Mitigating abiotic stresses using natural and modified stilbites synergizing with changes in oxidative stress markers in aquaculture.

In-depth mineralogical understanding and characterization are necessary to explore potential applications of clinoptilolites. In this study, the clinoptilolite collected from quarries and identified as stilbite microscopically and spectroscopically was subjected to physical and chemical treatments for the synthesis of modified stilbites, which were further evaluated for determining their removal efficiencies on ammonical contaminant in a predetermined concentration range from various source of aquaculture water namely fish pond, aquaponics and ornamental under laboratory condition. High-resolution transmission electron microscope results revealed that stilbite was rod-shaped in all forms but physically modified stilbite contains some nano-zeolite particles, synthesized probably due to heat treatment. The natural zeolite (stilbite) and microwave sodium acetate treated stilbite were found to be most effective in ammonia removal, hence both these products were further evaluated for the removal of cadmium and lead under laboratory conditions and for the ammonia removal in fish pond water under wet lab conditions. The results showed that these zeolites at 10-100 mg/L and 100-200 mg/L had a better removal efficiency of ammonical and metallic contaminants, respectively. Fish samples were taken at particular intervals to determine oxidative stress parameters, i.e., superoxide dismutase and catalase enzyme activities were found to be increased in control fish samples without treatment due to abiotic stress caused by higher ammonia concentration. The levels of oxidative stress markers are decreased in the treatments with zeolite-stilbite which brings to light its potential efficiency in alleviating stress in fish. This study revealed the potential of natural and abundantly available native zeolite-stilbite and its chemically modified form in relieving ammonical stress from the aquaculture system. This work has potential applications for the environmental management of aquaculture, ornamental fisheries, and aquaponics.

Maturation profile and fecundity of the exotic Oreochromis niloticus in the River Yamuna, India.

The knowledge on the reproductive biology of fish Oreochromis niloticus (Linnaeus, 1758) in riverine condition is meagre in the Indian sub-continent which is necessary for the development of an appropriate fishery management protocols for the rivers. In this context, the gonadal maturation profile and fecundity of 0. niloticus was studied. Mature, spawning and spent females recorded in almost all the months of the year evidenced multiple and prolonged breeding behaviour. An overall sex ratio (M/F) of 1: 1.08 observed was statistically non-significant from expected 1:1 ratio (chi2=6.994219, p=0.8642) indicating that males and females were statistically equal in number. The absolute fecundity ranged from 1192 to 4760 with mean of 2590 eggs from ovary weighing between 1.91 g to 28.89 g. Monthly changes in gonado-somatic index (GSI) revealed that fish bred throughout the year except in July and August, but at peak between October-November and March-June. Size at first maturity of male was estimated as 229.6 mm with confidence limit of 235.9 and 223.6 mm and for female as 238.1 mm with confidence limit of 244.7 and 231.7 mm, respectively.