Journal of Applied Ichthyology最新文献

Sturgeon species (Acipenseridae) around the world have undergone substantial population declines over the past century due to a suite of anthropogenic actions and overharvest. Shovelnose sturgeon are the smallest and most abundant sturgeon species in North America and still support commercial and recreational fisheries despite notable declines in abundance and population structure throughout much of their range. The Rock River, located in Northwestern Illinois, USA, has recently attracted angler attention in response to numerous state record shovelnose sturgeon captured via recreational angling (unregulated recreational fishery), thus prompting the need to understand the size structure and demographics of this largely undescribed population to inform management actions. This study was the first to describe relative condition and size distributions of shovelnose sturgeon in the Rock River, Illinois. A total of 1324 unique shovelnose sturgeon were captured between Fall of 2022 and Winter 2024-2025, with 22% of captured fish meeting or exceeding trophy size class requirements (≥ 810 mm). Shovelnose sturgeon in the Rock River can reach larger body sizes (length and weight) than other regional systems. The Rock River supports the highest proportion of trophy class shovelnose sturgeon in the world. Although no commercial exploitation occurs, recreational angling is currently unregulated, and this population may be vulnerable to substantial shifts in population structure that may warrant management action. Future research seeks to gain a better understanding of population dynamics and develop robust long-term monitoring protocols to inform data-driven management.

Understanding the density-dependent effects is essential for sustainable fishery management. Stocking and harvesting activities directly influence fish abundance and associated density-dependent responses. In this study, we compared the body size, age structure, growth patterns, and body condition of bighead carp (Hypophthalmichthys nobilis) from two large subtropical reservoirs in China: Shanmei Reservoir (SMR) (n = 161) and Liuxihe Reservoir (LXHR) (n = 257), which have different stocking and harvesting patterns. In SMR, annual stocking and harvesting maintain a lower bighead carp biomass (catch per unit effort, 0.62 ± 0.03 g/m²/24 h), whereas in LXHR, annual stocking without harvesting results in higher fish biomass (0.84 ± 0.01 g/m²/24 h). Plankton biomass and abundance, particularly zooplankton, were significantly higher in SMR than in LXHR. The SMR population exhibited a more stable age structure, faster growth, and better body condition, whereas the LXHR population showed the opposite trends under higher fish density. Both populations exhibited isometric growth and included individuals aged one to five, but dominant age groups differed. The SMR population had a larger inflection age and greater standard length (SMR: 4.7 years and 591 mm; LXHR: 3.5 years and 456 mm). In addition, total mortality, fishing mortality, and exploitation rates were higher in SMR than in LXHR. These findings highlighted the role of stocking and harvesting in shaping fish density and hence inducing density-dependent effects. A balanced fisheries strategy integrating both practices is crucial for sustainable fish population management.

The utilization of live Tubifex (Tubifex tubifex) as a feed source in ornamental fish aquaculture is widely recognized for its high nutritional value. However, feeding live tubifex worms come with a higher risk of transmitting parasites, and precautions must be taken. So, necessitate feeding strategies have to be adopted which includes dietary diversification such as usage of tubifex in frozen form. This study aimed to evaluate the nutritional stability of frozen Tubifex over a 12-week period (85 days), stored at −20°C. Weekly evaluations were conducted to measure changes in key nutritional parameters, including crude protein, moisture, lipid, and ash content. The results indicated that crude protein content remained stable (p > 0.05) for the first 5 weeks, while lipid content showed no significant changes (p > 0.05) until the seventh week. Additionally, ash content was stable (p > 0.05) until the ninth week of storage. These findings suggest that frozen Tubifex can be safely stored for up to 36 days without significant nutritional degradation, offering a viable alternative to live feed in ornamental fish aquaculture this research supports the use of frozen Tubifex by mitigating the risks associated with live feed while ensuring optimal nutritional delivery to aquatic organisms.

This study estimated the length–weight relationships (LWRs) and length–length relationships (LLRs) for 6 fish species in the middle Yangtze River basin and its adjacent lakes (Ochetobius elongatus (Kner 1867), Rhinogobio cylindricus (Günther 1888), Hemibagrus macropterus (Bleeker 1870), Pseudobagrus albomarginatus (Rendahl 1928), Siniperca knerii (Garman 1912), and Coreosiniperca roulei (Wu 1930)). All fish specimens were seasonally collected through scientific research monitoring of fishery resources from May 2020 to June 2023. A triple gillnet (with a mesh size of 20–30 mm, a height of 2.0–4.0 m, and a length of 30–50 m) was employed for the capture. The LWRs and LLRs of all specimens were highly significant (p < 0.05), featuring high correlation coefficients (r² ≥ 0.9511). These findings not only enriched the data in FishBase but also offered supplementary references for the management of the Yangtze River during its fishing ban period.

