Status of Stocks & Multispecies Assessment Program
2006 Aleutian Islands Cooperative Acoustic Survey Study (cont.)
Between 14 March and 4 April 2006 six successful surveys were completed resulting
in relatively precise estimates of biomass for the survey area over time. Survey
2, conducted 14-15 March, provided a biomass estimate for pollock of 8,910
t. The biomass estimate for subsequent surveys were lower (although not
statistically significantly lower for Survey 4) and dropped significantly after
Survey 4 to a low of 2,845 t for the final survey (Table 2, Fig.
4, Fig. 5,
and Fig. 6)
In total, 965 t of fish were harvested during this study, the majority of which
(97% or 935 t) were harvested from the smaller area covered in Survey 6 and 7.
Most (77%) of the harvest (745 t) occurred after Survey 4 (Day 9). The pollock
biomass apparently declined by 68% in the large survey area during the 3 weeks
of the study. In the smaller “fished” area, the decline was estimated
at 90%. The “unfished” region showed no significant difference in
biomass estimates between Surveys 2 and 8.
Further analyses are needed to evaluate the cause the decline in the fished area.
A conservative estimate on the change in biomass over the study period is about
4,000 t—much greater than the amount of pollock caught. A trend in the
maturity data shows that the pollock began to show signs of active spawning only
at the end of the study period. This could indicate that fish were moving out
of the area to spawn. This may account for some of the observed declines.
Table 2. Abundance estimation for 2006 AICASS surveys.
Survey
Area (n.mi.2)
Deadzone (Y/N)
Biomass (t)
Relative Precision (Ei)
High Biom. (t)
Low Biom. (t)
Density (t / n.mi.2)
2
180
N
8233.8
8.67%
9632.5
6835.1
45.7
2
180
Y
8809.9
8.04%
10198.4
7421.4
48.9
2
72
N
6484.5
12.29%
8046.1
4922.9
90.1
2
72
Y
6706.6
14.32%
8589.2
4824.0
93.1
4
180
N
6600.4
7.96%
7630.1
5570.7
36.7
4
180
Y
7980.2
7.87%
9210.6
6749.8
44.3
4
72
N
5246.4
12.31%
6512.6
3980.2
72.9
4
72
Y
6149.8
11.89%
7582.5
4717.1
85.4
5
9
N
890.8
5.29%
983.2
798.4
99.0
5
9
Y
1036.6
4.75%
1133.1
940.1
115.2
6
72
N
3015.0
6.64%
3407.4
2622.6
41.9
6
72
Y
3458.5
6.44%
3894.9
3022.1
48.0
7
72
N
1159.0
6.83%
1314.2
1003.8
16.1
7
72
Y
2179.7
5.05%
2395.4
1964.0
30.3
8
180
N
2313.6
14.51%
2971.6
1655.6
12.9
8
180
Y
2845.2
14.24%
3639.0
2051.4
15.8
8
72
N
559.2
14.32%
716.1
402.3
7.8
8
72
Y
677.0
12.96%
848.9
505.1
9.4
In short, the 2006 AICASS was successful. In addition to achieving its scientific
objectives, this project fostered an excellent working relationship between NMFS,
the Aleut Enterprise Corporation, and the fishing industry. Local participation
and stakeholder involvement enhances NMFS’ ability to provide responsible stewardship
of this important marine resource. Future work should consider the expansion
of this technique to survey more areas within the Aleutian Islands to determine
the health and behavioral dynamics of this stock within Steller sea lion critical
habitat.
An AFSC Processed Report on the results of this study is due out this year. For further information please contact Steve Barbeaux at
Steve.barbeaux@noaa.gov.
