Forecasts and Planning Tools

Seasonal to Interannual Forecasts

Forecasting Oregon Coho Marine Survival

April 2004 archive copy

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Marine survival rates for Oregon coho salmon are influenced by several sequential environmental processes that affect coastal ocean food webs:

  1. Winter climate prior to smolt migration from rivers to the ocean;
  2. Date of occurrence of the “spring transition”, the period when alongshore winds (off the Pacific Northwest (PNW) coast) shift from being mostly northward to mostly southward;
  3. Total coastal upwelling during the spring;
  4. Ocean conditions during the maturing cohos’ only winter at sea.

By monitoring conditions during each cohort’s lifecycle, we can provide an experimental forecast of Oregon coho marine survival rates.

Recent Conditions

Environmental Index Observed Condition Relative Condition Implication for coho marine survival
Oregon Coastal Sea Surface Temperature, January-February-March 2003 10.8° C Above Average

Slightly
UNFAVORABLE

Spring Transition Date, 2003 Day 112 About 22 days later than average UNFAVORABLE
Neah Bay Coastal Sea Level (proxy for upwelling and alongshore transport), April-May-June 2003 -60.8 mm About average NEUTRAL
Oregon Coastal Sea Surface Temperature, January-February-March 2004 10.5° C A little above average Slightly
UNFAVORABLE

Current Forecast

Issue date: April 23, 2004 (updated from March 2004)
FORECAST RETURN RATE FOR ADULTS RETURNING FALL 2004: 1%

The original forecast return rate of 2% (issued March 2004) has been updated to reflect warmer January-March 2004 Oregon coastal sea surface temperatures. The preliminary forecast was based on January temperature only (10.3 degrees C). The observed Jan-March temperature mean was 10.5 degrees C.

Next Forecast Update
The early long-lead forecast for 2005 adult returns will be available in September 2004 (requires a forecast for January-February-March 2005 Oregon coastal sea surface temperatures).

Past Forecast Performance

Coho Returns (Year)
2002
2003
2004
2005
2006
Forecast
4-8%
5-7%
1%
   
Observed
~2%
not available at this time
     

See Figure 1 for the model’s performance at hindcasting for the period 1969-1998.

click image to enlarge

model’s performance at hindcasting for the period 1969-1998

Figure 1

Forecast Methodology

To better understand and predict Oregon coho marine survival, we developed a conceptual model (Figure 2) of key environmental processes that influence coastal ocean food webs and ultimately marine survival rates for Oregon coho salmon. The key processes are sequential:

  1. winter climate prior to smolt migration from rivers to the ocean;
  2. date of occurrence of the spring transition, when alongshore winds (off the PNW coast) shift from being mostly northward to mostly southward;
  3. total coastal upwelling during the spring;
  4. ocean conditions during the maturing cohos’ only winter at sea.

We then parameterized a general additive model (GAM) with Oregon Production Index (OPI) coho smolt-to-adult survival estimates from 1970-2001 and the environmental processes listed above. For the model training period (smolt year data from 1969-2000), the GAM explained 75% of the variance in observed OPI smolt-to-adult survival rates.

click image to enlarge

conceptual model of key environmental processes that influence coastal ocean food webs

Figure 2

Selected References

Logerwell, E. A., N. J. Mantua, P. Lawson, R. C. Francis, and V. Agostini. 2003. Tracking environmental processes in the coastal zone for understanding and predicting Oregon coho (Oncorhynchus kisutch) marine survival. Fisheries Oceanography 12(3):1-15.