Pacific Cod Gadus Macrocephalus Research Articles

Distribution of pacific cod Gadus macrocephalus (Gadidae) and functional structure of the habitat in the northern Japan Sea and some issues on regulation of the fishery

Seasonal and bathymetric distribution of the main age groups of pacific cod in the northern Japan Sea are considered on the data of bottom trawl surveys in 1980–2023. The main wintering and spawning accumulations, where the fish concentrate from December to January and then spawn in February-March, are formed on the external shelf and the upper continental slope along the western coast approximately between Peter the Great Bay and 47о N and along the eastern coast between Cape Krillon and 47о 30′N. The juveniles have feeding migrations from April to May, while older age groups complete the migrations a month later. They migrate in three main directions: from the areas at the mainland coast – southwestward and northeastward and from the areas at western Sakhalin — southward. The juveniles feed on shallows in Peter the Great Bay, northern Tatar Strait, and on southwestern shelf of Sakhalin between the Nevelsky Bay and Cape Krillon, whereas the feeding grounds for older groups occupy two vast areas including Peter the Great Bay with the adjacent southeastern shelf of Primorye and the shelf of northern Primorye in the Tatar Strait (to the north from 47о N) with the whole shelf of Sakhalin. In the northern Tatar Strait (northward from 48о N), the cod belonged to the Primorye and Sakhalin stocks can feed together. The feeding season lasts from June to September. The older cod feed usually deeper that the juveniles. Back migrations of cod for wintering occur from October to November. Because of a joint feeding area where the mainland and Sakhalin stocks are able to mix, the bottom trawl surveys at Primorye coast cannot be used for correct assessment of the total available catch (TAC) in this fishing district. To improve quality of the cod fishery forecasts, the methods of cohort or production analyses should be used, with the control by bottom trawl surveys data, as alternative information about the state of cod stocks, taking into account the abovementioned patterns of seasonal distribution and migrations.

Development of a MGB probe based qPCR protocol for detecting Pacific cod Gadus macrocephalus in eDNA samples

Development of a MGB probe based qPCR protocol for detecting Pacific cod Gadus macrocephalus in eDNA samples

ЭКОЛОГИЯ ПИТАНИЯ СИВУЧА С РЕПРОДУКТИВНОГО ЛЕЖБИЩА НА МЫСЕ КОЗЛОВА (ВОСТОЧНАЯ КАМЧАТКА)

We studied the Steller's sea lion Eumetopias jubatus feeding ecology based on undigested food items found in feces at the Kozlova Cape rookery, Eastern coast of Kamchatka Peninsula, in summers (2004 through 2008). Atka mackerel Pleurogrammus monopterygius and walleye pollock Theragra chalcogramma were dominant in a sea lion diet hauled out at Kozlova Cape rookery in terms of frequency of occurrence. Less frequently occurred were Pacific sand lance Ammodytes hexapterus, Threespine stickleback Gasterosteus aculaeatus, Smelt Osmerus mordax, Sculpins Cottidae, Pacific sandfish Trichodon trichodon, Flatfishes Pleuronectidae, Salmon Oncorhynchus sp., Pacific cod Gadus macrocephalus, and Squid and Octopus Cephalopoda. The contribution of the other food items was not significant. Diet diversity median during sea lion single foraging trip was two prey items, range being one to nine Atka mackerel and Walleye pollock as the major prey objects. Most of sea lion food items were referred to species featuring a marked seasonal presence near the shore or on the shelf. Sea lions feed near the rookery close to the shore on seasonal food aggregations common to the area. Seasonal prey aggregations can be extremely important for breeding animals due to increasing the efficiency of food search and capture, which in turn can affect the reproductive success of animals and their survival. In this regard, the stability of the food resource near Kozlova Cape Rookery may influence sea lion population status there.

