Butler et al.: Biology and population dynamics of Sebastes levis in the southern California Bight 



261 



CPUE 



0,001 -0 014 

 014-0.047 

 047 - 0.083 

 083-0.145 



145-0.223 

 0.223 - 0.333 

 0.333 - 0.478 

 0.478-0 78 

 0.78- 1.452 



1 452- 3.1 



121° 



120° 



119° 



118- 



117° 



Figure 1 



Cowcod habitat in central and southern CaHfornia. The southern CaUfornia 

 Bight (SCB) between Pt. Conception and the Mexico-U.S. border is the center of 

 the cowcod population's distribution. Assumed habitat areas for adult cowcod at 

 100-300 m are shaded light gray. Square outlines identify California Department 

 of Fish and Game fishing blocks (generally lO'xlO') used to analyze commercial 

 passenger fishing vessel (CPFV) logbook data. Dots show CPFV mean catch rates 

 (cowcod per angler day) for each fishing block during the 1964-74 seasons (no dot 

 means zero CPUE). 



ichthyoplankton surveys is during January-April, and 

 some larvae are present during November- August (Moser 

 et al., 1994). Cowcod larvae spend about 100 days in the 

 plankton and settle to the bottom as juveniles at about 

 50-60 mm FL (Johnson, 1997). 



Cowcod are found at depths of 20-500 m. Juveniles (50% 

 maturity at about 44 cm FL [Love et al., 19901 ) generally 

 inhabit relatively shallow water (<100 m) on relatively 

 sandy bottom and adults generally inhabit deeper water 

 {>100 m) on rocky bottom (Miller and Lea, 1972; Esch- 

 meyer et al., 1983; Butler et al., 1999). Average length 

 of cowcod increases with depth (Love et al. 1990) as is 

 the case with many other species along the west coast of 

 North America (Jacobson et al., 2001). Adult cowcod habi- 

 tat off Southern California comprises a series of basins 

 and ridges that form islands and offshore banks (Emery, 

 1960). Juveniles in Monterey Bay recruit to fine sand and 

 clay sediments at depths of 40-100 m during the months 

 of March-September (Johnson, 1997). In submersible 

 surveys at the northern end of the SCB, juvenile cowcod 

 (<40 cm TL) were most common at 90-149 m and adults 

 were most common at depths of 120-209 m (Butler et al., 

 1999). California commercial bottom trawl fishermen take 

 cowcod at depths of 120-500 m, but mainly at 120-300 m 

 (Fig. 2). We used total bottom area at 100-300 m (measured 



using a geographic information system and depth data) 

 as a crude estimate of habitat area for cowcod (Fig. 1, see 

 "Discussion" section). 



Cowcod are an important part of multispecies commer- 

 cial and recreational fisheries off central and southern 

 California. Fishermen target cowcod, particularly in the 

 recreational fishery, because of their large body size. Close 

 association with rocky bottom features makes adult cowcod 

 relatively easy to catch with stationary gear (e.g. hook-and- 

 line and set nets) in both the recreational and commercial 

 fisheries. Prior to 1983, the recreational fishery accounted 

 for most of the annual catch, but the commercial fishery 

 was usually dominant during subsequent years. 



Commercial fishery 



Cowcod have been landed in fifteen different California 

 Department of Fish and Game market categories. Like- 

 wise, fourteen species of Sebastes have been landed in the 

 cowcod market category. Of these, the bronzespotted rock- 

 fish, S. gilli, is most common. Exvessel (wholesale) prices 

 (adjusted for inflation to 1998) paid by processors for land- 

 ings in the cowcod market category rose from $1.02/lb in 

 1981 to $1.56/lb in 1998 and peaked at $1.85/lb in 1990 

 (Butler etal., 1999). 



