Se describe el comportamiento de los parámetros de temperatura, salinidad, transparencia del agua y temperatura ambiente, y de la abundancia y diversidad de la comunidad del peces del sistema Candelaria-Panlau en escalas temporal y espacial. Los trabajos de campo se realizaron de manera mensual en cinco estaciones entre abril de 1993 Y abril de 1994. La comunidad de peces quedó representada por 50 especies con 7 926 organismos y 144.7 kg de peso. Los valores de abundancia y diversidad de la comunidad fueron: 0.09 ind/m2, 1.61 g/m2 18.25 g/ind, H'n = 1.879, J = 0.475 Y D = 5.681. Las especies con dominio ecológico fueron: Cathorops melanopus, Diapterus rhombeus, Anchoa mitchilli, Sphoeroides testudineus, Bairdiella chrysura, B. ronchus, Cynoscion arenarius, y C. nebulosus, que en conjunto representan el 90.9 % en número y el 78.9 % en peso de la captura total. Las matrices de valores de los parámetros ambientales y de abundancia numérica de la comunidad de peces, fueron sometidas a un análisis de factores con el método dé extracción de componentes principales, su representación gráfica confmna la definición de especies dominantes y demuestra que la salinidad, estación cinco y mes de febrero son los componentes que caracterizan al sistema y a la comunidad de peces. The environmental and ecological patterns of tbe fish community in Candelaria-Panlau system (Mexico) are described. Parameters of the water temperature, salinity and transparency, and density, biomass and diversity of the fish cornmunity were analyzed. Between April 1993 and April 1994 five stations were sampled monthly. The fish community had 50 species (7 926 individuals, 144.7 kg of weight). The abundance and diversity values for the fish cornmunity were: 0.09 ind/m2 ; 1.61 g/m2; 18.25 g/ind; H'n = 1.879; J = 0.475 and D = 5.681. The species with ecological dominance were: Cathorops melanopus, Diapterus rhombeus, Anchoa mitchilli, Sphoeroides testudineus, Bairdiella chrysura, B. ronchus, Cynoscion arenarius, and C. nebulosus. The matrixes of the environmental parameters and of fish abundance, were tested with a factor analysis (principal components extraction method); its graphical representation confmns the dominant species and indicates that salinity, station number five and February are tbe components that characterize the system and the fish community.

The biodiversity and abundance of commercially important biotic resources on the west coast of Campeche (Mexico) is recognized. The main extraction activity is seabob shrimp fishing. This paper aims to analyze and discuss changes in the abundance of the fish community in two annual cycles by statistical analysis. Between February 2003 and January 2004 (cycle 1) and between February 2006 and January 2007 (cycle 2), 37 sites were visited monthly. Physical and chemical parameters were registered and nekton samples were collected by a trawl net. In cycle 1, 49,177 individuals (631.62 kg total weight) were caught and the fish community was represented by 94 species. In cycle 2, 26,386 individuals (407.07 kg total weight) and 94 species were caught. At spatial scale, the fish community abundance values were 0.01–0.23 ind m–2, 0.08–3.02 g m–2, and 7.12–45.45 g ind–1 in cycle 1, and 0.007–0.11 ind m–2, 0.13–1.71 g m–2, and 5.61–45.64 g ind–1 in cycle 2. Highest abundance was recorded during the dry season in cycle 1, but during the rainy season in cycle 2. There were no significant differences in temperature and salinity between the two cycles, but an analysis of variance revealed significant differences between seasons. Significant differences were founded when the matrix of number of individuals per species and month of both cycles was analyzed by multidimensional scaling.

Terminos Lagoon is recognized as an ecosystem of great diversity and productivity in the southern Gulf of Mexico. It is also the site of various anthropogenic activities in the lagoon as well as in its surroundings. In addition, in recent years this lagoon has showed variations in temperature and salinity as a result of global warming and/or watershed management. This has generated variations in the structure and function of fish communities, among other taxonomic groups. IIn this work, we analyze the changes in abundance and distribution associated with modifications in the salinity of fish species from two key families (Ariidae y Gerreidae) during the years 1980, 1998, and 2011. Salinity is analyzed in the three periods (ANOVA, Tukey (HSD); the abundance of species, environmental breadth according to salinity (Levins Index), environmental overlap (Pianka Index), and co-occurrence (C-score) are also analyzed. Statistical differences were tested using the null model. The results showed high variability in salinity, with a tendency to increase during the studied period with 24.7, 27.9, and 28.4 UPS for each year, respectively (p < 0.0001). The abundance of both families increased from 1980 to 1998 and decreased in 2011 (82% for Ariidae and 62% for Gerreidae). The C-score ranged from 1.07 in 1980 to 0.78 in 1998 and 2.71 in 2011. The observed averages were significantly lower than the simulated average (P <0.0001). In conclusion, the increase in salinity is probably one of the causes of a variation in the abundance of fish species. According to a possible more limited competition for space, fish abundance and C-score fluctuated inversely, indicating a trend towards a more generalist fish community. Keywords: Environmental breadth, environmental overlapping, co-ocurrence, and salinity gradient.