Journal of Applied Ichthyology最新文献

The Oujiang River, the second-largest river in Zhejiang Province, southern China, supports rich fishery resources. However, these resources have experienced significant decline due to multiple anthropogenic and environmental pressures. To assess the current status of fishery resources, this study investigated the length–weight relationships (LWRs) and length-length relationships (LLRs) of 11 economically and ecologically important fish species. The results showed that the b values ranged from 2.534 to 3.469, with the coefficient of determination (r²) ranging from 0.893 to 0.987. Notably, we provide the first LWR and LLR records for Acrossocheilus fasciatus and Microphysogobio oujiangensis in FishBase, along with a new maximum length record for Onychostoma barbatulum. These findings offer valuable baseline data to inform science-based conservation and sustainable management of fisheries in the Oujiang River.

As a vital tributary of the Poyang Lake system, the Xinjiang River plays a crucial role in maintaining regional aquatic biodiversity and sustainable fisheries. However, anthropogenic pressures and climate change have led to significant degradation in fish community structure, including declining species diversity and population miniaturization. This study presents the first systematic evaluation of length–weight relationships (LWRs) for 11 native fish species in Xinjiang River, filling an important gap in fundamental biological data for this region. Fish samples were collected from 10 sampling sites between June and September 2022. LWR parameters (W = aL^b) were determined using Le Cren’s log-transformation method, with 95% confidence intervals and coefficients of determination (R²) calculated. Results showed that the allometric coefficient (b) ranged from 2.24 to 3.28 among the 11 Cyprinidae species, with Hemiculter bleekeri and Toxabramis swinhonis exhibiting significant negative allometric growth (b < 3). All species demonstrated high model fit (R² > 0.95). This study reports the first LWR records for Megalobrama skolkovii and T. swinhonis in FishBase and reveals spatial variations in growth patterns compared with other Yangtze tributaries, likely reflecting ecological and anthropogenic influences. These findings provide essential data for evidence-based fisheries management and conservation strategies in the Xinjiang River basin.

Traccatichthys is a genus of small benthic omnivorous nemacheiline loaches, with limited ecological and biological data available. Here, we described length–weight relationships (LWRs) for four Traccatichthys species from southern China. Fishes were sampled using stationary fish cages (10 m in length, mesh size: 0.5 cm) between January and April 2025 at four selected sampling sites. All specimens were transported to the laboratory within 2 days of collection, maintained alive in oxygenated water, and measured for total length (TL) to the nearest 0.1 cm and body weight (BW) to the nearest 0.01 g in the laboratory. LWRs were calculated using linear regression, and the four species-specific models were all highly significant (p < 0.001). The allometric exponent b values ranged from 2.875 to 3.196. The LWRs for three species (T. tuberculum, T. zispi, and T. taeniatus) are new to FishBase (as of May 2025). Our results provide essential baseline data for sustainable management and ecological research of these species.

This study developed predictive models using generalized linear statistical analyses to estimate Atlantic bonefish (Albula vulpes) fork length (FL) dependent on four head morphometry covariates: snout length, eye diameter, postorbital head length, and head length. A total of 257 South Florida bonefish were examined, which ranged from 28 to 720 mm FL. Each of the morphometric measurements was highly correlated with FL, with coefficients of determination (r²) that ranged from 0.9592 for eye diameter to 0.9959 for head length. Total length (TL) was also highly correlated with FL. Sex differences in the morphometric measurements were examined; however, no significant sexual dimorphism was detected. All of the morphometric measurements examined were good predictors of Atlantic bonefish FL and TL.

