Fisheries & Aquatic Life

Effect of different stocking densities on growth performance, feed utilization, and survival of Labeo angra (Hamilton) fry in aquaria

- Akhtaruzzaman — 2025-09-30

This study was conducted to assess the effect of stocking density on the growth performance, feed utilization, and survival of Labeo angra (Hamilton) in nine glass aquaria each containing 30 l of water for 45 days. Three different stocking densities of 1, 1.5, and 2 fry l^-1 of water (T₁, T₂ and T₃, respectively) were assessed in three replicates each. L. angra fry of approximately 0.32 ± 0.10 g weight were stocked and fed with a commercial feed four times daily at a rate of 15–30% body weight. Growth performance in terms of final weight (2.53 ± 0.22 g), weight gain (2.20 ± 0.05 g), percentage of weight gain (567.68 ± 15.25%), average daily gain (4.90 ± 0.11% day^-1), and specific growth rate (4.54 ± 0.04% day^-1) showed significantly higher values in T₂ compared to the other treatments. Significantly lower feed conversion ratios and the highest protein efficiency ratio were noted in T₂ (1.5 fry l^-1) diets. Significantly higher survival was observed in T₂ compared to T₁ and T₃. However, the results indicated that T₂ (1.5 fry l^-1) had more positive influence on the enhancement of growth performance, feed utilization, and survival of L. angra fry nursing in aquaria.

The use of biofilters with different types of fillers in recirculation aquatic system (RAS)

Dmytro Sharylo — 2025-09-30

The aim of this study was to evaluate the effectiveness of using highly porous materials as fillers for biofilters in RAS, such as those with a much higher specific surface area than classical polymer floating bioload, and to determine the optimal proportion of biofilter with these fillers to the total volume of fish tanks. During the experiment, additional nitrogen in the form of ammonium chloride was added to the water of the RAS with different filler types. The effectiveness of biofiltration systems with different fillers was evaluated by the oxidation time of NH₃/NH₄⁺ to NO₂^- and the physiological condition of sterlet fry (Acipenser ruthenus L.), which was used as a test organism. It was proven that highly porous fillers oxidized ammonium compounds in RAS water 1-3 hours faster than polymer floating bioloading. The optimal proportions of the volumes of highly porous fillers to the total volume of fish tanks were determined to be 1:100 for foamed glass and 1:50 for porous ceramics. Under the experimental conditions, the survival of the test object corresponded to current technological standards. Observations of the physiological state and behavioral responses of young sterlets did not reveal any adverse effects of nitrogen compounds on fish.

New multiplex PCR assays for estimating genetic diversity in European grayling (Thymallus thymallus) by polymorphism of microsatellite DNA

Dariusz Kaczmarczyk — 2025-09-30

The European grayling (Thymallus thymallus L.) is a vulnerable freshwater fish that plays an important role in the conservation of the biodiversity of European ichthyofauna and is a key species in recreational fishing. Multiplex PCR is a technique used to estimate genetic diversity that saves both time and money. This paper presents three multiplex PCR assays for amplifying 11 microsatellite markers from European grayling DNA. The steps necessary for constructing multiplex assays and verifying genotyping results are described. The compositions of the PCR mixture and the characteristics of the PCR thermal profile recommended for amplification in multiplex mode, and protocols used in genotyping them by using automatic DNA sequences are also described. Consequently, our method enables a near four-fold reduction in time and costs of the PCR stage of studies on genetic variation. Moreover, the next step of analysis (measuring the length of DNA fragments) can be done faster and easier without decreasing the precision or quality of genotyping results. This method was tested by assessing the genetic variation in a grayling stock kept under aquaculture conditions, and it has proved useful in the management of the genetic variation of this species.

New sites of the invasive signal crayfish, Pacifastacus leniusculus (Dana, 1852), from the Lutynia and Prosna rivers in Poland

Paweł Wróblewski — 2025-09-30

This article presents new observations of the invasive signal crayfish, Pacifastacus leniusculus, in Poland. The species was detected for the first time in the Lutynia and Prosna rivers in southwest Poland. In total 59 and 50 individuals were captured. The population examined probably came from illegal releases, while the presence of juvenile specimens may suggest that the population is capable of reproduction. This species could continue to spread and expand its range to include additional aquatic ecosystems. Therefore, it is recommended to monitor the environment regularly and take appropriate remedial actions against this population.

Ecological role and importance of oysters for environmental sustainability: a mini review

Shivish Bhandari — 2025-09-30

Oysters, a bivalve species, play an important role in balancing aquatic ecosystems. However, the role of oysters in environmental sustainability is poorly understood. Here, we answer the question of how oysters contribute to ecological health and environmental sustainability in coastal and marine ecosystems. We reviewed published articles and technical reports. We found that oysters contribute to minimizing eutrophication and provide habitat for many species. Moreover, oysters serve as a good source of food for many invertebrates and vertebrates, including fishes and birds. Additionally, oysters help prevent soil erosion and increase species diversity in aquatic ecosystems. Our research provides basic information about oysters’ contributions to the sustainability of nature; however, more detailed research is needed to better understand how oysters and their environment work together to support and maintain healthy aquatic ecosystems.