Forecasting Pink Salmon Abundance in Southeast Alaska from Juvenile Salmon Abundance and Associated Environmental Parameters
The Southeast Coastal Monitoring project (SECM) is a component of the NOAA Auke Bay Laboratories salmon research program which has sampled juvenile salmon and associated biophysical parameters in northern Southeast Alaska (SEAK) since 1997 utilizing the NOAA Ship John N. Cobb and chartered trawl vessels. Sampling juveniles as they migrate to the Gulf of Alaska, after high-mortality periods of freshwater incubation and early marine residency, provides information on year-class strength that can be used with associated environmental data to forecast abundance of the fish when they return as adults. Data from these annual surveys have been used to develop models that predicted SEAK pink salmon harvests within 16% of actual harvests for 2004, 2005, 2007, 2008, and 2009. However, this forecast accuracy was not achieved in 2006, when pink salmon harvest was well below both the SECM forecast based on juvenile salmon abundance and the Alaska Department of Fish and Game (ADF&G) forecast based on previous pink salmon harvest time series. Despite this overestimate, the 2006 SECM forecast accurately identified a decline in average pink salmon harvest. The ADF&G is now incorporating the SECM juvenile data into their annual harvest time series forecast.
The Northern Fund (NF) has provided support to SECM to improve the forecast modeling and to increase the geographic scope of the data collected. Wertheimer et al. (2008a) and Orsi et al. (2008a) reported on improvements to the forecast model and the successful expansion of sampling in 2005-2007. In 2008, the NF continued support, including funding for a second year of fishing efficiency calibration tests between the ADF&G R/V Medeia and the John N. Cobb in anticipation of the deactivation of the John N. Cobb after the 2008 season. Unfortunately, a major mechanical breakdown of the John N. Cobb made it unusable for sampling in 2008 and thereafter. Consequently, NOAA chartered a trawler (the F/V Steller) to replace the John N. Cobb for sampling the northern SEAK stations; fishing power of this vessel was calibrated to the Medeia to maintain the core forecasting time series. Results from the 2008 sampling were reported in Orsi et al. (2009a); results for the forecast model developed from the 2008 sampling efforts were reported in Wertheimer et al. (2009a); and results from the calibration analysis were reported in Wertheimer et al. (2009b). No funding applications to the NF for support of research proposed in 2009 were awarded due to the international economic downturn. Because of the truncated sampling in 2008, funds remained from the 2008 SECM project that could be carried over for additional work in 2009. The Northern Fund Committee approved use of the carryover funds as matching funds for other support awarded by the Alaska Sustainable Salmon Fund (AKSSF). Therefore, this final report includes summaries from both the 2008 and 2009 sampling seasons. Sampling in 2009 was successfully completed in both regions using another chartered trawl vessel, the F/V Chellissa, in July and August, but funding was not in place in time for a June chartering. The Chellissa’s fishing power was calibrated to the Medeia in July so that the entire time series could be compared to the original John N. Cobb data.