Walleye Pollock Research Articles

Chukchi Sea — new walleye pollock fishing area

The purpose: to identification of the features of the distribution and biology of walleye pollock Gadus chalcogrammus, as well as the presentation of information on the stocks of the species and the initial stage of development of its resources in the western part of the Chukchi Sea.Methods used: to achieve this goal, we used materials from nine integrated trawl surveys carried out in 1995– 2020 on research vessels, as well as coastal studies on the Arctic coast of the Chukotka Autonomous Okrug, which analyzed data on the distribution, biology, biomass and fishery of walleye pollock.Novelty: elements of novelty are generalized modern materials on the distribution, biology and for the first time organized pollock fishery.Practical significance: the Chukchi Sea can be attributed to the most favorable areas for studying the variability of the organization of Arctic ecosystems, due to the instability of climatic conditions on Earth during the period of warming. The obtained results of studies on the distribution, biology, stocks and fishery of such a mass indicator species as walleye pollock will increase the efficiency of using the raw material base of marine fish in this reservoir.

Reproduction, stocks assessment and walleye pollock fishery in Navarin area of the Bering Sea

The aim of the work is to summarize information about the reproduction, stock dynamics and walleye pollock fishery in the Navarin region of the Bering Sea.Methods used: methods and models of the fishery science, allowing to assess the state of the stock in conditions of increased data noise and specific features of the entry of generations into the fishing stage.Result: the updated estimates of walleye pollock stock status in the Navarin region of the Bering Sea are given. The available data allow us to state that in this area of the Bering Sea there are reproductively isolated groups of winter and spring spawning walleye pollock.Novelty: it was shown that trends in the biomass dynamics of walleye pollock spawning stock in the Navarin region and the East Bering Sea stock changed synchronously in 1995–2011 and in 2019–2021. While the rest of the time, synchrony was not observed. According to the calculated data, it is expected that the biomass values may coincide for the first time in 2022.Practical significance: the results obtained provide additional grounds for refining the volume of TAC.

Walleye pollock of the Bering Sea: features of distribution and biology, stocks, fishery

The purpose of the work: to identify the features of the distribution and biology of walleye pollock Gadus chalcogrammus, as well as to provide information on the reserves and development of its resources in the Bering Sea.Methods used: to achieve the goal, data on distribution, biology, biomass and fishery of walleye pollock were analyzed.Novelty: elements of novelty are generalized modern materials on the distribution, biology, stocks and fishery of walleye pollock.Practical significance: at the present stage, the East Bering Sea and northwestern pollock populations are at the average long-term level of biomass, their annual changes largely depend on the background conditions of the natural environment and the development of the food supply, which determine the scale of fish migration from the southeastern part of the Bering Sea to the northwestern and back. In the West Bering Sea walleye pollock, there is a trend towards a gradual recovery of stocks after a period of minimum values in the late 1990s — e arly 2000s. In general, the current state of walleye pollock stocks in the Bering Sea is characterized as stable, which maintains the fishery at a relatively high level. The results obtained in this work on the characteristics of the distribution and biology of walleye pollock, the state of its stocks and fishing will improve the efficiency of using the raw material base of marine fish in the Bering Sea.

Population structure of walleye pollock within the Asian part of the range based on the analysis of various genetic markers

