Journal of Applied Ichthyology最新文献

We investigated the gastric evacuation rate (GER) and maintenance ration (MR) for the adult pointhead flounder Cleisthenes pinetorum (77–421 g) at 4°C, 9°C, and 14°C which reflect the bottom, middle, and surface temperatures of their habitat in early summer. GERs were obtained from gravimetric experiments with 34 flounders fed juvenile walleye pollock Gadus chalcogrammus as prey. A 169-day feeding experiment for 67 pointhead flounders fed krill Thysanoessa inermis was undertaken to measure MR. The effects of a 10°C temperature increase (Q₁₀) on the GER and the MR were 6.55 and 2.04, respectively, indicating that the effect of temperature was greater on GER than on MR. As a result, the differences between the GER and MR, indicating the maximum amount of food ingestible for growth, were 2.8 and 30.7 cal·g⁻¹ day⁻¹ at 4 and 14°C, respectively. The water temperature on the sea floor generally remained at <4°C from winter through summer, but exceeded 10°C in the surface layer of Funka Bay, where pointhead flounders were sampled. Therefore, their growth rate should be considerably limited if they remain in the bottom layer. The unique ecology of this species among the flatfishes of floating from sea floor and feeding at pelagic zones may represent a strategy to compensate for the physiological limitation of growth at low temperatures.

To determine sex and maturity stages accurately without any physical injury and stress, especially for sensitive and high-value fish species, employing a noninvasive ultrasound imaging technique could be a desirable approach. The ultrasound imaging method as a powerful eco-friendly tool was established to determine sex, gonad volume, gonadosomatic index (GSI), and reproductive stages in the Indian shad, hilsa (Tenualosa ilisha). About 30 hilsa (15 males and 15 females) of different maturity stages were collected from the river Ganga round the year using gill nets. The ultrasound sonography (USG) was then employed in hilsa to determine the computed GSI. The fresh gonad volume of hilsa was determined using a water displacement method to ascertain actual GSI values. There was no significant difference between the calculated, real, and actual GSIs (P > 0.05) in both males and females. The validation of the precise maturity stages of ultrasound images of the gonad by the histological architecture indicated that USG images of the hilsa gonad depicted exact stages of maturity in both sexes except for stages I and II in males. The sex of the fish was accurately ascertained using ovarian ultrasound scanning for all the specimens. The calculated USG-based ovarian volume was positively correlated (R² = 0.97) with the actual and real ovarian volumes. The noninvasive and reliable ultrasonography technique was found to be an accurate and valid tool to track gender and gonadal development and predict the spawning periodicity in hilsa.

The freshwater bodies of Nepal host a great deal of fish diversity; however, the molecular study of Nepalese fish is still in its early stages. Conservation management tactics require knowledge of the real species composition, often impeded by descriptions of intermittent species based on traditional taxonomy. Catfish, one of the most overfished taxa on the planet, are abundant and heavily exploited in the eastern region of Nepal. Hence, actual catfish diversity in this region needs to be examined using a combined morphological and molecular DNA barcoding approach. In this study, we sequenced the cytochrome oxidase subunit I (COI) gene in Nepalese fish species for the first time and used it for molecular identification. Altogether, 99 specimens representing 29 species belonging to 21 genera and 8 families were successfully barcoded. They were found to be 98.5–100% identical to the known sequences deposited in the GenBank and BOLD databases. Of these, two species, Amblyceps arunachalense and Erethistoides sicula, were recorded for the first time in Nepal. Out of 29 species, one species was found to be Endangered, one species under Vulnerable, two species under Near Threatened, one species under Data Deficient, and 24 species under Least Concern. The intraspecific genetic distances within species ranged from 0 to 5%. The highest intraspecific genetic distances (Kimura 2-parameter) were found among the individuals of two species, namely, E. sicula (4%) and Glyptothorax telchitta (5%), indicating the presence of putative (sub)species. The interspecific genetic distances among the catfishes in eastern Nepal ranged between 8.47% (between Glyptothorax trilineatus and G. cavia) and 26.38% (between Amblyceps arunachalense and Chaca chaca). The GC content at the 1^st, 2^nd, and 3^rd positions of the codons was found to be 42.4%, 49.3%, and 43.8%, respectively. These findings will support future initiatives for fish resource inventory, monitoring, and management. It is also an important input to the DNA barcode library of catfish in the eastern region of Nepal.

