220 



Fishery Bulletin 103(1) 



'(*i | i i | i i | i i | i i | i i | i i | i i | i i | i i | i i | i i | IT] i i | i i | i ifnyf i | i i | i i | i i | i i | i i | i r | I r ! i i ! i i| i i | i i | i i | i i | i 



Jan Apr Jul Oct Jan Apr Jul Oct Jan Apr Jul Oct Jan Apr Jul Oct Jan Apr Jul Oct Jan Apr Jul Oct Jan Apr Jul Oct Jan Apr Jul Oct 



1995 



1996 



1997 



1998 1999 



Month 



2000 



2001 



2002 



Figure 1 



Monthly landings (in metric tons) of Dosidicus gigas in Mexico from 1995 through 2002. 



Materials and methods 



Santa 1_, 

 Rosalia ? 



BAJA 



CALIFORNIA 



SUR 



Fieldwork was carried out in two sepa- 

 rate experiments along both coasts of the 

 Guaymas basin (see Fig. 2). This area of 

 the central part of the Gulf of California 

 accounts for more than 95% of Mexican 

 jumbo squid landings. A total of 996 squid 

 were tagged between 9 and 16 October 

 2001, in the general vicinity of Sta. Rosa- 

 lia, Baja California Sur (B.C.S.), as indi- 

 cated in Figure 2. Another 997 squid were 

 tagged off Guaymas, Sonora, between 3 

 and 7 April 2002. Both experiments were 

 conducted close to the anticipated end of 

 the respective fishing seasons for each 

 zone, because we hoped to obtain recap- 

 tures both locally and from more distant 

 sites after the squid had migrated away 

 from the fishing areas. 



Squid were caught by commercial fish- 

 ermen using hand-lines with 30-cm jigs 

 and were tagged on deck with spaghetti- 

 type, plastic cinch-up tags (Floy Tag Co., 

 Seattle, WA) through the anterior edge of 

 the dorsal mantle. This process took about 

 30 seconds, and the squid was then imme- 

 diately released. All squid quickly jetted away with no 

 obvious sign of trauma or physical impairment. Animals 

 with any visible damage, primarily form cannibalistic 

 attacks by other squid, were not tagged. In addition, 

 dorsal mantle length (ML) was measured to the nearest 

 mm for all squid in the Guaymas experiment. 



Tag-return information was imprinted on the tag, and 

 posters announcing the experiment were distributed at 

 squid-landing ports and at local processing facilities in 

 Sta. Rosalia, San Lucas, San Bruno, Mulege, Loreto 

 and La Paz (B.C.S.), as well as in San Carlos, Guay- 



Tag recoveries: 



' 1 C 11-16 

 © 2-3 f 



» 5-6 * 



SONORA 



juaymas 



Figure 2 



Map of the Guaymas basin in the central Gulf of California showing both coasts 

 where the tagging experiments were performed. Area of detailed main map is 

 indicated by a gray rectangle in upper leftmost inset. Numbers of tags deployed 

 are in bold type in main map. Symbols for the numbers of tags recovered are 

 indicated in the inset "Tag recoveries." Black symbols represent squid tagged 

 off Sta. Rosalia; white symbols represent squid tagged off Guaymas. Depth 

 contours are in meters. Adapted from Bischoff and Niemitz (1980). 



mas, Yavaros (Sonora) and Mazatlan (Sinaloa) (Fig. 2). 

 A monetary reward ($50 US) was offered for each tag 

 returned with information on recapture date and lo- 

 cation. During the second experiment an additional 

 reward was offered for information on squid ML and 

 stage of sexual maturity as defined by Lipinski and 

 Underhill (1995): immature (stages I— II ), maturing 

 (III) and mature (IV-V). Average daily growth rate 

 (DGR) was calculated from the increase in ML between 

 tagging and recapture divided by the number of days 

 elapsed during this period. 



