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Journal of Marine Systems 50 (2004) 21 – 37
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Biological and physical processes in and around Astoria
submarine Canyon, Oregon, USA
Keith L. Bosley a,*, J. William Lavelle b, Richard D. Brodeur c, W. Waldo Wakefield a,
Robert L. Emmett c, Edward T. Baker b, Kara M. Rehmke d
a
NOAA Fisheries, Northwest Fisheries Science Center, Fishery Resource Analysis and Monitoring Division,
Hatfield Marine Science Center, 2032 S.E. OSU Drive, Newport, OR 97365, USA
b
NOAA Pacific Marine Environmental Laboratory, OAR 7600 Sand Point Way NE, Seattle, WA 98115-6349, USA
c
NOAA Fisheries, Northwest Fisheries Science Center, Fish Ecology Division, Hatfield Marine Science Center, 2030 S.E. OSU Drive,
Newport, OR 97365, USA
d
Oregon State University, Hatfield Marine Science Center, 2030 S.E. OSU Drive, Newport, OR 97365, USA
Received 13 February 2003; accepted 10 June 2003
Available online 21 July 2004
Abstract
Astoria Canyon represents the westernmost portion of the Columbia River drainage system, with the head of the canyon
beginning just 16 km west of the mouth of the Columbia River along the northern Oregon and southern Washington coasts.
During the summer of 2001, physical, chemical, and biological measurements in the canyon were taken to better understand the
hydrodynamic setting of, and the feeding relationships among, the pelagic and benthic communities. Results show that currents
were strongly tidal, and transport, where measured, was primarily up and into the canyon below shelf depth as previous studies
in the canyon have shown. Temperature time series suggests that the largest diurnal oscillations occurred at, or were trapped
near, the bottom of the canyon. Within the upper canyon, subtidal temperature was correlated with upper-level shelf-edge
currents, linking subtidal upwelling events in the canyon with near-surface subtidal along-shore flow. Invertebrates, such as
shrimp, euphausiids, and squid, as well as mesopelagic fishes, dominated the Isaacs – Kidd midwater trawl catches along the
canyon walls. Large trawl catches were comprised mainly of hake and rockfishes (shallow trawls) and macrourids, scorpaenids,
stomiids, and zoarcids (bottom trawls). Gut-content analysis of rockfishes and lanternfishes revealed substantial use of
midwater prey such as euphausiids and mesopelagic fishes. The d13C values of fishes and invertebrates reflected local primary
production, as indicated by particulate organic matter (POM) d13C values from samples collected at various depths along the
axis of the canyon, as well as across the canyon at several sites. The d15N values of fishes and invertebrates indicated
lanternfishes, along with euphausiids, amphipods, shrimp and squid, may be important dietary components of higher-trophiclevel fishes in both the benthic and benthopelagic food webs. The d13C and d15N values of Sebastes species showed significant
enrichment in the adults of species that are largely piscivorous relative to the values of adults of more omnivorous species.
D 2004 Elsevier B.V. All rights reserved.
Keywords: Submarine canyons; Astoria canyon; Currents; Zooplankton; Micronekton; Fish; Stable isotopes
* Corresponding author. Tel.: +1-541-867-0506; fax: +1-541-867-0505.
E-mail address: [email protected] (K.L. Bosley).
0924-7963/$ - see front matter D 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jmarsys.2003.06.006
22
K.L. Bosley et al. / Journal of Marine Systems 50 (2004) 21–37
1. Introduction
Canyons represent just one type of abrupt topography in which enhanced productivity is often found.
Factors that lead to enhanced productivity in canyons
are the regional and local topography, the regional
and local nutrient supply, vertical migration habits of
species, and the ocean currents within and above the
canyon. Genin (2004) has reviewed the biophysical
mechanisms by which fishes and their prey resources
become aggregated near abrupt topography. These
include funneling and trapping of plankton (Koslow
and Ota, 1981; Greene et al., 1988; Macquart-Moulin and Patriti, 1996) and counter-upwelling depth
retention (Allen et al., 2001). The topographic complexity of canyons, the time-varying nature of flow
and forcing, and the difficulty in sampling behaviorally dynamic biological populations in physically
dynamic environments, however, make fully unraveling trophic pathways in these environments a
challenge.
Compared to neighboring shelf and slope regions,
submarine canyons exhibit intensified flow and turbulence. Wind-driven, pressure-driven, and tidal
flows dominate motion (e.g., Hickey et al., 1986;
Hunkins, 1988; Noble and Butman, 1989; Lafuente
et al., 1999). Focusing of flow by canyon topography
makes canyons a major site in cross-slope/cross-shelf
exchange (e.g., Hickey, 1997). Freeland and Denman
(1982), noting the persistent pool of nutrients on the
shelf at the head of the Juan de Fuca Canyon in the
Northeast Pacific Ocean, recognized that canyons
may serve as conduits of deep nutrients to shelf
water (see also Sobarzo et al., 2001). Internal tide
focusing and breaking in canyons (Gardner, 1989)
can lead to intensified mixing near canyon bottoms
(Lueck and Osborn, 1985; Carter and Gregg, 2002;
Kunze et al., 2002; Petruncio et al., 1998). Increased
turbulence in the bottom f 100 m leads to resuspension, a slowing of the deposition of particulate
matter descending from the euphotic zone, and to
higher levels of particulates and nutrients in the
water column within the canyon. Density-driven,
down-canyon flows are also not uncommon and they
can temporarily change habitats along a canyon floor
by scouring the seafloor, by increasing turbidity, and
through sediment deposition (Kampf and Fohrmann,
2000).
Astoria Canyon, along the west coast of North
America and just beyond the mouth of the Columbia River, is considered to be a steep and narrow
canyon (Hickey, 1997). Flow is marked by spatial
variability at length scales of a few kilometers or
less; diurnal and semi-diurnal tidal motions account
for much of the variance (Hickey, 1997). This
results in suspended matter fields that are marked
by considerable temporal variability (Plank et al.,
1974).
During times of maximum upwelling (southward
along-shore near surface flow), flow across the entire
width of the canyon is landward, but prior to and after
maximum upwelling, canyon flow is marked by
strong lateral shear (Hickey, 1997). A cyclonic vortex
at the head of canyons is typical of flow during such
times (Allen, 1996; Hickey, 1997; She and Klink,
2000) and, in the case of Astoria Canyon, it extends as
much as 50 m above canyon rim depth. Water
properties are domed upward at the head of some
canyons (Hickey, 1995) in response to upwelling. In
Astoria Canyon, shelf flows crossing the canyon in
the near surface (0 –100 m) are not deflected (Hickey,
1997).
Stable-isotope ratios present a useful tool for
studying the processes, connections, and energy flow
within aquatic ecosystems (see reviews by Fry and
Sherr, 1984; Owens, 1987; Peterson and Fry, 1987).
Two elements, carbon and nitrogen, are particularly
useful as natural tracers of both the flow of organic
matter and food-web structures in marine ecosystems.
