Structure of the Ichthyofauna associated with soft bottoms in San Ignacio Lagoon, Baja California Sur, Mexico

San Ignacio Lagoon is located within the Vizcaíno Biosphere Reserve. There has been limited study of its ichthyofauna to date; the objective of this chapter is to describe the composition and distribution, as well as the temporal and spatial abundance of the ichthyofauna associated with soft bottoms in this coastal lagoon. A total of 44 trawls were carried out over a 346,500 m2 area. A total of 11 trawls per season were carried out, covering an 86,625 m2 area (7,875 m2 per trawl). A total of 1,361 organisms were collected, with a total biomass of 67,118 g. The ichthyofauna of this lagoon was composed of 21 families, 35 genera, and 44 species. The highest abundance of organisms and biomass was obtained during the autumn (34.6% and 30.4%, respectively), while the lowest abundance and biomass were obtained in the spring (16.5% and 13.5%, respectively). Of the 44 recorded species, eight were present during the overall study period (S. annulatus, S. lispus, E. dowii, P. maculatofasciatus, Urobatis halleri, Hypsopsetta guttulata, Hippocampus ingens, and Paralichtyes californicus). The Biological Value Index showed that 25 species were dominant in this ecosystem. The species diversity was highest in winter (2.28 bits/ind.) and lowest during the autumn (0.41 bits/ind.). Water temperature was similar in spring and autumn (21.1°C and 20.9°C, respectively), and was higher in the summer (24.9°C). The zoogeographic affinity analysis showed that the provinces with the highest number of records were the Panamic (36%) and San Diego (31.8%) Provinces.