326 



Fishery Bulletin 100(2) 



t Receiver locations 

 • Fish release locations 



I 1998 study site 1 



II 1998 study site 2 

 Signal detection 





Meters 



n range / Zone 3 ^"^[""""^s* ^°"^ \' 



,-----. ', ""'34/ I v2one2\ / 



/ Zone 5 ^V -^-'fi / *--_l'^ 



/ /\ ^ i«^^ -3 Rcv'2 / 



1 D„„<: * .. / ^-CVl? / 



400 800 





v,"' ,,,- --1*.' ' 



I ^^ 1" >?, Zone 4 



Rcvr4 



18.20 



— - w 



'^one 6 



4FICvr6 



I 100 m \, 

 I \ 



36 48 0' - 



Figure 2 



Fish-release locations with tag numbers, receiver locations, current meter loca- 

 tion (moored with receiver 11, expected signal detection range, and resulting 

 receiving zones for the 1998 field study of bocaccio. 



the tag was located within 800 m of that receiver and 

 outside the range of detection of other receivers. If a sig- 

 nal was recorded at the same time by two or more receiv- 

 ers, we knew the tag was somewhere within the intersec- 

 tion of the circles that represented the overlap of detection 

 range for the respective receivers. We defined the combi- 

 nations of intersections or exclusions of overlapping 800-m 

 detection ranges as "receiving zones." In 1997. five such 

 receiving zones were detected (Table 1). We labeled the 

 northeasternmost receiving zone (signals only recorded by 



receiver 1 ) as zone 1. Zone numbers increased to the south- 

 west. Because we knew the depths of all the gi-eenspotted 

 rockfish tracked in 1997. we were able to refine estimated 

 locations of a tag to the area in each receiving zone that 

 was between the 100-300 m isobaths (Fig. 1). 



In 1998, the same method provided 13 combinations of 

 overlapping detection ranges — too many to permit the pat- 

 terns of fish movement to be understood easily Conse- 

 quently, we gi'ouped combinations of overlapping detection 

 ranges into six receiving zones by their spatial distribution 



