U.S. DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

National Marine Fisheries Service

NOAA Technical Memorandum NMFS-NWFSC-74

Neustonic Mesozooplankton

Abundance and Distribution

in the Northern California Current,

2000 and 2002

February 2006
NOAA Technical Memorandum

NMFS Series

The Northwest Fisheries Science Center of the National

Marine Fisheries Service, NOAA, uses the NOAA

Technical Memorandum NMFS series to issue informal scientific and technical publications when complete formal review and editorial processing are not

appropriate or feasible due to time constraints. Documents published in this series may be referenced in the

scientific and technical literature.

The NMFS-NWFSC Technical Memorandum series of

the Northwest Fisheries Science Center continues the

NMFS-F/NWC series established in 1970 by the

Northwest & Alaska Fisheries Science Center, which

has since been split into the Northwest Fisheries

Science Center and the Alaska Fisheries Science

Center. The NMFS-AFSC Technical Memorandum

series is now being used by the Alaska Fisheries

Science Center.

Reference throughout this document to trade names

does not imply endorsement by the National Marine

Fisheries Service, NOAA.

This document should be cited as follows:

Pool, S.S., and R.D. Brodeur. 2006. Neustonic

mesozooplankton abundance and distribution in the

northern California Current, 2000 and 2002. U.S.

Dept. Commer., NOAA Tech. Memo. NMFSNWFSC-74, 76 p.
NOAA Technical Memorandum NMFS-NWFSC-74

Neustonic Mesozooplankton

Abundance and Distribution

in the Northern California Current,

2000 and 2002

Suzan S. Pool* and Richard D. Brodeur

Northwest Fisheries Science Center

Fish Ecology Division, Newport Research Station

Hatfield Marine Science Center

2032 Southeast OSU Drive

Newport, Oregon 97365

Oregon State University

Cooperative Institute for Marine Resources Studies

Hatfield Marine Science Center

2030 Southeast Marine Science Drive

Newport, Oregon 97365

February 2006

U.S. DEPARTMENT OF COMMERCE

Carlos M. Gutierrez, Secretary

National Oceanic and Atmospheric Administration

Vice Admiral Conrad C. Lautenbacher, Jr. USN (Ret), Administrator

National Marine Fisheries Service

William T. Hogarth, Assistant Administrator for Fisheries

*
Most NOAA Technical Memorandums NMFS-NWFSC

are available online at the Northwest Fisheries Science

Center web site (http://www.nwfsc.noaa.gov)

Copies are also available from:

National Technical Information Service

5285 Port Royal Road

Springfield, VA 22161

phone orders (1-800-553-6847)

e-mail orders (orders@ntis.fedworld.gov)

ii
Table of Contents 

List of Figures...............................................................................................................................................v

List of Tables ..............................................................................................................................................vii

Executive Summary .....................................................................................................................................ix

Acknowledgments......................................................................................................................................xiii

Introduction...................................................................................................................................................1

Methods ........................................................................................................................................................2

Survey Area ..............................................................................................................................................2 

Sample Protocols......................................................................................................................................2 

Data Analysis............................................................................................................................................4 

Results...........................................................................................................................................................6

Physical Parameters..................................................................................................................................6 

Chlorophyll a..........................................................................................................................................14 

Biovolumes.............................................................................................................................................14 

Mesozooplankton Abundance ................................................................................................................14 

Copepoda............................................................................................................................................28 

Amphipoda.........................................................................................................................................30 

Euphausiacea......................................................................................................................................37 

Decapoda............................................................................................................................................37 

Chaetognatha......................................................................................................................................46 

Osteichthyes.......................................................................................................................................46 

Others.................................................................................................................................................46 

Spatial Variability...................................................................................................................................51 

Species Diversity....................................................................................................................................53 

Species Associations ..............................................................................................................................53 

Diel Studies ............................................................................................................................................57 

Discussion...................................................................................................................................................67

Conclusion ..................................................................................................................................................72

References...................................................................................................................................................73

iii
iv
List of Figures 

Figure 1. Pacific Northwest coastline, with survey area..............................................................................3

Figure 2. The 1-m depth temperature in June and August 2000..................................................................8

Figure 3. The 1-m depth temperature in June and August 2002..................................................................9

Figure 4. The 1-m depth salinity in June and August 2000. ......................................................................10

Figure 5. The 1-m depth salinity in June and August 2002. ......................................................................11

Figure 6. The 1-m depth water density in June and August 2000..............................................................12

Figure 7. The 1-m depth water density in June and August 2002..............................................................13

Figure 8. Chlorophyll a at 3-m depth in June and August 2000................................................................15

Figure 9. Chlorophyll a at 3-m depth in June and August 2002................................................................16

Figure 10. Biovolumes of neuston samples in June and August 2000.......................................................17

Figure 11. Biovolumes of neuston samples in June and August 2002.......................................................18

Figure 12. Composition of major neustonic mesozooplankton taxonomic groups 

collected during four cruises.......................................................................................................................28

Figure 13. Distribution of neustonic mesozooplankton concentrations in June and August 2000. ...........31

Figure 14. Distribution of neustonic mesozooplankton concentrations in June and August 2002. ...........32

Figure 15. Abundance and distribution of Hyperoche medusarum concentrations in 

June and August 2000.................................................................................................................................33

Figure 16. Abundance and distribution of Hyperoche medusarum concentrations in 

June and August 2002.................................................................................................................................34

Figure 17. Abundance and distribution of T. pacifica concentrations in June and August 2000...............35

Figure 18. Abundance and distribution of T. pacifica concentrations in June and August 2002...............36

Figure 19. Abundance and distribution of Pacific krill concentrations in June and August 2000.............38

Figure 20. Abundance and distribution of Pacific krill concentrations in June and August 2002.............39

Figure 21. Abundance and distribution of T. spinifera concentrations in June and August 2000. ............40

Figure 22. Abundance and distribution of T. spinifera concentrations in June and August 2002. ............41

Figure 23. Abundance and distribution of Dungeness crab megalopae concentrations in 

June and August 2000.................................................................................................................................42

Figure 24. Abundance and distribution of Dungeness crab megalopae concentrations in 

June and August 2002.................................................................................................................................43

Figure 25. Abundance and distribution of Oregon cancer crab and red rock crab megalopae 

concentrations in June and August 2000.....................................................................................................44

v
Figure 26. Abundance and distribution of Oregon cancer crab and red rock crab megalopae 

concentrations in June and August 2002.....................................................................................................45

Figure 27. Abundance and distribution of Sagitta spp. concentrations in June and August 2000.............47

Figure 28. Abundance and distribution of Sagitta spp. concentrations in June and August 2002.............48

Figure 29. Abundance and distribution of larval and juvenile fish concentrations in June 

and August 2000. ........................................................................................................................................49

Figure 30. Abundance and distribution of larval and juvenile fish concentrations in June 

and August 2002. ........................................................................................................................................50

Figure 31. Inshore-offshore distribution of five most abundant neustonic mesozooplankton 

taxa along six main transects from north to south in June 2000. ................................................................52

Figure 32. Inshore-offshore distribution of five most abundant neustonic mesozooplankton 

taxa along six main transects from north to south in August 2000.............................................................54

Figure 33. Inshore-offshore distribution of five most abundant neustonic mesozooplankton 

taxa along six main transects from north to south in June 2002. ................................................................55

Figure 34. Inshore-offshore distribution of five most abundant neustonic mesozooplankton 

taxa along six main transects from north to south in August 2002.............................................................56

Figure 35. Dendrograms of neustonic mesozooplankton taxa cluster groupings for June and 

August 2000................................................................................................................................................58

Figure 36. Dendrograms of neustonic mesozooplankton taxa cluster groupings for June and 

August 2002................................................................................................................................................59

Figure 37. Temporal variations in water temperature, salinity, neustonic mesozooplankton 

biovolumes, chlorophyll a, and concentrations of five most abundant taxa and total 

mesozooplankton at station NH-5 in June 2002. ........................................................................................64

Figure 38. Diel pattern of neustonic mesozooplankton species diversity indices and number 

of taxa in June 2002 at station NH-5 and August 2002 at station HH-2.....................................................65

Figure 39. Temporal variations in water temperature, salinity, neustonic mesozooplankton 

biovolumes, chlorophyll a, and concentrations of five most abundant taxa and total 

mesozooplankton at station HH-2 in August 2002. ....................................................................................66

vi
List of Tables 

Table 1. Data ranges of physical parameters and chlorophyll a by cruise...................................................7

Table 2. Biovolumes of neustonic mesozooplankton samples in June and August 2000 and 2002. .........19

Table 3. Frequency of occurrence, mean concentration, and standard deviation of taxa present 

in samples from June and August 2000 and 2002.......................................................................................20

Table 4. Ten most abundant neustonic mesozooplankton taxa in June and August 2000 and 2002..........29

Table 5. Concentrations of taxa in the June 2002 diel study at station NH-5............................................60

Table 6. Concentrations of taxa in the August 2002 diel study at station HH-2........................................62

vii
viii
Executive Summary 

Most plankton surveys off Oregon and northern California have focused along one 

transect off Newport, Oregon, or only on the ichthyoplankton in the water column and at the 

ocean surface. Therefore as part of juvenile salmonid (Oncorhynchus spp.) ocean sampling 

funded by U.S. Global Ocean Ecosystem Dynamics, a study was undertaken to collect neustonic 

mesozooplankton from Crescent City, California, to Newport, Oregon, during four cruises in 

June and August 2000 and 2002. 

These collections were made for comparison with stomach contents of juvenile 

salmonids; however this technical memorandum does not include that comparison. It contains 

the results of our analysis of the species composition, relative abundances, and spatial 

distributions of the neuston on a point-by-point basis for both years instead of using geostatistics 

as previously done for only 2000 by Reese et al. (2005). In addition to regular sampling we 

conducted two diel studies in 2002 to examine temporal variations of the neustonic 

mesozooplankton population. 

Overall 347 samples were collected, 144 taxa were identified, and 38,325 specimens 

were counted. Our findings show that: 

• Dungeness crab (Cancer magister) megalopae, Oregon cancer (C. oregonensis) and red 

rock crab (C. productus) megalopae (not identifiable to either species), Thysanoessa 

spinifera, Pacific krill (Euphausia pacifica), Hyperoche medusarum, Themisto pacifica, 

and Sagitta spp. were the dominant taxa. 

• Species diversity was higher in 2002 than in 2000, but it was not significantly different 

between years or seasons. 

• Species cluster groupings based on station assemblages included: 

o Dungeness crab megalopae, Oregon cancer and red rock crab megalopae, and Pacific 

rock crab (C. antennarius) and graceful crab (C. gracilis) megalopae (not identifiable 

to either species); 

o terrestrial insects and benthic gammarids; 

o pelagic euphausiids and hyperiids; 

o chaetognaths; and 

o shrimp larvae. 

• In the diel studies more taxa were collected at night than during the day. 

• In 2000, 1-m water temperatures were warmer, 3-m chlorophyll a concentrations were 

lower, and neustonic mesozooplankton abundance was lower than in 2002. In 2000 and 

ix
2002 salinity was lower, density was lower, and sample biovolumes were larger in June 

than in August. 

Surveys

Each of the four cruises lasted 14–18 days and primarily surveyed over the continental 

shelf with occasion sampling beyond the shelf break. Six major transects were sampled first, 

then additional stations on these or other transects based on fine-scale oceanographic features 

were sampled. Samples were collected using a surface-towing neuston net. 

In addition to regular sampling, two diel studies were conducted in 2002 to examine 

temporal variations of the neustonic mesozooplankton population. A conductivity, temperature, 

and depth profiler was deployed to measure physical characteristics of the ocean water. 

Chlorophyll a was collected from 3 m deep and analyzed by cold-acetone extraction and 

fluorescence. Zooplankton were collected with a surface-towing neuston net, then identified and 

enumerated in the laboratory. 

Results 

Of the 144 taxa identified in the four cruises, Dungeness crab megalopae, Oregon cancer 

and red rock crab megalopae, Thysanoessa spinifera, Pacific krill, Hyperoche medusarum, 

Themisto pacifica, and Sagitta spp. were dominant. Decapods dominated both years in June 

whereas euphausiids dominated in August 2000 and chaetognaths dominated in August 2002. 

Other taxa caught included crab zoeae, shrimp larvae, mysids, insects, fish larvae and juveniles, 

copepods, polychaetes, squids, heteropods, pteropods, cumaceans, isopods, and caprellids. 

Variations in species composition were observed in the spatial distribution, cross-shelf 

distribution, and diel patterns. Inshore-offshore distribution of the five most abundant taxa 

varied among and within cruises along the six main transects. Spatial variability also was 

apparent from north to south. 

Species diversity was higher in 2002 than in 2000, but it was not significantly different 

between years or seasons. Analysis of species cluster groupings based on station assemblages 

included 17 taxa in June 2000, 20 in August 2000, 33 in June 2002, and 17 in August 2002. 

Cluster groupings included: 

1) Dungeness crab megalopae, Oregon cancer and red rock crab megalopae, and Pacific 

rock crab and graceful crab megalopae; 

2) terrestrial insects and benthic gammarids; 

3) pelagic euphausiids and hyperiids; 

4) chaetognaths; and 

5) shrimp larvae. 

In the diel study more taxa were collected at night than during the day. The region 

surveyed covers a highly dynamic environment due to the strong upwelling that characterizes the 

California Current. The changing oceanographic conditions, compounded with variable life 

x
history patterns of zooplankton, influence the species composition and abundance of neustonic 

mesozooplankton. 

Over the survey area the coldest water was nearshore and over Heceta Bank during all 

cruises. Salinity on the shelf was significantly lower in June than in August of 2000 and 2002. 

Density was higher over the shelf than offshore and higher in August than in June both years. 

Chlorophyll a concentrations were higher nearshore or over Heceta Bank than elsewhere. 

Biovolumes of samples were larger in June than in August of 2000 and 2002. 

xi
xii
Acknowledgments 

The authors thank Jacqueline Popp Noskov, Robert Emmett, Joseph Fisher, Todd Miller, 

Douglas Reese, Paul Bentley, Todd Sandell, Rebecca Baldwin, Marcia House, Cynthia 

Anderson, Emily Locke, Tracy Wenham and the crews of the fishing vessels FV Sea Eagle and 

FV Frosti for their help with the field sampling. In addition the authors thank Cathy Potts for 

processing the June and August 2000 zooplankton samples, John Chapman for identification of 

gammarids and isopod Acanthamunnopsis milleri, Cheryl Morgan for assistance with early 

identifications of specimens, Mak Terazaki for identifying the Sagitta species from the June and 

August 2000 zooplankton samples, and Maria Parnel for identifying some of the larval and 

juvenile fishes. This study was partly funded by the U.S. GLOBEC Northeast Pacific Program 

and supported by a grant to the Cooperative Institute for Marine Resources Studies at Oregon 

State University in Corvallis. 

xiii
xiv
Introduction 

It has long been known that certain organisms have an affinity for the near-surface or 

neustonic zone in marine waters, and these organisms are called neuston (Zaitsev 1970). Some 

of these organisms are associated through morphological or physiological adaptations to the 

neustonic layer and are termed euneuston. Others occur there by chance or as a result of diel 

vertical migration patterns and are called facultative or pseudoneuston (Hempel and Weikert 

1972). Neuston are important prey items for some fish species, including juvenile salmonids 

(Oncorhynchus spp.) (Brodeur 1989). 

Although there have been many plankton surveys in the northern California Current off 

Oregon and northern California, most were focused on zooplankton or ichthyoplankton 

occupying the entire water column. Ahlstrom and Stevens (1976), however, sampled the 

ichthyoneuston from California to northern Washington. Richardson and Pearcy (1977) sampled 

for fish larvae, including those in the neuston, along one transect off of Newport, Oregon 

(lat. 44.7oN), and at a station to the north but no stations to the south. Shenker (1988) studied 

neustonic larval and juvenile fishes and Dungeness crab (Cancer magister) megalopae on the 

Newport line only. Richardson et al. (1980) collected larval fish with a bongo zooplankton net 

along the Oregon coast in March and April 1972–1975. Brodeur et al. (1987) completed the only 

comprehensive study of the entire neustonic mesozooplankton community in the northeast 

Pacific Ocean, which includes the central to southern Oregon coast, in 1984. 

U.S. Global Ocean Ecosystems Dynamics (GLOBEC) commissioned further 

oceanographic research in the northeast Pacific Ocean, including the California Current. As a 

component of the GLOBEC Northeast Pacific sampling program (Batchelder et al. 2002), 

extensive surveys were conducted in 2000 and 2002 in the northern California Current off the 

Oregon and northern California coasts. To complement the juvenile salmon and other pelagic 

fish sampling (Brodeur et al. 2004), neuston net tows were made at every trawling station. Reese 

et al. (2005) used geostatistical techniques that entail interpolation to estimate abundance 

between the data points to describe the neuston community from 2000. Instead of using 

geostatistics we analyzed neuston community data on a point-by-point basis. In addition we 

examined data from 2000 and 2002, whereas Reese et al. (2005) focused on 2000. In this 

technical memorandum our purpose is to describe the mesozooplankton species composition, 

abundance and distribution patterns, and species associations in the neuston during four cruises, 

two in each year. 
Methods 

Survey Area 

The survey area covered the continental shelf from Newport (lat. 44.7°N) to Crescent 

City, California (lat. 41.9°N) (Figure 1). Four research cruises were conducted: 

• 29 May 2000–11 June 2000, 

• 28 July 2000–12 August 2000, 

• 1 June 2002–18 June 2002, and 

• 1 August 2002–17 August 2002. 

(Hereafter these dates are referred to as June 2000, August 2000, June 2002, and August 2002, 

respectively.) During each cruise mesoscale transects were sampled first and additional stations 

were selected based on fine-scale oceanographic features such as eddies or fronts (Figure 1). 

