Abstract
Growth response of major carps in a pond fertilized with layer manure, at the level of 0.10 g nitrogen/100 g of wet fish weight daily and control (without additives) was examined. Individual weight, fork length and total length gains were better for Cirthina mrigala. However, the trend of weight gains among three fish species was significantly different. Increase in fish yield, under treated pond, remained maxi-mum at water temperature range of 30.5-33.0 ° C, Treated and control ponds re-sponded differently for the planktonic productivity and fortnightly increase in fish yield. However, the correlation coefficients between planktonic productivity and in-crease in fish yield, under both treated and control ponds, were significant. The net fish yields of 4875.42 and 767.29 kg/ha were computed under treated and control ponds, respectively.
INTRODUCTION
Aquaculture in Pakistan can well progress and plays an important role, par-ticularly, in supporting rural economy and in increasing foreign exchange earnings from non-oil commodities. The contribution of aquaculture to the overall fish production is very much less than that from capture fish-eries, however, its contribution in terms of values and socio-economic benefits to the rural and coastal communities is becoming increasingly significant. The average annual fish consumption is becoming increasingly significant. The average annual fish con-sumption in Pakistan is still very low. It is thus obvious that there is an urgent need to increase fish supply, especially for rural people. The production of major carps such as Calla catla, Labco rohita and Cirrhina md-gala, in ponds, could be increased by the ap-
plication of organic and inorganic fertilizers which tend to produce an abundance of zooplankton and phytoplankton, respectively (.laved, 1988). Banerjee et al. (1979) re-ported a fish yield of 670 kg/ha/90 days by using unspecified poultry manure. *laved et al. (1990) used broiler droppings (4.60 ± 0.09% nitrogen) to fertilize major carp ponds and reported a net fish yield of 5050.83 kg/ha/year.
MATERIALS AND METHODS
The methods adopted were the same as given by Javed et al, (1989) with the excep-tion that layer manure (3.84 ± 0.10% nitro-gen) was added to the treated pond at the rate of 0.10 g nitrogen (from 100/3.84 x 0.10 g layer manure) per 100 g of wet fish weight daily for one year. However, the control pond received no additives.