The black jewfish (Protonibea diacanthus) occurs in tropical coastal waters throughout the central Indo-Pacific. It has long been valued as an important recreational and artisanal fishery species but has become increasingly targeted by commercial fisheries due to demand for its large swim bladder. To better understand how changes in fishing pressure may impact the sustainable exploitation of P. diacanthus populations throughout Eastern Australia, we evaluated the reproductive biology of the species across two management regions in Central Queensland. Reproductive characteristics studied included the size at maturity, fecundity, spawning mode, and season. Spawning periodicity was evaluated throughout the two major management regions and revealed an increase in the gonadosomatic index during the early austral spring, followed by evidence of spawning occurring from September through March with a peak from September to November. Females were found to produce ∼4.5 million ± 1.4 million oocytes (mean ± SE) per batch. Spawning periodicity did not vary latitudinally but was found to differ from other regions in northern Australia. The present study provides reliable maturity and fecundity information to improve future assessment and sustainable management of P. diacanthus.

This study utilized the length-based spawning potential ratio (LBSPR), a data-limited model, to assess the stock status of three fin fish species in the northern South China Sea. The analysis used the “LBSPR” package in R software, incorporating catch-length data of the study species and life history ratios. The results revealed a depletion of the stock’s reproductive biomass for S. undosquamis and imminent risks of stock collapse for P. macracanthus, with SPRs of 10% and 19%, respectively. In contrast, N. virgatus exhibited a relatively high SPR of 32%, surpassing the limit reference point (LRP) (20%). This study identified high fishing pressure (F/M) and the prevalence of destructive fishing practices as contributing factors to stock depletion. Effective management strategies, such as implementing stricter mesh size regulations, reducing catch limits, and reducing fishing efforts, are essential for addressing these issues. Adopting sustainable practices with an SPR target of 40% could lead to economic benefits for N. virgatus. Immediate interventions are crucial for P. macracanthus and S. undosquamis to prevent further declines. Continuous monitoring of the SPR, adaptive management, and active stakeholder engagement are vital for ensuring compliance with conservation measures and achieving long-term sustainability in the region.

The rice-fish system has gained significant interest in recent years because of its effective usage of limited land and freshwater resources. To scientifically guide the improvement of rice field fishery production, the data in this study were selected from the latest China Fishery Statistical Yearbook, and therefore the development of paddy aquaculture was investigated. In order to more precisely predict the production of rice-fish in China, this paper introduces an artificial neural network with the SSA-BP model, which solves the drawbacks of the BP neural network such as easy to fall into local optimum and slow convergence speed when it is used for prediction. Firstly, the SSA-BP model incorporates the aquaculture area (split by water area), the national freshwater fish seedling output, the national end-of-year ownership of inland fishing vessels, the number of freshwater fisheries practitioners as input variables, and the production of rice-fish as an output variable; secondly, the SSA optimization algorithm was used to find the optimal initial thresholds and weights for the BP neural network, and finally the SSA-BP prediction model was constructed. The results revealed that the overall expansion of the rice field fishery was swift in the last five years, and the output of cultivated fish in China’s rice fields rose by nearly 20% yearly in the past five years. Compared with the BP neural network and GA-BP models, the accuracy of the SSA-BP prediction model was enhanced by 61.01% and 16.15%, respectively, which was more suited for predicting the production of rice-fish.