In addition a diel study was conducted twice in 2002 to sample designated stations every 

4 hours within a 24-hour period. The purpose was to examine diel patterns in and possible 

correlations between salmonid abundance and other oceanographic parameters, including 

possible salmonid prey in the neuston. Two stations were selected for the diel study based on 

high salmonid catches during mesoscale trawling. A station on the Newport Hydroline (NH) 

denoted as NH-5 (lat. 44.7°N, long. 124.2°W) was chosen for June 2002 and a station on the 

Heceta Head (HH) transect denoted as HH-2 (lat. 44.0°N, long. 124.4°W) was chosen for August 

2002 (Figure 1). 

Sample Protocols 

Conductivity, temperature, and depth (CTD) profiles were collected at each station. An 

SBE 19 SEACAT profiler (Sea-Bird Electronics, Bellingham, Washington) was used in 2000, 

whereas an SBE 19plus SEACAT profiler, which also measured light transmittance and 

fluorometric chlorophyll, was used in 2002. Temperature, salinity, and density at 1-m depth were 

analyzed. 

Replicate samples for in vitro chlorophyll a were collected at 3-m depth with a 1-l Niskin 

water sampler (General Oceanics Inc., Miami, Florida). Samples were filtered immediately 

through grade GF/F glass fiber filters (with particle retention down to 0.7 micrometer [μm; 10-6

meter]), then frozen for analysis in the laboratory. One of the two replicates was processed, and 

the other was kept as a reserve sample. Chlorophyll a was processed using the cold-acetone 

extraction method and measured with a 10-AU fluorometer (Turner Designs Inc., Sunnyvale, 

California) (Arar and Collins 1997). 

2
Newport Hydroline

Heceta Head

Umpqua River

Five Mile River

Rogue River

Crescent City

NH-5

HH-2

126°W 125°W 124°

Longitu

CANAD

Heceta

Bank

Cape Blanco

PACIFIC OCEAN

Figure 1. Pacific Northwest coastline (right), with survey area (left). Major transects are indicated by the six horizontal lin

names of geographical features. Additional transects are not shown. Stations NH-5 (June 2002) and HH-2 (Augus

locations of a diel study. The dotted line to the west of the coastline is the 200-m depth shelf break. 

3
A neuston net with a 1-m wide by 0.3-m high mouth and 333-μm mesh was utilized for 

collection of all zooplankton samples. A General Oceanics flowmeter was attached in the mouth 

of the net to estimate the volume of water filtered during each tow. The net was towed out of the 

ship’s wake for 5 minutes at approximately 2 knots (3.7 kilometers per hour [km/h]). Upon 

retrieval the net was hosed down, and contents of the cod end were transferred to a sample jar. 

Large jellyfish1 and flotsam were rinsed with seawater to remove any attached plankton and 

discarded at sea. The sample was preserved with formalin in ambient seawater to make a 5% 

formalin solution. 

In the laboratory samples were washed with tap water over a 320-μm mesh sieve to 

remove the formalin then transferred to water. Additional extraneous contents subsequently 

were removed. To obtain displacement volumes, samples were allowed to settle overnight in 

Imhoff settling cones or graduated cylinders depending on the sample volume. Biovolumes 

(milliliter per 100 cubic meters [ml/100 m3]) were calculated from displacement volumes and 

flowmeter readings. 

Samples were transferred to a clear Pyrex dish on a white background for sorting and 

removing zooplankton greater than or equal to 5 millimeters (mm) using a lighted magnifying 

glass. This size fraction was chosen based on prey size selected by juvenile coho salmon (O. 

kisutch) and Chinook salmon (O. tshawytscha) in previous trophic analyses (Brodeur 1991, 

Schabetsberger et al. 2003). Occasionally large samples with many mesozooplankton were 

subsampled with a Folsom plankton splitter, and the counts were estimated. The 

mesozooplankton were enumerated and identified to the lowest practical taxon using a dissecting 

microscope, and life stages of the specimens were determined when possible. Completed 

samples were transferred to 70% ethanol. Counts were standardized into concentrations 

expressed as numbers per 100 m3. 

Data Analysis 

Sampling occurred most often during daylight hours, but several samples were collected 

after dark. Daytime samples are defined as having been collected between 0600 hours and 2000 

hours Pacific daylight time. Excluding the diel study samples, the numbers of nighttime samples 

per cruise were: 10 in June 2000, 4 in August 2000, 12 in June 2002, and 4 in August 2002. 

Analysis of physical parameters, chlorophyll a concentrations, zooplankton biovolumes, and 

neustonic mesozooplankton concentrations were from daytime and nighttime samples, and 

included the first sample taken during each diel study. Distribution of physical parameters and 

chlorophyll a concentrations was examined utilizing Surfer 7 software (Golden Software, Inc., 

Golden, Colorado). Because of the scattered spacing of sampling locations, point kriging, with 

anisotropy ratio and angle of 1 and 0, respectively, was selected as the gridding method for its 

flexibility. Although this generates surficial contours using interpolated values along with actual 

data points, the objective simply was to show the possible spatial patterns of these parameters. 

Six mesoscale transects were used to examine the spatial variability in neustonic 

mesozooplankton from the northern to southern ends of the survey area (Figure 1). Occasionally 

 

1

 Five species of jellyfish, egg yolk jelly (Phacellophora camtschatica), Aequorea spp., lion’s mane jelly (Cyanea 

capillata), moon jelly (Aurelia labiata), and sea nettle (Chrysaora fuscscens), were captured in the surface rope 

trawl used for catching salmonids and other fishes. 

4
a transect could not be completed during the mesoscale leg because of rough weather conditions; 

therefore, the same transect was resampled and completed during the fine-scale leg several days 

later and was used in the spatial variability analysis. This was necessary to compare the 

cross-shelf distribution of five taxa abundant and common to all six transects within a cruise and 

to reduce the effects of temporal variability. 

Species diversity was calculated using the Shannon-Wiener diversity index (H') 

(Levinton 1982, Valiela 1995, Spellerberg and Fedor 2003). The formula was: 

i

s

i

i ln' ppH

1

∑=

−= (1) 

where s is the number of species and pi is the proportion of species i. 

For statistical analysis, nighttime samples were excluded to minimize the effects of diel 

patterns commonly observed in zooplankton. Data transformations on several variables were 

necessary because of a skewed frequency distribution. Zooplankton concentrations and sample 

biovolumes were transformed with log10(x + 1). Chlorophyll a data were transformed with a 

square root. Water density, temperature, salinity, and diversity data were not transformed. To 

test for a possible difference between seasons (i.e., June vs. August) in 2000 and 2002, the 

two-sample t-test was used. One-way analysis of variance (ANOVA) was run to examine 

differences between all four cruises while considering the variations within each cruise. 

Because of a few outliers in the transformed data despite normalization, the nonparametric 

Kruskal-Wallis test was run to justify the use of ANOVA. 

Potential species associations were examined using the agglomerative hierarchical cluster 

analysis method. Data for this analysis excluded nighttime stations, samples without 

mesozooplankton, and taxa occurring in less than 5% of the stations within a cruise (i.e., 

frequency of occurrence was three in June and August 2000 and four in June and August 2002). 

The Sørensen (Bray-Curtis) distance measure and flexible beta negative 1.0 group linkage 

method were chosen for the cluster analysis, producing the least amount of chaining. 

Examination of diel patterns in the neustonic mesozooplankton included all diel samples. 

The five most abundant taxa were chosen to examine temporal variation in numerical 

concentrations. Species diversity (H') and the number of taxa collected over time also were 

analyzed. 

5
Results 

Physical Parameters 

The 1-m depth water temperature was warmer in 2000 than in 2002 (ANOVA, 

p < 0.0001), and it was warmer in June than in August. The seasonal difference in 2000 was 

not significant (t-test, p = 0.6); whereas the seasonal difference in 2002 was significant (t-test, 

p < 0.0001). For appropriate and easier comparisons between cruises, August 2000 stations west 

of long. 125.3°W were excluded from the analysis of temperature. The temperature ranges were 

10.0°C–14.6°C in June 2000, 8.7°C–16.6°C in August 2000, 7.8°C–14.2°C in June 2002, and 

8.1°C–13.3°C in August 2002 (Table 1). The coldest water was in the nearshore region and over 

Heceta Bank during all cruises (Figure 2 and Figure 3). In June 2000 the 1-m temperature was 

colder over Heceta Bank than along Cape Blanco (Figure 2). In August 2000 there was a greater 

increase in 1-m temperature from near the coast to the offshore region than during the three other 

cruises (Figure 2). The water was coldest at the most-nearshore stations on the Newport 

Hydroline (lat. 44.7°N) and Heceta Head (lat. 44.0°N) transects (Figure 2). In June 2002 the 

coldest 1-m temperatures were recorded from nearshore stations on transects from Cape Blanco 

to Crescent City (Figure 3). In August 2002 the 1-m temperatures were colder than on all three 

other cruises (Figure 3). Cold water in the nearshore region to the north of Cape Blanco 

indicated upwelling (Figure 3). Upwelling in August 2002 also occurred south of Cape Blanco 

to a greater extent than observed in June 2002 (Figure 3). In August 2000 four stations west of 

long. 125.3°W had temperatures above 17°C (Figure 2). 

The 1-m depth salinity over the continental shelf was significantly lower in June than in 

August of 2000 and 2002 (both years: t-test, p < 0.0001) (Figure 4 and Figure 5). Not including 

stations west of long. 125.3°W, 1-m salinity ranges were 28.9–33.0 practical salinity units (psu) 

in June 2000, 31.8–33.9 psu in August 2000, 29.6–33.8 psu in June 2002, and 31.7–33.7 psu in 

August 2002 (Table 1). In June of both years most stations over the shelf were between 31.0 psu 

and 33.0 psu (Figure 4 and Figure 5). In August of both years many stations over the shelf had 

greater than 33.0 psu, but some stations over Heceta Bank were between 32.0 psu and 33.0 psu 

(Figure 4 and Figure 5). 

The 1-m depth water density had a similar distribution as salinity (Figure 6 and Figure 7). 

Density ranges were 21.5–25.3 kilograms per cubic meter (kg/m3) in June 2000, 23.5–26.2 kg/m3 

in August 2000, 22.2–26.2 kg/m3 in June 2002, and 23.8–26.2 kg/m3 in August 2002 (Table 1). 

The density was higher over the shelf than offshore and higher in August than in June of both 

years (Figure 6 and Figure 7). The seasonal difference (t-test, p < 0.0001) and the interannual 

variation (ANOVA, p < 0.0001) were highly significant. 

6
Table 1. Data ranges of physical parameters and chlorophyll a by cruise. 

June 2000 August 2000 June 2002 August 20

Parameters Minimum Maximum Minimum Maximum Minimum Maximum Minimum Ma

Temperature (°C) 10.00 14.60 8.70 16.60 7.80 14.20 8.10 1Salinity (psu) 28.90 33.00 31.80 33.90 29.60 29.60 31.70 3Density (kg/m3) 21.50 25.30 23.50 26.20 22.20 26.20 23.80 2Chlorophyll a (μg/l) 0.11 10.29 0.07 14.21 0.20 45.44 0.00 3

7
126°W 125°W 124°W

Longitude

125°W 124°W

Longitude

42°N43°N44°N45°N

Latitude

OREG

CALIFOR

Cape Blanco

OREGON

CALIFORNIA

Cape Blanco

PACIFIC OCEAN PACIFIC OCEAN

Figure 2. The 1-m depth temperature (°C) in June (left) and August (right) 2000. Contour labels are oriented in an uphill d

Plus signs are locations where measurements were made. The dotted line is the 200-m depth contour. 

8
126°W 125°W 124°W

Longitude

125°W 124°W

Longitude

42°N43°N44°N45°N

Latitude

OREGO

CALIFORN

Cape Blanco

OREGON

CALIFORNIA

Cape Blanco

PACIFIC OCEAN PACIFIC OCEAN

Figure 3. The 1-m depth temperature (°C) in June (left) and August (right) 2002. Contour labels are oriented in an uphill d

Plus signs are locations where measurements were made. The dotted line is the 200-m depth contour. 

9
126°W 125°W 124°W

Longitude

125°W 124°W

Longitude

42°N43°N44°N45°N

Latitude

OREG

CALIFOR

Cape Blanco

OREGON

CALIFORNIA

Cape Blanco

PACIFIC OCEAN PACIFIC OCEAN

Figure 4. The 1-m depth salinity (psu) in June (left) and August (right) 2000. Contour labels are oriented in an uphill direc

Plus signs are locations where measurements were made. The dotted line is the 200-m depth contour. 

10
126°W 125°W 124°W

Longitude

125°W 124°W

Longitude

42°N43°N44°N45°N

Latitude

OREGO

CALIFORN

Cape Blanco

OREGON

CALIFORNIA

Cape Blanco

PACIFIC OCEAN PACIFIC OCEAN

Figure 5. The 1-m depth salinity (psu) in June (left) and August (right) 2002. Contour labels are oriented in an uphill direc

Plus signs are locations where measurements were made. The dotted line is the 200-m depth contour. 

11
126°W 125°W 124°W

Longitude

125°W 124°W

Longitude

42°N43°N44°N45°N

Latitude

OREG

CALIFOR

Cape Blanco

OREGON

CALIFORNIA

Cape Blanco

PACIFIC OCEAN PACIFIC OCEAN

Figure 6. The 1-m depth water density (kg/m3) in June (left) and August (right) 2000. Contour labels are oriented in an up

Plus signs are locations where measurements were made. The dotted line is the 200-m depth contour. 

12
126°W 125°W 124°W

Longitude

125°W 124°W

Longitude

42°N43°N44°N45°N

Latitude

CALIFORNIA

OREGON

Cape Blanco

OREG

CALIFOR

Cape Blanco

PACIFIC OCEAN PACIFIC OCEAN

Figure 7. The 1-m depth water density (kg/m3) in June (left) and August (right) 2002. Contour labels are oriented in an up

Plus signs are locations where measurements were made. The dotted line is the 200-m depth contour. 

13
Chlorophyll a

Chlorophyll a data from two stations in June 2000 and five stations in August 2000 were 

removed from analysis, because their fluorescence values exceeded the fluorometer’s detection 

limit. Chlorophyll a concentrations were lower in 2000 than in 2002 (Figure 8 and Figure 9). 

The ranges were 0.11–10.29 micrograms per liter (μg/l) in June 2000, 0.07–14.21 μg/l in August 

2000, 0.20–45.44 μg/l in June 2002, and 0.00–37.76 μg/l in August 2002 (Table 1). In June 

2000, chlorophyll a was highest on the nearshore part of the Crescent City transect (lat. 41.9°N). 

Most stations had less than 2.0 μg/l (Figure 8). In August 2000 high concentrations were 

observed over Heceta Bank and around Cape Blanco, and all but two stations west of the shelf 

break had low chlorophyll a (Figure 8). In June 2002 chlorophyll a was abundant nearshore 

north and south of Cape Blanco (Figure 9). In August 2002 Heceta Bank had the highest 

concentrations, exceeding the normally observed maximum of 20 μg/l (Figure 9). One station 

had no chlorophyll a (0.00 μg/l), because it had converted completely to phaeophytin a; whether 

this was a natural occurrence or caused by sampling or processing error was uncertain. The 

difference in chlorophyll a concentrations between June and August was significant in 2000 

(t-test, p < 0.0001) but not in 2002 (t-test, p = 0.5). The sample variation among all four cruises 

was highly significant (ANOVA, p < 0.0001). 

Biovolumes 

Biovolumes of samples were larger in June than in August of 2000 (t-test, p = 0.8) and 

2002 (t-test, p < 0.0001) (Figure 10 and Figure 11). There was a significant difference in 

biovolumes between all four cruises (ANOVA, p < 0.0001). The largest biovolume, 987.80 

ml/100 m3, was observed in June 2000 at a nearshore station at lat. 42.3°N (Figure 10). The 

maximum and mean biovolumes were higher in June than in August (Table 2). In 2000 the 

larger biovolumes were nearshore and around Cape Blanco (Figure 10). In August 2000 several 

oceanic stations had a higher biovolume than some shelf stations (Figure 10). In June 2002 

larger biovolumes were distributed widely over the shelf and offshore (Figure 11). In August 

2002 some of the offshore stations had larger biovolumes than those over the shelf, and 

biovolumes generally were lower over the northern part of Heceta Bank than elsewhere (Figure 

11). 

Mesozooplankton Abundance 

A total of 347 samples were collected, 144 taxa were identified, and 38,325 specimens 

were enumerated (Table 3). Samples were taken from 81 stations in June 2000, 77 stations in 

August 2000, 98 stations in June 2002, and 91 stations in August 2002. Of these samples, 10 in 

June 2000, 4 in August 2000, 12 in June 2002, and 4 in August 2002 were collected at night. 

Total concentrations were 1,629.91/100 m3

 in June 2000, 1,466.64/100 m3 in August 2000, 

16,057.94/100 m3

 in June 2002, and 3,267.49/100 m3 in August 2002. The difference in 

concentrations between June and August was not significant in 2000 (t-test, p = 0.5), but it was 

significant in 2002 (t-test, p = 0.0067). Interannual variations were highly significant (ANOVA, 

p < 0.0001). 

14
126°W 125°W 124°W

Longitude

125°W 124°W

Longitude

42°N43°N44°N45°N

Latitude

OREGON

CALIFORNIA

Cape Blanco

OREGON

CALIFORNIA

Cape Blanco

PACIFIC OCEAN PACIFIC OCEAN

Figure 8. Chlorophyll a (μg/l) at 3-m depth in June (left) and August (right) 2000. Contour labels are oriented in an uphill 

Plus signs are locations of chlorophyll a sample collections. The dotted line is the 200-m depth contour. 

