Biology and assessment of the thread fin bream Nemipterus japonicus in Gulf of Suez, Egypt

Monthly data of length frequency for Nemiptrus japonicus landed between September 2010 to July 2011 from commercial catch at El-Attaka fish landing along the Gulf of Suez were used to estimate the age composition, growth parameters, sex ratio ,condition factor, length at first sexual maturity, mortality exploitation rate, relative yield per recruit, and relative biomass per recruit. The maximum total length and weight were 29cm and 219.92 g, respectively. Females and males were represented by 46% and 54%, respectively, of the particular population of the species. The total length of females ranged from 8.5-25cm, and of males 10-29cm. The lengthweight relationship for combined sexes were estimated as W=0.025*L^2.733. Age determination based on length frequency data showed that the life span extended to five years. The von Bertaianffy growth parameters were estimated as: L_∞ =33.65cm, K=0.450 and t_◦ = -0.123. Females matured at a total length of 12.5 cm, while males matured at a total length of 11.4 cm. The mortality rates were computed as (Z) =1.75 y^-1 , (M)=0.529 y^-1 and (F) =1.221 y^-1 . The exploitation rate was estimated as E cur.0.697. The relative yield per recruit and relative biomass per recruit analysis showed that the stock of Nemiptrus japonicus in the Gulf of Suez was overexploited.