|Management of Argyrozona argyrozona (Pisces: Sparidae) in South Africa based on per-recruit models|
Brouwer, S.L.; Griffiths, M.H. (2006). Management of Argyrozona argyrozona (Pisces: Sparidae) in South Africa based on per-recruit models. Afr. J. Mar. Sci. 28(1): 89-98
In: African Journal of Marine Science. NISC: Grahamstown. ISSN 1814-232X , more
|Authors|| || Top |
- Brouwer, S.L.
- Griffiths, M.H.
Carpenter Argyrozona argyrozona is an endemic sparid that constitutes an important component of the South African linefishery between Cape Agulhas and Port Alfred, where it exists as two stocks; one on the central Agulhas Bank and the other on the eastern Agulhas Bank. Spawner biomass-per-recruit (SB/R), fecundityper-recruit (Egg/R) and yield-per-recruit (Y/R) models were used to model both South African carpenter stocks. Owing to the allometric relationship between annual fecundity and individual size, Egg/R ratios were between 40% and 74% of SB/R at equivalent fishing mortality (F). Egg/R ratios account for allometric increases in fecundity with size/age, and are therefore regarded as better estimators of reproductive potential. It is shown that the current length at first capture (Lc) of 250mm TL and F (at M = 0.1) will reduce Egg/R to 6.41% of the pristine value in the eastern Agulhas Bank population and to between 6.06% and 14.15% on the central Agulhas Bank, indicating that both stocks are heavily overfished. An increase in Lc from 250mm to 350mm TL and a 70% reduction in commercial fishing effort is recommended to attain a target reference point of 40% Egg/RF=0. Bag frequencies indicate that a reduction in daily bag limit from 10 fish person-1