It is possible to obtain time-integrated descriptions of
diets, sources of prey, and the trophic status of a fish
by quantifying the ratios of 15N/14N and 13C/12C. The
carbon sources in a geographic area can be distinguished isotopically because the relative amount of
13
C in the tissues of primary producers varies depending on the mechanism of carbon fixation and often
varies substantially between habitats that are dominated by different types of primary producers (Fry and
Sherr, 1984). The trophic level of a secondary consumer can be inferred because heavier isotopes, especially 15N, are retained in the tissues of a consumer in
increasing amounts relative to the amount of heavier
isotopes found in its diet, a process referred to as
fractionation (DeNiro and Epstein, 1981). A onetrophic-level difference in nitrogen stable isotope
levels is generally considered to be 3.0 to 3.5 per
K.L. Bosley et al. / Journal of Marine Systems 50 (2004) 21–37
mil (x) (DeNiro and Epstein, 1981). That is, if a
primary producer had a value of 0x, a primary
consumer that feeds on it should have a value of
3.0x to 3.5x. A secondary consumer feeding on the
primary consumer would be expected to have a value
of 6.0x to 7.0x, and so on.
Hill and Wheeler (2002) examined organic carbon
and nitrogen in surface waters off of Oregon and
Washington to characterize three distinct water sources: oligotrophic offshore water, the Columbia River
plume, and the coastal upwelling region. They found
that the river plume had the highest levels of both
total and dissolved organic carbon. Previous studies
have shown that potential sources of carbon in marine
and coastal ecosystems will have different d13C
signatures, and they used the carbon isotopic composition of suspended particulate organic matter (POM)
and sediments as a means of calculating the amount
of terrestrial carbon that is contributed to freshwater
and marine systems (Fry and Sherr, 1984). A prerequisite for using isotope ratios as tracers in food webs
is a detectable and consistent difference in the isotopic signature between its components. In areas of the
oceans where there are different sources of primary
production, along with diverse assemblages of consumers, such as along a continental shelf or slope,
stable isotopes can be used in conjunction with
traditional methods (i.e. stomach content analysis) to
study feeding relationships and the relative contributions of different primary producers (Perry et al.,
1999; Polunin et al., 2001; Davenport and Bax,
2002).
Astoria Canyon is a highly productive fishery
region. The canyon is home for many pelagic fish
species, and many years of surveys have found
extensive groundfish resources there as well. Despite
the importance of its fisheries resources, we know
little about the pathways leading from primary
nutrients to higher trophic levels in Astoria Canyon.
To date, the only study of the food habits of fishes in
Astoria Canyon was that of Pereyra et al. (1969),
which examined the feeding ecology of adult yellowtail rockfish that utilized mesopelagic prey resources.
In this work, we report on biological, chemical, and
physical measurements taken in Astoria Canyon
aimed at further elucidating feeding relationships
and the physical environment in which these trophic
transfers occur.
23
2. Materials and methods
2.1. Study area
This study was conducted during a NOAA Ocean
Exploration cruise aboard the R/V Ronald H. Brown
from June 27 through July 3, 2001 in Astoria Canyon.
The head of the canyon begins at a bottom depth of
120 m just 16 km west of the present river mouth (Fig.
1). The axis of the canyon extends from well within
the continental shelf zone, west-southwest for approximately 110 km, where, at a bottom depth of more
than 2000 m, it transitions into a deep-sea channel.
The width of the canyon ranges from 9 km where it
cuts across the shelf to 70 km where it transitions into
Astoria Channel (Carlson, 1968). Astoria Canyon is
the southern-most submarine canyon of a series of
canyons that bisect the continental margin of the
Pacific Northwest off British Columbia and Washington. Rogue Canyon, far to the south, is the only other
significant canyon feature on the Oregon margin
(Underwood, 1991). Astoria Canyon lies within a
major upwelling region and underlies the Columbia
River Plume, a major hydrographic feature along the
coasts of Oregon and Washington (Hickey, 1989). Our
study was confined to the eastern portion of the
canyon.
2.2. Physical measurements
Two taut-wire moorings were deployed in the
canyon on June 29 to measure currents and temperatures. The moorings collected data during the intensive 1-week biological sampling period (June 27 – July
3) and remained in the canyon through August 2 in
order to sample during one entire lunar cycle. The
Aanderaa RCM-7 current meters recorded speed,
averaged over the sampling interval, and instantaneous direction half-hourly. Moorings M-118 and
M-119 were located at 46j13.8VN, 124j27.0VW and
46j11.0VN, 124j39.40VW, respectively. M-118, in
337-m water depth, recorded currents at a depth of
275 m, and M-119 recorded currents at 50, 275, and
325 m in 400-m water depth. M-118 was located
nearer the head of the canyon, and M-119 was located
where the canyon and upper slope intersect (Fig. 1).
Temperatures were recorded using Miniature Temperature Recorders (MTR) and Miniature Autonomous
24
K.L. Bosley et al. / Journal of Marine Systems 50 (2004) 21–37
Fig. 1. Sampling locations in Astoria Canyon. The CTD stations are indicated by single upper-case letters/open circles; the IKMT trawl sites
begin with the letter ‘‘I’’/solid star; the Sea Eagle trawl sites begin with the letter ‘‘R’’/solid triangle (midwater rope trawl) or ‘‘B’’/open square
(bottom trawl); and the mooring locations begin with the letter ‘‘M’’/solid square. Bathymetry is adapted from NOAA National Ocean Survey
Seamap Series for the North Pacific Ocean, no. 12042-12B. Depth contours are in meters. Only the 150-, 1000-, and 2000-m contours are
featured on the inset map to show the relative position of the shelf break.
Plume Recorders (MAPR) (Baker and Milburn,
1997). On M-118, temperatures were sampled halfhourly at depths of 60, 100, 125, 160, 200, 250, 290,
and 340 m, and on M-119, at depths of 100, 150, 190,
and 270 m. Wind speed and direction 5 m above sea
level were sampled hourly from Buoy 46029 by the
NOAA National Data Buoy Center. Buoy 46029 at
46j07V00U N and 124j30V36U W in 128 m of water is
located 13 km SSW of M-118 and 13 km ESE of M119. The buoy’s location makes its measured winds
representative of those over the canyon (Fig. 1).
Spectral analysis of time series involved removing
the mean and a linear trend from each time series,
cosine tapering 10% of both ends of the resulting
record, Fourier analyzing, and then band smoothing
the resulting periodograms using a Hanning spectral
window with an 11-point width (e.g. Emery and
Thomson, 1997).
CTD casts were made at several stations across the
canyon and along its axis from the R/V Brown. A CTD
rosette containing multiple Niskin bottles was lowered
at each station and water samples were collected from
just below the sea surface, from the midwater (based
on station depth) and from just above the sea floor.
Replicate water samples were first filtered through 28Am mesh to remove larger particulates and then
through Whatman GF/F filters to collect particulate
organic matter (POM). The filters were frozen for
further processing on land for isotopic analysis (see
below).
2.3. Biological sampling
Most of the biological samples and data were
collected from the R/V Brown. Multi-frequency acoustic data were collected from continuous transects
across the canyon using an EK-500 echosounder
receiving data from 38-, 120-, and 200-kHz transducers. Complete analyses of these acoustic data are
beyond the scope of this paper and will be presented
elsewhere. The acoustics were employed to target
midwater and bottom trawling on particular signals
and acoustic layers. Three horizontal tows for micronekton were made with an IKMT (Isaacs –Kidd midwater trawl) with a mouth area of 5.4 m2. The main
body of the net was comprised of 10-mm stretch
K.L. Bosley et al. / Journal of Marine Systems 50 (2004) 21–37
mesh, with 500-Am mesh in the codend. A large V-fin
depressor situated at the front of the net increased the
sampling depth for the given amount of wire out. A
calibrated General Oceanicsk flow meter suspended
in the mouth of the net provided data on the amount of
water filtered by the trawl. The depth of each tow was
determined using a MAPR device. All fishes and
invertebrates caught were identified by species and
weighed in the laboratory to determine biomass.
