Survey of Abalone Populations at Stryker Is and, of British Columbia,

Survey of Abalone Populations at Stryker Is and, of British Columbia,
Survey of Abalone Populations at Stryker Is and,
Tribal Group and Simonds Group, Central Coast
of British Columbia, ay, 1997
A. Campbell, and K. Cripps
Fisheries and Oceans Canada
Science Branch, Pacific Region
Pacific Biological Station
Nanaimo, British Columbia
V9R 5K6
1998
Canadian Manuscript Report of
Fisheries and Aquatic Sciences 2451
Fisheries and Oceans
Canada
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Canadian Manuscript Report of
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1998
SURVEY OF ABALONE POPULATIONS AT STRYKER ISLAND, TRIBAL GROUP
AND SIMONDS GROUP, CENTRAL COAST OF BRITISH COLUMBIA, MAY, 1997
by
A. Campbell, and K. Crippsl
Fisheries and Oceans Canada
Science Branch, Pacific Region
Pacific Biological Station
Nanaimo, British Columbia
V9R5K6
1 Eco-Pacific Resource-Management and Heiltsuk Fisheries Program,
Waglisla, B.c. VOT lZ0
ii
© Minister of Public Works and Government Services Canada 1998
Cat. No. Fs 97-4/2451 E
ISSN 0706-6473
Correct citation for this publication:
Campbell, A., and K. Cripps. 1998. Survey of abalone populations at Stryker Island,
Tribal Group and Simonds Group, central coast of British Columbia, May, 1997.
Can. Manuscr. Rep. Fish. Aquat. Sci. 2451: iii + 21 p.
iii
ABSTRACT
Campbell, A., and K. Cripps. 1998. Survey of abalone populations at Stryker Island,
Tribal Group and Simonds Group, central coast of British Columbia, May, 1997.
Can. Manuscr. Rep. Fish. Aquat. Sci. 2451: 21 p.
Transect surveys were conducted to determine the density of the northern abalone,
Haliotis kamtschatkana, from intertidal to approximate 8m depths, in the Tribal and
Simonds, Stryker group of islands of the central coast of British Columbia during May,
1997. Most (>96 %) adult abalone (2: 70 mm shell length SL) were exposed or emergent
(visible on rocks). Mean abalone sizes were generally largest in the -1-3 m depth range
and smallest in > 7 m depths. Adult abalone were more abundant < 5 m depths, whereas
small juveniles «50 mm SL) were found at all depths, but less frequently in the intertidal.
Mean densities for all sizes of abalone were similar (0.47,0.47 and 0.53 per m2) between
areas. Abalone densities were highest in the 0 - 1 m depth range, with fewer abalone
found in the intertidal areas and to depths >4 m.
RESUME
Campbell, A., and K. Cripps. 1998. Survey of abalone populations at Stryker Island,
Tribal Group and Simonds Group, central coast ofBritish Columbia, May, 1997.
Can. Manuscr. Rep. Fish. Aquat. Sci. 2451: 21 p.
Nous avons effectue en mai 1997 des releves sur transects pour determiner la
densite de l' ormeau nordique (Haliotis kamtschatkana), de la zone intertidale a une
profondeur d'environ 8 m, dans les lIes Tribal et Simonds, du groupe Stryker, dans la zone
centrale de la cote de Colombie-Britannique. La plupart (> 96 %) des ormeaux adultes
(~ 70 mm, LS de la coquille) etaient exondes ou emergents (visibles sur les rochers). La
taille moyenne des ormeaux etait generalement au maximum dans zone de profondeur
de 1-3 m et au minimum a des profondeufs de plus de 7 m. Les adultes etaient plus
abondants des profondeurs de moins de 5 m, tandis que les petits juveniles « 50 mm
LS) se retrouvaient a toutes les profondeurs, mais moins frequemment dans la zone
intertidale. Les densites moyennes etaient semblables pour toutes les tailles (0,47, 0,47 et
0,53 au m2) d'une zone a l'autre. Les densites des ormeaux etaient au plus haut dans la
plage de profondeur de 0-1 m, et les ormeaux etaient moins nombreux dans les zones
intertidales et a des profondeurs de plus de 4 m.
a
INTRODUCTION
The 'northern' or 'pinto' abalone, Haliotis kamtschatkana, generally occurs in
patchy distribution on exposed and semi-exposed coasts from Sitka Island, Alaska to Baja
California, including British Columbia (B.C.) (Sloan and Breen 1988). Northern abalone
were harvested by first nations and in commercial, and recreational fisheries in B.c. until
1990. Previous surveys at index sites in southeastern Queen Charlotte Islands and the
north central coast of B.C. indicated that the abundance of northern abalone had declined
more than 75% between the period of 1978-84 and remained low until 1994 (Winther et
ai. 1995; Thomas and Campbell 1996). Faced with the possibility of abalone population
collapse the northern abalone fishery has remained closed since 1990 due to conservation
concerns. The standard broad-scale survey design has remained essentially the same since
1978 (Breen and Adkins 1979) and consisted of counting and measuring abalone in 16
alternate 1 m2 quadrats per index site. Apart from a few samples made by Breen and
Adkins (1982) of abalone densities at Spider Island, Triquet Island and the Goose Group
during 1980, little was known of the status of abalone stocks in the Heiltsuk First Nations
traditional fishing area. Consequently, the traditional broad-scale survey of the Central
coast of B.c. (Thomas and Campbell 1996) was extended to include sample sites in the
Stryker, Simonds and Breadner group of islands (Campbell et ai. 1998). The objectives of
the present paper were to estimate the density of abalone using a random transect method
(Cripps and Campbell 1998) and to determine whether there was a relation between depth
and abalone size and density at the Tribal, Simonds and Stryker islands (Fig. 1).