15
126°W 125°W 124°W

Longitude

125°W 124°W

Longitude

42°N43°N44°N45°N

Latitude

OREGON

CALIFORNIA

Cape Blanco

OREGON

CALIFORNIA

Cape Blanco

PACIFIC OCEAN PACIFIC OCEAN

Figure 9. Chlorophyll a (μg/l) at 3-m depth in June (left) and August (right) 2002. Contour labels are oriented in an uphill 

Plus signs are locations of chlorophyll a sample collections. The dotted line is the 200-m depth contour. 

16
126°W 125°W 124°W

Longitude

125°W 124°W

Longitude

42°N43°N44°N45°N

Latitude

 0–<10 10–<100 100–<988

OREG

CALIFOR

Cape Blanco

OREGON

CALIFORNIA

Cape Blanco

PACIFIC OCEAN PACIFIC OCEAN

Figure 10. Biovolumes (ml/100 m3) of neuston samples in June (left) and August (right) 2000. The dotted line is the 200-m 

17
126°W 125°W 124°W

Longitude

125°W 124°W

Longitude

42°N43°N44°N45°N

Latitude

 0–<10 10–<100 100–<988

PACIFIC OCEAN PACIFIC OCEAN

OREGON

CALIFORNIA

Cape Blanco

OREGO

CALIFORN

Cape Blanco

Figure 11. Biovolumes (ml/100 m3) of neuston samples in June (left) and August (right) 2002. The dotted line is the 200-m 

18
Table 2. Biovolumes (ml/100 m3

) of neustonic mesozooplankton samples in June 

and August 2000 and 2002. SD = standard deviation. 

Cruise Minimum Maximum Mean SD 

June 2000 4.65 987.80 96.69 153.29 

August 2000 1.46 342.57 62.03 71.04 

June 2002 9.77 685.98 124.06 104.71 

August 2002 0.14 400.80 69.77 67.56 

In June 2000 decapods comprised 49.4% of the neustonic mesozooplankton taxa, 

followed by amphipods (31.3%). Dungeness crab megalopae and Oregon cancer (C. 

oregonensis) and red rock crab (C. productus) megalopae2 dominated the decapods, while 

Lycaea pulex, Vibilia australis, Themisto pacifica, and Hyperoche medusarum were the primary 

amphipods (Figure 12). The eight most abundant taxa comprised 90% of the total concentration 

(Table 3). Sample concentrations were higher nearshore than near the shelf break (Figure 13). 

Six stations beyond the shelf break had higher abundance than those around the shelf break 

(Figure 13). Three samples had no mesozooplankton. 

In August 2000 euphausiids were 27.4% of the taxa, followed by decapods (26.7%) and 

amphipods (21.3%) (Figure 12). Pacific krill (Euphausia pacifica) and Thysanoessa spinifera

dominated the euphausiids, and Dungeness crab megalopae and Oregon cancer and red rock crab 

megalopae dominated the decapods. Themisto pacifica was the most abundant amphipod, 

followed by Hyperoche medusarum (Table 3). Stations around Cape Blanco, in the northern part 

of the survey area, and far offshore had somewhat more mesozooplankton than elsewhere 

(Figure 13). Ten stations did not contain neustonic specimens in the greater than or equal to 

5-mm size fraction. 

In June 2002 decapods were 64.1% of the taxa, followed by euphausiids (26.6%) (Figure 

12). Dungeness crab megalopae, T. spinifera, then Oregon cancer and red rock crab megalopae 

dominated and comprised 87.5% of the total concentration (Table 3). All samples had 

mesozooplankton. 

In August 2002 chaetognaths were 38.5% of the taxa, followed by decapods (29.4%) and 

amphipods (16.9%) (Figure 12). Sagitta spp. were the primary chaetognaths. Dungeness crab 

megalopae and Oregon cancer and red rock crab megalopae were the most abundant decapods. 

Hyperoche medusarum was the most abundant amphipod. The 10 most abundant taxa comprised 

91.0% of total concentration (Table 4). Sample concentration was lower in the northern part of 

the survey area and moderate over Heceta Bank and over the shelf south to Cape Blanco (Figure 

14). Four samples had no neustonic mesozooplankton. 

 

2

 Megalopae of Oregon cancer crab and red rock crab are not distinguishable because morphological characteristics 

are similar. 

19
Table 3. Frequency of occurrence (FO), mean concentration (Mean, no./100 m3), and standard deviation (SD, no./100 m3) 

samples from June and August 2000 and 2002. 

June 2000 August 2000 June 2002 

Common name Scientific namea

F0 

(n=81) Mean SD 

F0 

(n=77) Mean SD 

F0 

(n=98) Mean SD 

Segmented worm Annelida Bristle worm Polychaeta 

Alciopidae (unidentified) — — — — — — 2 0.54 0.02 Autolytus sp. — — — — — — 3 0.76 0.46 Nereis sp. — — — 2 1.30 1.21 — — — 

Syllidae (unidentified) — — — — — — 1 0.56 — Tomopteris sp. — — — 2 7.55 9.17 21 2.64 3.50 Travisiopsis sp. — — — — — — 1 0.67 — 

Mollusc Mollusca Gastropod Gastropoda Pyramid clio sea butterfly Clio pyramidata — — — 3 1.42 1.19 1 10.05 — Clio sea butterfly Clio sp. — — — 3 2.25 0.93 — — — Sea butterfly Clionidae (unidentified) 1 0.47 — — — — 3 0.61 0.07 Sea slug Dendronotus sp. — — — 1 5.20 — — — — Nudibranch Eolidoidea (unidentified) — — — 1 0.54 — — — — Naked pteropod Gymnosomata (unidentified) — — — — — — — — — Octopus, squid Cephalopoda 

Chiroteuthis sp. — — — 1 0.38 — — — — 

Market squid Loligo opalescens —— — — — — — — 

— 

Arthropod Arthropoda Crustacean Crustacea Copepod Copepoda Parasitic copepod 

Copepoda (unidentified parasitic) — — — — — — 1 0.65 — Eucalanus sp. — — — 1 0.49 — 32 5.75 12.85 Euchaeta spp. — — — 2 1.26 1.25 — — — Neocalanus cristatus — — — — — — 10 12.76 21.37 Neocalanus plumchrus — — — — — — 5 1.31 0.71 

20
Table 3 continued. Frequency of occurrence (FO), mean concentration (Mean, no./100 m3), and standard deviation (SD, no

present in samples from June and August 2000 and 2002. 

June 2000 August 2000 June 2002 

Common name Scientific namea

F0 

(n=81) Mean SD 

F0 

(n=77) Mean SD 

F0 

(n=98) Mean SD 

Cumacean Cumacea 

Diastylopsis sp. —

—

—

— — 

— 1 2.07

—

Hemilamprops spp. —

—

—

— — 

— 2 9.61 5.79

Oxyurostylis sp.

—

—

—

— — 

— 1 0.69

—

Opossum shrimp Mysida 

Alienacanthomysis macropsis 3 0.71 0.52 1 11.47 

— 3 0.92 0.32 

Archaeomysis grebnitzkii 1 0.43

— 1 4.47 

—

—

—

—

Neomysis kadiakensis 

—

—

— 1 1.56 

—

—

—

— 

Pacifacanthomysis nephrophthalma —— — — — — — — 

—— — — — — — — 

1 3

1 0

— 

Pill bug Isopoda 

Acanthamunnopsis milleri — Excirolana linguifrons 

—

—

— 1 0.45 

—

—

—

—

Idotea fewkesi 10 2.74 2.80 5 1.09 0.68 2 1.55 0.16Idotea rufescens 

—

—

— 2 1.03 0.83

—

—

—

Eelgrass isopod Pentidotea resecata 0.4

—

— — 

—

—

—

—

Vosnesensky’s isopod Pentidotea wosnesenskii 1 0.40

— 2 0.76 0.45 1 0.60

—

Amphipod Amphipoda Gammarid Gammaridea 

Allorchestes angusta 8 0.76 0.64 4 0.58 0.34 7 1.22 0.83 Ampithoe sp.

—

—

—

— — 

— 1 0.53

—

Aruga oculata 

—

—

— 1 0.45 

—

—

—

—

Atylus tridens 3 0.40 0.03 18 2.66 4.19 8 1.33 1.00 Calliopius cf C. columbianus 1 0.40

— 2 8.02 10.71 14 2.79 4.78 

Eobrolgus chumashi 

—

—

—

— — 

—

—

—

— 

Eogammarus confervicolus 0.4

—

— — 

—

—

—

—

21
Table 3 continued. Frequency of occurrence (FO), mean concentration (Mean, no./100 m3), and standard deviation (SD, no

present in samples from June and August 2000 and 2002. 

June 2000 August 2000 June 2002 

Common name Scientific namea

F0 

(n=81) Mean SD 

F0 

(n=77) Mean SD 

F0 

(n=98) Mean SD 

Gammaridea continued 

Gnathopleustes simplex 1 0.46

—

— — 

—

—

—

—

Heterophoxus sp. —

—

—

— — 

— 1 1.26

—

Hyale anceps 

—

—

—

— — 

— 1 0.54

—

Hyale frequens 5 0.45 0.02 10 2.50 3.45 1 0.57

—

Microjassa sp. 

—

—

— 1 0.46 

—

—

—

—

Monoculodes sp.

—

—

—

— — 

— 1 0.63

—

Peramphithoe humeralis 1 0.47

— 4 2.76 2.73

—

—

—

Hyperiid Hyperiidea 

Brachyscelus crusculum 11 0.69

—

— — 

— 1 0.56

—

Hyperia medusarum 5 0.57 0.25 6 2.60 3.92 6 1.57 1.02 Hyperoche medusarum 22 1.48 1.28 28 1.77 1.94 42 4.90 9.55 Lycaea pulex 25 11.35 45.29

— — 

—

—

—

—

Paraphronima crassipes 

— — 

— 1 0.44 

—

—

—

—

Primno brevidens 

—

—

— 1 0.66 

—

—

—

—

Primno macropa 

—

—

—

— — 

— 1 0.59

—

Streetsia challengeri —— — — — — — — 

1 6

— 

Themisto pacifica 6 10.14 22.24 10 13.27 20.02 10 4.20 4.94 Tryphana malmi 4 1.38 1.15

— — 

— 8 2.16 2.50 

Vibilia australis 18 6.20 19.40

— — 

—

—

—

—

Hyperiidea (unidentified) 2 0.41 0.01 1 0.38 

—

—

—

—

Skeleton shrimp Caprellidea 

Caprella ferrea 0.4

—

— — 

—

—

—

—

Caprella incisa 

—

—

— 1 10.40 

—

—

—

—

Caprellidea (unidentified) 

—

—

— 1 0.54 

—

—

—

—

Krill Euphausiacea Pacific krill Euphausia pacifica 30 1.69 2.13 24 10.34 33.44 22 11.14 25.48 

Thysanoessa inspinata 1 1.31

— 1 0.46 

—

—

—

— 

22
Table 3 continued. Frequency of occurrence (FO), mean concentration (Mean, no./100 m3), and standard deviation (SD, no

present in samples from June and August 2000 and 2002. 

June 2000 August 2000 June 2002 

Common name Scientific namea

F0 

(n=81) Mean SD 

F0 

(n=77) Mean SD 

F0 

(n=98) Mean SD 

Euphausiacea continued 

Thysanoessa raschii —— — — — — — — 

1 0

—— — — — — — — 

— 

Thysanoessa spinifera 13 1.17 1.72 17 9.07 20.04 40 100.79 587.84 

Crab, lobster, prawn, shrimp Decapoda Hermit crab, sand crab, mole crab, porcelain crab, squat lobster, stone crab Anomura Tubeworm hermit crab Discorsopagurus schmitti 

—

—

—

— — 

— 6 0.95 0.99

Pacific sand crab Emerita analoga 

—

—

—

— — 

— 1 0.94

—

Alaskan hermit crab Pagurus ochotensis 1 0.43

— 1 0.52 

— 2 1.17 0.96 

Pagurus sp. C [sensu 

Lough 1975)]

—

—

—

— — 

— 2 1.37 0.86 

True crab Brachyura Pacific rock crab and graceful crab 

Cancer antennarius and 

C. gracilis 

—

—

—

— — 

— 7 2.37 1.60 

Dungeness crab Cancer magister 34 14.47 29.24 13 16.97 31.04 67 116.58 357.27 Oregon cancer crab and red rock crab 

Cancer oregonensisand C. productus 27 11.26 25.39 7 18.79 40.85 34 64.98 155.78 

Cancrid crab Cancer sp. 1 0.47

—

— — 

— 4 0.73 0.17 

Grooved mussel crab Fabia subquadrata 

—

—

—

— — 

— 6 6.27 7.06

Purple shore crab Hemigrapsus nudus 0.4

—

— — 

—

—

—

—

Shrimp CarideaSnapping shrimp Alpheidae (unidentified) 

—

—

— 2 0.75 0.32

—

—

—

Crangon shrimp Crangon sp. — 

23
Table 3 continued. Frequency of occurrence (FO), mean concentration (Mean, no./100 m3), and standard deviation (SD, no

present in samples from June and August 2000 and 2002. 

June 2000 August 2000 June 2002 

Common name Scientific namea

F0 

(n=81) Mean SD 

F0 

(n=77) Mean SD 

F0 

(n=98) Mean SD 

Caridea continued

Sand shrimp, bay shrimp 

Crangonidae (unidentified) 

—

—

—

— — 

— 10 6.02 14.14 

Crangonidae sp. 

Ab 1 3.92

— 2 0.48 0.05 8 2.45 2.82 

Broken-back shrimp 

Hippolytidae (unidentified) 3 1.19 0.74 5 7.67 16.11 12 7.85 11.97 Pandalus spp.

—

—

—

— — 

— 6 1.42 1.25

Ghost shrimp, mud shrimp, sponge shrimp Thalassinidea Ghost shrimp Neotrypaea californiensis

—

—

—

— — 

— 7 2.30 1.81 

Sergestoidea 

Sergestidae (unidentified)

—

—

—

— — 

—

—

—

— 

Insect Insecta Beetle, weevil Coleoptera (unidentified) 4 0.41 0.03 5 0.80 0.76 3 0.77 0.27 True fly Diptera (unidentified) 12 0.86 0.71 3 0.52 0.06 11 1.13 1.24 True bug Hemiptera (unidentified) 1 0.40

— 3 0.46 0.07 1 0.68

— 

Cicada, leafhopper, aphid Homoptera (unidentified) 1 0.40

— 1 0.46 

—

—

—

—

Ant, bee, wasp, sawfly Hymenoptera (unidentified) 1 0.37

— 3 0.68 0.35 1 2.04

— 

Butterfly, moth Lepidoptera (unidentified) 

—

—

— 2 0.49 0.07 5 0.72 0.20 

Lacewing, ant lion, mantispid, etc. Neuroptera (unidentified) 8 1.01 0.92

— — 

— 12 1.49 1.35 

Dragonfly, damselfly Odonata (unidentified) 

—

—

— 1 0.51 

—

—

—

—

Stonefly Plecoptera (unidentified) 

—

—

— 1 0.46 

—

—

—

—

Caddis fly, water moth Trichoptera (unidentified) 1 0.37

—

— — 

—

—

—

—

Insecta (unidentified) 1 0.42

—

— — 

—

—

—

—

24
Table 3 continued. Frequency of occurrence (FO), mean concentration (Mean, no./100 m3), and standard deviation (SD, no

present in samples from June and August 2000 and 2002. 

June 2000 August 2000 June 2002 

Common name Scientific namea

F0 

(n=81) Mean SD 

F0 

(n=77) Mean SD 

F0 

(n=98) Mean SD 

Arrowworm Chaetognatha 

Eukrohnia sp. 

—

—

—

— — 

— 10 3.32 6.65 

Sagitta elegans 1 108.91

— 7 1.22 1.77

—

—

—

Sagitta euneritica 

—

—

— 3 36.54 61.98

—

—

—

Sagitta minima 0.42

— 1 66.53 

—

—

—

—

Sagitta scrippsae

—

—

— 4 1.31 0.52

—

—

—

Sagitta spp. 

—

—

—

— — 

— 57 8.87 16.39 

Chaetognatha (unidentified) 

—

—

— 1 0.52 

— 13 5.47 6.57 

Chordate Chordata Bony fish Osteichthyes Poacher Agonidae Blacktip poacher Xeneretmus latifrons 

—

—

—

— — 

— 1 0.62

—

Sand lance Ammodytidae Pacific sand lance Ammodytes hexapterus 

—

—

—

— — 

— 5 2.28 2.80

Sablefish Anoplopomatidae Sablefish Anoplopoma fimbria 

—

—

—

— — 

— 2 0.56 0.07

Ronquil Bathymasteridae Ronquil Bathymaster sp.

—

—

—

— — 

— 1 1.26

—

Northern ronquil Ronquilus jordani 

—

—

—

— — 

— 2 0.83 0.42

Brotula Bythitidae Red brotula Brosmophycis marginata 

—

—

—

— — 

— 2 1.55 1.55 

Clupeid Clupeidae Pacific herring Clupea pallasii 

—

—

— 9 0.68 0.43 1 0.63

—

Clupeidae (unidentified) 

—

—

—

— — 

— 1 0.63

—

Sculpin Cottidae Padded sculpin Artedius fenestralis 

—

—

—

— — 

— 1 1.26

—

Calico sculpin Clinocottus embryum 1 3 — — — — — — 

0.4 — 

25
Table 3 continued. Frequency of occurrence (FO), mean concentration (Mean, no./100 m3), and standard deviation (SD, no

present in samples from June and August 2000 and 2002. 

