466 
Day and night abundance, distribution, 
and activity patterns of demersal fishes 
on Heceta Bank, Oregon 
Ted D. Hart' 
Julia E. R. Clemons (contact author ) 2 
W. Waldo Wakefield 2 
Selina S. Heppell' 
Email address for contact author: Julia.Clemons@noaa.gov 
1 Oregon State University 
Department of Fisheries and Wildlife 
104 Nash Hall 
Corvallis, Oregon 97331 
Present address for Ted D. Hart: Environmental Science and Management 
Portland State University 
1719 SW 10th Avenue, SB2 Room 218 
Portland, Oregon 97201 
2 Northwest Fisheries Science Center 
Fishery Resource Analysis and Monitoring Division 
National Marine Fisheries Service 
National Oceanic and Atmospheric Administration 
2032 SE OSU Drive 
Newport, Oregon 97365 
Abstract — Most shallow-dwelling 
tropical marine fishes exhibit differ- 
ent activity patterns during the day 
and night but show similar transition 
behavior among habitat sites despite 
the dissimilar assemblages of the 
species. However, changes in species 
abundance, distribution, and activ- 
ity patterns have only rarely been 
examined in temperate deepwater 
habitats during the day and night, 
where day-to-night differences in light 
intensity are extremely slight. Direct- 
observation surveys were conducted 
over several depths and habitat types 
on Heceta Bank, the largest rocky 
bank off the Oregon coast. Day and 
night fish community composition, 
relative density, and activity levels 
were compared by using videotape 
footage from a remotely operated 
vehicle (ROV) operated along paired 
transects. Habitat-specific abundance 
and activity were determined for 31 
taxa or groups. General patterns 
observed were similar to shallow 
temperate day and night studies, 
with an overall increase in the abun- 
dance and activity of fishes during 
the day than at night, particularly 
in shallower cobble, boulder, and 
rock ridge habitats. Smaller school- 
ing rockfishes ( Sebastes spp.) were 
more abundant and active in day 
than in night transects, and sharp- 
chin (S. zacentrus ) and harlequin (S. 
variegatus) rockfish were significantly 
more abundant in night transects. 
Most taxa, however, did not exhibit 
distinct diurnal or nocturnal activ- 
ity patterns. Rosethorn rockfish (S. 
helvomaculatus) and hagfishes (Epta- 
tretus spp.) showed the clearest diur- 
nal and nocturnal activity patterns, 
respectively. Because day and night 
distributions and activity patterns in 
demersal fishes are likely to influence 
both catchability and observability in 
bottom trawl and direct-count in situ 
surveys, the patterns observed in the 
current study should be considered 
for survey design and interpretation. 
Manuscript submitted 30 September 2009. 
Manuscript accepted 24 August 2010. 
Fish. Bull. 108:466-477 (2010). 
The views and opinions expressed 
or implied in this article are those 
of the author (or authors) and do not 
necessarily reflect the position 
of the National Marine Fisheries 
Service, NOAA. 
For surveys of groundfish, swept-area 
trawls are generally conducted and 
direct-counts from video cameras 
are recorded during daylight hours 
(Gunderson, 1993; Adams et al., 1995; 
Yoklavich et al., 2000; Wakefield et 
al., 2005). If activity patterns vary 
among species during the day versus 
the night, conclusions about rela- 
tive abundance, community composi- 
tion, and habitat affiliations could be 
incomplete or biased. It is not known 
whether diel activity and abundance 
patterns in fishes commonly found 
in shallow temperate and tropical 
areas are similar for fishes inhabit- 
ing deeper temperate areas along the 
west coast of North America, where 
diel changes in light levels are subtle. 
We used a repeat-transect (the tran- 
sect was followed once during the day 
and again at night) visual sampling 
survey to examine differences in fish 
abundance, distribution, and behavior 
on Heceta Bank, a temperate reef and 
ridge ecosystem off the central coast 
of Oregon. 
Diel distributions and activity pat- 
terns in fishes have been well studied 
in tropical areas, and these studies 
have shown that most fishes exhibit 
distinct diel behavioral patterns (Col- 
lette and Talbot, 1972; Hobson, 1972; 
Helfman, 1978). Generally, two-thirds 
of fishes are diurnal, one-third are 
nocturnal, and a marked change in 
the vertical distribution of fishes oc- 
curs between day and night (Helfman, 
1978). Most fishes rigidly follow a di- 
urnal or nocturnal activity pattern, 
exhibiting very low activity in shel- 
ter-providing areas and high activ- 
ity during feeding. Rotation between 
ecological niches at daytime and at 
night, such as the broad replacement 
of diurnal planktivores with preda- 
tors during the night, proceeds in 
predictable patterns (Hobson, 1972). 
Some of the largest schools encoun- 
tered by day in tropical waters are 
nonfeeding, resting schools of noctur- 
nal fishes, and many diurnal fishes 
actively school in the water column 
by day and then rest individually at 
night (Hobson and Chess, 1973; Par- 
rish, 1992). 
Although not as well studied, diel 
shifts in fish communities and be- 
havioral patterns in shallow temper- 
ate habitats are less distinct than 
