In Bangladesh, aquaculture is critically important in terms of providing food and nutrition, sustainable livelihoods, income, and export earnings. Nevertheless, aquaculture in Bangladesh has faced recent concerns due to climate change. Aquaculture is vulnerable to a combination of climatic factors, such as global warming, rainfall variation, flood, drought, temperature fluctuation, and salinity change. Considering the vulnerability of fish production to the impacts of climate change, tilapia farming is one of the possible strategies for adaptation to climate change. The positive culture attributes of tilapia are their tolerance to low water levels and poor water quality with rainfall variation, temperature fluctuation, and salinity change. In fact, tilapia farming is possible in a wide range of water environments, including freshwater, brackish water, and saltwater conditions. We suggest that appropriate tilapia culture strategies with institutional support and collaboration with key stakeholders are needed for adaptation to environmental change.

A global interest in Silver Barb (Barbonymus gonionotus) cultivation has arisen because of a combination of declining wild stock and a steady increase in demand and market value. The purpose of the current investigation was to evaluate the impact of extreme water temperature changes on growth, hemato-biochemical responses, pepsin enzyme activity and gill histomorphology of B. gonionotus. Four distinct temperatures (22, 26, 30 and 34 °C) were applied in the laboratory (22, 26, 30 and 34 °C) in triplicate glass aquariums (150 L each). At 30 and 22 °C, respectively, the highest and the lowest length and weight gain, specific, daily and relative growth rates were noted. At 30 °C the lowest FCR was recorded (1.42 ± 0.04). The values related to hematology and biochemistry were found to be within normal ranges; nevertheless, there was a notable variation in the parameters when the temperature changed. Hematological results revealed that RBC, HB, PLT, HCT and PMV levels were significantly higher in groups 30 °C with respect to others. It was evident that cold and heat shock stress was present due to the decline in hematocrit levels and rise in WBC values. Regarding the biochemical responses, the level of triglycerides, cholesterol, AP, Ca⁺, HDL, and HDL/LDL ratio increased significantly higher at 30 °C. Glucose, total protein, albumin, Na⁺, K⁺, Cl⁻¹, AST, bilirubin, uric acid, and LDL levels were significantly higher at 22 °C compared to other temperatures. There was a higher pepsin activity between 26 and 30 °C while the digestive somatic index (I_DS) was disproportionate. Histological examination demonstrated the well-shaped gill tissues at 26 and 30 °C compared to distinctive pathology in other temperature treatments. As an end note, the results of the experiment indicated that B. gonionotus should be cultured at 26–30 °C to maximize the overall productivity and the health condition of this economically important fish species.

Increased demand for commercial petroleum derivatives, including diesel has increased the possibility of numerous spills and leakages into the aquatic environment worldwide that can directly or indirectly pollute waterbody disrupting the health status of fish species and other aquatic organisms. This study was conducted to understand the effects of commercial diesel oil on freshwater species of rui (Labeo rohita), catla (Catla catla), and mrigal (Cirrhinus mrigala) fingerlings. The fingerlings were exposed to four different concentrations (0; 0.25; 0.50 and 0.75 ppm) of diesel oil, each containing three replications for 96 h. After 96 h lethal concentration (LC₅₀) for rui, 0.35 ppm; catla, 0.30 ppm; and mrigal fingerlings 0.3625 ppm, were calculated through probit analysis. Maximum mortality occurred at the highest concentration of diesel oil, and treated fingerlings showed behavioural and external morphologic alterations. Dissolved oxygen decreased with the increasing of oil concentrations, and water quality was poor among all the treatments. This study demonstrated that commercial diesel oil directly affects the survivability, behaviour, and external morphology of rui, catla, and mrigal fingerlings. It is expected that the present results will be beneficial to make awareness of the fretful effects of commercial diesel oil and other oils uses in the environment.