June 2000 August 2000 June 2002 

Common name Scientific namea

F0 

(n=81) Mean SD 

F0 

(n=77) Mean SD 

F0 

(n=98) Mean SD 

Cottidae continued 

Coastrange sculpin Cottus aleuticus 

—

—

—

— — 

— 1 0.63

—

Brown Irish lord Hemilepidotus spinosus 1 0.47

—

— — 

— 7 1.28 0.90

Slim sculpin Radulinus asprellus 1 7

—— — — — — — — 

0.4

—

— — 

—

—

—

—

Puget Sound sculpin Ruscarius meanyi 

—

—

—

— — 

— 3 1.57 0.85

Cabezon Scorpaenichthys marmoratus 1 0.69

— 2 0.47 0.08 9 1.38 1.95 

Anchovy Engraulidae Northern anchovy Engraulis mordax 

—

—

—

— — 

— 3 0.61 0.17 

Cod, haddock Gadidae Pacific tomcod Microgadus proximus 

—

—

—

— — 

— 2 0.78 0.44

Stickleback Gasterosteidae Threespine stickleback Gasterosteus aculeatus — Greenling Hexagrammidae Kelp greenling Hexagrammos decagrammus 1 0.39

—

— — 

— 2 1.85 1.85

Lingcod Ophiodon elongatus 

—

—

—

— — 

— 1 0.56

—

Snailfish Liparidae Slimy snailfish Liparis mucosus 

—

—

—

— — 

— 1 0.63

—

Lanternfish Myctophidae Northern lampfish Stenobrachius leucopsarus 

—

—

—

— — 

— 2 0.52 0.03 

Blue lanternfish Tarletonbeania crenularis 1 0.69

— 5 4.56 3.40

—

—

—

Myctophidae (unidentified) 1 0.45

—

— — 

—

—

—

—

Smelt Osmeridae (unidentified) 1 0.43

— 1 2.16 

— 7 1.06 1.22 

Barracudina Paralepididae Slender barracudina Lestidiops ringens 

—

—

— 1 0.42 

—

—

—

—

26
Table 3 continued. Frequency of occurrence (FO), mean concentration (Mean, no./100 m3), and standard deviation (SD, no

present in samples from June and August 2000 and 2002. 

June 2000 August 2000 June 2002 

Common name Scientific namea

F0 

(n=81) Mean SD 

F0 

(n=77) Mean SD 

F0 

(n=98) Mean SD 

Righteye flounder Pleuronectidae Rex sole Glyptocephalus zachirus —

—

—

— — 

— 2 0.72 0.31

Starry flounder Platichthys stellatus 

—

—

—

— — 

— 1 0.56

—

Sand sole Psettichthys melanostictus 1 0.43

—

— — 

— 1 0.60

—

Fathead Psychrolutidae Blob sculpin Psychrolutes phrictus 

— — — — — — — — — 

Saury Scomberesocidae Pacific saury Cololabis saira 28 2.79 3.30 17 1.67 2.43

—

—

—

Scorpionfish Scorpaenidae Pacific ocean perch Sebastes alutus 

—

—

— 1 1.08 

—

—

—

—

Splitnose rockfish Sebastes diploproa 

—

—

— 3 4.66 1.37

—

—

—

Yellowtail rockfish Sebastes flavidus 1 0.69

—

— — 

— 2 1.31 0.83 

Shortbelly rockfish Sebastes jordani 

— — 

—

— — 

— 1 0.62

—

Canary rockfish Sebastes pinniger 

—

—

—

— — 

— 1 0.50

— 

Bank rockfish Sebastes rufus 1 0.50

— 1 0.33 

— 2 0.49 0.00

Sharpchin rockfish Sebastes zacentrus 

—

—

— 4 1.79 1.72

—

—

—

Rockfish Sebastes spp.

—

—

—

— — 

— 4 0.62 0.17

Prickleback Stichaeidae High cockscomb Anoplarchus purpurescens 

—

—

—

— — 

— 1 0.45

—

Stichaeidae (unidentified) 

—

—

—

— — 

— 2 0.59 0.07

Osteichthyes (unidentified) 

—

—

— 2 0.54 0.12 1 0.60

— 

a Indentation patterns do not follow strict taxonomic classification. Taxonomic levels are indented to indicate a subcategory that is ide

recognizable scientific name. Within the lowest subcategories, species and other taxa with data are indented the same. This resulted 

indented the same between high taxonomic levels such as phyla.

b A distinct single species in the family Crangonidae that could not be identified to genus or species with the available taxonomic keys

(unidentified) has one or more unidentified species and does not include Crangonidae sp. A. 

27
June 2002

Decapoda

64.1%

Euphausiacea

26.6%

Other

0.9%

Chaetognatha

3.8%

Amphipoda

2.1%

Osteichthyes

0.5%

Copepoda

2.0%

August 2002

Chaetognatha

38.5%

Amphipoda

16.9%

Decapoda

29.4%

Copepoda

7.2%

Euphausiacea

5.9%

Osteichthyes

0.5% Other

1.7%

June 2000

Amphipoda

31.3%

Decapoda

49.4%

Chaetognatha

6.7%

Osteichthyes

5.1%

Other

3.3% Euphausiacea

4.1%

August 2000

Euphausiacea

27.4%

Amphipoda

21.3%

Chaetognatha

12.9%

Decapoda

26.7%

Osteichthyes

5.7%

Other

5.7%

Copepoda

0.2%

Figure 12. Composition of major neustonic mesozooplankton taxonomic groups collected during four 

cruises. 

Copepoda 

Copepods comprised 0.2% of total abundance in August 2000, 2.0% in June 2002, and 

7.2% in August 2002 (Figure 12). No copepods greater than or equal to 5 mm were in any June 

2000 samples. Eucalanus sp. and Neocalanus cristatus were more abundant and occurred more 

frequently than other copepods (Table 3). Eucalanus sp. sample concentration was 0.49/100 

m3

in August 2000 and ranges were 0.49–69.59/100 m3 (mean = 5.75/100 m3) in June 2002 and 

0.45–40.40/100 m3

 (mean = 8.19/100 m3) in August 2002. Neocalanus cristatus concentration 

ranges were 0.49–67.52/100 m3 (mean = 12.76/100 m3) in June 2002 and 0.50–11.88/100 m3

(mean = 3.60/100 m3

) in August 2002. This species was absent in the 2000 samples. 

 

28
Table 4. Ten most abundant neustonic mesozooplankton taxa in June and August 2000 and 2002. 

Cruise Common name Scientific name 

Total 

concentration 

(no./100 m3

) 

Cumulative

% of total 

June 2000 Dungeness crab Cancer magister 491.81 30.17 

Oregon cancer crab 

and red rock crab 

Cancer oregonensis 

and C. productus 303.93 48.82 

Lycaea pulex 283.71 66.23 

Vibilia australis 111.68 73.08 

Sagitta elegans 108.91 79.76 

Pacific saury Cololabis saira 78.20 84.56 

Themisto pacifica 60.86 88.29 

Pacific krill Euphausia pacifica 50.80 91.41 

Hyperoche medusarum 32.59 93.41 

Idotea fewkesi 27.43 95.09 

August 2000 Pacific krill Euphausia pacifica 248.14 16.92 

Dungeness crab Cancer magister 220.59 31.96 

Thysanoessa spinifera 154.16 42.47 

Themisto pacifica 132.66 51.52 

Oregon cancer crab 

and red rock crab 

Cancer oregonensis 

and C. productus 131.56 60.49 

Sagitta euneritica 109.61 67.96 

Sagitta minima 66.53 72.50 

Hyperoche medusarum 49.50 75.87 

Atylus tridens 47.93 79.14 

Hippolytidae (unidentified) 38.34 81.75 

June 2002 Dungeness crab Cancer magister 7,811.04 48.64 

Thysanoessa spinifera 4,031.59 73.75 

Oregon cancer crab 

and red rock crab 

Cancer oregonensis 

and C. productus 2,209.41 87.51 

Sagitta spp. 505.76 90.66 

Pacific krill Euphausia pacifica 245.02 92.18 

Hyperoche medusarum 205.97 93.47 

Eucalanus sp. 183.85 94.61 

Neocalanus cristatus 127.55 95.41 

Hippolytidae (unidentified) 94.20 95.99 

Chaetognatha (unidentified) 71.17 96.44 

29
Table 4 continued. Ten most abundant neustonic mesozooplankton taxa during the June and August 2000 

and 2002 cruises. 

Cruise Common name Scientific name 

Total 

concentration 

(no./100 m3

) 

Cumlative

% of total 

August 2002 Sagitta spp. 777.43 23.79 

Dungeness crab Cancer magister 584.06 41.67 

Chaetognatha 

(unidentified) 

394.45 53.74 

Oregon cancer crab 

and red rock crab

Cancer oregonensis 

and C. productus 330.86 63.87 

Hyperoche medusarum 221.43 70.64 

Eucalanus sp. 204.79 76.91 

Eobrolgus chumashi 169.94 82.11 

Thysanoessa spinifera 127.79 86.02 

Themisto pacifica 95.46 88.94 

Eukrohnia sp. 69.29 91.06 

Amphipoda 

Amphipods were the second largest major taxon in June 2000. Fourteen gammarid and 

11 hyperiid species were identified (Table 3). In 2000 and 2002, Allorchestes angusta, Atylus 

tridens, and Calliopius cf C. columbianus were the most common gammarids. Hyale frequens

was common only in 2000. All but one of the remaining gammarid species occurred once (Table 

3). During all four cruises gammarids were caught over the shelf and beyond the shelf break. 

Eobrolgus chumashi was the seventh most abundant gammarid in August 2002, and it was 

collected from two shelf stations at lat. 43.1°N with concentrations of 167.09 and 2.86/100 m3. 

Hyperiids were present in 56% of the June 2000, 48% of the August 2000, 49% of the 

June 2002, and 66% of the August 2002 samples. Hyperoche medusarum and T. pacifica were 

the most abundant hyperiids. 

Hyperoche medusarum concentration ranges were 0.40–4.67/100 m3 (mean = 1.48/100 

m3

) in June 2000, 0.42–7.95/100 m3 (mean = 1.77/100 m3) in August 2000, 0.49–44.47/100 m3

(mean = 4.90/100 m3

) in June 2002, and 0.46–32.88/100 m3 (mean = 3.82/100 m3) in August 

2002 (Table 3). Hyperoche medusarum distribution was scattered in 2000 and widespread in 

2002 (Figure 15 and Figure 16). 

Themisto pacifica concentration ranges were 0.47–55.51/100 m3

 (mean = 10.14/100 m3) 

in June 2000, 0.33–54.31/100 m3

 (mean = 13.27/100 m3) in August 2000, 0.53–14.54/100 m3

(mean = 4.20/100 m3

) in June 2002, and 0.46–86.43/100 m3 (mean = 9.55/100 m3) in August 

2002 (Table 3). In 2000 stations with the highest T. pacifica concentrations were far offshore, 

whereas in 2002 they were over the shelf (Figure 17 and Figure 18). 

30
126°W 125°W 1

Longitude

125°W 124°W

Longitude

42°N43°N44°N45°N

Latitude

CA

Cape Bla

OREGON

CALIFORNIA

Cape Blanco

 0.001–<1 1–<10 10–<100 100–<1,000 1,000–<4,000

PACIFIC OCEAN PACIFIC OCEAN

Figure 13. Distribution of neustonic mesozooplankton concentrations (no./100 m3) in June (left) and August (right) 2000. 

The dotted line is the 200-m depth contour. 

31
126°W 125°W 1

Longitude

125°W 124°W

Longitude

42°N43°N44°N45°N

Latitude

 0.001–<1 1–<10 10–<100 100–<1,000 1,000–<4,000

PACIFIC OCEAN PACIFIC OCEAN

C

Cape Bla

OREGON

CALIFORNIA

Cape Blanco

Figure 14. Distribution of neustonic mesozooplankton concentrations (no./100 m3) in June (left) and August (right) 2002. 

The dotted line is the 200-m depth contour. 

32
126°W 125°W 

Longitude

125°W 124°W

Longitude

42°N43°N44°N45°N

Latitude

C

Cape Bla

OREGON

CALIFORNIA

Cape Blanco

 0.001–<1 1–<10 10–<45

PACIFIC OCEAN PACIFIC OCEAN

Figure 15. Abundance and distribution of Hyperoche medusarum concentrations (no./100 m3) in June (left) and August (ri

signs represent zero concentration. The dotted line is the 200-m depth contour. 

33
126°W 125°W 1

Longitude

125°W 124°W

Longitude

42°N43°N44°N45°N

Latitude

 0.001–<1 1–<10 10–<45

CA

Cape Blan

OREGON

CALIFORNIA

Cape Blanco

PACIFIC OCEAN PACIFIC OCEAN

Figure 16. Abundance and distribution of Hyperoche medusarum concentrations (no./100 m3) in June (left) and August (ri

signs represent zero concentration. The dotted line is the 200-m depth contour. 

34
126°W 125°W 1

Longitude

125°W 124°W

Longitude

42°N43°N44°N45°N

Latitude

CA

Cape Bla

OREGON

CALIFORNIA

Cape Blanco

 0.001–<1 1–<10 10–<87

PACIFIC OCEAN PACIFIC OCEAN

Figure 17. Abundance and distribution of T. pacifica concentrations (no./100 m3) in June (left) and August (right) 2000. P

zero concentration. The dotted line is the 200-m depth contour. 

35
126°W 125°W 1

Longitude

125°W 124°W

Longitude

42°N43°N44°N45°N

Latitude

 0.001–<1 1–<10 10–<87

CA

Cape Bla

OREGON

CALIFORNIA

Cape Blanco

PACIFIC OCEAN PACIFIC OCEAN

Figure 18. Abundance and distribution of T. pacifica concentrations (no./100 m3) in June (left) and August (right) 2002. P

zero concentration. The dotted line is the 200-m depth contour. 

36
In June 2000 Lycaea pulex (range = 0.36–227.59/100 m3

) and V. australis (range = 

0.36–83.26/100 m3

) were the most common hyperiids. In all four surveys Hyperia medusarum

and Tryphana malmi also were caught several times but at lower concentrations than T. pacifica

(Table 3). Remaining hyperiid species were collected only once (Table 3). 

Caprella ferrea, C. incisa, and an unidentified caprellid occurred once in 2000. No 

caprellids were found in the 2002 samples (Table 3). 

Euphausiacea 

Pacific krill and T. spinifera were the most frequent and abundant euphausiids for all 

cruises. Thysanoessa inspinata and T. raschii also were present. Only one T. raschii was caught 

during all four cruises; it was collected in August 2002 from a station nearest to shore at 

lat. 42.95°N. 

Pacific krill was more frequent than T. spinifera in 2000, whereas it was less frequent 

than T. spinifera in 2002 (Table 3). Life stages of furcilia to adults were present. Pacific krill 

concentration ranges were 0.37–7.94/100 m3 (mean = 1.69/100 m3) in June 2000, 

0.42–162.70/100 m3 (mean = 10.34/100 m3) in August 2000, 0.43–101.14/100 m3 (mean = 

11.14/100 m3

) in June 2002, and 0.51–19.15/100 m3 (mean = 3.60/100 m3) in August 2002 

(Table 3). Pacific krill distribution mainly was scattered in all cruises (Figure 19 and Figure 20). 

In August 2000 it was found mainly beyond the shelf break (Figure 19). 

Thysanoessa spinifera concentrations ranges were 0.37–6.81/100 m3 (mean = 

1.17/100 m3) in June 2000, 0.44–64.80/100 m3 (mean = 9.07/100 m3) in August 2000, 

0.41–3,722.73/100 m3

 (mean = 100.79/100 m3) in June 2002, and 0.42–40.76/100 m3 (mean = 

3.28/100 m3) in August 2002 (Table 3). Thysanoessa spinifera was collected mainly over the 

shelf, and it rarely was caught beyond the shelf break (Figure 21 and Figure 22). In August 2000 

and during both 2002 cruises, T. spinifera appeared to be more common and abundant south of 

Heceta Bank (Figure 21 and Figure 22). 

Decapoda 

Decapods comprised a large portion of the survey-wide species composition (Figure 12). 

Dungeness crab megalopae and Oregon cancer and red rock crab megalopae were the most 

abundant and frequent decapods in all four cruises. Dungeness crab megalopae concentration 

ranges were 0.39–147.46/100 m3

 (mean = 14.47/100 m3) in June 2000, 0.44–93.34/100 m3 

(mean = 16.97/100 m3) in August 2000, 0.43–2,572.30/100 m3 (mean = 116.58/100 m3) in June 

2002, and 0.49–175.68/100 m3

 (mean = 15.79/100 m3) in August 2002 (Table 3). Dungeness 

crab megalopae were more abundant in June than in August of both years (Figure 23 and Figure 

24). The distribution in June 2000 was mainly nearshore (Figure 23). In August 2000 most 

specimens were collected from north of Heceta Bank (Figure 23). In June 2002 the distribution 

was across the shelf (Figure 24). The August 2002 distribution also was shelf wide with most 

specimens collected from the Heceta Bank region (Figure 24). 

Oregon cancer and red rock crab megalopae generally were more abundant nearshore 

than offshore in June of both years (Figure 25 and Figure 26). It was less frequent and more 

scattered in August (Figure 25 and Figure 26). Concentration ranges were 0.44–131.22/100 m3 

37
126°W 125°W 1

Longitude

125°W 124°W

Longitude

42°N43°N44°N45°N

Latitude

C

Cape Bla

OREGON

CALIFORNIA

Cape Blanco

 0.001–<1 1–<10 10–<100 100–<163

PACIFIC OCEAN PACIFIC OCEAN

Figure 19. Abundance and distribution of Pacific krill concentrations (no./100 m3) in June (left) and August (right) 2000. 

zero concentration. The dotted line is the 200-m depth contour. 

