Seasonal to Interannual Forecasts
Forecasting Oregon Coho Marine Survival
April 2007 archive copy
On This Page
- Elizabeth Logerwell (contact person), NOAA Fisheries/Alaska Fishery Science Center
- Nathan Mantua, University of Washington, Climate Impacts Group
- Peter Lawson, NOAA Fisheries/Newport Lab
- Robert Francis, University of Washington, Climate Impacts Group and School of Aquatic and Fishery Sciences
- Vera Agostini, University of Washington, Climate Impacts Group and School of Aquatic and Fishery Sciences
Marine survival rates for Oregon coho salmon are influenced by several sequential environmental processes that affect coastal ocean food webs:
- Winter climate prior to smolt migration from rivers to the ocean;
- 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;
- Total coastal upwelling during the spring;
- 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 and Forecasted Conditions
|Relative Condition||Implication for coho marine survival|
|Oregon Coastal Sea Surface Temperature, January-February-March 2006 (before ocean entry)||11.65°C||Well above average (highest since 1999)||
|Spring Transition Date, 2006||Day 112 (April 22)||About average||Neutral|
|Neah Bay Coastal Sea Level (proxy for upwelling and alongshore transport), April-May-June 2006||-30.64 mm||On the high side||Somewhat unfavorable|
|Oregon Coastal Sea Surface Temperature, January-February-March 2007 (after ocean entry)||
Issue date: April 30, 2007
FORECAST RETURN RATE FOR ADULTS RETURNING FALL 2007:
Forecasted Jan-March 2007 Sea Surface Temperature
Forecasted Return Rate for Fall 2007 (mean rate)
4.5% (+/- 0.9%)
Ocean conditions, as measured by our simple model, were moderately good for OPI coho smolts in 2006. The spring transition was near average and spring sea level was low (low sea level is indicative of good upwelling and strong north-south transport).
Although Jan-Mar SST in 2005 was above average and unfavorable, January through March SST in 2007 was quite cold and favorable.
Past Forecast Performance
|Year prior (Y0)
(before ocean entry)
|Oregon SST, Y0
|Spring Transition, Y0||Neah Bay Sea Level , Y0 (April-June)||Oregon SST, Y1
(Jan-Mar, after ocean entry)
|Predicted OPI survival for Y1||Observed OPI survival for Y1|
|2000||1999||9.53°C||Day 91||-142.73 mm||10.5°C||6%|
|2001||2000||10.5°C||Day 72||-70.03 mm||10°C||5%|
|2002||2001||10°C||Day 61||-122.43 mm||9.7°C||
|2003||2002||9.7°C||Day 80||-141.29 mm||10.8°C||7%||3.8%|
|2004||2003||10.8°C||Day 112||-60.82 mm||10.5°C||1%||2.6%|
|2005||2004||10.5°C||Day 110||-75.02 mm||10.74°C||0.5%||1.9%|
|2006||2005||10.74°C||Day 145||-16.09 mm||11.65°C||0.3%||2.0%|
|2007||2006||11.65°C||Day 112 (April 22)||-30.64 mm||9.21°C||
See Figure 1 for the model’s performance at hindcasting for the period 1969-1998.
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:
- winter climate prior to smolt migration from rivers to the ocean;
- date of occurrence of the spring transition, when alongshore winds (off the PNW coast) shift from being mostly northward to mostly southward;
- total coastal upwelling during the spring;
- 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.
For More Information
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.