Main Commercial Fish Species Research Articles

Modern characteristics of mass fish species and their parasites in polar reservoirs of the Yenisei basin (on the example of Khantaiskoye)

Fisheries research was carried out on the Khantayskoye reservoir in 1977–2020. This article presents the results of these works. In the first years after the flooding of the Khantayskoye reservoir, pike and common species of whitefishes (Siberian vendace, peled and whitefishpyzhyan) constituted the basis of the fishery. The share of other fish (carp, burbot, perch) was insignificant. The sharp increase in the food supply for planktophages and benthophages was short-term. Trophic depression began to appear in the early 80s (3–5 years from the moment the reservoir was filled). From this moment to the present time, whitefish species have a slowdown in linear and weight growth, an increase in the timing of puberty, a decrease in fertility. Of the whitefish fish, only Siberian vendace and whitefish are present in the fishery, the numbers of which have significantly decreased. Since the mid-2000s, the number of peled has decreased significantly and this species of fish has become rare in the reservoir. . Currently, there is a relatively high number of pike. Roach, ide, pike and perch actively mastered the channel of Kontiki, where before was practically absent. The increased number of these species affects the number of whitefish in their spawning areas, and their reproduction, including the safety of eggs.The parasite fauna of the main commercial fish species of the Khantayskoye reservoir was investigated. The most pathogenic were myxosporidia Henneguya zschokkei (Gurley, 1894), the causative agent of peptic ulcer disease in whitefishes.

HELMINTH FAUNA OF MAIN COMMERCIAL FISH IN LAKE ECOSYSTEM OF THE NAROCHANSKY NATIONAL PARK (REPUBLIC OF BELARUS)

The composition of the helminth fauna of the main commercial fish species in the lake ecosystem of the Narochansky National Park was determined. It is represented by 10 species of helminths having a complex development cycle with the participation of intermediate hosts, as well as 1 species of helminths (Gyrodactylus sp.), a representative of cl. Monogenea, having a direct development cycle. It was noted that the highest level of invasion was typical for larvae of trematodes Tylodelphys conifera. The greatest variety of parasitic helminths is observed in fish from lake Miastro and Naroch (7 species of helminths each). It was revealed that the most common representatives of the helminth fauna of fish inhabiting the lakes of Narochansky National Park are metacercariae of trematodes of the Diplostomum genus. They were found in fish in all water reservoirs examined. Their host spectrum was also the widest. Examination of the three-spine stickleback showed a severe damage by plerocercoids Ligula intestinalis (prevalence 92% to 98.4%, infection intensity 1–4 pairs per fish). In addition, proboscis worms Acanthocephalus lucii were found in the intestines of the three-spine stickleback. The trematode fauna of fish muscles from the Naroch lake group is rather poor and represented by three types of helminths: Rhipidocotyle illense, Paracoenogonimus ovatus and Apophallus muelingi.

The current state of aquatic biological resources and fisheries in the lower Dniestr and Dniestrovskiy liman