38
126°W 125°W 1

Longitude

125°W 124°W

Longitude

42°N43°N44°N45°N

Latitude

 0.001–<1 1–<10 10–<100 100–<163

C

Cape Bla

OREGON

CALIFORNIA

Cape Blanco

PACIFIC OCEAN PACIFIC OCEAN

Figure 20. Abundance and distribution of Pacific krill concentrations (no./100 m3) in June (left) and August (right) 2002. 

zero concentration. The dotted line is the 200-m depth contour. 

39
126°W 125°W 

Longitude

125°W 124°W

Longitude

42°N43°N44°N45°N

Latitude

C

Cape Bl

OREGON

CALIFORNIA

Cape Blanco

 0.001–<1 1–<10 10–<100 100–<1,000 1,000–<3,723

PACIFIC OCEAN PACIFIC OCEAN

Figure 21. Abundance and distribution of T. spinifera concentrations (no./100 m3) in June (left) and August (right) 2000. P

zero concentration. The dotted line is the 200-m depth contour. 

40
126°W 125°W 1

Longitude

125°W 124°W

Longitude

42°N43°N44°N45°N

Latitude

 0.001–<1 1–<10 10–<100 100–<1,000 1,000–<3,723

CA

Cape Bla

OREGON

CALIFORNIA

Cape Blanco

PACIFIC OCEAN PACIFIC OCEAN

Figure 22. Abundance and distribution of T. spinifera concentrations (no./100 m3) in June (left) and August (right) 2002. P

zero concentration. The dotted line is the 200-m depth contour. 

41
126°W 125°W 1

Longitude

125°W 124°W

Longitude

42°N43°N44°N45°N

Latitude

 0.001–<1 1–<10 10–<100 100–<1,000 1,000–<2,573

CA

Cape Blan

OREGON

CALIFORNIA

Cape Blanco

PACIFIC OCEAN PACIFIC OCEAN

Figure 23. Abundance and distribution of Dungeness crab megalopae concentrations (no./100 m3) in June (left) and Augus

Plus signs represent zero concentration. The dotted line is the 200-m depth contour. 

42
126°W 125°W 1

Longitude

125°W 124°W

Longitude

42°N43°N44°N45°N

Latitude

 0.001–<1 1–<10 10–<100 100–<1,000 1,000–<2,573

OREGON

CALIFORNIA

Cape Blanco

C

Cape Bla

PACIFIC OCEAN PACIFIC OCEAN

Figure 24. Abundance and distribution of Dungeness crab megalopae concentrations (no./100 m3) in June (left) and Augus

Plus signs represent zero concentration. The dotted line is the 200-m depth contour. 

43
126°W 125°W 1

Longitude

125°W 124°W

Longitude

42°N43°N44°N45°N

Latitude

CA

Cape Bla

OREGON

CALIFORNIA

Cape Blanco

 0.001–<1 1–<10 10–<100 100–<772

PACIFIC OCEAN PACIFIC OCEAN

Figure 25. Abundance and distribution of Oregon cancer crab and red rock crab megalopae concentrations (no./100 m3) in 

August (right) 2000. Plus signs represent zero concentration. The dotted line is the 200-m depth contour. 

44
126°W 125°W 1

Longitude

125°W 124°W

Longitude

42°N43°N44°N45°N

Latitude

 0.001–<1 1–<10 10–<100 100–<772

CA

Cape Bla

OREGON

CALIFORNIA

Cape Blanco

PACIFIC OCEAN PACIFIC OCEAN

Figure 26. Abundance and distribution of Oregon cancer crab and red rock crab megalopae concentrations (no./100 m3) in 

August (right) 2002. Plus signs represent zero concentration. The dotted line is the 200-m depth contour. 

45
(mean = 11.26/100 m3

) in June 2000, 0.45–110.83/100 m3 (mean = 18.79/100 m3) in August 

2000, 0.47–771.27/100 m3

 (mean = 64.98/100 m3) in June 2002, and 0.55–271.98/100 m3 (mean 

= 27.57/100 m3) in August 2002 (Table 3). 

In addition to Dungeness crab megalopae and Oregon cancer and rock crab megalopae, 

there were 16 other decapod taxa. These included pagurid zoeae and megalopae, three additional 

species of brachyuran crabs, caridean shrimp zoeae and megalopae, ghost shrimps, and pelagic 

sergestid shrimps (Table 3). All taxa were more frequent and more abundant in June 2002 than 

other periods (Table 3). Crangonids and hippolytids dominated in frequency and mean 

abundance (Table 3). 

Chaetognatha 

Chaetognaths were collected during all four sampling periods. Chaetognaths were the 

most abundant taxon in August 2002 (Figure 12). Sagitta spp. were the most common 

chaetognaths. In the 2000 samples four Sagitta species were identified: S. elegans, S. euneritica, 

S. minima, and S. scrippsae. In the 2002 samples it was not feasible to identify Sagitta to 

species; therefore, all Sagitta species were grouped together for analysis of chaetognaths. 

Sagitta spp. were more widespread and more frequent in 2002 than in 2000 (Figure 27 and 

Figure 28). Sagitta spp. concentration ranges were 0.42–108.91/100 m3

 (mean = 54.67/100 m3) 

in June 2000, 0.44–174.63/100 m3

 (mean = 17.27/100 m3) in August 2000, 0.39–97.64/100 m3

(mean = 8.87/100 m3) in June 2002, and 0.43–177.48/100 m3 (mean = 15.24/100 m3) in August 

2002 (Table 3). In addition to Sagitta spp., Eukrohnia sp. and unidentified chaetognaths also 

were present. Eukrohnia sp. was present only in 2002 with a sample concentration range of 

0.49–34.70/100 m3. 

Osteichthyes 

Larval and juvenile fish were caught during all four surveys. A total of 42 taxa in 20 

families was identified (Table 3). The number of taxa per cruise was 12 in June 2000, 11 in 

August 2000, 31 in June 2002, and 10 in August 2002. The fish comprised 5.1 % of the 

taxonomic composition in June 2000, 5.7% in August 2000, 0.5% in June 2002, and 0.5% in 

August 2002 (Figure 12). Pacific saury (Cololabis saira) juveniles dominated the fish 

composition in 2000 (Table 3). No one species dominated in 2002. Only cabezon 

(Scorpaenichthys marmoratus) and unidentified osmerids were present in all four cruises. Mean 

concentrations did not exceed 4.66/100 m3

 (Table 3). Except for the sauries, the frequency of 

occurrence was no more than nine stations during any one cruise (Table 3). Pacific saury 

occurred at 28 stations in June 2000 and 17 stations in August 2000 (Table 3). Spatially, the 

distribution of larval and juvenile fish was beyond the shelf break in 2000 and over the shelf in 

2002 (Figure 29 and Figure 30). 

Others 

Polychaetes were not caught in June 2000 and rarely were found during the other three 

cruises (Table 3). The pelagic polychaete Tomopteris sp. was most common in June 2002 when 

it was identified in 21 samples. Autolytus sp. and unidentified syllids were in epitoke stages. 

46
126°W 125°W 1

Longitude

125°W 124°W

Longitude

42°N43°N44°N45°N

Latitude

CA

Cape Bla

OREGON

CALIFORNIA

Cape Blanco

 0.001–<1 1–<10 10–<100 100–<178

PACIFIC OCEAN PACIFIC OCEAN

Figure 27. Abundance and distribution of Sagitta spp. concentrations (no./100 m3) in June (left) and August (right) 2000. 

zero concentration. The dotted line is the 200-m depth contour. 

47
126°W 125°W 1

Longitude

125°W 124°W

Longitude

42°N43°N44°N45°N

Latitude

 0.001–<1 1–<10 10–<100 100–<178

CA

Cape Bla

OREGON

CALIFORNIA

Cape Blanco

PACIFIC OCEAN PACIFIC OCEAN

Figure 28. Abundance and distribution of Sagitta spp. concentrations (no./100 m3) in June (left) and August (right) 2002. 

zero concentration. The dotted line is the 200-m depth contour. 

48
126°W 125°W 1

Longitude

125°W 124°W

Longitude

42°N43°N44°N45°N

Latitude

C

Cape Bla

OREGON

CALIFORNIA

Cape Blanco

 0.001–<1 1–<10 10–<24

PACIFIC OCEAN PACIFIC OCEAN

Figure 29. Abundance and distribution of larval and juvenile fish concentrations (no./100 m3) in June (left) and August (rig

represent zero concentration. The dotted line is the 200-m depth contour. 

49
126°W 125°W 

Longitude

125°W 124°W

Longitude

42°N43°N44°N45°N

Latitude

 0.001–<1 1–<10 10–<24

CA

Cape Bla

OREGON

CALIFORNIA

Cape Blanco

PACIFIC OCEAN PACIFIC OCEAN

Figure 30. Abundance and distribution of larval and juvenile fish concentrations (no./100 m3) in June (left) and August (rig

represent zero concentration. The dotted line is the 200-m depth contour. 

50
Heteropods and pteropods were present in the 2000 and 2002 samples, whereas the 

nudibranchs were found only in the 2000 samples (Table 2). An early life stage of Chiroteuthis

sp. was caught in August 2000 and August 2002, whereas market squid (Loligo opalescens) was 

collected only in August 2002. In August 2000 one individual Chiroteuthis sp. was seen in a 

sample from lat. 43.0°N immediately beyond the shelf break. In August 2002 the second station 

west of the shelf break at lat. 42.2°N had three Chiroteuthis sp. individuals. 

Cumaceans were found only in the June 2002 samples (Table 3). Diastylopsis sp., 

Hemilamprops spp., and Oxyurostylis sp. were collected on 8 June 2002 on the 2A transect at 

lat. 44.4°N. 

Four mysid species were in the samples (Table 3), and Alienacanthomysis macropsis was 

the only species identified in samples from all four cruises. Its highest mean abundance was 

11.47/100 m3

 in an August 2000 sample. The other species occurred in one or two cruises. 

Six isopod species were identified (Table 3). Idotea fewkesi was the most common 

isopod but was not collected in August 2002. Vosnesensky’s isopod (Pentidotea wosnesenskii) 

was collected in June 2000, August 2000, and June 2002. Eelgrass isopod (P. resecata) and I. 

rufescens were not in any of the 2002 samples. Excirolana linguifrons occurred once in August 

2000. A single specimen of Acanthamunnopsis milleri was caught on 4 August 2002 at the 

second station from shore on the Rogue River transect south of Cape Blanco. 

Ten orders of insects were identified. Diptera and Neuroptera were the most frequent 

orders in June 2000, June 2002, and August 2002 (Table 3). In August 2000 Coleoptera had the 

highest mean abundance of 0.80/100 m3. In June 2002 Hymenoptera occurred only once, but 

had the highest abundance at 2.04/100 m3. Homoptera, Odonata, Plecoptera, and Trichoptera 

were in the 2000 samples but not the 2002 samples. 

Spatial Variability 

Inshore-offshore distribution of the five most abundant taxa varied among and within 

cruises along six main transects (Figure 1): 

1) Newport Hydroline, 

2) Heceta Head, 

3) Umpqua River, 

4) Five Mile River, 

5) Rogue River, and 

6) Crescent City. 

Spatial variability also was apparent from north to south. 

In June 2000 Pacific saury juveniles were more abundant beyond the shelf break along all 

six transects (Figure 31). Except along the Heceta Head and Rogue River transects, Dungeness 

crab megalopae generally were more abundant inshore (Figure 31). Oregon cancer and red rock 

crab megalopae were most abundant at the nearshore station on the Umpqua River Transect 

51
Umpqua River Transect

Concentration (no./100 m3

)

0

20

40

140

160

Heceta Head Transect

0

5

10

70

80

Crescent City Transect

Distance Offshore (km)

90100 80 70 5060 40 30 20 10 0

0

1

2

3

4

Newport Hydroline

0

1

2

3

4

C. magister

C.

pr

 oregonensis/

oductus

C. saira

E. pacifica

L. pulex

Five Mile River Transect

0

2

4

6

8

10

Rogue River Transect

0

10

20

30

220

230

Dungeness crab 

Oregon cancer 

and red rock crab 

Pacific saury 

Pacific krill 

L. pulex

Distance offshore (km)

Figure 31. Inshore-offshore distribution of five most abundant neustonic mesozooplankton taxa along six 

main transects from north (Newport Hydroline) to south (Crescent City Transect) in June 2000. 

Vertical dashed lines represent shelf break at 200-m depth. Diagonal slashes in y-axes are breaks 

in data range. 

52
(Figure 31). The hyperiid L. pulex was most abundant beyond the shelf along the Rogue River 

Transect and inshore on the Five Mile River Transect (Figure 31). Pacific krill concentrations 

were low over and beyond the shelf (Figure 31). 

In August 2000 the Umpqua River Transect had the highest concentration of neustonic 

mesozooplankton because of high T. spinifera concentrations at the station closest to shore 

(Figure 32). As in June 2000 Pacific saury also was more abundant beyond the shelf (Figure 32). 

Hyperoche medusarum was common nearshore, but it also was caught beyond the shelf from the 

Umpqua River to Crescent City transects (Figure 32). Pacific krill was caught more often 

beyond the shelf (Figure 33). Atylus tridens was distributed inshore and offshore (Figure 32). 

In June 2002 all five taxa, particularly Dungeness crab megalopae and Oregon cancer and 

red rock crab megalopae, were most abundant nearshore from the Newport Hydroline to the Five 

Mile River Transect (Figure 33). They were more distributed over the shelf on the Rogue River 

Transect and beyond the shelf break on the Crescent City Transect (Figure 33). It is worth 

noting that the Newport Hydroline to Rogue River transects were sampled one day apart from 

1 June to 5 June 2002 during the mesoscale leg of the cruise. Only two nearshore stations on the 

Crescent City Transect could be sampled before sea conditions became too rough to continue. 

Data for the Crescent City Transect are from the fine-scale leg when five stations were sampled 

successfully in one day, eight days after the end of the mesoscale study. Data examination from 

these two stations during the mesoscale leg showed that spatial distribution along the transect 

was similar to that seen in the other five transects. 

In August 2002 Sagitta spp. were abundant nearshore on the Heceta Head and Umpqua 

River transects and offshore on the Rogue River and Crescent City transects (Figure 34). 

Dungeness crab megalopae abundance peaked inshore and near the shelf break (Figure 34). 

Hyperoche medusarum and T. spinifera were more abundant on the Five Mile River and Rogue 

River transects (Figure 34). Unidentified chaetognaths peaked inshore on the Heceta Head and 

Umpqua River transects and offshore on the Crescent City Transect (Figure 34). 

Species Diversity 

Species diversity (H') was higher in 2002 than in 2000, but it was not significantly 

different between years (ANOVA, p = 0.4497) or seasons (t-test, p = 0.8, 2000; t-test, p = 0.5, 

2002). Maximum diversity was 2.15 (mean = 0.78) in June 2000, 2.11 (mean = 0.80) in August 

2000, 2.32 (mean = 0.95) in June 2002, and 2.01 (mean = 0.85) in August 2002. The diversity 

was not concentrated in any particular area of the survey, but it was evenly distributed. The 

maximum number of taxa in any one sample was 12 (mean = 3.8) in June 2000, 25 (mean = 3.6) 

in August 2000, 25 (mean = 6.2) in June 2002, and 18 (mean = 4.3) in August 2002. 

Species Associations 

Analysis of species cluster groupings based on station assemblages included 17 taxa in 

June 2000, 20 in August 2000, 33 in June 2002, and 17 in August 2002. Within each cruise, the 

number of clusters was determined by cutting the resulting dendrograms at 50% of the remaining 

information. Then station locations and habitat preferences (i.e., pelagic, benthic, and terrestrial) 

of specimens were considered. 

53
Five Mile River Transect

0.0

0.5

1.0

1.5

2.0

Rogue River Transect

0

2

4

6

8

Umpqua River Transect

0.0

0.5

1.0

1.5

Concentration (no./100 

m )

3

0

2

4

50

60

Crescent City Transect

Distance Offshore (km)

100 102030405060708090 0

0

4

8

12

Newport Hydroline A. tridens

C. saira

E. pacifica

H. medusarum

T. spinifera

Heceta Head Transect

Distance offshore (km) 

Atylus tridens 

Pacific saury 

Pacific krill 

H. medusarum 

T. spinifera 

0.0

0.5

1.0

1.5

Figure 32. Inshore-offshore distribution of five most abundant neustonic mesozooplankton taxa along six 

main transects from north (Newport Hydroline) to south (Crescent City Transect) in August 2000. 

On the Crescent City Transect, two stations beyond 100 km were omitted. Vertical dashed lines 

represent shelf break at 200-m depth. Diagonal slashes in y-axes are breaks in data range. 

Figure 32. Inshore-offshore distribution of five most abundant neustonic mesozooplankton taxa along six 

main transects from north (Newport Hydroline) to south (Crescent City Transect) in August 2000. 

On the Crescent City Transect, two stations beyond 100 km were omitted. Vertical dashed lines 

represent shelf break at 200-m depth. Diagonal slashes in y-axes are breaks in data range. 

54
Crescent City Transect

Distance Offshore (km)

8090100 506070 3040 1020 0

0

2

4

6

8

10

Newport Hydroline

0

400

800

2400

2600

C. magister

C.

pro

 oregonensis/

ductus

H. medusarum

Sagitta spp.

T. spinifera

Heceta Head Transect

0

10

20

30

Umpqua River Transect

Concentration (no./100 m3

)

0

100

200

600

700

Five Mile River Transect

0

200

400

1200

1300

Rogue River Transect

Dungeness crab 

Oregon cancer 

and red rock crab 

H. medusarum 

Sagitta spp. 

T. spinifera 

Distance offshore (km)

0

10

20

200

250

Figure 33. Inshore-offshore distribution of five most abundant neustonic mesozooplankton taxa along six 

main transects from north (Newport Hydroline) to south (Crescent City Transect) in June 2002. 

