Integrated biomarker approach strongly explaining in vivo sub-lethal acute toxicity of butachlor on Labeo rohita

Alteration of haematological and biochemical biomarkers after sub-lethal chronic malathion (Elathion®) intoxication in freshwater fish, Labeo rohita (Hamilton, 1822)

The present investigation aimed to evaluate the long-term effects of malathion (Elathion®) at two sub-lethal concentrations (0.36 and 1.84 mgL-1) for 45 days after the determination of 96 h-LC50 value (18.35 mgL-1) in a commercially important aquaculture species, Labeo rohita by assaying multiple biomarker approaches. Total erythrocyte count (TEC), and haemoglobulin count (Hb) were found to be decreased while total leucocyte counts (TLC) were increased (p < 0.05) in malathion-intoxicated fish. Malathion exposure significantly reduced (p < 0.05) serum protein levels while significantly increased (p < 0.05) blood glucose levels. RNA activity in muscle was reduced (p < 0.05) while DNA activity increased (p < 0.05) in malathion-intoxicated fish. Acid phosphatase (ACP) activities in the brain; lacate dehydrogenase (LDH) activities in brain and liver were increased (p < 0.05), while alkaline phosphatase (ALP) activities in the brain; succinate dehydrogenase (SDH) activities in the brain, liver and kidney; acetylcholine esterase (AChE) activity in the brain; and ATPase activities in the brain, liver and kidney were reduced (p < 0.05) in comparison to control. Thus, the alteration in studied biomarkers was in a concentation-time dependent manner; however, it was more pronounced at the higher concentration at 45 days of exposure. The alteration in biomarker activity is probably a defensive mechanism/ adaptive response of fish to overcome the stress induced by malathion, which is a novel insight and possible impact on L.rohita. Our findings suggest malathion-induced stress, therefore, the use of malathion needs to be regulated to safeguard aquatic animals including fish and human health.

Multivariate characterization of biochemical and physiological attributes umpires Pangasianodon hypophthalmus for a welfare-based open-water cage culture

The striped catfish, Pangasianodon hypophthalmus, dominates in the Indian inland freshwater cage culture because of its rapid growth and adaptive feeding habits; however, suitable stocking density based on growth without compromising the health of fish is important. Furthermore, fish growth and survival are inversely proportional to stocking density. Many farmers face size differentiation and poor survival at higher stocking densities. To address the aforementioned practical issue, the current study was carried out to study the influence of different stocking densities on the growth performance of P. hypophthalmus in cages. The fingerlings of P. hypophthalmus (10.63 ± 0.27 g) were stocked in triplicate in five different stocking densities (20, 30, 40, 50, and 60 m-3), and the fishes were given commercial feed for 240 days. The outcome demonstrated that the fish stocking densities and their growth attributes were inversely related. Stocking density in the range of 20 to 40 m-3 produced the highest final weight, relative growth rate, and specific growth rate. The feed conversion ratio was significantly lower in 20, 30, and 40 m-3 than the higher densities of 50 and 60 m-3. The level of serum biochemical markers such as serum glutamate oxaloacetate transaminase (SGOT) and serum glutamate pyruvate transaminase (SGPT) and glucose and cortisol levels elevated significantly in higher stocking densities. The muscle quality changed as crude fat and muscle pH decreased at 50 and 60 m-3, leading to a drop in drip loss and frozen leakage rate. The vital water quality parameters were found within a suitable range. According to the outcomes of principal component analysis (PCA), elevated levels of SGOT, SGPT, glucose, and cortisol were detrimental to fish growth. The stocking density of 30 m-3 had the highest benefit-cost ratio (B:C) and return on investment (RI), followed by 20 and 40 m-3. Higher economic return was achieved at lower densities (30-40 m-3). This study suggests that rearing P. hypophthalmus at stocking densities of about 30-40 m-3 could be considered as an optimum for the inland freshwater cage culture which gives the best performance in terms of growth and production in tropical reservoirs of India. The best-suited stocking density is also taken into consideration based on the characterization of multivariate biochemical and physiological attributes.