The fish species composition and structural characteristics of the ichthyofauna of the Lower Dniester and Dniesterovskiyliman are presented. In total 79 species of fish from 16 orders, 24 families, 61 genera were observed in 2006–2018.The largest number of species in two orders: Cypriniformes and Perciformes (40.5 and 25.3%, respectively); largest number of genera and species in families: Cyprinidae – 22 genera and 29 species, Gobiidae – 7 genera and 13 species,and Percidae – 5 genera and 5 species. Ichthyofauna of Lower Dniester and Dniesterovskiy liman is represented byfour main faunal complexes. The dominant complex is the Ponto-Caspian, combining brackish and marine fish species.Ichthyofauna of the Lower Dniester is formed mainly by freshwater (55.7% of the total number of identified species)and brackish-water fish (26.6%). Most of species (77.2%) are demersal and bottom dwelling, phytophiles (34.2%)and lithophiles (22.8%), benthophages and carnivores. The remaining groups are represented by fewer species.The analysis of the current state of aquatic bioresources are presented. From 16 to 28 species of fish are recorded inthe commercial catches of the Lower Dniester and Dniestrovskiy liman. The dynamics of catches of the main commercialfish species are presented according to official statistics. Significant increase in the catch of gibel carp, an increase inthe catch of common carp? roach and common bream, and a decrease in the number of populations of predatory fishspecies was observed. The total catch of aquatic biological resources from 2013 to 2017 increased sharply from 547.9 to2344.3 tons per year. Gibel carp Carassius gibelio (Bloch, 1782) is the dominant fish species in the Lower Dniester.The catches of this species increased significantly (up to 1967.8 tons). The age and sex composition, as well as the sizemasscharacteristics of the main commercial species are presented. A decrease in the age composition of the populationsof the main commercial fish species as a result of an increase in the intensity of fishing was observed. The commercialfish mortality rates and stocks of the main commercial species are presented. The stock of gibel carp is set at 5,000–6,000 tons, bream – 630 tons, roach – about 150-200 tons, common carp about 200–250 tons, pikeperch – 20–25 tons.Forecasts of the allowable catch of the main commercial fish species of the Lower Dniester are presented.

Fishery organization in the Lower Dniestr and in the Dnistrovsky liman (analytical overview)

According to official statistics, the long-term dynamics of catch of the main commercial fish species and invertebrates of the Lower Dniester, changes in the structure and variations in the volume of catches are shown. Fisheries in the lower Dniester basin are characterized by a very high level of exploitation of aquatic bioresources, which, along with other factors of anthropogenic impact, has led to changes in the structure of ichthyocenosis. The rapid increase in the number of prussian carp in the last five years indicates a significant imbalance of the ecosystem. Modern approaches to the organization and regulation of fisheries, including commercial, amateur, in the waters of the NRF are considered. The current regulatory documents governing the organization and regulation of fisheries are analyzed. The predominance of IUU fishing over the legal forms of fisheries activities was noted, which seriously threatens the state of commercial aquatic bioresources and makes their rational sustainable use impossible. The problem of reliability of statistical data on the catch volumes of aquatic biological resources is noted. Official fishery statistics provide not only significantly reduced catches but also a distorted catch structure. There are practically no reliable data on fishing by amateur fishermen. The low efficiency of measures taken for the artificial reproduction of aquatic biological resources is shown. The most promising route is the restoration of natural spawning areas downstream of the river and in the estuary, which can have a greater environmental and economic impact than artificial reproduction. Proposals to improve the protection and rational use of aquatic bioresources in the Dniester basin were considered.

СОВРЕМЕННОЕ СОСТОЯНИЕ И ПЕРСПЕКТИВЫ ИСКУССТВЕННОГО РАЗВЕДЕНИЯ РЕДКИХ, ИСЧЕЗАЮЩИХ ВИДОВ РЫБ ДЛЯ СОХРАНЕНИЯ БИОРАЗНООБРАЗИЯ И ВОССТАНОВЛЕНИЯ ЧИСЛЕННОСТИ В ЕСТЕСТВЕННЫХ ВОДОЕМАХ ИЛЕ-БАЛКАШСКОГО БАССЕЙНА