Importance of fish species in the bottom and near-bottoml biotopes of the Far-Eastern Seas and Pacific waters of Russia

Importance of fish species in the benthal ichthyocoenoses (up to depths of 2000 m) is discussed for the Russian waters in the Far-Eastern Seas and adjacent North-West Pacific on the data of bottom trawl surveys conducted by Pacific Fish. Res. Inst. (TINRO) in 1977–2010. The inverse Simpson index (or polydominance index) was chosen as a measure of dominance; Sorensen-Chekanovsky similarity index was used for comparative analysis of the dominance structure in ichthyocoenoses. The importance is determined for the top 20 species ranked by biomass (94.9 % of the total biomass of all demersal fish on the shelf and 95.8 % — at the continental slope, on average). Poor evenness under strong domination of 2–4 species is noted in the fish communities within the range of 0–2000 m. Walleye pollock Theragra chalcogramma dominate in all regions whereas the subdominants are pacific herring Clupea pallasii, pacific cod Gadus macrocephalus, atka mackerel Pleurogrammus monopterygius, or okhotsk atka mackerel P. azonus, depending on the region. The pollock domination is interrupted at the continental slope of the Bering Sea, where giant grenadier Albatrossia pectoralis dominate. The subdominants at the continental slope of all regions are greenland halibut Reinhardtius hippoglossoides matsuurae, popeye grenadier Coryphaenoides cinereus, pacific herring, pacific sleeper shark Somniosus pacificus, scale-eye plaice Acanthopsetta nadeshnyi, and blackfin flounder Glyptocephalus stelleri. Generalized graphs of the ichthyocoenoses similarity between the studied regions (Okhotsk Sea, Bering Sea, Japan Sea, and Pacific waters at Kamchatka and Kuril Islands) by species structure and composition of the dominant species are presented, separately for the shelf and continental slope.

Shifting fish distributions impact predation intensity in a sub‐Arctic ecosystem

An abundance of studies in marine systems have documented species range shifts in response to climate change, and many more have used species distribution models to project species ranges under future conditions. However, there is increasing interest in moving beyond a single‐species focus to understand how species redistribution alters ecosystem dynamics via changes in trophic interactions. We employed spatiotemporal models to characterize decadal‐scale changes in spatial overlap between the distribution of juvenile walleye pollock Gadus chalcogrammus and the distributions of four of its groundfish predators: arrowtooth flounder Atheresthes stomias, Pacific cod Gadus macrocephalus, Pacific halibut Hippoglossus stenolepis and adult walleye pollock. These fishes represent ecologically and commercially important species in a rapidly changing sub‐Arctic ecosystem, the eastern Bering Sea, Alaska, USA. We then examined whether changes in spatial overlap corresponded to changes in predation, using spatiotemporal models of predator stomach contents. We found marked shifts in spatial overlap between juvenile pollock and two predators (arrowtooth flounder and Pacific halibut) over 34 years, with changes in overlap corresponding to increases in population‐scale predation pressure. By contrast, we did not find clear relationships between spatial overlap and predation for Pacific cod and adult pollock, the two predators for which juvenile pollock constitute a much smaller diet proportion. Our findings highlight the complexity of predicting predation dynamics for generalist marine species and suggest a need for better process‐based methods for understanding the potential future ecological impacts of coupled species range shifts. However, simple metrics of spatial overlap between relatively specialized predators and their prey offer promise as a means to integrate predictions from species distribution models into ecosystem‐based fisheries management.

An ensemble approach to understand predation mortality for groundfish in the Gulf of Alaska

There is increasing consensus of the need for ecosystem-based fisheries management (EBFM), which accounts for trophic interactions and environmental conditions when managing exploited marine resources. Continued development and testing of analytical tools that are expected to address EBFM needs are essential for guiding the management of fisheries resources in achieving and balancing multiple social, economic, and conservation objectives. To address these needs, we present and compare alternative climate-informed multi-species statistical catch-at-age models to account for spatio-temporal differences in stock distributions, with application to four groundfish species (walleye pollock Gadus chalcogrammus, Pacific cod Gadus macrocephalus, arrowtooth flounder Atheresthes stomias, and Pacific halibut Hippoglossus stenolepis) in the Gulf of Alaska, USA. We integrate across multiple forms of uncertainty regarding the data and distribution of Pacific halibut using an ensemble modelling approach. Models developed here can be used to supplement current tactical fisheries management and inform on the trade-offs between harvesting across groundfish in the Gulf of Alaska. This approach may be applicable for other situations where spatial and temporal overlap is extensive among closely coupled species.

