Juaristi Videgaray Diego, Barjau González Emelio, Vadillo Romero Eleonora
The San Ignacio Lagoon is one of the largest in the northwest area of Baja California Sur; it is characterized by high levels of commercial fish catch; however the number of investigations related to taxonomic diversity is low. The variation in taxonomic diversity was determined for the assemblage of fish associated with soft bottoms, at 11 locations in a period from spring of 1998 to winter of 1999. Variation in diversity of the soft bottom fish were evaluated considering the taxonomic distance between species, using the indices of alpha, average alpha, beta and gamma diversity, also the indices of taxonomic distinctness (Δ*) and average taxonomic distinctness (Δ+). Bottom trawls were performed using an experimental net to an average depth of 5 m, between 9:00 to 17:00 h 1361 organisms were observed, belonging to 44 species on 35 genera. According to the average alpha, beta and gamma diversity indices, the season with higher value on average alpha diversity was summer, with 6.68 species followed by spring with 5.73 species. In beta´s case the highest value was observed during spring (21.27%) followed by summer (20.18%). Taking gamma in account, the highest values were observed during spring and summer, both seasons with 27 species each. The lowest values observed according to the average alpha beta and gamma indices, was observed during winter season (5.27, 20.18% and 20 species, respectively). In the spatial analysis, the average taxonomic distinctness index (Δ+) show a significant difference (p ≤ 0.05), while taxonomic distinctness index (Δ*) showed no significant difference (p ≥ 0.05). In the temporal analysis both indices showed no difference (p ≥ 0.05).
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