This article presents materials on the current state of the native ichthyofauna of the Ile-Balkhash basin, affected by large-scale acclimatization works. Four species of the ichthyofauna composition are listed in the Red Book of Kazakhstan: spike ( Acipenser nudiventris Lovetsky, 1828), Aral barbel ( Barbus brachycephalus brachycephalus Kessler, 1872), Balkhash marinka ( Schizothorax argentatus argentatus Kessler, 1874), Balkhash perch ( Perca schrenkii Kessler, 1874). Due to the ineffectiveness of fish conservation measures, including the prohibition for catching of these fish species, which are not found anywhere except in the Ile-Balkhash basin, it is necessary to impose artificial reproduction, changes in the Fishery Rules and organization of commercial rearing. The work is based on research materials of 2001-2018 conducted in Lake Balkhash, the delta and the lower reaches of the Ile and the Tokraun. The status of spike populations ( Acipenser nudiventris Lovetsky, 1828), Aral barbel ( Barbus brachycephalus brachycephalus Kessler, 1872), Balkhash marinka ( Schizothorax argentatus argentatus Kessler, 1874) and Balkhash perch ( Perca schrenkii Kessler, 1874). The main reasons preventing the maintenance of a high number of endangered species have been established: small area of natural spawning grounds, death of fry in linmeshing fishing gear, large-scale poaching (spike); deterioration of conditions for the natural reproduction, mass mortality of young fishes in the irrigation system (Aral barbel); total elimination and food competition with pike perch (Balkhash marinka, Balkhash perch). The prospects for preservation of rare and endangered fish species have been considered, recommendations for breeding and replenishing populations of species listed in the Red Book have been given: measures for artificial reproduction and prevention of juvenile death, creating favorable conditions for fattening and reducing the pressure of trophic competition. Without taking adequate measures for reducing the anthropogenic impact on natural resources, including ichthyofauna, the number of main commercial fish species will decrease, rare species of fish will die out.

Community structure of the deep sea fishes in the northern Gulf of Aqaba, Red Sea (Osteichthyes and Chondrichthyes)

The aim of this study was to investigate the community structure of deep sea fishes in the northern Gulf of Aqaba. Deep fish traps, short lines and long lines were deployed at depth ranges from 60 to 700 m between June 2014 and May 2015. A total of 369 fish individuals belonging to 37 species in 21 families were collected. The most abundant family observed in deep fish traps and short line was the commercially important family Sparidae, whereas the most abundant family in long line catch was the commercially unimportant fish family Muraenidae. The most abundant fish species sampled by deep fish traps and shortline was Blueskin Seabream, Polysteganus coeruleopunctatus. The most abundant species in long line catch White-spotted Moray, Gymnothorax johnsoni. In fish traps and with short line, the most commonly caught species was Blueskin Seabream. White-spotted Moray was the most common long line catch. Depth distribution for 37 deep fish species and GIS maps for the two main commercial fish species Blueskin Seabream and Bigeye Hound Shark, Iago omanensis were documented.

Assessing ecological and fisheries implications of the EU landing obligation in Eastern Mediterranean

Discards are of primary target for the European Union policy and concerns have been expressed on the consequances that the landing obligation may have on the fisheries resources and other ecosystem components. In this context, we used an ecosystem modelling approach based on a previously constructed food web model for the Greek Ionian Sea to explore changes in food web components and fisheries due to the application of the landing obligation. Time series were also used to tune the trophic relationships during a hindcast period (1998–2014) and six scenarios were explored after 2015 simulating the current policy; a partial and a total discard ban (implemented after 2017) under both constant and decreasing fishing effort. Results indicated that, under constant fishing effort, changes in the management of unwanted catches (from discarding to landing them) had a significant consequences on certain functional groups, especially on marine birds which were even more adverse in the scenario tuned for the total discard ban. However, the new management practices seem pointless for the sustainability for most of the stocks, because there were no changes in the main commercial fish species apart from few exceptions (e.g. flatfish, deep water shrimps, continental shrimps) in which biomass changes were generally low. In contrast, simulations of declining fishing effort affected to higher extent more groups, whereas additionally representing changes in discarding policies had little effect. The model presented here is intended to shed light in the importance of discards in the food-web structure and subsequently to incentivize the practices to avoid producing discards in the first place.

