NOTE Lozano-Alvarez et al.: Occurrence and seasonal variations of Panulirus argus 



809 



v. I 



'87.' 



89W 



~S USA 



GULF OF MEXICO 



\l»t« Mulam 



Punta Allen 



ishladela Ascension 



hla da I Eaplrltu Santo 



Punta Harraro 



191 



'•' .Y*VBanco Chlochorro 



V 



*"'" 8 6- 



lA: I 



Punta 

 Pa|aroa 



Punta Tupac 



_19'20 



J 



Figure 1 



(A) The coast of Quintana Roo, showing the main fishing localities for Panulirus argus. (B) Bahia de la 

 Ascension. Black areas denote coral reef tracts; shaded areas show the sector of the shelf where exploratory 

 fishings with traps were carried out. Casitas for lobster fishing were used coastward from the coral reef. 



locate suitable bottoms for installing traps to minimize 

 trap loss. In certain areas where the deep reefs are well 

 developed (e.g., offshore from Punta Allen, Fig. IB ), no 

 suitable bottoms were found. Thus, fishing operations 

 were constrained to a range of depths between 15 and 

 30 m, from Nicchehabim Reef to Punta Pajaros (Fig. IB). 



Because soak time does not affect catch rate of the 

 traps (Lozano-Alvarez et al., 1991b, Lozano-Alvarez 

 and Negrete-Soto, 1991), we considered the number of 

 lobsters per trap-lift as a gross index of abundance. 

 Carapace length (CL) of lobsters was measured 

 (±0.1 mm) from between the rostral horns to the poste- 

 rior dorsal edge of the cephalotorax. Carapace state of 

 lobsters was recorded following an arbitrary scale from 

 1 (newly molted and completely clean) to 4 (heavily 

 fouled), as a relative indicator of the time elapsed since 

 the last molt (Kanciruk and Herrnkind, 1976). Females 

 were considered non-reproductive (NR) when eggs were 

 absent, the carapace was clean, and no traces of sper- 

 matophores were found on the sternum. Reproductive 

 females comprised those that presented a new sper- 

 matophore attached to the sternum (SP); external eggs 

 attached to the pleopods (EE); or empty egg capsules 

 remaining on the pleopods (EC). 



To compare the size distribution and general fea- 

 tures of the lobsters found on the shelf outside the bay 



with those from the bay, two different groups of data 

 were obtained from the bay area. Throughout the 

 fishing season, July 1989-February 1990, monthly data 

 from a number of boxes of lobster tails, categorized by 

 tail weight (TW, g) class, were obtained from a local 

 processing plant. This plant receives all the catch from 

 the bay area. The data were transformed to CL by 

 applying the following equation: Log TW (g)= 2.550 

 log CL (mm) -2.69298 (Lozano-Alvarez et al, 1989). 

 However, because the size structure of the catch is 

 constrained by the minimum size limit and includes 

 lobsters caught on the fore-reef down to a depth of 15 

 m, and the catch data gives no information on sex or 

 reproductive activity, we also used data from Lozano- 

 Alvarez et al. (1991a) taken during a tagging opera- 

 tion carried out in May-June 1986, which comprised 

 lobsters found solely beneath casitas throughout the 

 bay, as a less biased estimate of size structure, sex 

 ratio, and carapace state of lobsters in the bay. 



Student's t-test (Zar, 1984) was used to compare log- 

 transformed data on seasonal abundance of lobsters 

 (number of lobsters per trap-lift), mean sizes between 

 males and females, and mean sizes between shelf and 

 bay lobsters. Sex-ratios were compared with a x 2 test. 

 Mean sizes of summer and winter lobster catches taken 

 on the shelf outside the bay were compared with a 



