Journal of Applied Ichthyology最新文献

Information on habitat transitions is critical to understand whether efforts to manage the freshwater phase of juvenile green sturgeon (Acipenser medirostris) rearing habitats are feasible or beneficial. We implanted microacoustic transmitters in naturally produced age-0 juvenile green sturgeon in the Sacramento River to evaluate residency, general spatial distribution, movement rates, and downstream migration patterns over 300 river kilometers. Furthermore, we investigated whether changes in three environmental variables (discharge, turbidity, and water temperature) were associated with the beginning of movements resulting in the transition from riverine to brackish waters during their outmigration to the Sacramento-San Joaquin Delta Estuary. We captured 183 juvenile green sturgeon by trawl of which 88 were implanted with microacoustic tags. An additional 10 individuals were collected and tagged from the Red Bluff Diversion Dam rotary-screw traps. Linear mixed models showed that individuals caught by trawl had longer upper river residence times, post-tagging, than those caught by trap. Intergate velocity models showed that trap-caught individuals relocated at higher upper river reach velocities than trawl-caught fish, but there were no differences between trap- and trawl-caught fish within the middle or lower reach. Detections showed that juvenile green sturgeon began the downstream transition to brackish water habitat when discharge and turbidity increased. Temperature was not found to significantly influence the initiation of downstream migration. Both continuous and stepped downstream migration patterns were observed in each of the four cohorts, with smaller individuals being more likely to exhibit stepped migration. These data provide information that was previously unknown about the life history of the southern distinct population segment of the North American green sturgeon and can be utilized to assist with water resource management and recovery of this threatened fish species.

Length-weight relationships are presented for twelve fish species collected at 22 sampling points in the Heishui River, a priority tributary for fish conservation in the mainstream of the Baihetan Reservoir area, China. A combination of gill nets was used for sampling over a period between November 2018 and May 2021. The gill nets consisted of 12 nets per point with dimensions of 20 × 2 m (length and width), mesh size ranging from 20 to 80 mm, and soaking depth ranging from 40 to 160 cm. In addition, fixed gill nets were employed, with 10 nets per point having dimensions of 10 to 30 m in length and 1.5 to 2.5 m in width. The mesh size of these fixed gill nets was 10, 15, or 20 mm. This study presents the length-weight relationships of twelve species for the first time in the Heishui River Basin, including the new maximum body length of Pseudorasbora parva (Temminck and Schlegel, 1846). The slope (b) values for the assessed species ranged from 2.5 to 3.5. All the estimated relationships are highly significant (P < 0.05) with a high coefficient of determination R² ranging from 0.9574 to 0.9997. It is expected that the results obtained from this study will contribute to filling the knowledge gap in this area and also assist fisheries scientists in future assessment studies.

The present study evaluates stocks of Etroplus suratensis concerning length-weight relationships (LWRs), condition factor (K), and truss analysis from different habitats, viz., West Bengal (freshwater hatchery), Gujarat (brackish water grow-out pond), and Odisha (Chilika lagoon) in India. All the stocks were collected using gill nets with various mesh sizes of 20–50 mm and cast nets with mesh size of 15 mm from February 2021 to September 2021. The total length (L), weight (W), and digital pictures were taken for LWRs and principle component analysis (PCA). The total length (L) and total weight (W) were measured to the nearest 0.1 cm and 0.01 gm, respectively, followed by regression analysis. The values of parameters “b” in the LWRs equation were estimated within the range of 2.50–3.82 and intercept “a” values (0.235–0.779) and “K” (1.07–3.37), respectively, for all different habitats and ecosystems with significant correlation values (R² ≥ 0.85). In truss morphometric analysis, principal component 1 (PC1) contributed the highest (93.1%) and principal component 2 (PC2) contributed 4.6% to the size and shape variation amongst the stocks from different habitats and ecosystems. The scatter plot analysis and canonical variate analysis (CVA) have shown that the Gujarat and West Bengal stocks are closely placed and separated from the Chilika-Odisha stock. Similar variations were also observed in the ANOSIM boxplot analysis, where Chilika-Odisha stock scored higher than the other two stocks. Since data available regarding LWRs and truss morphometry studies of E. suratensis from different habitats are limited, the present study will provide a clear insight into the differentiation of E. suratensis stocks from different habitats in India. The overall findings of the present study could be utilized for the conservation and sustainable management of E. suratensis.

Barrier presence in river systems has been demonstrated to impair fish assemblages. Low head dams specifically are frequently occurring barriers in riverine environments. Well-supported impacts of these structures on fishes include diminished movement, reproduction, and habitat availability. Longitudinal patterns in riverine fish assemblages have long been researched to ascertain dynamics and display interactions. The need for research becomes more critical when factoring in impacts of barriers and detrimental invasive species. Knowledge of fish assemblages can inform fisheries biologists and aid in improved management practices for recreational and ecologically important species, as well as invasive species. The Neosho River system in Kansas has 14 barriers present. Little fisheries sampling has been done in the Kansas portion of this river system from the John Redmond Dam to the Oklahoma border; therefore, sampling was conducted to inform questions posed about the fish assemblages. We sought to document the fish assemblages of the system in Kansas and examine for assemblage composition distinctions by geographic region along a longitudinal gradient. The fish assemblage dataset from this research generated a wealth of knowledge on sportfish infiltration from reservoirs, imperiled fishes, and apparent impacts from low-head dams. Information from this study will aid in future management and direct new research investigating imperiled fishes.

