الفهرس 
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Abstract
Common silver biddy (Gerres Oyena) is considered one of the most important economic fish species in the Gulf of Suez. Monthly random samples (759) specimens ranging from 10.2 to 20.2 cm total length) of the common silver biddy were collected from the commercial catches of the trawl fishery of the main landing site in the Gulf of Suez (Attacka harbor) during the period from September 2015 to June 2016. During the study period, the average annual total common silver biddy catch was 10.4 ton. The fishing effort described as number of landings expanded through the period from 2005 to 2015 was represented by minimum value of 1118 and maximum value of 2272 with average of 1695 landings. According to the otolith examination of 759 specimens, the maximum life span of G.oyena was four and five years for males and females respectively. The length weight relationship indicated that the growth of weight relative to length was positive allometric growth for males, females and sexes combined. The study estimated sex ratio M/F as 1: 2.1. The length at 50 % maturity for males was estimated as 13.5 cm and for female was estimated as 14.1 cm. the spawning season of G. oyena was restricted to the period from April to September for both sexes. For males the ripe stage started from March to the end of August with the highest percent of ripening stage during July. The running stage started from April to September. For females and the ripening starts from May to September and the running stage started from April to September with highest value during May. The spent stage value recorded from October to January and then the maturing and developing appeared during February to March. from these results it can be noticed that the spawning season extend from April to September, with the peak during May (during spring). Size compositions of G. oyena showed that more than 70.0% of the sample was represented in small lengths from 10.5 to 14.5cm. About 30.6% of the catch was represented in length interval of 12.5 to 13.5 cm. The bulk of the catch is constituted of fishes with lengths of 11.5 to 14.5 cm. Generally, age group II was the dominant age group for G. oyena contributing about 45.9%; 50.9% and 50.4% for males, females and combined sexes, respectively. Generally, age groups V attained the least percentage of the catch. The estimated values of total mortality (Z), natural mortality
(M), fishing mortality (F) and exploitation rate (E) were Z = 1.81/ y-1, M=0.45/y-
1,F=1.41/y-1andE=0.76/yea