Journal of Applied Ichthyology最新文献

Global climate change significantly influences environmental temperature, affecting the feeding patterns, growth, and overall health of fish. Understanding how fish respond to thermal changes is crucial, particularly for growth and stress response in aquaculture. This study examines the effects of different acclimation temperatures on the expression of stress, appetite, and growth-related genes in Nile tilapia (Oreochromis niloticus). Quantitative real-time PCR method was employed to analyze the expression of genes for growth hormone (gh) from the pituitary, insulin-like growth factors (igf1 and igf2), ghrelin, and heat shock proteins (hsp70 and hsp90) from the liver of juvenile Nile tilapia acclimated to 31°C (control), 34°C, and 37°C for 14 days. Results revealed that the expression of hsp70 and hsp90 as well as the level of blood glucose were significantly upregulated at 37°C in both males and females, indicating a pronounced stress response due to higher acclimation temperature. Conversely, the expressions of gh, igf1, and igf2 were highest at 34°C, stimulating metabolic processes and promoting somatic growth. In comparison, significantly lower expression of these genes was observed at 37°C, suggesting an inhibitory effect of higher temperatures on growth processes. Expression of ghrelin followed a similar pattern to that of GH and IGFs with higher levels at 34°C correlating with increased appetite and growth, but a decreased expression at 37°C, indicating reduced feeding activity resulting from thermal stress. These findings underscore the critical role of maintaining optimal temperatures in aquaculture settings and provide valuable insights into the physiological mechanisms underlying thermal adaptation in Nile tilapia under varying environmental conditions.

Growth rates are generally obtained from back-calculation of increments of otolith readings and based on the assumption that mean annual growth can be scaled directly to the distance between age rings. Although otoliths continue to grow even when somatic growth ceased. To analyse growth rates of yellow eel, a passive integrated transponder (PIT) mark-recapture study was performed in four water bodies (Delfland, Markiezaatsmeer, Süderpolder and Vinkeveense Plassen) in the Netherlands. PIT-tags were used as an alternative method instead of the generally applied back-calculation of annual increments from otolith readings. During 2017–2020, 2209 eels were tagged individually and in the subsequent years, 541 eels were recaptured. The mean annual growth rate decreased with increasing length of eel, with growth rates of 2.2–8.8 cm/year for undifferentiated (sex undetermined) eel between 30 and 50 cm and 1.3 and 5.7 cm/year for female eel between 50 and 80 cm. Differences in growth rate were also observed between the four water bodies, which having consequences to population demographics, such as age at first maturity.

Water pollution resulting from petroleum derivatives, notably diesel fuel oil, has emerged as a significant environmental concern recently. The experiment was conducted to find out the impact of diesel oil on morphology, behavior, and changes in internal organs i.e., heart, intestine, kidney, and liver in Nile tilapia (Oreochromis niloticus). There were controls and three groups of Nile tilapia (Oreochromis niloticus) exposed to 0 mL/L (control), 0.5 mL/L, 1.0 mL/L, and 1.5 mL/L of diesel for 15 days. Several morphological changes such as a broken fin, rough scale, increased mucous, and discolored gill were recorded. The treated fish displayed erratic swimming patterns, rapid operculum movements, and hovering in the water column, displaying signs of weakness whereas the untreated (control) remained calm and normal. Probit analysis revealed that the mortality rates were increased significantly (p < 0.05) with the increase of diesel concentrations. Multiple histopathological abnormalities were found and they were fragmentation of myocardial muscle fiber and formation of degenerative vacuoles in the heart; degeneration of epithelium, submucosa, and hemorrhage in the mucosa of the intestine; hemorrhages of glomerulus and dilation of tissues in the kidney; and enlargement of central vein, degeneration of hepatocyte, dilation of the sinusoid, hemorrhage, vacuolization of hepatocytes, necrosis, and thickening of the hepatocytic cells in the liver. This study also concluded that the dissolved oxygen levels decreased with the increase of oil concentrations, which led to poor water quality and had a significant effect on morphology, behavior, histology, and mortality. This study will grow social awareness and people will handle commercial diesel oil properly during transportation. Thus, the present findings might be helpful to save aquatic animals as well as aquatic environments.

