Total Number Of Fish Research Articles

Influence of stream temperature and human disturbance on prespawn mortality of Chinook Salmon in the Willamette River basin

AbstractObjectivePremature mortality of adult female Chinook Salmon Oncorhynchus tshawytscha is a major barrier to population recovery. The Willamette River basin, Oregon, typifies the problems that are faced by fishery managers in the Pacific Northwest (USA). Adult salmon are trapped and transported upstream of dams to access historical spawning grounds, but annual rates of prespawn mortality (PSM) are high (often >40%) and may limit the recovery of natural populations. The purpose of this study was to identify potential factors related to PSM of female Chinook Salmon that are outplanted above dams and incorporate them into a modeling framework to facilitate adaptive management of outplanting operations.MethodsWe evaluated PSM in Fall Creek of the Willamette River basin prior to transport facility improvements in summer and fall of 2010–2017 and postimprovement during 2020–2021. We estimated PSM and conducted exploratory analyses to identify possible nontransport sources of stress that may contribute to the observed high PSM rates. Candidate factors included long‐term elevated temperature exposure, elevated temperature exposure below the trap, total number of outplanted fish, and monthly human disturbance of outplanted fish. We then developed and fit three models, each representing a hypothesis of a factor influencing PSM, incorporated them into a single alternative decision model, and conducted sensitivity analyses.ResultPrespawn mortality averaged 0.66 (ranging from 0.37 to 0.94) over the study period. According to the simulation results, the top two management actions were to exclude human activities—swimming and fishing—from Fall Creek in July and August.ConclusionExpected PSM rates were predicted to be 0.38 when human activity was excluded in July and 0.37 for August. Sensitivity analyses indicated that the most influential decision model component was the choice of the alternative model.

Impacts of the High-Pressure Bratsk Hydroelectric Power Station on Fish Population of the Bratsk Reservoir

Environmental and ecological effects of the dam of the high-pressure Bratsk Hydroelectric Power Station (HPS) on the fish population and the probability of fish downstream migration from the Bratsk Reservoir have been studied. It has been revealed that thermal stratification of the water column is a significant factor in the ecological differentiation of the fish population in the upper reaches of high-pressure hydroelectric plants. According to hydroacoustics data, most of the ichthyomass, consisting of “warm-water” representatives of the Percidae (65%) and Cyprinidae (22%) families, is concentrated in the relatively warm layer of the epilimnion. Juvenile fish from 30 to 50 mm in size (up to 70% of the total fish number in this layer) are also concentrated here. In the cold-water hypolimnion, the fish population is represented by large single individuals of whitefish (Coregoninae). The data on distribution of fish in the lower and upper reaches of the dam, fish nutrition patterns, growth rate, and the presence of injuries that occur when fish pass downstream through hydroelectric plant dams are presented. Revealed differences in the growth rate of perches from the upper and lower reaches are associated with their constant inhabiting of water masses with contrasting temperatures. Net catches in the lower reaches over the four seasons of research lack injured individuals. These facts prove the absence of mass downstream passage of fish through the Bratsk HPS dam. Juveniles of cyprinids and perches accumulate in the upper warm layer of 0–10 m, i.e. outside the zone of the intake flow formation, which makes their entrance to intake openings at a depth of more than 20 m hardly possible.

Prevalence of Gastrointestinal Parasites of African Catfish (Clarias gariepinus) from River Nasarawa, Nasarawa State, Nigeria

