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| Dataset Title: | Groundfish Data for U.S. West Coast (2003-2005) |
| Dataset ID: | nwioosGroundfish |
| Institution: | NOAA NWFSC |
| Information: | Summary
| Variables
| Background | Data Access Form
|
|
Attributes {
s {
longitude {
String _CoordinateAxisType "Lon";
Float64 actual_range -125.8555, -117.2767;
String axis "X";
Float64 colorBarMaximum -115.0;
Float64 colorBarMinimum -135.0;
String ioos_category "Location";
String long_name "Longitude";
String standard_name "longitude";
String units "degrees_east";
}
latitude {
String _CoordinateAxisType "Lat";
Float64 actual_range 32.5708, 48.4525;
String axis "Y";
Float64 colorBarMaximum 55.0;
Float64 colorBarMinimum 30.0;
String ioos_category "Location";
String long_name "Latitude";
String standard_name "latitude";
String units "degrees_north";
}
time {
String _CoordinateAxisType "Time";
Float64 actual_range 1.0413792e+9, 1.1045376e+9;
String axis "T";
Float64 colorBarMaximum 2005.0;
Float64 colorBarMinimum 2003.0;
String Description "Year the survey cycle was performed.";
String ioos_category "Time";
String long_name "Survey Year";
String standard_name "time";
String time_origin "01-JAN-1970 00:00:00";
String units "seconds since 1970-01-01T00:00:00Z";
}
haul_id {
Float64 actual_range 2.003030016e+11, 2.00503009536e+11;
String ioos_category "Identifier";
String long_name "Haul Identifier";
}
scientific_name {
String ioos_category "Taxonomy";
String long_name "Scientific Name";
}
common_name {
String ioos_category "Taxonomy";
String long_name "Common Name";
}
position_description {
String Description
"Type of position reported for the haul, typically the gear track midpoint or
the vessel track midpoint.";
String ioos_category "Location";
String long_name "Position Description";
}
catch_range_min {
Float64 actual_range 0.0, 4530.0;
Float64 colorBarMaximum 4500.0;
Float64 colorBarMinimum 0.0;
String Description "Catch range minimum (catch per unit effort in kilograms per square meter).";
String ioos_category "Fish Abundance";
String long_name "Catch Range Min";
String units "kg km-2";
}
catch_range_max {
Float64 actual_range 0.0, 257606.0;
Float64 colorBarMaximum 250000.0;
Float64 colorBarMinimum 0.0;
String Description "Catch range maximum (catch per unit effort in kilograms per square meter).";
String ioos_category "Fish Abundance";
String long_name "Catch Range Max";
String units "kg km-2";
}
map_legend {
Float64 colorBarMaximum 250000.0;
Float64 colorBarMinimum 0.0;
String Description
"Indicates the catch per unit effort range that characterizes the haul catch
for a species. Catch ranges are bounded by whole number standard deviation
increments. Zero catch is indicated in a distinct category.";
String ioos_category "Fish Abundance";
String long_name "Map Legend";
String units "kg km-2";
}
}
NC_GLOBAL {
String cdm_data_type "Point";
String Conventions "COARDS, CF-1.0, Unidata Dataset Discovery v1.0";
Float64 Easternmost_Easting -117.2767;
Float64 geospatial_lat_max 48.4525;
Float64 geospatial_lat_min 32.5708;
String geospatial_lat_units "degrees_north";
Float64 geospatial_lon_max -117.2767;
Float64 geospatial_lon_min -125.8555;
String geospatial_lon_units "degrees_east";
String history
"2009-02-17 http://nwioos.coas.oregonstate.edu:8080/dods/drds/Groundfish%
20Survey%202003-2006
2009-02-17 http://coastwatch.pfeg.noaa.gov/tabledap/nwioosGroundfish.das";
String infoUrl
"http://nwioos.coas.oregonstate.edu:8080/dods/drds/Groundfish%20Survey%202003-
2005.info";
String institution "NOAA NWFSC";
String license
"The data may be used and redistributed for free but is not intended
for legal use, since it may contain inaccuracies. Neither the data
Contributor, ERD, NOAA, nor the United States Government, nor any
of their employees or contractors, makes any warranty, express or
implied, including warranties of merchantability and fitness for a
particular purpose, or assumes any legal liability for the accuracy,
completeness, or usefulness, of this information.";
Float64 Northernmost_Northing 48.4525;
String sourceUrl
"http://nwioos.coas.oregonstate.edu:8080/dods/drds/Groundfish%20Survey%202003-
2006";
Float64 Southernmost_Northing 32.5708;
String standard_name_vocabulary "CF-1.0";
String summary
"The data available for downloading is summarized data from the 2003-2005
U.S. West Coast Bottom Trawl Survey (WCGTS) of Groundfish Resources off
Washington, Oregon and California.
