EFFECTS OF ENVIRONMENTAL POLLUTANTS ON REPRODUCTIVE PERFORMANCE OF FARMED FISH

Abstract

The present study was carried out at the laboratories of the Animal Production Department, Fish production Branch at the Faculty of Agriculture, Ain Shams University, Shoubra El-Kheima, Cairo, Egypt. The aim of the study was to investigate the detrimental effect of xenoestrogens on Oreochromis niloticus. By conducting survey at five different locations of Lake Manzala. Twenty-five to thirty-five wild mixed ages of O. niloticus were taken from El-Bashteer, El-Gameel, El-Serw, El-Enania, El-Sayala and Temsah at two different seasons December 2011 and August 2012 and a reference lab experiment. The Lab experiment Fish were randomly distributed into three groups plus control group. Each experimental group was represented by four replicates in 16 fiberglass tanks with carrying capacity of 15 fish/tank. The O. niloticus were treated with different contamination dosages of nonylphenol ethoxylate (NPE) 25, 50 and 100 μg/l; the administration of doses continued for 126 days. The anatomical and histological criteria were used to evaluate these detrimental effects in all study parts. Survey study The results obtained from the survey study could by summarized as follows: 1. Sex ratio The sex ratio in the first season for both sexes were as follow; the highest males percentage was in Bashteer 80% and the lowest was in both El-Enania and El-Serw 46. 7%. While for females, the highest percentage was in El-Serw 53% and the lowest in Bashteer 20%. In the second season, the highest male percentage was recorded at El-Temsah 91% and the lowest was in El-Gameel 64.29%. 2. Body weight The highest average body weight for males during first season was 96.92g at El-Serw and the lowest was 66.09g at El-Temsah. While, during the second season the highest was 118.63g at El-Enania and the lowest one was 31.20g at El-Temsah. On the other hand, females highest average body weight during the first season was108.50g at El-Serw and the lowest was 50.92g was recorded at Bashteer. During the second season the highest body weight value was 115.17g at El-Enania and the lowest one was 31.07g at El-Gameel. The statistical analysis of body weight showed that the differences among the different locations were significant (P<0. 05). 3. Body length The total body length in the first season ranged from 15 -17 cm for males and 14 -17 cm for females. While in the second season values were ranged from 14-17cm for males and 14-18cm for females. The statistical analysis of total length showed that the differences among the different locations were significant (P<0. 05). 4. Gonado somatic index (GSI) The highest GSI value El-Gameel area was 1.26 for males and 1.96 for female. While in the second season had the highest value, 1.8 was recorded for males at El-Serw and 2.7 for females at Bashteer. The statistical analysis of GSI showed that the differences among the different locations were no significant (P>0. 05). 5. Hepatosomatic index (HIS) The highest HSI values in all areas at the first season was recorded in El-Serw area 3.08 for males and 3.6 for female. The statistical analysis of HSI showed that the differences among the different locations were significant (P<0. 05). 6. Gonadal staging Male gonadal staging, males showed stage II occurring in offseason and the most activity was taking place prior to and during the spawning season (stage IV). Moreover, testis-ovas (To) were found in samples collected in both seasons and all collection sites with different occurrence percentage and severity. However, females gonad in the first season showed; spent stage (V) 100% of the collected samples. While, in the second season mature stage (III) and ripening oocyte stage (IV) were detected with almost all case. Laboratory study The results obtained from the Lab study could by summarized as follows: 1. Body weight The 100µg/l NP9 groups gave the highest average body weight 752.5g; while the lowest obtained by the 50µg/l 217.5g. The statistical analysis of body weight showed that the differences among the different treatment were significant (P<0. 05). 2. Survival rate The survival rate in the control and most treated groups was around 68.3% except for 50µg/l NP9 group that was 20%. 3. Gonado somatic index (GSI) The highest GSI value 0.95 was recorded for meals treated with 50µg/l group and the lowest 0.50 was recorded for 100µg/l treated group. There were statistical significant difference (P<0.05) between control and treated groups in GSI. 4. Hepatosomatic index (HSI) The highest HSI value was recorded for fish treated with 25µg/l group (3.20) and the lowest one was recorded for 50µg/l treated group (2.52). The difference between control and treated groups in HSI statistically significant (P<0.05). 5. Gonadal staging Histological examination showed that early spermatogenesis stage II was observed in fish treated with the highest concentration 100µgl-1 and late spermatogenesis stage IV in the control group. 6. Testis-ova (TO) The occurrence percentage of TO from sampled individuals ranged from 10- 50% of treated groups individuals and severity was minimal to mild (1-3 testis-ova/section) for the treated groups. Thus, the recommended action could be increasing water circulation through inletpurgation to mitigate pollutants and restocking the lake until it regain its natural balance.On the other hand, the lab experiment showed that, other estrogenic chemicals in the environment have the potential to produce effects similar to those of nonylphenol.