Body Text for Appendix XX: Distribution of standardized survey catch of
corals and sponges, comparing two time periods.
Map Book file name:
Map Book file name:
Map Book file name:
Map Book file name:
Task3_WCGBTS_CoralCPUE_MapBook.pdf
Task3_WCGBTS_CoralSpongeCPUE_MapBook.pdf
Task3_WCGBTS_PennCPUE_MapBook.pdf
Task3_WCGBTS_SpongeCPUE_MapBook.pdf
Appendix XX figures depict the spatial distribution of standardized survey catch of
corals and sponges within two time periods: “Before” (2003-05 survey cycles) and
“After” (2006-10 survey cycles) implementation of Amendment 19 regulations. The
sole data source for the map layers is catch records from the West Coast Groundfish
Bottom Trawl Survey (WCGBTS). Since 2003, the WCGBTS has been a combined
survey of demersal species residing in both continental shelf (i.e., 30-100 ftm) and
slope (i.e., 100-700 ftm) habitats. Each year, the WCBGTS sampled ~750 stations
during two passes (May-Jul, Aug-Oct) operating north to south from the Canadian to
Mexican maritime borders. Tow durations were targeted at 15 minutes, with a
mean tow distance of 1.4 km. Invertebrates in the catch were sorted, weighed and
identified down to the lowest possible taxonomic level. Consequently, taxonomic
resolution was dependent upon the expertise of onboard biologists. A full
description of the survey design and protocols can be found in past cruise reports
at: http://www.nwfsc.noaa.gov/research/divisions/fram/index.cfm.
Like previous descriptions of methods for creating density layers, a straight line
connecting the start and end points was used to represent each tow event. And
similar to standardized bycatch layers developed from observer data, standardized
survey catch is the quotient of catch density (numerator) and effort density
(denominator). Because survey tows were much shorter in length than the average
commercial tow (mean of 1.3 vs. 12.2 km) and because they were much less
numerous, a larger search radius (6km) was used. The resulting density values
were applied to the same 500x500 m cell size as was other density products (e.g.,
fishing effort, standardized bycatch).
Sponges were more common in the catch than corals, and accounted for the top six
taxa by standardized weight (CPUE) in the period from 2003-10 (Table XX). Two
pennatulid taxa were the next most abundant, with gorgonians and then black
corals being the most frequently recorded of all non-pennatulid coral taxa. Any
significant changes in the frequency or standardized catch of taxa between the two
time periods should be interpreted with caution, as the ability of onboard biologists
to identify corals in the catch has improved throughout time.
In order to evaluate how fishing effort has changed between the two time periods,
the color ramps for the intensity layers are scaled to the same range of values in
each panel (Fig. XX-XX). Blue- (red-) shaded areas represent the lowest (highest)
relative effort in both time periods. The value in the map legends is the lowest
“high” value between the time periods. It was necessary to set the color ramp to the
lowest “high” value in order for the colors in each panel to perfectly match and
therefore be comparative.
In the maps showing standardized catch of corals excluding sea pens/whips (Fig.
XX-XX), areas of highest relative CPUE occurred off northern California (Map 3) in
both time periods. Two areas off northern Washington show moderate CPUE, one
within the Olympic 2 EFH conservation area in the recent time period.
In the maps showing sponges only (Fig. XX-XX), the areas of highest relative CPUE
occurred off southern California, two sites in the before period and one in the after
(Map 7). The one area of highest CPUE in the recent time period also showed
relative moderate catches of sponges in the before period. Other areas of moderate
catch of sponges occurred near the Eel River Canyon (Map 4, before) and off central
Oregon in both time periods (Map 2).
Areas of highest CPUE for sea pens/whips (Fig. XX-XX) occurred off northern and
central Oregon (Map 2) and central California (Map 7). Other areas of moderate
CPUE are apparent off San Francisco in the recent time period (Map 5) and central
(Map 7) and southern California (Map 8 and 9).
One important consideration when evaluating catch records of invertebrates from
trawl surveys is the sampling gear itself. Bottom trawl gear used in the WCGBTS is
not designed to sample sessile invertebrates, nor is it designed to access many of the
preferred habitats for coral and sponge settlement. Regardless of the limitations of
the gear, corals or sponges were recorded in almost half of all survey tows (see
Table XX). Recall that survey tows are much shorter in duration than commercial
tows, and vessel captains can often prosecute a tow in areas where they normally
wouldn’t during commercial operations. This may in part account for the fact that
corals and sponges are recorded more frequently in survey catches (see Appendix
XX, Table XX [WCGOP documentation]).
