Confidence intervals for fish out-migration estimates using stratified trap efficiency methods

Emigration of Natural and Hatchery Naco x (Chinook salmon; Oncorhynchus tshawytscha) and Heeyey (Steelhead; Oncorhynchus mykiss) Smolts from the Imnaha River, Oregon from 5 October 2006 to 21 June 2007, Annual Report 2007.

“…This estimate is a minimum estimate based on trap efficiency trials in the fall of 2006 and spring of 2007. To maintain robustness for analysis, we set a lower limit of seven mark recaptures for any period (Steinhorst et al 2004). …”

“…Spring and fall emigration indexes of juvenile abundance for natural Nacó'x (Chinook salmon) and spring emigration indexes of Héeyey (steelhead) smolts migrating past the trap were estimated using the Gauss program (Aptech Systems Inc., Maple Valley, Washington) with a Bailey trap efficiency estimation method (Steinhorst et al 2004). The Bailey estimate is a version of the Lincoln-Peterson method and is used to develop the point estimate.…”

Snake River Sockeye Salmon Captive Broodstock Program Research Elements : 2007 Annual Project Progess Report.

“…Stream velocity was measured below the trap weekly. Out-migrant run size was derived using a modified Bailey estimator and 95% bootstrap confidence intervals using methods described by Steinhorst et al (2004). Smolt out-migration estimates were calculated separately for natural origin and fall direct-released hatchery origin sockeye salmon smolts.…”

Idaho Steelhead Monitoring and Evaluation Studies : Annual Progress Report 2007.

“…If the kelt was alive, the trap tender punched the left operculum and passed it downstream. We used two methods to estimate steelhead escapement: 1) summing the number of adults trapped in the upstream livebox and the number of unmarked kelts recovered, and 2) a maximum likelihood estimate using the number of marked fish passed upstream of the weir, the total number of kelts recovered, and the number of marked kelts recovered (Steinhorst et al 2004). …”

“…Fall was from August 15 until trap removal. Using software developed by Steinhorst et al (2004), we estimated emigrant abundance by season with Bailey's modification of the Lincoln-Peterson estimator. The 95% confidence intervals were computed with the bootstrap option.…”