Studying size frequency, size relationships, and the conditions of fish is vital for managing the resources properly. Some biological aspects of the fishes in Geray Reservoir were studied from October 2017 to August 2018. Fish were sampled monthly by overnight setting of gillnets. Fishers’ catch was also used. Fish were dissected and sexed. Biological parameters were measured following standard procedures. Four fish species (Oreochromis niloticus, Tilapia rendalli, Carassius auratus, and Cyprinus carpio) belonging to the Cichlidae and Cyprinidae families were identified. From the total 570 fish specimens collected, 426 (74.7%), 66 (11.6%), 44 (7.7%), and 34 (6.0%) were O. niloticus, T. rendalli, C. auratus, and C. carpio, respectively. In Geray Reservoir, most of the sampled fish specimens were found in length intervals of 24–27, 18–24, 24–32, and 41–49 cm for O. niloticus, T. rendalli, C. auratus, and C. carpio, respectively. Length–weight relationships of O. niloticus, T. rendalli, C. auratus, and C. carpio were curvilinear and statistically significant (p < 0.05). For all introduced fish species, b values were less than 3, negative allometry growth. The mean Fulton condition factor of O. niloticus, T. rendalli, C. auratus, and C. carpio was > 1 and showed significant variation (p > 0.05) among months. In Geray Reservoir, all four economically important fish species are fully established and contribute significantly to local livelihoods. However, in this sampling scheme, the number of catches of T. rendalli, C. auratus, and C. carpio deserve due attention for the management of the exotic fish species. The data presented in this work could be vital for further biological investigations, helping researchers to assess the status of the introduced fishes in the reservoir and for local fish managers to select appropriate management strategies.

Relationships between weights (W, dry weight [DW] and wet weight [WW] and lengths L, standard length [SL], head length [HL], and caudal peduncle depth [CD]) and these between DW and WW were examined in 61 freshwater fishes using formula W = aL^b and DW = aWW^b, respectively. The parameters of the SL–DW, SL–WW, HL–DW, HL–WW, CD–DW, CD–WW, and WW–DW relationships were determined for 60, 61, 57, 58, 50, 50, and 61 taxa, respectively, with the criterion where the estimated R-square was greater than 0.8. For the genus or higher taxonomic level, parameters of the SL–DW and SL–WW relationships were determined for 20 taxonomic groups with the same criterion to each species. For the three eel-like species, the SL–DW and SL–WW relationships were largely consistent with the pooled taxonomic data. In contrast, noneel-like species exhibited variations in these relationships across species. Systematic variations in the SL–DW and SL–WW relationships were observed at the order and family levels, except in Salmonidae, Cobitidae, and Cottidae. However, at the genus level, these relationships were generally consistent among species. These intragroup variations should be considered when applying these equations to ecological and taxonomic studies.

The Denkoro River is the largest river in Borena Sayint National Park (BSNP) of Ethiopia. Many studies have been conducted on the terrestrial biodiversity of the park. However, there are no baseline data on the fish biodiversity of the park. Therefore, this study aimed to assess the diversity, determine the biology of the dominant fishes, and compile baseline data. Fish specimens were collected using gillnets (4, 6, 8, 10, and 12 cm stretched mesh sizes), monofilaments (5, 10, 15, and 20 mm mesh size), and hook and lines. Fish samples in the Denkoro River were collected in wet (September) and dry (December) seasons, 2022. A total of 398 fish specimens were collected from three sites in both seasons. Five fish species, Labeobarbus intermedius, Garra dembecha, Clarias gariepinus, Labeobarbus beso, and Oreochromis niloticus, were identified from the river. The diversities (H′) of fish species in the Wachau, Buke, and Kernemariam sites in the dry season were 1.45, 0.95, and 0.64, respectively. During the wet season, fish species diversity was lower than that in the dry season, with Shannon diversity indices of 1.33, 1.18, and 0.93 at the Wachau, Buke, and Kernemariam sites, respectively. L. intermedius was the most abundant species, with 42.9% of the total catch. The length–weight relationships of L. intermedius and L. beso followed a curvilinear pattern, described by the equations TW = 0.005TL^3.12 and TW = 0.01TL^2.94, respectively. In all sites, females were more numerous than males and statistically significant (Chi-square, p < 0.05). For sustainable fish conservation and development, further research on fishing activities, feeding habits, and fish biology is needed. Important management measures such as regulated fishing activities, habitat restoration, and spawning ground protection should be performed in the area.