The aim: The aim of this work is focused on a phylogeographic analysis of the relationship between the population groups of walleye pollock Gadus chalcogrammus of the Asian part of the range.The methods: The analysis of phylogeographic analysis is based on the data of polymorphism of microsatellite markers, a fragment of the mtDNA control region (D-loop) and a fragment of the mtDNA cytochrome b gene. The newness: A comprehensive phylogeographic analysis using samples of spawning walleye pollock individuals from most of the Asian part of the range from the Sea of Japan to the northwestern Bering Sea using various genetic markers was carried out for the first time.The results: The results of the analysis of the variability of walleye pollock samples by mitochondrial markers (fragments of the cytochrome b and D-loop genes) allow us to distinguish two large population groupings within the Asian part of its range: the first one in the Sea of Okhotsk, the Sea of Japan, the waters of the Kuril Islands and southeastern Kamchatka and the second one in the Bering and Chukchi seas. Analysis of the variability of walleye pollock samples by microsatellite markers allows us to judge the absence of population groupings in the waters of the Sea of Okhotsk, the Sea of Japan, off the Kuril Islands and southeastern Kamchatka.The practical significance: When regulating pollock fishing in the Russian waters, it is necessary to establish a single total allowable catch (TAC) for each of the two superpopulations: the Sea of Okhotsk — Sea of Japan (1) and the Bering Sea (2) combining the sizes of proposed catch for walleye pollock groups belonging to each of these superpopulations.

Comparative analysis of the output products of pollock and the main commercial cod fish species

The purposeof this study is to identify general trends affecting changes in the values of the output of products from pollock and other commercial species of cod fish, and also includes a comparative analysis of the nutritional value of products from pollock and cod to provide objective recommendations to consumers of fish products.Methods used: To conduct a comparative analysis, data on the output of frozen products, reference materials and publications on the characteristics of growth, puberty, seasonal changes in biological parameters, fatness coefficient for walleye pollock, northeastern arctic and Baltic cod, Pacific cod were used. In accordance with the “Methodology for determining the consumption rates of raw materials in the production of products from aquatic organisms”, in order to compare the data, the coefficients of consumption of raw materials for the production of products were recalculated.Novelty:a comparative analysis of the change in the values of the output of products from pollock and the main commercial species of cod fish was carried out for various types of cutting in conjunction with the annual dynamics of biological parameters.Result:the general trends of changes in the output of pollock, northeastern arctic, Baltic and Pacific cod were determined. Based on the results of a comparative analysis of the nutritional value of products from pollock and cod, recommendations are presented to consumers of fish products.Practical significance: it has been established that inter-s easonal changes in the output of walleye pollock products average 0,5 %, and the output of Pacific cod changes by 5,4–5,5 %, in northeastern arctic cod the difference in output by season can reach up to 5,7 %, in Baltic cod up to 4,5 %. Cod is more depleted in the pre-spawning period, unlike pollock, so pollock processing is more rational.

Basic trophological elements of walleye pollock and its food supply

Objectives: to study the features of the trophology of pollock of different sizes, to identify the dominant species, according to which the seasonal and interannual dynamics of its food supply should be considered in plankton.Methods used: to solve the problem, TINRO databases «Zooplankton» and «Trophology» were used, which exist in the Excell format, when the methods accepted in TINRO were used as standard for collecting and processing fish feeding and plankton samples; complete processing was carried out fresh in the ship’s laboratories.Novelty: the elements of novelty are the identified and refined features of the trophology of the Sea of Okhotsk pollock, a modern assessment of the state of its food supply, calculated data on its structure divided into fractional group and species composition. For a sample of 1000 kg of each pollock size class, tables of their daily rations in kg were compiled, broken down into species for the Sea of Okhotsk and the Bering Sea and the northwestern part of the Pacific Ocean.Practical significance: materials on the trophology of walleye pollock make it possible to evaluate the food base taking into account the needs of each of its size groups, and according to the tables of their daily rations for the Sea of Okhotsk and the Bering Sea and the northwestern part of the Pacific Ocean, it is possible to quickly calculate the total need for food, and, if data on the stock of fractions, groups and dominant species are available, determine their predation, pressure on the plankton community and competition with other species.

Some issues of walleye pollock reproduction in the pacific waters adjacent to the Kamchatka peninsula and the northern Kuril Islands in 2013–2022.

