Population biology and assessment of representatives of the family Carangidae

Abstract

The demography and status of Carangoides bajad and Gnathanodon speciosus in the Southern Arabian Gulf was investigated using a combination of size frequency and biological data. For both species, the absence of suitable structural increments precluded the development of an ageing method using sagittal otoliths, consequently, length-based methods were used to establish growth parameters. The Hoenig and Hanumara version of the von Bertalanffy growth function provided the best empirical fit to size frequency data and growth rates were characterised by defined seasonal oscillations. Parameter values of the model were: k = 0.598 year−1, L∞ = 40.38 cm (LF), to = −0.35 years, C = 1.0, ts = −0.5 (C. bajad) and k = 0.514 year−1, L∞ = 72.33 cm (LF), to = −0.70 years, C = 0.639 and ts = −0.5 (G. speciosus). Peaks in spawning occurred during June and September for C. bajad and from April to May for G. speciosus. The fishing mortality rate of C. bajad was substantially below the safe harvest level (F0.1), conversely, for G. speciosus it was greater than that associated with the maximum sustainable yield (FMSY). High juvenile retention rates and the discrepancy between the mean sizes at first capture and those which would maximise yield per recruit suggests that a review of the existing mesh size regulations for the trap fishery in the Southern Arabian Gulf is required.