ЛЕТНЕЕ ПИТАНИЕ СИВУЧА В ВОДАХ ДАЛЬНЕГО ВОСТОКА РОССИИ В 2004–2008 ГОДАХ

The diet of Steller sea lion Eumetopias jubatus was studied based on undigested food parts found in feces collected in the summer season on 20 rookeries in the Russian Far East. A total of 915 samples were analyzed between 2004 and 2008, in which 65 food items were identified. The frequency of occurrence of 11 diet items was greater than 5%, including Atka mackerel Pleurogrammus monopterygius (64.8%), Pollock Theragra chalcogramma (44.3%), Pacific salmon Salmonidae (20.5%), Irish lord Hemilepidotus sp. (20.4%), Pacific sand lance Ammodytes hexapterus (15.8%), Pacific herring Clupea pallasi (9.5%), Squid and Octopus Cephalopoda (8.4%), Pacific cod Gadus macrocephalus (5, 9%), Pacific sandfish Trichodon trichodon (5.9%), Flatfishes Pleuronectidae (5.8%), Threespine stickleback Gasterosteus aculaeatus (4.9%). Three regions with different diets were identified – the Sea of Okhotsk, the Kuril Islands, and Kamchatka with the Commander Islands. In the Sea of Okhotsk, Pollock and Herring (83.6% by frequency of occurrence) dominated among undigested food remains in feces. The diet at the Kuril Islands rookeries was variable within the region. The general pattern was a low diversity of diet at each Kuril Island sites and predominance of 1-3 food items, probably the most accessible near the sites (Pollock, Squid and Octopus, Atka mackerel, Pacific salmon). The diet pattern in Kamchatka and the Commander Islands in the summer season was characterized by a high diet diversity. In contrast to other regions, the diet includes in high proportion small non-commercial species – Sand lance, Irish lord, Pacific sandfish, Flatfishes, Threespine stickleback and others. The regional patterns of sea lion diets show the spatial distribution and areas of abundant biomass of the main food items. The diet patterns of sea lions from rookeries differed from haulouts in having a higher content of abundant food items. Long-term changes in diet structure were not statistically significant.

Using a climate attribution statistic to inform judgments about changing fisheries sustainability

Sustainability—maintaining catches within the historical range of socially and ecologically acceptable values—is key to fisheries success. Climate change may rapidly threaten sustainability, and recognizing these instances is important for effective climate adaptation. Here, we present one approach for evaluating changing sustainability under a changing climate. We use Bayesian regression models to compare fish population processes under historical climate norms and emerging anthropogenic extremes. To define anthropogenic extremes we use the Fraction of Attributable Risk (FAR), which estimates the proportion of risk for extreme ocean temperatures that can be attributed to human influence. We illustrate our approach with estimates of recruitment (production of young fish, a key determinant of sustainability) for two exploited fishes (Pacific cod Gadus macrocephalus and walleye pollock G. chalcogrammus) in a rapidly warming ecosystem, the Gulf of Alaska. We show that recruitment distributions for both species have shifted towards zero during anthropogenic climate extremes. Predictions based on the projected incidence of anthropogenic temperature extremes indicate that expected recruitment, and therefore fisheries sustainability, is markedly lower in the current climate than during recent decades. Using FAR to analyze changing population processes may help fisheries managers and stakeholders to recognize situations when historical sustainability expectations should be reevaluated.

Estimating spatiotemporal availability of transboundary fishes to fishery‐independent surveys

