Size structure of freshwater mussel Unionidae Psoronaias crocodilorum on Wetlands Biosphere Reserve of Centla, Mexico

Population parameters in two populations of mussels, Psoronaias crocodilorum, in the San Pedrito River and the Naranjos River in the Centla Wetlands Biosphere Reserve (CWBR), Mexico, were assessed. Samples were collected in May 2008, and a density and a morphometric study were performed. For each sample, water depth, temperature, salinity, pH, organic matter and sand, silt and clay percentage, were recorded. The San Pedrito river bank had a surface of 1200.12 m2 vs. 562.00 m2 in Los Naranjos. Shell length in San Pedrito was 21.26 – 76.16 mm vs. 22.20 – 83.30 in Los Naranjos; the most frequent length in both sites was 58.71 – 60.11 mm. Shell weight averaged 87.43% of the mussels’ total weight. MV in San Pedrito was 219.41 g/m2 and 81.75 g/m2 in Los Naranjos. Density in San Pedrito was 22.90 org/ m2 and 10.50 org/m2 in Los Naranjos. Texture in sediment was loamy sand with 30.17% organic matter in San Pedrito, and 27.43% in Los Naranjos. Physicochemical parameters and the proportion of sand, silt and clay were similar in both sites. None of the mussel banks had biological, ecological or economic features for a fishery, especially due to their low abundance.