Publication Abstract

Effects of gear selectivity and different calculation methods on estimating growth parameters of bluefish, Pomatomus saltatrix (Pisces: Pomatomidae), from southern Brazil

Effects of gear selectivity and different calculation methods on estimating growth parameters of bluefish, Pomatomus saltatrix (Pisces: Pomatomidae), from southern Brazil

F.M.Lucerna and C.M. O'Brien

We examined the effects of gear selectivity and the consequences of a chosen method for estimating growth parameters of bluefi sh, Pomatomus saltatrix, from southern Brazil. Samples were obtained from commercial landings at Rio Grande (1992–97). Age determination for 1159 fi sh indicated that gill-net and purse-seine fisheries caught 1–5 year-old and 1–7 year-old fi sh, respectively. Trawlers caught fi sh from ages 1 to 7. Because of their high degree of selectivity, the gill nets caught the larger individuals of ages 1 and 2, as well as the smaller individuals of ages 3–5. Faster-growing fish captured with gill nets had smaller scales than fi sh of a similar length caught with purse seines. By contrast, the slower-growing fi sh captured with gill nets had larger scale size than fi sh of a similar length caught with purse seines. For gill nets and purse seines, there were differences between the von Bertalanffy growth estimates derived from both mean values of backcalculated length-at-age and individual back-calculated length-atage. We also recorded differences in growth parameters obtained from back-calculated length-at-age derived from measurements to the last annulus only and from measurements of all annuli up to the sampling age. Selectivity-related bias was incorporated in the estimation of growth parameters, yielding unrealistic estimates of L_¥ and k for the gill-net growth curve.

Reference:

F.M.Lucerna and C.M. O'Brien, 2001. Effects of gear selectivity and different calculation methods on estimating growth parameters of bluefish, Pomatomus saltatrix (Pisces: Pomatomidae), from southern Brazil. Fishery Bulletin, 99(3): 432-442.

F.M.Lucerna and C.M. O'Brien*

Fishery Bulletin, 99(3): 432-442