Population biology of Red Sea bream diplodus noct, Valenciennes, 1830 (family: Sparidae) from the northern part of the Gulf of Suez

Population biology of Red Sea bream diplodus noct, Valenciennes, 1830
(family: Sparidae) from the northern part of the Gulf of Suez
Manal M. Sabrah, Aly Yousif and Amal M. Amin
National Institute of Oceanography and Fisheries (NIOF)
P.O. Box 182, Suez, Egypt
E. mail: [email protected]
Received 15st November 2011, Accepted 17th December 2011
Abstract
Age, growth, mortality and the reproductive biology for Red Sea breams, Diplodus noct, were analyzed.
Samples were collected from the northern part of the Gulf of Suez (Suez Bay) during the seasonal experimental
fishing survey using the trammel nets from 2003 to 2005. The study revealed that there is insignificant difference
between males and females in length, age and weight (P > 0.05). The age of D. noct was estimated by reading
otoliths and it was found that the fish maximum age was IV years. The estimated length weight relationship was W=
0.0127L3.073. The von Bertalanffy growth parameters were estimated as K = 0.46 yr-1
(SE = 0.065), L∞ = 28.5cm
(SE = 0.18) and t0 = – 0.029 yr-1
. The overall sex ratio males to females were 1: 1.6 in favor of females. Estimated
total, natural and fishing mortality rates were Z= 2.0yr-1
(SE=0.343), M= 0.99 yr-1
and F= 1.01 yr-1
respectively.
Exploitation ratio was estimated as E = 0.51. The study of the gonad maturation and gonado-somatic index revealed
that, D. noct is a winter spawner. Length at first sexual maturity for males and females were 11.55±cm.The study
revealed that D. noct fishery is relatively overexploited and any increase in the fishing effort will expose the fishery
ground to stress.
Key words: Red sea, Gulf of Suez, Diplodus noct, age, growth, mortality, population, reproductive biology