Clupea Harengus Pallasi Research Articles

A comparison of diet estimates of captive beluga whales using fatty acid mixing models with their true diets

Beluga whales (Delphinapterus leucas) are sentinel species for Arctic environmental change; however, whether belugas are resilient to anticipated changes in prey dynamics remains uncertain, partly due to a lack of dietary information. Mixing models are promising tools to evaluate the diets of marine mammals, using dietary tracers such as fatty acid signatures. Additionally, captive feeding trials are useful to test the effectiveness of these tools for application to wild populations. In our study, we compared the ability of two models, quantitative fatty acid signature analysis in R (QFASAR) and Fatty Acid Source Tracking Algorithm in R (FASTAR) to reconstruct the diets of captive beluga whales that had been fed a long-term diet consisting mostly of Pacific herring (Clupea harengus pallasi), and in smaller proportions, capelin (Mallotus villosus) and squid (Doryteuthis opalescens). To account for fatty acid metabolism, we compared a suite of calibration coefficients derived from captive feeding trials of American mink (Mustela vison), harp seal (Pagophilus groenlandicus), harbour seal (Phoca vitulina richardsi), and grey seal (Halichoerus grypus) fed monotypic diets. For both methods, diets estimated using calibration coefficients derived from feeding trials of mink fed herring and/or seal oil were able to correctly identify herring as the dominant prey source of belugas. In addition, there was higher precision among diet estimates using these calibration coefficients in comparison to those generated using calibration coefficients derived from feeding trials of pinnipeds or mink fed poultry. QFASAR more accurately approximated the diet proportions of the whales than FASTAR, possibly because of the greater robustness to errors in the calibration coefficients. Based on QFASAR, diet estimates best reflect the whales' true dietary proportions consumed approximately two weeks to one month prior to sampling, similar to timeframes seen in previous studies of harbour seals. We recommend caution when using these models with prey that have high within-species variability in fatty acid signatures or small sample sizes, as well as prey with similar fatty acid signatures. The application of mixing models is promising to identify the prey of wild beluga whales and other marine mammals.

Trade-offs in prey quality and quantity revealed through the behavioral compensation of breeding seabirds

Many productive ocean ecosystems are also highly variable, resulting in complex trophic interactions. We analyzed interannual patterns in the diet of a seabird, the common murre Uria aalge, in a region of high oceanographic productivity, the northern California Current, to investigate how these top predators adjust their chick provisioning to cope with environmental variability. Murres relied chiefly on Pacific herring Clupea harengus pallasi and surf smelt Hypomesus pretiosus to provision chicks, although they regularly returned 8 other fish taxa. Pro- visioning success was measured by the energy return rate to chicks, which in turn was disarticu- lated into energy per meal (quality) and meal delivery rate (quantity). Parents exhibited 'compen- sation' during 2 years in which smaller, low quality prey were returned more quickly than in years with normal (i.e. 'good') provisioning. Despite the increased delivery rate, energy return rates were still lower in 'compensation' vs. 'good' years. The lowest energy return rates occurred in 3 'poor' years, during which ocean productivity was also depressed. Our results suggest that mur- res in this system have the ability to shift provisioning strategies to deal with some variability in prey resources, but not when limited by exceptionally poor environmental conditions.

North Pacific basin-scale differences in lower and higher trophic level marine ecosystem responses to climate impacts using a nutrient-phytoplankton–zooplankton model coupled to a fish bioenergetics model

