Coho Marine Survival Model
Spatial Design
Temporal Design
Response Design
Inference Design
References
The marine survival models reported on this site are documented in the Final Amendment 13 to the Pacific Coast Salmon Plan (revised in the 2000 Review). Since data for marine survival rates for wild fish were not available at the time that that Amendment 13 came out, the smolt-to-jack survival rates of hatchery produced coho in the Oregon Production Index (predominantly Columbia River hatcheries) were considered to be the best available predictor to determine high, medium and low adult marine survival categories. At the time it was noted that if better predictors were determined in the future, they would replace the jack predictor after review and approval by the SSC and Council. Such an effort is currently underway using marine survival data for wild coho collected at several life-cycle monitoring sites along the Oregon coast.
Spatial Design
Data on smolt-to-jack and subsequent smolt-to-adult coho survival are collected at Columbia River and Oregon coastal hatcheries.
Temporal Design
Data for adult return years 1970-1996 were usedboth for the initial analysis and for the 2000 review.
Response Design
The marine survival rate for hatchery-origin jack coho was calculated by dividing the number of returning jacks by the number of smolts released. The marine survival rates for hatchery-origin adult coho were calculated by dividing the number of returning adults by the number of smolts released. This approach was retained in the 2000 Review.
Inference Design
Marine survival rates were placed into three categoriesunder Amendment 13. The 2000 review added a fourth category. The categories outlined in the 2000 review are defined as follows:
“Extremely Low” (EL) jack:smolts ratios of <0.0008 - At the upper bound of this category marine survival would be expected to be at a level such that populations would fail to replace themselves even in the absence of harvest. It is expected that marine survival of hatchery fish will be less than 1%. Adult marine survival observed in the “Extremely Low” category ranges from 0.5% to 1.3% and averages 0.7%. For modeling purposes it was assumed that marine survival of wild fish in this category would be twice that of hatchery fish (Nickelson 1986, Seiler 1989).
“Low” (L) jacks:smolts ratios of 0.0008-0.0014 - Average marine survival in this category should result in populations at 50-100% of full seeding in the absence of harvest, depending upon beginning population size. Under the conditions of this category it is expected that marine survival of hatchery fish will range from 1% to possibly 3%. Marine survival observed in the Low category ranges from 1.1% to 2.4% and averages 2.0%. For modeling purposes it was assumed that marine survival of wild fish in this category would be 1.5 times that of hatchery fish.
“Medium” (M)jacks:smolts ratios of >0.0014-0.0040 - When marine survival rates are in this category the population on average, experiences recruitment >1.5 across the entire spectrum of parental spawner abundance. By this definition the “Medium” category would functionally encompass all marine survival rates greater than those observed in the “Low” category. However, groupings of the empirical data in the relationship between jacks per smolt and adults per smolt clearly point to a fourth category of higher marine survival and were useful for identifying an upper boundary for the “Medium” category. Under the conditions of this category it is expected that marine survival of hatchery fish will range from slightly less than 3% to a high of 6-8%. Marine survival observed in the new “Medium” survival category ranges from 2.9% to 8.4 and averages 4.5%. For modeling purposes it was assumed that marine survival of wild fish would be 1.5 tunes that if hatchery fish at the low end of the category and equal to that of hatchery fish at the high end of the category.
“High” (H)jacks:smolts ratios of >0.0040 - This category remained the same as originally designed in Amendment 13. Empirical data in the relationship between jacks per smolt and adults per smolt were useful for identifying a group of marine survival values in the upper end of the range that correspond to this category. Under the conditions of this category it is expected that marine survival of hatchery fish will be greater than 8%. Adult marine survival observed in the High category ranges from 8.6% to 11.7% and averages 10.2%. For modeling purposes it was assumed that marine survival of wild fish in this category would be the same as that of hatchery fish (Nickeson 1986).
Adults-per-smolt is predicted from observations of jacks per smolt. A linear regression of the adult hatchery coho survival rates on the jack survival rates for the data set from 1970-1996 indicates that the predicted hatchery smolt-to-adult survival levels show a generally strong relationship between the jack survival and adult survival categories (r2 = 0.85)
Relationship of jack:smolt versus adult:smolt ratios for OPI hatchery coho (the four different shaded symbols represent the four new marine survival categories in the revised harvest management matrix.)
References
Nickeson, T.W. (1986). Influences of upwelling, ocean temperature, and smolt abundance on marine survival of coho salmon (Oncorhynchus kisutch) in the Oregon Production Area. Can. J. Fish. Aquat. Sci. 43:527-535.
PFMC. (1999). Final Amendment 13 to the Pacific Coast Salmon Plan. Fishery management regime to ensure protection and rebuilding of Oregon coastal natural coho. Pacific Management Council. Portland, Oregon.
ODFW and PFMC. (2000). 2000 Review of Amendment 13 to the Pacific Coast Salmon Plan. Pacific Management Council. Portland, Oregon.