Hart et al.: Abundance, distribution, and activity patterns of demersal fishes on Hecate Bank, Oregon 
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Figure 4 
Nonmetric multidimensional scaling (NMS) ordination showing association between 11 taxa and habitat patches 
(different symbols) from all stations (2, 3, 4, 6, and 9). Taxa codes are: HF (hagfishes, Eptatretus spp.), HR 
(harlequin rockfish, S’. variegatus), KG (kelp greenling, Hexagrammos decagrammus), PR (pygmy rockfish, S. 
wilsoni), PRC (pygmy-Puget Sound complex, S’. wilsoni and S. emphaeus), PSR (Puget Sound rockfish, S. empha- 
eus), RA (spotted ratfish, Hydrolagus colliei), RS (rex sole, Glyptocephalus zachirus), RT (rosethorn rockfish, S. 
helvomaculatus), RRF (unidentified juvenile rockfish, Sebastes spp.), and SH (sharpchin rockfish, S. zacentrus ). 
Environmental variables include the quantitative variable of depth (increasing depth from top to bottom), and 
the categorical variables (shape of symbols) of day, night, and habitat. 
When compared to the dominant day assemblage, 
the night assemblage exhibited lower overall densities 
and consisted of less active, larger-size fish of fewer 
taxa, many of which were also seen during the daylight 
hours (Tables 1 and 2, Fig. 3). Dominant night taxa 
were sharpchin rockfish, yellowtail rockfish, Dover sole 
(Microstomus pacificus), and greenstriped rockfish (S. 
elongatus). Of the dominant night assemblage, sharp- 
chin rockfish comprised over half of the fish encoun- 
tered at night (Fig. 3) and was one of the only taxa 
that showed significantly greater abundance during the 
night (P<0.05) in most primary habitat types (Table 1). 
Hagfishes and spotted ratfish were significantly greater 
in abundance and activity during the night (P<0.05), 
and widow rockfish showed significantly greater activity 
during the night (P<0.05), despite being rarely observed 
(Table 2). Hagfishes were the only taxa that exhibited 
a distinct nocturnal activity pattern (P<0.05). 
Discussion 
The relative composition of fish taxa over all depths 
and habitat types on Heceta Bank did not show a broad 
replacement from day to night, as observed in shallow 
tropical areas. However, there were consistent patterns 
of abundance and activity that were species-, depth-, 
and habitat-specific. There was a considerable day- 
night change in the abundance of the four most domi- 
nant day taxa (pygmy rockfish, Puget Sound rockfish, 
pygmy-Puget Sound rockfish complex, and unidentified 
juvenile rockfish) over shallower areas of rock ridge 
and boulder habitat. Active, small- to medium-size fish 
taxa tended to aggregate around shallow medium- to 
large-size habitat features during the day, and larger- 
size night taxa (sharpchin rockfish, yellowtail rockfish, 
Dover sole, and greenstriped rockfish) tended to aggre- 
gate around these features at night. Rosethorn rockfish 