Assessing the Inter-Relations Between Fish Health and Stock Status of the Main Commercial Fish Species

Abstract This paper aims to show the importance of knowing the health status of fish populations in their natural environment and its influence on fish stocks at the Romanian coast. To assess the interrelationship between fish health status and the state of stocks, the following fish species: turbot, sprat, anchovies and horse mackerel were analysed from the pathological point of view. Pathological analyses performed between 2015 and 2017 revealed the presence of infections caused by bacteria of the genus Aeromonas and Vibrio and parasitic diseases Trichodinosis, Botriocephalosis and Nematodosis. The presence of these diseases in natural fish populations may represent a real danger to the state of existing stocks, but also to their evolution.

Diets and trophic niches of the main commercial fish species from the Celtic Sea.

The characterization and quantification of diets of nine commercially important Celtic Sea fish species (black-bellied angler Lophius budegassa, blue whiting Micromesistius poutassou, Atlantic cod Gadus morhua, haddock Melanogrammus aeglefinus, European hake Merluccius merluccius, megrim Lepidorhombus whiffiagonis, European plaice Pleuronectes platessa, common sole Solea solea and whiting Merlangius merlangus) was undertaken November 2014 and November 2015 to gain a better understanding of fish feeding strategies, prey preferences, competition for resources and, more generally, increases knowledge of marine ecosystem functioning. Prey were classified into 39 taxonomic groups. A feeding overlap index and multivariate analyses were used to classify the fishes into four main trophic groups where interspecific competition for resources may be important: piscivorous species, omnivorous species, planktivorous species and invertebrate benthic feeders. Ontogenetic changes in diet were also considered for L. budegassa, G. morhua, M. aeglefinus, M. merluccius and M. merlangus through partitioning into size classes. This revealed an important shift in the diet of M. merluccius from omnivory to piscivory, whereas M. aeglefinus exhibited no significant ontogenetic change in diet, remaining an invertebrate benthic feeder. Feeding strategies of these species were also investigated using the Shannon niche-breadth index and other descriptors, such as the total number of taxonomic groups of prey and the mean number of prey in gut contents.

Long-term stability of Sphyrion lumpi abundance in beaked redfish Sebastes mentella of the Irminger Sea and its use as biological marker.

The main commercial fish species in the Irminger Sea, the beaked redfish Sebastes mentella, is commonly infected with the copepod Sphyrion lumpi. This ectoparasite is often used as a biological marker for stock discrimination to evaluate the still-debated metapopulation structure of beaked redfish. Nevertheless, it is still not understood whether parasite abundances and communities vary over longer time periods. In the present study, we investigated the abundance of S. lumpi in S. mentella of the pelagic zone of the Irminger Sea and adjacent waters. Our analyses revealed that live S. lumpi abundance remained constant during summer over a sampling period from 2001 to 2015, which confirms its validity as a biomarker. As S. mentella forms dense aggregations during mating, our results suggest that host densities are, regardless of a fishery-induced decrease in host biomass, large enough to facilitate the direct transmission of S. lumpi. After correcting for covariate effects, two stock units could be differentiated, which supports a continuation of the current fishery management strategy.

Питание и трофические отношения массовых видов рыб в прикурильских водах Тихого океана

Feeding conditions of the main commercial fish species are assessed and their feeding relationships are considered on the materials collected aboard RV Professor Levanidov and RV TINRO in the Pacific waters at Kuril Islands in July-August of 2015 and 2016 in the surveys targeted on evaluation of the subtropical species migrations, as Scomber japonicus, Scomber australasicus, Sardinops melanostictus , and Todatodes pacificus , as well as pre-anadromous migrations of salmons Oncorhynchus gorbusha and Oncorhynchus keta . Copepods, euphausiids, and hyperiids dominated in the diet of subtropical species, with exception of Scomber japonicus and Scomber australasicus with fish as a significant part of the diet and Sardinops melanostictus with phytoplankton in the diet. In the salmons diet, copepods, euphausiids, hyperiids, and pteropods prevailed for pink salmon and euphausiids, pteropods, hyperiids, and medusas for chum salmon. Daily and monthly rations were calculated for fish species and their ratio with the stock of large-sized zooplankton was determined. The main consumers of zooplankton were Scomber japonicus (49 % of total consumption in 2016) and Sardinops melanostictus (40 %) and the main consumers of nekton - Scomber japonicus , too (86 % of total consumption in 2016) and Scomber australasicus (13 %). Salmons consumed no more than 1 % in sum. In 2015, Scomber japonicus also was the main consumer (73-71 % of the total consumption of zooplankton and nekton) and salmons’ consumption was even lower. The stock of zooplankton, being in 18 times larger than the fish biomass, provided full feeding demand of the consumers. The stocks of the preferable preys, as euphausiids, copepods, and amphipods, exceeded their consumption in 15-25 times in 2016, though slight deficit of euphausiids was observed in 2015, compensated by high abundance of copepods, hyperiids, medusas and small-sized nekton.

