Ross et al.: Fish species associated with shipwreck and natural hard-bottom habitats 
53 
were set apart from most other SS samples 
(Fig. 3). Fishes that occurred in deeper wa- 
ters (>90 m) that were missing from those 
3 middle shelf sites, regardless of habitat 
type, were the metallic codling (Physiculus 
fulvus), the big roughy ( Gephyroberyx dar- 
winii), the longspine snipefish (Macroram- 
phosus scolopax ), groupers ( Hyporthodus 
spp.), and the deepbody boarfish. Two spe- 
cies common on the middle shelf sites, the 
scup ( Stenotomus chrysops ) and the tautog 
( Tautoga onitis), were not observed on the 
deeper sites. 
Habitat preference also was indicated by 
relative abundance patterns of most benthic 
fishes. The hard bottom (AS/NHB) habitat 
type contained >89% of the abundance of 
each of 22 fish taxa (i.e., the first 22 species 
in Fig. 4), and far more individuals were ob- 
served overall in that habitat type than in 
the SS habitat type. Several species, includ- 
ing a searobin (Prionotus sp.), the fourspot 
flounder ( Paralichthys oblongus), the sum- 
mer flounder (P. dentatus ), and the scup, 
used both soft- and hard-bottom habitats 
frequently. A few taxa, including lefteye 
flounders (Bothidae), the margined snake 
eel ( Ophiclithus cruentifer), and the rosette 
skate (Leucoraja garmani), were observed 
only on soft bottom (Figs. 2F and 4). 
Habitat code 
▲ SS 
■ AS 
*NHB 
Similarity (%) 
40 
- 30 
Multidimensional scaling ordination of 26 video samples from habi- 
tats of artificial (shipwreck) substrata (AS), natural hard bottom 
(NHB), and soft substrata (SS), based on the Bray-Curtis similarity 
matrix calculated from standardized, fourth-root transformed fish 
abundances (41 taxa). Numbers by symbols are the dive numbers 
given to each dive of the remotely operated vehicles (see Table 1). 
Discussion 
Fishes that occupied natural and artificial hard-bottom 
habitats on the middle to outer shelf of the MAB ex- 
hibited an assemblage structure in our study that was 
different from that of the well-documented (e.g., Mu- 
rawski et al., 1983; Mahon et al., 1998) ichthyofauna 
of MAB soft-bottom habitats. Although the most abun- 
dant reef (i.e., hard-bottom) species also were observed 
and counted on soft-bottom habitat, in most cases they 
were never far from reef structures. The hard-bottom 
habitats surveyed in our study were dominated by cool- 
temperate and warm-temperate species that are gen- 
erally considered to be reef associates, although some 
(e.g., the chain dogfish, black sea bass, and conger eel) 
have broad depth and latitudinal distributions and 
large-scale habitat use. Other species common to the 
hard-bottom habitats (e.g., most Serranidae, the tau- 
tog, the blueline tilefish, and the deepbody boarfish) 
exhibited more restricted distributions and tighter as- 
sociation with reefs. Species of Serranidae (excluding 
the black sea bass) in particular seemed constrained 
to a relatively narrow depth range (from ~70 m to at 
least 150 m) in the MAB, most likely because of the 
generally warmer (>10°C) and less variable bottom wa- 
ter temperatures along the outer shelf of the southern 
MAB (Colvocoresses and Musick, 1984). 
In contrast to most of the fishes associated with 
soft-bottom habitats, several of the abundant hard- 
bottom species (Fig. 2, A-E; e.g., the yellowfin bass, the 
red barbier, groupers, and the blueline tilefish) were 
further constrained by being at or near the northern 
limits of their adult ranges (Moore et al., 2003; Ander- 
son and Heemstra, 2012). Because many of the common 
hard-bottom species (e.g., most of the Serranidae and 
the chain dogfish and deepbody boarfish) likely have 
an obligate association with reef-like habitats (Able 
and Flescher, 1991; Craig et al., 2011; Anderson and 
Heemstra, 2012), the relatively limited extent of hard 
bottom in the MAB (Steimle and Zetlin, 2000) would 
also affect their distribution. Therefore, an abundant 
component of the hard-bottom fish community in the 
southern MAB is restricted by habitat availability, 
depth, and zoogeography, of which the latter 2 con- 
straints probably are related to bottom temperature. 
Although this reef community of the outer shelf ap- 
pears to flourish, these limitations likely make it vul- 
nerable to overfishing, habitat damage, and large-scale 
environmental variations. 
Results presented here differ substantially from 
those of other surveys of the MAB. Our ROV study 
sites overlapped with some of the areas of fish group- 
ings that were based on decades of bottom trawl sur- 
veys (Colvocoresses and Musick, 1984; Mahon et al., 
1998); however, the majority of species common to this 
study and these 2 trawl-based studies were species 
that are reported to be most common on sandy bottoms 