METHODS
Transects were randomly placed on a nautical chart by positioning a metric ruler,
marked in mm, along the length of shoreline to be surveyed. A random numbers table was
used to select the position along the ruler where survey transects were to be placed. The
survey method was the same as that described by Cripps and Campbell (1998). The
primary sampling unit was a "transect", made up of a cluster or variable number of
secondary units. Each transect was one meter wide and variable in length depending on
the slope of the substrate within the depth range of 0 to 8m. The secondary sampling unit
consisted of a 1 m 2 quadrat that was placed on the right side of the transect line. Lead
line was deployed perpendicular to the iso1epths to a depth of approximately 10 meters
below chart datum. Transect origin was determined by indescriminantly throwing a lead
cannon ball into the intertidal zone. Divers, equipped with a 1m x 1m quadrat, flipped the
quadrat parallel to the transect line, from deep to shallow, and the number of "emergent"
or "exposed" (visible on rocks) abalone, shell length (SL in mm) of each abalone, depth,
substrate type, and dominant algal cover was recorded for each quadrat. All kelp, sea
urchins and starfish were removed from the quadrat to ensure abalone were easily
detectable, however, boulders were not rolled to examine for cryptic abalone. Caution
was exercised to ensure that abalone in upcoming quadrats were not disturbed. Sampling
2
only exposed abalone is an efficient sampling strategy, since the majority of mature
abalone (e.g., 2.70 mm SL) of interest to the survey are exposed (Campbell 1996).
All depth recordings were converted to depth at datum. The surveys were
conducted from the intertidal zone to about 8 m below chart datum. Surveying deeper
would have greatly reduce the number of transects that could be safely completed in a day.
To determine the detectability of exposed animals and the cryptic proportion of the
population, a few transects in each area were randomly chosen and subjected to more
intensive sampling protocol. The number of transects intensively surveyed at the Tribal
group was 4, Simonds group was 6, and Stryker Island was 3. The intensive survey
protocol involved examining each quadrat three times before moving onto subsequent
quadrats. Depth, substrate, dominant algal cover, number of exposed (emergent) abalone
on first examination, number of emergent abalone on second examination, and number of
cryptic abalone were recorded for each quadrat. The first examination involved
identifying and harvesting all the exposed animals. Sampled abalone were placed in a
marked collection bag. The quadrat was then more closely examined to see if any exposed
abalone were missed during the first pass. If an abalone was missed on the first pass the
animal was removed and placed in a separate labeled collection bag. On the third
examination, the cryptic component of the population was sampled by removing and
inspecting all of the moveable material within the quadrat. The cryptic abalone were also
removed and placed in a labeled collection bag. The shell length (mm) was recorded for
each abalone in each collection bag. Once the abalone were measured they were returned
to the area from where they were sampled.
The mean density, d (number / m2), was calculated as
(1)
The standard error of the mean density, se (d), was calculated as
seed)
= .Jl- n / N
n(n -1)a 2
where for each i transect, ci = the number of abalone observed in a transect, ai = the area
of transect surveyed in square metres, a =the mean transect area for all transects, n is the
number of transects sampled, and N is the total population of possible transects.
Adjusting densities for detectability was calculated by substituting Ci with ci / e, where e =
mean proportion of total population estimated to be detectable (exposed abalone /
(exposed + cryptic abalone». This method accounted for the variable length of transects.
Mean and standard error of densities by depth range and abalone size class was also
th
(2)
3
calculated by subsampling each transect. The depth ranges were (1) <0 m, (2) 0 - 1.5 m,
(3) 1.51 - 3.0 m, (4).3.01 - 4.50 m, (5) 4.51 - 6.00 m, (6) 6.01 - 7.50 m, (7) >7.50 m. The
size classes were "mature":::: 70 m SL [Le., about 100 % of abalone would be mature
(Campbell et al. 1992)], "prerecruit" 92-99 mm SL, "legal" :::: 100 mm SL, "new recruit"
100-106 mm SL and "total" which included all size classes. Although some of the size
categories, overlap they were included in the analyses so that the results could be
compared with those from previous surveys of abalone from other areas. The "immature"
<70 mm SL size class was not included in the density estimates (except as part of the
"total") because of the difficulty of finding small abalone.
RESULTS
SURVEY LOGISTICS SUMMARY
The number of transects surveyed off the Tribal Group was 29, the Simonds
Group was 32, and Stryker Island was 20 (Table 1,2). The mean length of transect was
12.0 m for the Tribal Group, 13.3 m for Simonds Group, and 12.7 m for the Stryker
Group.
POPULATION SIZE STRUCTURE
Juvenile exposed abalone « 50 mm SL) made up 22.5 %, 20.3 % and 23.3 % of
the population for the Tribal, Simonds, and Stryker group, respectively. The length
frequency distribution of exposed abalone indicated that the majority of the animals
sampled at both locations were less than 100 mm SL, with most abalone between 70 and
100 mm SL (Fig. 2, Table 3). Abalone:::: 70 mm SL were 43.2 %, 55.4 and 55.1 % of the
population for the Tribal, Simonds, and Stryker group, respectively. The percentage of
legal abalone (:::: 100 mm SL) was greater for the Simonds (18 %) than for those for
Stryker (5 %) and Tribal group (2 %).
