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



173 



by the characteristic presence of Pleuronecti- 

 formes and Agonidae. 



Intermediate- and fine-scale 

 fish-habitat associations 



At the level of the individual fish species, a 

 range of benthic habitat variables and spatial 

 scales were important in explaining species-spe- 

 cific distributions. Intermediate-scale informa- 

 tion on patch use, patch selectivity, along with 

 fine-scale microhabitat use, revealed four types 

 of species-specific groups (Fig. 5-8). 



The first group, rock and boulder associates 

 (e.g., S. hopkinsi, S. flavidus, and S. paucispi- 

 nis) were species that at the intermediate-scale 

 were strongly associated with patches of rock 

 or boulders (or both) (Fig. 5). At the fine-scale, 

 these three species were found on or above rocks 

 (69%, 76%, and 30%, respectively) or boulders 

 (28%f , 24%, and 18%, respectively); S. paucispi- 

 nis also used mud microhabitats (52%). 



The second group, generalists (e.g., S. wilsoni, 

 S. rosaceus, and O. elongatus) were species that 

 at the intermediate-scale were associated with 

 a variety of patch types (Fig. 6). However, when 

 standardized by habitat availability, these spe- 

 cies were strongly associated with patches of 

 boulders, cobbles, and to a lesser extent, rock, 

 and were negatively associated with patches 

 of homogeneous mud. At the fine-scale, these 

 species were also found on or above all possible 

 microhabitat types and showed a flexibility in 

 habitat use at all three spatial scales. Onto- 

 genetic shifts in habitat use also were indi- 

 cated. For example, small O. elongatus, (<25 

 cm; «=54) were more abundant in patches with 

 mud or cobbles (e.g., 74% in mud-mud [MM], cobble- 

 boulder [CB], and mud-cobble [MC]), whereas medium- 

 size O. elongatus (25-50 cm; 7) = 57) were found more fre- 

 quently in patches with boulders (40%) and rock (32%). 

 Larger individuals (>50 cm; n=&), on the other hand, 

 were found in patches of rock (83%), indicating that O. 

 elongatus move from mixed mud and cobble habitats to 

 more complex rocky outcrops as they grow. 



The third group, cobble-mud associates (e.g., S. semi- 

 cinctus, S. chlorostictus, and S. elongatus) were species 

 that at the intermediate-scale were found in patches 

 containing various mixtures of cobbles, mud, and to 

 a lesser extent, boulders (Fig. 7). At the fine-scale, 

 these species were found over mud (66%, 54%, and 

 81%, respectively) or low-relief cobbles and boulders 

 (pooled 33%, 47%, and 16%, respectively) indicating 

 that mud habitats adjacent to or within mixed cobble- 

 mud areas had inherent properties above either habitat 

 in isolation. 



Finally, the fourth group, soft-sediment associates 

 (e.g., Pleuronectiformes, Agonidae, Citharichthys spp., 

 and R. nicholsii) were species that at the intermediate- 

 scale were strongly associated with patches containing 



1.0 



0.5  



-0.5 



-1.0 



Sand / . 



J //" 



y nibrivincti 



Cobbles 



Z rosiici'us 



Cilharichtlixs spp 

 S seiniciiicnis 



•JPatch number ^ wiho 



thliTi 

 Z/m;t(/i/l\ 



Relief 



S rosaceus 



YOY Rock^^,,,,,,.^,^^. 

 /™{<.m/ Boulders 



nicholsii 



S hopkinsi 

 tus 



S. puucispinis 



A sicilis 



/ 



Ziiiiiolcpis spp Z latipinnis^ 

 S elongatus/.- 



Musi- \ 



/ Agonidae \ 



Agonidae 



Pleuronectiformes 



4  



Mud Depth 



-1.0 



-0.5 0.0 



Canonical variate 1 (54.5°' 



0.5 



1.0 



Figure 4 



Broad-scale associations of the demersal fish assemblages with 

 benthic habitat variables as discerned from canonical correla- 

 tion analysis. Circles depict the three broad-scale strata (dark 

 gray=hard, white = mixed, light gray=soft sediment), and are 

 presented to assist in the visual association of species and ben- 

 thic habitat variables. Vectors are the eigenvectors of the benthic 

 habitat variables. YOY = young-of-year Sebastes spp., "Stomus" = 

 Sebastomus spp.; S = Sebastes; R = Rhinogobius; O = Ophiodon; 

 Z = Zaniolepis: and A = Argentina. 



mud or sand (Fig. 8). Pleuronectiformes, Agonidae, and 

 Citharichthys spp. were all associated with homoge- 

 neous soft sediments at all spatial scales (Fig. 8, A-C). 

 In contrast, R. nicholsii were found in a range of soft- 

 sediment patch types (e.g., sand-boulder [SB], sand- 

 sand [SS], mud-rock [MR], mud-boulder [MB], etc.) and 

 microhabitats. However, homogeneous soft-sediment 

 areas had few or no R. nicholsii (Fig. 8D), indicating 

 that, for this species, sediment gaps within a rocky 

 outcrop matrix had inherent properties above either 

 rock or sediment habitats in isolation. 



Discussion 



The composition, complexity, and configuration of the 

 seafloor at multiple scales allowed us to predict assem- 

 blage structure and species distributions across the 

 continental shelf within southern Monterey Bay. Broad- 

 scale habitat strata, which are routinely mapped by 

 acoustic methods, showed clear distinctions in assem- 

 blage structure. Hard stratum, composed of high-relief 

 outcrops, was occupied by a diverse range of demer- 



