Comparative age and growth of common snook Centropomus undecimalis (Pisces: Centropomidae) from coastal and riverine areas in Southern Mexico Martha A. Perera-Garcia1, Manuel Mendoza-Carranza2, Wilfrido Contreras-Sánchez3, Allyse Ferrara4, Maricela Huerta-Ortiz3 & Raúl E. Hernández-Gómez1 1. División Académica Multidisciplinaria de los Ríos, Universidad Juárez Autónoma de Tabasco, Col. Solidaridad S/N, C.P. 86901, Tenosique, Tabasco, México; [email protected] 2. El Colegio de la Frontera Sur (ECOSUR), Carretera Villahermosa/Reforma, Kilómetro 15.5, Ranchería Guineo 2a. Sección, C.P. 86280, Villahermosa, Tabasco, México; [email protected] 3. División Académica de Ciencias Biológicas, Universidad Juárez Autónoma de Tabasco, Apdo. Postal 967. C.P.86101, México. Villahermosa, Tabasco, México; [email protected], [email protected] 4. Nicholls State University, Department of Biological Sciences, 223 Gouaux Hall, Thibodaux, LA 70310, USA; [email protected] Received 13-XII-2011. Corrected 25-VIII-2012. Accepted 24-IX-2012. 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 mar- ginal 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 -0.21(t+0.57) 0.27(t+0.48) equations were FLt=109.21(1-e ) for Barra Bosque, FLt=94.56(1-e- ) for Barra San Pedro, -0.17(t+1.32) -0.26(t+0.49) FLt=97.15(1-e ) for San Pedro and FLt=83.77(1-e ) 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 differ- ences 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. Rev. Biol. Trop. 61 (2): 807-819. Epub 2013 June 01. Key words: Centropomidae, otolith, population structure, growth rate artisanal fishery. Common snook, Centropomus undecima- (Caballero 2003, Zarza-Meza et al. 2006). lis, is a protandric hermaphrodite species with However, in recent years, the high exploitation a diadromous life history (Taylor et al. 2000, rates by the commercial and recreational fis- Tavares & Luque 2003, Muller & Taylor 2006), heries had resulted in a strong decrease of its distributed in the Eastern Atlantic Ocean from abundance in many coastal areas of the Gulf of Northern Florida, USA to Southern Brazil Mexico (Chacón 1993, Quiroga & Solís 1999, (Rivas 1986, Brennan et al. 2006). Common Caballero 2003, Muller & Taylor 2006). snook is abundant in coastal states of Gulf of The increase in fishing mortality changes Mexico (Tamaulipas, Veracruz, and Tabasco) population structure, particularly age structure Rev. Biol. Trop. (Int. J. Trop. Biol. ISSN-0034-7744) Vol. 61 (2): 807-819, June 2013 807 and reproduction efficiency (Cadima 2003). In Tabasco state, small-scale fishery fleets The impacts of increased fishing mortality are exploit common snook within coastal marine usually more acute in tropical regions, where and riverine environments by using special gill- food availability is often lower as well as meta- nets made out of multifilament nylon (Perera- bolic demands greater than in temperate regions García et al. 2008). This species represents a (Brennan et al. 2006, Stevens et al. 2007). Age significant monetary income and alimentary structure is useful to compare population’s resource for all rural communities nearby its dynamics under different exploitation rates or distribution. Based on the economical impor- different environments occupied by species tance of this species and its life cycle, the aim (Sparre & Venema 1997). Periodic assessments of this study was to determine and compare regarding age, growth, and abundance are basic the age structure and growth rates of common to determine the effects due to changes of envi- snook individuals, collected from small scale- ronmental variables and catch rates over the fisheries of two coastal and two riverine areas exploited populations (Pauly et al. 2002). in Tabasco, Mexico. Comparative studies about common snook in Florida, USA, showed differences in the MATERIALS AND METHODS growth and reproductive parameters of two populations (Eastern and Western) of Florida. Study area and sampling survey: Com- This was related to the reproductive isolation mon snook individuals and otoliths were between these two populations and differences obtained from four commercial landing points in exploitation rates (Marshall 1958, Aliaume located in coastal and riverine areas during et al. 2000, Taylor et al. 2000, Muller & Taylor monthly sampling surveys conducted from July 2006). In México, both