Abstract
Common snook Centropomus unidecimalis is an important commercial and fishery species in Southern Mexico, however the high exploitation rates have resulted in a strong reduction of its abundances. Since, the information about its population structure is scarce, the objective of the present research was to determine and compare the age structure in four important fishery sites. For this, age and growth of common snook were determined from specimens collected monthly, from July 2006 to March 2008, from two coastal (Barra Bosque and Barra San Pedro) and two riverine (San Pedro and Tres Brazos) commercial fishery sites in Tabasco, Mexico. Age was determined using sectioned saggitae otoliths and data analyzed by von Bertalanffy and Levenberg-Marquardt among others. Estimated ages ranged from 2 to 17 years. Monthly patterns of marginal increment formation and the percentage of otoliths with opaque rings on the outer edge demonstrated that a single annulus was formed each year. The von Bertalanffy parameters were calculated for males and females using linear adjustment and the non-linear method of Levenberg-Marquardt. The von Bertalanffy growth equations were FLt = 109.21(1-e-0.2(t+0.57)) for Barra Bosque, FLt = 94.56(1-e-027(t+0.485)) for Barra San Pedro, FLt = 97.15(1-e 0.17(t + 1.32)) for San Pedro and FLt = 83.77(1-e-026(t + 0.49)) for Tres Brazos. According to (Hotelling's T2, p < 0.05) test growth was significantly greater for females than for males. Based on the Chen test, von Bertalanffy growth curves were different among the study sites (RSS, p < 0.05). Based on the observed differences in growth parameters among sampling sites (coastal and riverine environments) future research need to be conducted on migration and population genetics, in order to delineate the stock structure of this population and support management programs.
Highlights
(Caballero 2003, Zarza-Meza et al 2006)
Considering that common snook is a diadromous species with a life cycle which is strongly related to riverine migrations, it is important to know its population dynamic along its distribution range and to test for populational differences regarding its life cycle and reproductive migration along rivers
The analysis of covariance (ANCOVA) analyses show that the FL-SW relationship was not statistically different between males and females for all sampling points
Summary
(Caballero 2003, Zarza-Meza et al 2006). in recent years, the high exploitation rates by the commercial and recreational fisheries had resulted in a strong decrease of its abundance in many coastal areas of the Gulf of Mexico (Chacón 1993, Quiroga & Solís 1999, Caballero 2003, Muller & Taylor 2006). Comparative studies about common snook in Florida, USA, showed differences in the growth and reproductive parameters of two populations (Eastern and Western) of Florida This was related to the reproductive isolation between these two populations and differences in exploitation rates (Marshall 1958, Aliaume et al 2000, Taylor et al 2000, Muller & Taylor 2006). In Tabasco state, small-scale fishery fleets exploit common snook within coastal marine and riverine environments by using special gillnets made out of multifilament nylon (PereraGarcía et al 2008) This species represents a significant monetary income and alimentary resource for all rural communities nearby its distribution. Based on the economical importance of this species and its life cycle, the aim of this study was to determine and compare the age structure and growth rates of common snook individuals, collected from small scalefisheries of two coastal and two riverine areas in Tabasco, Mexico
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