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Effects of gear selectivity and different calculation methods on estimating growth parameters of bluefish, Pomatomus saltatrix (Pisces: Pomatomidae), from southern Brazil
Lucena, F.M.; O'Brien, C.M. (2001). Effects of gear selectivity and different calculation methods on estimating growth parameters of bluefish, Pomatomus saltatrix (Pisces: Pomatomidae), from southern Brazil. Fish. Bull. 99(3): 432-442
In: Fishery Bulletin. US Government Printing Office: Washington, D.C.. ISSN 0090-0656, more
Peer reviewed article  

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Keywords
Author keywords
    Back-calculation; Atlantic coast; United-states; Gulf

Authors  Top 
  • Lucena, F.M.
  • O'Brien, C.M.

Abstract
    We examined the effects of gear selectivity and the consequences of a chosen method for estimating growth parameters of bluefish, Pomatomus saltatrix, from southern Brazil. Samples were obtained from commercial landings at Rio Grande (1992-97). Age determination for 1159 fish indicated that gill-net and purse-seine fisheries caught 1-5 year-old and 1-7 year-old fish, respectively. Trawlers caught fish 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 fish of a similar length caught with purse seines. By contrast, the slower-growing fish captured with gill nets had larger scale size than fish 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-at-age. 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-infinity and k for the gill-net growth curve.

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