RESUMO
In terms of hatchery-based seed production, one of the most important aquaculture species in Bangladesh is the stinging catfish (Heteropneustes fossilis). Scientific and evidence-based embryonic and larval development research on this fish species in the context of climate change is limited. This experimental study was conducted via induced breeding of stinging catfish using a conventional hatchery system, rearing the larvae in hapas placed in ponds. A series of microscopic observations using a trinocular digital microscope and an analysis of the relationship between larval growth and climate-driven water quality parameters such as temperature, pH, dissolved oxygen, total dissolved solids, alkalinity, and ammonia were performed. During embryonic development, the first cleavage was observed between 30 and 35 min of post-fertilization. Embryonic development (ranging from the 2-cell to the pre-hatching stage) took 21:00 h. Hatching occurred at 22:30 to 23:00 h after fertilization, with an average larvae length of 2.78 ± 0.04 mm. In the post-hatching stage, four pairs of tiny barbels appeared at 36:00 h, and the larvae started feeding exogenously after 72:00 h. These larvae fully absorbed their yolk sacs on the 6th day and attained an average length of 6.44 ± 0.06 mm. Aerial respiration of the larvae was investigated through naked-eye observation on the 10th day of hatching. The average length of the larvae was 32.00 ± 2.0 mm at the end of the 30-day post-hatching observation period. Bivariate correlation analysis showed significant correlations between key climatic variables and water quality parameters under hapa-based larval-rearing conditions. According to canonical correlation analysis, the first canonical function revealed the highest significant correlation between the two sets of variables (r1 = 0.791). The response variable weight of larvae (6.607) was linked to two explanatory variables: pH (0.321) and dissolved oxygen (0.265). For the second canonical correlation function, a positive correlation (0.431) was observed between the two sets of variables. Larval weight (-18.304) was observed to be linked to climatic variables, including air temperature (-0.316) and surface pressure (0.338). Results of this study reveal the subtle correlation between larval growth and water quality driven by climatic variables.
RESUMO
Bangladesh is among the countries most vulnerable to climate change due to its geographical location. Climate change issues have become major concerns in aquaculture industry, particularly for fish hatchery productivity. Fish production in Bangladesh is mainly steered by the aquaculture sector, which is dependent on private hatchery-based fish seed production to a great extent. This review aimed to present the impacts of climate change on fish hatcheries, particularly during different stages of hatchery production, and the economic loss from the onset of disease and other impairments due to environmental causes. Geographically, most hatcheries in Bangladesh are operated within a narrow range of temperature (22.8-23.1 °C, equivalent to 73-73.5 °F) and rainfall (1750-2000 mm). Thus, slightest fluctuations in these parameters affect seed production in fish hatcheries. The broodstock, produced in natural and captive conditions, is severely affected by flash flooding, water quality deterioration, river siltation, erratic rainfall, and temperature fluctuations. Based on our review, temperature fluctuation is the main factor hampering maturation and breeding performances of broodstock. Temperature has also been reported to affect embryonic development and cause stunted growth of larvae and juvenile. In shrimp and prawn hatcheries, fluctuations in temperature, pH, and salinity are responsible for post-larval disease outbreaks. In some instances, storms and heavy rainfall wash away reared broodfish and fish seed from the hatcheries, causing massive socioeconomic losses. This review presents indisputable negative impacts of climate change on hatchery production. As of now, no cost-effective proven strategies have been developed to minimize the effects of climate change on Bangladesh's fish hatchery production, on which the aquaculture industry is inextricably dependent. For sustainable fish hatchery production, basic research on climate impacts on hatcheries is inevitable, as well as improving capacity of hatchery owners are needed for resilient hatchery operations in Bangladesh and similar environments worldwide.