The rainbow trout, Oncorhynchus mykiss, is the most extensively cultured coldwater fish species in India. However, skeletal deformities remain a significant concern and are frequently reported in rainbow trout farming operations. The incidence of skeletal deformities can serve as an indicator of the quality of rearing conditions and environmental factors. The present study was conducted to assess the skeletal deformities of rainbow trout, from selected farms in Himachal Pradesh, and Uttarakhand, India. During the study, physicochemical parameters such as water temperature, pH, dissolved oxygen (DO), nitrogen and phosphorus compounds, and chlorides were recorded. The brain, gill, and muscle tissues were examined under optical microscope to inspect myxozoan parasite infections. Nevertheless, myxozoan parasites were not detected in the microscopic examination. For histopathological analysis, tissue samples from the internal organs were processed. The degree of acinar cell necrosis, fibrosis, and macrophage aggregation were determined through histopathological examination. The skeletal deformities, whirling behavior, and mortality were directly associated with the major pancreatic anomalies but no signs of parasite presence.

Identification of polymorphism in growth-related genes and their association with growth traits is an area of intense research. The growth rate is the most sought-after economic trait in the breeding program of fish. The significant association of polymorphism will aid in marker-assisted selection and speed up the genetic improvement program. The present study was performed in a population of common carp belonging to an ongoing selective breeding program at ICAR-CIFE, Rohtak Center. A total of 50 common carp based on the breeding value for body weight were selected and bifurcated into two groups: high and low performers. Each fish had three records (based on pond age) for growth-related traits, viz., body weight (Bw), body length (Bl), and body height (Bh). At 200 days of pond age, the mean Bw, Bl, and Bh for high performers was 494.28 ± 52.12 g, 23.764 ± 0.63 cm, and 9.36 ± 0.35 cm, respectively, whereas the mean Bw, Bl, and Bh for low performers was found to be 165.72 ± 17.31 g, 16.20 ± 0.57 cm, and 6.40 ± 0.23 cm, respectively. The DNA was extracted from the fin clips of these fish. Five primers were used to amplify five distinct regions of the growth hormone gene covering five exons and four introns. The positive PCR products were purified and subjected to Sanger sequencing. The sequences with a Phred quality score above 20 were imported in Sequencher V for SNP hunting. Five polymorphic sites were detected, viz., C165 (amplicon 3), D60 (amplicon 4), D114 (amplicon 4), E90 (amplicon 5), and E185 loci (amplicon 5). The population genetic analysis was performed using GenAlex V. The D60 and E185 loci significantly deviated from the Hardy–Weinberg equilibrium (p < 0.05). Growth association was performed for the polymorphic loci using a linear model by invoking PROC GLM in SAS. The loci C165, D60, and E90 were significantly associated with the Bw, Bl, and Bh. The results obtained in this study must be utilized in the ongoing selective breeding of common carp to speed up genetic improvement.

To reconstruct the life history of Coilia nasus in the Shandong section of the Yellow River, an electron probe microanalyzer (EPMA) was employed to analyze the Sr and Ca values in the otoliths of 12 individuals collected from Pangkou Bay. The results indicated that the life history of C. nasus is complex and diverse, the individuals in this study can be categorized into five distinct patterns. Pattern I includes P1, P2, P3, and P4, whose life history tracks indicate hatching in brackish water near the Yellow River estuary; after approximately 1 year, they begin to migrate along the Yellow River to Pangkou Bay for spawning. Pattern II encompasses P9, P12, and P13, which hatch in freshwater habitats; as these individuals grow, there is an abrupt change from Stage 1 to Stage 2, but their life history does not extend to marine habitats with high Sr/Ca values, and after about 1 year, they migrate along the Yellow River to Pangkou Bay for spawning. Pattern III includes P6, P8 and P10, which also hatch in freshwater habitats and experience abrupt changes; however, the mapping analysis reveals a large area of red and yellow concentric rings, indicating a history of seawater habitat and an extension of their life history to Laizhou Bay. Pattern IV is represented by P11, whose living environment was relatively stable, with no significant abrupt changes and no migratory life history characteristic, which presumed to be a freshwater settlement type that passively entered the Yellow River due to the flood season of Dongping Lake. Pattern V is exemplified by P7, whose analysis results show two trips to freshwater and brackish water habitats, both of which produced significant pattern changes which indicates that it conducted a reproductive migration at the first instar, swam to the Yellow River estuary after spawning, and migrated to Pangkou during the reproductive period of the following year to lay eggs until it was captured. This study demonstrates that most individuals in Pangkou Bay are of the migratory type. Compared with the sexual maturity of individuals in other waters of the Yangtze River basin, Pangkou Bay is identified as an important spawning ground for the migratory type of C. nasus.