Unraveling the spawning and reproductive patterns of tomato hind grouper, Cephalopholis sonnerati (Valenciennes, 1828) from south Kerala waters.

The objective of this study is to provide information on the reproductive biology of tomato hind grouper, Cephalopholis sonnerati (Valenciennes, 1828) for conservation and management purposes. Fish caught by artisanal fishermen from September 2019 to August 2021 were analysed. A total of 280 females, 31 males, and 4 transitional and 178 sex-undetermined fish were analysed. The female to male sex proportion was 9:1, and the fish reached a maximum total body length of 38.5 and 54.5 cm for females and males, respectively. The following microscopic stages were identified: immature, developing, ripe, running ripe/releasing, and spent in both males and females. Several asynchronous development patterns were observed in the studied gonads, including multiple oocyte stages and early and advanced stages of sexual transition. High gonadosomatic index (GSI) for both males and females was recorded in March, May, and November. Running ripe and releasing stages in females were identified in the months from March to June, which indicates the spawning season. The absolute and relative fecundity of the species ranged from 162,723 ± 207,267 and 239 ± 285, respectively. An exponential relationship was found between fecundity and total body length (TL), fecundity and total body weight (TW), and fecundity and gonad weight (GW).

Trophic significance of microzooplankton to commercially important small pelagic fishes along the southwest coast of India.

Microzooplankton is an important component in the plankton food web transferring microbial food web carbon to the higher trophic levels, including fishes. This study investigates the role and significance of microzooplankton in the diet of three economically important small pelagic fishes along the southwest coast of India: Indian oil sardine (Sardinella longiceps), Indian mackerel (Rastrelliger kanagurta) and Commerson's anchovy (Stolephorous commersoni). The diet content of oil sardine was dominated by diatoms throughout the year with an increase in the presence of microzooplankton and copepods during the Northeast Monsoon. Phytoplankton, microzooplankton and copepods represented the diet of Indian mackerel throughout the year. Commerson's anchovy differed considerably in their diet composition from both Indian oil sardine and Indian mackerel as they chiefly depended on a carnivorous diet feeding on copepods, fish eggs, ostracods, lucifers and microzooplankton. The present study concludes that organic carbon from the microbial food web also, through microzooplankton, provides nutritional support to small pelagic fishes along the southwest coast of India but in varying degrees depending on the fish species as well the seasons.

Chronic stress due to high stocking density in open sea cage farming induces variation in biochemical and immunological functions in Asian seabass (Lates calcarifer, Bloch).

Stocking density is an important factor in cage aquaculture of finfish. Effects of high stocking density (35 fish cubic m(-1)) on a range of biochemical and immunological parameters in Asian seabass reared in open sea floating net cages were compared to fish held in relatively low density (15 fish cubic m(-1)). The results revealed that chronic stress due to high stocking density induced variations in most of the parameters studied as evidenced by increased cortisol and glucose levels and decreased activity of lysozyme, myeloperoxidase and complement. Production of reactive oxygen species, total leucocyte count and total serum protein were also decreased, whereas anti-protease, alkaline phosphatase and acid phosphatase activities were increased in high stocking-density group when compared to low stocking-density group. Effects of chronic stress due to high stocking density were discussed in relation to variations in these parameters.