To assess the changes in genetic structure across generations of selectively bred largemouth bass (Micropterus nigricans) (F3, F4, F5, and F6), this study, in combination with an introduced population, utilized 15 pairs of microsatellite primers to analyze the genetic diversity and structure. The results revealed a total of 62 alleles (N_a), with an average of 4.160 alleles per locus. The average observed heterozygosity (H_o) was 0.559, and the average expected heterozygosity (H_e) was 0.529. The introduced population exhibited the highest genetic diversity parameters, including polymorphic information content (PIC), N_a effective number of alleles (N_e), H_o, H_e, and Shannon’s information index (I). In contrast, the selectively bred populations showed a gradual decline, with PIC ranging from 0.398 to 0.494, N_a from 3.533 to 4.000, N_e from 2.008 to 2.387, H_o from 0.480 to 0.589, H_e from 0.457 to 0.550, and I from 0.794 to 0.990, indicating a moderate level of polymorphism. The F-test in different generations of selectively bred populations revealed that 10 loci had negative inbreeding coefficients (F_is), while 5 loci had positive values, suggesting a low level of inbreeding across generations. Overall, the introduced and selectively bred populations exhibited a moderate level of genetic differentiation, with low to moderate genetic differentiation observed. AMOVA revealed that 92% of the variation originated within individuals. UPGMA clustering and PCoA analysis demonstrated significant genetic differentiation between the selectively bred populations and the introduced population. In conclusion, the introduced population exhibited higher genetic diversity compared to the selectively bred populations. The genetic diversity of the selectively bred populations showed a declining trend as the selection process progressed, highlighting the importance of evaluating genetic diversity while improving target traits during selection. This study provides scientific guidance for the selection of new varieties and the evaluation and conservation of germplasm resources in largemouth bass.

The European eel (Anguilla anguilla L. 1758) is a migratory fish species whose populations have undergone a severe collapse in numbers in recent decades. Infectious diseases are one of the factors contributing to the decline of European eels. One hundred and eighteen eels from four Spanish Mediterranean sites were captured and analysed for Anguillicoloides crassus, anguillid herpesvirus 1 (AngHV1), rhabdovirus Eel Virus European X (EVEX) and aquabirnavirus Eel Virus European (EVE). The nematode A. crassus and AngHV1 were present in eels from all four sampled wetlands, which indicates that these two pathogens are commonly occurring in Mediterranean ecosystems. The global prevalence (eels from the four wetlands) of the later parasite stages (L3, L4 and adults) was 74.58%. The global prevalence of all parasite stages (L2, L3, L4 and adults) was 93.22%. The global prevalence of the AngHV1 virus was 27.7%. EVEX was only detected in eels from two of the four wetlands (12.87% global prevalence), while EVE was not detected in any sample. At the population level, pathogens seem to represent a serious threat to eels in L’Albufera de Valencia: 92.31% of specimens were co-infected by AngHV1 and EVEX and 84.62% of specimens were triple co-infected with AngHV1, EVEX and any stage of A. crassus. Further studies are necessary to understand the impact of diseases, together with other anthropogenic factors (pollution, salinity, climatic change, etc.), on eel status in Mediterranean ecosystems.

The pallid sturgeon Scaphirhynchus albus, a large, long-lived fish endemic to the Missouri and Mississippi River Basins, was listed as a federally endangered species in 1990 due to population declines driven by profound anthropogenic habitat alterations, including river fragmentation by dams and channelization. In contrast, its congener, the shovelnose sturgeon Scaphirhynchus platorynchus, remains common in large rivers and their tributaries, such as the Des Moines River. Historically, the pallid sturgeon’s range in Iowa has been limited to the Missouri River along the state’s western border. Recovery efforts, as outlined in the National Pallid Sturgeon Recovery Plan, have emphasized habitat restoration and conservation stocking to prevent extirpation and to support natural recruitment. Here, we document the first verified records of wild (nonstocked) pallid sturgeon in the Des Moines River, Iowa. This represents a potential expansion of the species’ known contemporary range and occurs within a tributary not previously identified as occupied habitat. This finding underscores the potential for stocked or wild individuals to disperse into novel river systems where previously undocumented habitat may be available. The finding has immediate conservation implications under the Endangered Species Act, prompting a reassessment of the Des Moines River’s management strategies and necessitating enhanced, targeted sampling efforts. It also raises concerns under the Act’s Similarity of Appearance clause, which governs the legal commercial take of shovelnose sturgeon in the pooled reach of the Upper Mississippi River downstream of the Des Moines River confluence, a potential migration corridor. The presence of pallid sturgeon in the Des Moines River demonstrates that even highly altered river systems can provide essential habitat, such as suitable spawning substrate, needed to support their life cycle, particularly when stream flow is managed to approximate natural hydrologic patterns.