Fish and fish products are significant sources of nutrients for humans. Parasites of fish are of concern since they often produce a weakening of the host’s immunity thereby increasing susceptibility to secondary infections. This study was conducted with aimed to examine the prevalence of gastrointestinal parasites infecting fish. Field study was conducted during the period from September to November 2022. A total of 200 fish samples (Clarias gariepinus) were examined for the presence of gastrointestinal parasites. Result show that, total number of fishes infected 60(30.0%) out of which 26(26.26%) males and 34(33.66) female. Two helminths one each from Cestode and Nematode were isolated from the infected fishes. The Cestode and its prevalence were Diphylobothrium latum (5%) and nematode Procamallanus spp. (3.33%). The protozoa recovered included: Hexamita spp., Protoopalina spp. and Microsporidia with 60.00%, 23.33% and 18.34% respectively. The majority of the parasites were found in the intestine. Fish specimens that were lighter in weight 10 -200g had less infection (12.5%) but those found with parasites weighed between 201-400g (42%). There was no significant difference (P>0.05) in the infection between male and female Clarias gariepinus and with age on the prevalence and intensity of the gastrointestinal parasite. Wild fish (Clarias gariepinus) in River Nasarawa have a high prevalence of intestinal parasites, therefore it is recommended to avoid open defecation that finally is washed down to rivers and streams hence affecting the aquatic organisms and to properly cook wild fish obtained from River Nasarawa before consumption for safety.

Using Bayesian multispecies models to evaluate fish and invertebrate detection probability and distribution in the hypersaline Bahia Grande tidal basin

AbstractObjectiveIn 2000, the Laguna Atascosa National Wildlife Refuge acquired the Bahia Grande (Texas) management unit, a space that had lain barren and arid for 70 years. A large cooperative partnership launched a restoration project to replenish the basin and recover its original tidal hydrology. In 2005, the construction of a pilot channel successfully restored water throughout the basin, and plans to eventually widen the channel were developed. Our study aims to evaluate an estuarine habitat restoration by assessing ecological drivers and the impacts on species diversity.MethodsWe evaluated species richness, detection/occupancy rates, and species–habitat relationships, and we estimated the sampling effort required to achieve a given level of relative precision if relative abundance was used instead of occupancy to inform future sampling. Sampling gear included bag seines for juvenile life stages and gill nets for capturing subadult and adult life stages. For analysis, we used a Bayesian negative binomial linear mixed‐effects model to evaluate richness–habitat relationships and a hierarchical Bayesian multispecies model to evaluate individual species–habitat relationships, and we calculated the total number of fish captured and relative standard error by gear and sample year to produce a precise estimate of relative abundance.ResultOverall, 29 species were caught between 2018 and 2021. Salinity emerged as a clear driver in the Bahia Grande, as both species richness and individual‐level responses were negatively associated with high salinity values. We found that catch estimated as relative abundance had much variability, as is typical of most survey programs assuming constant detectability, and the number of net sets or seine hauls required to achieve a given level of relative precision varied considerably depending on the species, season, year, and gear type. The most collected species were found in the upper extremes of their salinity tolerances—potentially a unique adaptation to this hypersaline system.ConclusionBaseline data suggest that for the channel widening to be successful, there must be a noticeable increase in suitable habitat characteristics throughout the basin.

The effect of various drugs on the survival of sterlet fry in bacterial contamination of water

Currently, aquaculture is a reliable source of increasing the volume of fish food products and serves as a guarantor of food security. The sterlet Acipenser ruthenus L. is one of the main objects of freshwater aquaculture. Feeding with artificial feed, high planting densities and other negative factors of industrial fish farming inevitably lead to increased stress loads. This affects the physiological state of fish. Disturbances in the functioning of the immune system leads to outbreaks of infectious diseases and epizootic disadvantage of pond fish farms. In modern aquaculture, various antibiotics, probiotics and plant preparations are used to treat and prevent bacterial diseases. In this paper, the effect of different feed additives on the survival rate of sterlet fry to infectious agents was investigated. For this purpose, 150 individuals each were seeded into separate pools with high content of myxobacteria and aeromonads in the water microflora. Studies were conducted in 5 separate pools: control group with feed and 4 experimental pools with different feed additives. The duration of the experiment was 75 days. During the experiment, the number of surviving fries was recorded, and at the end, survival rate was calculated as a percentage of the total number of fish initially planted in each pool. Differences in the effect of different feed additives on the survival rate of fry were found. The highest escapement was recorded in the control group and the least in the group with Antibac-100. In the other experimental groups, the percentage of surviving fry was higher than in the control.