Detectability expressed as a percent of exposed compared to total (exposed +
cryptic) abalone was higher for sizes:::: 70 mm SL than smaller abalone (Table 4, Fig. 3).
Most cryptic animals were < 70 mm SL. These results were similar to those reported for
other surveys (Campbell 1996; Cripps and Campbell 1998). These detectability factors
were used to estimate the combined cryptic and exposed abalone densities (Table 5).
Size frequencies and mean SL of exposed abalone generally decreased as depth
increased (Fig. 4, 5). Adult abalone were more abundant < 5 m depths, whereas small
juveniles «50 mm SL) were found at all depths, but less frequently in the intertidal (Fig.
4A, 4 B, 4C).
4
DENSITY ESTIMATES
Mean densities per transect ranged from 0 to 2.72 total exposed abalone per m2
(Fig. 6). Total mean densities of exposed, and adjusted for detectability, were similar for
each area (Table 5). Abalone densities were generally highest in the 1-3 m depth range,
although abalone were found at all depths surveyed (Fig. 7).
DISCUSSION
This study showed that there were differences in mean size and density of abalone
with increases in mean depth. Abalone were most abundant between 1 to 3 m depth, and
both density and mean abalone size declined with increasing depth in all three study areas.
Reduced density and size with increasing depth has been reported previously for H.
kamtschatkana (Sloan and Breen 1988; Cripps and Campbell 1998). All abalone were
found on firm substrates in this survey, although northen abalone are reported to be
capable of moving across sand or gravel (Sloan and Breen 1988). The decrease in mean
length with depth was probably due to adult abalone preferentially inhabiting shallow
water habitats for spawning (Breen and Adkins 1980) with juveniles found throughout the
1 - 7 m depths in this study. Breen and Adkins (1979, 1982) found juvenile northern
abalone were generally distributed deeper (5 - 15 m) than adults (Sloan and Breen 1988).
In general, the estimated mean total densities of abalone (adjusted for detectability)
found in this study appear to be similar to the densities found in previous surveys of
abalone in the central coast. Using the same transect method, Cripps and Campbell (1998)
estimated similar abalone densities in east Higgins Pass compared to those found in the
present study. Thomas and Campbell (1996) reported slightly higher densities from a
survey of abalone at 25 sites further north along the central coast ofRC. conducted
during 1993 (in this survey, the mean density of the total was 0.53, legals was 0.09). The
differences in mean density were probably a result of differences between the depth ranges
sampled by the index site 16-quadrat method (1 - 4 m) (Thomas and Campbell 1996;
Campbell et at. 1998) and the present transect survey method (intertidal to 8 m). After
standardizing the data to similar depth ranges, Campbell et al. (1998) found abalone
densities, estimated by the two survey methods at Simonds and Stryker Islands, during
May, 1997, to be similar. The results of the present survey and those of Campbell et al
(1998) indicated that northern abalone densities in southern areas of the central coast of
RC. were at density levels when the fishery was closed in 1990, and were well below
those reported by Breen and Adkins (1982) in a few samples during 1980.
Studies suggest that abalone growth and recruitment can differ dramatically from
one small area to another depending on local conditions, such as habitat type, food
availability, substrate type, and exposure to wave action (Sloan and Breen 1988). Future
surveys and studies of abalone in these areas should involve estimates of growth, mortality
and recruitment rates so that the productivity and surplus abalone production for possible
5
exploitation can be determined. Due to uncertainties about abalone productivity and
ability of abalone populations to recover from previous exploitation there still remains
conservation concerns for H. kamtschatkana along the central coast ofRC.
ACKNOWLEDGMENTS
We thank 1. Bolton, S. Humchitt and P. Newman for helping with the dive survey,
the Heiltsuk Band Council and the Aboriginal Fisheries Strategy for funds and providing
logistic support for the abalone surveys, L. Barton for chart/figure preparation and J.
Perry for assisting with data analyses.
6
REFERENCES CITED
Breen, P. A, and B. E. Adkins. 1979. A survey of abalone populations on the east coast
of the Queen Charlotte Islands, August 1978. Fish. Mar. Servo MS Rep. 1490:
125 p.
Breen, P. A, and B. E. Adkins. 1980. Spawning in a British Columbia population of
northern abalone, Haliotis kamtschatkana. Veliger 23: 177 - 179.
Breen, P. A, and B. E. Adkins. 1982. Observations of abalone populations on the north
coast of British Columbia, July 1980. Can. Manuscr Rep. Fish. Aquat. Sci. 1633:
55 p.
Campbell, A 1996. An evaluation of abalone surveys off southeast Queen Charlotte
Island. Can. Tech. Rep. Fish. Aquat. Sci. 2089: 111 - 131.
Campbell, A, 1. Manley, and W. Carolsfeld. 1992. Size at maturity and fecundity of the
abalone, Haliotis kamtschatkana, in northern British Columbia. Can Manuscr.
Rep. Fish. Aquat. Sci. 2169: 47-65.
Campbell, A, 1. Winther, B. Adkins, D. Brouwer, and D. Miller. 1998. Survey of
northern abalone, Haliotis kamtschatkana, in the central coast of British Columbia,
May 1997. Canadian Stock Assessment Secretariat Research Document 98/89. 29
p.
Cripps, K., and A Campbell. 1998. Survey of abalone populations at Dallain Point and
Higgins Pass, central coast of British Columbia, 1995 - 96. Can. Manuscr. Rep.
Fish. Aquat. Sci. 2445: 35 p.