Dynamics of Catches and Actual State of Stock of Gibel Carp Carassius gibelio and Bream Abramis brama in the Dniester Liman in 2004-2014

Paper deals with dynamics of catches, age structure and size-mass characteristics of the main commercial fish species of the Dniester liman - gibel carp Carassius gibelio (Bloch, 1782) and bream Abramis brama (Linnaeus, 1758). Age structure of gibel carp and bream populations turned to domination of younger groups owing to intensive commercial catches. Estimated parameters of the Bertalanffy equation, coefficients of total, natural and fishery mortality are presented. Stocks of gibel carp and bream were assessed. The stock of gibel carp in the Dniester liman is about 1150 tons, of bream – about 630 tons.

A DSC study of phase transition in muscle and oil of the main commercial fish species from the North-Atlantic

Phase transitions were investigated for Atlantic Salmon, Cod, Herring, Mackerel and Rainbow Trout. The onset of melting was found between −33.5°C and −29.3°C. The amount of unfreezable water was calculated by the DSC (differential scanning calorimetry) melting endotherm integration and was in the range between 5.1% and 8.6% for all investigated samples. The low temperature glass transition was determined to be in the range between −86.0°C and −68.0°C. The high temperature glass transition was found within the melting peak, in the range between −14.0°C and −12.0°C, and was associated with ice melting. Phase transitions of fats, which were present in the fish muscles, did not influence the detection of low and high temperature glass transitions in the samples of fresh fish investigated. The data obtained could be useful to model the freezing process, especially at temperatures below −40.0°C, and the prediction of the fish quality during frozen storage.

A comparison of diel feeding pattern, ingestion and digestive efficiency of Oreochromis niloticus and Oreochromis macrochir in Lake Chivero, Zimbabwe

Possible reasons why Oreochromis niloticus have supplanted Oreochromis macrochir as the main commercial fish species in Lake Chivero, Zimbabwe, were investigated in 2006. Diel feeding trends, daily food consumption and protein digestion efficiencies of the two species were compared. Both followed a similar diurnal feeding trend, with peaks at 12:00 and 16:00. The stomach content dry weight for large fish of 20–30 cm SL peaked in the morning, whereas for small 10–20 cm SL fish it peaked at dusk. Small O. niloticus and O. macrochir fed for 14 h and 12 h, respectively, whereas big fish fed on average for 8 h and 6 h, respectively. Oreochromis macrochir ingested more food than O. niloticus. Small Oreochromis macrochir ingested 2.7 g d−1, which was 53% more than that ingested by O. niloticus of comparable size. Big O. macrochir also ingested 2.7 g d−1, which was 4% more than that of O. niloticus of comparable size. The mean digestive coefficient of proteins ingested by O. niloticus, 62.5% (SD 8.6), was higher than that of O. macrochir, 39.4% (SD 9.1). The efficiency of O. niloticus in utilising food was identified as one of the possible reasons why it had successfully replaced O. macrochir in Lake Chivero.