We present a modeling approach where we use one common model formulation of a 11 state variable lower trophic level model that includes two groups of phytoplankton, three groups of zooplankton, and representations of nitrogen and silicate embedded in a three-dimensional ocean general circulation model (OGCM) and forced with a common climate forcing. Results are applied to a fish bioenergetics model for two geographically distinct ocean regions off Japan including the Oyashio, mixed, and Kuroshio subregions and off California including the subarctic, transition and subtropical subregions. The model is applied to two fish species (Pacific saury: Cololabis saira and Pacific herring: Clupea harengus pallasi) with different life histories in each region and the influence of three different “regime shift” periods was explored. With this approach, we narrow the observed biological response and model dynamics to reflect local conditions and eliminate differences related to the model formulations in each region. In general, the trend in temperature was negatively correlated with trends in the zooplankton community. Out-of-phase herring growth trends were observed between the Japan and California regions ( r = −0.259, p = 0.02). In-phase growth trends between herring and saury were observed at the California region ( r = 0.61, p < 0.01). We did note some evidence of a basin-scale PDO mode response. During 1980–1985, simulated saury and herring in both regions showed a consistent increase in weight-at-age. In the Oyashio subregion, temperature decreased and all three zooplankton groups increased beginning around 1980. The same pattern of a decrease in temperature and an increase in zooplankton densities was observed between 1980 and 1985 in the subarctic subregion of California. Results are discussed in the context of ecosystem-based fisheries management.

Comparison of fatty acid profiles of spawning and non-spawning Pacific herring, Clupea harengus pallasi

Crude lipid and fatty acid composition from liver, intestine, roe, milt and flesh of spawning and non-spawning Pacific herring ( Clupea harengus pallasi) were examined to determine the relative effects of spawning on the nutritional value of herring. Depletion of lipid due to spawning condition was significant ( P < 0.01) in all organ tissues and flesh of spawning herring. The lipid content ranged from an average of 1.9 to 3.4% (wet weight basis) in different organ tissues of spawning herring, to 10.5 to 16% in non-spawning fish. The fatty acid profile exhibited many differences in the relative distribution of individual fatty acids among organ tissues and between the two fish groups. Oleic acid (C18:1n-9), a major monounsaturated fatty acid (MUFA) found in all tissue lipids, decreased significantly ( P < 0.01) in spawning fish. The two monoenes, C20:1n-9 and C22:1n-11, occurred at high concentrations in the flesh but at only minor proportion in the digestive organs and gonads. Spawning herring also had significantly ( P < 0.01) higher polyunsaturated fatty acids (PUFA) content in the organ tissues, particularly in the milt and ovary, with docosahexaenoic acid (C22:6n-3, DHA) having the greatest proportion. Among the n-6 fatty acids, only C18:2n-6 and C20:4n-6 occurred at notable amounts and were present in higher proportions in spawning fish. We concluded that although relatively higher n-3 fatty acid content was found in the organ lipids of spawning herring, they are not an energy-dense prey food source due to the fact that both flesh and gonads contain a very low amount of lipid.

Effect of boiling and frying on the content of essential polyunsaturated fatty acids in muscle tissue of four fish species

Frozen samples of common fish species, sea trout ( Salmo trutta), from Norway and Siberia, herring ( Clupea harengus pallasi), rock sole ( Lepidopsetta bilineata) and cod ( Gadus morhua maris-albi), collected from a wholesale market in Krasnoyarsk city (Siberia, Russia) were analyzed. Special attention was paid to long-chain essential polyunsaturated fatty acids: eicosapentaenoic, 20:5ω3 (EPA) and docosahexaenoic, 22:6ω3 (DHA). Heat-treatment (cooking and frying) did not in general significantly decrease the contents of EPA and DHA compared to raw fish species, except for a modest reduction in Norwegian trout during frying. Boiled trout appeared to be a more valuable fish dish for obtaining the officially recommended appropriate daily intake of EPA + DHA for humans. Herring and sole had intermediate values, while boiled cod had a comparatively low value.

Dissolved saxitoxin causes transient inhibition of sensorimotor function in larval Pacific herring (Clupea harengus pallasi)

