title: The Use of Per Recruit Models for Stock Assessment and Management of Greasy Grouper Epinephelus tauvina in The Arabian Gulf Waters off Qatar.
abstract: Per recruit models were applied to assess greasy grouper, Epinephelus tauvina, stock in the gulf waters off Qatar. Yield per recruit (Y/R) increased rapidly at low values of fishing mortality (F). At present natural mortality (M = 0.17 per year) and age at first capture (Tc = 7.6 years), the Y/R increased with increasing F to reach a maximum value of 1067.8 g per recruit at F = 0.65 per year. Above this level of F, Y/R was constant or slightly decreased. The current level of F is higher than the biological reference points F0.1 (0.15 per year), FSB40% (0.13 per year), FSB50% (0.08 per year) and FSB25% (0.24 per year). Increasing the Tc by one year resulted in a slight increase in the Y/R, while additional increases in Tc led to a decrease in Y/R values. At constant M, the increase in Tc caused an increase in F required to obtain the maximum Y/R until reaching a non-maximum state at the oldest Tc. At the current level of F, increasing the Tc by one year would result in a small increase in biomass per recruit (B/R), while further increases would lead to a decrease in B/R. At higher levels of F, any increase in Tc would cause a gradual increase in B/R, followed by a decline after a certain value of Tc. These results provide evidence of recruitment over-fishing at all optimum fishing levels, F0.1, FSB40%, FSB50% and at the threshold level, FSB25%. Therefore, sustainable management and conservation of greasy grouper in Qatari waters would require a decrease in F to levels less than F0.1 and FSB40%, which can be achieved through a reduction in fishing effort but not through an increase in Tc.
authors.affiliation: Oceanography Department, Faculty of Science, Alexandria University, Alexandria, Egypt.
authors.forename: Mehdat A
authors.initials: MA
authors.lastname: Abdel Barr
authors.affiliation: Oceanography Department, Faculty of Science, Alexandria University, Alexandria, Egypt.
authors.forename: Abdel Fattaqh M
authors.initials: AF
authors.lastname: El-Sayed
authors.affiliation: Oceanography Department, Faculty of Science, Alexandria University, Alexandria, Egypt.
authors.forename: Amany M
authors.initials: AM
authors.lastname: Osman
keywords: Arabian Gulf; Epinephelus tauvina; Per recruit models