Calyptospora sp. in Brachyplatystoma vaillantii (Valenciennes, 1840) captured in salvaterra, Pará state, Brazil

Coccidia of the Calyptosporidae family are parasites that infect a wide range of fish and aquatic invertebrates. Currently, the Calyptosporidae family is represented by species with a heteroxenic cycle, that is, they can infect more than one host, alternating between vertebrates and the definitive host, the fish. Currently, the diversity of species in the genus Calyptospora has been little investigated, which makes it difficult to understand the distribution and prevalence of infection of this group of microparasites in fish. In the present study, thirty specimens of the Brachyplatystoma vaillantii species, from the Paracauari River, in Salvaterra, Marajó Island, were examined. Of the total number of fish examined, 12 fish, 40% of the total, were parasitized by several mature and immature oocysts in the liver, each containing three to four ellipsoidal sporocysts. General morphology of the spores is characteristic of the genus Calyptospora.

A good word on topmouth gudgeon Pseudorasbora parva in small impoundments in the Aral Sea watershed (Central Asia, Kazakhstan)

Biological invasions are one of the most powerful negative factors threatening the natural biological diversity and well-being of continental water bodies. In the Aral Sea (Small Aral) basin, it has now been possible to stabilize the catastrophe that arose as a result of the irrational use of water resources. However, the diversity and impact of alien fish species on water ecosystems remains little known. For 10 years, we studied the distribution of one fish species, topmouth gudgeon Pseudorasbora parva (Temminck & Schlegel, 1846) in water bodies of the Aral Basin in the Republic of Kazakhstan. Now, this species is found everywhere in the Syrdarya River itself, floodplain lakes and most tributaries, but is not numerous. Using the example of two small local impoundments, the ratio of the abundance of topmouth gudgeon and other fish species was studied. There was no significant correlation between the presence of topmouth gudgeon and the presence/absence of other fish species. There is also no any significant correlation between the total number of fish (abundance) and topmouth gudgeon abundance, diversity indices and topmouth gudgeon abundance. The findings do not suggest that topmouth gudgeon has a negative impact on other fish species. More likely, this species is able to quickly expand new habitats, but under more stable conditions of water bodies it gives way to other fish species. At high water temperatures, topmouth gudgeon remains the only fish species that feeds on the larvae of blood-sucking Culex and Anopheles mosquitoes.

Spatiotemporal microplastic occurrence study of Harike wetland, A Ramsar wetland of India

Ramsar wetlands are one of the least investigated areas for microplastic contamination. Harike wetland is located downstream of the confluence of the Beas and Sutlej rivers. Rivers are nature's drainage systems, which collect waste from everywhere and move ahead. On the same note, the Harike wetland, the largest wetland in North India, is an ideal home for migratory birds and aquatic animals. The water in the canal and the fish living within it have been examined for microplastics. Results revealed that the number of microplastics did not significantly differ between sites 1 and 2, but showed a seasonal variation with higher levels observed in the winter season compared to summer and the rainy season. The most common types of plastics detected in the wetland and canal were HDPE and nylon, which were further analyzed using conformational tests, ATR-FTIR, and GC-MS techniques. Additionally, microplastics measuring less than 5mm in size were recovered from the gut of Cyprinus carpio fish, with a 7% recovery rate from the total number of fish analyzed. Although this percentage may seem low, it cannot be ignored given the potential impact on the aquatic environment. This percentage may be less, but it is not ignorable. Indeed, the amount of poorly managed plastic garbage generated by people living around or illegal outskirts garbage dumping near rivers and tributaries is a potential source of aquatic debris.