SUMMARY
The Northwest Fisheries Science Center's Fishery Resource Analysis and
Monitoring Division (FRAM) completed the sixth in an annual series of
groundfish bottom trawl surveys in 2003. The survey was conducted June
24 to October 23, 2003 and targeted the commercial groundfish resources
inhabiting depths of 55 to 1,280 meters [m], (30 - 700 fathoms [fm])
from the area off Cape Flattery, Washington (latitude [lat.] 48°10'N)
to the U.S.-Mexican border (lat. 32°30'N) using chartered West Coast
commercial trawlers. These ongoing series of annual surveys, conducted
by FRAM since 1998, are designed to monitor long-term trends in
distribution and abundance of west coast groundfish, especially those
species of management concern. The 2003 survey represents the first
year in which the depth range was expanded to include both the
continental shelf (55 - 183 m) and continental slope (183 - 1,280 m)
area and the first year in which a stratified-random sampling design
was adopted.
In 2003, 620 primary sampling sites, and associated secondary sites,
were selected randomly prior to the start of the survey. Trawling
locations were allocated according to a stratified-random sampling
design that divided the region into two geographic areas (north and
south of Pt. Conception, CA and three depth zones (strata). The
objective was to provide a representative sample of the various
groundfish species and relative numbers in each stratum. By selecting
random stations within certain depth zones, towable ground has an
equal probability of being sampled during the survey. Thus, the
method produces unbiased estimates of the relative stock size. In
2003, a total of 574 successful tows were completed out of 643
attempts. Simrad ITI net mensuration data, as well as global
positioning system (GPS) navigation data and bottom contact sensor
data, used to document performance (e.g. bottom tending), were
obtained for most tows.
An Aberdeen-style net with a small mesh (2\" stretched measure or less)
liner in the codend (to retain smaller specimens) was used to sample
fish biomass. Target duration of each tow was 15 minutes. Tow
duration was the time between touchdown and lift-off of the trawl net
from the seafloor based on readings from bottom contact sensors.
Catches were sorted to species, aggregate or other appropriate
taxonomic level and then weighed using an electronic,
motion-compensated scale. A total of 517 species or families (fish
and invertebrates) were identified within the survey area. Although
biological sampling effort continues to include Dover sole
(Microstomus pacificus), shortspine thornyhead (Sebastolobus
alascanus), longspine thornyhead (Sebastolobus altivelis), and
sablefish (Anoplopoma fimbria), focus has increasingly shifted to
encompass all groundfish species of management concern. Up to 100
length measurements, sex determinations, and individual weights
and up to 25 age structures were collected per haul for these species.
SURVEY METHODS
Survey Period and Sampling Area
The 2003 WCGTS was conducted in two completed cycles of operations,
or passes, between June 24 and October 23, 2003 from the areas off
Cape Flattery, Washington (lat. 48°10'N), to the U.S. - Mexican
border (lat. 32°30'N). Four West Coast bottom trawlers were
chartered through the standard competitive bid process. The Fishing
Vessel (FV) Ms. Julie and the FV Captain Jack were used during the
first survey period, from June 24 to August 13, 2003, and two
additional vessels, the FV Excalibur and the FV Blue Horizon, were
used during the second survey period, from August 31 to October 23,
2003. All vessels started their operations off Cape Flattery, and
then progressed south along the coast, finishing the completed cycle
south of San Diego, CA[w1].
