Growth performance and survivability of the Asian seabass Lates calcarifer (Bloch, 1790) reared under hyper-saline, hypo-saline and freshwater environments in a closed aquaculture system / Desempenho de crescimento e sobrevivência do robalo asiático Lates calcarifer (Bloch, 1790) criado em ambientes hipersalinos, hipossalinos e de água doce em um sistema de aquicultura fechado

Salinity is one of the most critical environmental parameters regarding fish physiology, modifying food intake and growth performance in many fish species. The present study has investigated the effects of different salinity levels on growth performance, feeding and survival of Asian seabass Lates calcarifer juveniles. Asian seabass juveniles were reared at 0 (T1), 5 (T2), 22 (T3), 36 (T4), and 42 (T5) ppt salinity. Approximately eight hundred thirty fish individuals with an average weight of 1.24±0.52 g were randomly distributed (166 fish/Tank) in 5 concrete tanks (each tank 30×6×4 ft, volume 19,122 L) for forty days. Juveniles were initially fed 42% crude protein-containing diets at a rate of 6% of their body weight per day. The results showed that salinity level had a significant effect on the weight gain (WG), average daily weight gain (ADWG), specific growth rate (SGR), feed conversion ratio (FCR), survival rate (SR), total biomass and health indices (p<0.05). The highest WG (39.11±1.49 g), ADWG (1.00±0.12 g), SGR (8.74±0.03% d-1) and lowest FCR (0.96±0.20) were observed with T3 treatment, which was significantly higher compared to other treatment groups (p<0.05). Among the health indices, the highest hepatosomatic index and viscerosomatic index were found with T3 treatment, significantly higher than the other groups (p<0.05). No significant differences were found among the treatments in terms of survival rate (p>0.05), but the maximum survival rate (98.89±0.0%) was observed in the T3 and T2 treatments. The maximum level of crude proteins (19.99±1.4%) was found in the whole-body biochemical composition of Asian seabass juveniles in the T3 treatment group. The second-order polynomial regression showed that 20 ppt salinity is optimum for the best growth of Asian seabass. Thus, the present study recommends 20 to 36 ppt salinity for the commercial farming of Asian seabass under a closed aquaculture system.

A salinidade é um dos parâmetros ambientais mais críticos em relação à fisiologia dos peixes, modificando a ingestão de alimentos e o desempenho de crescimento em muitas espécies. O presente estudo investigou os efeitos de diferentes níveis de salinidade no desempenho de crescimento, alimentação e sobrevivência de jovens espécies de robalos asiáticos Lates calcarifer, as quais foram criadas sob salinidade 0 (T1), 5 (T2), 22 (T3), 36 (T4) e 42 (T5) ppt. Aproximadamente 830 indivíduos de peixes com peso médio de 1,24 ± 0,52 g foram distribuídos aleatoriamente (166 peixes / tanque) em cinco tanques de concreto (cada tanque tinha 30 × 6 × 4 pés (9,1 x 1,8 x 1,2 metros), com volume de 19,12 litros) por 40 dias. Os peixes foram inicialmente alimentados com uma dieta contendo 42% de proteína bruta a uma taxa de 6% do seu peso corporal por dia. Os resultados mostraram que o nível de salinidade teve um efeito significativo no ganho de peso (GP), ganho de peso médio diário (GPMD), taxa de crescimento específico (TCE), taxa de conversão alimentar (TCA), taxa de sobrevivência (TS), biomassa total e índices de saúde (p < 0,05). O maior GP (39,11 ± 1,49 g), GPMD (1,00 ± 0,12 g), TCE (8,74 ± 0,03% d-1) e o menor TCA (0,96 ± 0,20) foram observados com o tratamento T3, que foi significativamente superior em comparação com os outros tratamentos (p < 0,05). Entre os índices de saúde, os maiores índices hepatossomáticos e viscerossomáticos foram encontrados no tratamento T3, significativamente superior do que os demais grupos (p < 0,05). Não foram encontradas diferenças significativas entre os tratamentos quanto à TS (p > 0,05), mas a TS máxima (98,89 ± 0,0%) foi observada nos tratamentos T3 e T2. O nível máximo de proteína bruta (19,99 ± 1,4%) foi encontrado na composição bioquímica dos corpos dos jovens robalos asiáticos no grupo T3. A regressão polinomial de segunda ordem mostrou que a salinidade de 20 ppt é ótima para o melhor crescimento do robalo asiático. Assim, o presente estudo recomenda salinidade de 20 a 36 ppt para o cultivo comercial de robalo asiático em sistema de aquicultura fechado.

