Feeding habits the Pacific cod <Emphasis Type="Italic">Gadus macrocephalus</Emphasis> in oceanic waters of the Northern Kuril Islands and Southeast Kamchatka

This study examines the feeding habits of the Pacific cod Gadus macrocephalus in waters off the eastern coast of the northern Kuril Islands and southern Kamchatka. In November–December 1996, the cod primarily consumed fish, which made up 47.6% of the total food mass. The proportion of cephalopods, fishery offal discarded from fishing vessels, and decapods did not exceed 18.5, 17.4, and 12.2%, respectively. Among fishes, the main prey item of the cod was atka mackerel (15.4%); among cephalopods, octopus (16.8%); among fishery offal, heads of atka mackerel (14.2%); and among decapods, majid crabs (6.4%). The rather low percentage of walleye pollock (7.3%) in the cod diet was due to the decline of the east-Kamchatka walleye pollock stock.     

The Egg Mortality in Walleye Pollock (Gadus chalcogrammus Pallas, 1814) during Embryogenesis in Waters off the Western Kamchatka Coast

Russian Journal of Marine Biology - Five consecutive ichthyoplankton surveys were conducted during the spawning season of the walleye pollock Gadus chalcogrammus, in April and May 2019, at a...     

An unusual localization of the parasitic copepod <Emphasis Type="Italic">Haemobaphes diceraus</Emphasis> Wilson, 1917 (Copepoda: Pennellidae) on the walleye pollock <Emphasis Type="Italic">Theragra chalcogramma</Emphasis>

During a study performed in April 2008 in the Pacific waters of the northern Kuril Islands, the parasitic copepod Haemobaphes diceraus was found localized on the isthmus of two specimens of the walleye pollock Theragra chalcogramma. In both cases, the parasite directly penetrated the heart, without entering the blood vessels.     

Infestation of walleye pollock with the parasitic copepod Haemobaphes diceraus Wilson, 1917 (Copepoda: Pennellidae) in waters of Sakhalin and the Kuril Islands

The infestation of walleye pollock with a parasitic copepod Haemobaphes diceraus at the coasts of Sakhalin and the Kuril Islands was studied during the spring of 2008. The extensiveness of the infestation in Pacific waters of the northern Kurils was 1.85–1.97%. In the southern Kurils it was from 2.0% (northeast of Iturup Island) to 7.41% (Prostor Bay), in the Tatar Strait it was 1.61%, and off northern Sakhalin Island it was 0.46%.     

Micro-evolutionary processes in sablefish Anoplopoma fimbria,based on polymorphism of the two sites of mitochondrial DNA

Sablefish Anoplopoma fimbria is a deep-sea fish, endemic to the North Pacific Ocean, with continuous range from southern California to the central part of Honshu Island, including the Bering and Okhotsk Seas. It is an important commercial species and a promising object for aquaculture [1, 2]. Compared to the eastern part of the range [3, 4] the population structure of sablefish in Asian waters is poorly studied. It is believed that sablefish goes to the Bering Sea and Pacific waters of Kamchatka and the Kuril Islands from the northeastern Pacific, and Asian waters are its eviction zone [5]. Other authors suggest that replenishment of sablefish off the eastern Kamchatka and the Kuril Islands is not only due to migration of the adult fish from the Bering Sea along the continental slope, but also due to the drift of yearlings by Aleutian current over the American coast [6].     

Comparative characteristics of the diet of Pacific halibut <Emphasis Type="Italic">Hippoglossus stenolepis</Emphasis> from different areas of the northwestern part of the Pacific Ocean

Food composition of Pacific halibut Hippoglossus stenolepis has been considered in three areas of the northwestern Pacific: in the western part of the Bering Sea, in Pacific waters off the northern Kuril Islands and southeastern Kamchatka, and waters off the southern Kuril Islands. The main food items in all studied regions were shrimp, cephalopods, and fish. It has been noted that fish offal plays a considerable role in the feeding of H. stenolepis in the western part of the Bering Sea. Changes in food composition in relation to fish growth, depth of catch, and sex of individuals have been analyzed; and differences in the composition of food items consumed by H. stenolepis in different parts of the studied areas have been considered.     

