646 



Abstract.— Economically valuable 

 Cahfomiahahbut.Parahchthyscaliforn- 

 iciis. and barred sand bass. Paralabrax 

 nebuhfer, along with other fishes, are 

 often abundant in the shallow areas of 

 California bays during their early life 

 history. However, little is known about 

 their habitat use within these areas. We 

 investigated habitat use of juvenile 

 fishes in the shallow waters of an 

 embayment by towing a 1.6-m beam 

 trawl with 3-mm mesh through eelgrass 

 beds [Zostefa manna) and unvegetated 

 areas at depths <1.1 m in Alamitos Bay. 

 Tows were conducted monthly or bi- 

 monthly from May 1992 through No- 

 vember 1995. A total of 435 tows dur- 

 ing 31 months yielded 52,787 fishes 

 comprising 46 species. However, the 

 catch was dominated by only a few spe- 

 cies and consisted mostly of juveniles 

 and gobiid larvae. A total of 1157 Cali- 

 fornia halibut and 225 barred sand bass 

 were collected. California halibut were 

 2-6 times more abundant in unvegetated 

 areas than in eelgrass beds, whereas 

 barred sand bass were captured almost 

 exclusively in eelgrass. Abundance of 

 both species significantly decreased as 

 distance from the bay mouth increased. 

 Abundances of most other fishes also 

 varied considerably between habitats 

 and among sites. In contrast to Cali- 

 fornia halibut and barred sand bass, 

 abundances of other species were 

 higher at sites farther inside the bay. 

 Variations in water temperature, dis- 

 solved o.\ygen, salinity, eelgrass shoot 

 density, and eelgrass blade length failed 

 to e.xplain differences in abundance for 

 most fishes. Habitat and site selection 

 for juvenile California halibut and 

 barred sand bass may be related to lar- 

 val supply and to the first suitable area 

 encountered, but may be modified sub- 

 sequently by movement into other ar- 

 eas in search of preferred food items. 



Differential habitat use by California halibut, 

 Paralichthys californicus, barred sand bass, 

 Paralabrax nebulifer, and other juvenile 

 fishes in Alamitos Bay, California 



Charles F. Valle 

 John W. O'Brien 



Kris B. Wiese 



California Department of Fish and Game 



330 Golden Shore, Suite 50 



Long Beach, California 90802 



E mail address (for C F Valle) cvalleSdfg2 cagov 



Manuscript accepted 25 June 1998. 

 Fish. Bull. 97:646-660 ( 1999i. 



It is widely recognized that bays 

 and estuaries are important nurs- 

 ery grounds for many marine spe- 

 cies. Within these areas, numerous 

 studies have documented the impor- 

 tance of eelgrass, Zostera marina, 

 and other seagrasses as habitat for 

 fishes. The composition and abun- 

 dance of fishes in these habitats can 

 vary considerably from unvegetated 

 areas (Orth and Heck, 1980; Borton, 

 1982; reviewed in Orth et al., 1984; 

 Heck et al., 1989; Ferrell and Bell, 

 1991; Sogard and Able, 1991). 

 Seagrass habitats may be impor- 

 tant because of their associated food 

 resources or because they provide a 

 refuge from predation (Adams, 

 1976; Heck and Thoman, 1981; re- 

 viewed in Orth et al., 1984; Leber, 

 1985; Sogard and 011a, 1993). 



The association of fishes with 

 seagrass beds has been related to 

 various physical characteristics of 

 seagrass, such as shoot density, 

 blade length, and biomass (Adams, 

 1976; Orth and Heck, 1980; re- 

 viewed in Orth et al., 1984; Bell and 

 Westoby, 1986a). However, evidence 

 suggests that physical characteris- 

 tics of seagrasses may only affect 

 fish abundances on a local scale 

 such as within a seagrass bed, but 

 not over larger scales such as dif- 

 ferent beds within a bay (Bell and 

 Westoby, 1986b; Bell et al., 1988; 

 Sogard, 1989; Worthington et al.. 



1992). Instead, it has been sug- 

 gested that differing fish abun- 

 dances in seagrass beds across an 

 estuary are due to availability of 

 competent larvae; pelagic larvae of 

 some seagrass fishes settle indis- 

 criminately in the first seagrass bed 

 encountered regardless of seagrass 

 physical characteristics (Bell and 

 Westoby, 1986b; Bell et al., 1987, 

 1988). According to this "settle and 

 stay" hypothesis, once within a 

 seagrass bed, fishes would move 

 around selecting microsites but 

 would not leave the seagrass bed 

 because of greater predation risks 

 associated with moving over unvege- 

 tated substrata. However, others 

 have found that initial settlement 

 patterns in habitats may be altered 

 considerably by postsettlement 

 mortality (Levin, 1994). migration 

 to other areas (Sogard, 1989), or by 

 both in response to available food 

 (Jenkins et al., 1996). 



Much of the work on seagrasses 

 and associated fishes has taken 

 place on the east coast of the United 

 States or in other parts of the world. 

 Although several studies have de- 

 scribed the ichthyofauna of south- 

 ern California bays (Allen and 

 Horn, 1975; Horn and Allen, 1976; 

 Allen, 1982; Allen and Herbinson, 

 1991), few studies have described 

 the relation of fishes with eelgrass 

 and other habitats. Understanding 



