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Tower counts

By:
Compiled by:
D.H. Johnson , Brianna M. Shrier , Jennifer S. O'Neal , John A. Knutzen , Xanthippe Augerot , Thomas A. O'Neal , and Todd N. Pearsons

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Abstract

Counting towers provide an accurate, low-cost, low-maintenance, low-technology, and easily mobilized escapement estimation program compared to other methods (e.g., weirs, hydroacoustics, mark-recapture, and aerial surveys) (Thompson 1962; Siebel 1967; Cousens et al. 1982; Symons and Waldichuk 1984; Anderson 2000; Alaska Department of Fish and Game 2003). Counting tower data has been found to be consistent with that of digital video counts (Edwards 2005). Counting towers do not interfere with natural fish migration patterns, nor are fish handled or stressed; however, their use is generally limited to clear rivers that meet specific site selection criteria. The data provided by counting tower sampling allow fishery managers to determine reproductive population size, estimate total return (escapement + catch) and its uncertainty, evaluate population productivity and trends, set harvest rates, determine spawning escapement goals, and forecast future returns (Alaska Department of Fish and Game 1974-2000 and 1975-2004). The number of spawning fish is determined by subtracting subsistence, sport-caught fish, and prespawn mortality from the total estimated escapement. The methods outlined in this protocol for tower counts can be used to provide reasonable estimates ( plus or minus 6%-10%) of reproductive salmon population size and run timing in clear rivers. 

Additional publication details

Publication type:
Book chapter
Publication Subtype:
Book Chapter
Title:
Tower counts
ISBN:
9781888569926
Year Published:
2007
Language:
English
Publisher:
American Fisheries Society
Contributing office(s):
Alaska Science Center
Description:
22 p.
Larger Work Type:
Book
Larger Work Subtype:
Instruction
Larger Work Title:
Salmonid Field Protocols Handbook: Techniques for Assessing Status and Trends in Salmon and Trout Populations
First page:
363
Last page:
384
Online Only (Y/N):
N
Additional Online Files (Y/N):
N