521 



Abstract — Multibeam sonar mapping 

 techniques provide detailed benthic 

 habitat information that can be com- 

 bined with the data on species-specific 

 habitat preferences to provide highly 

 accurate calculations of populations 

 in a particular area. The amount 

 of suitable habitat available for the 

 endangered white abalone {Haliotis 

 sorenseni) was quantified to aid in 

 obtaining an accurate estimate of the 

 number of remaining individuals at 

 two offshore banks and one island 

 site off the coast of southern Cali- 

 fornia. Habitat was mapped by using 

 multibeam sonar survey techniques 

 and categorized by using rugosity and 

 topographic position analysis. Abalone 

 densities were evaluated by using a 

 remotely operated vehicle and video 

 transect methods. The total amount 

 of suitable habitat at these three 

 sites was far greater than that previ- 

 ously estimated. Therefore, although 

 present estimates of white abalone 

 densities are several orders of mag- 

 nitude lower than historic estimates, 

 the total population is likely larger 

 than previously reported because of 

 the additional amount of habitat sur- 

 veyed in this study. 



The use of multibeam sonar mapping techniques 

 to refine population estimates 

 of the endangered white abalone 

 {Haliotis sorenseni) 



John Butler (contact author)' 



Melissa Neuman^ 



Deanna Pinkard' 



RIkk Kvitek^ 



Guy Cochrane* 



' National Marine Fisheries Service 

 Southwest Fisheries Science Center 

 8604 La Jolla Shores Drive 

 La Jolla, California 92037 

 Email address for J. Butler: John.ButleriSnoaa.gov 



^ National Marine Fisheries Service, Southwest Region 

 501 West Ocean Blvd 

 Long Beach, California 90802 



^ California State University, Monterey Bay 

 100 Campus Center 

 Seaside, California 93955 



'' United States Geological Service 

 345 Middlefield Road 

 Menio Park, California 94025 



Manuscript submitted 2 May 2005 

 to the Scientific Editor's Office. 



Manuscript approved for publication 



6 December 2006 by the Scientific Editor. 



Fish. Bull. 104:521-532 (2006>. 



Accurate classification of habitat is 

 important for examinations of the dis- 

 tribution and abundance of marine 

 organisms. The potential complexity 

 of species-habitat relationships is such 

 that the use of a single parameter 

 when trying to link species to specific 

 areas has become obsolete. Multiple 

 physical oceanographic parameters 

 that link species to their habitat 

 have proven to be useful, although 

 they are not applicable to all types 

 of marine organisms (Freeman and 

 Rogers, 2003). The use of high-resolu- 

 tion multibeam sonar maps for clas- 

 sifying habitat has become a critical 

 step in the process of estimating 

 the distribution and abundance of 

 marine animals that are known to 

 be associated with particular habi- 

 tat types. Because an increasing 

 number of marine resources are in 

 states of decline, information on the 

 amount of habitat of specific types and 

 qualities becomes crucial to making 

 predictions for the purposes of fisher- 

 ies management, and to aid in deci- 

 sions concerning potential locations 



of marine protected areas (Kvitek et 

 al.'; lampietro et al., in press). For 

 species in states of decline, protection 

 of known critical habitat may be the 

 only approach available to enhance 

 survival of the species. Detailed habi- 

 tat mapping provides a large amount 

 of information on the benthic makeup 

 of an area in a relatively short amount 

 of time, and further processing of data 

 with GIS (geographic information 

 system) can produce accurate esti- 

 mates of actual areas categorized by 

 various physical parameters. These 

 pieces of information, coupled with 

 field surveys to obtain information on 

 animal or plant habitat associations. 



1 Kvitek, R., P. lampietro, C. Bretz, K. 

 Thomas, S. Zurita, B. Jones, and E. 

 Morris. 2004. Hydrographic data 

 acquisition in support of MLPA and 

 MLMA Implementation. California 

 Department of Fish and Game Final 

 Report P0170015, p. 1-74. Foundation 

 of California State University Monterey 

 Bay, 100 Campus Center, Seaside, CA 

 93955. 