Herring (Clupea harengus pallasi) spawning sites in Puget Sound, Washington overlap spatially and temporally with blooms of Alexandrium catenella, a toxic dinoflagellate species responsible for paralytic shellfish poisoning. Consequently, newly hatched herring larvae may be regularly exposed to the suite of dissolved paralytic shellfish toxins that are released into the water column from toxic cells during blooms. To date, virtually nothing is known about the impacts of these neurotoxins on early developmental stages of marine fish. In the present study, herring larvae at three ages, 0 days post hatch (dph), 4 dph, and 11 dph, were exposed to dissolved saxitoxin (STX) in 24-h and multi-day exposures. All larvae were examined for sensorimotor function (i.e. spontaneous swimming behavior and touch response). Significant reductions in spontaneous and touch-activated swimming behavior occurred within 1 h of exposure. EC50s at 1 h of exposure were 1,500, 840, and 700 μg STX equiv. l−1 for larvae introduced to STX at 0, 4, and 11 dph, respectively. This progressive age-specific increase in STX-induced paralysis suggests that older larvae were more sensitive to the toxin than younger larvae. Interestingly, herring larvae at all ages exhibited a significant degree of neurobehavioral recovery within 4–24 h of continuous exposure relative to the 1-h time point. This recovery of normal motor behaviors was not observed in previous studies with freshwater zebrafish (Danio rerio) larvae under the same continuous exposure conditions, suggesting that an adaptive detoxification or toxin sequestration mechanism may have evolved in some species of marine fish larvae. Our data reveal that (1) dissolved STX is bioavailable to marine finfish larvae, (2) the toxin is a paralytic agent with potencies that differ between developmental stages, and (3) STX-induced sensorimotor inhibition occurs rapidly but is transient in marine larvae. Collectively, these results suggest that dissolved algal toxins may have important sublethal effects on marine fish populations.

Fat content and fatty acid composition of forage fish and invertebrates in Prince William Sound, Alaska: factors contributing to among and within species variability

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 241:161-181 (2002) - doi:10.3354/meps241161 Fat content and fatty acid composition of forage fish and invertebrates in Prince William Sound, Alaska: factors contributing to among and within species variability Sara J. Iverson1,*, Kathryn J. Frost2, Shelley L. C. Lang1 1Department of Biology, Dalhousie University, 1355 Oxford St., Halifax, Nova Scotia B3H 4J1, Canada 2Alaska Department of Fish and Game, Division of Wildlife Conservation, 1300 College Road, Fairbanks, Alaska 99701, USA *E-mail: sara.iverson@dal.ca ABSTRACT: We determined the fat content and fatty acid composition of 26 species of fish and invertebrates (n = 1153) that are primary forage species of piscivorous seabirds and marine mammals in Prince William Sound (PWS), Alaska. Flatfish, shrimps and octopus had the lowest average fat contents (~1.0%), although some cods, as well as juvenile walleye pollock Theragra chalcogramma, Pacific herring Clupea harengus pallasi and pink salmon Oncorhynchus gorbuscha also ranged as low as 0.5 to 0.7% fat. The highest fat contents were found in eulachon Thaleichthys pacificus (25%), adult herring (21%) and the squid Berrytheuthis magister (5 to 13%). Within species, fat content varied mostly with season, but also with size. Fatty acid signatures generally distinguished forage species, with up to 95% of individuals correctly classified using either discriminant or classification and regression tree (CART) analyses. Discriminant plots provided insight into the relationships between fatty acid signatures of different species. Species with similar life histories and diets clustered closer together, while those with the greatest differences in ecology differed most in their fatty acid patterns. Within some species, changes in fatty acid signatures were apparent with increasing size and were consistent with known dietary shifts reported from stomach contents analyses. Furthermore, fatty acid signatures of Age 0 (yr) pollock and herring in PWS were consistent with previous stomach contents analysis that indicated annual differences in the timing of dietary changes from eating zooplankton to piscivory. Overall, when size/age classes were taken into account, species classification using fatty acid signatures was improved. Our findings have important implications for evaluating diets and food web interactions of fish stocks, as well as at higher trophic levels. Despite individual variation within species, our results indicate that fatty acid signatures accurately characterize forage species in this ecosystem, and consequently can be used to study and perhaps estimate the species composition of diets of their predators. KEY WORDS: Fatty acids · Forage fish · Food webs · Trophic interactions Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 241. Online publication date: October 04, 2002 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2002 Inter-Research.