Vertical dashed lines represent shelf break at 200-m depth. Diagonal slashes in y-axes are breaks 

in data range. 

55
Newport Hydroline

0

1

2

3

4

C. magister

Chaetognatha

H. medusarum

Sagitta spp.

T. spinifera

Crescent City Transect

Distance Offshore (km)

102030405060708090100 0

0

20

40

60

Heceta Head Transect

0

10

20

30

125

150

Umpqua River Transect

Concentration (no./100 m3

)

0

50

100

150

200

Five Mile River Transect

0

5

10

15

Rogue River Transect

Dungeness crab 

Chaetognatha 

H. medusarum 

Sagitta spp. 

T. spinifera 

0

5

10

15

Figure 34. Inshore-offshore distribution of five most abundant neustonic mesozooplankton taxa along six 

main transects from north (Newport Hydroline) to south (Crescent City Transect) in August 2002. 

Vertical dashed lines represent shelf break at 200-m depth. Diagonal slashes in y-axes are breaks 

in data range. 

Distance offshore (km)

56
Dungeness crab megalopae and Oregon cancer and red rock crab megalopae were 

associated with each other in June of 2000 and 2002 (Figure 35 and Figure 36). In August 

Dungeness crab megalopae were clustered with chaetognaths, fish, hyperiids, hippolytids, and 

Eucalanus sp. (Figure 35 and Figure 36). Oregon cancer and red rock crab megalopae were 

clustered with T. spinifera in August 2000 and with Pacific rock and graceful crab megalopae, 

hippolytids, Tomopteris sp., hyperiids, and krill in August 2002 (Figure 35 and Figure 36). 

Terrestrial insects (Diptera, Neuroptera, Lepidoptera, and Coleoptera) generally were 

clustered with benthic gammarids (A. angusta, H. frequens, A. tridens, and Peramphithoe sp.) 

and isopods (I. fewkesi) in 2000 (Figure 35). However, in 2002 they associated with the copepod 

N. cristatus (Figure 36). A cluster of hyperiid Hyperia medusarum, T. malmi, T. pacifica, and V.

australis was found for June 2000 and August 2002 (Figure 35 and Figure 36). 

Common pelagic taxa such as T. spinifera, Pacific krill and Hyperoche medusarum were 

in the same cluster groupings in June of 2000 and 2002 and in August 2002 (Figure 35 and 

Figure 36). In August 2000 T. spinifera was not found to cluster with Pacific krill and 

Hyperoche medusarum (Figure 35). In the 2000 survey Pacific saury juveniles were associated 

with pelagic euphausiids and hyperiids (Figure 35). 

Unidentified chaetognaths and Eukrohnia sp. were clustered together for both cruises in 

2002 (Figure 36). Grooved mussel crab zoeae and megalopae and Tomopteris sp. were grouped 

with the unidentified chaetognaths and Eukrohnia sp. in June (Figure 36). Dungeness crab 

megalopae, Eucalanus sp., and Sagitta spp. were associated with the unidentified chaetognaths 

and Eukrohnia sp. in August (Figure 36). Sagitta spp. associated more closely with T. spinifera, 

Pacific krill, and Hyperoche medusarum in June 2002 (Figure 36). 

Ghost shrimp (Neotrypaea californiensis) zoeae and megalopae and unidentified zoeal 

crangonids were clustered with Pacific rock and graceful crab megalopae in June 2002 (Figure 

36). In another subcluster Crangonidae sp. A zoeae and hippolytids grouped with Eucalanus sp. 

(Figure 36). 

Diel Studies 

During both diel studies in 2002, seven sets of samples were collected. Forty taxa were 

identified, 32 in June and 22 in August (Table 5 and Table 6). 

During the June diel study, water temperature, salinity, zooplankton biovolume, and 

chlorophyll a concentrations fluctuated over time (Figure 37). Although the biovolume peaked 

at 1800 hours, total mesozooplankton concentration was low and did not peak until 0204 hours 

(Figure 37). Dungeness crab megalopae and Sagitta spp. were in all seven samples. Oregon 

cancer and red rock crab megalopae, Eucalanus sp., and Pandalus spp. megalopae occurred in 

four or more samples (Table 5). Most taxa were collected at night (2205 hours and 0204 hours), 

when total sample concentrations also were high. The total sample concentrations were 

97.38/100 m3 at 2205 hours and 255.68/100 m3

 at 0204 hours. The midday (1141 hours) 

sampling collected 5.95/100 m3, the lowest concentration (Figure 37). The five most abundant 

taxa were Diastylopsis sp., Dungeness crab and Oregon cancer and red rock crab megalopae, 

57
Distance (Objective Function)

Information Remaining (%)

1.6E-01

100

3.3E+00

75

6.5E+00

50

9.6E+00

25

1.3E+01

0

Allorche

Diptera

Neuropte

C.magist

C.org/pr

Coleopte

I.fewkes

Hyale.fr

Hyperoch

T.spinif

Cololabi

E.pacifi

Lycaea

Hyperia

Tryphana

Themisto

Vibilia

Allorchestes angusta 

Diptera 

Neuroptera (unidentified) 

Dungeness crab 

Oregon cancer and red rock crab 

Coleoptera (unidentified) 

Idotea fewkesi 

Hyale frequens 

Hyperoche medusarum 

Thysanoessa spinifera 

Pacific saury 

Pacific krill 

Lycaea pulex 

Hyperia medusarum 

Tryphana malmi 

Themisto pacifica 

Vibilia australis 

Distance (Objective Function)

Information Remaining (%)

7.7E-02

100

5.3E+00

75

1E+01

50

1.6E+01

25

2.1E+01

0

Allorche

Coleopte

I.fewkes

Atylus

Hyale.fr

Peramphi

C.org/pr

T.spinif

C.magist

S.scripp

Tarleton

Hyperia

S.zacent

Clupea.p

E.pacifi

Cololabi

Hyperoch

Hippolyt

S.elegan

Themisto

Allorchestes angusta

Coleoptera (unidentified) 

Idotea fewkesi 

Atylus tridens 

Hyale frequens 

Peramphithoe humeralis 

Oregon cancer and red rock crab 

Thysanoessa spinifera 

Dungeness crab

Sagitta scrippsae 

Blue lanternfish 

Hyperia medusarum 

Sharpchin rockfish 

Pacific herring 

Pacific krill 

Pacific saury 

Hyperoche medusarum 

Hippolytidae (unidentified) 

Sagitta elegans 

Themisto pacifica 

Distance (objective function) 

1.6E-01 3.3E+00 6.5E+00 9.6E+00 1.3E+01 

Distance (objective function) 

 7.7E-02 5.3E+00 1E+01 1.6E+01 2.1E+01 

Information remaining (%) 

100 75 50 25 0 

Information remaining (%) 

100 75 50 25 0 

Figure 35. Dendrograms of neustonic mesozooplankton taxa cluster groupings for June (top) and August 

(bottom) 2000. Vertical dashed lines represent cutoff level. 

58
Distance (O ctive Function) bje

Information Remaining (%)

9.6E-02

100

1.2E+01

75

2.3E+01

50

3.5E+01

25

4.7E+01

0

Figure 36. Dendrograms of neustonic mesozooplankton taxa cluster groupings for June (top) and August 

(bottom) 2002. Vertical dashed lines represent cutoff level. 

Allorche

Tryphana

Ammodyte

Hemilepi

E.pacifi

T.spinif

Hyperoch

Sagitta

C.magist

C.org/pr

Osmerida

Pandalus

Calliopi

Scorpaen

Diptera

Neuropte

Lepidopt

N.crista

Atylus

Discorso

Themisto

C.ant/gr

Neotrypa

Crangoni

C.cf.fra

Eucalanu

Hippolyt

Hyperia

N.plumch

Chaetogn

Eukrohni

Fabia.su

Tomopter

Allorchestes angusta 

Tryphana malmi 

Pacific sand lance 

Brown Irish lord 

Pacific krill 

Thysanoessa spinifera 

Hyperoche medusarum 

Sagitta spp.

Dungeness crab 

Oregon cancer and red rock crab 

Osmeridae (unidentified) 

Pandalus spp. 

Calliopius cf C. columbianus 

Scorpaenichthys marmoratus 

Diptera (unidentified) 

Neuroptera (unidentified) 

Lepidoptera (unidentified) 

Neocalanus cristatus 

Atylus tridens 

Tubeworm hermit crab 

Themisto pacifica 

Pacific rock crab and graceful crab 

Ghost shrimp 

Crangonidae (unidentified) 

Crangonidae sp. A 

Eucalanus sp. 

Hippolytidae (unidentified) 

Hyperia medusarum 

Neocalanus plumchrus 

Chaetognatha (unidentified) 

Eukrohnia sp. 

Grooved mussel crab 

Tomopteris sp. 

Distance (Objective Function)

Information Remaining (%)

1.5E-01

100

3.6E+00

75

7E+00

50

1E+01

25

1.4E+01

0

C.ant/gr

Hippolyt

C.org/pr

Tomopter

Hyperia

Tryphana

E.pacifi

Hyperoch

T.spinif

Diptera

N.crista

Themisto

C.magist

Chaetogn

Sagitta

Eucalanu

Eukrohni

Pacific rock crab and graceful crab 

Hippolytidae (unidentified) 

Oregon cancer and red rock crab 

Tomopteris sp. 

Hyperia medusarum 

Tryphana malmi 

Pacific krill 

Hyperoche medusarum 

Thysanoessa spinifera 

Diptera (unidentified) 

Neocalanus cristatus 

Themisto pacifica 

Dungeness crab 

Chaetognatha (unidentified) 

Sagitta spp. 

Eucalanus sp. 

Eukrohnia sp. 

Distance (objective function) 

 9.6E-02 1.2E+01 2.3E+01 3.5E+01 4.7E+01

Information remaining (%) 

100 75 50 25 0 

Information remaining (%) 

100 75 50 25 0

Distance (objective function) 

 1.5E-01 3.6E+00 7E+00 1E+01 1.4E+01 

59
Table 5. Concentrations (no./100 m3

) of taxa in the June 2002 diel study at station NH-5 (lat. 44.7°N, 

long. 124.2°W). 

Time of day 

Common name Scientific namea

1012 1411 1800 2205 0204 0606 0932 

Segmented worm Annelida 

Bristle worm Polychaeta 

Spionidae (unidentified) — — — — 0.57 — — 

Arthropod Arthropoda

Crustacean Crustacea 

Copepod Copepoda 

Eucalanus sp. 1.04 — 0.63 0.98 1.14 — — 

Lophothrix frontalis — — — — 0.57 — — 

Cumacean Cumacea

Colurostylis sp. — — — 0.49 2.86 — — 

Diastylopsis sp — — — — 50.34 — — 

Lamprops sp., 

Hemilamprops sp., or 

Mesolamprops sp. — — — — 10.30 — — 

Leptostylis sp. — — — 0.49 1.14 — — 

Oxyurostylis sp. — — — — 0.57 — — 

Opossum shrimp Mysida

Alienacanthomysis 

macropsis — — — 1.97 8.01 — — 

Neomysis kadiakensis — — — — 1.14 — — 

Mysida (unidentified) — — — — 0.57 — — 

Amphipod Amphipoda

Gammarid Gammaridea 

Atylus tridens — — — 3.44 6.86 — 0.56 

Hyperiid Hyperiidea

Hyperoche 

medusarum — — — 1.48 — — — 

Themisto pacifica — — — 1.48 0.57 — — 

Krill Euphausiacea

Thysanoessa 

spinifera — — — — — 0.50 — 

Crab, lobster, 

prawn, shrimp Decapoda

Hermit crab, sand 

crab, mole crab, 

porcelain crab, 

squat lobster, 

stone crab Anomura 

Tubeworm hermit 

crab 

Discorsopagurus 

schmitti — — — 0.49 1.72 — — 

Alaskan hermit 

crab Pagurus ochotensis — — — — 1.72 — — 

Pagurus sp. C [sensu

Lough (1975)] — — — — 0.57 — — 

60
Table 5 continued. Concentrations (no./100 m3

) of taxa in the June 2002 diel study at station NH-5 

(lat. 44.7°N, long. 124.2°W). 

Time of day 

Common name Scientific namea

1012 1411 1800 2205 0204 0606 0932 

True crab Brachyura 

Pacific rock crab 

and graceful grab 

Cancer antennarius 

and C. gracilis — — — 0.98 — — — 

Dungeness crab Cancer magister 3.65 4.63 3.77 16.72 0.57 25.91 7.79 

Oregon cancer 

crab and red rock 

crab 

Cancer oregonensis

and C. productus 4.69 — 0.63 1.48 0.57 1.50 24.48 

Grooved mussel 

crab Fabia subquadrata — — 2.51 1.48 1.72 — — 

Shrimp Caridea 

Stout crangon Crangon alba — — — — 1.14 — — 

Sand shrimp, bay 

shrimp Crangonidae — — — 29.02 8.58 — — 

Crangonidae sp. Ab — — — — 1.14 0.50 1.11 

Broken-back 

shrimp 

Hippolytidae 

(unidentified) — — 1.26 6.39 8.58 — — 

Pandalus spp. 0.52 0.66 0.63 2.46 0.57 — — 

Ghost shrimp, 

mud shrimp, 

sponge shrimp Thalassinidea 

Ghost shrimp 

Neotrypaea 

californiensis — — — — 1.14 — — 

Blue mud shrimp 

Upogebia 

pugettensis — — — — 1.72 — — 

Arrowworm Chaetognatha

Sagitta spp. 12.52 0.66 28.25 27.54 114.97 16.94 22.81 

Chaetognatha 

(unidentified) — — — — 9.15 0.50 — 

Osteichthyes 

Smelt Osmeridae (unidentified) — — — — 0.49 17.16 — 

a

 Indentation patterns do not follow strict taxonomic classification. Taxonomic levels are indented to indicate a 

subcategory that is identified with a commonly recognizable scientific name. Within the lowest subcategories, 

species and other taxa with data are indented the same. This resulted in species not being indented the same 

between high taxonomic levels such as phyla.

b A distinct single species in the family Crangonidae that could not be identified to genus or species with the 

available taxonomic keys. Crangonidae (unidentified) has one or more unidentified species and does not include 

Crangonidae sp. A. 

unidentified crangonid zoeae and megalopae, and Sagitta spp. Crangonids dominated at 2205 

hours whereas Sagitta spp. dominated at 0204 hours (Figure 37). Generally the number of taxa 

and species diversity (H') followed a similar temporal pattern (Figure 38). 

61
Table 6. Concentrations (no./100 m3

) of taxa in the August 2002 diel study at station HH-2 

(lat. 44.0°N, long. 124.4°W). 

Time of day

Common name Scientific namea

0825 1237 1637 2142 0138 0532 0936 

Mollusc Mollusca 

Gastropod Gastropoda 

Sea butterfly Clionidae (unidentified) — — — 0.52 — — —

Arthropod Arthropoda 

Crustacean Crustacea 

Copepod Copepoda 

Eucalanus sp. — — — 2.07 0.74 0.62 —

Neocalanus cristatus — — — 0.52 2.23 — —

Amphipod Amphipoda 

Gammarid Gammaridea

Allorchestes 

angusta 1.84 — — — — — —

Atylus tridens — — — 0.52 2.23 — —

Hyperiid Hyperiidea

Hyperoche 

medusarum 0.61 — — 6.21 16.36 170.64 —

Themisto pacifica — — — 16.55 3.72 6.23 —

Krill Euphausiacea 

Pacific krill Euphausia pacifica — — — 11.38 49.08 — —

Thysanoessa 

spinifera 1.84 0.80 — 58.97 1,997.39 16.19 1.25

Crab, lobster, 

prawn, shrimp Decapoda 

Hermit crab, sand 

crab, mole crab, 

porcelain crab, 

squat lobster, 

stone crab Anomura 

Alaskan hermit 

crab Pagurus ochotensis — — — 1.03 0.74 — —

True crab Brachyura

Pacific rock crab 

and graceful crab 

Cancer antennarius 

and C. gracilis — — — 18.10 5.21 — —

Dungeness crab Cancer magister — — — 15.52 7.74 8.72 1.25

Oregon cancer 

crab and red rock 

crab 

Cancer oregonensis 

and C. productus — — — 57.42 63.21 — —

Shrimp Caridea

Sand shrimp, bay 

shrimp 

Crangonidae 

(unidentified) — — — — 3.72 — —

Crangonidae sp. Ab — — — 0.52 1.49 — —

Broken-back 

shrimp 

Hippolytidae 

(unidentified) 1.23 — — 3.62 0.74 — —

62
Table 6 continued. Concentrations (no./100 m3

) of taxa in the August 2002 diel study at station HH-2 

(lat. 44.0°N, long. 124.4°W). 

Time of day

Common name Scientific namea 0825 1237 1637 2142 0138 0532 0936 

Insect Insecta 

True bug Hymenoptera 0.61 — — — — — —

Arrowworm Chaetognatha 

Sagitta spp. 11.67 — 0.61 15.00 30.49 5.60 —

Chaetognatha 

(unidentified) 0.61 — — 2.07 4.46 0.62 —

Chordate Chordata 

Osteichthyes 

Sculpin Cottidae 

Cabezon 

Scorpaenichthys 

marmoratus — — — — — 0.62 —

Anchovy Engraulidae

Northern anchovy Engraulis mordax — — — 1.03 — — —

Snailfish Liparidae 

Liparis sp. — — — — 0.74 — —

a

 Indentation patterns do not follow strict taxonomic classification. Taxonomic levels are indented to indicate a 

subcategory that is identified with a commonly recognizable scientific name. Within the lowest subcategories, 

species and other taxa with data are indented the same. This resulted in species not being indented the same 

between high taxonomic levels such as phyla.

b A distinct single species in the family Crangonidae that could not be identified to genus or species with the 

available taxonomic keys. Crangonidae (unidentified) has one or more unidentified species and does not include 

Crangonidae sp. A. 

