Hydroacoustic surveys as contribution to the study of spawning aggregations of Nassau Grouper (Epinephelus striatus) in the Yucatan

One of the main species in the Caribbean cost of Yucatan-Mexico is the Mero (Epinephelus striatus), but the fisheries are beginning to go down and the principal reason could be the over-catch. The objective of this work is to study the aggregations of the Nassau Grouper, as well as the rest of the fish populations associated with the slope of the Mexican Caribbean of the Yucatán Peninsula, using hydroacoustic methods, and to establish a methodology that allows the continuation of these studies for the evaluation and a major knowledge of these resources. In this area the evaluation of the fisheries of fish has not been a priority. Some acoustic surveys were made over three years trying to have a contact with the aggregation of Mero in the spawning season. The place selected was the Mahahual beach and the south of Chinchorro Bank Reserve. Many triangular transects were execute from 8 m depth to the end of the talud till 60m. The main hydroacoustic equipments used was the BIOSONICS DT-5000 at a frequency of 130 kHz and BIOSONICS DT-X at 208 kHz that represented a good method to study this specie. The TS (target strength) analysis are giving for different depth stratas, the must quantity of fish with TS between -35 and -20dB were detected in the slopes of 30 and 50 m depth, possibly Mero in spawning. Visual observations from divers reported some individuals Mero and school of different species that are common in this area. No expected concentrations of Mero were found but some fishermen report a high Mero aggregation in January 2001 in Xcalak at south of the surveys.