Anderson and Yoklavlch: Habitat association of deepwater demersal fishes off central California 



175 



Patcfi use 



800 

 600 

 400 

 200 

 



^ 50 



+ 



e 40 



^ 30 



r 20 



o 



E 



i 



Patcfi selectivity Microtiabitat 



use 



A S. wilsoni 



1" Substratum 



kXxjj Boulders 

 EI] Cobbles 



Sand 



Mud 



Bs 



C O. elongatus 



100% 



50% 



0% 

 100% 



50% 



0% 

 100% 



50% 



0% 



B C S 



Patcfi type 



-40-20 20 40 



Selectivity index 



Figure 6 



Intermediate and fine-scale habitat use by species that are habitat general- 

 ists: (A) pygmy rockfish iSehastes wilsoni), (B) rosy rockfish (S. rosaceus), and 

 iC) lingcod (O. elongates). Symbols and interpretation are given in Figure 5. 



off central California. Jagielo et al. (2003) compared 

 trawlable and untrawlable habitats off Washington and 

 found rockfishes iSebastes helvomaculatus [rosethorn 

 rockfish], S. rubberimus, S. flavidus, Sebastes nigro- 

 cinctus [tiger rockfish], and Sebastes spp.) were three 

 times more abundant in untrawlable habitats. In more 

 complex habitat systems. Stein et al. (1992) found high 

 densities of juvenile Sebastes spp. and S. flavidus on 

 the tops of high-relief rocky pinnacles on Heceta Bank, 

 Oregon, whereas in the Gulf of Alaska, O'Connell and 

 Carlile (1993) found the commercially important S. rub- 

 berimus in highest densities in complex habitats. 



Mixed stratum, characterized by lower complexity 

 and relief than areas of hard stratum, also comprised a 

 distinctive demersal fish assemblage with high numbers 

 of species. High diversity in these areas resulted from 

 a combination of species unique to the mixed stratum 

 (e.g., S. semicinctus), and species characteristic of both 

 hard (e.g., S. wilsoni, O. elongatus, S. rosaceus) and 



soft (e.g., Pleuronectiformes and Agonidae) strata. In 

 addition to high diversity, some species (e.g., S. chlo- 

 rostictus, S. elongatus, and Z. frenata) were also more 

 abundant in the mixed stratum, indicating that some 

 inherent property of heterogeneous habitats (e.g., mul- 

 tiple resource needs, higher levels of habitat fragmen- 

 tation, and interface zones) may be important to these 

 species. Similar findings have been reported in other 

 submersible surveys. Stein et al. (1992), for example, 

 found more species and higher densities of these species 

 (e.g., S. chlorostictus, S. wilsoni) in patches with either 

 "mud and boulder" or "mud and cobble" than in patches 

 with mud, boulders, or cobbles in isolation. Species use 

 of interface regions can also be inferred from previous 

 studies even though habitat use at the microscale was 

 not explicitly measured. For example, both Richards 

 (1986) and Pearcy et al. (1989) reported higher num- 

 bers of S. elongatus in soft sediment areas adjacent 

 to rocks. Similarly, Yoklavich et al. (2002) found that 



