رسائل ماجيستير
English
2023
Population dynamics and stock assessment of Javelin grunter (Pomadasys kaakan) (Cuiver, 1830) in the Northern Sea of Oman, Sultanate of Oman
Fatma Al-Harbiyah , Hussein Al Masroori, Sachinandan Dutta
كلية العلوم الزراعية والبحرية-جامعة السلطان قابوس · عمان
The life history of the fish is dependent on factors such as growth rate, reproductive cycle, reproductive strategies and mortality rate. This in turn depend on the complicated assemblage of discriminatory powers forced on a species by its surrounding environments. The present study tried to determine the life history and population status of Pomadasys kaakan in the Sea of Oman to obtain an optimum sustainable yield and provide management recommendations to ensure the sustainable stock of this species. Commonly known as the ‘Nagroor’, the Pomadasys kaakan(Javelin grunter) is one of the most targeted commercial species in the Sea of Oman and the Persian Gulf. The life history and population status of P. kaakan have been determined by collecting biological data such as length, weight, age, gonad weight and maturity stages on a monthly basis in 2016 from the Dibba fish landing center in the Musandam region of the Sultanate of Oman. The fish stock status was determined using the Beverton-Holtmodel and length-based Bayesian biomass (LBB) approaches. The length-weight relationship for P. kaakan was W = 0.03L2.81with a negative allometric growth (t = 0.0318, P 0.05) being observed during the studied period. The mean Fulton’s condition factor (k = 1.45) and the mean relative condition factor (Kn = 1.01) indicate that the health condition of P. kaakan was good in 2016. The von-Bertalanffy Growth Function (VBGF) parameters such as asymptotic length (L) was58.95cm, the growth coefficient (K) was 0.301 year-1and length at age zero (t0) was 0.9, with the maximum age recorded at 23 years. The gonadosomatic index (GSI) suggested that the spawning season of this species is from March to May in the studied region. The mean length at which 50% (L50) of the population reached sexual maturity was 43 cm. The mean length at first capture was 42 cm, which is smaller than the length at first maturity which mean that the stock is at the edge of being overfishing. The sex ratio (males: females) was0.379:1, indicating female-biased behavior during 2016. The mortality rate (Z) was 0.79 year-1 and the natural mortality rate (M) was 0.68 year-1,implying that the current fishing mortality rate (F) was 0.26 year-1, which is lower than recommended reference points F0.1 (0.19 year-1) and F max (0.31 year-1). The B/BMSY ratio estimated using the LBB method was 0.98, which indicates that the P. kaakan population was being slightly overfished in the northern Sea of Oman. Therefore, management policies such as spawning season catch bans and using high-selectivity fishing
7gear are urgently needed to ensure the future sustainability of this fishery stock under the growing fishing pressures in the coming years.