Specific features of distribution and ecology of the Japanese dog poacher <Emphasis Type="Italic">Percis japonica</Emphasis> (Agonidae) in Pacific waters off the northern Kuril Islands and southeastern Kamchatka

According to materials of 1992–2002, data on the spatial-bathymetric distribution and size composition of the Japanese dog poacher Percis japonica in Pacific waters off the northern Kuril Islands and southeastern Kamchatka are provided. This comparatively scarce, medium-sized representative of the family Agonidae (maximum length of 46 cm) in the observation period was found in the lower part of the shelf and the upper bathyal over the entire study area from 47°50′ to 52°00′ N at depths of 76–770 m; however, its maximum catches (more than 200 individuals per hour of trawling) were constantly recorded in the spring and autumn months at the traverse of the Fourth Kuril Strait and at the eastern slope of the seamount of the northern link of the external Kuril Ridge, mainly in the range of 251–350 m at a temperature of 1.6–3.0°C. The relationship between the depth of catch and the average weight of P. japonica was analyzed. It was shown that the value of its catches in Pacific waters off the northern Kuril Islands and southeastern Kamchatka is subjected to some interannual, seasonal, and diurnal dynamics.     

Some issues related to reproduction of Pacific cod <Emphasis Type="Italic">Gadus macrocephalus</Emphasis> in waters of the eastern coast of the northern Kuril Islands and the southern extremity of Kamchatka

The analysis of data collected in December 1996 and 1998 on the reproduction of cod Gadus macrocephalus in Pacific waters of the northern Kuril Islands and the southern part of Kamchatka was performed. It was shown that the individual absolute fecundity of the cod varies within 0.197–9.729 million eggs and the relative fecundity, in the range of 24-1386 eggs. The fecundity of 1000 mature females comprises 2179–2449 million eggs. The low individual fecundity of fish is related to pseudobranchial tumor growth. The main role in cod reproduction is played by females of two-three size groups characterized by the highest numbers of mature females. It is suggested that different fecundity within the range of Pacific cod is related to environmental conditions, in particular, water temperature in the spawning grounds during spawning rather than to the habitation latitude.     

Distribution and Size and Sex Composition of the Mud Skate Bathyraja taranetzi in the Pacific Waters off the Northern Kuril Islands and Coasts of Southeastern Kamchatka in the Summer Period

Journal of Ichthyology - In the summer period, the mud skate Bathyraja taranetzi lives at depths from ~100 to 757 m in the Pacific waters off the northern Kuril Islands and southeastern Kamchatka;...     

Distribution of the Eelpout Lycodes soldatovi(Pisces: Zoarcidae) over the Continental Slope of the Sea of Okhotsk

The eelpout Lycodes soldatovi was found at depths of 153 to 1005 m in the Sea of Okhotsk; however, it usually inhabits the depth range of 400 to 800. The mean and maximum abundance and the biomass of this species were 198.5 and 1037 individuals per km² and 173.7 and 1275 kg/km², respectively. In view of the data on the distribution of young fish (up to 30 cm in total body length) and the reports on the absence of Lycodes larvae, a hypothesis was developed that this species spawns predominantly in the waters off western Kamchatka and eastern Sakhalin at the depth range of 700 to 900 m. Large individuals (>50 cm) exhibit higher migratory activity and are more tolerant of environmental conditions. That is why they are encountered throughout the distribution area of this species, even in subzero temperature areas. Lycodes soldatovi seems to be a typical inhabitant of the Sea of Okhotsk, except for the waters off the South and Central Kuril Islands and the Pacific waters off the North Kuril Islands.     

Interannual differences in growth and hatch date distributions of age-0 year walleye pollock Theragra chalcogramma (Pallas) sampled from the Shumagin Islands region of the Gulf of Alaska, 1985 – 2001

Daily increments of age-0 year walleye pollock Theragra chalcogramma otoliths from 1985 to 2001 were examined for interannual variability in growth and hatch dates. Fish were collected in summer and autumn surveys near the Shumagin Islands in the western Gulf of Alaska (GOA). Hatch date distributions of these fish were compared with hatch dates of larvae from spawning aggregations located in Shelikof Strait and the Shumagin Islands based on their spawning times. The hatch date distributions of age-0 year fish captured from the Shumagin Islands area were similar to those observed for larvae from the Shelikof Strait spawning group. Age-0 year fish whose hatch dates corresponded to the Shumagin Islands spawning, which occurred earlier in January and February, were not found. Sea surface temperature was associated with variability in hatch date distribution and growth.     

Reproductive conditions of walleye pollock <Emphasis Type="Italic">Theragra chalcogramma</Emphasis> (Gadidae) off the northeastern coast of Sakhalin Island,Sea of Okhotsk

The spatial distribution of eggs and larvae of the walleye pollock Theragra chalcogramma is considered in respect to dynamics of oceanologic processes, nutrients, chlorophyll а and zooplankton off the northeastern coast of Sakhalin Island in spring 2012. It is shown that the effect of severe temperature regime in the near-bottom horizons in the western Sea of Okhotsk during the spawning period of walleye pollock becomes milder due to specific features of water dynamics. The egg distribution is determined by mesoscale eddies in the region. The species survival depends on the effect of such environmental factors as freshwater discharge from the Amur River, eddy structure in waters of the Sea of Okhotsk, and dynamics of phytoplankton and zooplankton development.     

