltic herring is considered to annually return to bays and estuaries for spawning their benthic eggs on submerged aquatic vegetation. This homing behavior potentially renders the population rather vulnerable against changes of those inherent areas. Hence, the knowledge on habitat dependency of herring throughout the life cycle is essential to understand recruitment variability. The first part of this thesis deals with the identification of important nursery areas for the Western Baltic herring population. Elemental fingerprinting in age-0 herring otoliths from four different spawning areas along the Western Baltic coastline was used to identify habitat-specific chemical signatures. Additionally, these natal fingerprints were combined with otolith core signatures from adult herring to investigate the contribution of single spawning habitats to the overall population. Analysis revealed that the quantitative contribution of Greifswald Bay to the adult population was generally major, but the exact magnitude varied between the years. According to herring homing behavior, this thesis provided first evidence that Atlantic herring in the Western Baltic Sea return to their natal spawning areas, revealing a strong, inherent dependency on certain inshore coastal spawning areas, such as Greifswald Bay. The second part of the thesis deals with the identification of local drivers and stressors, acting on the nursery area Greifswald Bay to evaluate potential effects on population dynamics. Eutrophication-based cascading effects resulted in a decline of macrophyte spawning substrate in Greifswald Bay with current growth limits of about 3.5 m. This vertical distribution limit of spawning beds increases the vulnerability of benthic herring eggs to multiple stressors, such as storm-induced hydrodynamics and increased water temperatures, which could highly impact annual fish recruitment. This thesis demonstrated that inshore coastal systems, including vegetated littoral zones, are particularly important for all herring life stages (from the egg to the larvae and juveniles to the matured adult herring). Their functions include nursery areas for juveniles, sheltered retention and development areas for eggs and larvae and spawning grounds for adult fish. Considering the persistent level of eutrophication in combination with future climate change scenarios including increasing storm intensities, -frequencies and increasing temperatures, the results of this thesis underline the demand for an integrated and sustainable management of shallow coastal spawning grounds. Kustengewasser mit ihren geschutzten Buchten, Lagunen und Astuaren sind weltweit wichtige Laichgebiete und Kinderstuben fur zahlreiche kommerziell genutzte Fischarten. Im Ubergang vom Land zum Ozean und damit in der Zone der hochsten Bevolkerungsdichten, unterliegen diese Systeme einer enormen Veranderung durch menschliche Nutzung. Zudem unterliegt die Okologie der flachen inneren Kustengewasser einer starken saisonalen Dynamik und reagiert unmittelbar auf klimatische Veranderungen. Je nach ihrem spezifischen Beitrag an Fischnachwuchs kann eine Verschlechterung der Umweltbedingungen auf der relativ lokalen raumlichen Skala dieser wichtigen Reproduktionsgebiete die Dynamik gesamter Fischpopulationen beeinflussen. Der Atlantische Hering (Clupea harengus) zahlt zu den am besten untersuchten Fischarten der Welt und dennoch gibt es immer noch Unklarheiten uber wichtige Mechanismen der Populationsdynamik, uber die raumliche Nutzung der Laichgebiete und somit uber die gebietsspezifische Abhangigkeit der Adult-Population von bestimmten Reproduktionsgebieten. Der Atlantische Hering der westlichen Ostsee ist der „Brotfisch“ der lokalen Kustenfischer und somit einer der wichtigsten Zielarten fur die kommerzielle Fischerei in der Ostsee. Zugleich spielt der Hering eine essentielle okologische Rolle in marinen Nahrungsnetzen, da er ein wichtiges Bindeglied zwischen verschiedenen trophischen Ebenen darstellt. In den letzten 17 Jahren hat die Nachwuchsproduktion des Herings der westlichen Ostsee stark abgenommen. Es wird vermutet, dass zahlreiche lokale Stressoren einen negativen Einfluss auf den Reproduktionserfolg haben. Jedoch gibt es bislang keine Studien zu dem quantitativen Beitrag einzelner Laichgebiete und „Kinderstuben“ zur Gesamtpopulation, um den Einfluss der lokalen Stressoren abschatzen zu konnen. Zudem weist der Hering ein besonderes Verhalten der Brutortstreue auf (Homing-Verhalten). Wahrend seiner jahrlichen Wanderungen kehrt der Hering jedes Fruhjahr zu seinen Laichplatzen in den Lagunen und Buchten entlang der westlichen Ostseekuste zuruck, um dort seine klebrigen Eier an vorhandene Unterwasservegetation zu heften. Neben der Funktion als Laichgebiet fungieren die inneren Kustengewasser als Retentionsgebiete in denen die gesamte larvale Entwicklung abgeschlossen wird. Darum ist es besonders wichtig den Grad der Abhangigkeit dieser Fischart zu ihren Laichgrunden zu untersuchen, um die Variabilitat der Rekrutierung zu verstehen. Der erste Teil dieser Arbeit beschaftigt sich mit der Identifikation der wichtigen Kinderstuben des Herings der westlichen Ostsee. Anhand von Otolithen-Mikrochemie wurden juvenile Heringsotolithen aus vier verschiedenen Laichgebieten auf ihre gebietsspezifischen, chemischen Unterschiede untersucht. Die gefundenen chemischen Signaturen wurden mit der Kernregion (juvenil-Phase) von adulten Heringsotolithen verglichen, um den Beitrag der vier untersuchten Gebiete zur Gesamtpopulation abzuschatzen. Die Analyse ergab, dass das Laichgebiet „Greifswalder Bodden“ ein sehr wichtiges Aufwuchsgebiet fur die fruhen Entwicklungsstadien des Herings ist und dieses Laichgebiet quantitativ am Meisten zu der Adult-Population beigetragen hat. Der quantitative Beitrag variierte allerdings zwischen den beiden untersuchten Jahresklassen. Im Zusammenhang mit dem „Homing“-Verhalten des Herings wurde die raumliche Skala der Brutortstreue untersucht und die Hypothese aufgestellt, dass die adulten Heringe jedes Jahr zu ihrem Laichgebieten zuruckkehren, wo sie einst selbst geschlupft sind. Die Ergebnisse haben gezeigt, dass der Hering im Zuge seiner jahrlichen Migration zu seinem Ursprungslaichgebiet zuruckkehrt. Diese Untersuchungen zeigen erstmals, dass einzelne Laichgebiete die gesamte Population zu tragen scheinen und beweisen die starke gebietsspezifische Abhangigkeit des Herings zu bestimmten Laichgebieten. Im zweiten Teil dieser Arbeit wurden lokale Faktoren untersucht, die auf dieses wichtige Gebiet einwirken und somit masgeblich die gesamte Heringspopulation beeinflussen konnen. Der massive Eintrag von Nahrstoffen aufgrund intensiver landwirtschaftlicher Nutzung und die resultierenden Kaskadeneffekte fuhrten in der Vergangenheit zu einem starken Ruckgang der Makrophyten, und somit zu einem Ruckgang des Laichsubstrates. Die Ergebnisse haben gezeigt, dass Sturm-induzierte Hydrodynamik in der bewachsenen Flachwasserzone zu einer drastischen Ei-Sterblichkeit fuhren kann. Zusammenfassend kann aus den Ergebnissen dieser Arbeit geschlossen werden, dass einzelne Gebiete (wie der Greifswalder Bodden) von enormer Wichtigkeit fur den Fortbestand des Herings der westlichen Ostsee sind. Zudem sind alle Lebensstadien (vom Ei uber die Larve bis hin zum adulten Hering) stark auf die bewachsene Litoralzone in den inneren Kustengewassern angewiesen.