Purpose: To characterize some issues of East Kamchatka pollock reproduction in the last 10 years.Methods: complex (ichthyoplankton and hydrological) surveys in the Pacific waters adjacent to the Kamchatka Peninsula and the northern Kuril Islands, surveys in the spawning center — the “North” canyon, located in Avacha Bay, layer-by-layer surveys in the canyons and on the shelf.Novelty: the currently available data on the main spawning areas of the Eastern Kamchatka pollock were supplemented, new data on the state of the spawning stock, vertical distribution of eggs at different stages of development were presented.Results: During the period under consideration, the main pollock spawning in Avacha and Kronotsky bays occurred above deep-water canyons, and on the shelf near southeastern Kamchatka and northern Kuril Islands — in the whole surveyed water area, in some years — to the south of the island Paramushir. According to the results of ichthyoplankton surveys, model calculations, the spawning stock of the Eastern Kamchatka pollock peaked in 2010, and then it gradually decreased. Currently, resources are at an average level. Horizons of the main pollock spawning in deep-water canyons change in an inter-a nnual aspect. In addition, as egg development, as a result of internal processes occurring in the canyons (internal waves), it, then rises, then falls in the underlying layers of water.Practical significance: The results of the work can be used to improve the method of assessment of the current and prospective state of stocks, justification of the TAC of the Eastern Kamchatka pollock.

TINRO research in the field of pollock complex processing technologies

The aim: To analyze the main results and achievements of Far Eastern scientists in the field of pollock complex processing.The methods: In the period from 1977 to 2002, within the framework of research work, research was carried out on the size, mass and chemical composition, safety indicators and technological properties of walleye pollock. In order to determine the nutritional significance and ways of rational use, numerous experiments were carried out, various methods and technological methods of its processing were tested.The results: In the period from 1977 to 2002, within the framework of research, the size-mass and chemical composition, safety indicators and technological properties of walleye pollock were studied. The proposed technologies for obtaining frozen, culinary, canned, salted, analogue and other products from pollock are considered.The newness: The created technologies make it possible to provide a comprehensive non-waste processing of pollock, as the ways of using all parts of the fish body have been determined. Innovative approaches and new opportunities for its rational use are shown.The practical significance: A significant part of the developed technologies has been introduced into modern production in the processing of pollock.

Modern status, formation and exploitation of walleye pollock stocks off the southern Kuril Islands

The aim of the study is analyze the state and clarify modern status of walleye pollock stocks in the southern Kuril Islands waters.Result: Strong year-classes are revealed, which determined pollock stock dynamics in the South Kuril region in the 2010s — e arly 2020s. It is shown, that the maximum pollock biomass since the early 1990s was observed in the early 2010s, and in the early 2020s decreased to the average level. The organization of fishing and the composition of pollock commercial catches off the southern Kuril Islands are differ at low and high levels of stocks.Novelty: New data on structure and pollock stocks assessment in the South Kuril region since 2011 based on the integrated surveys results are presented. Long-term data on the effectiveness of fishing and the structure of pollock commercial catches in the South Kuril zone are considered.Practical significance: The obtained estimates of the current state and structure of pollock stock will be used for short-term and long-term forecasts.Research methods: walleye pollock stocks assessment in the South Kuril region is based on the annual integrated research expeditions in accordance with the standard methods used in TINRO to monitor pollock stocks.

Reproduction, stock status and fishery for walleye pollock in Peter the Great Bay in the modern period

The aim of the study is to analyze the current state of reproduction, resources and pollock fishery in Peter the Great Bay.Result: It is shown that the increase in pollock abundance is associated with the appearance of a strong yearclass of 2014 in Peter the Great Bay. Pollock biomass has increased significantly, mass spawning has resumed in traditional spawning areas, commercial catch of pollock increased to record levels. However, during the three spawning seasons of the year-class 2014 there was no significant recruitment, so the fish stock is expected to return to a low level.Novelty: The results of scientific research conducted in the Peter the Great Bay in 2019–2022 made it possible to obtain new data on the reproduction, current state and structure of pollock stock.Practical significance: The obtained estimates of the current state and structure of pollock stock will be used for short-term and long-term forecasts.Research methods: The data of research bottom trawl and ichthyoplankton surveys and pollock catch statistics from the Industry Monitoring System (OSM «Fishing») were used.

