Effect of stocking density on growth performance, plankton abundance, body composition and haematological parameters of Etroplus suratensis (Bloch, 1790)

Abstract

A seed rearing experiment was attempted to evaluate the effects of stocking densities in the biofilm-based system reared with pearlspot, Etroplus suratensis on different aquaculture parameters. Pearlspot advanced fry of size (4.67 ± 0.04 cm/1.71 ± 0.03 g) stocked at four different stocking densities viz 50 fish (T 1 ); 100 fish (T 2 ); 150 fish (T 3 ) and 200 fish (T 4 ) m −3 in the biofilm-based rearing system and at the rate of 150 fish m −3 in the clear water fed (CWF) system tanks. The total ammonia nitrogen and dissolved oxygen levels in biofilm tanks with different stocking density were significantly lower than CWF. Diatom was found as dominant plankton in all biofilm treatment tanks in water as well as on substrate. The growth parameters were found to significantly decrease with increasing stocking density in the biofilm-based rearing system. The significant highest individual growth parameters and significantly lowest fish biomass were found in T 1 . Final fish biomass was found to increase with increasing stocking density up to 150 advanced fry m −3 and then reduced due to decreased survival. Body composition analysis of E. suratensis showed increased protein and decreased lipid levels in all biofilm-based rearing system treatments at different stocking densities compared with clear water fed system. The present investigation findings on plankton abundance, growth, body composition and blood parameters at different stocking densities will provide guidelines for selecting appropriate stocking density for pearlspot advanced fry to fingerling rearing in a low saline biofilm-based system without providing a supplementary diet.

Challenges in the field of toxicity of metals in India including the development of new treatment

“…association of photosynthetic microalgae and heterotrophic bacteria (Catarina and Xavier, 2012). It is also found that incorporation of algal bacterial system helps in improving the water quality by removal of harmful nitrogenous content from culture environment (Han et al, 2019;He et al, 2017;Pacheco-Vega et al, 2018;Yadav et al, 2021). The natural anti-microbial compounds or biomolecules in some microalgal species can serve as immunostimulants and improve the cultured organism's health (Charoonnart et al, 2018).…”

“…Microbial films have been reported to improve the water quality parameters and alleviate harmful effects of the overloaded population (Krishnani et al, 2006a;Krishnani et al, 2009Krishnani et al, , 2013Krishnani and Kathiravan, 2010). Yadav et al (2021) reported a significantly lower value of total ammonia concentration in the biofilm rearing system than sources of clear water fed fish seed rearing system.…”

“…The bioactive microbial products or methane utilizing bacterial meal can replace fish meal in feed for tiger prawn totally, biofloc meal or a single-cell protein obtained from the bacteria Corynebacterium ammoniagenes up to 20 % in white leg shrimp feed and methane utilizing bacterial meal up to 55 % in salmon feed. Apart from the above ex-situ trials, some in-situ research efforts have revealed biofilm-based system showed an increase in protein level and decrease in lipid level compared with the traditional fed aquaculture system (Yadav et al, 2021).…”

“…Scope for modification of existing algal bacterial aquaculture system for sustainability: Conventional biofilm culture is performed by the addition of substrate, soil base at the bottom of the culture unit and fertilizers to supply nitrogen and phosphorus for developing algae (Yadav et al, 2021). Addition of substrate in biofilm culture and biofloc system have shown improved shrimp growth and health by trapping the suspended biofloc particles, better water quality parameters, enhanced biofilm growth, and quality of natural food (Kumar et al, 2019).…”