Abstract. - Commercial and 

 sport landings of white seabass have 

 declined, particularly in southern 

 California, and the populations now 

 appear to be severely impacted. To 

 provide information critical to the 

 management of this species, settle- 

 ment patterns of white seabass with- 

 in the Southern California Bight 

 were investigated for 1988-89. Data 

 were obtained from 16 stations sam- 

 pled along the southern California 

 coastline during June-October 1988, 

 and at 12 stations sampled along the 

 coasts of the mainland and four 

 Channel Islands May-August 1989. 

 At each station, four 5-minute tows 

 were taken with a 1.6 m beam trawl 

 at each of two depths, 5 and 10m. 



Most young-of-the-year white sea- 

 bass were <10mmSL and had set- 

 tled within 2-3 weeks of capture. 

 Density estimates for white seabass 

 off southern California were low, 

 ranging from 0.3 to only 37.8 individ- 

 uals per hectare. In 1988, catch-per- 

 unit-effort (CPUE) peaked in July 

 (1.10/tow) with differences being sta- 

 tistically significant among months. 

 In 1989, CPUE peaked in June 

 (0.45/tow) with differences being 

 statistically significant among 

 distance blocks from the mainland. 

 CPUE was 15 times higher at the 

 mainland stations compared with the 

 island stations (0.59/tow vs. 0.04/ 

 tow). Abundance was significantly 

 correlated with warm bottom-water 

 temperatures in 1988, although not 

 in 1989. 



Multivariate analysis of the catches 

 with selected environmental vari- 

 ables indicated that distance from 

 the mainland and bottom tempera- 

 ture may have been important fac- 

 tors influencing settlement. However, 

 in combination, these two variables 

 accounted for only 5% of the total 

 variance {R'^ 0.05) in abundance. 

 This finding implies that other fac- 

 tors, most notably the availability of 

 premetamorphic larvae, probably 

 have an influence on white seabass 

 settlement and need to be considered 

 in future studies. 



Abundance, distribution, and 

 settlement of young-of-the-year 

 whiite seabass Atractoscion nobilis 

 in tlie Southern California 

 Bight 1988-89* 



Larry G. Allen 



Department of Biology. California State University, NortfiFT dyL ' , Cd l ifu i i lia 9 1 J30 i .. , 



i luuiiiifi Biological Laboratory | 



Michael P. Franklin i LIBRARY 



i' 



Department of Biology, California State University, Northridge, California 91330 

 Present address: Department of Biological Sciences j MAR 1 ^ 1993 



University of California. Santa Barbara, California 9B106 



The white sesbs.?,?, Atractoscion nobi- 

 lis is the largest croaker (family Sci- 

 aenidae) occurring off southern Cali- 

 fornia (Miller and Lea 1974), where 

 it is important in both commercial 

 and sport fisheries. Despite attempts 

 to improve the fishery (e.g., impos- 

 ing minimum size requirements 

 and limits on sport and commercial 

 catches; Frey 1971), landings con- 

 tinue to decline and the stocks appear 

 to be severely impacted (Vojkovich 

 and Reed 1983), particularly in 

 southern California waters. 



Despite their impacted status and 

 economic importance, little was 

 known about the early-life-history 

 stages of white seabass until recent- 

 ly. Moser et al. (1983) described the 

 larval development from hatchery- 

 reared eggs. Field investigations of 

 early-life-history stages were limited 

 to reports of larval occtirrence wnthin 

 California Cooperative Fisheries In- 

 vestigations (CalCOFI) collections 

 from 1950 to 1978. For example, 

 Moser et al. (1983) found that only 

 15% of white seabass larvae were 

 taken in southern California waters. 

 Most were taken near Sebastian 

 Viscano and San Juanico Bays, Baja 

 California. 



Manuscript accepted 8 July 1992. 

 Fishery Bulletin, U.S. 90:633-641 (1992). 



' Contribution 67 of the Ocean Studies Insti- 

 tute, California State University. 



A few studies have provided lim- 

 ited information on the yoimg-of-year 

 (YOY) stages of white seabass. Allen 

 and Franklin (1988) examined the 

 abundance and distribution of juve- 

 nile white seabass in the vicinity of 

 Long Beach harbor and developed a 

 model for locating YOY white sea- 

 bass in coastal waters. We observed 

 that YOY white seabass were cap- 

 tured over sandy bottoms in shallow 

 water near the breaker line, most 

 often with submerged aquatic vege- 

 tation (drift algae: green, brown, 

 and red), encrusting bryozoans, and 

 terrestrial debris. This area seems to 

 be the nursery grounds for white 

 seabass. The drift material may be an 

 important component of these nur- 

 sery areas because these fish appear 

 to be structure-oriented early in life 

 (Allen and Franklin 1988, Margulies 

 1989, Donohoe 1990). Donohoe 

 (1990), based on field collections, 

 found that young seabass were asso- 

 ciated with the drift, and also ob- 

 served that the larvae and juveniles 

 moved toward structures in labora- 

 tory experiments. A significant rela- 

 tionship was found between the mass 

 of drift algae and the occurrence of 

 YOY white seabass from Oceanside, 

 California to the Mexican border, 

 suggesting that the drift habitat may 

 influence the distribution patterns 



633 