STRUKTUR KOMUNITAS IKAN DI PERAIRAN DANAU MELINTANG KECAMATAN MUARA WIS KABUPATEN KUTAI KARTANEGARA

Melintang Lake (Kenohan) is a lake located in the Mahakam river area in Kutai Kartanegara Regency, East Kalimantan. This lake has an area of approximately 11,000 hectares. This study aims to determine the type of fish, to determine the total number of fish per station, and to determine the diversity, uniformity, and dominance in Melintang Lake. There were 10 types of fish found. Rempang fish (Osteochilus repang) was the most common fish with 66 individuals. The highest composition was found at station 2. Diversity index at 3 stations ranged from 1.95-2.23. Uniformity ranged from 0.85-0.97 fish were evenly distributed. Dominance ranged from 0.11-0.18 which means that no dominant species was found

Changes in native fish communities in response to the presence of alien brown bullhead (Ameiurus nebulosus) in four lakes (Poland)

The aim of the study was to determine changes in the abundance of Ameiurus nebulosus and native fish in four lakes after 4–7 years. It was hypothesised that A. nebulosus would be the dominant species of fish in various types of lakes. The study was conducted in the summer of 2014 and 2018–2021, using Nordic multi-mesh gillnets. We indicated that relative numbers and biomass of A. nebulosus decreased in the oligo-mesotrophic lake, while increased in lakes of higher trophic conditions. Body weight and total length of A. nebulosus fluctuated from 3.2 to 283.3 g and 64 to 267 mm, respectively. The coefficient of condition of this species varied widely from 0.2 to 1.8 with the highest and lowest values in the meso-eutrophic lake. Ameiurus nebulosus accounted for 0.2–34.1% of the total numbers and 2.4–36.5% of the total biomass of the fish community. In the mesotrophic and meso-eutrophic lakes, A. nebulosus was a dominant component of the fish community after 7 years. The percentage contribution of A. nebulosus to the total numbers of fish decreased with the increasing trophic status of the studied lakes. Our study showed that A. nebulosus could be one of the factors responsible for a decrease in the number of native fish species and a change in the taxonomic structure of native fish in lakes of different trophic status (from oligo-mesotrophy to eutrophy).

Stability analysis of reef fish communities based on symbiotic graph model

The community stability of coral reefs and fish is the focus of ecological monitoring of coral reefs. Among them, the realization of effective metrics of variations in reef fish communities (i.e., the combined communities of coral reefs and fish) is important for analyzing the stability of communities as well as maintaining the ecological balance of coral reefs. Based on coral reef and fish data collected at St. John's Island from 2004 to 2010, this study proposes a symbiotic graph modeling method to express the biological relationships of reef fish communities, and a Pyramid Match graph kernel method for fusing Attributes (PMA) to quantify community fluctuations to measure interannual variability of communities. The results showed that the community similarity was low in 2006, 2007, and 2008. The total coral cover rate in the study area decreased by 32.04% from 2006 to 2007 and increased by 24% in 2008. The total number of fish fell from 3780 in 2006 to 2596 in 2007 and rose to 6249 in 2008. Among them, the proportion of herbivorous fish decreased to 30.84% in 2007. Furthermore, we have combined the Louvain algorithm with the proposed PMA method to effectively identify the regions that should be prioritized for protection. Experiments were conducted on real datasets with good results, demonstrating the potential of the proposed method to assist in the analysis of community stability and identification of priority conservation areas.

A comparison of methods for estimating juvenile salmon habitat capacity to assist with restoration planning and evaluation