Selected species from these tows had white muscle
tissue dissected for stable-isotope analysis and stomachs dissected for content analysis and were handled
as described above. Whole invertebrates also were
frozen for further processing and isotopic analysis.
Some biological sampling was carried out from a
commercial fishing vessel, the F/V Sea Eagle, during
the same time period. Fishes and invertebrates were
collected from the Sea Eagle using a bottom trawl that
featured a ‘‘rock hopper’’ footrope (number of
tows = 2) and using a Nordic 264 rope trawl (n = 7)
to assess species diversity and abundance around the
canyon. Fish that were collected in the trawls were
sorted by species and then weighed, measured, and
counted. Selected species had white muscle tissue
dissected for stable-isotope analysis and stomachs
dissected for content analysis. The muscle tissue
was dissected from just below the dorsal spines or
fins of each fish and then frozen. The stomachs were
preserved in 10% formalin. Whole invertebrates also
were sorted by species, and selected animals were
frozen for further processing and isotopic analysis.
2.4. Laboratory analyses
Prior to analysis, muscle-tissue samples were first
thawed and then dried completely at 55 jC. The
samples were ground using a Wig-L-Bugk (Dentsply) automated mortar and pestle and then loaded into
tin capsules. Filter samples also were thawed and
dried completely at 55 jC and then acidified with 1
N HCl to remove any inorganic carbon. The stableisotope analysis was carried out using a Costech
elemental analyzer coupled to a Thermo Finnegan
stable-isotope-ratio mass spectrometer in the continuous-flow mode, with ultra-high-purity helium as the
carrier gas. The stable-isotope ratios (15N/14N and
13 12
C/ C) were reported as d15N and d13C, with units
of per mil (x) difference relative to standards; N2 in
25
air for nitrogen and PDB (Peedee belemnite) (Craig,
1957) for carbon. Lipids are depleted in 13C relative to
other biochemical fractions (DeNiro and Epstein,
1977, 1978; Tieszen et al., 1983). Since lipids were
not removed prior to the analysis of muscle-tissue
samples, final fish and invertebrate d13C values were
normalized (McConnaughey and McRoy, 1979) to
account for the depletion effect of lipids.
3. Results
3.1. Physical environment of the canyon
Surface winds measured south of the canyon had a
vector-averaged speed of 3.4 m s 1 and direction of
149j (Fig. 2A), typical of southward winds along the
Oregon coast during spring and summer (Hickey,
1997). The spectra of wind over the interval June –
August 2001 exhibited both diurnal and semidiurnal
peaks.
Currents measured at 50-m depth on M-119 (Fig.
2C) showed a strong vector-averaged flow of 16.4 cm
s 1 to the south (181j), with no indication of flow
reversal. Spectra analysis of the record confirmed a
strong semi-diurnal, nearly linear, oscillatory component, a substantial inertial frequency signal, but a very
weak diurnal oscillation. Currents at 225 m (Fig. 2D)
and 325 m (not shown) at M-119 flowed primarily to
the NNE (24j and 17.6j, respectively) along the trend
of the slope isobaths at vector-averaged speeds of 6.8
and 3.6 cm s 1, possibly showing evidence of the
influence of the California undercurrent.
Currents in the upper canyon (M-118) at 225-m
depth (Fig. 2B) were weaker (mean speed = 0.8 cm
s 1) and more variable in direction, with the overall
vector-averaged direction of 96j in the direction of
the canyon wall. Spectra of data from the three deepest meters showed almost no inertial oscillation, a
strong rectilinear semi-diurnal signal, and strong diurnal signals as well. Diurnal motions, which were
clearly intensified by the canyon topography, were
rectilinear at 225 and 275 m but nearly circular at the
325-m deep site (not shown).
Temperatures (T) recorded at M-118 (Fig. 3A)
showed substantial temporal variability and sizeable
vertical gradients. Between 50 and 325 m, the temporal
mean of T differed by 1.5 jC (Fig. 3B), roughly
26
K.L. Bosley et al. / Journal of Marine Systems 50 (2004) 21–37
Fig. 2. Vector time series of (A) winds measured offshore, just south of Astoria Canyon (46j07V, 124j30.6VW); (B) currents in the upper part of
the canyon at M-118 and 275-m depth; (C) currents in the upper water column (50-m depth) over the canyon but farther offshore at M-119; (D)
currents at M-119 but below shelf depth (225 m).
equivalent to the magnitude of the temporal variance
around that mean at each depth. The sequence of
spectra (Fig. 3C) showed a semi-diurnal signal at all
depths, and a diurnal signal that was very weak at the
upper meters but intensified below shelf depth in the
canyon.
Tidal oscillations in T recorded at 200-m depth on
the upper canyon mooring (M-118) were made more
clearly visible in Fig. 4 (solid line). Tidal oscillations
in the north – south component of currents measured in
the near surface waters (50m depth) at mooring M-
119, nearer the canyon mouth, were even more
apparent (dotted line).
CTD observations showed high spatial (vertical
and horizontal) and temporal variability in both the
hydrography and turbidity of the canyon waters. In
the upper canyon, a broad layer of intense light
scattering was common between 200- and 300-m
depth, likely a remnant of resuspension and advection
of adjacent shelf sediments. Just above the canyon
floor, a 50-m-thick layer of sharply increased light
scattering, lower temperature, and increased salinity
K.L. Bosley et al. / Journal of Marine Systems 50 (2004) 21–37
27
Fig. 3. (A) Eight time series of temperatures (T) recorded at M-118 at depths (starting with the uppermost series) of 60, 100, 125, 160, 200, 250,
290, and 340 m. (B) Profiles of temperature representing the mean, maximum, and minimum T from each of the time series. (C) Spectra of time
series each successively offset by one unit on the y-axis. The lowest curve (not offset) represents data from 60-m depth.
suggest up-canyon flow vigorous enough to create a
thick layer of resuspended bottom sediments. Lightscattering values in this layer increased with decreasing canyon depth. Even in the upper canyon, vertical
stratification was sufficient to maintain pronounced
layering of the fine-grained suspended particulate
matter.
The vertical and horizontal variability was not as
evident in the d13C data from the POM that was
collected, but there were some measurable differences
(Table 1). Overall though, the POM data varied little
between the stations around the canyon, regardless of
depth. The mean d13C was 23.82x with a standard
deviation (S.D.) of 1.10x (n = 22). The station with
the greatest d13C variability between surface and
bottom POM was station J, which ranged from a
low of
25.25x near the bottom to a high of
21.40x near the surface. Station J was the deepest
station sampled and was located in the heart of the
canyon (see Fig. 1). Several stations had surface POM
28
K.L. Bosley et al. / Journal of Marine Systems 50 (2004) 21–37
Fig. 4. Along-shore current speeds (dotted line) at 50-m depth on M-119, plotted over temperatures (solid line) measured in the upper part of
Astoria Canyon on M-118 at 200-m depth.
d13C that were nearly identical to bottom POM d13C.
