Improved Estimates of Escapement, Survival and Exploitation for Nicomen Slough Coho

Coho escapement to the Lower Fraser River (LFC) management unit (MU) is an important requirement of the Fishery Regulation Assessment Model (FRAM) but is estimated with unknown and high uncertainty. Inch Creek Coho are used as the hatchery coded-wire tag (CWT) indicator stock for LFC, but estimates of survival and exploitation rates lack precision due to the low number of CWT recoveries from recreational fisheries and spawning ground escapement surveys in the Nicomen Slough. However, hatchery raised Coho from Norrish Creek (a tributary to Nicomen Slough) are adipose-fin-clipped (AFC) and released into Nicomen Slough, but CWT’s are not applied. We propose to reduce the uncertainty in survival and exploitation rate estimates by doubling the number of CWTs available to be sampled by applying CWTs to Norrish Creek Coho in addition to Inch Creek Coho. Additionally, expanding Creel survey coverage in Nicomen Slough will yield greater recovery of CWT’s, further reducing the uncertainty of our estimates of survival and exploitation for the LFC MU. This work would bring us closer to being able to generate an entire system estimate of LFC escapement for use in FRAM when combined with a Lillooet Coho CU SONAR project (proposed by LGL and in their second year of SEF Funding) and a potential future Lower Fraser test fishery. The improved estimates generated from this current work would better inform backward FRAM exploitation rate estimates, and increase the quality of the forecasts for use in forward FRAM to plan bilateral fisheries. Lastly, we propose to analytically produce a more accurate estimate of the escapement of natural-origin Coho in Nicomen Slough and measure the precision of that estimate from the additional information generated from this project.