Fisheries of experimental purse seine net using light and population dynamics of Sardinella aurita (Family Clupeidae) east of Alexandria,Egypt.

The present study is focused on investigating the fisheries of pelagic fish caught by purse seiners using light from Alexandria to Rosetta during 2007. Five experimental fishing operations were processed seasonally (spring, summer
and autumn).The fishing operation and sampling were explained. Analysis of species composition (seasonal and total) and size composition were carried out. A comparison between the present study and other previous studies was done.
The average catch of the net per night was maximum during summer (1295 Kg),while minimum one during autumn (479 Kg). The most abundant fish in the catch throughout the year was Sardinella aurita followed by Etrumeus teres,
Sardina pilchardus, Scomber japonicus, Boops boops, Trachurus mediterraneus,and Engraulis encrasicholus respectively.
Growth and dynamic parameters of S. aurita, as it is the main economic pelagic fish species, were investigated. The results obtained show that back – calculated lengths (based on scales readings) for the first, second, third, fourth
and fifth age groups were 12.24; 15.9; 18.98; 21.36 and 22.17 cm respectively.The corresponding weights for the same age groups were 14.31; 28.93; 46.57; 63.98 and 70.71 gm respectively. The length-weight relationship was
represented by the formula: Log W = 0.01701 + 2.68904 Log L. The estimated von Bertalanffy growth
parameters were L∞ = 25.55 cm; K = o.3537 year -1 and to = - 0.81.Growth performance: 2.368. Maximum age: 7.59 year. Total mortality (Z), natural mortality (M) and fishing mortality (F) were: 1.467; 0.86959 and 0.5974
respectively. The yield per recruit indicated that maximum sustainable yield was 18.5 g at fishing mortality (F) 2.8 .Maximum optimum yield was 16.7 g at fishing mortality 1.2 .The current yield was 13.5 g at fishing mortality 0.597.
Meanwhile biomass was 22.6 g at exploitation rate o.313; 13.9 g at exploitation rate 0.51 and 6.6 g at exploitation rate of 0.74 respectively. The exploitation rate (E): 0.31336 proved that this species is under exploitation by purse seine using
light.