AbstractObjectiveA variety of analytical approaches have been developed in recent years to estimate salmon Oncorhynchus spp. freshwater habitat capacity to assist with planning and evaluating habitat restoration. We compared and contrasted seven different methods for estimating juvenile Chinook Salmon O. tshawytscha habitat rearing capacity (total number of fish that a given area of habitat can support), abundance, and habitat suitability in a 3.2‐km reach of the Grande Ronde River, Oregon.MethodsThis included approaches that used statistical methodologies applied to existing empirical data sets, including quantile random forests (QRFs) and spatial stream networks (i.e., Fish Data Analysis Tool [FDAT]), and deterministic models that included the habitat suitability index, the unit characteristic method (UCM), and three habitat expansion methods.ResultWe hypothesized that the methods would provide comparable estimates. However, the approaches provided very divergent estimates for the same stream reach, ranging from 1048 to 24,530 juvenile Chinook Salmon. The simple habitat expansion methods appeared to be the most similar to the actual parr (juvenile) abundance obtained from recent snorkel surveys (4179 juveniles). The fish density data (fish/m2) and habitat data used in the models were likely the main drivers of the differences between the UCM and habitat expansion methods.ConclusionThe habitat expansion approaches, which are based on detailed habitat surveys, appear to be particularly suitable for estimating capacity within a reach; thus, they may be suitable for evaluating changes due to habitat restoration. The model‐based approaches (QRF and FDAT) appear to yield coarser estimates, in part because they use various inputs at the reach and landscape scales. As such, they are more useful for relative comparisons among reaches in watersheds to assist with watershed‐scale restoration planning and prioritization. Because all of the methods rely on fish density in different types of habitats, regional or local data on fish densities would improve their accuracy.

Fish diversity and assemblage in the Batticaloa lagoon, Sri Lanka.

The Batticaloa Lagoon (Sri Lanka's third-largest brackish waterbody) has suffered habitat degradation and water quality deterioration during the past 30 years due to various anthropogenic activities. Despite Sri Lanka having 40 lagoons, inventories on the lagoon ichthyofauna are rather meagre and data on fish diversity and assemblages are scarce. An assessment of fish diversity is essential to maintain the ecological stability and lagoon fisheries. This study examined the fish fauna of the Batticaloa lagoon considering the northern and southern regions of the lagoon and various depths through a 3-year survey (2017-2019) and documented the dominant and rare fish species. In addition, biodiversity measures, species assemblages and the role of environmental parameters on the distribution of fishes were documented. Various diversity indices (the Margalef richness index, the Shannon-Weiner diversity index, Pielou's evenness index, the dominance index, the taxonomic diversity index, the average taxonomic distinctness index and the total taxonomic distinctness index) were calculated. Analysis of similarities (ANOSIM) was used to examine the seasonal and regional differences in the fish assemblages. The survey showed the occurrence of 96 species belonging to 40 families and 11 orders. Ambassis gymnocephalus was the most abundant fish species (8.7% of the total number of fishes collected) followed by Etroplus suratensis (6.8%), Arius maculatus (6.1%), Gerres filamentosus (5.3%), Oreochromis niloticus (4.6%) and Gerres abbreviates (3.9%). Dasyatis uarnak (0.02%), Acanthurus gahhm (0.03%), Alectis ciliaris (0.04%) and Crossorhombus valderostratus (0.08%) were considered as rare species which constitute less than 0.1% of the total while D. uarnak was considered a doubletons species (represented twice in the whole sample of 16 stations). Two types of species assemblages, one in the northern region and one in the southern region, were evident in a dendrogram (Based on the samples were collected on each region dendrogram were plotted with respect to sites then finally dendrogram of one region pratly connected by other region) based on sample composition similarity estimated with a Bray-Curtis matrix and nonmetric multidimensional scaling plots. The Bray-Curtis dissimilarity was 59.03% between the two regions, indicating statistically significant differences in assemblages (ANOSIM R 0.801; P < 0.01). The northern region of the lagoon had a higher number of species, density, Margalef richness, Pielou's evenness, Shannon-Wiener diversity, taxonomic diversity, taxonomic distinctness and total taxonomic distinctness compared to the southern region. The northern region showed significantly higher levels of salinity and dissolved oxygen (DO) and the southern region higher temperature, turbidity, phosphates and nitrates. The best subset of biota and environmental variables [BEST(BIO-ENV)] test showed a significant relationship between fish assemblage and environmental parameters. Distance-based linear model analysis showed a significant relationship between fish assemblage and the environmental parameters salinity, temperature, pH and DO. The sequential test of this analysis showed the environmental parameters to explain about 74.9% (R2 ) of the total variation. The bioenvironmental model developed was found to be appropriate. Thirteen species were found to be influential as they explained the overall fish distribution pattern with a Spearman rank correlation of 0.951. Ten groups of coherent species were also identified in the study area. In stations having anthropogenic activities, the fish diversity was low. The fish fauna of the Batticaloa lagoon should be monitored periodically to protect the fishery resources here. An understanding of the role that environment plays in structuring the fish assemblage in the Batticaloa lagoon and locations with critical habitats will be of great importance in the conservation and management of fishery resources in this lagoon. However, as monitoring only the dominant species may fail to pick up on important impacts affecting the less common species, it should be done using diversity indices and rare fish species. Monitoring is imperative in view of the livelihood of the fishers this lagoon supports and the health of the local people, as fish is a healthy food. The fishery resources of this lagoon must be protected for posterity with appropriate management measures.