Marine mammals in macro-ecosystems of the Far Eastern seas and adjacent waters of the North Pacific

This article considers the role of marine mammals in a sea or ocean ecosystem based on the example of the Far Eastern seas with adjacent waters of the North Pacific, which is one of the regions of the World Ocean that is distinguished by its high biological and fish capacity and by a high abundance of cetaceans and pinnipeds. Based on extensive data, which was published mostly by Russian experts, the authors have estimated the quantities of annual consumption of fish and invertebrates by marine mammals in three Far Eastern seas: 14.6–18.2 million tons in the early 20th century; 12.3–15.1 million tons in the late 1970s; 22.7–28.8 million tons in the pre-harvest period; and 24.0–24.7 million tons in the early 21st century (27.0–29.5 million tons, if 3–5 million tons in ocean waters off the Kuril Islands and Kamchatka are taken into account). More than half of this quantity is formed by zooplankton and zoobenthos; the second largest portion consists of fish and squid. At the same time, the values of food consumption by fish and large invertebrates are much higher than these estimates for the 0–1000 m layer: 516 million tons were consumed in the 1980s–1990s; 389 million tons in 1991–1995; and 461 million tons in 1996–2005. In the years of high abundance, large walleye pollock alone consumed nearly 40 million tons of small fish and squid. Based on the data of 35-year-long ecosystem studies that were conducted by the Pacific Research Fisheries Center (TINRO Center), the following biomass estimates have been obtained for the biota of the Far Eastern Economic Zone of Russia: mesoand macroplankton, 1000 million tons; zoobenthos, 500 million tons; nekton, 100 million tons; benthic fish, 5 million tons; and large benthic invertebrates that are not included in the benthos, 2.43 million tons. By using these estimates and by comparing the quantities of food consumption by marine mammals, the conclusion was made that the role of marine mammals in food webs of waters of the Russian Far East is remarkable, but it does not reach a level that is high enough to regulate such a large-scale ecosystem as the macro-ecosystem of a sea or ocean.     

New data on the reproductive biology of shortspine thornyhead <Emphasis Type="Italic">Sebastolobus alascanus</Emphasis> (Sebastidae) in the northwestern Pacific

New data on fecundity, sex ratio in different size groups, and the rate of sexual maturation of shortspine thornyhead Sebastolobus alascanus in the northwestern part of the Pacific Ocean are provided. Individual absolute fecundity of the studied females varies in the range of 175 000–821000 (on average, 392500) eggs. In Pacific waters off the Kuril Islands and Kamchatka, among individuals with a length to 41 cm, males dominate; in size groups of 42–59 cm, sex ratio is almost equal; among larger fish, females prevail. In the western part of the Bering Sea among analyzed fish with a length to 44 cm, sex ratio is almost equal; among larger individuals, females dominate. Half of males and females of shortspine thornyhead off the eastern coast of the northern Kuril Islands and southeastern Kamchatka mature at a length of approximately 41 cm that can be recommended as a commercial size for the given species in this area.     

Specific features of distribution and ecology of two species of armorhead sculpins of the genus Gymnocanthus (Cottidae) in Pacific waters of the northern Kuril Islands and Southeastern Kamchatka

Based on materials of 1992?C2012, data on the occurrence, spatial-bathymetric distribution, and size-weight composition of armorhead sculpin Gymnocanthus galeatus and purplegray sculpin G. detrisus and species accompanying them in catches in Pacific waters of the northern Kuril Islands and southeastern Kamchatka are provided. These comparatively numerous, medium-sized representatives of the family Cottidae (maximal length of the former species 49 cm, weight 1400 g and that of the latter, 48 cm and 1140 g) in the period of study occurred uniformly at depths of 76 to 596 m at a near-bottom temperatures of ?1.2 to + 4.5°C. Their maximum by density concentrations were constantly recorded at the beam of the Fourth Kuril Strait, from the oceanic side of the Paramushir and Shumshu Islands, and off the southeastern extremity of Kamchatka mainly in the lower part of the shelf (depths of 80?C200 m) at temperatures of ?1.0 to +2.5°C. Regularities of spatial-bathymetric distribution of different size groups of these species were analyzed. It was shown that the occurrence and the size of catches of both armorhead sculpins in Pacific waters of the northern Kuril Islands and southeastern Kamchatka are subjected to some inrterannual, seasonal, and diurnal dynamics.     

