Abstract

A diving survey was carried out in the central area Alacranes reef between February 14 to 21 of 1997. The objective was to obtain spiny lobster and queen conch density, abundance and queen conch instantaneous mortality rate estimations in one prominent fishing areas inside Alacranes reef. Data were collected by free dive with average velocity of 750 m/h, diving time between 15 to 30 minutes. In total 41 transects and 14 :3l diving time hours and total search area 101,646 m2 were carried out. Abundance estimation was performed using a random sampling design in a total inference area of 171,495,200 m2 (50 nautical miles) between 22° 22’ to 22° 35” LN and 89° 37’ to 89” 47’ LW and under assumption that 80% and 60% of the area is lobster and conch potential habitat respectively. Density distribution maps are show for each resource. Ageing of conchs were obtained using a key done with growth parameters reported for Mexican Caribbean coast and age structure was used for approach instantaneous mortality rate estimations. Lobster and conch average density was 3.31 lobster/ha and 4.71 conch/ha respectively ; abundance estimation was 45,435 ( +- 302: 95% confidence level ) lobsters and 49 166 (+- 516 ) conch. Lobster tail and conch meat average weigh was 0.159 (SD = 0.073) and 0.393(SD = 0.056) respectively. Biomass estimation was 7,204 kg of lobster tails and 19,322 kg of conch meat. Probable age of conch captured was between 3 to 13 years and instantaneous mortality rates was between 1.045 to 1.386.

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