Cyprinus carpio is a widely distributed and commercially important fish species in Ethiopia. Effective management is essential to sustain fisheries and provide benefits to local communities. This study aims to estimate the growth, mortality, and exploitation rate of C. carpio using length-frequency data. A total of 194 C. carpio specimens (117 females and 77 males) were collected between June 2022 and May 2023. The population parameters were determined using FISAT (ELEFAN I) software. The Von Bertalanffy growth function estimations were L_∞ = 51.45 cm total length, K = 1.1 year⁻¹; t₀ = −0.124 year, and growth performance index (Φ′) = 3.464. The total mortality rate (Z), natural mortality rate (M), and fishing mortality rate (F) were 2.55 year⁻¹, 1.58 year⁻¹, and 0.97 year⁻¹, respectively. The estimated potential longevity (t_max) and average age at which C. carpio attains length at the optimum cohort biomass or yield per recruit (L_opt = 34.79) in Lake Arekit were calculated as 2.60 years and 1.29 years, respectively. The Z/K ratio (2.32), exploitation rate (E = F/Z = 0.38), and highest permissible yield per recruit for C. carpio (E_max = 0.421) suggest enhancing fishery production by increasing the exploitation rate of the underexploited C. carpio in Lake Arekit. The results of this study provide information on the stock of C. carpio, which can be used to guide management efforts. The fish catch in Lake Arkeit is currently far lower than it could be. Therefore, the fish harvest should be boosted through the use of permitted nets, the establishment of groups of fishermen who can catch fish effectively, and the linking of the benefits of fish farming’s supply chain to the potential of fisheries.

A 60-day culture in brackish water (0, 3, 5, 7, 9, and 11 ppt) was conducted to study the effects of salinity on muscle nutrition, fatty acid composition, and anabolic metabolism of blue tilapia Oreochromis aureus. Current research showed that WGR, SGR, and FCR indicators of tilapia were better improved in brackish water. In addition, the physical properties of O. aureus muscle demonstrated a positive correlation with salinity levels. The content of amino acids and fatty acids in O. aureus muscles grown under salinity was higher than that in freshwater (P > 0.05). Venn analysis showed that 2343 common differentially expressed genes (DEGs) were identified in the four groups (0, 3, 7, and 11 ppt), of which 767 were up-regulated and 1576 were down-regulated. GO and KEGG analysis revealed 39 significant pathways, mainly including unsaturated fatty acid biosynthesis, fatty acid elongation, and α-linolenic acid metabolism. The heat map and trend analysis showed that the expression levels of key genes involved in the physiological processes of ELOVL, SPLA2, and FADS2 in the test group were significantly higher than those in the control group (P > 0.05). The above results suggested that O. aureus can not only adapt to the saline habitat but also improve muscle quality by regulating the body’s metabolic pathways.

A 60-day feeding trial has been carried out to access the optimal dietary crude protein (DCP) requirement of juvenile Jerdon’s carp, Hypselobarbus jerdoni. Six isoenergetic (around 400 Kcal DE/100 g), isolipidic (60.80 g/kg), and heteronitrogenous diets were prepared with graded levels of protein, viz., 200, 250, 300, 350, 400, and 450 g/kg (TCP 20-TCP 45 with 50 g/kg incremental level). A completely randomised design (CRD) was used to distribute 270 Jerdon’s carp juveniles (6.12–6.18 g) in six experimental groups in triplicates (15 fish/tank, 200 l water capacity). After 60 days, the fishes of the TCP30 group showed significantly higher weight gain, final body weight, and percentage weight gain (WG%). The fish of the TCP30 group exhibited a significantly higher feed efficiency ratio and specific growth rate. On the other hand, a significantly lower feed conversion ratio is recorded in the TCP30 and TCP35 groups. The protein efficiency ratio of fish was reduced significantly with the elevated DCP level. Whole-body moisture, lipid, and total ash contents of H. jerdoni were remain unaffected by DCP levels. However, DCP levels significantly influenced the whole-body protein of H. jerdoni juveniles, with significantly higher values noticed in the TCP30 and TCP35 groups. The TCP35, TCP40, and TCP45 groups exhibited significantly higher (p < 0.05) protease activity, and the amylase activity showed a decreasing trend in response to dietary protein levels. A significantly (p < 0.05) higher SOD and CAT activity were observed in the TCP20 and TCP25 groups. However, lower hepatic glutamate pyruvate transaminase and glutamic-oxaloacetic transaminase activity were observed in the TCP30 and TCP35 groups, respectively. Furthermore, based on broken-line linear and second-order polynomial regression with respect to WG%, the optimal dietary crude protein requirement of H. jerdoni cultured for 60 days was found to be 309.72 and 316.40 g/kg.

SOXE transcription factors, including SOX8, SOX9, and SOX10, regulate several developmental events, such as sex determination, chondrogenesis, and neurogenesis. This study systematically identified six SoxE subfamily genes from the turbot (Scophthalmus maximus) genome and transcriptome, including SmSox8a, SmSox8b, SmSox9a, SmSox9b, SmSox10a, and SmSox10b. The duplicates of three SOXE members revealed that SoxE subfamily genes in the turbot underwent significant expansion. Relatively conserved exon-intron structures and intron insertions were detected using genomic structural analysis. Besides, phylogenetic analysis supported the previous classification of the SoxE subfamily. Results of the expression profile revealed that turbot SoxE subfamily genes may be involved in different activities, such as neurogenesis and gonad development. These findings would assist in the understanding of fish SoxE gene subfamily activities and evolution.