Effect of seasonal variations on performance and parasitic infestation of cultured fish in Fayoum governorate

A field study was carried out in a fish farm to study the effect of seasonal variations during the production period on performance and parasitic infestation of cultured fish. Water samples were obtained to determine the Physio-chemical investigation of water in the examined farm to estimate temperature, dissolved oxygen, PH, ammonia, nitrite, nitrate, salinity, total alkalinity and total hardness. Fish samples were obtained for parasitological examination to detect external parasitic infestation.The results referred that an elevation of water temperature during summer months leading to slight increase of PH of water, while dissolved oxygen values decreased from 6.8±0.15 to 6.0±1.5 throughout the study period. The mean values of ammonia, nitrite and nitrate reach the maximum in July and August months (0.71±0.18, 0.20±0.07 and 3.1±0.07 mg/l respectively). In addition there was a slightly increase of the total alkalinity and total hardness at beginning of the study (37.8±3.0 and 147.0±5.0mg/l respectively) reached the maximum levels in the summer months (44.4±2.8 and 182.8±6.0 mg/l respectively). It can be noticed that the most prevalent ectoparasitic affecting cultured Tilapia are Trichodina,Monogenia and Epistylis. It can be noticed that, the average initial body weight of examined fish was 6.8±2.3 gm and reached 218.0±3.8 gm. at the end of experiment (210 days) with an average of daily weight gain 1.01 ±0.07 gm. From the aforementioned results, it can be concluded that special attention to Physio-chemical parameters of water fish ponds and regular inspection of fish parasitic infestation particularly during summer months obtained a good fish performance as well as high body weight gain and high survival percentage.