Catch composition of the spiny lobster Panulirus gracilis (Decapoda: Palinuridae) off the western coast of Mexico

The lobster fishery in the Gulf of California and the south-central region of the western coast of Mexico consists of small-scale artisanal activity supported by Panulirus gracilis and P. inflatus, with an annual average catch of 132 ton. The present study analyzes the landing composition of this fishery and the population structure of P. gracilis. Carapace lengths (CL) for this species ranged from 35 to 125 mm, and the most frequent sizes were between 60 and 85 mm. The size distribution was approximately normal. This implies that the fishery is composed of several size classes, with annual recruitment to the fishing areas. For the 1989-1990 and 1990-1991 fishing seasons, the mean monthly sizes of males were between 70.18 +/- 11.74 and 81.11 +/- 6.76 mm CL, whereas females averaged from 73.60 +/- 8.95 to 80.28 +/- 7.53 mm CL. Power-law relationships between carapace length (CL in mm) and total weight (TW in g) were determined, resulting in the following equations: PT = 0.0021 CL2.7689 for males and PT = 0.0009 CL3.0038 for females. During certain periods of the year, males dominated the catch; however, the overall annual male: female ratio was near 1:1.