Sloan, N. A, and P. A Breen. 1988. Northern abalone, Haliotis kamtschatkana, in
British Columbia: fisheries and synopsis of life history information. Can Special
Pub. Fish. Aquat. Sci. 103: 46 p.
Thomas, G., and A Campbell. 1996. Abalone resurvey in Aristazabal Island, the Estevan
group
Banks
Sci. 2089:
109.
Winther, 1., A Campbell, G. A Thomas, RE. Adkins, and RG. Clapp. 1995. Abalone
resurvey in the southeast Queen Charlotte Islands, 1994. Can Manuscr. Rep. Fish.
Aquat. Sci. 2273: 46 p.
7
Table 1. Dive swvey SllllllllaIY for abalone transects swveyed in the Tribal, Simonds and Stryker
groups, May 1997.
Time
Bottom
Depth(m)
Number of Total #
Density
Transect
Min
Quadrats of Abalone (No.lm2)
Finish
Date
Max
Time
Start
Tribal Group
101
7.86
May 21
14:35
14:50
0:15
0.12
7
0
0.000
May 21
15:45
-2.74
8.38
17
102
15:00
0:45
18
1.059
103
May 22
-0.76
7.68
9:14
9:34
0:20
9
9
1.000
-2.07
7.86
9
May 21
104
11:20
11:33
0:13
2
0.222
105
15
12
May 22
11:40
11:57
0:17
-2.77
5.70
0.800
May 22
6.98
10
106
9:50
10:03
0:13
-1.13
2
0.200
107
21
17
May 22
14:50
15:32
0:42
-1.28
6.00
0.810
108
May 22
11
0
11:40
11:57
0:17
-2.77
6.31
0.000
109
May 22
11:10
11:30
0:20
-2.41
7.04
10
13
1.300
110
May 22
13:42
14:37
0:55
-2.62
7.19
20
19
0.950
-1.46
7.35
111
May 21
10:29
10:48
0:19
15
2
0.133
6.89
112
May 21
11:00
11:15
0:15
-1.52
11
0
0.000
May 21
-1.46
7.25
113
11
0
11:20
11:33
0:13
0.000
114
13:15
13:30
0:15
-2.26
7.22
8
16
May 21
2.000
May 21
115
14:00
14:12
0:12
-2.50
7.62
8
8
1.000
116
May 21
-2.65
6.34
11:43
11:58
0:15
8
6
0.750
11
117
May 21
10:01
10:16
0:15
-1.92
8.66
3
0.273
118
May 22
16:00
-1.80
7.77
15:47
0:13
9
1
0.111
119
May 22
-1.55
6.83
10
16:12
16:25
0:13
2
0.200
121
15:16
15:28
0:12
-2.29
5.70
12
May 23
1
0.083
122
May 23
14:43
15:05
0:22
-2.62
5.61
11
4
0.364
123
May 23
14:15
6.31
4
14:45
0:30
-2.01
12
0.333
124
May 23
12:45
13:15
0:30
-1.74
6.25
26
1
0.038
125
7.89
May 23
12:17
12:34
0:17
-1.83
10
4
0.400
126
May 23
11:41
12:06
0:25
-1.71
7.22
14
2
0.143
127
11:00
11:25
0:25
-1.68
8.44
14
May 23
7
0.500
128
10:23
10:51
0:28
-1.49
8.35
17
May 23
19
1.118
129
16:06
16:15
0:09
-1.07
5.70
6
May 23
0
0.000
130
May 23
16:24
16:34
0:10
-2.13
6.19
6
0
0.000
Simonds Group
201
May 25
16
0
14:10
14:30
0:20
-2.16
7.53
0.000
202
May 25
0040
8041
20
14
9:16
9:44
0:28
0.700
203
May 25
14:46
15:29
0:43
-3.63
7.10
39
1
0.282
204
21
22
May 25
10:29
10:47
0:18
1.86
10.18
1.048
205
May 26
13
3
11:04
11:28
0:24
0.24
9.17
0.231
206
May 26
9.20
11
4
10:40
10:57
0:17
-0.27
0.364
207
May 26
12:45
13:11
0:26
-1.10
8.99
14
12
1.167
208
11:19
11:32
0:13
-0.67
8.32
10
4
May 25
00400
209
10:50
11:11
0:21
-0046
8.26
8
10
May 25
1.250
210
May 25
10:47
0:18
-0.27
8.35
11
9
0.818
10:29
211
May 25
10:21
0:30
0046
9.02
16
17
9:51
1.063
212
0:28
-0.21
9.94
15
May 25
9:16
9:44
10
0.667
213
-0.34
7.96
7
May 25
9:00
9:09
0:09
0
0.000
214
12:14
0:34
-1.19
7.77
May 25
17
26
11:40
1.529
215
May 26
9:52
10:05
0:13
-0.12
9.11
8
1
0.125
8
Table 1 (cont'd).