studies about age and 2006 to March 2008. Fish were obtained from growth of common snook has been limited to small-scale fisheries by using multifilament coastal zones; these studies have been obser- gillnets with a six centimeters (cm) mesh size, 10-100m length and 2m height. ved by Caballero (2003), who identified nine We sampled two coastal areas, Barra age-classes using whole otoliths readings, indi- Bosque located in the Grijalva River mouth cating that it is a slow growing species with a (18°36’52’’ N - 92°41’07’’ W) and Barra San longevity from 21 to 28 years old. Pedro located at the San Pedro and San Pablo Considering that common snook is a dia- River mouth (18°38’59’’ N - 92°41’07’’ W), dromous species with a life cycle which is as well as in two riverine areas, Tres Brazos strongly related to riverine migrations, it is (18°23’50’’ N - 92°38’52’’ W) and San Pedro important to know its population dynamic (17°46’13’’ N - 91°09’17’’ W) located along along its distribution range and to test for popu- the Usumacinta River (Fig. 1). A total of 104 lational differences regarding its life cycle and and 114 individuals from Barra Bosque and reproductive migration along rivers. In Tabas- Barra San Pedro were respectively collected, co, the fishery of common snook is strongly while 36 and 314 individuals were collected related to its life cycle. The highest catches are from Tres Brazos and San Pedro, respectively. in accordance with its reproductive migrations For each specimen, fork length (FL, in cm) and between riverine and coastal marine areas; somatic weight (SW, in g) were obtained, sex during winter, the mature individuals migrate was determined macroscopically by gonads upstream whereas in summer they migrate to observation, and the right sagittae otoliths were coastal areas to spawn (Perera-García et al. extracted by cutting inside the operculum area, 2008, Perera-Garcia et al. 2011). However, and were stored for later processing. this movement as well as age structure of spawning aggregations are poorly understood Laboratory samples processing: A low (McDowall 1999). speed Buehler® IsoMet® 1000 saw equipped 808 Rev. Biol. Trop. (Int. J. Trop. Biol. ISSN-0034-7744) Vol. 61 (2): 807-819, June 2013 Barra San Pedro Barra El Bosque Gulf of Mexico 18º32’24” Centla Tres Brazos Usumacinta River 18º05’17” Balancan Usumacinta River San Pedro and San Pedro San Pablo River Emiliano Zapata 17º38’10” Tenosique 5 0 5 10 km 92º31’43” 92º03’08” 91º34’57” 91º06’36” Fig. 1. Sampling points of common snook, C. undecimalis, Tabasco, México. with diamond wafering blades was used to cut the distance from the otolith core to the edge 0.5 millimeters (mm) transverse sections from along sulcus ridge (otolith radius) and the dis- each right sagittae otolith (Taylor et al. 2000). tance from the core to each opaque band were Otolith sections were polished with sandpa- measured with a micrometer (Fig. 2). per (2000 caliber); afterwards, sections were In order to test for seasonality in the bands mounted on clean slides with Crystal BondTM formation, a cross correlation analysis was #509 thermoplastic cement (Electron Micros- performed between the monthly proportion of copy Supply, Inc.). marginal translucent and opaque bands with the Images of 7.5 megapixels of each otolith monthly average sea surface temperature of the section were obtained under transmitted light sampled period (Perera-Garcia et al. 2011). The using a stereoscopic microscope Stemi DV4 monthly average sea surface temperature along (Carl-Zeiss) fitted with a CannonTM Power Shot the fishing area was estimated from weekly sea G6 digital camera. Then, the age of each indivi- surface temperature images taken from module dual was obtained by two different readers by MODIS on Aqua (Ocean Watch North Pacific direct counting of the age marks (opaque and Demonstration Project, 2012). translucent bands) (Taylor et al. 2000, Campa- The von Bertalanffy (1957) growth model na 2005). Disagreement between readers was was fitted to the observed length-at-age and addressed by a concert read. However, if diffe- weight-at-age. The model was described by -k (t-to) rences in age determination were persisting, the the equations: Lt =L∞ (1-e ) and Wt=W∞ –k (t-to) b otolith was discarded (Beamish & McFarlane (1-exp ) , where: Lt = average fork length 1983, Taylor et al.