Detecting environmental regimes in fish stock-recruitment relationships by fuzzy logic

A fuzzy logic approach is developed to model and test the impact of environmental regimes on fish stock–recruitment relationships. Traditional methods use environmental variables to classify stock–recruitment data into different membership percentiles followed by fitting the stock–recruitment models for each subset. In contrast, the fuzzy logic approach uses a continuous membership function to provide a rational basis for the classification. Thus, parameter estimation is based on a more logically consistent foundation without resorting to subjective partitions. This new approach is applied to herring stock from the west coast of Vancouver Island (Clupea harengus pallasi) using sea surface temperature as the environmental variable and to Pacific halibut stock (Hippoglossus stenolepis) using the Pacific Decadal Oscillation as the environmental variable. From these applications, the herring stock–recruitment relationships were found to vary significantly during different regimes, whereas this was not the case for halibut. However, in both instances, the fuzzy logic approach demonstrated that density-dependent effects differed between regimes. The fuzzy logic model consistently outperformed traditional approaches as measured by several diagnostic criteria. Because fuzzy logic models address uncertainty better than traditional approaches, they have the potential to improve our ability to understand factors influencing stock–recruitment relationships and thereby manage fisheries more effectively.

Characterization of rainbow trout cell lines using microsatellite DNA profiling.

Ten microsatellite loci (Omy27DU,Omy325(A3)UoG, OmyFGT5TUF,OmyFGT14TUF, OmyFGT15TUF,OmyFGT23TUF, Omy77DU,Ssa20.19NUIG, Ots1BML, andOne18ASC) were amplified using the polymerase chain reaction to create genetic profiles for nine cell lines (RTG-2, RTH-149,RTL-W1,RTgill-W1, RTS-11, RTS-34st, RTP-2, RTP-91E and RTP-91F) from rainbow trout(Oncorhynchus mykiss) and one cell line (CHSE-214) from Chinook salmon (O. tschawytscha). A cell line (PHL) from anon-salmonid, the Pacific herring (Clupea harengus pallasi), was included as a control. The ten loci clearly revealed the uniqueness of each cell line, except for two cell lines (RTP-91E andRTP-91F) from the same fish. RTP-91E and RTP-91F were identical at all loci except Ssa20.19NUIG. The most useful locus for demonstrating uniqueness was Ots1BML. The information was used to demonstrate that an uncharacterized rainbow trout cell line (Clone 1A)was in fact CHSE-214, illustrating the usefulness of multiplexed microsatellites for the creation of genetic profiles for salmonid cell lines and for the testing of cell line cross-contamination.

Nearshore Fish Distributions in an Alaskan Estuary in Relation to Stratification, Temperature and Salinity

Fish were sampled with beach seines and small-meshed beam trawls in nearshore (<1km) and shallow (<25m) habitats on the southern coast of Kachemak Bay, Cook Inlet, Alaska, from June to August, 1996–1998. Fish distributions among habitats were analysed for species composition, catch-per-unit-effort (CPUE) and frequency of occurrence. Two oceanographically distinct areas of Kachemak Bay were sampled and compared: the Outer Bay and the Inner Bay. Outer Kachemak Bay is exposed and receives oceanic, upwelled water from the Gulf of Alaska, whereas the Inner Bay is more estuarine. Thermohaline properties of bottom water in the Outer and Inner Bay were essentially the same, whereas the Inner Bay water-column was stratified with warmer, less saline waters near the surface.Distribution and abundance of pelagic schooling fish corresponded with area differences in stratification, temperature and salinity. The Inner Bay supported more species and higher densities of schooling and demersal fish than the Outer Bay. Schooling fish communities sampled by beach seine differed between the Outer and Inner Bays. Juvenile and adult Pacific sand lance (Ammodytes hexapterus), Pacific herring (Clupea harengus pallasi), osmerids (Osmeridae) and sculpins (Cottidae) were all more abundant in the Inner Bay. Gadids (Gadidae) were the only schooling fish taxa more abundant in the Outer Bay. Thermohaline characteristics of bottom water were similar throughout Kachemak Bay. Correspondingly, bottom fish communities were similar in all areas. Relative abundances (CPUE) were not significantly different between areas for any of the five demersal fish groups: flatfishes (Pleuronectidae), ronquils (Bathymasteridae), sculpins (Cottidae), gadids (Gadidae) and pricklebacks (Stichaeidae).

