Valle et a\ Habitat use by Paralichthys califomicus and Paralabrax nebulifer 



649 



habitats and sites for California halibut and barred 

 sand bass. Subsets of these data (see above) were 

 used in these analyses. 



Kruskal-Wallis and Dunn multiple comparisons 

 were also made on the mean number of eelgrass 

 shoots and mean blade length per quadrat to deter- 

 mine differences in these eelgrass characteristics 

 among the three sites. Water temperature, dissolved 

 oxygen, and salinity values for each tow were used 

 in a two-way nonparametric ANOVA to test for dif- 

 ferences in each of these abiotic factors between habi- 

 tats and among sites. 



Results 



Eelgrass characteristics and abiotic factors 



Physical characteristics of eelgrass beds at the three 

 sites were very different. Belmont Shore had the long- 

 est bed but mean bed width, eelgrass shoot density, 

 and eelgrass blade length were lowest (Table 1 ). Eel- 

 grass densities at Bay Entrance and Marine Stadium 

 were significantly greater than at Belmont Shore 

 (P<0.05), and all blade length comparisons among 

 sites were significantly different (P<0.05). 



Abiotic factors varied temporally but showed little 

 spatial variation. Mean monthly values ranged from 

 14.5 to 23.0°C for water temperature, 4.8-8.1 mg/L 

 for dissolved oxygen, and 23.2-36.0 ppt for salinity. 

 These abiotic factors were very similar between habi- 

 tats and among sites except for slightly lower dis- 

 solved oxygen in eelgrass and higher water tempera- 

 tures at Marine Stadium. However, none of these 

 abiotic factors were significantly different between 

 habitats or among sites (P>0.05). 



Fish community 



A total of 52,787 fish representing 46 species was 

 collected from 435 tows (Table 2 ). The catch was domi- 



nated by a few species that were often captured in 

 large numbers. 



Numbers of species varied among habitats and 

 sites. Many more species were captured in eelgrass 

 beds (/?=42) than in unvegetated areas (72=26). We 

 collected 19 species exclusively in eelgrass beds but 

 captured only three species solely in unvegetated 

 areas (Table 2). Species numbers decreased as dis- 

 tance from the bay mouth increased; more species 

 were collected at Bay Entrance (n=40) than at 

 Belmont Shore in =35) and Marine Stadium (n=28). 



California halibut 



California halibut ranked eighth in abundance; 1 157 

 individuals were collected from 50. 89^ of the tows 

 (Table 2 ). The number of California halibut captured 

 per tow ranged from to 81 with a mean of 2.7 

 ± 0.32 SE. The abundance of newly settled Califor- 

 nia halibut was greatest from March through May 

 (Fig. 2). A total of 325 newly settled California hah- 

 but was captured. For all sites and habitats com- 

 bined, maximum mean density per month of newly 

 settled individuals was 15/100 m- (May 1995). Maxi- 

 mum mean density per month at an individual site 

 and habitat was 81/100 m- (May 1995, Bay Entrance 

 unvegetated area). 



California halibut abundance varied considerably 

 among habitats and sites (Fig. 3A). The magnitude 

 of these differences depended upon the habitat and 

 site as indicated by a significant interaction term in 

 the two-way ANOVA (P=0.002). Abundance was sig- 

 nificantly different between habitats at all three 

 sites, for all three site comparisons in unvegetated 

 areas, and for two of three comparisons in eelgrass 

 beds (Table 3). Within sites, Marine Stadium and 

 Belmont Shore unvegetated areas contained about 

 2-3 times as many California halibut as eelgrass 

 beds, and Bay Entrance unvegetated area had more 

 than six times as many California halibut as nearby 

 eelgrass (Fig. 3A). Within both habitats, California 



