(Günther, 1862). Values of b ranged from 2.912 to 3.432. The results revealed that length-weight relations for all species were highly correlated; likewise, length-length relations for all fi shes also showed high correlation. This study presents for the fi rst time, length-weight parameters for two species and length-length relations for six species.Keywords: Actinopterygii, ichthyofauna, estuaries, Michoacán, LWR, regression models, Mexico Length-weight relations (LWR) studies are used to predict the mean weight of fi sh when it is not possible to estimate it in fi eld. They are also used to calculate the standing stock biomass, to analyse the ontogenetic changes, and to study other aspects of fi sh population dynamics like growth rates and age structure (Quist et al. 2012). This type of information is not available for fi sh species inhabiting the coastal zone of the state of Michoacán, Mexico. Thus, the goal of this study was to report data of the length-weight (LWR) and standard length-total length (L-L) relations, for 14 fi sh species caught in estuaries from Michoacán (central Mexican Pacifi c).Fish specimens were collected in four estuaries from the south-eastern coast of Michoacán: Barra de Nexpa (18°05′07′′N, 102°47′18′′W), Teolán (18°4′19′′N, 102°43′51′′W), Mexcalhuacán (18°3′16′′N, 102°39′28′′W), and Barra de Pichi (17°58′28′′N, 102°19′33′′W). The fi shes were sampled bimonthly, from February 2010 through February 2011, using beach seines, cast nets, and trammel nets. Fish specimens, were deposited in the Aquatic Biology Laboratory of the Universidad Michoacana de San Nicolás de Hidalgo (UMSNH) to be identifi ed using specialized keys. Standard (SL) and total (TL) lengths were measured to the nearest 1 mm using a digital calliper and weights were determined to the nearest 0.01 g with an electronic balance.LWR was calculated from linear regression:log W = log a + b log SL Table 1, including number of specimens (n), size range, and b values. Estimations revealed that length-weight for all species were highly correlated, with the coeffi cient of determination (r 2 ) ranging from 0.94 to 0.99 (P < 0.001). The most represented family in our study was Eleotridae (three species). It was followed by Mugilidae and Gobiidae (two species each) while the remaining seven families were represented by a single species only (Table 2).Results were compared with those reported in other studies taken place in the Mexican Pacifi c coast (González-Acosta et al. 2004, Rojas-Herrera et al. 2009, Velázquez-Velázquez et al. 2009). Four of 14 LWRs (Lile nigrofasciata, Mugil curema, Lutjanus novemfasciatus, and Eucinostomus currani) and one of L-L relations (E. currani) were not within the expected range. The differences in the expected ranges when compared with the estimates provided by other studies may be due to the variation in the sample sizes and the size ranges. The high number of individuals with small length was because estuaries are used as nurseries for fi shes such as L. nigrofasciata, Agonostomus monticola, M. c...