Aquaculture is an emerging sector in meeting global food demands, with significant potential to accelerate fish production. However, a major bottleneck in this industry remains the challenge of fulfilling the complex nutritional needs of fish larvae, often limited by the high cost and scarce availability of appropriate feed sources. In this study, we explored the potential of live microalga Desmodesmus sp. and nutritionally enriched copepods, administered at different concentrations, as alternative dietary supplements to enhance the growth performance and survival rate of the mrigal, Cirrhinus cirrhosus larvae. The fish larvae were reared for a period of 30 days under six feeding regimes (treatments): T₁ (10–13 × 10⁴ cells mL⁻¹ live Desmodesmus sp.), T₂ (7.5–9.5 × 10⁴ cells mL⁻¹ live Desmodesmus sp. + 5–10 individuals mL⁻¹ enriched live copepods), T₃ (5–6.5 × 10⁴ cells mL⁻¹ live Desmodesmus sp. + 10–20 individuals mL⁻¹ enriched live copepods), T₄ (2.5–3.25 × 10⁴ cells mL⁻¹ live Desmodesmus sp. + 15–30 individuals mL⁻¹ enriched live copepods), T₅ (20–40 individuals mL⁻¹ enriched live copepods), and T₆ commercial feed (0.5–1 gL⁻¹) as a control diet under laboratory environments. The T₃ diet exhibited the highest protein (17.87%) and fat (2.89%) content in the fish larvae, significantly higher than the control diet T₆ (16.63% protein, 2.28% fat). The T₃ diet significantly improved the larval growth in terms of gain in length (17.34 mm), gain in weight (118.81 mg), percent gain in length (299.69%), percent gain in weight (10,069.49%), and specific growth rate (15.83%). The highest survival rate was observed in T₃ (92.55%), followed by T₄ (90.15%), T₅ (85.48%), T₆ (84.21%), T₂ (82.44%), and T₁ (69.43%). This study highlights the potential of the combined Desmodesmus sp. and enriched copepods as diets for the rearing of mrigal larvae with an aim of sustainable aquaculture development.

Length–weight relationship (LWRs), length–length relationships (LLRs), and relative condition factor (Kn) are fundamental biological indices for fisheries stock assessment, sustainable management, and monitoring ecosystem health. This study determined the LWRs, LLRs, and Kn of three ecologically important fish species: the straightfin barb Enteromius paludinosus, the stone-lapping minnow Garra quadrimaculata, and the black lampeye Aplocheilichthys antinorii from Lake Hawassa, Ethiopia. A total of 1,420 samples (449 E. paludinosus, 176 G. quadrimaculata, and 795 A. antinorii) were collected using beach seine and hand nets in two rainy (May and June) and two dry (October and November) months of 2023. The data were analyzed using MS Excel Office 10 and IBM SPSS 27 software. The results showed that the LWRs of all considered species have a strong relationship (r²  = 0.96, 0.95, and 0.85) for E. paludinosus, G. quadrimaculata, and A. antinorii, respectively, and exhibit strong nonlinear relationships. The growth exponent (b) of G. quadrimaculata showed positive allometric growth (b > 3) and was significantly different from three (p < 0.05). However, E. paludinosus and A. antinorii showed negative allometric growth (b < 3) and were significantly different from the cube value (p < 0.05). Regarding their LLR, the coefficient of determination showed a very strong correlation (r² > 0.95) and linear relationship. No significant differences in Kn were found between sexes for E. paludinosus, G. quadrimaculata, and A. antinorii (p > 0.05). The mean relative condition factor (Kn) of all species displayed  > 1, indicating favorable Kn relative to the population average during the study period. This study provides essential baseline biological parameters for E. paludinosus, G. quadrimaculata, and A. antinorii in Lake Hawassa.

The Chinese sturgeon (Acipenser sinensis), a critically endangered anadromous species endemic to the Yangtze River, has undergone severe population decline due to habitat degradation and anthropogenic disturbances. To improve monitoring under low-abundance conditions, this study applied environmental DNA (eDNA) analysis using species-specific primers and SYBR Green quantitative PCR to investigate the spatiotemporal distribution of A. sinensis in the Yangtze River Estuary and adjacent coastal waters in May and August 2024. eDNA was detected at all sampling sites, with higher copy numbers generally observed in May, particularly in nearshore waters between Chongming and Changxing Islands. Generalized linear modeling indicated that eDNA concentrations were most closely associated with moderate temperatures, high dissolved oxygen, and slightly alkaline pH, while signal intensity declined under warmer and oxygen-poor conditions. Elevated eDNA values in May coincided with the timing of upstream release events, although the absence of prerelease baseline data prevents direct attribution to stocked individuals. Overall, the findings provide preliminary insights into seasonal habitat associations of A. sinensis in estuarine ecosystems and demonstrate the potential of eDNA as a sensitive and noninvasive tool for long-term monitoring and conservation assessment of endangered aquatic species.