Time
Transect
Date
Finish
Start
Simonds Group (cont'd)
216
May 26
9:28
9:47
217
May 26
9:18
8:47
218
May 24
15:18
15:38
219
May 24
14:58
15:10
220
May 24
14:31
14:46
221
May 24
14:07
14:19
222
May 24
13:40
13:57
223
May 24
13:07
13:32
224
May 24
11:07
11:38
225
May 24
10:12
10:55
226
May 24
9:56
10:07
227
May 24
9:41
9:50
228
May 24
9:26
9:35
229
May 24
9:06
9:20
230
May 26
12:45
13:11
231
May 26
13:20
13:32
232
May 26
13:39
13:59
Stryker Island
301
May 29
11:40
11:55
302
May 29
11:13
11:31
303
May 29
10:37
10:47
304
May 29
10:55
11:05
305
May 29
9:48
10:30
306
May 29
9:17
9:39
311
May 28
8:38
9:09
312
May 28
9:19
9:36
314
May 28
10:24
10:47
316
May 28
11:33
11:58
317
May 28
11:21
11:01
318
May 28
12:08
12:20
319
May 28
12:26
12:36
320
12:57
May 28
12:46
321
May 28
13:04
13:14
322
May 28
13:20
13:40
323
May 28
14:00
13:47
324
May 28
14:32
14:10
325
May 28
14:43
15:02
326
May 28
9:44
10:10
Bottom
Time
Depth(m)
Min
Max
Number of Total #
Density
Quadrats of Abalone (No./m2 )
0:19
0:31
0:20
0:12
0:15
0:12
0:17
0:25
0:31
0:43
0:11
0:09
0:09
0:14
0:26
0:12
0:20
-0.61
-0.73
-2.90
-2.87
-2.77
-2.26
-2.32
-2.62
-1.25
-0.98
1.62
1.10
0.55
0.24
-1.40
-1.98
-2.07
9.91
8.75
6.86
7.22
6.80
7.01
7.62
7.77
8.93
8.87
8.69
8.14
8.17
8.20
8.99
7.92
8.90
10
14
14
8
12
9
11
17
20
21
9
6
5
8
18
10
11
1
2
1
4
7
0
6
25
12
4
1
0
0
0
11
1
9
0.100
0.143
0.071
0.500
0.583
0.000
0.545
1.471
0.600
0.190
0.111
0.000
0.000
0.000
0.611
0.100
0.818
0:15
0:18
0:10
0:10
0:42
0:22
0:31
0:17
0:23
0:25
0:20
0:12
0:10
0:11
0:10
0:20
0:13
0:22
0:19
0:26
-1.10
-1.34
-1.40
-0.30
-2.23
-3.14
-1.71
-1.52
-0.79
-1.16
-1.07
-0.70
0.55
-1.04
-1.10
-1.22
-0.76
-1.07
-1.10
-0.61
7.56
7.96
8.44
7.10
7.96
8.35
8.11
8.44
8.29
8.72
7.01
8.14
8.17
9.05
9.33
7.41
7.86
8.90
6.43
8.84
8
21
6
14
14
14
16
9
11
13
29
7
7
10
8
16
12
12
18
9
4
3
2
0
16
3
10
0
10
16
4
7
1
1
0
20
2
33
2
2
0.500
0.143
0.333
0.000
1.143
0.214
0.625
0.000
0.909
1.231
0.138
1.000
0.143
0.100
0.000
1.250
0.167
2.750
0.111
0.222
9
Table 2. SUlIllIUlIY statistics of transect SOlVey of exposed abalone from the Tribal,
Simonds and Stryker groups, May, 1997. Values in brackets are standard errors.
Details per transect
Dates
Number of tansects
Mean Depth (m)
Mean quadrats or length (m)
Mean minutes
Mean minutes/quadrat
Tribal Group
21-24 May
29
2.41 (0.09)
12.0 (0.9)
20.5 (2.0)
1.59 (0.14)
Simonds Group
24-26 May
32
3.75 (0.09)
13.3 (1.2)
20.9 (1.6)
1.60 (0.07)
Stryker Group
28-29 May
20
3.21 (0.12)
12.7 (1.2)
18.8 (1.8)
1.69 (0.08)
10
Table 3. Mean shell length (mm SL) of exposed abalone of different size groups for
all transect surveys of the Tribal, Simonds and Stryker Island groups, May, 1997.
N = number of abalone. Values in brackets are standard errors.
(mm SL)
Size group
Tribal Group
Mature
~70
Pre Recruit
92 - 99
New Recruit 100 -106
Legal
~ 100
all sizes
Total
Simonds Group
Mature
~70
Pre Recruit
92 - 99
New Recruit 100 - 106
Legal
~ 100
Total
all sizes
Stryker Group
Mature
~70
Pre Recruit
92 - 99
New Recruit 100 -106
Legal
~ 100
Total
all sizes
N
%oftotal
Shell Length
73
13
2
4
169
43.20
7.69
1.18
2.37
100.00
83.6 (1.1)
94.8 (0.5)
102.5 (2.5)
106.3 (2.7)
64.4 (1.6)
123
24
17
40
222
55.41
10.81
7.66
18.02
100.00
92.5 (1.2)
95.5 (0.4)
102.5 (0.5)
108.3 (1.0)
71.3 (2.0)
66
8
6
7
129
51.16
6.20
4.65
5.43
100.00
83.4 (1.3)
95.8 (0.9)
103.5 (0.9)
105.0 (1.7)
66.6 (2.1)
11
Table 4. Detectability as a percent of total abalone by size category for cryptic and exposed abalone
from intensive samples at all depths from the Tribal (4 transects), Simonds (6 transects) and Stryker
(3 transects) groups of islands, May, 1997.
Tribal Group
Number % of Total
Details
Immature Abalone < 70 mm SL
Cryptic
6
20.00
Exposed
24
80.00
Total
30
Mature Abalone 2: 70 mm SL
Cryptic
0
0.00
Exposed
28
100.00
Total
28
All sizes of Abalone
Cryptic
6
10.34
Exposed
52
89.66
Total
58
Simonds Group
Number % of Total
Stryker Group
Number % of Total
Total of Three areas
Number % of Total
1
8
9
11.11
88.89
10
20
30
33.33
66.67
17
52
69
24.64
75.36
1
14
15
6.67
93.33
1
12
13
7.69
92.31
2
54
56
3.57
96.43
2
22
24
8.33
91.67
11
32
43
25.58
74.42
19
106
125
15.20
84.80
12
Table 5. Mean density (number/m2) of exposed abalone of different size groups for all depths
from Tribal, Simonds and Stryker group of islands, May, 1997. Means unadjusted and adjusted for
detectability. Values in brackets are standard errors.