Abstract Taxa can expand beyond historical scientific survey footprints and into new areas with different survey protocols as they move to track their preferred climate. In global groundfish fisheries, for example, scientists estimate population dynamics within the spatial extent of a fishery‐independent survey using an index known as a design‐based estimator. Observed changes in species distribution in recent years suggest that some groundfish are moving beyond the spatial extent of single surveys. We must intercalibrate disparate data that cover a larger spatial extent to maintain our ability to accurately index populations as their availability to historical surveys changes. We combine US and Russian data from the northern, eastern and western Bering Sea to understand the proportion of fish biomass within the extent of the eastern survey (‘availability’). Surveys are within close proximity to each other, but with different sampling protocols (hence catch a different proportion of local densities, termed ‘sampling efficiency ratio’). We use Alaska pollock Gadus chalcogrammus, Pacific cod Gadus macrocephalus and Alaska plaice Pleuronectes quadrituberculatus as case studies to calculate survey efficiency ratios and two area‐swept estimators, termed local and conventional, to summarize groundfish biomass over various spatial scales across the Bering Sea. We estimated variation in spatial availability of transboundary stocks to the eastern Bering Sea (EBS) survey. In 2017, the most recent available year of survey coverage that included all three Bering Sea regions, estimated availability in the EBS of pollock biomass was ~33%, cod biomass was ~27% and plaice biomass was ~26%, down from ~58%, ~71% and ~30%, respectively, in 2010. Synthesis and applications. This is the first study to provide an empirical way to combine Russian and US data in the Bering Sea to assess changes in the availability of groundfish biomass, which, in turn, will alter the interpretations and values of population indices used in regional management. We recommend leveraging this approach using existing global fishery‐independent datasets that span different spatiotemporal footprints to monitor transboundary stocks, and as a template to initiate international cooperation on the assessment of spatial availability of stocks common to multiple countries.

Seasonal migratory patterns of Pacific cod (Gadus macrocephalus) in the Aleutian Islands

BackgroundPacific cod (Gadus macrocephalus) is an ecologically important species that supports a valuable commercial fishery throughout Alaska waters. Although its life history includes seasonal movement for spawning and feeding, little is known about its movement ecology. Here, we present results from the first study to use pop-up satellite archival tags (PSATs) to track the within-year movements of Pacific cod to understand their potential seasonal movement patterns within the Aleutian Islands. This study was part of a cooperative research project; tagging was conducted onboard commercial vessels during the winter fishing season while Pacific cod were aggregated to spawn in the central Aleutian Islands.ResultsOf the 36 PSATs deployed, we were able to obtain movement data from 13 Pacific cod that were at liberty between 60 and 360 days. We determined that three tagged Pacific cod were predated on by marine mammals and three were recaptured by the commercial fishery. Geolocation models were produced for four migrating individuals. Eight Pacific cod moved to a productive foraging ground near Seguam Island located 64 to 344 km from their release site and presumed spawning ground within a few weeks of their release. These movements indicate that some Pacific cod in the Aleutian Islands undergo seasonal migration. Three Pacific cod remained near their release locations (within 50 km) for more than 75 days suggesting the existence of partial migration in the population. Two Pacific cod undertook larger movements (378 and 394 km) during which they swam over deep passes and crossed several management boundaries highlighting the potential connectedness of Pacific cod throughout the Aleutian Islands.ConclusionsThis study provided important initial insights into the seasonal movement patterns of Pacific cod in the Aleutian Islands. Most tracked Pacific cod (77%) undertook migrations in the middle of March (64–394 km) from their winter spawning areas to summer foraging areas, but a few individuals remained in their capture location suggesting a partial migration strategy. Their ability to cross deep passes that were previously seen as potential barriers to movement has expanded our understanding of population connectivity.

A Dynamic Stress-Scape Framework to Evaluate Potential Effects of Multiple Environmental Stressors on Gulf of Alaska Juvenile Pacific Cod

Quantifying the spatial and temporal footprint of multiple environmental stressors on marine fisheries is imperative to understanding the effects of changing ocean conditions on living marine resources. Pacific Cod(Gadus macrocephalus), an important marine species in the Gulf of Alaska ecosystem, has declined dramatically in recent years, likely in response to extreme environmental variability in the Gulf of Alaska related to anomalous marine heatwave conditions in 2014–2016 and 2019. Here, we evaluate the effects of two potential environmental stressors, temperature variability and ocean acidification, on the growth of juvenile Pacific Cod in the Gulf of Alaska using a novel machine-learning framework called “stress-scapes,” which applies the fundamentals of dynamic seascape classification to both environmental and biological data. Stress-scapes apply a probabilistic self-organizing map (prSOM) machine learning algorithm and Hierarchical Agglomerative Clustering (HAC) analysis to produce distinct, dynamic patches of the ocean that share similar environmental variability and Pacific Cod growth characteristics, preserve the topology of the underlying data, and are robust to non-linear biological patterns. We then compare stress-scape output classes to Pacific Cod growth rates in the field using otolith increment analysis. Our work successfully resolved five dynamic stress-scapes in the coastal Gulf of Alaska ecosystem from 2010 to 2016. We utilized stress-scapes to compare conditions during the 2014–2016 marine heatwave to cooler years immediately prior and found that the stress-scapes captured distinct heatwave and non-heatwave classes, which highlighted high juvenile Pacific Cod growth and anomalous environmental conditions during heatwave conditions. Dominant stress-scapes underestimated juvenile Pacific Cod growth across all study years when compared to otolith-derived field growth rates, highlighting the potential for selective mortality or biological parameters currently missing in the stress-scape model as well as differences in potential growth predicted by the stress-scape and realized growth observed in the field. A sensitivity analysis of the stress-scape classification result shows that including growth rate data in stress-scape classification adjusts the training of the prSOM, enabling it to distinguish between regions where elevated sea surface temperature is negatively impacting growth rates. Classifications that rely solely on environmental data fail to distinguish these regions. With their incorporation of environmental and non-linear physiological variables across a wide spatio-temporal scale, stress-scapes show promise as an emerging methodology for evaluating the response of marine fisheries to changing ocean conditions in any dynamic marine system where sufficient data are available.