Vessels and Sampling Gear
The four chartered fishing vessels ranged in size from 65 to 92 feet
(19.8 to 28.0 meters) and in power from 450 to 775 horsepower. Each
vessel was rigged as a stern trawler; with a rear gantry housing one
or two net reels to set and retrieve trawl gear. Vessels were
outfitted with split trawl winches and equipped with modern
electronics including global positioning systems (GPS), multiple
depth sounders, radars, and other navigational aids. Prior to the
start of the survey, the NWFSC provided each vessel with two 5/8\"
steel core trawl cables, each 2,288 m (1,250 fm) in length. Cables
were measured side-by-side and marked at 25 fm increments while being
spooled onto the vessel's winches. The markings provided real-time
verification of the release of equal warp length from both winches
while setting a tow.
All vessels were provided with two standard Aberdeen-style nets built
and rigged to operate within strict specifications in compliance with
protocols established for bottom trawl surveys (Stauffer 2004). The
Aberdeen trawl is routinely used by fishers throughout the survey
region and was chosen after substantial analysis of trawl performance
over various towing situations. The Aberdeen trawl demonstrated
relatively stable performance over the range of conditions expected
during the survey (West et al. 1998). Each net was outfitted with
a small-mesh liner (1 ½\" stretched measure, #24 twisted polypropylene)
in the codend to retain smaller fish. Various aspects of the
mechanical performance of the nets (e.g., spread between net wings,
vertical distance from the center of the headrope to the bottom,
distance from the headrope to the footrope, and clearance between the
footrope and bottom) were recorded using acoustic and bottom contact
instruments hung from the net during each deployment. Additional
information was recorded on operational conditions such as: depth,
amount of towing cable deployed, towing speed, tow duration, and
weather conditions.
Trawl Station Allocation
From 1998 through 2002 selection of sample sites for the WCGTS was
based on a fixed transect design. Following an evaluation of the
transect-based survey design by assessment and survey scientists, a
stratified-random sampling design was adopted in 2003. The survey
area was partitioned into ~12,000 adjacent cells of equal area (1.5 nm
long. by 2.0 nm lat., Albers Equal Area projection) with each vessel
assigned a primary subset of 155 [w2]randomly selected cell sites.
In 2003, sampling density was assigned to areas defined by
International Pacific Fishery Council
Management Areas and specified depth categories. In 2003, sampling
locations were allocated by assigning 16 - 25 % of the effort within
each INPFC area. This allocation scheme was adopted to maintain a
level of sampling effort in the slope area (184 - 1,280 m) comparable
to prior years and to account for bathymeyric disparity between the
areas. The survey area was further stratified into three depth zones
(55 - 183 m, 184 - 549 m and 550 - 1,280 m). Emphasis was placed on
continuing a level of effort in the 184 - 549 m and 550 - 1,280 m
depth strata similar to past surveys while maintaining a minimum of 30
tows per strata. The total number of sites targeted for the survey
year was apportioned across geographic area and depth categories,
based on the above scheme, and then primary stations were drawn from
the survey cell pool, by strata, using a pseudo random number
generator. Each cell was sequentially assigned to an individual vessel.
The process was repeated to identify two alternate sampling sites per
location; additional constraints were imposed to ensure alternate sites
were neither so close to an untrawlable primary site that they exhibit
the same untrawlable features, nor were at an impractical transit
distance.
In 2003, 620 primary sites were selected with each vessel assigned 155
tows (one tow per cell). A total of 574 successful tows were completed
out of 643 attempts[w3].
