Algal Abundances and Growth Performances of Nile Tilapia (Oreochromis Niloticus) and Common Carp (Cyprinus Carpio) as Affected by Different Fertilizer = تأثير الأسمدة المختلفة على وفرة الطحالب وأداء نمو أسماك البلطي النيلي والمبروك العادي

Abstract

The present study was carried out at a private fish farm at Tolombat 7 site Kafr ElSheikh Governorate, Egypt. The study was performed for 140 days during the period from 5 Th July to 27 Th November 2010. The study aimed to investigate the effect of different fertilizer sources (chemical, organic or combined chemical +organic) on plankton abundances , growth performances of Nile tilapia (O.niloticus) and Common carp (Cyprinus carpio)and water quality parameters in earthen ponds compared to feeding fish only. The experimental ponds were stocked with 4000 O. niloticus fingerlings with an average initial weight of 17.18g and 500 C. carpio fingerlings initial weight of 16.50g in ten earthen ponds with dimentions of 21 x 100 m. each i.e. 1/2 fadden . Five treatments with two replicates each were applied as follow: The 1 treatment was fed only on a commercial fish feed (25% protein), the 2nd organic fertilizer (poultry manure 32.5 kg /0.5 feddan /week) and artificial feeding (25% crude protein), the 3rd combined fertilizer treatment included the application of both organic fertilizer( poultry manure 32.5 kg /0.5 feddan /week) and chemical fertilizer (urea 46.5 % N) at 1 kg /0.5 feddan / week , (triple super phosphate 20% P2O5) at 4 kg/ 0.5 feddan / week and artificial feeding (25% crude protein), the 4th, chemical fertilizer (urea at 1kg/0.5 feddan/week , triple super phosphate 4 kg/0.5 feddan/week ) and artificial feeding (25% crude protein) and the 5th, organic fertilizer (poultry manure 32.5 kg /0.5 feddan /week) and chemical fertilizer (urea at 1kg/0.5 feddan/week , triple super phosphate 4 kg/0.5 feddan/week )where the daily allowances of the fish was calculated as 3 % of fish biomass/day 6 days a week. The average total phytoplankton counts (org /ml) were the highest in the feeding and combined fertilizer treatment compared to those feed only as a result of increased algal density and abundances. Total ammonia (NH4) , Nitrate (NO3 –N) and Nitrite (NO2 –N) concentrations in the combined fertilizer and feed treatments were higher with an increase in algal growth, abundance. Within fertilizer treatments, The daily