Maturation and Spawning of the Pacific Cod Gadus macrocephalus in the West Coast of Yellow Sea of Korea

Maturation and Spawning of the Pacific Cod Gadus macrocephalus in the West Coast of Yellow Sea of Korea

Effect of Different Rotifer Enrichment Products on Survival, Growth, and Fatty Acid Composition of Larval Pacific Cod Gadus macrocephalus

Effect of Different Rotifer Enrichment Products on Survival, Growth, and Fatty Acid Composition of Larval Pacific Cod Gadus macrocephalus

IgE reactivity to fish allergens from Pacific cod (Gadus macrocephalus) in atopic dogs

BackgroundIgE reactivity to fish allergens in atopic dogs, which are used as models for food allergy, has not been elucidated to date. We investigated IgE reactivity to crude extracts and purified allergens derived from the Pacific cod (Gadus macrocephalus) in atopic dogs to identify the allergenic proteins of cod.ResultsThe levels of specific IgE to crude cod extracts were measured in the sera of 179 atopic dogs, including 27 dogs with cod allergy, using enzyme-linked immunosorbent assay (ELISA). Specific IgE to crude cod extracts were present in 36 (20%) of the 179 atopic dogs and in 12 (44%) of the 27 dogs with cod allergy. The allergens in crude cod extracts were analyzed by ELISA, immunoblotting, and liquid chromatography-tandem mass spectrometry. In allergen component analysis, IgE reactivity to tropomyosin and enolase was observed in the sera of dogs with cod allergy. IgE reactivity to parvalbumin, collagen, and tropomyosin was evaluated using the sera of atopic dogs that tested positive for specific IgE to crude cod extracts. Among the 36 dogs with IgE reactivity to crude cod extracts, 9 (25%), 14 (39%), and 18 (50%) dogs tested positive for specific IgE to parvalbumin, collagen, and tropomyosin, respectively.ConclusionsThe IgE reactivity to cod allergens observed in dogs was similar to that in humans, and this finding further supports the use of atopic dogs with fish allergy as a model for fish allergy in humans.

Examining the ecological role of jellyfish in the Eastern Bering Sea

AbstractWithin the Eastern Bering Sea, the jellyfish Chrysaora melanaster has fluctuated widely over recent decades. We examined the role of C. melanaster as an ecosystem-structuring agent via application of ecosystem models representing inner-, mid-, and outer-shelf regions of comparable areal coverage. Chrysaora melanaster utilize 1% of total mid-shelf consumer production, or 1/4th the energy required by forage fish (capelin Mallotus villosus, Pacific herring Clupea pallasii, age-0 Pacific cod Gadus macrocephalus, age-0 walleye pollock Gadus chalcogrammus). Model simulations show the impacts of C. melanaster are broadly distributed across consumer groups with increasingly negative impacts with higher jellyfish biomass. Age-0 pollock represent the greater part of the forage fish biomass, and observed pollock biomass during low jellyfish years (2004–2007) was significantly greater than during high jellyfish years (2009–2014). However, sensitivity among consumer groups to observed jellyfish variability is small, within 5% of baseline (2004–2015) conditions. Estimates using similar models for the Coastal Gulf of Alaska (CGoA) and Northern California Current (NCC) suggest large differences in the role of scyphozoans among northern Pacific shelf ecosystems. Only 0.1% of total summer consumer production is required to support CGoA Chrysaora, while the coastal NCC population uses 19%.