Size group
mmSL
Unadjusted
Mature
~70
Pre Recruit
92 - 99
New Recruit
100 - 106
Legal
~ 100
Total
all sizes
Adjusted for detectability
Mature
~70
Pre Recruit
92 - 99
100 -106
New Recruit
Legal
~ 100
Total
all sizes
Number of transects
Tribal
Simonds
Stryker
0.188 (0.053)
0.039 (0.014)
0.008 (0.005)
0.013 (0.008)
0.468 (0.094)
0.231 (0.068)
0.049 (0.017)
0.028 (0.014)
0.064 (0.032)
0.468 (0.081)
0.255 (0.099)
0.030 (0.014)
0.018 (0.009)
0.022 (0.012)
0.526 (0.149)
0.188 (0.053)
0.039 (0.014)
0.008 (0.005)
0.013 (0.008)
0.522 (0.105)
29
0.248 (0.072)
0.052 (0.018)
0.030 (0.015)
0.069 (0.034)
0.510 (0.088)
32
0.276 (0.108)
0.032 (0.015)
0.020 (0.010)
0.024 (0.013)
0.707 (0.200)
20
13
128:20
128:30
o
o
Campbell
Island
01
lO
I\)
o
..,
('\I
lO
o
01
..
.()
~
'
1
01
o
o
I\)
o
o
('\I
lO
lO
lO
a'
lO
Scale in Meters
:
o
t
2700 5400 8100 10800 13500
128:30
128:20
Fig. 1. General location of study areas (1) Tribal (in statistical area 7 -18), (2) Simonds
(in statistical area 7 -25)" and (3) Stryker group of islands (in statistical areas 7 -18, 7 19), in the central coast of British Columbia surveyed for abalone during May, 1997.
14
8
8
7
A
TRIBAL
6
...-
MEAN =64
N = 169
6
0.03
5
a
'8
;::l.
o·
4
:J
0.0216
...,
3
OJ
B
SIMONDS
MEAN = 71
N =222
0.03
"U
a
u
5
0
0.02
'E
6
(.)
4
:J
CD
...,
3
OJ
0.01 ~
0.01
50
..........---'0.0
100
150
50
100
'-11----10.0
150
SHELL LENGTH (MM)
SHELL LENGTH (MM)
12 .-------.----.-------,0.09
10
C
MEAN = 67
STRYKER N = 129
0.07
"U
0.05
g.
o
...c
6
0.08
a
0.06 u
8
6
:J
(.)
0.04 16
...,
4
0.03 ~
0.02
2
0.01
50
g.
u
Ql
...,
2
o
o
6
"U
c
(.)
7
0.04
....1------10.0
100
150
SHELL LENGTH (MM)
Fig. 2. Size frequencies of exposed abalone from the (A) Tribal, (B) Simonds, and (C)
Stryker group of islands surveyed May, 1997.
15
EXPOSED
CRYPTIC
0.5
3
A
MEAN = 22
N=6
2
C
:>
"
0.4
0.31.
0
..,:>
0.2 !!:
m
MEAN =69
N=52
3
."
a
0
0
B
C
5
0
2
0.07
0.06
."
0.05
~
0.04
..,~
0.03 !!:
m
0.02 ~
~
0.1
0.01
0
0
50
100
0.0
150
0
0
50
SHEll LENGTH (MM)
3
1.5
1.4
C
1.0
100
MEAN = 72
1.2
N=1
1.0
I
D
MEAN = 83
N =22
."
.g
0.8
:>
0
0
0.6
g
:>
~
50
100
o'
:>
0.06 ~
1
0 .04
2
50
100
0 .0
150
0.09
F
MEAN 60
N = 32
0.2 ."
..,ao
ao
c
,3
..,
:>
0.1
1
~
SHELL LENGTH (MM)
3
MEAN = 40
N = 11
m
0 .02
o
o
0.0
150
SHELL LENGTH (MM)
E
..,a
:>
0
0
0.2
0.0
0
0.10 ."
0.08 ~
C
m
0.4 ~
0.5
0.12
2
0
c
0.0
150
SHEll LENGTH (MM)
~
2
0.08
0.07 ."
0.06
c
0.05
:>
0
0
.g
0
g
:>
0.04 ~
0.03 ~
~
0.02
0.01
o
o
50
100
SHELL LENGTH (MM)
0 .0
150
0
0
50
100
0.0
150
SHELL LENGTH (MM)
Fig. 3. Size frequencies of cryptic and exposed abalone, respectively, (A) and (B) Tribal
Group, (C) and (D) Simonds Group, and (E) and (F) Stryker Group from intensive survey
samples May, 1997.
16
TRIBAL GROUP
4
4
1
0.06
3
0.05
3
"U
a
2
C
i5
0
2
::>
0
0.03 ~
0.02
c
i5
0
50
100
2
0.04
g
m
~
"0
0
50
100
"0
0.04 ;;,
0.5
0.0
150
~
0.0
0
50
100
1.5
3
0.5
0.2
6
5
.g
a
1.0
0
d.
c
0
~
"U
a
"0
2
"0
g
0.4
"U
a
0
::>
0.1 ~
0
~
m
0.04 ~
~
0.3
c
::>
50
100
SHELL LENGTH (mm)
0.0
150
0
0.2
50
100
SHELL LENGTH (mm)
0.0
150
0.0
0
"0
~
m
0.5
~
0.1
0
0
!