Effects of Sprayable, Highly Adhesive Hydrophobized Gelatin Microparticles on Endoscopic Submucosal Dissection: A Swine Model

Introduction: Sprayable wound dressings containing hydrophobized microparticles (hMPs) are characterized by strong adhesiveness. We examined the effect of hMPs derived from Alaska pollock gelatin on endoscopic submucosal dissection (ESD) ulcers. Methods: (1) In an in vivo model of miniature swine gastric ESD, gastric ulcers were created by ESD and then sprayed with hMPs or untreated followed by microscopic examination. (2) In an ex vivo ESD model of resected stomach, a pinhole-shaped perforation was created on the ESD ulcer of resected stomach; hMPs were then sprayed on the perforation; and air leakage and intragastric pressure were measured. (3) In an in vivo duodenal ESD model of miniature swine, duodenal artificial ESD ulcers with pinhole-shaped perforation were examined; ulcers were classified into hMPs-sprayed and nonsprayed groups, and inflammation in the intrinsic muscle layer and serosa were compared between the groups. Results: (1) Histological observation of submucosal tissues showed a decreased number of invading inflammatory cells in hMP-sprayed tissues compared with the control in miniature swine gastric ESD (p < 0.05). In addition, the rates of anti-alpha smooth muscle actin and type I collagen positivity were significantly lower in the hMPs group than in the control group (p < 0.05). (2) Intragastric pressure could not be measured in the nonsprayed group, whereas no air leakage was observed in the sprayed group when pressurized up to 26 mm Hg in the resected stomach model. (3) The sprayed group showed suppressed inflammation of the intrinsic muscular layer and serosa in both cases compared with the nonsprayed group in miniature swine duodenal ESD (p < 0.05). Conclusions: Sprayable, tissue-adhesive hMPs are a promising medical material for intraoperative and postoperative treatment of ESD-induced wound via anti-inflammation and strong adhesiveness.

Fine-scale diversity of prey detected in humpback whale feces.

Predator diets are largely influenced by prey availability and abundance. Yet, in heterogenous marine environments, identifying the prey species consumed by diving mammals remains a fundamental challenge. For rorqual whales, the energetic constraints of prey engulfment require that the whales seek areas of high prey abundance and execute discrete lunge feeding events on patches of high-density prey. Prey occurrences in feces should therefore provide meaningful insight into the dominant taxa in food patches selected by the animal. We investigated the prey consumed by humpback whales in three regions in southern British Columbia (BC), Canada, using opportunistic fecal sampling, microscopy, and DNA metabarcoding of 14 fecal samples. Fish including Pacific herring (Clupea pallasii), hake (Merluccius productus), and eulachon (Thaleichthys pacificus) were the most common fish species potentially targeted by humpback whales in two regions. The krill Euphausia pacifica was the most prevalent invertebrate DNA detected in all three regions, while sergestid and mysid shrimp may also be important. High DNA read abundances from walleye pollock (Gadus chalcogrammus) and sablefish (Anoplopoma fimbria) were also recovered in one sample each, suggesting that juveniles of these semi-pelagic species may occasionally be targeted. In general, we observed heavily digested fecal material that drove substantial dissimilarities in taxonomic resolution between polymerase chain reaction-based and morphological analyses of the feces. Pacific herring and walleye pollock were the only prey species confirmed by both methods. Our results highlight that molecular and visual analyses of fecal samples provide a complementary approach to diet analysis, with each method providing unique insight into prey diversity.

