Basket trap selectivity for tilapia fish at Lake Manzalah, Egypt

Basket trap selectivity for tilapia fish at Lake Manzalah, Egypt
El-Azab El-Azab Badr El-Bokhty
National Institute of Oceanography and Fisheries, Alexandria, Egypt
Received 14th May 2009, Accepted 23rd June 2009
Abstract
To obtain a high and sustainable yield in the fisheries, the mesh size should be controlled to improve the selective
properties of the fishing gear. The present investigation is aimed to evaluate mesh selection and selectivity of the nylon
or filament basket traps for catching Oreochromis niloticus dominating Lake Manzalah by using a new method for its
evaluation. The method of Pope et al., (1975) was used for the first time in Egypt in this concern and compared with that
of Holt (1957). It was found that the Pope et al.,’s model reflects the usual logistic curve while Holt’s method reflects a
similar reversed normal ogive indicating that the first method could be used to evaluate the selective properties of basket
traps. It is recommended also to carry out more experimental studies to ensure the model and to correct the probability of
retention in relation with the mesh size.

Keywords: Tilapia, Selectivity, Basket Trap, Lake Manzala, Egypt.