Trawling Protocol
Standard trawl operations were followed to minimize differences in
sampling (fishing) efficiency across the range of conditions
encountered during the survey and over time (Stauffer, 2004). By
established conventions, trawling operations were limited to the
daylight period, i.e., initial tow each day began (net on seafloor)
following official sunrise, and the last tow of the day ended (net
off seafloor) before official sunset. Once a vessel was in the
pre-selected sampling area (1.5 by 2.0 nm cell), the captain was
instructed to observe the following search rules to identify a
specific tow site: 1) search within the specified depth range; 2)
remain fully within the specified area; and 3) complete the search
for trawlable ground within 1 hour. If no trawlable site was found
within the 1-hour limit, the cell was noted in the log as untrawlable
and the vessel proceeded to the secondary cell. If the secondary cell
also proved untrawable, the tertiary cell was attempted next. If a tow
was attempted but judged unsatisfactory, or if the tow was aborted, a
reasonable attempt was made to redo the tow within the primary site
before proceeding to alternate sites.
All fishing operations, including vessel operations and gear
performance were monitored using a suite of trawl instrumentation
systems. The NMFS-supplied differential global positioning system
(GPS) navigation unit (Northstar 500 [Footnote1] or the vessel's speed
indicators were used to monitor towing speed for each survey haul
(target 2.2 knots over ground). All hauls were additionally monitored
using the Simrad Integrated Trawl Instrumentation (ITI [Footnote 2])
system. Four sensors from the ITI trawl system were attached to the
net prior to setting the gear. Two instruments were mounted on the
center of the net headrope: the trawleye provided information on the
vertical opening of the trawl, distance to the seafloor, and footrope
clearance above the bottom, and the temperature-depth sensor recorded
ambient temperature and the depth of the trawl headrope. Paired wing
units (communication sensor and remote sensor) were attached on the
port and starboard wings of the net to measure wing spread. Extreme
or prolonged periods of abnormal wing spread were indicative of net
performance problems. Wing spread provided an indicator of the net's
contact with the bottom and whether adequate scope (amount of wire
deployed) was utilized. With too little scope the gear tends bottom
poorly, while too much scope may impact the proper spread of the
doors. The captain, relying on past experience and judgment, determined
the initial scope at the start of each tow. Guidelines for initial
scope, tailored to local conditions and vessels, were provided for
use at the discretion of the captain. Since the ITI trawl instruments
displayed gear performance in real time adjustments to the scope were
made if necessary. Scope was adjusted by deploying additional wire until
the gear made stable, consistent bottom contact according to the ITI
display. The Simrad ITI also provided geo-referenced trawl positions
relative to ship position, supplying a means to track the trawl
location along the seafoor throughout each tow.
A pair of bottom contact sensors (BCSs) and a secondary
temperature/depth recorder (Seabird SBE39 [Footnote 3]) were also
deployed on every haul. The BCSs were attached four feet from the
center-point of the footrope, on either side of the net. The BCSs
recorded the angle of incline of the net, indicating when the net
landed on and lifted off bottom and provided redundancy in the event
that the ITI failed to perform adequately. The Seabird
temperature/depth recorder was attached to the head rope in an ABS
plastic sleeve. The BCS and Seabird temperature/depth data were
reviewed following every haul to provide additional information on
bottom contact and trawl performance. In addition to monitoring trawl
performance, the data from the sensor systems (Simrad ITI, BCS and
Seabird) were used to calculate net dimensions (net height and net
width), duration of the tow, and distance fished.
While gear was being set, vessel speeds varied from 2.2 to 5 kn.
After the net made contact with the bottom, vessel speed was targeted
at 2.2±0.5 kn. The haul officially began when the net was in proper
fishing configuration and maintained steady contact with the bottom.
The haul ended when the net lifted off the bottom after the start of
haulback. Tow duration was targeted at 15 minutes. The Simrad ITI
trawl eye was used to monitor ground-gear contact during a haul, but
the actual bottom time was determined using data from the BCS.