Efficient conservation efforts for valued fish species such as Bangana devdevi, a medium-sized minor carp prevalent in Southeast Asian countries, can be facilitated through well-established artificial breeding techniques. This study aimed to investigate the reproductive biology of B. devdevi and focused on optimizing hormone dosages for breeding purposes for the first time. The research findings indicated that the highest gonadosomatic index (GSI) for males (1.17) was observed in August, while for females, it peaked in July (2.24). Female fish exhibited absolute fecundity ranging from 2089 to 26287 eggs, corresponding to body weights ranging between 10.46 and 153.73 g. The relative fecundity ranged from 170 to 298 eggs g⁻¹ of body weight. To induce breeding, female brooders were administered Gonopro-FH hormone through three experimental groups: G-FH_0.4, G-FH_0.5, and G-FH_0.6, with doses of 0.4 mL, 0.5 mL, and 0.6 mL·kg⁻¹ of body weight, respectively. Spawning occurred within 6–10 h after hormone administration. Among these groups, G-FH_0.5 exhibited the highest fertilization rate (94.25%) and hatching rate (89.03%), significantly surpassing the rates observed in G-FH_0.4 and G-FH_0.6 (p < 0.05). This study provided valuable insights into the reproductive biology of B. devdevi and emphasized its potential application in developing management and conservation strategies for this species in rivers and tributaries. Furthermore, the knowledge gained from induced breeding holds promise for future large-scale seed production initiatives.

Desiccation due to air exposure is a common environmental stress that harms the health of crustaceans. How crustaceans respond to air exposure remains largely unclear. In this research, we explored the physiological responses and gene regulation under air exposure of an invasive species Procambarus clarkii, which is the most commonly cultured freshwater crustacean in China. Toll3 belonging to the Toll-like receptor family and proPO in the prophenoloxidase-activating system were two important immune responses to air exposure. In addition, air exposure can also influence ammonia metabolism via regulating the expression of the key genes. Prx6 and proPO showed quick responses and high sensitivity to air exposure, suggesting the potential to be the biomarker for desiccation stress assessment in crayfish. The results of this research can provide useful information for monitoring desiccation stress, as well as transport and sale management in red swamp crayfish.

Petroleuciscus borysthenicus is a species with a wide distribution from the eastern, western, and northern Black Sea and Azov Sea basins, the Aegean Sea basin, and Northwestern Türkiye. However, there has been relatively little attention on the genetic variability of this species in their native distribution range, and nearly no study has been conducted in Türkiye despite its importance in biodiversity. The aim of this study was to elucidate the genetic variability and population structure of P. borysthenicus from Northwestern Türkiye using an integrated molecular method. A total of 72 specimens were collected from 13 localities in the Northwestern part of Türkiye. A total of six haplotypes were identified in all specimens. A relatively low level of genetic variability was found for P. borysthenicus throughout the study region based on the indices of genetic diversity including haplotype diversity and nucleotide diversity for the cytochrome oxidase subunit I (h = 0.507, π = 0.0027). The pairwise F_ST values between the samples ranged from −0.123 to 1.000. Furthermore, our results revealed no provable recent demographic expansion for P. borysthenicus from Northwestern Türkiye. However, more studies using additional geographic sampling and molecular analysis are needed to enhance our knowledge of the diversity and distribution of this species.

Sebastes schlegelii is a species of great economic significance in Zhangzi Island’s waters in the Northern Yellow Sea. Since the beginning of the 21^st century, there has been a significant decline in the fishery resources of Sebastes schlegelii, and the reduction in size has become increasingly apparent. Therefore, it is imperative to understand the characteristics of Sebastes schlegelii and develop management tactics. Based on biological data from Sebastes schlegelii collected in Zhangzi Island’s waters, an analysis was conducted on the relationship between body length and weight, growth equations were formulated, and an assessment was made of the resources’ status. The study simulated and evaluated the effects of various closed season management strategies on egg production per recruit (EPR) and spawning biomass per recruit (SBR). The results showed the following. (1) The length-weight relationship was W = 5 × 10⁻⁵L^2.882. (2) Von Bertalanffy’s growth equation was L_t = 450[1 − e^{−0.31(t+0.42)}] and W_t = 2215.8[1 − e^{−0.31(t+0.42)}]^2.882. (3) The resource is in an overfished state with an exploitation rate (E) of 0.737, a steady-state biomass of 1471 t, and a maximum sustainable yield of 466 t. (4) The closed season for Sebastes schlegelii in Zhangzi Island’s waters is suggested to be from November to February, coinciding with the recovery of the EPR value to 68.33% and the SBR value to 29.53%.