Abstract. - Movements of 25 

 yellowtail rockfish Sebastes flavidus 

 on Heceta Bank, off Oregon, were 

 studied by acoustical tagging and 

 tracking during the summers of 

 1988-90. Some fish were tracked dis- 

 continuously up to 1 month after 

 transmitters were inserted into their 

 stomachs. In each year, some fish re- 

 mained at the capture site after 

 release or returned after displace- 

 ment to a different release site. In 

 1990, the year of most intensive tag- 

 ging, 11 of 12 fish were detected 

 near the capture location 13 days 

 after release in August 1990, in- 

 cluding 3 of 4 fish displaced 0.5 nmi 

 (0.9km), all 4 fish displaced 2.0 nmi 

 (3.7 km), and all 4 of the fish released 

 at the capture site. One fish homed 

 overnight from the release site 0.5 

 nmi away. In September 1990, 1 

 month after release, eight of these 

 fish had dispersed up to 0.1-0.7nmi 

 (0.2-1. 3km) to the south of their cap- 

 ture location, suggesting a change 

 in site fidelity. Pressure-sensitive 

 transmitters showed that tagged 

 yellowtail rockfish usually remained 

 at midwater depths of 25-35 m, well 

 above the sea floor depth of ~75m. 

 Rapid descents to nearbottom depths 

 were common, but no obvious diel 

 vertical or horizontal migrations 

 were detected. 



Movements of acoustically-tagged 

 yellowtail rockfish Sebastes flavidus 

 on Heceta Bank, Oregon 



William G. Pearcy 



College of Oceanography. Oregon State University. Corvallis, Oregon 97331-5503 



Manuscript accepted 13 July 1992. 

 Fishery Bulletin, U.S. 90:726-735(1992). 



The yellowtail rockfish Sebastes Jlavi- 

 dus is a common rockfish along the 

 west coast of North America. It is 

 caught by both commercial and rec- 

 reational fishermen and was one of 

 the most abundant rockfish species in 

 commercial groundfish landings from 

 the U.S. west coast from 1982 to 

 1990 (Pacific Fisheries Management 

 Council 1991). 



Schools of yellowtail rockfish may 

 persist at the same location for many 

 years. Carlson (1986) reported that 

 a school of adult yellowtail rockfish 

 in southeastern Alaska consisted of 

 individuals from one or two year- 

 classes and had negligible recruit- 

 ment over an 11-year period. Be- 

 cause their aggregrations may be 

 site-specific with limited interchange 

 of adults, and because rockfish are 

 long-lived, late-maturing, and of low 

 fecundity (Gunderson et al 1980, 

 Love et al. 1990, Eldridge et al. 

 1991), overfishing or disturbances, 

 such as habitat modifications from 

 offshore mining or petroleum devel- 

 opment, may have long-lasting ef- 

 fects in a local area. On the other 

 hand, a rockfish species whose in- 

 dividuals move freely from reef to 

 reef may be less vulnerable to local- 

 ized disturbances (Love 1979). The 

 stability and areal range of rockfish 

 aggregations have important implica- 

 tions for assessment, availability, and 

 management of rockfish species. 



The yellowtail rockfish is the most 

 abundant, large-sized schooling fish 

 seen from submersibles over the 

 shallow, rocky areas on the top of 

 Heceta Bank, a deep reef located 

 ~55km off the central Oregon coast 



(Pearcy et al. 1989; Figs. 1 and 2). 

 Large pelagic schools, sometimes of 

 a thousand or more individuals, were 

 observed over shallow portions of the 

 bank (<150m) during the summer. 

 Based on both observations from 

 submersible dives and the occurrence 

 of large echo-groups recorded by the 

 ships' echosounders, these schools 

 were often associated with pinnacles 

 or high-relief topography (Pearcy et 

 al. 1989). 



During one dive, a school of yellow- 

 tail rockfish followed the submersible 

 along the bottom for over an hour 

 before abruptly turning and swim- 

 ming back toward the location where 

 the school was initially encountered 

 (Pearcy et al. 1989). This observation 

 and those of Carlson and Haight 

 (1972), who found that individual 

 rockfish returned to a home site in 

 southeast Alaska after being dis- 

 placed as far as 22.5km, suggest that 

 schools of yellowtail rockfish may 

 have home ranges centered around a 

 specific site on the bank. 



Pelagic rockfishes, such as the 

 yellowtail rockfish, may range over 

 wider areas than benthic rockfishes. 

 However, little is known about the 

 vertical distribution or diel vertical 

 migrations of yellowtail rockfish, or 

 the relationships between vertical 

 and horizontal movements. 



This study used acoustical tracking 

 to determine the horizontal and ver- 

 tical movements and site-specificity 

 of yellowtail rockfish on Heceta 

 Bank. In this paper, I define site- 

 specificity as the tendency of fish to 

 inhabit a specific localized area as 

 opposed to free-ranging or vagrant 



726 



