English abstract
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-Holt model and length-based Bayesian biomass (LBB)
approaches.
The length-weight relationship for P. kaakan was W = 0.03L2.81 with 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) was 58.95 cm, the growth coefficient (K)
was 0.301 year-1 and 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) was 0.379:1, 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 Fmax (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
gear are urgently needed to ensure the future sustainability of this fishery stock under the
growing fishing pressures in the coming years.
