Research Document - 2004/013
Trends in Abundance for Northern British Columbia chum salmon
By Spilsted, B.P.
Abstract
This research paper documents chum salmon escapement trends and provides 2003 escapement forecasts of northern coastal British Columbia (Statistical Areas 1 to 6).
Long-term escapement trends
The Queen Charlotte Islands (Q.C.I.) index stream aggregate shows generally stable escapement for the past 30 years. Area 1 escapements are highly variable, with no apparent trend. Area 2 West streams show a stable pattern of chum escapement, similar to the Q.C.I. aggregate. The 2 East index stream aggregate shows periods of both increasing and decreasing abundance. The overall trend is not clear. It is recommended that the current conservative management approach of terminal Q.C.I. net fisheries directed on identified surplus escapement should continue.
North Coast chum streams in Areas 3, 5 and 6 show a long-term decline over the years 1950 to 2002. Area 4 escapements are highly variable, with no apparent trend. Chum stocks in Areas 3 to 6 need to be rebuilt.
2003 Escapement forecast
A summary of chum salmon escapement forecasts for index stream aggregate by Statistical Area and their characterization relative to a long-term mean and Department of Fisheries and Oceans Fisheries Management staff escapement goals is presented in the following Table:
| Stat. Area | Stock | Escapement Goal | Mean Esc. (1950-2002) | 2003 Forecast1 | 50% CI | Characterization of Status |
|---|---|---|---|---|---|---|
| 1 | index | 6.1x104 | 4.3x104 | 1.0x104 | 5.1x103 - 2.1x104 | Below Esc. Goal and Mean Esc., variable without trend |
| 2E | index | 2.2x105 | 1.3x105 | 6.5x104 | 4.2x104 - 1.0x105 | Below Esc. Goal and Mean Esc., variable with slight downward trend |
| 2W | index | 1.4x105 | 9.0x104 | 6.8x104 | 4.2x104 - 1.1x105 | Below Esc. Goal and Mean Esc., variable without trend |
| 3 | index | 7.2x104 | 3.8x104 | 3.3x104 | 2.2x104 - 4.8x104 | Depressed, long term decline, anticipated 2003 returns below Esc. Goal and Mean Esc. |
| 4 | index | 3.7x104 | 1.4x104 | 4.2x103 | 2.3x103 - 7.7x103 | Highly variable, no observable trend, 2003 returns well below Esc. Goal |
| 5 | index | 2.2x104 | 1.4x104 | 1.9x103 | 9.5x102 - 4.0x103 | Depressed, long term decline, anticipated 2003 returns well below Esc. Goal and Mean Esc. |
| 6 | index | 2.9x105 | 1.3x105 | 1.1x105 | 6.5x104 - 1.7x105 | Depressed, long term decline, anticipated 2003 returns well below Esc. Goal and Mean Esc. |
12003 forecast using 4YRA model for Areas 1, 2E, 4 and 5 and nYRA for Areas 2W, 3 and 6 as indicated by RMSE retrospective analysis (Table 9).
(Tables 10 to 12 provide forecast summaries using 4, 5 and n-YRA models for all stream aggregates and Tables 13 to 15 provide forecast summaries using 4, 5 and n-YRA models for index stream aggregates).
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