Position data, collected at 2-second intervals for each haul using a
GPS, were used to monitor ground speed, track the vessel path, and
estimate distance fished. Average vessel speed over ground and distance
fished were calculated from the position data and the trawl's actual
bottom time. All features of the \"trawl event\" (i.e. from commencement
of the deployment of the net to the completion of retrieval of the net)
including net mensuration information, GPS data, trawl location, scope,
vessel depth, trawl gear depth, and sea state conditions, were logged
using a customized software program called 'Towlogger'.
Following every haul, data were reviewed to determine a performance
rating for each tow. A tow was classified as unsatisfactory if gear was
severely damaged during a haul since damage to the gear might affect
catch composition. Moreover, if gear performance was otherwise deemed
unacceptable (e.g. large quantities of mud or jellyfish, lost or
abandoned fishing gear ensnared in the net, net off bottom for an
extended period during the tow etc.), the tow was also rated as
unsatisfactory. Unsatisfactory hauls were not included in this data
set.
Sampling Procedures and Biological Data Collection
Catches were sorted to species or other appropriate taxonomic levels
and then weighed in aggregate using an electronic, motion-compensated
scale (Marel, hf. [Footnote 4]). Subsamples of important management
species were randomly selected for individual measurements (length and
weights) and biological sampling (age structures and sex
determinations). Up to 100 sex determinations and length measurements
(to the nearest cm) were collected per haul from each of these species.
Although fork length (or total length) was generally measured for most
species, anal length was recorded for Pacific grenadier (Coryphaenoides
acrolepis) and spotted ratfish (Hydrolagus colliei).
Otoliths were most commonly removed to determine age; however,
exceptions to the use of otoliths included collection of: fin rays
from lingcod (Ophiodon elongates) and second dorsal spines from spiny
dogfish (Squalus acanthias). Fish were randomly selected for aging
from the subset of fish chosen for length determination. Up to 25
individuals per species were targeted for otolith (or other age
structure) removal per haul. Individual lengths and weights were
collected from all fish selected for age structure removal. For other
species, only total counts and aggregate weights were recorded, except
when additional information was collected for special projects
(including stomach contents, tissue samples, fecundity, and toxicology).
Data were logged wirelessly into a ruggedized Itronix3 notebook computer
(Itronix Corp. [Footnote 5]) using the Fisheries Scientific Computing
System (FSCS) version 1.6.
Any unidentified species were labeled, frozen or preserved in formalin
and retained for later identification. After all biological data were
collected; marketable fish were placed in the hold of the vessel, iced
and then delivered to a shoreside processing facility within 5 days.
Species with no commercial value or those with catch prohibitions were
returned to the sea as soon as possible.
[Footnote 1] Northstar Technologies, 30 Sudbury Rd., Acton, MA 01720.
[Footnote 2] Kongsberg Simrad Mesotech Ltd., 1598 Kebet Way, Port
Coquitlam, BC V3C 5M5, Canada.
[Footnote 3] Sea-Bird Electronics, Inc., 1808 136th Place NE, Bellevue,
WA 98005 USA
[Footnote 4] Marel, hf., Hofdabakki 9, 110 Reykjavik, Iceland.
+354 563 8000.
[Footnote 5] Itronix Corp.12825 E. Mirabeau Parkway, Spokane Valley,
WA 99216-1464
CONTACT
Beth Horness
Northwest Fisheries Science Center
Fisheries Resource Analysis and Monitoring Division
2725 Montlake Blvd. E
Seattle WA 98112";
String time_coverage_end "2005-01-01T00:00:00Z";
String time_coverage_start "2003-01-01T00:00:00Z";
String title "Groundfish Data for U.S. West Coast (2003-2005)";
Float64 Westernmost_Easting -125.8555;
}
}
tabledap request URLs must be in the form
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For example,
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ERDDAP Version 1.12