Primary structure and function of three gonadotropin-releasing hormones, including a novel form, from an ancient teleost, herring.

The evolution of GnRH and the role of multiple forms within the brain are examined. Three forms of GnRH were purified from the brain of Pacific herring (Clupea harengus pallasi) and characterized using Edman degradation and mass spectrometry. Two forms correspond with the known structures of chicken GnRH-II and salmon GnRH that are found in many vertebrate species. The third form, designated herring GnRH (hrGnRH), has a primary structure of pGlu-His-Trp-Ser-His-Gly-Leu-Ser-Pro-Gly-NH2. This novel peptide is a potent stimulator of gonadotropin II and GH release from dispersed fish pituitary cells. The content of hrGnRH in the pituitary was 8-fold that of salmon GnRH and 43-fold that of chicken GnRH-II, which provides supporting evidence that hrGnRH is involved in the release of gonadotropin. Herring is the most phylogenetically ancient animal in which three forms of GnRH have been isolated and sequenced. Our evidence suggests that the existence of three GnRHs in the brain of one species 1) is an ancestral condition for teleosts, 2) has the potential for separate regulation of the distinct GnRHs, and 3) may be an evolutionary advantage for refined control of reproduction in different environments.

Relative sensitivity of marine species to an effluent with elevated total dissolved solids

AbstractThe acute toxicity of aged gold mill effluent was compared for two reference species (juvenile mysid shrimp [Mysidopsis bahia (Americamysis bahia)] and larval sheepshead minnows [Cyprinodon variegatus]) and larvae of three species that are indigenous to the southern coast of Alaska (red king crab [Paralithodes camtschaticus], northern shrimp [Pandalus borealis], and Pacific herring [Clupea harengus pallasi]). Effluent osmolality was equivalent to that of 12 ppt seawater. Concentration–response relationships for the effluent, adjusted to equal the osmolality and pH of 31 ppt seawater, were determined after 24 h of exposure for immobility, paralysis, and death. The magnitude of differences and rank of sensitivity of the indigenous species depended on the response that was used for the comparison. For all responses, M. bahia and C. variegatus were the most and least sensitive species, respectively.

Successful aquatic animal disease emergency programmes.

The authors provide examples of emergency programmes which have been successful in eradicating or controlling certain diseases of aquatic animals. The paper is divided into four parts. The first part describes the initial isolation of viral haemorrhagic septicaemia (VHS) virus in North America in the autumn of 1988 from feral adult chinook (Oncorhynchus tshawytscha) and coho salmon (O. kisutch) returning for spawning. The fish disease control policies at both State and Federal levels in the United States of America required quarantine and emergency eradication measures upon the finding of certain exotic fish pathogens, including VHS virus. The procedures for emergency plans, destruction of stocks and disinfection of facilities are described, as well as challenge experiments with the North American strains of VHS virus and the detection of the virus in marine fish species (cod [Gadus macrocephalus] and herring [Clupea harengus pallasi]) in the Pacific Ocean. The second part of the paper outlines the aquatic animal legislation in Great Britain and within the European Union, in regard to contingency plans, initial investigations, action on the suspicion of notifiable disease and action on confirmation of infection. The legal description is followed by an account of an outbreak of viral haemorrhagic septicaemia in turbot (Scophthalmus maximus) in Great Britain, including the stamping-out process at the affected farm and investigations conducted to screen other farms in the vicinity for possible infection. The third part provides a historical review of the build-up of infectious salmon anaemia (ISA) in Norway and the attempts to control the disease using legal measures in the absence of detailed knowledge of the aetiology, epizootiology, pathogenesis, etc. of the disease. The measures taken show that the spread of ISA can be controlled using restrictions on the movement of fish, disinfection procedures, etc. However, acceptance and understanding of the chosen strategy by the fish farmers is a pre-requisite to reach that goal. Finally, the paper summarises future needs for national and international legislation, including the development of standard approaches for control, the creation of appropriate infrastructures and a better understanding of the epidemiology of aquatic animal diseases.