One was station G, located just up-canyon from
station J, with a depth of more than 700 m. Two of
these were stations B and F, which were the northernmost and southernmost stations, respectively,
along a cross-canyon transect and were among the
shallowest sites sampled.
3.2. Biological observations
An example of the bioacoustic data collected for
choosing trawl locations is shown in Fig. 5. In this
example (from a 120 kHz profile, taken over the north
wall of the canyon), several distinct layers at shelf
depth, along the canyon wall, over a pinnacle at
f 225-m depth and at approximately the same depth
Table 1
Particulate organic matter d13C values from water samples collected
at stations located around Astoria Canyon at the surface, midwater,
and near the bottom
Surface
Station
Station
Station
Station
Station
Station
Station
Station
Station
A
B
C
D
E
F
G
I
J
22.83
23.38
22.37
–
–
22.27
24.48
23.96
21.40
Midwater
Bottom
22.95
23.14
23.79
–
24.43
24.29
–
25.24
23.66
Dashed lines represent locations that could not be sampled.
24.44
23.81
24.94
25.14
22.48
24.63
25.06
25.25
within the canyon proper can be seen. On the basis of
the IKMT and trawl data (described below), the layers
were later found to be correlated with catches of
rockfishes in close proximity to the canyon walls
and pinnacles and with euphausiids and Pacific hake
(Merluccius productus) in the layers farther away
from these topographic features, but still within the
canyon.
Two IKMT trawls were made along the northern
side of the canyon and one on the south side (Fig. 1).
Tow 1 (to 89 m) targeted shallow acoustic layers
along the northern canyon wall, and caught mostly
larger zooplankton (decapod larvae, euphausiids,
hyperiids, chaetognaths, and fish larvae), but no large
nekton (Table 2) were collected in this tow. The two
deeper tows (to 222 and 264 m) caught a variety of
large mesopelagic organisms, including midwater
shrimps, squids, and fishes (Table 2). The northern
lampfish (Stenobrachius leucopsarus) dominated the
catch by number and weight in tow 3 (Table 2).
However, in tow 2, the catch was predominantly made
up of the offshore species of euphausiid, Euphausia
pacifica; the trawl apparently passed through a layer
of this species.
Nine fish/decapod trawls (Fig. 1) were made from
the Sea Eagle. Data from only three of the hauls (R1,
B1, and B2) are reported here (Table 3) because they
were the only ones from which tissue samples and
stomachs were collected for comparing stable-isotope
data to stomach content data. Similar to the IKMT
tows, tow R1 fished in midwater and caught a low
diversity of taxa, which with the exception of some
K.L. Bosley et al. / Journal of Marine Systems 50 (2004) 21–37
29
Fig. 5. A 120-kHz bioacoustic profile taken on a north-to-south transect across the north wall of Astoria Canyon, Oregon. The vertical gridlines
represent 10-min time intervals.
Pacific hake, was comprised entirely of rockfishes of
the genus Sebastes. The deepest bottom tow, B1 (max.
depth = 549 m), caught a relatively high diversity of
fishes, including grenadiers, thornyheads (Sebastoloobus alascanus, Sebastolobus altivelis), sablefish
(Anoplopoma fimbria), viperfish (Chauliodus
macouni), and snailfishes (Family Liparididae), but
no rockfishes. There was also a fairly substantial catch
of tanner crabs (Chionoecetes spp.) in that haul.
Finally, the last tow (B2) contained mostly thornyheads, eelpouts (Family Zoarcidae), and Dover sole
(Microstomus pacificus) but few other species.
The stomach content data are presented in Table 4.
Of the rockfish stomachs that were analyzed, widow
rockfish (Sebastes entomelas) were found to have
primarily unidentifiable gelatinous material; yellowtail rockfish (Sebastes flavidus) were found to have
euphausiids, myctophids, and squids; and bocaccio
rockfish (Sebastes paucispinis) were found to have
only Pacific ocean perch (Sebastes alutus) and other
fish remains in their stomachs. The stomach contents
of the myctophid, California headlightfish (Diaphus
theta), were found to contain primarily euphausiids
(E. pacifica) and hyperiid amphipods, while the
northern lampfish (S. leucopsarus) had a similar diet
but also consumed copepods to some extent (Table 4).
3.3. Stable-isotope analyses
The carbon and nitrogen stable-isotope data for
individual fishes and invertebrates are presented in
Fig. 6A. The isotopic values of most of the fishes that
were sampled were enriched in heavier isotopes of
both carbon and nitrogen relative to the invertebrates
that were collected. To better compare the trophic
position of the rockfishes, d13C and d15N values of
only the Sebastes species are presented in Fig. 6B.
Both the d13C and d15N values were significantly
different between rockfish species ( p < 0.0001, SAS
General Linear Model). Of the five species of rockfish
that were sampled in the pelagic tow, bocaccio rockfish (n = 9) was the most enriched in 13C and 15N,
which is in agreement with the findings of the
stomach-content analysis indicating substantial piscivory by this species. A post-hoc, pairwise comparison
determined that bocaccio rockfish d13C values were
significantly enriched relative to both yellowtail rockfish (n = 17) and widow rockfish (n = 17), and canary
30
K.L. Bosley et al. / Journal of Marine Systems 50 (2004) 21–37
Table 2
Standardized densities (number per 1000 m3) and biomass (grams per 1000 m3) of zooplankton and micronekton collected in each Isaacs – Kidd
Midwater Trawl (IKMT) in Astoria Canyon in 2001
Cnidaria
Hydromedusae unidentified
Atolla sp.
Siphonopora
Siphonophora unidentified
Cephalopoda
Gonatus onyx
Taonius pavo
Crustacea
Cancer magister
Munida quadrispina
Sergestes similis
Pasiphaea pacifica
Pandalus jordani
Thysanoessa spinifera
Euphausia pacifica
Boreomysis califonica
Holmesiella anomola
Phronima sedentaria
Paraphronima gracilis
Primno macropa
Themisto pacifica
Cyphocaris challengeri
Ampelisca sp.
Karoga megalops
Stilipes distincta
Chaetognatha
Eukhronia hamata
Sagitta elegans
Sagitta scrippsae
Osteichthyes
Sebastes spp.
Stenobrachius leucopsaurus
Stenobrachius nannochir
Diaphus theta
Tarletonbeania crenularis
Bathylagus stilbius
Chauliodus macouni
Lycodapus spp.
Nectoliparis pelagicus
Lyopsetta exilis
Glyptocephalus zachirus
Tow 1 (max. depth = 89 m)
Tow 2 (max. depth = 222 m)
Tow 3 (max. depth = 264 m)
Density
Density
Density
Biomass
2.562
0.914
0.229
0.114
0.686
0.343
0.914
0.038
0.001
0.008
0.010
0.006
0.001
0.003
0.002
0.114
0.007
0.016
rockfish (Sebastes pinniger, n = 4) d13C values were
also significantly enriched relative to widow rockfish
(Tukey’s Studentized range test, a = 0.05). The d15N
values of bocaccio rockfish were also significantly
enriched relative to both yellowtail rockfish and
widow rockfish.