A study was conducted to determine the breeding season of endangered Nandus nandus by observing fecundity, somatic indexes, and gonadal cycle development year-round. Samples were collected from different fish landing centers of Sadar Upazila of Gazipur district. GSI values of N. nandus ranged from 4.26 ± 0.45 to 10.28 ± 0.39 while the maximum and the minimum GSI values were observed in July and in October, respectively. However, GaSI values showed an inverse relationship between them. The fecundity of this fish varied from 11176 ±593 to 18030 ± 1704 with the mean fecundity value of 13534.87 ± 87.53. Interestingly the highest fecundity was 18030 ± 1704 in July and the lowest fecundity was 11176 ± 593 in March, implying that the fecundity increased with the increment of time. Histological observation of ovary confirmed the presence of undeveloped oocyte (UO) to mature (M) stages of oocytes in fishes from March to November. The mature stages of oocytes including yolk vesicle’s (YV), yolk granule’s (YG), and in the case of the male predominance of spermatozoids were found high in proportion during June to July indicating the peak breeding season of N. nandus. Finally, these results suggest that N. nandus may breed from March with the peak in July and this information may help to provide a guideline for induced breeding and proper management of this fish in a controlled system as well as for conservation from being extinct.

A 60-day experimental trial was conducted to evaluate the effect of different stocking densities, probiotic supplementation, and a biofloc system on the growth and physiological responses of Puntius sophore in laboratory conditions. P. sophore (8.64 ± 1.24 g) was obtained from the Brahmaputra River, Mymensingh, and immediately transferred to a flow-through water system. In experiment 1, fish were subjected to three treatments (20 fish per 400 L as LD, 25 fish per 400 L as MD, and 30 fish per 400 L as HD), and similarly, in experiment 2, three different types of diets were provided (control diet (D1), biofloc (D2), and a probiotic-containing diet (D3)). Three replications were used in the completely randomized experimental design. Growth parameters, viz. TLG, BWG, FCR, FCE, SGR, RGR, and DGR, were significantly influenced by stocking density and probiotics (p < 0.05). The highest growth rate was observed in LD and in D3. The lowest FCR was also observed in LD and in D3, while highest was in HD (30 fish per 400 L) and in D2. Though stocking density does not impact the blood profile, with the exception of WBC, in the case of feeding regime, WBC, RBC, MCV, MCH, and PLT levels differed significantly (p < 0.05); however, all haematological measures were within the normal range in both experiments, and the fish’s physiological conditions were better in LD and feeding with probiotic supplementation (D3). The results obtained from this study suggested that the welfare of P. sophore is adversely affected by high stocking density and increased growth and physiological conditions when cultured with LD and supplemented with probiotics.

A global interest in the cultivation of Kalibaus (Labeo calbasu) has emerged due to decreasing natural stocks and a consistent rise in market value and demand. Given these concerns, understanding the species’ physiological responses to environmental changes is crucial. The present research aimed to assess the effect of varying environmental temperatures on metabolism, haemato-biochemical indices, hormonal concentrations and immune responses in L. calbasu. This study was conducted in triplicate using 100 L glass aquariums at four different temperatures: 22, 26, 30, and 34 °C. The highest weight and length gain were observed at 30 °C, while the lowest occurred at 22 °C. Notably, the best feed conversion ratio (FCR) of 1.51 ± 0.03 was also recorded at 30 °C. Although haematological and biochemical parameters remained within normal ranges, they varied with temperature changes. Indicators of cold and heat stress were evident through lower hematocrit levels and higher white blood cell (WBC) counts. Biochemical indicators such as serum albumin (1.84 ± 0.05 g dL⁻¹), serum globulin (1.64 ± 0.06 gdL⁻¹), HCO₃ (30.93 ± 0.62), Na⁺ (115.60 ± 3.72 mmolL⁻¹), alkaline phosphatase (93.33 ± 9.39 AP, IUL⁻¹), and AST/SGOT (21.00 ± 4.55 UL⁻¹) were significantly higher at 30 °C. Regarding hormonal responses, peak levels of growth hormone (GH), triiodothyronine (T3) (1.44 ± 0.07 ngmL⁻¹), and thyroxine (T4) were recorded at 30 °C. Meanwhile, serum cortisol (1.62 ± 0.06 µgdL⁻¹) and adrenocorticotropic hormone (ACTH) (18.01 ± 3.26 pgmL⁻¹) were highest at 34 °C. Immune responses were strongest between 26 and 30 °C. In conclusion, the results suggest that L. calbasu should ideally be cultured between 26 and 30 °C for optimum growth and health, making it ideal for commercial farming.