Anthropogenic disturbance of aquatic biodiversity and water quality of an urban river in Penang, Malaysia

Malaysia's rapid economic and demographic development have placed negative pressure on its water supplies and the quality of the Juru River, which is close to the nation's capital and its major source of water. Healthy aquatic ecosystems are supported by physicochemical properties and biological diversity. This study evaluated the anthropogenic impacts on aquatic biodiversity, especially plankton, fish, and macrobenthos, as well as the water quality of the Juru River in the Penang area. Aquatic biodiversity and river water parameters were collected from ten sampling stations along the Juru River. Seven variables were used to assess the physicochemical environment: pH, temperature, total suspended solids (TSS), salinity, dissolved oxygen (DO), biochemical oxygen demand (BOD), and chemical oxygen demand. At each sampling station, the total number of plankton, fish, and macrobenthic taxa were counted and analyzed. The relationships between the physicochemical parameters and aquatic biodiversity were investigated with biotypological analysis, principal component analysis, hierarchical cluster analysis, and linear regression analysis. These analyses showed that the richness and diversity indices were generally influenced by salinity, temperature, TSS, BOD, and pH. The data obtained in this study supported the bioindicator concept. The findings, as they related to scientifically informed conservation, could serve as a model for Juru River management, as well as for river management throughout Malaysia and other tropical Asian countries.

UKURAN KEPADATAN DAN POTENSI IKAN BARONANG TOMPEL (Siganus guttatus Bloch 1787) DI TELUK KOTANIA SERAM BAGIAN BARAT

Spotted rabbitfish (Siganus guttatus Bloch 1787) are valuable commercial fish species. Research on the fish species has been carried out in the waters of Kotania Bay, aiming to obtain information about size, density and potential of the fish species. Data are collected about total length (TL), weight and number of individual fish at four observation stations using 120m length of bottom gillnet with mesh size of 2.0, 2.5, 3.0 dan 3.5 inches. The bottom gillnet is operated in a circle that starting two hours before the low tide then the spotted rabbitfish caught are collected at the low tide. The results showed that the total length of the spotted rabbitfish is in the range of 11,3 – 33,9 cm which has dominated by fish with sizes of 18, 24 and 26 cm. Mean density of the fish is 209 individual/ha, so the abundance the fish in the area of seagrass beds 823.62 ha was estimated as 172.486 of fish individual, it’s 72,51% or 125.070 individuals are those fishes that has spawned for the first time. The mean weight of the spotted rabbitfish at this size is 533,51 grams, so calculated biomass is 66,73 tons and MSY value is 33,365 tons in wet season.