::>
0
0
0.02
0
0
0.0
150
SHELL LENGTH (mm)
0
0.06
..
0
0.01
"U
c
~
0.06
0
0.02
0.10
2
0.08 ~
1.0
c::>
SHELL LENGTH (mm)
0.08
i5
.
.,
0.10
0.02 ~
0.0
150
3
0
a
0.03 ;;,
0.12
4
4'
0
"8
"0
SHELL LENGTH (mm)
4
0.05
0.06
0.01
0
0
3
0.07
"0
0.04 ~
1.5
0.08
50
100
SHELL LENGTH (mm)
Fig. 4A. Size frequencies by depth category of exposed abalone from the Tribal Group,
surveyed May, 1997. Depth category (1) < 0 m, (2) 0 - 1.50 m, (3) 1.51 - 3.00 m, (4) 3.01
- 4.50 m, (5) 4.51 - 6.00 m, (6) 6.01 - 7.50 m.
0.0
150
17
SIMONDS GROUP
3
6
0.16
1
0.14
0.12
2
5
11
0.10 ~
C
8
0.06
0
::>
."
.'"
3
2
0.05
0.06
"U
0
4
0.06
C
83
0.06 ;;;
0.04
3
0.10
0
C
::>
."
U
::>
."
0
."
'"
0.02 ;;;
m
2
~
0.03
0
0.04 ~
11
0.04
2
~
~
~
~
0.02
0.01
0.02
a
a
50
100
a
a
0.0
150
4
3
0.05
11
0.04
g
::>
0.03 ~
"U
"U
0
C
::>
0.06
0
u
0.06
g
::>
~
m
0.04 ~
0.01
100
0.0
150
0.2
0.12
m
50
100
6
0
1.0
0.10.g
0.02 ~
a
a
50
SHELL LENGTH (MM)
1.5
2
."
0
C
52
a
a
0.0
150
0.14
5
0.06
u
100
3
0.07
4
50
SHELL LENGTH (MM)
SHELL LENGTH (MM)
."
0
<±
C
::>
0
0.1 ~
0
u
~
m
0.5
~
0.02
a
a
0.0
150
50
100
SHELL LENGTH (MM)
SHELL LENGTH (MM)
0.0
150
0.0
a
50
100
0.0
150
SHELL LENGTH (MM)
3
7
0.2
"U
0
"0
0
~
C
::>
0
U
0.1
"0
~
m
~
50
100
0.0
150
SHELL LENGTH (MM)
Fig. 4B. Size frequencies by depth category of exposed abalone from the Simonds
Group, surveyed May, 1997. Depth category (1) < 0 m, (2) 0 - 1.50 m, (3) 1.51 - 3.00 m,
(4) 3.01 - 4.50 m, (5) 4.51 - 6.00 m, (6) 6.01 -7.50 m, (7) >7.50 m.
18
STRYKER GROUP
6
3
1
0.14
5
<4
0.10
2
0.12
0.06 "
"
0.10 ~
2
c
0.08
il
()
..,a
<4
a
c
..,g
il
C
il
..,:>
0.04 ~
'"
3
()
{D
0.2
..,a"
0
go
0.06
0.06 ~
0.04
3
3
0
a0
2
:>
()
0.1
~
~
{D
!:
"
!:
0.02
0.02
a
a
50
100
0.0
150
50
SHEll LENGTH (MM)
100
1.5
1.5
4
0.07
0.06
1.0
..,"a
0.05 ~
:>
0
0
0.04
()
.6
'"
0.03 ;:;,
0.5
a
0.3
1.5
0.0
150
a
5
0.06
co
0.0
150
SHEll LENGTH (MM)
0.02
!:
6
0.2
1.0
.g"
0
a0
c
:J
..,
:J
0
()
~
0.1 ~
0.5
0.2
..,a"
1.0
0
a0
c
:J
..,
:>
0
()
0.1 ~
0.5
{D
!:
0.01
0.0
a
50
100
0.0
150
0.0
a
SHELL LENGTH (MM)
50
100
SHELL LENGTH (MM)
0.0
150
0.0
a
50
100
0.0
150
SHELL LENGTH (MM)
1.5
7
0.14
0.12
1.0
0.10
.g"
0
C
:J
0.08
go
..,
:J
0
()
0.06
0.5
~
{D
0.04 !:
0.02
0.0
a
50
100
0.0
150
SHELL LENGTH (MM)
Fig. 4C. Size frequencies by depth category of exposed abalone from the Stryker Group,
surveyed May, 1997. Depth category (1) < 0 m, (2) 0 - 1.50 m, (3) 1.51 - 3.00 ill, (4) 3.01
- 4.50 m, (5) 4.51 - 6.00 m, (6) 6.01 -7.50 m, (7) >7.50 m.
19
-80
~
~
-- 70
I
I-
<.9 60
z
W
....J
....J
....J
TRIBAL
50
/+
~ __ ~X
W 40
I
CJ)
STRYKER
z 30
«
w
~
20
10 L---L----L-----L-----l-----Il....-...l----L----l---L---1.----'
-1
0
1
2
3
4
5
6
7
8
9 10
MEAN DEPTH (M)
Fig. 5. Mean shell length of exposed abalone by mean depth in the Tribal, Simonds, and
Stryker groups of islands during May, 1997.