SPOILAGE AND HISTAMINE IN WHOLE PACIFIC HERRING (CLUPEA HARENGUS PALLASI) AND PINK SALMON (ONCORHYNCHUS GORBUSCHA) FILLETS

ABSTRACT Fresh pink salmon (Oncorhynchus gorbuscha) fillets and whole Pacific herring (Clupea harengus pallasi) were stored for two weeks at 10C to determine if significant amounts of histamine were produced before the fish spoiled. Spoilage odors in salmon were moderate by day 4 and intense by day 7, while herring had detectable spoilage by day 4 and became potent by day 6. Aerobic bacterial counts increased from 4.0 × 102/g initially to 3.6 × 108/g in salmon fillets by day 14 and from 2.3 × 103/g initially to 2.7 × 107/g in whole herring by day 14. Total volatile nitrogen increased from 1.8 to 78.5 mg N/100 g in salmon and 2.2 to 23.6 mg N/100 g in herring. Histamine was not detected in salmon, while concentrations reached 54.9 ppm in herring at day 14. However, herring were considered spoiled by day 6.

Development and characterization of a cell line from Pacific herring, Clupea harengus pallasi, sensitive to both naphthalene cytotoxicity and infection by viral hemorrhagic septicemia virus.

A cell line, PHL, has been successfully established from newly hatched herring larvae. The cells are maintained in growth medium consisting of Leibovitz's L-15 supplemented with 15% fetal bovine serum (FBS), and have been cryopreserved and maintain viability after thawing. These cells retain a diploid karotype after 65 population doublings. PHL are susceptible to infection by the North American strain of viral hemorrhagic septicemia (VHS) virus, and are sensitive to the cytotoxic effects of naphthalene, a common environmental contaminant. Naphthalene is a component of crude and refined oil, and may be found in the marine environment following acute events such as oil spills. In addition, chronic sources of naphthalene contamination include offshore drilling and petroleum contamination from areas such as docks and marinas that have creosote-treated docks and pilings and also receive constant small inputs of petroleum products. This cell line should be useful for investigations of the toxicity of naphthalene and other petroleum components to juvenile herring. In addition, studies of the VHS virus will be facilitated by the availability of a susceptible cell line from an alternative species.

GRAY WHALE (ESCHRICHTIUS ROBUSTUS) HABITAT UTILIZATION AND PREY SPECIES OFF VANCOUVER ISLAND, B. C.

AbstractHabitat utilization and prey species of Vancouver Island gray whales were investigated by (1) summarizing 26 yr of distribution and feeding data and (2) conducting intensive observations in Clayoquot Sound, Vancouver Island, from 1989 to 1996. Whale distribution and movements were monitored from March to November through systematic boat surveys and whale‐watch sighting programs. Prey species were collected by suction hose and plankton net or determined through analysis of fecal samples. Gray whales utilized virtually all of the southern west coast of Vancouver Island over the 26‐yr observation period. Distribution, prey species, and feeding behavior showed marked variability during any one season and between years. Some feeding areas were used on an annual basis, others with &gt;10‐yr intervals between use. Feeding occurred in shallow sand or mud bays, eel grass beds, kelp beds, in the open water column, and at the surface. Young whales appeared to utilize habitat and prey species differently than adults. Main prey species included herring eggs/larvae (Clupea harengus pallasi), crab larvae (Cancer magistermegalops,Pachycbelesspp. zoea), mysids (Holmesimysis sculpta, Neomysis rayii, Acanthomysisspp.), amphipods (Ampeliscaspp.,Atylus borealis), and ghost shrimp (Callianassa californiensis). The definition and relative importance of specific feeding grounds and the study of human impacts on this population are complicated by its broad and variable use of habitat and prey species.