In the August diel study, water temperature was warmer during the afternoon than during 

the night, and salinity fluctuated over time (Figure 39). Chlorophyll a concentrations peaked 

during the evening, and then declined during the night (Figure 39). However, there was a sharp 

drop in chlorophyll a at 1237 hours (Figure 39), which was confirmed with data recorded by the 

auxiliary fluorometer on the CTD vertical profiler. Sample biovolume was low during the 

daytime and peaked at 0138 hours before declining prior to dawn (Figure 39). The temporal 

pattern of biovolume resembled that of the total mesozooplankton concentration (Figure 39). 

Most mesozooplankton taxa occurred in one or two samples, and samples collected at night 

(2142 hours and 0138 hours) contained the most taxa (Table 5). The midday (1237 hours and 

1637 hours) samples contained only one taxon each (Table 5). Thysanoessa spinifera was the 

most frequent and abundant species during the August diel study. The maximum T. spinifera

concentration was 1,997.39/100 m3 and occurred at 0138 hours, when the most mesozooplankton 

were caught. Hyperoche medusarum, Pacific krill, Oregon cancer and red rock crab megalopae, 

and Sagitta spp. were the more abundant species and mainly caught at night (Figure 39). 

Hyperoche medusarum peaked at 0532 hours (Figure 39). Comparison of species diversity 

indices and number of taxa per sampling time indicated that, while the number of taxa at 0138 

hours was high, diversity was low (Figure 38). This is in contrast to that observed at 2124 hours, 

when diversity was much higher than at 0138 hours (Figure 38). 

63
Sampling Time

1012 1411 1800 2205 0204 0606 0932

Concentration (no./100 m3

)

0

50

100

150

200

250

Total Sample Concentration (no./100 m3

)

0

50

100

150

200

250

Diastylopsis sp. 

Dungeness crab

Oreg

r

on cancer crab and

ed rock crab

Crangonidae (unidentified) 

Sagitta spp. 

Biovolume (ml/100 m3

)

20

40

60

80

100

120

140

Chlorophyll 

a (μg/l)

2.0

2.5

3.0

3.5

4.0

4.5

Temperature (°C)

8.5

9.0

9.5

10.0

10.5

11.0

Salinity (psu)

31.5

32.0

32.5

33.0

33.5

Sampling time 

Total sample concentration 

Diastylopsis sp.

Dungeness crab 

Oregon cancer crab and 

red rock crab 

Crangonidae (unidentified)

Sagitta spp. 

Figure 37. Temporal variations in water temperature (°C), salinity (psu), neustonic mesozooplankton 

biovolumes (ml /100 m3

), chlorophyll a (μg/l), and concentrations (no./100 m3) of five most 

abundant taxa and total mesozooplankton at station NH-5 in June 2002. Gray areas indicate 

nighttime sampling. 

64
1012 1411 1800 2205 0204 0606 0932

H'

0.0

0.5

1.0

1.5

2.0

2.5

No. of taxa

0

5

10

15

20

25

30

Sampling Time

0825 1237 1637 2142 0138 0532 0936

H'

0.0

0.5

1.0

1.5

2.0

2.5

No. of taxa

0

5

10

15

20

25

30

Figure 38. Diel pattern of neustonic mesozooplankton species diversity indices (H') and number of taxa 

in June 2002 (top) at station NH-5 and August 2002 (bottom) at station HH-2. Gray areas 

indicate nighttime sampling. 

Sampling time 

65
Sampling Time

0825 1237 1637 2142 0138 0532 0936

Concentration (no./100 m3

)

0

25

50

75

100

125

150

175

200

2000

2500

Total Sample Concentration (no./100 m3

)

0

25

50

75

100

125

150

175

200

2000

2500

Hyperoche medusarum 

Euphausia pacifica 

Thysanoessa spinifera 

Cancer orego

productus 

nensis/

Sagitta spp. 

Biovolume (ml/100 m3

)

0

50

100

150

200

250

Chlorophyll 

a (μg/l)

14

16

18

20

22

24

26

28

Temperature (°C)

10.6

10.8

11.0

11.2

11.4

Salinity (psu)

32.50

32.75

33.00

33.25

33.50

Figure 39. Temporal variations in water temperature (°C), salinity (psu), neustonic mesozooplankton 

biovolumes (ml/100 m3

), chlorophyll a (μg/l), and concentrations (no./100 m3) of five most 

abundant taxa and total mesozooplankton at station HH-2 in August 2002. Gray areas indicate 

nighttime sampling. Diagonal slashes in y-axes are breaks in data range. 

Sampling time 

Hyperoche medusarum

Pacific krill 

Thysanoessa spinifera 

Oregon cancer crab 

and red rock crab 

Sagitta spp. 

Total sample concentration 

66
Discussion 

The variations observed in the neustonic mesozooplankton abundance and distribution 

may be affected by a number of factors such as predator-prey interactions, interspecific 

competition for space and food resources, vertical migration, current direction and speed, and 

water surface conditions (i.e., varied from calm with no waves breaking to large, choppy swells 

with waves breaking). Geomorphological features such as Heceta Bank and a coastal 

promontory, Cape Blanco, also could play a role. During the 2000 survey, a strong southward 

upwelling jet flowed along the outside of Heceta Bank, and a weaker northward current flowed 

inshore of the bank (Barth et al. 2005). Barth et al. (2000 and 2005) observed that Cape Blanco 

redirects the southward flow of the California Current offshore as it passes the cape. In addition, 

Peterson and Keister (2002) found that Cape Blanco separated the copepod community from the 

upper 100-m water column into interspecific zones north and south of the cape. Some taxa are 

meroplankton that spend a portion of their life cycles in the upper water column where currents 

could affect their seasonal occurrence and the enumeration of the different life stages (Lough 

1975, Peres 1982, Holdway and Maddock 1983). 

Data from the CTD casts indicated cooler water during 2002 than in 2000. Cool water 

nearshore was caused by coastal upwelling and the subsequent offshore advection of upwelled 

water during the summer season along the Oregon coast (Huyer 1983). Daily average upwelling 

indices showed that downwelling occurred during much of the June 2000 cruise because of an 

intense storm that originated from the south and was accompanied by strong southerly winds. 

During the cruise, northward wind stress reached nearly 0.4 Newton per square meter before 

subsiding (Barth et al. 2005). These conditions were anomalous for this time of year (Batchelder 

et al. 2002). The upwelling indices for August in 2000 and 2002 were similar, although strong 

upwelling occurred during July 2002 before the August 2002 cruise. Murphree et al. (2003) 

reported that anomalous wind stress in the Gulf of Alaska during early 2002 caused a strong 

equator-ward flow of the California Current, hence an intrusion of subarctic water to the 

California Current. The anomalous intrusion of subarctic water in our survey area also was 

identified by Barth (2003), Kosro (2003), and Strub and James (2003). This in turn may have 

influenced our observations of higher chlorophyll a concentrations in 2002 than in 2000, 

particularly over Heceta Bank. Wheeler et al. (2003) also reported high chlorophyll a

concentrations off southern Oregon in July 2002 and attributed this to increased nutrients 

transported to this region as part of the subarctic anomaly. 

For all four cruises, the numerically dominant taxa were Dungeness crab megalopae, 

Oregon cancer and red rock crab megalopae, Hyperoche medusarum, T. pacifica, Pacific krill, T.

spinifera, and Sagitta spp. These taxa have been commonly caught in past surveys of this area 

(Lough 1975, Brodeur et al. 1987, Brodeur 1990, Schabetsberger et al. 2003, Gómez-Gutiérrez et 

al. 2005). 

67
The distribution of Dungeness crab megalopae and Oregon cancer and red rock crab 

megalopae across the shelf and offshore mainly was because of the water circulation patterns in 

the survey area. The concentrations of these abundant species dropped dramatically from June to 

August in both years, perhaps contributing in large part to the seasonal decrease in biovolumes 

because of their large body size. Early in the year when downwelling occurs, both cancrid 

species pass through their zoeal stages while being transported offshore (Lough 1975, Shenker 

1988, Jamieson et al. 1989, Hobbs et al. 1992). During the spring, the winds shift from 

southwesterly to northerly and upwelling begins, causing the southward flowing California 

Current to become stronger (Hickey and Banas 2003). This is when the last zoeal stage 

metamorphoses into the megalopal stage. The megalopae then are transported cross-shelf to 

return nearshore where they settle in shallow water (Lough 1975, Shenker 1988, Hobbs et al. 

1992). Occasional southwesterly storms with accompanying winds during the upwelling season 

may facilitate the shoreward transport of the megalopae (Shenker 1988, Jamieson et al. 1989). 

However, Roegner et al. (2003) found that Dungeness crab megalopal recruitment to two 

Washington estuaries occurred during a wide range of wind stress and water movements. 

Tidally generated internal waves in convergence zones may be another mode of transport 

(Johnson and Shanks 2002). Surface orientation of megalopae or their practice of clinging to 

floating surface debris also has been proposed (Jamieson et al. 1989). Dungeness crab 

megalopae and Oregon cancer and red rock crab megalopae were previously caught up to 111 

km offshore along the Newport Hydroline (Lough 1975, Shenker 1988). In addition, Dungeness 

crab megalopae and Oregon cancer and red rock crab megalopae were collected 28–170 km off 

the southwestern side of Vancouver Island in British Columbia, Canada (Jamieson et al. 1989). 

Therefore, the occurrence of these megalopae offshore and beyond the shelf break in our neuston 

survey was not unexpected.

The differences in Dungeness crab megalopal abundance between June 2000 and June 

2002 may have been because of several effects. The timing of zoeal to megalopal 

metamorphosis could have differed between years (Lough 1975). This could influence whether 

most individuals were in the megalopal stage by the time of this sampling. Aggregation 

behaviors have been suggested as another effect (Lough 1975, Shenker 1988, Roegner et al. 

2003). Dungeness crab was observed more often at the surface during the megalopal phase than 

during all zoeal stages, probably because of their photopositive response to light (Lough 1975, 

Shenker 1988). However, in other studies, more megalopae were caught from the ocean surface 

at night than at other times; this possibly was caused by vertical migration, avoidance of 

predators or the net, or surface orientation for onshore transport (Shenker 1988, Jamieson et al. 

1989, Johnson and Shanks 2002, Roegner et al. 2003). Temperature and salinity were 

considered important environmental factors on Dungeness crab larval life (Lough 1975). 

However, Hobbs et al. (1992) (from northern California to Washington) and Roegner et al. 

(2003) (off southern Washington) did not find any correlations or significant relationships 

between sea surface temperature or salinity and Dungeness crab megalopal abundance. 

Hyperiid and gammarid amphipods were collected from the ocean surface during 2000 

and 2002. Gammarids may have been brought to the neustonic layer by subsurface water mixing 

and vertical transport, or in the case of nearshore species, many have been associated with 

drifting kelp or other algae. Gammarids were caught in previous zooplankton surveys off 

Oregon and Washington but not in large numbers or high occurrences (Brodeur et al. 1987, 

Schabetsberger et al. 2003). Hyperiids generally are considered to be commensal or even 

68
parasitic on gelatinous zooplankton, often inhabiting their cavities and tissues while young and 

riding on them while adults (Madin and Harbison 1977, Harbison et al. 1977, Laval 1980, 

Sorarrain et al. 2001). Therefore, the distribution of some hyperiids could be dependent on the 

distribution of their hosts (Madin and Harbison 1977, Harbison et al. 1977, Laval 1980, Sorarrain 

et al. 2001). Hyperoche medusarum have been associated with ctenophores (Beroe forskali), 

moon jelly and lion’s mane jelly, and comb jelly (Brusca 1970, Harbison et al. 1977, Laval 

1980). Themisto pacifica are parasites on medusae and salps (Laval 1980). The concomitant 

surface rope trawl catches included salps, ctenophores (Beroe spp.), moon jelly, and lion’s mane 

jelly. In addition, some of the neuston tows contained many Pleurobrachia spp., including P. 

bachei. While direct observations of living hyperiids parasitizing on these gelatinous 

zooplankton were not made during this survey, the possibility remains that the abundance and 

distribution of gelatinous zooplankters largely influenced the capture of hyperiids in neustonic 

zooplankton tows. Laval (1980) indicated that abundance and distribution of hyperiids caught in 

plankton tows may not be representative because of associations with their gelatinous hosts. 

Among the euphausiids, T. spinifera generally is considered a shelf species, while 

juvenile and adult Pacific krill are considered an offshore species; however, their distributions 

are stage dependent and often overlap (Gómez-Gutiérrez et al. 2005). Smiles and Pearcy (1971) 

reported that Pacific krill of all sizes were more abundant over the shelf than offshore, but that 

the larvae were more abundant inshore. Our analysis combined all life stages observed in the 

size fraction we examined and from the ocean surface, as opposed to deeper waters. Whereas we 

caught juveniles to adults, some of our samples had many furciliae within the size range from 4 

to 6 mm. Diel vertical migrations of both species have been observed over the continental shelf 

and in the California Current (Brinton 1962, Alton and Blackburn 1972, Youngbluth 1976). 

During the August 2002 diel study, this phenomenon was apparent in that most of the 

euphausiids were caught at night. Therefore, the data may be underestimated if one limits 

analysis to furciliae, and biased on the temporal and vertical distributions of each life stage. 

Thysanoessa raschii is a subarctic species that is rarely observed off Oregon and the single 

specimen of this species found in August 2002 was probably a result of the anomalously cold 

water intrusion during 2002.3

Chaetognaths were one of the most abundant organisms during all cruises. Along the 

Oregon and southern Washington coasts, chaetognaths dominated over other mesozooplankters 

in the water column throughout the summer of 1981 (Brodeur 1990). Chaetognaths also 

dominated in the Gulf of Alaska, where copepods were the dominant prey (Brodeur and Terazaki 

1999). The abundance and distribution of chaetognaths in this study, therefore, could be 

dependent on the availability of copepods as prey. However, few chaetognaths in our samples 

had copepods in their digestive tracts, despite many samples containing a high abundance of 

copepods below the 5-mm size fraction examined in this study. Off Oregon and northern 

California, the concentrations of neustonic chaetognaths in 2000 and 2002 were 2–8 times higher 

than in 1984 (Brodeur et al. 1987). 

Larval and juvenile fishes have been caught from the neuston and water column in 

ichthyoplankton surveys along the Pacific coast from Canada to California (Ahlstrom and 

 

3

 J. Gómez-Gutiérrez, Departmento de Plancton y Ecologia Marina, Col Playa de Santa Rita, La Paz, Mexico. Pers. 

commun., 31 January 2004. 

69
Stevens 1976, Richardson and Pearcy 1977, Richardson et al. 1980, Gruber et al. 1982, Shenker 

1988, Doyle 1992, Doyle et al. 2002). Fish larvae and juveniles were not very abundant in our 

survey compared to other ichthyoplankton surveys in this region, though we did collect many 

species that had been identified in previous surveys. Net avoidance during the day and diel 

vertical migration of fish larvae and juveniles could affect catches of ichthyoplankton in the 

neuston (Gruber et al. 1982, Shenker 1988, Doyle 1992). Ichthyoplankton surveys of just the 

Newport transect by Richardson and Pearcy (1977) and Shenker (1988) over several time periods 

provide an indication of seasonal abundance patterns in the larval and juvenile stages of many 

fishes. 

The associations among species generally appeared to be based on habitats, but they were 

not highly distinguishable. Many common pelagic taxa such as Cancer spp. megalopae, 

chaetognaths, Tomopteris sp., hippolytid larvae, T. spinifera, and grooved mussel crab zoeae and 

megalopae seemed to be clustered together. In 2000, Pacific saury juveniles and Pacific krill 

were grouped together, likely because of their offshore affinities, while also being associated 

with Hyperoche medusarum because all three species have similar spatial distributions. Shrimp 

zoeae and megalopae usually clustered together, which could be because of the timing of 

reproduction and the subsequent presence of larval stages at the ocean surface. Finally, 

terrestrial (insects) and benthic organisms (gammarids and isopods) generally were clustered, 

probably because of their proximity to shore. Any offshore distributions of these latter taxa 

could be explained by offshore dispersal caused by winds and Ekman transport. 

In the one previous comprehensive survey to date, Brodeur et al. (1987) sampled four 

transects between lat. 42.0°N and lat. 44.7°N from shore to about long. 124.7°W during three 

cruises in 1984. Much of their sampling was close to shore and to the north of the present study 

area (one cruise extended from Canada to southeast Alaska). In contrast, we sampled up to 18 

transects over a broader offshore area (i.e., to long. 126.0°W) more intensely during two 

summers. Therefore, direct comparison of abundance and distribution patterns of 

mesozooplankton in the neuston between these two studies is difficult. In a comparison between 

the June cruises in the present study and in the 1984 study, many dominant species were similar 

(Dungeness crab, Oregon cancer and red rock crab, Pacific krill, T. spinifera, and T. pacifica

[Parathemisto pacifica in the 1984 study]). A major difference was the relative paucity of 

terrestrial insects during the present study compared to 1984. Winds could affect the aerial 

distribution of small, weak-flying insects, and hence, their ocean surface abundance and 

distribution (Cheng 1977, Cheng 1978). An anomalous weather pattern, with winds blowing 

offshore from the coast, may have contributed to the overabundance of insects in the previous 

sampling (Brodeur et al. 1987, Brodeur 1989). Also, the previous work encompassed the end of 

a strong El Niño, which led to the occurrence of some warm-water southern species such as the 

euphausiid Nyctiphanes simplex, normally found only off southern California. 