Climate change is causing saline intrusion, negatively affecting aquaculture productivity on a global scale. It is necessary to explore suitable species for coastal aquaculture in water with low to moderate salinity. Thus, the objective of the present study was to assess the impact of salinity on the growth performance, muscle composition, and blood parameters of a farmed fish, Gangetic mystus (Mystus cavasius). For this experiment, the fingerlings were raised in the aquarium for 60 days. Three distinct salinities, specifically 3, 6, and 9 parts per thousand (ppt), were employed for treatment 2 (T2), treatment 3 (T3), and treatment 4 (T4), whereas treatment 1 (T1) was referred to as the control with a salinity of 0 ppt. Increasing salinity did not have any influence on the water quality parameters. The survival rates were 97.5 ± 0%, 96.25 ± 1.25%, 92.5 ± 2.5%, and 90 ± 5% for T1, T2, T3, and T4, respectively. The highest specific growth rate (SGR) and the percentage of weight gain (PWG) and the lowest food conversion ratio (FCR) were recorded at T1. T2 and T3 showed descending values for SGR and PWG and ascending values for FCR. Moreover, the body protein percentage reduced by about 2%, and lipids increased by 13% in T3 compared to T1. RBC and Hb exhibited an inverse relation with increasing salinity, whereas WBC and glucose displayed an opposite trend due to stressed conditions. Thus, the study implies that while salinity does hinder growth performance and compromise the immune system to some degree, M. cavasius is capable of enduring salinity levels of up to 6 ppt while maintaining a satisfactory survival rate.

Bosten Lake is an important inland freshwater lake in China, which is rich in fishery resources. However, due to various factors, its fishery resources have declined. The length–weight relationship (LWR) is of great significance for fish research and fishery management. This study was based on the samples of 17 freshwater fish species collected from 10 sampling points in Bosten Lake from March 2023 to November 2024. The LWRs were determined, the regression parameters and the coefficient of determination (R²) were calculated, and the fish condition factor BW/TL³ was analyzed. The results showed that the b value of the LWR parameters of the 17 freshwater fish species ranged from 1.262 to 3.665. The b values of most fish species were within the expected range. The LWRs of all fish species were significantly different (p < 0.05), and the R² values ranged from 0.746 to 0.999. The LWR of Aristichthys nobilis was the strongest, and that of Rhodeus ocellatus was the weakest. This study reported for the first time the LWRs of Channa argus in the lake, and its b value was the highest, and the growth pattern was related to its ecological niche. The research results provide basic data and theoretical basis for fish ecology research, fishery resource management, and lake ecological protection.

Artificial expansion of shipping routes in the course of international trade opens up fish migration routes for numerous species. Since 2006 migration of four different goby species took place from the Ponto–Caspian region to the Lower Rhine. Neogobius fluviatilis, Neogobius melanostomus, Proterorhinus semilunaris and Ponticola kessleri were able to establish in the local fish community of the Lower Rhine. Besides the four other goby species, Knipowitschia caucasica migrated from the Ponto–Caspian region to the Lower Rhine as well in 2019. Due to increasing abundance in the last years and lack of information regarding population dynamics, feeding activity and prey preferences of the dwarf goby, the length of 1218 Caucasian dwarf gobies was analysed as well as the diet of 519 individuals in the course of May 2021 to February 2022. The populations of three different locations along the Lower Rhine were examined in winter on differences in population dynamics and feeding ecology. Analysis of the population over time suggests that K. caucasica in the Lower Rhine is an annual species with spawning during summer. The juvenile individuals of the Caucasian dwarf goby increased in total length until winter, while the adults vanished after spawning. Both juveniles and adults mainly fed on zooplankton and insect larvae. The feeding activity of the dwarf goby was higher in summer than in winter and started to increase as early as February. No difference in winter prey was recorded between populations at different sites, as all populations fed mostly on copepods and chironomids.