20
12
10
.....c
:J
0
()
A
10
MEAN = 0.47
N = 29
8
12
0.4
0.3 ~
"t:l
0
do
6
0.2
g
"t:l
~
4
OJ
III
8
B
MEAN = 0.47
N = 32
.....
c
:J
0
()
0
-0
a
"t:l
0
0.2
6
...,
(»
4
OJ
0.1 ~
2
0
1
2
0.0
3
0
0
MEAN ABALONE DENSITY PER TRANSECT
1
2
0.0
3
MEAN ABALONE DENSITY PER TRANSECT
7~-----,-----,----~
6
C
5
MEAN = 0.53
N =20
C 4
:J
o
() 3
0.3
-0
a
"t:l
0.2 ~
o
:J
"t:l
~
2
0.1
o
o
0.0
g.
:J
"t:l
0.1 ...,
2
0.3
OJ
~
1
2
3
MEAN ABALONE DENSITY PER TRANSECT
2
Fig. 6. Frequency distribution of mean densities (number per m ) of exposed abalone per
transect for all depths combined from the (A) Tribal, (B) Simonds, and (C) Stryker group
of islands surveyed during May, 1997.
21
W
0::
t:i
::2:
2.5 r--r-r-r-r-r-r-r--r--r--r--..---.
A
dCJ)
ffi
W
d
CJ)
ffi
1.5
<t.
28
1.5
w
Z
o 1.0
1.0
-l
c(
i::2:1i
i::2:1i
CD
c(
z 0.5 26
z 0.5
O.0 1.--L....JL....l--l.-..L-..L..-L--L.~S-..I.---'
-2 -1
0
1
2
3
4
5
6
7
8
27
0.0 L..-.'--'--'--'--'--'--I.--L......IL......IL......IL.......I
-2 -1
9 10
0
1.5....-r--r--r--r--r--r--r--r--r--r--..---.
0::
o
W
TRIBAL
MATURE
::2:
CJ)
W
0::
d
CJ)
<t.
28
1.0
0.0 L..-..1-.1-.1-=-.1-.1-.D=o.........1-.L-.L...-J
4
5
6
7
8
::2:
w
G
::2:
TRIBAL
LEGAL
~
w
0.2
CJ)
0
1
2
3
4
5
6
7
8
0.3
z
0.0
-2 -1
9
0
1
2
3
4
5
6
7
MEDIAN DEPTH (M)
0.0 LJL..1-L-L-L!LJ1=t::::f:1:::ILJ....-J
-2
1 2
8
~
9 10
3
4
5
6
7
8
9 10
0.3
I
STRYKER
LEGAL
~
d
0.2
CJ)
0.2
0::
W
0W
z
19
0
<t.
0.1
0.1
CD
c(
z
28
0.5
w
z
«
w
28
c(
::2:
W
0::
I-
H
SIMONDS
LEGAL
c(
c(
w
19
1.0
MEDIAN DEPTH (M)
CD
CD
9 10
STRYKER
MATURE
9 10
0
<t.
8
w
0.0 L-.l..:.-.1..-.1-.1-.1-.1-.1-J........LJ.....:::"---L.-J
0W
Z
0.1
7
Z
w
0
6
c(
0::
0::
W
0W
Z
5
c(
w
d
4
CD
-2 -1
0::
I-
3
::2:
d
MEDIAN DEPTH (M)
0.3
2
W
o
<t.
0.5
9 10
0::
l-
1
w 1.5 r-r-Y-;r-r-r-r-r-,.-,.-,.--r-->
F
ICJ)
Z
3
0
0::
W
0W
Z
26
w
2
-2 -1
0::
c(
1
0.0 ':.-..'':.-..''---'--'--'---L---L=-.L---L---L-..L.-J
MEDIAN DEPTH (M)
CD
0
::2:
9 10
E
MEDIAN DEPTH (M)
~
8
c(
-2 -1
<t.
7
SIMONDS
MATURE
0::
W
0W
Z
i1i
CJ)
6
1.5 r--r--r--r--r--r--r--r--r-r-r-,.......,
::2:
z
d
5
o
0.5
CD
w
4
W
1.0
c(
::2:
3
I-
0::
W
0W
Z
o
<t.
1 2
z 0.5
«
w
MEDIAN DEPTH (M)
MEDIAN DEPTH (M)
I-
1.5
0-
c(
c(
d
ffi
26
CD
c(
STRYKER
ALL
d
w
Z
o-l
1.0
CD
w
W
::2: 2.0
CJ)
0-
w
C
I-
SIMONDS
ALL
::2: 2.0
0-
oZ
w 2.5 r-r-rrr-r-r-r-r-r-r-r-or--.
0::
B
I-
TRIBAL
ALL
2.0
w 2.5r-r-r-r-r-r-r-r-r-r-r-,---,
0::
c(
w
0.0
-2 -1
~
0
1 2
3
4
5 6
7
MEDIAN DEPTH (M)
8
9 10
0.0
-2 -1
0
1
2
3
4
5
6
7
MEDIAN DEPTH (M)
Fig. 7. Mean densities of abalone (adjusted for detectability, to include exposed and
cryptic) by size group and depth from the Tribal, Simonds, and Stryker group of islands,
respectively for (A, B, C) all sizes, (0, E, F) mature sizes (2:. 70 mm SL), and (G, H, I)
legal sizes (2:. 100 mm SL) surveyed during May, 1997. Vertical lines are + 1 standard
error. Numbers represent number of transects.
8
9 10
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