Biomass
1.209
0.213
0.341
0.384
0.085
0.207
0.437
2.050
2.263
11.785
3.886
0.098
0.000
0.805
4.699
0.360
320.239
47.881
0.128
0.013
0.085
0.085
0.171
0.003
0.000
0.009
0.011
0.114
1.942
0.686
0.114
Biomass
6.917
11.060
0.384
1.077
0.043
0.015
0.128
0.043
0.043
0.018
0.003
0.011
0.031
0.010
0.063
0.094
0.124
0.044
0.283
4.534
1.385
1.354
1.228
1.008
0.031
0.063
0.252
0.045
1.871
2.725
0.688
0.075
0.057
0.003
0.006
0.028
0.031
0.126
0.220
0.001
0.010
0.024
8.533
0.031
0.063
0.031
0.189
0.031
0.031
0.063
11.710
0.006
0.018
0.019
0.056
0.017
0.010
0.001
4. Discussion
4.1. Currents and hydrography
Current and temperature time series in Astoria
Canyon exhibit strong, semi-diurnal components at
K.L. Bosley et al. / Journal of Marine Systems 50 (2004) 21–37
31
Table 3
Standardized densities (number per 106 m3) of fish and decapods collected in midwater (R) and bottom (B) trawls in Astoria Canyon in 2001
Common name
Scientific name
Tanner crab
Myxinidae
Pacific hagfish
Scyliorhinidae
Brown cat shark
Alepocephalidae
California slickhead
Stomiidae
Pacific viperfish
Neoscopelidae
Blackchin
Pacific blackchin
Moridae
Pacific flatnose
Gadidae
Pacific hake
Macrouridae
Giant grenadier
Grenadiera
Scorpaenidae
Rougheye rockfish
Brown rockfish
Darkblotched rockfish
Widow rockfish
Yellowtail rockfish
Bocaccio
Canary rockfish
Shortspine thornyhead
Longspine thornyhead
Anoplopomatidae
Sablefish
Cyclopteridae
Unidentified snailfish
Zoarcidae
Snakehead eelpout
Black eelpout
Unidentified eelpout
Pleuronectidae
Dover sole
Deepsea sole
Arrowtooth flounder
Chionoecetes spp.
a
Tow R1
(max. depth = 89 m)
Tow B1
(max. depth = 549 m)
Tow B2
(max. depth = 340 m)
Density
Density
Density
22.01
0.54
Eptatretus stouti
0.51
0.54
Apristurus brunneus
5.63
0.54
Alepocephalus tenebrosus
0.51
Chauliodus macouni
65.52
Neoscopelus macrolepidotus
Scopelengys tristis
1.09
0.10
Antimora microlepis
Merluccius productus
0.51
19.30
Albatrossia pectoralis
Coryphaenoides spp.
Sebastes aleutianus
Sebastes auriculatus
Sebastes crameri
Sebastes entomelas
Sebastes flavidus
Sebastes paucispinis
Sebastes pinniger
Sebastolobus alascanus
Sebastolobus altivelis
1.09
8.70
748.32
0.27
19.99
0.69
31.02
51.70
4.14
2.07
1.33
149.66
12.75
13.29
Anoplopoma fimbria
12.80
2.17
Cyclopteridae
11.26
0.27
2.56
6.65
2.17
4.07
3.80
Lycenchelys crotalinus
Lycodes diapterus
Zoarcidae
Microstomus pacificus
Embassichthys bathybius
Atheresthes stomias
1.02
1.02
4.07
0.27
0.27
Possible complex of two species: Coryphaenoides acrolepis (Pacific grenadier) and C. cinerus (popeye grenadier).
all measured locations, have inertial frequency components only above shelf depth, and have a diurnalfrequency content that is weak above but strong
within the canyon.
The topography of Astoria Canyon, like other
deep, narrow canyons, clearly intensifies diurnal
motions (Fig. 3C). Results are consistent with the
much more extensive physical oceanographic investigations of Astoria Canyon by Hickey (1997).
One interesting aspect of Fig. 4 is the apparent
correlation of the subtidal signals in the two records,
with a slight time lead of current on T changes. Both
32
K.L. Bosley et al. / Journal of Marine Systems 50 (2004) 21–37
Table 4
Prey composition (percent of total weight) of three species of rockfishes (Sebastes spp.) and two mesopelagic myctophids from Astoria Canyon
collected in midwater and bottom trawls in June 2001
Prey items
Copepoda
Calanus marshallae
Clausoalanus spp.
Candacia spp.
unidentified calanoid
Hyperiidae
Themisto pacifica
Primo macropa
unidentified
Euphausiacea
Euphausia pacifica
unidentified
Decapoda
Pasiphaea pacifica
Cephalopoda
unidentified squid
Siphonophora
Other gelatinous material
Osteichthyes
Nectoliparis pelagicus
Stenobrachius leucopsarus
Sebastes alutus
unidentified fish remains
Unidentified material
Predator
S. entomelas
S. flavidus
S. paucispinis
D. theta
S. leucopsarus
Number examined
16
18
6
25
27
Length range (mm)
341 – 398
384 – 496
382 – 415
48 – 81
53 – 96
2.41
1.12
1.12
4.18
0.43
0.02
1.33
1.32
62.06
0.14
3.75
2.94
18.43
2.94
57.68
19.45
29.41
35.29
2.98
8.46
0.06
95.27
1.44
Hickey (1997) and Allen et al. (2001) have noted a
similar correlation in their measurements. The explanation begins by noting that currents in the near-surface
layer should be in approximate geostrophic balance
with the cross-shore pressure gradient (dp/dx). The
subtidal, along-shore, near-surface current record can
serve as a surrogate for dp/dx. Fluid in the canyon is
subject to overlying pressure gradients (dp/dx) and
other forces, but as Freeland and Denman (1982) note,
the walls of the canyon prevent the primary force
balance in the canyon from being geostrophic as it is
near-surface. Instead, dp/dx forcing in the canyon
opposes frictional forces and along-axis baroclinic
pressure gradients, which together determine alongaxis flow. Changes in dp/dx can therefore alter the
strength and possibly the direction of along-axis flow,
with one consequence being changes in T. Larger,
negative dp/dx drive stronger, up-canyon flow, causing
isopycnals to bend upward and T at a fixed location to
23.39
3.10
91.02
8.74
0.25
0.68
20.59
decrease. The correlation of surface currents and T in
the canyon shown in Fig. 4 occurs in this way.
The correlation of subtidal T at 200 m and alongaxis currents at M-118 at 225 m was not nearly as
good. The poor correlation of those two time series
(not shown) makes it quite unlikely that changes in T
in Fig. 4 were caused by horizontal advection past the
measurement site. The reason instead must be the
vertical displacement of isopycnals, a displacement
documented by Hickey (1997) using CTD measurements. Therefore, in the upper canyon, T primarily
recorded the vertical movement of isotherms in response to up- or down-canyon flow. Temperature at
M-118 at 200-m depth over the time period June 29th
to July 6th decreased by as much as 0.4 jC (Fig. 4).
Using a dT/dz of 4.1 10 3 jC m 1 at 200-m depth
estimated from the central profile of Fig. 3A, the
corresponding vertical displacement of isopycnals at
M-118 would be 98 m.