Cruises during this study were 14–18 days long, covering a large area with constantly 

changing oceanographic conditions. The long duration of the cruises may have produced 

variations in the results at the fine-scale level. For instance, sampling the Heceta Head line on 2 

June 2002 then again on 9–10 June 2002 showed that species composition changes rapidly. For 

example, Dungeness crab megalopae were not caught at four of five stations on 2 June 2002 

(HH-1–HH-5), but they were found in high abundance 9–10 June 2002. The 1-m temperature, 

salinity, and density were similar (<1 unit of change) between these two sampling times, 

70
although chlorophyll a concentrations at the 3-m depth increased 2–14 times at three nearshore 

stations. During the August 2002 cruise on the same Heceta Head line, chlorophyll a

concentrations changed by a factor of 5 within a 14-day period. Timing of the offshore transport 

of megalopae, and an increase in primary productivity as indicated by chlorophyll a

concentrations, may have been more pronounced after we sampled the transect the first time. 

Therefore, the dynamics of environmental conditions and zooplankton life cycles could affect the 

temporal abundance and distribution of neustonic mesozooplankton at a single sampling 

location. 

71
Conclusion 

Mesozooplankton in the neustonic layer off Oregon and northern California differed in 

numerical abundance, taxa composition, and temporal and spatial distribution between sampling 

periods. Abundance and number of taxa observed were higher in 2002 than in 2000 and higher 

in June than in August. Cooler 1-m water temperatures and higher 3-m chlorophyll a

concentrations observed in 2002 are indicative of strong upwelling and may have positively 

affected neustonic mesozooplankton abundance and distribution. Dungeness crab megalopae 

and Oregon cancer and red rock crab megalopae, T. spinifera, Pacific krill, Hyperoche 

medusarum, T. pacifica, and Sagitta spp. were the commonly caught mesozooplankton during all 

four cruises. Fluctuations in abundance and distribution also can be attributed to zooplankton 

life histories, diel vertical migration, oceanographic conditions, and sampling net avoidance. 

72
References 

Ahlstrom, E. H., and E. Stevens. 1976. Report of neuston (surface) collections made on an extended 

CalCOFI cruise during May 1972. CalCOFI Rep. 18:167–180. 

Alton, M. S., and C. J. Blackburn. 1972. Diel changes in the vertical distribution of the euphausiids, 

Thysanoessa spinifera Holmes and Euphausia pacifica Hansen, in coastal waters of Washington. 

Calif. Fish Game 58(3):179–190. 

Arar, E. J., and G. B. Collins. 1997. Method 445.0: In vitro determination of chlorophyll a and 

pheophytin a in marine and freshwater algae by fluorescence. Revision 1.2. U.S. Environmental 

Protection Agency, Cincinnati, Ohio. 

Barth, J. A. 2003. Anomalous southward advection during 2002 in the northern California Current: 

Evidence from Lagrangian surface drifters. Geophys. Res. Lett. 30(15):8024. Online at 

http://dx.doi.org/ [DOI number 10.1029/2003GL017511, accessed 14 November 2005]. 

Barth, J. A., S. D. Pierce, and T. J. Cowles. 2005. Mesoscale structure and its seasonal evolution in the 

northern California Current system. Deep-Sea Res. II: Top. Stud. Oceanogr. 52(1-2):5–28. 

Barth, J. A., S. D. Pierce, and R. L. Smith. 2000. A separating coastal upwelling jet at Cape Blanco, 

Oregon and its connection to the California Current system. Deep-Sea Res. II: Top. Stud. 

Oceanogr. 47:783–810. 

Batchelder, H. P., J. A. Barth, M. P. Kosro, P. T. Strub, R. D. Brodeur, W. T. Peterson, C. T. Tynan, M. 

D. Ohman, L. W. Botsford, T. M. Powell, F. B. Schwing, D. G. Ainley, D. L. Mackas, B. M. 

Hickey, and S. R. Ramp. 2002. The GLOBEC Northeast Pacific California Current System 

program. Oceanography 15:36–47. 

Brinton, E. 1962. Variable factors affecting the apparent range and estimated concentration of 

euphausiids in the North Pacific. Pac. Sci. 16:374–408. 

Brodeur, R. D. 1989. Neustonic feeding by juvenile salmonids in coastal waters of the northeast Pacific. 

Can. J. Zool. 67:1995–2007. 

Brodeur, R. D. 1990. Abundance and distribution patterns of zooplankton along the Oregon and 

southern Washington coasts during the summer of 1981. Final rep. to the National Coastal 

Resources Research & Development Institute, Newport, Oregon. Univ. Washington, Fisheries 

Research Institute, Seattle. 

Brodeur, R. D. 1991. Ontogenetic variations in the type and size of prey consumed by juvenile coho, 

Oncorhynchus kisutch, and Chinook, O. tshawytscha, salmon. Environ. Biol. Fish. 30:303–315. 

Brodeur, R. D., and M. Terazaki. 1999. Springtime abundance of chaetognaths in the shelf region of the 

northern Gulf of Alaska, with observations on the vertical distribution and feeding of Sagitta 

elegans. Fish. Oceanogr. 8(2):93–103. 

73
Brodeur, R. D., J. P. Fisher, D. J. Teel, R. L. Emmett, E. Casillas, and T. W. Miller. 2004. Juvenile 

salmonid distribution, growth, condition, origin, and environmental and species associations in 

the Northern California Current. Fish. Bull. 102(1):25–46. 

Brodeur, R. D., B. C. Mundy, W. G. Pearcy, and R. W. Wisseman. 1987. The neustonic fauna in coastal 

waters of the northeast Pacific: Abundance, distribution, and utilization by juvenile salmonids. 

ORESU-T-87-001. Oregon Sea Grant Program, Oregon State Univ., Corvallis. 

Brusca, G. J. 1970. Notes on the association between Hyperoche medusarum A. Agassiz (Amphipoda, 

Hyperiidea) and the ctenophore, Pleurobrachia bachei (Müller). Bull. South. Calif. Acad. Sci. 

69(3–4):179–181. 

Cheng, L., and M. C. Birch. 1977. Terrestrial insects at sea. J. Mar. Biol. Assoc. U.K. 57:995–997. 

Cheng, L., and M. C. Birch. 1978. Insect flotsam: An unstudied marine resource. Ecol. Entomol. 

3:87–97. 

Doyle, M. J. 1992. Neustonic ichthyoplankton in the northern region of the California Current 

ecosystem. CalCOFI Rep. 33:141–161. 

Doyle, M. J., K. L. Mier, M. S. Busby, and R. D. Brodeur. 2002. Regional variations in springtime 

ichthyoplankton assemblages in the northeast Pacific Ocean. Prog. Oceanogr. 53:247–281. 

Gómez-Gutiérrez, J., W. T. Peterson, and C. B. Miller. 2005. Cross-shelf life-stage segregation and 

community structure of the euphausiids off central Oregon (1970–1972). Deep-Sea Res. II: Top. 

Stud. Oceanogr. 52(1-2):289–315. 

Gruber, D., E. H. Ahlstrom, and M. M. Mullin. 1982. Distribution of ichthyoplankton in the southern 

California bight. CalCOFI Rep. 23:172–179. 

Harbison, G. R., D. C. Biggs, and L. P. Madin. 1977. The associations of Amphipoda Hyperiidea with 

gelatinous zooplankton — II. Associations with Cnidaria, Ctenophora and Radiolaria. Deep-Sea 

Res. 24:465–488. 

Hempel, G., and H. Weikert. 1972. The neuston of the subtropical and boreal northeastern Atlantic 

Ocean. A review. Mar. Biol. 13:70–88. 

Hickey, B. M., and N. S. Banas. 2003. Oceanography of the U.S. Pacific Northwest coastal ocean and 

estuaries with application to coastal ecology. Estuaries 26(4B):1010–1031. 

Hobbs, R. C., L. W. Botsford, and A. Thomas. 1992. Influence of hydrographic conditions and wind 

forcing on the distribution and abundance of Dungeness crab, Cancer magister, larvae. Can. J. 

Fish. Aquat. Sci. 49:1379–1388. 

Holdway, P., and L. Maddock. 1983. A comparative survey of neuston: Geographical and temporal 

distribution patterns. Mar. Biol. 76:263–270. 

Huyer, A. 1983. Coastal upwelling in the California Current system. Prog. Oceanogr. 12:259–284. 

Jamieson, G. S., A. C. Phillips, and W. S. Huggett. 1989. Effects of ocean variability on the abundance 

of Dungeness crab (Cancer magister) megalopae. In R. J. Beamish and G. A. McFarlane (eds.), 

74
Effects of ocean variability on recruitment and an evaluation of parameters used in stock 

assessment models, p. 305–325. Can. Spec. Publ. Fish. Aquat. Sci. 108. 

Johnson, J., and A. L. Shanks. 2002. Time series of the abundance of the post-larvae of the crabs Cancer 

magister and Cancer spp. on the southern Oregon coast and their cross-shelf transport. Estuaries 

25(6A):1138–1142. 

Kosro, P. M. 2003. Enhanced southward flow over the Oregon shelf in 2002: A conduit for subarctic 

water. Geophys. Res. Lett. 30(15):8023. Online at http://dx.doi.org/ [DOI number 

10.1029/2003GL017436, accessed 15 November 2005]. 

Laval, P. 1980. Hyperiid amphipods as crustacean parasitoids associated with gelatinous zooplankton. 

Oceanogr. Mar. Biol. Annu. Rev. 18:11–56. 

Levinton, J. S. 1982. Marine ecology. Prentice-Hall, Inc., Englewood Cliffs, NJ. 

Lough, R. G. 1975. Dynamics of crab larvae (Anomura, Brachyura) off the central Oregon coast, 

1969–1971. Doctoral thesis. Oregon State Univ., Corvallis. 

Madin, L. P., and G. R. Harbison. 1977. The associations of Amphipoda Hyperiidea with gelatinous 

zooplankton — I. Associations with Salpidae. Deep-Sea Res. 24:449–463. 

Murphree, T., S. J. Bograd, F. B. Schwing, and B. Ford. 2003. Large scale atmosphere-ocean anomalies 

in the northeast Pacific during 2002. Geophys. Res. Lett. 30(15):8026. Online at 

http://dx.doi.org/ [DOI number 10.1029/2003GL017303, accessed 15 November 2005]. 

Peres, J. M. 1982. 7. Specific pelagic assemblages. Mar. Ecol. 5(91):313–372. 

Peterson, W. T., and J. E. Keister. 2002. The effect of a large cape on distribution patterns of coastal and 

oceanic copepods off Oregon and northern California during the 1998–1999 El Niño-La Niña. 

Prog. Oceanogr. 53:389–411. 

Reese, D. C., T. W. Miller, and R. D. Brodeur. 2005. Community structure of near-surface zooplankton 

in the northern California Current in relation to oceanographic conditions. Deep-Sea Res. II: 

Top. Stud. Oceanogr. 52:29–50. 

Richardson, S. L., J. L. Laroche, and M. D. Richardson. 1980. Larval fish assemblages and associations 

in the north-east Pacific Ocean along the Oregon coast, winter-spring 1972–1975. Estuar. Coast. 

Mar. Sci. 11:671–699. 

Richardson, S. L., and W. G. Pearcy. 1977. Coastal and oceanic fish larvae in an area of upwelling off 

Yaquina Bay, Oregon. Fish. Bull. 75(1):125–145. 

Roegner, G. C., D. A. Armstrong, B. M. Hickey, and A. L. Shanks. 2003. Ocean distribution of 

Dungeness crab megalopae and recruitment patterns to estuaries in southern Washington state. 

Estuaries 26(4B):1058–1070. 

Schabetsberger, R., C. A. Morgan, R. D. Brodeur, C. L. Potts, W. T. Peterson, and R. L. Emmett. 2003. 

Prey selectivity and diel feeding chronology of juvenile Chinook (Oncorhynchus tshawytscha) 

and coho (O. kisutch) salmon in the Columbia River plume. Fish. Oceanogr. 12(6):523–540. 

75
Shenker, J. M. 1988. Oceanographic associations of neustonic larval and juvenile fishes and Dungeness 

crab megalopae off Oregon. Fish. Bull. 86(2):299–317. 

Smiles, M. C., Jr., and W. G. Pearcy. 1971. Size structure and growth rate of Euphausia pacifica off the 

Oregon coast. Fish. Bull. 69(1):79–86. 

Spellerberg, I. F., and P. J. Fedor. 2003. A tribute to Claude Shannon (1916–2001) and a plea for more 

rigorous use of species richness, species diversity and the ‘Shannon-Wiener’ index. Global Ecol. 

Biog. 12:177–179. 

Sorarrain, D. R., F. Ramirez, and H. Mianzan. 2001. Hyperoche medusarum (Krøyer, 1838) 

(Amphipoda, Hyperiidae) and Mnemiopsis mccradyi (Mayer, 1910) (Ctenophora): A new host 

and first record of this association for the southwestern Atlantic. Crustaceana 74(4):407–410. 

Strub, P. T., and C. James. 2003. Altimeter estimates of anomalous transports into the northern 

California Current during 2000–2002. Geophys. Res. Lett. 30(15):8025. Online at 

http://dx.doi.org/ [DOI number 10.1029/2003GL017513, accessed 15 November 2005]. 

Valiela, I. 1995. Marine Ecological Processes. Second edition. Springer-Verlag, New York. 

Wheeler, P. A., A. Huyer, and J. Fleischbein. 2003. Cold halocline, increased nutrients and higher 

chlorophyll off Oregon in 2002. Geophys. Res. Lett. 30(15):8021. Online at http://dx.doi.org/ 

[DOI number 10.1029/2003GL017395, accessed 15 November 2005]. 

Youngbluth, M. J. 1976. Vertical distribution and diel migration of euphausiids in the central region of 

the California Current. Fish. Bull. 74(4):925–936. 

Zaitsev, Y. P. 1970. Marine neustonology. Naukova Dumka, Kiev, Russia. (Translated from Russian to 

English by Israel Program for Scientific Translations, Jerusalem. Available from National 

Technical Information Service, 5285 Port Royal Road, Springfield, VA.) 

76
Most NOAA Technical Memorandums NMFS-NWFSC are available online at the

Northwest Fisheries Science Center web site (http://www.nwfsc.noaa.gov).

Recent NOAA Technical Memorandums NMFS

published by the

Northwest Fisheries Science Center

NOAA Tech. Memo.

NMFS-NWFSC73 Myers, J., C. Busack, D. Rawding, A. Marshall, D. Teel, D.M. Van Doornik, and M.T. Maher. 2006.

Historical population structure of Pacific salmonids in the Willamette River and lower Columbia River

basins. U.S. Dept. Commer., NOAA Tech. Memo. NMFS-NWFSC-73, 311 p. NTIS number pending.

72 Keller, A.A., E.L. Fruh, K.L. Bosley, D.J. Kamikawa, J.R. Wallace, B.H. Horness, V.H. Simon, and V.J.

Tuttle. 2006. The 2001 U.S. West Coast upper continental slope trawl survey of groundfish resources off

Washington, Oregon, and California: Estimates of distribution, abundance, and length composition. U.S.

Dept. Commer., NOAA Tech. Memo. NMFS-NWFSC-72, 175 p. NTIS number pending.

71 Nash, C.E., P.R. Burbridge, and J.K. Volkman (editors). 2005. Guidelines for ecological risk assessment

of marine fish aquaculture. U.S. Dept. Commer., NOAA Tech. Memo. NMFS-NWFSC-71, 90 p. NTIS

number pending.

70 Keller A.A., T.L. Wick, E.L. Fruh, K.L. Bosley, D.J. Kamikawa, J.R. Wallace, and B.H. Horness.

2005. The 2000 U.S. West Coast upper continental slope trawl survey of groundfish resources off

Washington, Oregon, and California: Estimates of distribution, abundance, and length composition. U.S.

Dept. Commer., NOAA Tech. Memo. NMFS-NWFSC-70, 163 p. NTIS number pending.

69 Fresh, K.L., E. Casillas, L.L. Johnson, and D.L. Bottom. 2005. Role of the estuary in the recovery of

Columbia River basin salmon and steelhead: An evaluation of the effects of selected factors on salmonid

population viability. U.S. Dept. Commer., NOAA Tech. Memo. NMFS-NWFSC-69, 105 p. NTIS number

pending.

68 Bottom, D.L., C.A. Simenstad, J. Burke, A.M. Baptista, D.A. Jay, K.K. Jones, E. Casillas, and M.H.

Schiewe. 2005. Salmon at river's end: The role of the estuary in the decline and recovery of Columbia

River salmon. U.S. Dept. Commer., NOAA Tech. Memo. NMFS-NWFSC-68, 246 p. NTIS PB2006-

101123.

67 Holmes, E.E., W.F. Fagan, J.J. Rango, A. Folarin, J.A. Sorensen, J.E. Lippe, and N.E. McIntyre.

2005. Cross validation of quasi-extinction risks from real time series: An examination of diffusion

approximation methods. U.S. Dept. Commer., NOAA Tech. Memo. NMFS-NWFSC-67, 37 p. NTIS

number pending.

66 Good, T.P., R.S. Waples, and P. Adams (editors). 2005. Updated status of federally listed ESUs of West

Coast salmon and steelhead. U.S. Dept. Commer., NOAA Tech. Memo. NMFS-NWFSC-66, 598 p. NTIS

PB2005-110650.

65 Fleischer, G.W., K.D. Cooke, P.H. Ressler, R.E. Thomas, S.K. de Blois, L.C. Hufnagle, A.R. Kronlund,

J.A. Holmes, and C.D. Wilson. 2005. The 2003 integrated acoustic and trawl survey of Pacific hake,

Merluccius productus, in U.S. and Canadian waters off the Pacific coast. U.S. Dept. Commer., NOAA

Tech. Memo. NMFS-NWFSC-65, 45 p. NTIS PB2005-110651.