The adventive species community changes in the Cheboksary reservoir during 2001-2021

Generally publications devoted to invasive fish species in the Volga-Kama cascade of reservoirs represents relative indicators and do not provide data on the abundance, numbers and invasive communities’ single species dynamics. It does not allow providing a correct assessment of population’s state and changes in the nonindigenous species composition. In this work, changes in the abundance and species structure of the Cheboksary reservoir’s invasive fish community during 2001-2021 were estimated. The total fish count was determined on data of active fishing gears catches and precise reservoir area. Differentiation into mass, widespread and relatively numerous and locally found with a small average abundance species was noted. A decrease in the species evenness of the invasive community was recorded in consequence of the Black Sea-Caspian sprat Clupeonella cultriventris (Nordmann, 1840) and the round goby Neogobius melanostomus (Pallas, 1814) domination rise. The Black Sea-Caspian sprat and the round goby put together for 98.7% of the total number of invasive fish in the current period. Due to this two dominant species there is a tendency to increase the relative abundance of invasive fish species in the reservoir up to 561 unit/ha despite a significant decrease in the abundance of some other invaders.

Distribution of fish in the subarctic lake

The paper studies fish population of an isolated lake in the subarctic zone. The study of the features of distribution of fish, the assessment of their abundance and size structure were carried out by the echometric method using hydroacoustic complexes and geoinformation systems. The research found out that the fish population is represented by 4 species of fish: roach, perch, pike and peled, with the absolute dominance of cyprinids. Their share of the total number of fish in the reservoir was &gt;80%. Features of the horizontal distribution of fish are mainly due to trophic-defensive behavior (concentration of juveniles in the littoral), where it is possible to use macrophytes as shelters from visually oriented predators - perch and pike. In the horizons of the water column with depths &lt;5 and &gt;5 m, 72.4 and 27.6% of fish from their total abundance in the reservoir were recorded, the average density of fish at the considered horizons was 2149 and 398 ind. / ha. In the vertical aspect, the distribution of fish is determined by both trophic-defensive (concentration of juveniles in the littoral) and thermoregulatory behavior (concentration of peled on the drope of depth in the profundal zone).

Влияние пробиотика «Энзимспорин» на морфофизиологические показатели гибрида ленского осетра и белуги при выращивании в аквакультуре

The use of probiotics is recommended for sustainable growth, increased resistance and efficiency of feed assimilation. Currently, there are commercial probiotic products prepared from the bacteria Bacillus sp., Lactobacillus sp., Enterococcus sp., Carnobacterium sp. The use of the probiotic supplement “Enzimsporin” in fish farming is in its infancy. However, information is available on the effectiveness of its use in rainbow trout. In this regard, an urgent task is to study the effect of the probiotic “Enzimsporin” on the morphophysiological parameters of the juvenile hybrid of Lena sturgeon and beluga (Lenbel) under existing cultivation conditions. At the initial stage, the fish were divided into 8 groups of 50 fish each according to the principle of pairs of analogues. Large and small individuals were divided into four groups: control and experimental with a dose of Enzimsporin of 1 g/kg, 1.5 g /kg and 2 g/kg of feed, respectively. The duration of the experiment was 60 days. Total catches were made at the beginning and end of the experiment, and intermediate catches were made every 15 days, individually weighing 25–35% of the total number of fish in the pool. The physiological state and immune status of Lenbel were assessed by hematological and cytochemical parameters. Blood for analysis was collected from the caudal vein of fish in vivo. Leukocyte composition and the proportion of immature cell types were determined in Pappenheim-stained peripheral blood smears under a digital microscope. The phagocytic activity of fish neutrophils was evaluated by a lysosomal cation test using a cytochemical method with bromophenol blue. During the two months of the experiment, the main hydrochemical parameters (pH, nitrites, nitrates, ammonium), water temperature and the dissolved oxygen content were within the technological norms. The best absolute and relative growth rates were obtained in the experimental groups receiving a probiotic at a dose of 1.5 g/kg of feed. These fish had high indicators: absolute and relative growth, absolute and relative growth rate, mass accumulation coefficient. The best survival rate was recorded in the group of small yearlings of Lenbel at a probiotic dose of 2 g/kg of feed. In large fish, the maximum survival rate (80%) was recorded at a dose of 1 g/kg of “Enzimsporin”. There is significantly more lysosomal cationic protein in the blood neutrophils of the experimental groups – activation of cellular immunity.