K.L. Bosley et al. / Journal of Marine Systems 50 (2004) 21–37
33
Fig. 6. (A) d13C vs. d15N of all of the fish and invertebrates that had tissue samples collected from sites in and around Astoria Canyon. Species
that are followed by a (B) are benthic and those that are followed by a (BP) are benthopelagic. (B) d13C vs. d15N of rockfish that had tissue
samples collected.
34
K.L. Bosley et al. / Journal of Marine Systems 50 (2004) 21–37
Typical southward summer winds during the measurement period signal a persistent, but variable,
onshore atmospheric-pressure gradient. Subtidal currents in the upper water column move southward over
the canyon, and currents in the canyon should upwell
as a result. An expectation based on previous measurements and models for this and other deep, narrow
canyons (e.g. Allen, 1996; Hickey, 1997; She and
Klinck, 2000) is that deep, upwelled water and the
nutrients contained therein will continue upward, spill
onto the shelf, and nourish the shelf downstream of
the southern canyon edge, resulting in elevated productivity there. For example, it was along the southern
side of Astoria Canyon where Pereyra et al. (1969)
reported much higher catches of fish. The subtidal
current and T record in Fig. 4 suggests that the rate of
upwelling varies. Hickey (1997) shows from measurements in Astoria Canyon that under such conditions,
upwelling is not laterally uniform. In fact, at times
before and after maximum upwelling, down-canyon
flow occurs on the upstream side of the canyon,
leading to a cyclonic eddy that extends downward
into it and as much as 50 m above it near the canyon
head. This recirculation (Hickey, 1997) may prolong
the residence time of nutrients and biota within the
canyon.
4.2. Water chemistry
The d13C values of POM were typical of marine
phytoplankton, which have been shown to range
anywhere from
24x to
18x (Fry and Sherr,
1984; Rau et al., 1990). The station (J) with the greatest
variability between d13C values of surface and bottom
POM was the deepest site that was sampled and was
located along the axis of the canyon. With the exception of Station G (which had nearly identical d13C
values of surface and bottom POM), the other stations
along the axis of the canyon that had samples collected
from multiple depths (C and A) had a 1.6x to 2.5x
difference between surface and bottom POM. The
shallow stations on the north and south sides of the
canyon showed the greatest homogeneity between
d13C values of surface and bottom POM.
Assuming 1 – 2x enrichment in 12C between trophic levels (DeNiro and Epstein, 1978), it appears that
many of the animals at higher trophic levels, particularly invertebrates and small fish, were probably deriv-
ing their carbon from localized primary production
rather than from distant sources, based on the range
of POM d13C values that were measured. This determination is dependant on the length of time necessary
to incorporate the isotopic signature of a diet. A longlived rockfish would probably reflect an integration of
isotopic signatures over a longer period of time, whereas invertebrates and smaller (i.e. micronektonic) fish
would reflect integration over shorter time periods.
The importance of localized primary production to
the food web around the canyon may have been
elevated during 2001. Terrestrial and riverine inputs
of carbon were expected to be anomalous as it was a
drought year. Indeed, the average monthly flow of the
Columbia River in June 2001 was 4296 m3 s 1,
which makes it one of the lowest on record. River
flow was substantially lower than the June averages
from the previous 10 years (1991 – 2000 ranged from
5775 to 14570 m3 s 1; data from United States
Geological Survey station at Beaver, Oregon).
4.3. Biological sampling
Many of the zooplankton and micronekton collected in the IKMT tows in the canyon are known to
occupy the epipelagic (upper 200 m) layers of the
ocean off Oregon although a number of these taxa are
known to vertically migrate down to the mesopelagic
zone during daytime (Pearcy and Laurs, 1966; Krygier and Pearcy, 1981). However, many of the micronektonic fishes are rarely found over the continental
shelf (Brodeur et al., 2003); some (e.g. Stenobrachius
nannochir) are not known to migrate up into epipelagic waters (Pearcy et al., 1979) and are not likely to
occur this close to the coast except in canyons or other
areas with substantial on-shelf transport. Brodeur et al.
(2003) found that the distribution of several of the
dominant myctophids we collected in this study was
displaced farther onto the shelf on a transect near
Astoria Canyon than on other transects along the coast
of Oregon, and speculated that they may be advected
onshore by way of the canyon. Although our micronekton sampling in Astoria Canyon was limited, we
observed densities and biomasses of some taxa that
were high relative to nearby areas (Pearcy and Laurs,
1966; Kalish et al., 1986), indicating perhaps an
interaction between behavior of these organisms and
currents affected by the canyon topography (see also
K.L. Bosley et al. / Journal of Marine Systems 50 (2004) 21–37
Greene et al., 1988; Macquart-Moulin and Patriti,
1996; Mackas et al., 1997). These high densities were
corroborated by cross-canyon acoustic transects,
which indicated substantial scattering layers in the
canyon and which often intersected the canyon walls,
especially during daytime (Brodeur, personal observation and example in Fig. 5).
There appear to be trophic effects associated with
the cross-canyon horizontal structure in Astoria
Canyon. High densities of several species of pelagic
rockfishes were collected in our shallow trawls and
were often observed in remotely-operated-vehicle
video transects during this cruise (Wakefield, unpublished data). Dense swarms of euphausiids were also
observed near the bottom at the rim of the canyon
during daytime deployments (Gómez-Gutiérrez et
al., 2003). Stable-isotope and dietary data suggest
that the rockfish species may utilize either euphausiid aggregations or mesopelagic prey that are
advected up the canyon and toward the canyon
walls, where the shallow bottom blocks their vertical
descent (Genin, 2004), or where they are then
advected onto the adjoining shelf and trapped, making them vulnerable to predation by rockfishes
(Pereyra et al., 1969). This trophic interaction between rockfishes and mesopelagic prey has been
observed numerous times in the North Pacific, both
on offshore banks (Brodeur and Pearcy, 1984; Genin
et al., 1988) and in canyons (Pereyra et al., 1969;
Lorz et al., 1983; Brodeur, 2001), which may point
to these areas as being critical habitats for these
heavily exploited rockfish species (Yoklavich et al.,
1999).
It is also clear from the stable-isotope and dietary
data that some rockfish species occupy a higher
trophic position relative to other rockfish species
feeding in the same general area. These data show
that adult bocaccio rockfish were at a higher trophic
position than any of the other rockfish species that
were sampled, consistent with other dietary studies of
this species (summarized by Love et al., 2002). The
lower-trophic positions of widow rockfish and yellowtail rockfish relative to bocaccio, as indicated by
their significantly lower d13C and d15N values, are
also consistent with other dietary studies (Love et al.,
2002; Lee, 2003) that found their diets to be comprised of gelatinous zooplankton and micronekton,
including smaller fishes, euphausiids and amphipods.
35
The d15N values of myctophids, sergestid and
pasiphaed shrimp, and squid (Gonatus onyx) were
clustered between the other fish species and most of
the other invertebrates, indicating that they all play an
intermediary role in energy flow within the canyon
food web. In an earlier study off Oregon, Tyler and
Pearcy (1975) observed three species of myctophids
(two in common with the current study, D. theta and
Stenobrachius leucopsaurus) to feed primarily on
euphausiids, copepods, and hyperiid amphipods. Our
stable-isotope data, along with diet studies off Oregon
(Nishida et al., 1988), indicate that shrimp and squid
may also represent a link between zooplankton that
graze on primary producers and higher trophic levels.
