Studies on the probable sources of fungal infection and the control measures in a fish seed farm

The causes of mortality of fry of cultivable fishes in a fish seed farm were investigated. The mortality was due to fungal infection and the pathogen was Saprolegnia sp. The sources of infection were unhygienic breeding hapas, spawnery hapas in the cemented ponds, hatching jars and excess feeding. Application of one kg slaked lime followed by 75g of CuSo sub(4)(l-0.5 p.p.m.) and 150g of KMno sub(4)(2-1 p.p.m.) per each nursery (158m³ water) controlled the pathogen.

Observations on the fish and prawn seed resources of the Gulf of Kutch and their utilization in aquaculture

The characteristics of the fish and prawn seed resources of the Gulf of Kutch are described. Results of experiments conducted in a primary low saline reservoir of a solar salt works to study their utility for aquaculture are reported. The prospective role of aquaculture in augmenting fish production along the coast is also discussed.

Effects of control of C/N ratio by low-cost carbohydrate addition on water quality and pond ecology in freshwater prawn Macrobrachium rosenbergii post-larvae nursing system

An experiment was conducted to evaluate the effects of control of carbon/nitrogen ratio (C/N ratio) by addition of low cost carbohydrate to the water column on water quality and pond ecology in freshwater prawn Macrobrachium rosenbergii post-larvae nursing system. In this experiment, two level of dietary protein 20% and 35% without carbohydrate addition (‘P20' and ‘P35') and with carbohydrate addition (‘P20+CH' and ‘P35+CH') were compared in small ponds of 40 m² area stocked with 20 post-larvae (0.021 ± 0.001g) per m² . Maize flour was used as low cost carbohydrate and applied to the water column followed by the first feeding during the day. The addition of carbohydrate significantly reduced (p< 0.05) ammonia-nitrogen (NH sub(3)-N) and nitrite-nitrogen (NO sub(2) - N) of water in P20 + CH and P35 + CH treatments. It significantly increased (p< 0.05) the total heterotrophic bacteria (THB) population both in water and sediment. Fifty nine genera of plankton were identified belonging to the Bacillariophyceae (11), Chlorophyceae (21), Cyanophyceae (7), Dinophyceae (1), Rotifera (7) and Crustacea (9) without any significant difference (p>0.05) of total phytoplankton and zooplankton among the treatments. Survival rate of prawn was significantly lowest (p<0.05) in P20 and no significant difference (p>0.05) was observed between P20+CH and P35 treatments. Control of C/N ratio by the addition of low-cost carbohydrate to the pond water column benefited the freshwater prawn nursing practices in three ways (1) increased heterotrophic bacterial growth supplying bacterial protein augment the prawn post-larvae growth performances, (2) reduced demand for supplemental feed protein and subsequent reduction in feed cost and (3) reduced toxic NH sub(3)-N and NO sub(2)-N levels in pond nursing system.

Environmental impact of wild shrimp seed collection with non-selective gears on coastal aquatic biodiversity

Collection of wild tiger shrimp (Penaeus monodon) seed with non-selective gears and its impact upon the coastal aquatic biodiversity has been investigated. Loss of undesired species as by-catch was estimated to be 1,075 individuals for collection of every desired shrimp seed which amounted to be 132 billion in a study area stretching 3 km long coastline of the Sagar Island under the Sunderban Biosphere, West Bengal, India. Non-penaeid shrimp seed and crab larvae accounted to be maximally destroyed as their overall contribution towards the by-catch were 56.5% and 29.44%, respectively. Though, rate of bycatch loss was found to be inversely correlated with the rate of shrimp seed collected per gear (r=-0.82, p<0.05) during the peak season (May-September), the overall relationship between them exhibited a linear relationship (r=0.73, p<0.05). By-catch loss for every shrimp seed collection tended to increase up to a daily collection of 2,500 numbers of shrimp seeds per gear followed by a decline. Coastal aquatic community was maximally damaged when the heterogeneity and stability as reflected by different diversity indices were higher.

Basic steps in the production of the African catfish seed

A typical production cycle for African catfish farming begins with a selection of fingerlings or juvenile fish of good quality for brood stock development. Fish are selected from a family or grow out stock basing on records of the origin,age, strain and performance history of the parents or from the wild in this brochure, we explain the basic steps and requirements a farmer needs in order to achieve good results in the hatchery.