Abstract.— Line transects run 

 from a manned submersible were 

 used to estimate the current den- 

 sity of yelloweye rockfish in two ar- 

 eas of the eastern Gulf of Alaska. 

 Yelloweye rockfish were seen in 

 cobble, continuous rock, broken rock, 

 and boulder habitats but were most 

 abundant in broken rock and boul- 

 der habitats. The presence of refuge 

 spaces appears to be an important 

 factor affecting occurrence of 

 yelloweye rockfish. Boulder areas in 

 deep water (>108m) were the most 

 densely-populated habitat, with an 

 estimated density of 9135 adult 

 yelloweye/km 2 . Overall density by 

 area and year ranged from 1954 to 

 2217 adult yelloweye rockfish/knr. 

 Habitat-specific density estimates 

 were less precise than general area 

 estimates because of smaller sample 

 sizes. For fisheries management, 

 density estimates may be extrapo- 

 lated to larger areas based on areal 

 estimation of yelloweye habitat from 

 available bathymetric data. 



Habitat-specific density of adult 

 yelloweye rockfish Sebastes 

 ruberrimus in the eastern Gulf 

 of Alaska* 



Victoria M. O'Connell 



Alaska Department of Fish and Game. 304 Lake Street, Room 1 03 

 Sitka. Alaska 99835 



David W. Carlile 



Alaska Department of Fish and Game. 802 3rd Street, Box 240020 

 Douglas, Alaska 99824-0020 



Manuscript accepted 28 January 1993. 

 Fishery- Bulletin, U.S. 91:304-309 1 19931. 



The yelloweye rockfish Sebastes 

 ruberrimus is the target species of 

 the commercial longline fishery for 

 Demersal Shelf Rockfishes (DSR) in 

 the eastern Gulf of Alaska (O'Connell 

 & Fujioka 1991). Rockfishes {Sebastes 

 spp.) are managed on an assemblage 

 basis in the Gulf of Alaska under the 

 advice of the North Pacific Fishery 

 Management Council (NPFMC). De- 

 mersal Shelf Rockfishes comprise 

 eight species of bottom-dwelling rock- 

 fishes inhabiting rocky areas of the 

 continental shelf; yelloweye rockfish 

 account for 96% of the landed catch 

 of targeted DSR. 



Traditional stock-assessment meth- 

 ods are difficult to apply to DSR be- 

 cause of a combination of behavioral 

 and physiological factors. The close 

 association of DSR with rugged bot- 

 tom precludes the use of bottom-trawl 

 surveys used for assessing other 

 groundfish in the Gulf of Alaska. Mark- 

 recapture studies are also ineffective 

 because rockfishes incur high embo- 

 lism mortality when brought to the 

 surface from depth (O'Connell 1991). 

 Consequently, prior to our research, 

 DSR was one of only two assemblages 

 managed under the Gulf of Alaska 

 Fisheries Management Plan for which 

 no biomass estimates were available. 



It has been well documented that 

 rockfish tend to be habitat-specific in 

 their distribution (Love & Ebeling 

 1978, Larson 1980, Richards 1986, 



Matthews 1991, Love et al. 1991, 

 Matthews & Richards 1991, Rosen- 

 thal et al. 1982). Therefore, to esti- 

 mate their abundance, we initiated 

 a project designed to take advantage 

 of the preference by DSR for rough, 

 rocky habitat. Our approach was 

 based on the assumption that DSR 

 abundance increases with structural 

 habitat complexity (i.e., increased to- 

 pographic relief and more interstitial 

 space in and between rocks). Our ob- 

 jective was to estimate density of 

 yelloweye rockfish in the Gulf of 

 Alaska for selected habitat and depth 

 categories. We hope to eventually de- 

 velop a model predicting the relation- 

 ship between DSR abundance and 

 habitat complexity and to use this 

 model to indirectly estimate the 

 abundance of DSR. If successful, this 

 approach would allow for expansion 

 of abundance estimates to other 

 areas in the eastern Gulf of Alaska 

 without replicating costly surveys. 



Methods 



Using the submersible Delta, we made 

 20 dives and covered 47 transects dur- 

 ing 17-25 August 1990 in two areas 

 off southeastern Alaska (Fig. 1). 



"Contribution PP-058 of the Alaska Depart- 

 ment of Fish and Game. Division of Commer- 

 cial Fisheries, Juneau. 



304 