Some Aspects of the Walleye Pollock (Theragra chalcogramma) Biology and Fishery Related to the Size and Age Structure in the Southwestern Chukchi Sea

Some Aspects of the Walleye Pollock (Theragra chalcogramma) Biology and Fishery Related to the Size and Age Structure in the Southwestern Chukchi Sea

Chronic Intake of a Meal Including Alaska Pollack Protein Increases Skeletal Muscle Mass and Strength in Healthy Older Women: A Double-Blind Randomized Controlled Trial

In animal studies, a meal containing Alaska pollack protein (APP) induces fast-twitch muscle hypertrophy. To our knowledge, no interventional studies have examined the benefits of APP intake on muscle mass and muscle weakness and the prevention of sarcopenia in older individuals. We evaluated the effects of APP intake on skeletal muscle mass, muscle strength, and physical performance among healthy community-dwelling older Japanese women. In this double-blind randomized controlled trial, healthy women ≥ 65 y old were allocated to an APP or whey protein control (CON) group. Participants ingested test protein meals (5.0-5.1 g protein/serving) daily for 24 wk. Between-group differences in the change of skeletal muscle mass index (SMI) as the primary outcome and muscle strength as a secondary outcome were tested using multifrequency BIA and a handheld dynamometer, respectively, at baseline, and 4, 12, and 24 wk. The mean changes in the measured primary and secondary outcome variables from baseline to 4, 12, and 24 wk were compared using unpaired t tests. There were no between-group differences in nutritional status, food intake, or total energy and protein intakes at baseline, 12 wk, or 24 wk. The change in SMI was 0.12 kg/m2 (95% CI: 0.01, 0.23 kg/m2) and 0.11 kg/m2 (95% CI: 0.03, 0.19 kg/m2) greater in the APP group than in the CON group at 12 wk and 24 wk (P ≤ 0.03) and knee extension strength was 0.07 Nm/kg BW (95% CI: 0.02, 0.12 Nm/kg BW) and 0.05 Nm/kg BW (95% CI: 0.00, 0.09 Nm/kg BW) higher in the APP group than in the CON group at these times (P ≤ 0.015), respectively. The groups did not differ at 4 wk. Daily intake of a meal containing APP compared with whey protein increases skeletal muscle mass and lower-extremity muscle strength in healthy older women, suggesting that an APP-containing meal may be useful in the prevention of sarcopenia in this group. This trial was registered at as UMIN000035718.

Changes in the vertical distribution of age‐0 walleye pollock (Gadus chalcogrammus) during warm and cold years in the southeastern Bering Sea

AbstractIn the last 20 years, the southeastern Bering Sea has shifted its thermal variability to longer‐term (4–6 years) ocean–ecosystem temperature stanzas. Age‐0 walleye pollock (Gadus chalcogrammus) populations respond to thermal changes with horizontal (east–west) shifts in spatial distribution over the continental shelf, though there are limited data on whether thermally mediated vertical shifts in distribution also occur. Vertical shifts may impact predator–prey overlap between age‐0 pollock and their lipid‐rich prey, calanoid copepods and euphausiids, resulting in different feeding conditions that ultimately affect fish body condition prior to winter onset. For this study, we analyzed acoustic backscatter measured during acoustic trawl surveys over the southeastern Bering Sea shelf in cold years (2011, 2012) and warm years (2014 and 2016) to determine the vertical distribution of age‐0 pollock. This study presents evidence that age‐0 pollock changes in vertical distribution were related to changes in ocean annual temperature. Age‐0 pollock went from occurring deeper in the water column during cold periods to being surface‐oriented during warm periods, potentially exacerbating spatial mismatches between pollock and prey. We relate patterns in a vertical position to physical water column properties, feeding, and bioenergetic condition of collected pollock and discuss implications for recruitment success during different thermal oceanographic stanzas.