Comparing the Benguela and Humboldt marine upwelling ecosystems with indicators derived from inter-calibrated models

Abstract Large-scale, mass-balance trophic models have been developed for northern and southern regions of both the Benguela and Humboldt upwelling ecosystems. Four of these Ecopath models were compared and calibrated against one another. A common model structure was established, and a common basis was used to derive poorly known parameter values. The four resulting models represent ecosystems in which the main commercial fish species have been moderately to heavily fished: central-southern Chile (1992), northern-central Peru (1973–1981), South Africa (1980–1989), and Namibia (1995–2000). Quantitative ecosystem indicators derived from these models were compared. Indicators based on large flows (involving low trophic levels) or top predators were not well estimated, because of aggregation problems. Many of the indicators could be contrasted on the basis of differences between the Benguela and Humboldt systems, rather than on the basis of fishing impact. These include integrated values relating to total catches, and trophic levels of key species groups. Indicators based on integrated biomass, total production, and total consumption tended to capture differences between the model for Namibia (where fish populations were severely reduced) and the other models. We conclude that a suite of indicators is required to represent ecosystem state, and that interpretation requires relatively detailed understanding of the different ecosystems.

Abundance indices for main commercial fish species caught by trawl from the south-eastern Australian continental shelf from 1918 to 1957

Per-haul records of catches by steam trawlers on the south-eastern Australian continental shelf from 1918 to 1957 were examined for the main commercial species tiger flathead (Neoplatycephalus richardsoni), jackass morwong (Nemadactylus macropterus), redfish (Centroberyx affinis), latchet (Pterygotrigla polyommata) and chinaman leatherjacket (Nelusetta ayraudi). Catch rates in weight per haul per species were standardised to annual indices of abundance using a log-linear model. Standardised annual index trends for flathead, latchet and leatherjacket indicate a strong to severe decline during the period covered by the data. All species showed seasonal patterns, but the peak season varied depending on the species. The distribution of standardised catch rate by area also differed greatly by species, and no single area showed consistent differences across all species. Day trawls caught more flathead, redfish and latchet, while night trawls caught more morwong and leatherjacket. Moon phase had less influence on catch rates than other factors. The correlation of annual index trends to a number of annual mean environmental factors was examined and no strong correlations were found.

Long‐term effects of human influence on fish community structure and fisheries in Berlin waters: an urban water system

Commercial catch and fisheries monitoring data were compared with hydrological and water course characteristics conditions to identify the cause of changes in fisheries production in Berlin water courses since the 1950s. The urban parts of Berlin are densely populated, and the waters are under pressure from shipping, hydraulic engineering, pollution and recreation use. Most Berlin waters are polytrophic or hypertrophic, with an annual nutrient input of 595 t of total phosphorous and 8640 t of total nitrogen. A total of 34 fish species were recorded, eight of which were introduced. According to historical records, seven native fish species are extinct or missing. At present, the fish community is dominated by a few eurytopic species, i.e. roach, Rutilus rutilus (L.), common bream, Abramis brama (L.), silver bream, Blicca bjoerkna (L.), and perch, Perca fluviatilis L., which contribute 85% of all individuals caught. Two ‘faunal breaks’ were identified. The first was the changing of river character from a barbel to bream zone caused by damming and river regulation. This started in the thirteenth century and ended at the beginning of the twentieth century with the extinction of anadromous fishes. The second break was during the 1960s and 1970s, with the eutrophication of Berlin waters and the near total loss of submerged macrophytes. All phytophilic fish species declined greatly and a mass development of eurytopic species started. The catch of pike, Esox lucius L., common carp, Cyprinus carpio L., and tench, Tinca tinca (L.), became negligible, and at present, eel, Anguilla anguilla (L.), and pikeperch, Stizostedion lucioperca (L.), are the main commercial fish species. Concomitantly, the profitability of the fisheries declined and was linked to a decrease in the number of people employed in fisheries by more than 75% compared with 1950.