Larval fish production in the tidal River Elbe 1985–1986

In 1985 and 1986 ichthyoplankton composition was studied during seven sampling series at 37 stations along the tidal Elbe and its tributary rivers between Hamburg harbour and the North Sea. The highest larval density was observed in May and April. No, or very few, larvae occurred from late summer to early spring. Smelt (59% on average of all samples) and twaite shad (20%) dominate in the freshwater region. Herring/sprat (17%) dominate in the estuary. All major spawning grounds are located along the southern shore. Smelt spawn further upstream 1 month earlier than twaite shad. Three percent of all larvae found were flounder. Most of them occurred upstream from the estuary in the R. Este and in other tributary rivers. It is not clear whether flounders are able to spawn in freshwater. Attention is drawn to the fact that an unknown but probably very high percentage of the ichthyoplankton is entrained by local power plants.     

Specific features of distribution and ecology of two species of sea poachers of genus Podothecus (Agonidae) in pacific waters off the northern Kuril Islands and southeastern Kamchatka

According to materials of studies in 1992–2002, data on occurrence, spatial-bathymetric distribution, and size-weight composition of two species of sea poachers of the genus Podothecus (P. accipenserinus and P. sturioides) and species accompanying them in catches in Pacific waters off the northern Kuril Islands and southeastern Kamchatka are provided. The distribution of these relatively large representatives of the family Agonidae (maximum length of the first species is 38 and that of the second species is 33 cm, body weight of both 200 g) noticeably differ. In the period of observations, P. accipenserinus was found in catches only to the north of the Fourth Kuril Strait at depths of 80–570 m at near-bottom temperature of ?0.70 to +4.25°C, while P. sturioides was found over the entire studied area in a wider bathymetric range (85–786 m) exclusively at positive values of near-bottom water temperature (0.10–3.55°C). However, more frequently and in greater amounts, both species of sea poachers were recorded in catches off the southeastern extremity of Kamchatka and from the oceanic side of the Shumshu and Paramushir islands. The relationship between the depth of catch and sizes of P. accipenserinus and P. sturioides was analyzed. It is shown that their occurrence and the magnitude of catches in Pacific waters off the northern Kuril Islands and southeastern Kamchatka are subjected to some interannual, seasonal, and diurnal dynamics.     

Specific features of spatial distribution of Pacific cod <Emphasis Type="Italic">Gadus macrocephalus</Emphasis> in waters off the eastern coast of the northern Kuril Islands and the southern extremity of Kamchatka

Spatial distribution of Pacific cod Gadus macrocephalus inhabiting waters off the eastern coast of the northern Kuril Islands and the southern part of Kamchatka has been studied. It is shown that the redistributions of densities of the aggregation of cod during the year occur mainly within the area under consideration. The absence of considerable migrations of cod is related, in particular, to sufficient food availability of abundant hydrobionts: for small-sized groups of cod, the main food are juvenile wall-eyed pollack Theragra chalcogramma and, for medium-sized and large-sized groups, its adult individuals and also Atka mackerel Pleurogrammus monopterygius and squid Belonella borealis.     

The Distribution of Walleye Pollock,Theragra chalcogramma,and Conditions of its Habitat off the Southern Kuril Islands

Russian Journal of Marine Biology - Data on the spatial distribution of the Walleye Pollock, Theragra chalcogramma, and the conditions of the habitat off the southern Kuril Islands in the spawning...     

On the Morphology of Arrowhead Flounders of the Genus Atheresthes in the Pacific Waters of the Northern Kuril Islands and Southeastern Kamchatka

This paper presents the results of studies on the morphology of arrowhead flounders, the Kamchatka flounder Atheresthes evermanni (35 specimens), and the American arrowtooth flounder A. stomias (37 specimens) collected in Pacific waters of the northern Kuril Islands and southeastern Kamchatka in 1998–1999. The morphology of the discussed species is compared with that of arrowtooth flounders from other areas. From this comparison, available information on the sharp increase in the density of the American arrowtooth flounder in the surveyed area (since 1997), and similarities in size compositions of the fish in Kuril and Aleutian waters, a conclusion has been made about the penetration of this species from Aleutian Pacific waters into the area of the northern Kuril Islands and southeastern Kamchatka. This is a result of expansion of the geographical range of this species due to general water warming in the northwestern Pacific during the second half of the 1990s.