Can an invader support commercial fishing? A case study of walleye pollock Gadus chalcogrammus in the western Chukchi Sea

Based on research of bottom and mid-water trawl surveys conducted onboard Russian research vessels in 2003–2020, data on the spatial and vertical distributions of walleye pollock Gadus chalcogrammus in the western Chukchi Sea are presented. The response of walleye pollock distribution related to water temperature, as well as the features of its distribution are also presented. In the water column, schools were mainly comprised of juveniles, while medium-sized and large individuals were scarce. Approximately 98% of the total number of juveniles and 100% of the large pollock caught by bottom trawls were observed in the southern part of the study area, while most of medium-sized fish were found in the northern part. In the water column, walleye pollock was found within the upper 65 m layer. Near the bottom, the majority of small-sized fish and all large individuals were observed at depths shallower 100 m, while over 70% of medium-sized walleye pollock were found at depths than 100 m. In the water column, juveniles were observed at temperatures from −0.4 to 3.3 °C with largest concentrations within a temperature ranges of 0.9–1.8 °C) and 3.0 °C. Near the bottom, walleye pollock were recorded at a temperature from −1.2 to 4.3 °C with maximum number within the ranges 2–3 °C, > 3 °C, and 1–2 °C. A few individuals were found at bottom temperatures below 0 °C. In the water column, the abundance was low during the entire study period. Acoustic estimates were notably higher compared to those based on the results of bottom trawl surveys. The recent dramatic increase of walleye pollock abundance in the western Chukchi Sea appears to reflect a complex of factors, including warming of bottom temperatures, decreasing of ice cover, increasing of northward currents, better foraging conditions, and increasing abundance and biomass in the Bering Sea. An attempt is made to determine the prospects for commercial fishing of walleye pollock in the western Chukchi Sea. Bottom trawl surveys in 2019–2020 indicated an estimate of total allowable catch of 37,200 t for the 2021 and 2022 fishing seasons; in 2021 over 4000 t were caught. However, this kind of fishing cannot be considered sustainable due to several reasons, including the inability to forecast the number of fish migrating from the Bering Sea, the limited fishing season due to harsh climatic conditions, the remoteness of main ports, and the uncertain population status of its stocks.

Polymorphism of mtDNA gene Cyt b of walleye pollock, Gadus chalcogrammus (Gadidae), in the Chukchi Sea, western Bering Sea, and Sea of Okhotsk

The results of the analysis of the Cytb gene polymorphism of mitochondrial DNA in samples of walleye pollock Gadus chalcogrammus from the Chukchi Sea are presented for the first time. The data obtained are compared with those from the western Bering Sea, the Sea of Okhotsk and the Pacific waters off the northern and southern Kuril Islands. According to the analysis of the samples pooled by seas, the populations of the Chukchi Sea and the Bering Sea do not differ from each other and differ statistically significantly (p < 0.05) from the pooled sample of the Sea of Okhotsk. This may be due to the exchange of its genetic material, which occurs because of the mixing from different spawning grounds at the early developmental stages as a result of transfer by currents (1) and active migrations of adults (2).

Processing Alaska Pollock Protein (Theragra chalcogramma) into Kamaboko Protein Mitigates Elevated Serum Cholesterol and Postprandial Glucose Levels in Obese Zucker fa/fa Rats

Fish paste products such as kamaboko (KB) are traditional Japanese foods prepared from fish meat. The health-promoting properties of fish proteins and their lysates include improving glucose and lipid metabolism. Although the KB manufacturing process and quality have been examined, limited studies have reported the health-promoting function of KB. This study aimed to evaluate the effects of processing Alaska pollock protein (APP) into KB protein (KBP) on serum lipids levels and postprandial glucose tolerance. Obese male Zucker fa/fa rats were fed on different diets for 4 weeks as follows: APP group, fed on a diet in which APP constituted 25% of total protein intake; KBP group, fed on a diet with APP-processed protein as the protein source; control group, fed on a diet with 100% casein as the protein source. Compared with those in the control group, the serum total cholesterol (TC) level was reduced and the elevated postprandial blood glucose level was mitigated during the high-carbohydrate meal tolerance test in the APP and KBP groups. Further, KBP exerted significantly higher effects on serum TC levels and glucose tolerance than APP.

