The Effectiveness of Coded Wire-Tagging and Release Methods as an Approach for Increasing the Stocking of Grey Mullet (Mugil cephalus) in an Egyptian Enclosed Wadi El-Rayan Lake

Determining appropriate methods to release fish into confined water bodies such as lakes necessitates an awareness of the potential impact on local fish and the ecosystem in general, as well as a cost-benefit analysis. The purpose of this study was to apply various release strategies boosting the survival rate (%) of grey mullet (Mugil cephalus) fingerlings in the lower part of Wadi El-Rayan Lake (WRL) located in Al-Fayoum Governorate, Egypt. This study involved two experiments. The first experiment involved nursing and rearing grey mullet fingerlings in net enclosures (NE-CWT) and an earthen pond for 40 days before releasing them into the WRL.  In the second experiment, three groups were studied before being released into the WRL: the first group underwent a nursing experiment (nursing for 40 days for acclimatization), the second group underwent grow out rearing for 334 days, and the third group (control group, continued) was released directly into the WRL, without extended rearing, acclimatization, or CWT recovery. During the first experiment, the growth performance, feed utilization, and survival rates of M. cephalus fingerlings were recorded. Throughout the second experiment, the fishermen collected monthly samples from the WRL to monitor the growth and survival rates of M. cephalus. The data revealed that fish temporarily held in NE-CWT had significantly higher (P< 0.05) final body weight, total weight gain, specific growth rate, and survival rate. Growth trends were similar for the fish temporarily held in EP-CWT. These findings emphasized the significance of short-term rearing and acclimation prior to release for improving the performance parameters of mullet seed compared to direct release into the lake. The study results can be used to increase the effectiveness of future grey mullet (M. cephalus) stockings in the Egyptian lakes. Transferring the results to fishermen’s associations in Egypt will provide these groups more time to evaluate and improve the stock enhancement technologies.