5. Conclusions
This study illustrates the potential of physical
processes to concentrate marine organisms in and
around undersea canyons. Recirculation (Hickey,
1997), for example, favors a prolonged residence time
of nutrients and biota within the canyon. At the time
of this study, local primary production appeared to
have a predominant effect on the canyon food web
compared to other potential sources. Species composition was shown to vary both vertically in the water
column and spatially. Stable-isotope and dietary data
suggest that rockfish may utilize either euphausiid
aggregations or mesopelagic prey that are advected up
the canyon and towards the canyon walls, and show
species-specific differences in the trophic position of
fishes. Fish that were found to be primarily piscivorous (based on gut contents) had d15N and d13C
values that were enriched relative to fish that were
found to be omnivorous. Fish that were shown to be
entirely planktivorous had d15N values that were
depleted relative to other fish. It is hoped that the
information presented here may serve to support
future studies in this and possibly other highly productive undersea canyons.
Acknowledgements
Funding for this work was provided by the NOAA
Northwest Fisheries Science Center, NOAA Office of
Ocean Exploration, NOAA Pacific Marine Environ-
36
K.L. Bosley et al. / Journal of Marine Systems 50 (2004) 21–37
mental Laboratory, the West Coast and Polar Undersea Research Center of NOAA’s National Undersea
Research Program, Oregon State University, and
NOAA Oceanic and Atmospheric Research Office
of Marine and Aviation Operations for R/V Brown
ship time.
The authors wish to thank the following individuals for assisting with various aspects of this project:
Doug Burrows, Julia Clemons, Bob Embley, Chris
Goldfinger, Chris Harvey, Gordon Hendler, Greg
Krutzikowsky, Phil Levin, Bruce McCain, Susan
Merle, Todd Miller, William Pearcy, Bill Peterson,
Kevin Piner, Bill Reichert, Joe Resing, Josie Thompson and Sharon Walker. Additional thanks go to the
Canadian Scientific Submersible Facility; Capt. Dan
Parker and the crew of the F/V Sea Eagle; Jennifer
Bloeser and Dave Douglas for assistance with sample
collection on the Sea Eagle, the officers and crew of
the R/V Ronald H. Brown, and Bill Pearcy, Bill
Peterson, Karen Bosley and three anonymous
reviewers for comments on earlier versions of the
manuscript. This is contribution no. 2542 from
NOAA Pacific Marine Environmental Laboratory.
References
Allen, S.E., 1996. Topographically generated subinertial flows
within a finite-length canyon. J. Phys. Oceanogr. 26,
1608 – 1632.
Allen, S.E., Vindeirinho, C., Thomson, R.E., Foreman, M.G.G.,
Mackas, D.L., 2001. Physical and biological processes over a
submarine canyon during an upwelling event. Can. J. Fish.
Aquat. Sci. 58, 671 – 684.
Baker, E.T., Milburn, H.B., 1997. MAPR: a new instrument for
hydrothermal plume mapping. Ridge Events 8, 23 – 25.
Brodeur, R.D., 2001. Habitat-specific distribution of Pacific ocean
perch (Sebastes alutus) in Pribilof Canyon, Bering Sea. Cont.
Shelf Res. 21, 207 – 224.
Brodeur, R.D., Pearcy, W.G., 1984. Food habits and dietary overlap
of some shelf rockfishes (Genus Sebastes) from the northeastern
Pacific Ocean. Fish. Bull. 82, 269 – 293.
Brodeur, R.D., Pearcy, W.G., Ralston, S., 2003. Abundance and
distribution patterns of nekton and micronekton in the Northern
California current transition zone. J. Oceanogr. 59, 515 – 535.
Carlson, P.R., 1968. Marine Geology of Astoria Submarine
Canyon. PhD thesis, Oregon State University, Corvallis,
OR, 259 pp.
Carter, G.S., Gregg, M.C., 2002. Intense, variable mixing near the
head of Monterey Submarine Canyon. J. Phys. Oceanogr. 32,
3145 – 3165.
Craig, H., 1957. Isotopic standards for carbon and oxygen and
correction factors for mass spectrometric analysis of carbon
dioxide. Geochim. Cosmochim. Acta 12, 133 – 149.
Davenport, S.R., Bax, N.J., 2002. A trophic study of a marine
ecosystem off southeastern Australia using stable isotopes of
carbon and nitrogen. Can. J. Fish. Aquat. Sci. 59, 514 – 530.
DeNiro, M.J., Epstein, S., 1977. Mechanism of carbon isotope
fractionation associated with lipid synthesis. Science 197,
261 – 263.
DeNiro, M.J., Epstein, S., 1978. Influence of diet on the distribution
of carbon isotopes in animals. Geochim. Cosmochim. Acta 42,
495 – 506.
DeNiro, M.J., Epstein, S., 1981. Influence of diet on the distribution
of nitrogen isotopes in animals. Geochim. Cosmochim. Acta 45,
1885 – 1994.
Emery, W.J., Thomson, R.E., 1997. Data Analysis Methods in
Physical Oceanography. Pergamon Press, New York, p. 634.
Freeland, H.J., Denman, K.L., 1982. A topographically controlled
upwelling center off Southern Vancouver Island. J. Mar. Res.
40, 1069 – 1093.
Fry, B., Sherr, E., 1984. d13C measurements as indicators of carbon
flow in marine and freshwater ecosystems. Contrib. Mar. Sci.
27, 13 – 47.
Gardner, W.D., 1989. Periodic resuspension in Baltimore Canyon by
focusing of internal wavers. J. Geophys. Res. 94, 18185 – 18194.
Genin, A., 2004. Trophic focusing: the role of bio-physical coupling in the formation of animal aggregations over abrupt topographies. J. Mar. Syst. (this issue).
Genin, A., Haury, L., Greenblatt, P., 1988. Interactions of migrating zooplankton with shallow topography: predation by rockfishes and intensification of patchiness. Deep-Sea Res. 35,
151 – 175.
Gómez-Gutiérrez, J., Peterson, W.T., De Robertis, A., Brodeur,
R.D., 2003. Mass mortality of krill caused by parasitoid ciliates.
Science 301, 339.
Greene, C.H., Wiebe, P.H., Burczynski, J., Youngbluth, M.J.,
1988. Acoustical detection of high-density krill demersal layers
in the submarine canyons off Georges Bank. Science 241,
359 – 361.
Hickey, B.M., 1989. Patterns and processes of circulation over the
shelf and slope. In: Landry, M.R., Hickey, B.M. (Eds.), Coastal
Oceanography of Washington and Oregon. Elsevier, Amsterdam, pp. 41 – 116.
Hickey, B., 1995. Coastal submarine canyons. In: Mueller, P., Henderson, D. (Eds.), Proceedings Hawaii Winter Workshop, January 17 – 10, 1995, Univ. Hawaii, pp. 95 – 100.
Hickey, B., 1997. The response of a steep-sides, narrow canyon to
time variable wind forcing. J. Phys. Oceanogr. 27, 697 – 726.
Hickey, B., Baker, E., Kachel, N., 1986. Suspended particle movement in and around Quinault submarine canyon. Mar. Geol. 71,
35 – 83.
