Fisheries & Aquatic Life

Oxolinic acid therapy: An effective way to reduce Aeromonas veronii infection in Oreochromis niloticus and improve biochemical and hematological parameters and histopathological lesions

Priyanka Sinha — 2025-03-31

Bacterial diseases such as motile Aeromonas septicemia are major constraints on aquaculture. This study evaluated the efficacy of oral oxolinic acid (OA) therapy at 12 mg kg biomass^-1 day^-1 for seven days to treat Aeromonas veronii-Av-F (AV) infection in Oreochromis niloticus. The lethal dose of AV for 50% mortality was determined to be 1.81 × 10⁸ cells fish^-1. Following intramuscular AV infection at 2.47 × 10⁸ cells fish^-1, OA treatment significantly reduced fish mortality and accelerated wound healing. AV infection caused notable changes in biochemical, and hematological parameters, erythrocyte morphology, and histopathological damage to liver and kidney tissues. However, OA therapy facilitated normalizing these parameters more rapidly than in untreated fish, including erythrocyte morphology and histopathological alterations. The study highlights the effectiveness of OA in treating AV infection in O. niloticus. However, available evidence cautions against its overuse and violations of regulations because of its critical importance in human medicine.

Large water flea (Daphnia magna Straus) and mealworm (Tenebrio molitor L.) as potential food sources for rearing common carp (Cyprinus carpio L.) juveniles indoors

Szabolcs Márk Turuczki — 2025-03-31

When rearing common carp fry using intensive technology, expensive rearing feeds can be replaced, or partially replaced, with economically produced live food organisms, which is a solution that is close to a natural one. Natural feeding conditions for common carp (Cyprinus carpio L.) juveniles were modeled in indoor studies 49 d in length in two consecutive years in Szeged, Hungary. In 2021, feeding Szeged mirror carp advanced fry with a nutritionally complete formulated feed was compared to feeding them large water fleas (Daphnia magna) and yellow mealworms (Tenebrio molitor) in rations that were adjusted for fish growth. In 2022, Szeged mirror carp and scaled landrace advanced fry fed water fleas and mealworms were compared with the same fish genotypes fed water fleas and complete feed in rations that were adjusted for fish growth. Feeding natural food resulted in significantly larger fish and better values for average daily gain, specific growth rate, feed conversion ratio, and final condition factor in both experiments, confirming that feeding live arthropods results in faster-growing carp fry with better feed utilization efficiency. The carp genotypes had different growth dynamics, with Szeged mirror carp exhibiting faster development and more efficient feed utilization compared to scaled landrace.

Role of β-glucans in reducing oxidative stress and improving muscle tissue health in European whitefish (Coregonus lavaretus L.)

Halina Tkaczenko — 2025-03-31

β-glucans are currently a notable topic in research on enhancing immunity in fishes and their significant role in improving fish health and productivity in aquaculture. Phagocytic activity (PA), phagocytic index (PI), analyses of oxidative stress biomarkers (2-thiobarbituric acid reactive substances [TBARS] as biomarkers of lipid peroxidation, aldehyde and ketone derivatives of oxidatively modified proteins [OMP]), total antioxidant status (TAS), and lysosomal enzyme activity (alanyl aminopeptidase [AAP], leucyl aminopeptidase [LAP], acid phosphatase [AcP], and β-N-acetylglucosaminidase [NAG]) were used to assess the effects of dietary β-glucans on the skeletal muscle and heart tissues of European whitefish (Coregonus lavaretus L.). Our study showed that dietary β-glucan supplementation improved the immune system of European whitefish. Fifteen, 30, and 45 days after supplementing diets with β-glucans, the fish showed increased blood PA and PI, indicating improved immune response. β-Glucans also reduced lipid peroxidation and oxidatively modified protein levels and effectively managed the overall antioxidant status. We observed an increase in β-N-acetylglucosaminidase (NAG) activity in the skeletal muscle tissue on days 15 and 30 after β-glucan dietary supplementation and in the cardiac tissue on days 15 and 45 after â-glucan dietary supplementation. This highlights the role of NAG in the metabolic changes in muscle caused by the action of β-glucans. Furthermore, NAG activity was significantly associated with the tissue type and the duration of β-glucan dietary supplementation, as shown by regression analysis. MANOVA analysis confirmed that the long-term effect of β-glucans was more pronounced. β-glucan supplementation is an effective strategy for improving immune function and managing oxidative stress in the skeletal and cardiac muscles of European whitefish.

