Pearcy: Movements of acoustically-tagged Setosfes flavidus 



731 



44 01,5 — 



44 01 



144 52 



124 51 0' 



Figure 6 



Tracks of eight of the yellowtail rockfish Sehastes flamdus released on 15 August, one 

 month later during the period 16-18 September 1990. Symbols designate positions of 

 each fish. 



water above a 68m rocky bottom. Four of these fish 

 were released at capture site A, four at 0.5 nmi to the 

 north (site B, bottom depth 70m), and four at 2.0 nmi 

 to the north (site C, bottom depth 87m) (Fig. 5). The 

 two release sites to the north of the capture site had 

 high-relief bottom topography, similar to the capture 

 site. In addition, schools of rockfish, similar in appear- 

 ance acoustically to those comprised of yellowtail rock- 

 fish, were observed in the vicinity of the two displace- 

 ment sites. Since yellowtail rockfish are numerous over 

 shallow (<100m) rocky ridge, boulder, and cobble 

 habitats of Heceta Bank, and schools of yellowtail 

 rockfish were seen from submersibles near release sites 

 B and C (Pearcy et al. 1989, Hixon et al. 1991), I as- 

 sumed that the transplant release sites were habitable 

 by yellowtail rockfish. 



The morning after the releases, all four of the trans- 

 mitters in fish released at capture site A were detected 

 within 0.1 nmi of site A. One of the fish (23) released 

 0.5 nmi to the north returned to the capture site over- 

 night, after 17h. No transmitters were detected at the 

 other two release sites on the following day when the 

 ship passed over these locations and departed the bank. 



Eleven of the twelve fish were located 13 days after 

 release when we returned to Heceta Bank, including 

 all four released at site C (2.0 nmi to the north) (Fig. 

 5). The missing transmitter was from site B. All 11 fish 

 were found at least once within 0.1 5 nmi of the capture 

 site (Fig. 5). These results are evidence for a strong 

 homing tendency. 



Two fish that were caught and released at the orig- 

 inal capture location (site A) showed the most ex- 

 tensive short-term movements (Fig. 5). Fish 26 was 



located 0.8 nmi and Fish 31 was 

 found 0.5 nmi north of site A dur- 

 ing the night and early morning 

 of 28-29 August, 14 days after 

 release. Both returned to site A 

 about 11 h later. Fish 27, dis- 

 placed to site C, was found 0.15 

 nmi east of capture site A and 

 then moved 0.24 nmi to the north 

 during a 2-hour period on the 

 evening of 29 August. 



One month after releases, we 

 returned to the capture location 

 to study longer-term movements. 

 No transmitters were detected in 

 the immediate vicinity of the orig- 

 inal capture location. Using an ex- 

 panding rectangular search pat- 

 tern, 8 of the 12 transmitters were 

 discovered, all south and a distance 

 of ~0.1-0.7nmi from the capture 

 location. Locations of these fish 

 were determined over the next 2.5 days during three 

 periods between submersible operations. The fish were 

 scattered along a 1.1 nmi east-west axis (Fig. 6). Most 

 fish demonstrated short-term movements of over 0.1 

 nmi (our nominal error of navigation) during these 2.5 

 days. Two fish (23 and 28) moved ~0.5nmi. Only one 

 fish (22) ended up near the location where it was ini- 

 tially found on this cruise. None of these eight fish was 

 found closer than 0.1 nmi to the original capture site, 

 and most were 0.4 nmi away. There was no evidence 

 that these fish stayed in a common school or within a 

 small home range, as found earlier in the summer. 



Vertical movements 



Pressure-telemetering (depth sensor) transmitters 

 were used during 1989 and 1990, but due to problems 

 with the receiver, limited data were obtained. Figure 

 7 shows the maximum and minimum depths for 10-min 

 intervals for three fish monitored almost continuously 

 during 21-22 and 24-25 August 1989. Fish were usual- 

 ly in midwater, inhabiting depths of 25-50 m where the 

 bottom was ~75m. Short-duration vertical movements 

 were seen for all fish, usually rapid descent/ascent 

 ("bounce") dives to or close to the bottom, followed by 

 rapid vertical ascents back to depths of 25-35 m. Fish 

 2 made nine of these "bounce dives" to the bottom dur- 

 ing the early morning of 24 August over about a 4h 

 period. Other than this series of dives, there was little 

 evidence for any diel patterns in the frequency of ver- 

 tical migrations of fish that were tagged. Fish 3 either 

 regurgitated its transmitter or rested on the bottom 

 after 0700 h on 25 August (Fig. 7). 