Hill, J.K., Wheeler, P.A., 2002. Organic carbon and nitrogen in the
northern California current system: comparison of offshore, river plume, and coastally upwelled waters. Prog. Oceanogr. 53,
369 – 387.
Hunkins, K., 1988. Mean and tidal currents in Baltimore Canyon. J.
Geophys. Res. 93, 6917 – 6929.
K.L. Bosley et al. / Journal of Marine Systems 50 (2004) 21–37
Kalish, J.M., Greenlaw, C.F., Pearcy, W.G., Holliday, D.V., 1986.
The biological and acoustical structure of sound scattering
layers off Oregon. Deep-Sea Res. 33, 631 – 653.
Kampf, J., Fohrmann, H., 2000. Sediment-driven downslope flow
in submarine canyons and channels. J. Phys. Oceanogr. 30 (9),
2302 – 2319.
Koslow, J.A., Ota, A., 1981. The ecology of vertical migration in
three common zooplankters in La Jolla Bight, April – August
1967. Biol. Oceanogr. 1, 107 – 134.
Krygier, E.E., Pearcy, W.G., 1981. Vertical distribution and biology
of pelagic decapod crustaceans off Oregon. J. Crustac. Biol. 1,
70 – 95.
Kunze, E., Rosenfeld, L.K., Carter, G.S., Gregg, M.C., 2002. Internal waves in Monterey submarine canyon. J. Phys. Oceanogr.
32, 1890 – 1913.
Lafuente, J.G., Sarhan, T., Vargas, M., Plaza, F., 1999. Tidal
motions and tidally induced fluxes through La Linea Submarine
Canyon, western Alboran Sea. J. Geophys. Res. Oceans 104,
3109 – 3119.
Lee, Y.W., 2003. Oceanographic effects on the dynamics of food
habits and growth condition of some groundfish species of the
Pacific Northwest. PhD thesis, Oregon State University.
Lorz, H.V., Pearcy, W.G., Fraidenburg, M., 1983. Notes on the
feeding habits of the yellowtail rockfish, Sebastes flavidus, off
Washington and in Queen Charlotte Sound. Calif. Fish Game
69, 33 – 38.
Love, M.S., Yoklavich, M., Thorsteinson, L., 2002. The Rockfishes
of the Northeast Pacific. The University of California Press,
Berkeley, CA.
Lueck, R.G., Osborn, T.R., 1985. Turbulence measurements in a
submarine canyon. Cont. Shelf Res. 4, 681 – 695.
Mackas, D.L., Kieser, R., Saunders, M., Yelland, D.R., Brown,
R.M., Moore, D.F., 1997. Aggregations of euphausiids and Pacific hake (Merluccius productus) along the outer continental
shelf off Vancouver Island. Can. J. Fish. Aquat. Sci. 54,
2080 – 2096.
Macquart-Moulin, C., Patriti, G., 1996. Accumulation of migratory
micronekton crustaceans over the upper slope and submarine
canyons of the northwestern Mediterranean. Deep-Sea Res.
43, 579 – 601.
McConnaughey, T., McRoy, C.P., 1979. Food-web structure and the
fractionation of carbon isotopes in the Bering Sea. Mar. Biol. 53,
257 – 262.
Nishida, S., Pearcy, W.G., Nemoto, T., 1988. Feeding habits of
mesopelagic shrimps collected off Oregon. Bull. Ocean Res.
Inst. 26 (II), 99 – 108.
Noble, M., Butman, B., 1989. The structure of subtidal currents
within and around Lydonia Canyon, Evidence for enhanced
cross-shelf fluctuation over the mouth of the canyon. J. Geophys. Res. 94, 8091 – 8110.
Owens, N.J.R., 1987. Natural variations in 15N in the marine environment. Adv. Mar. Biol. 24, 390 – 451.
37
Pearcy, W.G., Laurs, R.M., 1966. Vertical migration and distribution of mesopelagic fishes off Oregon. Deep-Sea Res. 13,
153 – 165.
Pearcy, W.G., Nemoto, T., Okiyama, M., 1979. Mesopelagic fishes
of the Bering Sea and adjacent northern North Pacific Ocean. J.
Oceanogr. 35, 127 – 135.
Pereyra, W.T., Pearcy, W.G., Carvey Jr., F.E., 1969. Sebastodes
flavidus, a shelf rockfish feeding on mesopelagic fauna, with
consideration of the ecological implications. J. Fish. Res. Board
Can. 26, 2211 – 2215.
Perry, R.I., Thompson, P.A., Mackas, D.L., Harrison, P.J., Yelland,
D.R., 1999. Stable carbon isotopes as pelagic food web tracers
in adjacent shelf and slope regions off British Columbia, Canada. Can. J. Fish. Aquat. Sci. 56, 2477 – 2486.
Peterson, B.J., Fry, B., 1987. Stable isotopes in ecosystem studies.
Ann. Rev. Ecolog. Syst. 18, 293 – 320.
Petruncio, E.T., Rosenfeld, L.K., Paduan, J.D., 1998. Observations
of the internal tide in Monterey Canyon. J. Phys. Oceanogr. 28,
1873 – 1903.
Plank, W.S., Zaneveld, J.R., Pak, H., 1974. Temporal variability of
suspended matter in Astoria Canyon. J. Geophys. Res. 79,
4536 – 4541.
Polunin, N.V.C., Morales-Nin, B., Pawsey, W.E., Cartes, J.E., Pinnegar, J.K., Moranta, J., 2001. Feeding relationships in Mediterranean bathyal assemblages elucidated by stable nitrogen and
carbon isotope data. Mar. Ecol., Prog. Ser. 220, 13 – 23.
Rau, G.H., Teyssie, J.-L., Rassoulzadegan, F., Fowler, S.W., 1990.
13 12
C/ C and 15N/14N variations among size fractionated marine
particles: implications for their origin and trophic relationships.
Mar. Ecol., Prog. Ser. 59, 33 – 38.
She, J., Klinck, J.M., 2000. Flow near submarine canyons driven by
constant winds. J. Geophys. Res. 15, 28671 – 28694.
Sobarzo, M., Figueroa, M., Djurfeldt, L., 2001. Upwelling of
subsurface water into the rim of the Biobio submarine canyon as a response to surface winds. Cont. Shelf Res. 21,
279 – 299.
Tieszen, L.L., Boutton, T.W., Tesdahl, K.G., Slade, N.A., 1983.
Fractionation and turnover of stable carbon isotopes in animal
tissues: implications for d13C analysis of diet. Oecologia 57,
32 – 37.
Tyler Jr., H.R., Pearcy, W.G., 1975. The feeding habits of three
species of lanternfishes (Family Myctophidae) off Oregon,
USA. Mar. Biol. 32, 7 – 11.
Underwood, M.B., 1991. Submarine canyons, unconfined turbidity
currents, and sedimentary bypassing of forearc regions. Rev.
Aquat. Sci. 4, 149 – 200.
Yoklavich, M., Greene, G., Calliet, G.M., Sullivan, D.E., Lea, R.N.,
Love, M.S., 1999. Habitat associations of deep-water rockfishes
in a submarine canyon: an example of a natural refuge. Fish.
Bull. 98, 625 – 641.