739 



Abstract— In the face of dramatic do- 

 clines in groundfish populations and 

 a lack of sufficient stock assessment 

 information, a need has arisen for new 



methods of assessing groundfish popu- 

 lations. We describe the integration of 

 seafloor transect data gathered by a 

 manned submersible with high-reso- 

 lution sonar imagery to produce a ha- 

 bitat-based stock assessment system 

 for groundfish. The data sets used in 

 this study were collected from Heceta 

 Bank, Oregon, and were derived from 

 42 submersible dives (1988-90) and 

 a multibeam sonar survey (1998). 

 The submersible habitat survey in- 

 vestigated seafloor topography and 

 groundfish abundance along 30-minute 

 transects over six predetermined sta- 

 tions and found a statistical relation- 

 ship between habitat variability and 

 groundfish distribution and abundance. 

 These transects were analyzed in a 

 geographic information system (GIS) 

 by using dynamic segmentation to dis- 

 play changes in habitat along the tran- 

 sects. We used the submersible data to 

 extrapolate fish abundance within uni- 

 form habitat patches over broad areas 

 of the bank by means of a habitat classi- 

 fication based on the sonar imagery. 

 Alter applying a navigation correction 

 to the submersible-based habitat seg- 

 ments, a good correlation with major 

 boundaries on the backscatter and 

 topographic boundaries on the imagery 

 were apparent. Extrapolation of the 

 extent of uniform habitats was made 

 in the vicinity of the dive stations and 

 a preliminary stock assessment of sev- 

 eral species of demersal fish was calcu- 

 lated. Such a habitat-based approach 

 will allow researchers to characterize 

 marine communities over large areas 

 of the seafloor. 



Integration of submersible transect data and 

 high-resolution multibeam sonar imagery for 

 a habitat-based groundfish assessment of 

 Heceta Bank, Oregon* 



Nicole M. Nasby-Lucas 



Pfleger Insdtute of Environmental Research 

 901 -B Pier View Way 

 Oceanside, Calilornia 92054 

 E mail address: nnasbyig yahoo, com 



Bob W. Embley 



Pacific Marine Environmental Laboratory, NOAA 

 Hatfield Manne Science Center 

 Newport, Oregon 97365 



Mark A. Hixon 



Department of Zoology 

 Oregon State University 

 Corvallis, Oregon 97331 



Susan G. Merle 



Cooperative Institute for Manne Resources Studies 

 Hatfield Manne Science Center 

 Newport, Oregon 97365 



Brian N. Tissot 



Program in Environmental Science and Regional 



Planning 

 Washington State University 

 Vancouver, Washington 98686 



Dawn J. Wright 



Department of Geosciences 

 Oregon State University 

 Corvallis, OR 97331 



Manuscript accepted 29 May 2002. 

 Fish. Bull. 100:739-751 (2002). 



Dramatic declines in several grouncifish 

 populations have occurred along the 

 U.S. West Coast during the last decade 

 (Ralston, 1998: PFMC^; Sampson,^ 

 Bloeser'). One problem exacerbating 

 these declines is that current stock 

 assessments are not sufficiently precise 

 or accurate to effect empirically based 

 management. This is especially true 

 for commercially important species 

 of rockfish (Scorpaenidae, Sebastes). 

 which comprise major groundfish fish- 

 eries along the Pacific Coast. Although 

 evidence has accumulated for sub- 

 stantial declines in the abundance of 

 several species of rockfish, the overall 

 picture is unclear because 42 of 54 

 rockfish species ( 78'7r ) have never been 

 assessed (Ralston, 1998; NMFS, 1999; 

 Bloeser^). Of the 12 species that have 

 been assessed by the National Marine 

 Fisheries Service, five were listed as 

 "overfished" and one species was listed 

 as "approaching overfished condition" 

 (NMFS, 1999). 



A possible alternative to single-spe- 

 cies stock assessments of demersal 

 fishes is a habitat-based community 

 assessment, which serves to estimate 

 groundfish population sizes by recog- 

 nizing that species are not randomly 

 distributed among varying habitats. It 



is known that the diversity, quality, and 

 extent of bottom habitats are impor- 

 tant in determining the distribution, 

 abundance, and diversity of rockfishes 

 (Carlson and Straty, 1981; Pearcy et 

 al., 1989; Carr, 1991; Stein et al., 1992; 

 O'Connell and Carlile, 1993). It has 

 been previously demonstrated, within 

 local study areas, that species richness 

 and composition correlate with seafloor 

 texture (Hallacher and Roberts, 1985; 

 Richards, 1986; Love et al., 1991; Stein 

 et al., 1992; Krieger, 1993; Yoklavich et 



* Contribution 2477 of the Pacific Marine 

 Laboratory, Newport, Oregon 97365. 



1 PFMC (Pacific Fishery Management Council). 

 1999. Status of the Pacific Coast ground- 

 fish gishery through 1999 and recom- 

 mended acceptable biological catches for 

 2000: stock assessment and fishery evalu- 

 ation, 75 p. Pacific Fishery Management 

 Council, 7700 NE Ambassador Place, Suite 

 200, Portland, OR 97220. 



- Sampson, D. B. 1997. Effective fishing 

 effort in the Oregon groundfish trawl fish- 

 ery. Final report to the Oregon Trawl Com- 

 mission, 80 p. Oregon Trawl Commission, 

 PO. Box 569, Astoria, OR 97103. 



■^ Bloeser, J. A 1999. Diminishing returns: 

 the status of west coast rockfish. Pacific 

 Marine Conservation Council, P.O. Box 59, 

 Astoria, OR 97103. 