Invader's portrait: Biological characteristics of walleye pollock Gadus chalcogrammus in the western Chukchi Sea

Presented here are data on the size composition and age structure, the sex ratio, the state of maturity of the gonads, and the composition of the diet and feeding habits of walleye pollock in the western Chukchi Sea, based on 2003-2020 bottom and mid-water trawl surveys conducted onboard Russian research vessels. During all years of research, mid-water trawl catches in this area were dominated by juveniles with FL 5–12 cm, while the size composition of walleye pollock in bottom trawl catches was bimodal with the dominance of fish 7–14 cm and 50–62 cm long. Females were considerably larger than males (on average by almost 10 cm), with mean FL 56.0–58.3 cm and 52.1–56.4 cm, respectively, in different years. The age structure of walleye pollock was significantly different from that of both the western and eastern Bering Sea since fingerlings and yearlings predominated there in the mid-water trawl catches, and fish under the age of 1 year and 6–17 years were the most numerous in the bottom trawl catches. In the western Chukchi Sea in 2018–2020, the proportion of females in bottom trawl catches ranged from 1.8 to 2.7 females per male. This is probably because walleye pollock here were represented mainly by large fish, while in the mature part of the population, females are usually larger than males. The proportion of fish with gonads at different stages of maturity varied significantly in different years. Immature individuals were extremely few among the fish analyzed. Individuals with developing and post-spawning gonads accounted for a major part of the catches. In recent years, walleye pollock of both sexes have been observed in pre-spawning, spawning, and post-spawning condition, which may indicate the possibility of spawning of individual specimens in the western Chukchi Sea. The survival of eggs, larvae, and fry in conditions of low temperatures is unlikely. However, if the warming in the Arctic continues, it is possible that new walleye pollock spawning grounds may appear in the Chukchi Sea. In the western Chukchi Sea, the proportion of euphausiids in the diet of large walleye pollock (>40 cm in 2018 and > 60 cm in 2019) was significantly higher than that of small fish (<40 cm). In the average long-term plan, the decrease in its diet with the growth was characteristic only for planktonic organisms (small crustaceans, chaetognaths, and larvaceans). Only large benthic crustaceans showed an increase in the walleye pollock diet as it grew. There were no pronounced trends regarding euphausiids and fish. In the western Chukchi Sea, the cannibalism was registered only in large individuals (40–60 cm and >60 cm) and only in 2019 with small number juveniles consumed. Such a low level of cannibalism was probably due to the spatial separation of juveniles and adults, as well as the presence of a sufficient amount of other prey.

Effects of Enzymatic- and Ultrasound-Assisted Extraction on Physicochemical and Antioxidant Properties of Collagen Hydrolysate Fractions from Alaska Pollack (Theragra chalcogramma) Skin.

Collagen hydrolysate were extracted from Alaska pollock skin using enzymatic (EAE), ultrasound (UAE), or combination of enzymatic and ultrasound (EAE+UAE) treatment. Control (C) was not treated with enzymatic or ultrasound. The extracts from C, EAE, UAE, and EAE+UAE were fractionated with ≤3, 3-10, 10-30, and ≥30 kDa. Each fraction was evaluated for biological activity and structural properties. All fractions contained high levels of glycine and proline. The ≤3 kDa fraction of control and ultrasound-assisted extracts exhibited the highest antioxidant activity as measured using Trolox equivalent antioxidant capacity, ferric ion reducing antioxidant power, oxygen radical absorbance capacity, and an assay on the inhibition of nitric oxide production by LPS-induced macrophages. The structurally digested collagen was evaluated using FTIR spectra and SDS-PAGE after Alcalase® and ultrasound treatments. The microstructure of collagen hydrolysate was assessed using SEM microscopy; the surface morphology was altered according to fraction size and extraction conditions. Overall, it was determined that enzyme treatment in combination with ultrasound is the most effective procedure for obtaining digested collagen hydrolysate, which could be used to further improve biotechnological processing for the addition of value to marine production chains in the future.