Table XX. Summary of coral and sponge taxa recorded during tows as part of the West Coast Groundfish
Bottom Trawl Survey (WCGBTS), comparing two time periods: “Before” (2003-05) and “After” (200610). “#” denotes number of tows with recorded bycatch; “FREQ” denotes ratio of tows with catch to total
tows recorded; “CPUE” denotes catch per unit of effort (units: kg/ha). Tow counts represent only those
where corals or sponges were present in the catch. Taxa are listed in descending order of CPUE for
combined time period.
Taxon
#
Porifera
359
Hexactinosida
103
Rossellinae
53
Suberites spp.
3
Hyalonema spp.
47
Hexactinellida
17
Pennatulacea
245
Anthoptilum grandiflorum
98
Chrysopathes spp.
0
Antipatharia
66
Halipteris spp.
0
Gorgonacea
58
Anthomastus ritteri
16
Ptilosarcus gurneyi
28
Alcyonacea
14
Anthomastus spp.
19
Callogorgia kinoshitae
4
Umbellula spp.
23
Paragorgia spp.
6
Isidella spp.
1
Scleractinia
4
Farrea spp.
5
Anthoptilum murrayi
4
Flabellidae
2
Caryophylliidae
1
Bathypathes spp.
6
Keratoisis spp.
2
Stylasteridae
1
Lillipathes spp.
3
Callogorgia spp.
1
Pennatula phosphorea
1
Acanthogorgiidae
0
Combined
749
Total Hauls /Time Period
1,652
BEFORE
AFTER
BEFORE + AFTER
FREQ
CPUE
# FREQ
CPUE
# FREQ
CPUE
21.7% 1,852.90
647 19.0% 2,297.41 1,006 19.9% 4,150.31
6.2%
810.13
295
8.7% 2,371.76
398
7.9% 3,181.89
3.2%
154.01
91
2.7%
698.79
144
2.8%
852.80
0.2%
425.77
9
0.3%
2.90
12
0.2%
428.67
2.8%
49.17
95
2.8%
174.32
142
2.8%
223.49
1.0%
77.80
0
0.0%
0.00
17
0.3%
77.80
14.8%
16.18
417 12.3%
24.44
662 13.1%
40.62
5.9%
6.64
289
8.5%
30.58
387
7.7%
37.22
0.0%
0.00
31
0.9%
29.24
31
0.6%
29.24
4.0%
23.85
25
0.7%
1.77
91
1.8%
25.61
0.0%
0.00
161
4.7%
13.11
161
3.2%
13.11
3.5%
2.56
82
2.4%
10.34
140
2.8%
12.90
1.0%
3.09
69
2.0%
8.04
85
1.7%
11.13
1.7%
2.48
62
1.8%
5.64
90
1.8%
8.12
0.8%
0.89
15
0.4%
3.53
29
0.6%
4.42
1.2%
3.00
11
0.3%
1.29
30
0.6%
4.29
0.2%
0.06
22
0.6%
4.09
26
0.5%
4.15
1.4%
1.38
94
2.8%
2.47
117
2.3%
3.84
0.4%
0.56
14
0.4%
2.68
20
0.4%
3.24
0.1%
0.06
9
0.3%
3.05
10
0.2%
3.11
0.2%
2.43
3
0.1%
0.14
7
0.1%
2.57
0.3%
0.76
3
0.1%
0.85
8
0.2%
1.61
0.2%
0.06
29
0.9%
1.01
33
0.7%
1.07
0.1%
0.03
9
0.3%
0.82
11
0.2%
0.84
0.1%
0.09
5
0.1%
0.35
6
0.1%
0.45
0.4%
0.05
25
0.7%
0.37
31
0.6%
0.42
0.1%
0.41
0
0.0%
0.00
2
0.0%
0.41
0.1%
0.00
4
0.1%
0.37
5
0.1%
0.37
0.2%
0.08
9
0.3%
0.20
12
0.2%
0.28
0.1%
0.02
4
0.1%
0.17
5
0.1%
0.19
0.1%
0.01
10
0.3%
0.10
11
0.2%
0.12
0.0%
0.00
1
0.0%
0.01
1
0.0%
0.01
45.3% 3,434.45 1,554 45.7% 5,689.85 2,303 45.5% 9,124.30
3,404
5,056