Journal of Applied Ichthyology最新文献

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%.

Length-weight relationship (LWR) studies are important for fish taxonomical analysis, ecological assessments, management, and conservation practices. Although LWR studies can use measurements of either fresh or preserved specimens, few studies have directly compared these methods. This study analyzed the effect of preservation on LWR of ten small-sized freshwater fish species from the Curaray River basin (Napo Basin), eastern Ecuador. 255 wild specimens were measured, weighed, fixed in formalin, and finally preserved in 70% ethanol. 287 specimens from the same species batch were measured again after preservation. We estimated LWR curves with linear regressions and compared slopes and intercepts between fresh and preserved specimens. The preservation process altered weight significantly for all ten species and altered both weight and length for two species. The magnitude of change varied according to the morphology and maximum size of each species. Smaller individuals exhibited greater proportional weight losses. LWR estimates for eight of the species are new to science. These results present new evidence of the preservation effects in LWR studies as well as a compilation of the varying results reported in the literature. We conclude that measurements on fresh specimens should be encouraged for LWR studies. However, recognizing that this is not always feasible, studies using preserved specimens should consider the effects of preservation on body length and weight.

The Qiantang River, located in Zhejiang Province, China, is a crucial water resource with significant ecological and economic importance. This study aimed to evaluate fishery resources in the Qiantang River Basin by analyzing the length-weight relationships (LWRs) and length-length relationships (LLRs) of 14 fish species. Fish samples were collected between July 2021 and November 2023 using multipanel nylon gillnets and cage nets. Each specimen was measured for total length (TL) and standard length (SL), as well as weighed. Linear regression models were employed to estimate LWRs and LLRs, with statistical tests revealing significant relationships (P < 0.05) and high R² values above 0.91. The study contributed new LWRs for two species and LLRs for three, deepening our understanding of their biology. These findings enriched FishBase and offered valuable data for fish stock assessments and management strategies in the Qiantang River Basin. Future research can utilize this foundation to explore population dynamics and promote sustainable management practices.

Growth stagnation in early-maturing fish is a concern for higher fish productivity and may be regulated with reproductive arrest using phytochemicals. In this line, the study attempts to improve the growth of silver barb, Barbonymus gonionotus, through dietary pawpaw (Carica papaya) seed (PS) supplemented diets during a 60-day trial (30-days of feeding PS, followed by a 30-day recovery period). Four levels of PS at 0, 2, 4, and 6 g kg⁻¹ diet were added to a commercial feed (32% crude protein) and fed to advanced fingerlings (19.08 ± 0.02 g) at 3% body weight, which forms the experimental groups, designated as control, T1, T2, and T3. Subsequent alterations in growth (% weight gain and specific growth rate), reproduction (gonadosomatic index (GSI) and gonadal histology), and physiological function (haematology and stress biomarkers, viz., cortisol and glucose) were examined at the end of the experiment. Observations noted at the end of the trial showed significantly (P < 0.05) enhanced growth in groups fed 2 g kg⁻¹, but not significantly with control. GSI showed an extreme reduction in all groups as the level of supplementation increased with the lowest being noted in T3. Sex change was observed in T2 and T3, wherein only male populations were noticed. Gonadal histology demonstrates tissue-level generation in T1, compared with control. Tissue alteration (atrophy and necrosis) was noticed in the T2 and T3. The haematological profile indicates a gradual decrease in erythrocyte and leucocyte counts, packed cell volume, and haemoglobin in the T2 and T3 groups, compared with the T1 and control groups (P < 0.05). Serum biochemistry followed a similar trend. The levels of blood glucose and cortisol were higher in T2 and T3 (P < 0.05) than in the control and T1. The overall findings from this study reveal that dietary PS supplementation at 2 g kg⁻¹ can enhance the growth of silver barb; however, higher doses suppress both growth and reproductive function, resulting in subsequent disturbances in physiology. Further studies regarding the molecular mechanism of such an outcome warrant immediate investigation.