Sexual Maturation and Sex Ratio in Pacific Cod Gadus macrocephalus (Gadidae) in Waters of Primorye (Sea of Japan)

Fifty percent of Pacific cod Gadus macrocephalus males reach sexual maturity in waters of Primorye at the age of 2+, while the age of female sexual maturation is 4+; 100% sexual maturation occurs at the age of 6+ and 7+, respectively. According to the long-term average data, the general number of males is 1.2 times larger than that of females in the population; among mature individuals, the number males is 1.7 times larger than females, which is required for successful spawning.

Influences of temperature, predators, and competitors on polar cod (Boreogadus saida) at the southern margin of their distribution

Polar cod (Boreogadus saida) is the most abundant and ubiquitous fish species throughout the Arctic Ocean. As such, they serve an important ecosystem role linking upper and lower trophic levels and transferring energy between the benthic and pelagic realms. Our objective is to explore what limits the southern distribution of polar cod in Pacific and Atlantic sectors by examining time series of survey and oceanographic data. We quantify the variability in the southern extent of the polar cod distribution in the Bering and Labrador Seas, and determine mechanisms (bottom temperature and potential predators: Pacific cod Gadus macrocephalus, Atlantic cod Gadus morhua, and Greenland halibut Reinhardtius hippoglossoides and competitors: capelin Mallotus villosus and walleye pollock Gadus chalcogrammus) driving the variability. When temperatures were lower, polar cod occupied larger areas and had higher abundances in both regions, suggesting that as temperatures increase with climate warming the range of polar cod is likely to contract. Temperature had a much larger impact on polar cod abundance than competitor abundance and predator abundance, especially in the eastern Bering Sea. However, when we included data from northern and eastern Bering Sea in 2010 and 2017, polar cod were less likely to occur in warmer waters when either Pacific cod or walleye pollock were present. Northward range expansions of subarctic Pacific cod and walleye pollock may further restrict polar cod distributions.

The Population Genetic Organization of Pacific Cod Gadus macrocephalus in the North Pacific Based on Microsatellite Analysis

Six groups have been identified in the species' population structure based on the analysis of microsatellite markers' polymorphism in Pacific cod Gadus macrocephalus samples within the entire western part of the North Pacific, including waters of the Pacific coast of Canada. The first group includes cod from waters of the Yellow Sea; the second group consists of cod from the Sea of Japan (eastern coast of Korea and Peter the Great Bay); the third group combines cod from Tatar Strait and the South Kuril Islands (both Sea of Okhotsk and Pacific Ocean sides); the fourth group is formed by cod from the northwestern Sea of Okhotsk and Taui Bay; the fifth-largest group includes cod from waters off western Kamchatka, the North Kuril Islands (Sea of Okhotsk and Pacific Ocean sides), Karaginsky Bay, Navarinsky area in the Bering Sea, and Anadyr Bay; the sixth group is formed by cod from coastal waters of Canada.

우리나라 서해에서 출현하는 대구(Gadus macrocephalus)의 식성

우리나라 서해에서 출현하는 대구(Gadus macrocephalus)의 식성

Population Structure and Microevolution of Pacific Cod Gadus macrocephalus Based on the Analysis of the Control Region (mtDNA) Polymorphism

We performed a population genetic analysis of 22 Pacific cod sample sets (n = 986) based on the mtDNA control region (599 bp) polymorphism, which made it possible to specify four distinguished groups of this species: (1) within the seaward parts of the Bering Sea and Sea of Okhotsk and northern part of the Pacific Ocean, affected by the Pacific Ocean gyres; (2) coastal areas of the East/Japan Sea; (3) northern part of the Sea of Okhotsk, more similar to the second group from the East/Japan Sea by haplotype sets than to the seaward groups, despite limited reproductive contacts, special hydrological conditions, and the history of formation of the sea areas; (4) fundamentally different Pacific cod from the Yellow Sea adapted to the conditions of the shallow water area in the subtropical region.