Growth performance and survivability of the Asian seabass Lates calcarifer (Bloch, 1790) reared under hyper-saline, hypo-saline and freshwater environments in a closed aquaculture system

Abstract Salinity is one of the most critical environmental parameters regarding fish physiology, modifying food intake and growth performance in many fish species. The present study has investigated the effects of different salinity levels on growth performance, feeding and survival of Asian seabass Lates calcarifer juveniles. Asian seabass juveniles were reared at 0 (T1), 5 (T2), 22 (T3), 36 (T4), and 42 (T5) ppt salinity. Approximately eight hundred thirty fish individuals with an average weight of 1.24±0.52 g were randomly distributed (166 fish/Tank) in 5 concrete tanks (each tank 30×6×4 ft, volume 19,122 L) for forty days. Juveniles were initially fed 42% crude protein-containing diets at a rate of 6% of their body weight per day. The results showed that salinity level had a significant effect on the weight gain (WG), average daily weight gain (ADWG), specific growth rate (SGR), feed conversion ratio (FCR), survival rate (SR), total biomass and health indices (p 0.05). The highest WG (39.11±1.49 g), ADWG (1.00±0.12 g), SGR (8.74±0.03% d-1) and lowest FCR (0.96±0.20) were observed with T3 treatment, which was significantly higher compared to other treatment groups (p 0.05). Among the health indices, the highest hepatosomatic index and viscerosomatic index were found with T3 treatment, significantly higher than the other groups (p 0.05). No significant differences were found among the treatments in terms of survival rate (p>0.05), but the maximum survival rate (98.89±0.0%) was observed in the T3 and T2 treatments. The maximum level of crude proteins (19.99±1.4%) was found in the whole-body biochemical composition of Asian seabass juveniles in the T3 treatment group. The second-order polynomial regression showed that 20 ppt salinity is optimum for the best growth of Asian seabass. Thus, the present study recommends 20 to 36 ppt salinity for the commercial farming of Asian seabass under a closed aquaculture system.

Resumo A salinidade é um dos parâmetros ambientais mais críticos em relação à fisiologia dos peixes, modificando a ingestão de alimentos e o desempenho de crescimento em muitas espécies. O presente estudo investigou os efeitos de diferentes níveis de salinidade no desempenho de crescimento, alimentação e sobrevivência de jovens espécies de robalos asiáticos Lates calcarifer, as quais foram criadas sob salinidade 0 (T1), 5 (T2), 22 (T3), 36 (T4) e 42 (T5) ppt. Aproximadamente 830 indivíduos de peixes com peso médio de 1,24 ± 0,52 g foram distribuídos aleatoriamente (166 peixes / tanque) em cinco tanques de concreto (cada tanque tinha 30 × 6 × 4 pés (9,1 x 1,8 x 1,2 metros), com volume de 19,12 litros) por 40 dias. Os peixes foram inicialmente alimentados com uma dieta contendo 42% de proteína bruta a uma taxa de 6% do seu peso corporal por dia. Os resultados mostraram que o nível de salinidade teve um efeito significativo no ganho de peso (GP), ganho de peso médio diário (GPMD), taxa de crescimento específico (TCE), taxa de conversão alimentar (TCA), taxa de sobrevivência (TS), biomassa total e índices de saúde (p 0,05). O maior GP (39,11 ± 1,49 g), GPMD (1,00 ± 0,12 g), TCE (8,74 ± 0,03% d-1) e o menor TCA (0,96 ± 0,20) foram observados com o tratamento T3, que foi significativamente superior em comparação com os outros tratamentos (p 0,05). Entre os índices de saúde, os maiores índices hepatossomáticos e viscerossomáticos foram encontrados no tratamento T3, significativamente superior do que os demais grupos (p 0,05). Não foram encontradas diferenças significativas entre os tratamentos quanto à TS (p > 0,05), mas a TS máxima (98,89 ± 0,0%) foi observada nos tratamentos T3 e T2. O nível máximo de proteína bruta (19,99 ± 1,4%) foi encontrado na composição bioquímica dos corpos dos jovens robalos asiáticos no grupo T3. A regressão polinomial de segunda ordem mostrou que a salinidade de 20 ppt é ótima para o melhor crescimento do robalo asiático. Assim, o presente estudo recomenda salinidade de 20 a 36 ppt para o cultivo comercial de robalo asiático em sistema de aquicultura fechado.

Effects of microplastics in freshwater fishes health and the implications for human health.

