Document Type : Research article
Authors
1
Limnology department, Central Laboratory for Aquaculture Research, Agricultural Research Center, Egypt
2
Fish physiology and hatchery department, Central laboratory for aquaculture research - Agriculture research center, Egypt
3
Aquaculture department, Central Laboratory for Aquaculture Research, Agricultural Research Center, Egypt
4
Liminology Department, Central laboratory for aquaculture Rsearch, Agricultural Research Center, Egypt
Abstract
Tilapia hatcheries if not well managed, it can cause environmental damage. The present study was designed to quantify the impacts generated by Nile tilapia hatcheries, through applying environmental indicators, which is necessary for tilapia hatcheries sustainable development. Three culture trials, each of 15 days, have been carried out to determine environmental indicators: the nitrogen and phosphorus flux and nutrient mass balance based on inputs from feed and losses in fish harvest, nutrients load in the effluent water, and fish bio-solid wastes (sludge). In each, three cement ponds were assigned to determine the nutrients input and loss for 15 days intervals, fry production cycle. The results showed that every 1 Kg feed of 35% protein produce 420 g sludge, of which 262 gm fish excretion. Uneaten feed was found to represent 15.8-20% of the introduced feed and produce 37.6 - 43.2 % of sludge. Fish retained at least 25.8 ± 3.91 % and 2.74 ± 0.37 % of the input feed nitrogen and phosphorus, respectively. While the sludge contained 11.3 ± 0.78 % and 32.62 ± 14.46 of the feed nitrogen and phosphorus, respectively. Effluent water contained 43.64 ± 6.45 % and 50.22 ± 16.63 % of feed nitrogen and phosphorus, respectively, distributed in three main fractions: particulate form; dissolved organic and dissolved inorganic forms. The feed nitrogen recovery in the present study was 80. 57%, while the phosphorus recovery reached 85.58% of the feed phosphorus content. Fry production is discussed in response to the feed protein content and feeding rate.
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