Fishes and the Forest

E very year, millions upon millions of anadromous fish come from the oceans to spawn in freshwater streams. In Southeast Alaska alone, these fish spawn in over 5000 streams (Halupka et al. in press). The best-known anadromous on the Pacific coast are the seven species of Pacific salmon of the genus Oncorhynchus (including steelhead, Oncorhynchus mykiss, and sea-run cutthroat trout, Oncorhynchus clarki). Other, less-publicized and less well studied anadromous species include the chars (Salvelinus spp.) and smelt, such as the eulachon (Thaleichthys pacificus). In addition to anadromous species, several species of fully marine forage fishes use interand subtidal zones. For example, along the north Pacific coast, Pacific herring (Clupea harengus pallasi) spawn on rocky coastlines, and Pacific sand lance (Ammodytes hexapterus) can be found buried in soft sands, often near the mouths of streams. These teeming hordes of fish fall prey not only to marine hunters, such as other fish, whales, and sea lions, but also to numerous terrestrial predators and scavengers. Historically, the predators were seen as competing with human harvesters of fish, and predator-control programs aimed at reducing the number of

Pheromone-Induced Spawning of Pacific Herring

A spawning pheromone in the milt (semen) and testes of the Pacific herring,Clupea harengus pallasi,is thought to facilitate school spawning of this species. We found that responsiveness to the spawning pheromone was variable among ripe fish (milt-producing or ovulated). Measurement of five principle reproductive steroids in the free form and five steroids in conjugated forms in the plasma of male fish early in the spawning season (newly ripe fish) showed that elevated plasma levels of 3α,17α-dihydroxy-5β-pregnan-20-one and 17α-hydroxyprogesterone coincided with responsiveness to the spawning pheromone in these fish; levels of other steroids did not differ. In contrast, responsiveness to the pheromone by female fish later in the spawning season (ripe-and-holding fish) coincided with lower levels of glucuronated 17α,20β-dihydroxyprogesterone and a lower gonadosomatic index. We suggest that these differences indicate a more advanced mature reproductive state in the responsive individuals among both the newly ripe male and the ripe-and-holding female fish. We found no differences in the level of cortisol in the blood of the herring that could be correlated with differences in pheromonal responsiveness. We conclude that differences in responsiveness to the spawning pheromone coincide to some extent with levels of reproductive maturation but probably not with recent stress.

Pheromone-Induced Spawning of Pacific Herring

A spawning pheromone in the milt (semen) and testes of the Pacific herring,Clupea harengus pallasi, triggers spawning in sexually mature fish of both sexes and is thought to facilitate school spawning of this species. We found the response to the pheromone to be a stereotyped behavioral sequence consisting of a graded extension of the gonadal papilla, release of gametes, and spawn deposition behavior. The response is triggered by an olfactory stimulus, as demonstrated by the elimination of the response by occlusion of the nares. Stimulus concentrations of an approximate 1:500 dilution of fresh milt or the equivalent of 0.02 g of fully mature testes per milliliter were required to elicit a response in 50% of ripe herring that are responsive to the pheromone. Female fish appeared to be less sensitive to the pheromone in milt than males early in the spawning season, but not thereafter. The average duration of responses of male fish was longer after exposure to concentrated milt than to testes extracts, but no consistent difference in response times of the two sexes was detected. Factors other than the spawning pheromone, maturity of the fish, and stress also were found to influence the spawning response. For example, exposure to shallow (3 cm) water in a small tank induced “spontaneous” papilla extension and spawning approximately 20 min after refilling the tank; occluding the nares prevented this response. Also, the presence of floating kelp (Macrocystis) resulted in prolonged spawning in a large tank after pheromonal stimulation.

The behavior of Pacific herring schools in response to artificial humpback whale bubbles

There have been numerous reports of humpback whales and other marine predators deploying bubbles during foraging activities. However, the effects of bubbles on schooling prey organisms remain poorly understood. We conducted a series of laboratory experiments to gain insight into the effect of bubbles on the Pacific herring, Clupea harengus pallasi, a principal prey species of the humpback whale, Megaptera novaeangliae. The fish exhibited strong avoidance of bubbles and could be contained within a circular bubble net. The herring schools were also reluctant to swim through a curtain of bubbles even when frightened. However, herring were much more willing to cross a bubble curtain or net if there was a larger aggregation of fish on the opposite side. Individuals and small groups of herring also waited for less time before crossing than did larger groups. These experiments suggest that herring have a strong fear of bubbles and can readily be manipulated or contained within bubble nets by predators.