The STADEM model estimates total escapement of spring/summer Chinook salmon and steelhead crossing Lower Granite Dam (LGR). Total escapement includes estimates of uncertainty and is parsed into weekly strata for three origin groups: natural-origin, hatchery (clipped), and hatchery (unclipped). The DABOM model estimates adult escapement of natural-origin spring/summer Chinook salmon and steelhead in various tributaries within the Snake River basin above LGR. Together, these models provide robust estimates of escapement for natural-origin spring/summer Chinook to populations and sub-populations throughout the Snake River basin.
The STADEM model uses two independent observations of the true number of fish crossing the dam, 1) window counts at LGR and 2) trap catch data from the adult sampling facility at LGR, and integrates them in a state-space model with a weekly time-step. Moreover, STADEM uses information from adults PIT tagged prior to arriving at LGR crossing the dam each week to account for night-time passage and fallback-and-reascension at LGR.
The DABOM model uses information on 1) natural-origin total escapement estimates at LGR (e.g., from the STADEM model), and 2) information from adults PIT tagged at LGR that are subsequently detected at Instream PIT Tag Detection Systems (IPTDS) throughout the Snake River basin to estimate spawning escapement into populations and sub-populations of spring/summer Chinook salmon and steelhead. In addition, the DABOM model can incorporate biological information taken from individual fish at the adult trap (provided by BPA projects 1991-073-00, 1990-055-00, and 2010-026-00 in the LGTrappingDB) to provide age and sex composition and length frequency for specific populations, as well as total wild escapement.
Findings and Uses
STADEM provides unbiased estimates of total escapement at LGR for both Chinook and steelhead species under a wide-range of scenarios, with high coverage probability. It also provides unbiased estimates of tributary escapement with high coverage probabilities, and has been validated against independent estimates of tributary escapement (e.g., weirs).
The STADEM and DABOM models can be used with biological information (length, sex, age, and genetics) from other BPA projects to inform management of natural-origin Chinook salmon and steelhead in the Snake River basin.
Results can also be used to inform conservation status and population viability analyses.