Exposure to cobalt chloride alters hemato-biochemical indices and erythrocyte morphology in stinging catfish, Heteropneustes fossilis

Fouzia Sultana Bristy — 2025-03-31

Higher amounts of cobalt chloride (CoCl₂) released by industries are regarded as environmental pollutants. The goal of the current investigation was to assess the acute toxicity of CoCl₂ from its effects on erythrocyte morphology and hemato-biochemical indicators in stinging catfish, Heteropneustes fossilis. The fish were subjected to CoCl₂ at five different concentrations of 0, 50, 100, 200, and 300 mg L^-l,which were referred to as control, CC50, CC100, CC200, and CC300, respectively. Red blood cell (RBC), hemoglobin (Hb), hematocrit (Hct), platelet counts, white blood cell (WBC), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), lymphocytes, granulocytes, serum protein, and blood glucose level were among the hemato-biochemical parameters of stinging catfish that were measured following a 96 h exposure period. Additionally, erythrocytic nuclear abnormalities (ENA) and erythrocytic cellular abnormalities (ECA) were evaluated in the experimental fish. As the quantity of CoCl₂ increased, there were notable reductions in RBC, Hb, Hct, WBC, platelet counts, MCH, MCV, MCHC, lymphocytes, granulocytes, serum protein, and blood glucose levels compared to the control. When the CoCl₂ concentration increased, the frequencies of ECA and ENA also increased significantly (P < 0.05). This work demonstrated the significant toxicity of high CoCl₂ concentrations caused alterations in hemato-biochemical indices and deformities in the erythrocytes of stinging catfish. Thus, it is imperative to take all necessary corrective action to guarantee that the amount of CoCl₂ in the aquatic environment stays below permissible limits.

Impact of varying sodium bicarbonate concentrations on carp skin structure and carcass pH

Wiktoria Cieśla — 2025-03-31

This preliminary study investigated the effects of washing common carp (Cyprinus carpio) carcasses with different concentrations of sodium bicarbonate solution (0%, 2%, 5%, and 7%) on skin morphology and carcass pH levels, which could potentially affect shelf life for consumers. Skin biopsies were analyzed histologically using AB/PAS staining, and pH was measured during a seven-day storage period under refrigerated conditions. Results showed that increasing sodium bicarbonate concentrations led to progressive skin degeneration, with the 5% and 7% groups showing the most superficial loss of the epithelial layer. However, no statistically significant differences were observed among the groups. Washing fish carcasses with sodium bicarbonate solution is a promising way to reduce the amount of mucus on the surface and in the fish skin, which could potentially extend the storage life of carp meat. However, further microbiological studies are needed to confirm these preliminary findings and to investigate the optimal concentration and duration of washing with sodium bicarbonate for different fish species, as well as its impact on the product’s sensory qualities and nutritional value.

The first occurrence of halophyte Oryza coarctata in the mid-southern coast of Bangladesh

Md. Rahamat Ullah — 2025-03-31

Salt marshes and other coastal habitats are essential for preserving ecological balance because they provide a habitat for a variety of species, prevent erosion, and mitigate climate change. The salt-tolerant wild species of rice Oryza coarctata is highly valuable because it may be used to develop crops that can withstand salt. It is a species that is well suited to coastal areas. This study documents the first recorded occurrence of O. coarctata along the mid-southern coast of Bangladesh, specifically in the intertidal zone of the Andharmanik River, Patuakhali, Bangladesh. The distribution and features of the species were evaluated by morphological studies and field surveys. The results show considerable variability of O. coarctata in shoot density (300 to 830 shoots m^-2), plant height (5 to 152 cm), leaf length (2.7 to 29 cm), and biomass (48 to 71 g dry weight m^-2), indicating the species’ phenotypic plasticity in response to environmental conditions. This finding highlights the potential expansion of O. coarctata’s known distribution area.