Some biological aspects and fisheries assessment of Diplodus vulgaris (Geoffrey Saint-Hilaire, 1817) (Teleostei: Sparidae) caught by gillnets (Egyptian Mediterranean waters, Alexandria)

This study was conducted to estimate some biological aspects and fisheries assessment of Diplodus vulgaris caught by gillnets during the period 2018–2020 from the Egyptian Mediterranean waters of Alexandria. From an overall of 1004 individuals of D. vulgaris (10.0 – 24.0 cm TL) examined, lengths from 13.0 to 17.0 cm were representing 82.67% of the total fish number. The length-weight relationships for total and gutted weights of the D. vulgaris were: Log W = −1.7144 + 2.9063 Log L (R2 = 0.9982) and Log W = −1.8508 + 2.9903 Log L (R2 = 0.9967), respectively. The condition factor (k) was found to be fluctuating between 1.268 and 1.534 with an average value of 1.395 ± 0.0597. The overall sex ratio (M: F) was 1.00: 0.63 and the chi-square test revealed highly significant difference (χ2 = 24.80; df = 1; P < 0.01). The spawning season of D. vulgaris was observed from December to February for both sexes. The gonadosomatic index (GSI) reached its highest value in December for both sexes. The age composition of the D. vulgaris catch was estimated to be four years and the first age dominated the population. The present von Bertalanffy growth parameters were calculated as follows: the coefficient of growth (K) = 0.128 yr.-1, the asymptotic length (L∞) = 37.06 cm, and the hypothetical age at zero size (to) = −2.773 yr.-1. The growth performance index (Ф') was: Ф'L = 2.24, and Ф'W = 1.00. The reproductive load (Lm/L∞) was low for males (0.39) and females (0.37). The ratio LmaxD/ LmD was 1.36 and 1.39 for males and females, respectively and it was found to be compatible with the Pauly's Gill-Oxygen Limitation Theory (GOLT). The total mortality coefficient (Z) was 1.79, the natural mortality (M) was 0.39 and fishing mortality (F) was 1.40. The M/K was 3.0615 and Lc/L∞ was 0.371. At the level of the current exploitation rate (Ecur = 0.78), the stock is considered highly exploited by gillnets fishery and only 9.34% of the stock biomass is protected. Fishery management for this wild stock is highly required.

Patterns of fish distribution in tropical rock pools at Príncipe Island, Gulf of Guinea

Little is known about the ichthyofauna from intertidal rock pools of the west coast of Africa, especially in the Gulf of Guinea. Rock pools are characteristic habitats of the intertidal zone of structurally complex rocky shores, adding important niche space to coastal fish species. In this study, rock pools of three similar rocky shores of Príncipe Island were sampled to describe the composition, abundance and distribution of fish assemblages and their relation to parameters of pool structure (volume, depth), water mass (temperature, salinity and pH) and biology (algal and coral cover, and biological species richness). A total of 18 fish species and one leptocephalus larva of unknown species, representing 13 families, were observed during sampling. In decreasing order, the five-most-abundant species were the goby Bathygobius burtoni, night sergeant Abudefduf taurus, West African rockhopper Entomacrodus cadenati, sailfin blenny Microlipophrys velifer and Biafra doctorfish Prionurus biafraensis, which together represented 81% of the total number of fish recorded during this study. The four-most-abundant species also proved to be the better adapted to the range of conditions found in rock pools. Overall, larger rock pools with minimal biological cover and higher salinity were found to support higher fish abundance and species richness. Most species individually preferred rock pools with larger volumes, but some presented a degree of habitat specificity, such as the absence or presence of biological cover. Species that were more-active swimmers preferred deeper pools.