Integrating Life History to Improve Survival in the Captive Setting: Lessons Learned from Two Rearing Cycles of Odd-Year Pink Salmon Displaced By the Elwha Dam Removal

A captive broodstock program was initiated for odd-year Elwha River Pink Salmon (Oncorhynchus gorbuscha) to conserve the unique genetics of this stock during dam removal (2011-2014).  Broodstock collection, spawning, incubation, and rearing to swim-up stage were conducted at Tribal and State facilities.  In a pioneering effort, seawater rearing of two broodyears (BY 2011 and BY 2013) was conducted at the Manchester Research Station in 6 m circular indoor tanks supplied with processed seawater (filtered to 5 µm/UV-sterilized).

Marine survival of the first broodyear (BY 2011) sufficiently met production needs.  In order to improve fish quality, second broodyear (BY 2013) fish were transferred to seawater earlier and rearing and feed methodologies were altered to better complement the species’ natural life history.  These changes eliminated early marine mortality caused by delayed seawater transfer (marine survival after 21 days BY11 59.6%, BY13 99.2%) and increased both survival (BY11 30.8%, BY13 66.3%) and size at first fall (BY11 71.4g, BY13 112g).  It is anticipated that the modifications discussed here will foster a higher maturation rate of BY 2013 fish at Age 2 (BY 2011 74%).  The program demonstrates captive broodstock technology can be utilized to conserve pink salmon during temporary habitat loss.