Fisheries & Aquatic Life

Effects of preserving juvenile rainbow trout (Oncorhynchus mykiss) in formalin and alcohol on body length, mass, and condition factor estimates

Martyna Greszkiewicz — 2024-12-30

Body length and weight are key parameters measured to provide information about the growth and condition of larval, juvenile, and adult fishes from both the wild and aquaculture. The goal of this study was to evaluate the effects of preservation in formalin and alcohol on juvenile rainbow trout, Oncorhynchus mykiss (Walbaum) standard body length (SL) and weight changes. Standard length (19.43–32.98mmSL) decreased after 60 days of preservation by an average of 2.98% in 96% alcohol and 2.26% in 10% formalin. In contrast, fish body weight (0.094–0.63 g) decreased in alcohol (31.22%) but increased in formalin (11.65%). These percentage values can be used as correction factors, with the exception of fish body weight in alcohol since the size of individuals affected the magnitude of change. Accordingly, a correction formula accounting for fish weight must be applied (fresh weight (g) = -0.0363 + 1.667 × preserved length). Changes in fish length and body weight in different preservatives resulted in significant differences in the Fulton condition factor, with underestimation in alcohol (fresh F = 1.58; preserved F = 1.20) and overestimation in formalin (fresh F = 1.60; preserved F = 1.92).

Incidences of taillessness in Acanthopagrus arabicus and Oreochromis niloticus collected from the Shatt al-Arab River, Basrah, Iraq

Jassim M. Abed — 2024-12-30

Taillessness (the absence of the caudal fin and some of the caudal peduncle) is described in Acanthopagrus arabicus Iwatsuki and Oreochromis niloticus (L.) specimens collected from the Shatt al-Arab River, Basrah, Iraq. The abnormal specimens completely lacked caudal fins and peduncles. The last remaining caudal vertebra was turned downward in A. arabicus, whereas the remaining parts of the caudal fin skeleton were turned upward in O. niloticus. The abnormalities were assessed by morphological diagnosis. None of the cases was fatal as they occurred in adult individuals. The likely reasons for these abnormalities and the appropriateness of this case study for environmental monitoring are discussed. Additional studies should be conducted from the viewpoint of pollution.

Helminths and helminth communities of Chondrostoma nasus from the Danube River, northwestern Bulgaria

Radoslava G. Zaharieva — 2024-12-30

In the 2019–2021 period, a total of 349 specimens of Chondrostoma nasus (L.) from the border zone of the Danube River (Kudelin, Koshava, and Yasen biotopes), in northwestern Bulgaria were subjected to interdisciplinary research. A total of 11 helminth taxa belonging to four classes (Trematoda, Cestoda, Acanthocephala, Nematoda) were identified. Two helminth species (Pomphorhynchus laevis and Contracaecum sp.) were common to common nase from the three biotopes studied. The helminth communities of the species at the level of the component communities and the infracommunities were analyzed for the first time in Bulgaria. Helminth species pathogenic to fishes and humans were found in the helminth communities of Ch. nasus.

Historical occurrence of Atlantic sturgeon, Acipenser oxyrinchus Mitchill, 1815, in the tributaries of the Vistula River in Poland

Stanisław Cios — 2024-12-30

All known historical accounts of the occurrence of Atlantic sturgeon (Acipenser oxyrinchus Mitchill) in the tributaries of the Vistula River are presented and analyzed. Sturgeon occurred in most large, medium, and small Vistula tributaries and in the upper reaches of the Vistula River in Silesia. The fish either migrated or strayed there rarely and irregularly, usually as single specimens and mainly during high waters. The data available do not provide evidence that sturgeon spawned successfully in any of the tributaries. In particular, the data do not support the commonly held view that Drwęca was the most important spawning river after 1918, which is the basis of the ongoing sturgeon reintroduction program.

Effects of dietary Chlorella ellipsoidea on growth performance, body composition, and hematology of stinging catfish, Heteropneustes fossilis

Asraful Alam — 2024-12-30

Microalgae have emerged as a promising feed supplement in aquaculture diets. Therefore, the aim of this study was to investigate the effect of Chlorella ellipsoidea as a feed supplement on the growth performance, body composition, and hematology of stinging catfish, Heteropneustes fossilis (Bloch). Five experimental diets were formulated to conduct this experiment by supplementing 0, 2.5, 5.0, 7.5, and 10% C. ellipsoidea at the expense of fish meal, and these are referred to as the control, CE 2.5, CE 5, CE 7.5, and CE 10 diets, respectively. A total of 900 fish (mean body weight of 0.50 ± 0.01 g) were divided equally into15 glass aquaria (180 L). Triplicate groups of fish were fed with each experimental diet to satiation twice daily for 10 weeks. At the end of the feeding trial, the weight gain (%) of the fish fed CE 5 and CE 7.5 was significantly (P < 0.05) higher than that of fish fed the control diet. The specific growth rate (SGR) of the fish fed CE 5 was significantly higher (p < 0.05) but comparable to those fed CE 2.5 and CE 7.5. The feed conversion ratio (FCR) of the fish fed CE 5, CE 7.5, and CE 10 was significantly (P < 0.05) lower, and the protein efficiency ratio (PER) of the fish fed CE 7.5 and CE 10 was significantly (P < 0.05) higher compared to all the other diets. In comparison to the control, dietary C. ellipsoidea of 5.0–10.0% significantly (P < 0.05) increased the protein content of stinging catfish, while lowering the lipid and moisture contents. The red blood cells, white blood cells, hemoglobin, hematocrit, and mean corpuscular hemoglobin levels of H. fossilis increased significantly (P < 0.05) when the fish were fed 5.0–10.0% dietary C. ellipsoidea compared with the control. Based on the findings of the study, 5.0–10.0% C. ellipsoidea supplementation was optimal in the stinging catfish diet to improve growth performance, body composition, hematology, and immunological response. However, based on regression analysis, the optimum level of C. ellipsoidea as a feed supplement was calculated to be 4.9–5% in stinging catfish.