Establishing length–weight relationships (LWRs) is essential for conserving fish populations, especially where gaps hinder efforts, particularly crucial for elasmobranch populations in the Gulf of Guinea. This study presents LWRs established for six species of elasmobranchs landed by artisanal maritime fishing in Mayumba, located in the south of Gabon. The data were collected in May 2022 and between September 2022 and March 2023. This work provides the first LWRs for six elasmobranch species that have not yet been referenced at the regional level. One of these species, Paragaleus pectoralis, lacks referenced data on FishBase.

Caohai Lake, hailed as a gem on the Yunnan–Guizhou Plateau, is currently being faced with serious biological invasion threats. Among the most influential invasive species, the Procambarus clarkii (Girard, 1852) is causing various adverse effects on the lake’s ecosystem. However, there has been little attention paid to this issue for a long time. In light of this, this study conducted a sample collection in August 2022 to investigate the total length–weight relationships (LWRs) and condition factors (K) of the target species with the aim of providing fundamental data for the upcoming ecological restoration in Caohai Lake. The results are as follows: (1) P. clarkii was distributed throughout the lake, with females exhibiting larger body sizes than males; (2) the LWRs were expressed as: W_♂ = 2 × 10⁻⁶TL^3.66 (R² = 0.90 and n = 227); W_♀ = 4 × 10⁻⁶TL^3.39 (R² = 0.95 and n = 259), both showing positive allometric growth pattern and indicating, the weight gain rate of males is significantly faster than that of females during the growth period; (3) the K was 0.27 ± 0.04%, indicating robustness in P. clarkii in the lake. These findings underscore that urgent scientific measures should be taken to handle the rapid invasion of P. clarkii in Caohai Lake.

The population size structure and length–weight relationships (LWRs) are fundamental tools in fishery science, providing valuable insights into the health, dynamics, and management of fish populations and contributing to the sustainable use of aquatic resources. The data used in this study were estimates from the main small pelagic fishes exploited in the Gambia. They were collected using surface and bottom gillnets between November 2020 and October 2021 during scientific fishing operations. The main small pelagic fish size composition showed a modal class of 20 cm for Ethmalosa fimbriata, 21 cm for Sardinella aurita, 22 cm for Sardinella maderensis, and 30 cm for Trachurus trecae. The parameter b value of these fish species ranged from 1.6831 to 2.9461, and the correlation coefficient ranged from 0.81 to 0.95. Statistical LWRs for all species were very significant. Information obtained is essential in reviewing and establishing basic management measures for depleted shared pelagic stocks in the Gambian fisheries and the sub-region. In the context of poor data fisheries, such results also encourage the Gambian government and intergovernmental subregional organizations to support data collection in the long term.

In the present study, the DNA barcoding of the nematode parasite infecting Ompok bimaculatus and Nemacheilus anguilla fish species was carried out in Barvi Reservoir, Maharashtra. To ascertain the taxonomic status of these nematode parasites, an 18S gene marker was used. Accurate identification of fish parasites is essential to formulate preventive strategies and to study host–environment relations. The present study did barcoding of the nematode parasites of the fishes caught from the Barvi Reservoir using the nuclear 18S rDNA (SSU) sequence. The nuclear 18S rDNA (SSU) was amplified into two overlapping amplicons and sequenced to identify the species based on the sequence similarity with the NCBI GenBank database. The present study sequences (both fragments) showed 98% similarity with the species of Eustrongylides. The average genetic distance value between the present study sample and species of Eustrongylides was 0.003. In the phylogenetic tree also, the sequence was clustered with the species of Eustrongylides with significant bootstrap values. The present study identified the nematode parasite of the fish caught from the Barvi Reservoir, as species of Eustrongylides. The species-level identification could not be possible due to the insufficient/lack of reference sequences in the database. It indicates the knowledge gap concerning the species-specific molecular markers for nematode parasites of the fish.