The presence of microplastics in aquatic environments has raised concerns about their abundance and potential hazards to aquatic organisms. This review provides insight into the problem that may be of alarm for freshwater fish. Plastic pollution is not confined to marine ecosystems; freshwater also comprises plastic bits, as the most of plastic fragments enter oceans via rivers. Microplastics (MPs) can be consumed by fish and accumulated due to their size and poor biodegradability. Furthermore, it has the potential to enter the food chain and cause health problems. Evidence of MPs s ingestion has been reported in >150 fish species from both freshwater and marine systems. However, microplastic quantification and toxicity in freshwater ecosystems have been underestimated, ignored, and not reported as much as compared to the marine ecosystem. However, their abundance, influence, and toxicity in freshwater biota are not less than in marine ecosystems. The interaction of MPs with freshwater fish, as well as the risk of human consumption, remains a mystery. Nevertheless, our knowledge of the impacts of MPs on freshwater fish is still very limited. This study detailed the status of the toxicity of MPs in freshwater fish. This review will add to our understanding of the ecotoxicology of microplastics on freshwater fish and give subsequent research directions.

Occurrence of new Philometra sp. in mangrove red snapper Lutjanus argentimaculatus from the Karachi coast, Pakistan.

A recent examination of Philometra nematodes from mangrove red snapper Lutjanus argentimaculatus (Forsskal, 1775) from the Karachi coast, Kemari was done in the years 2021-2022. The present study reported three new species of genus Philometra (Costa, 1845) (Nematoda: Philometridae) Philometra kolachii, Philometra lutjani and Philometra kemarii. A total of 140 fish samples were examined, and 76 were infected. The intensity of infected fish was 54.28%. In Pakistan, literature on Philometrid nematodes is limited, therefore, this research would be helpful for the documentation and enhancement of nematods in Pakistan.

Growth performance and survivability of the Asian seabass Lates calcarifer (Bloch, 1790) reared under hyper-saline, hypo-saline and freshwater environments in a closed aquaculture system.

Salinity is one of the most critical environmental parameters regarding fish physiology, modifying food intake and growth performance in many fish species. The present study has investigated the effects of different salinity levels on growth performance, feeding and survival of Asian seabass Lates calcarifer juveniles. Asian seabass juveniles were reared at 0 (T1), 5 (T2), 22 (T3), 36 (T4), and 42 (T5) ppt salinity. Approximately eight hundred thirty fish individuals with an average weight of 1.24±0.52 g were randomly distributed (166 fish/Tank) in 5 concrete tanks (each tank 30×6×4 ft, volume 19,122 L) for forty days. Juveniles were initially fed 42% crude protein-containing diets at a rate of 6% of their body weight per day. The results showed that salinity level had a significant effect on the weight gain (WG), average daily weight gain (ADWG), specific growth rate (SGR), feed conversion ratio (FCR), survival rate (SR), total biomass and health indices (p<0.05). The highest WG (39.11±1.49 g), ADWG (1.00±0.12 g), SGR (8.74±0.03% d-1) and lowest FCR (0.96±0.20) were observed with T3 treatment, which was significantly higher compared to other treatment groups (p<0.05). Among the health indices, the highest hepatosomatic index and viscerosomatic index were found with T3 treatment, significantly higher than the other groups (p<0.05). No significant differences were found among the treatments in terms of survival rate (p>0.05), but the maximum survival rate (98.89±0.0%) was observed in the T3 and T2 treatments. The maximum level of crude proteins (19.99±1.4%) was found in the whole-body biochemical composition of Asian seabass juveniles in the T3 treatment group. The second-order polynomial regression showed that 20 ppt salinity is optimum for the best growth of Asian seabass. Thus, the present study recommends 20 to 36 ppt salinity for the commercial farming of Asian seabass under a closed aquaculture system.

Composition of macrobenthos in the Bakkhali channel system, Cox's Bazar with notes on soil parameter.

Macrobenthos in coastal environment that play a significant role in the food web. It could also use as a good indicator of aquatic ecosystem health. The abundance and composition of macrobenthos in Bakkhali channel system, Cox's Bazar were conducted in relation to the soil parameters. Samples were collected using Ekman Berge bottom grab from five different stations of Bakkhali channel. Macrobenthos were comprised of five major groups namely Polychaeta (9.96-30.31%), Oligochaeta (3.68-59.707%), Crustacea (0.02-58.40%), Bivalvia (1.40-82.09%) and Gastropoda (0.08-4.25%). Total number of macrobenthos was higher at station I (9000 individuals m(-2)) and station II (8517 individuals m(-2)) compared to other stations. Shannon diversity index among the stations ranged from 0.65-1.04. Soil pH and soil moisture ranged from 6.1-6.4 and 23.44-31.29%, respectively. The highest organic carbon concentration was observed at station I (2.11%) and lowest at station III (1.40%). Maximum fraction of sand by weight was found at stations II (81.88%) and III (87.88) while the highest fraction of clay (21.52%) and silt (8.0%) were recorded in station I. It was observed that benthic bivalves were positively correlated (r = 0.891, p > 0.05) with silt fraction of the sediments.