3.2.1 Standards, Protocols and Guidelines: Salmon Escapement Estimation

Introduction

All salmon stock management systems rely on estimates of annual and seasonal variations in total abundance determined at each of several life history stages by a variety of different methods. Because of the history and focus on adult salmon as a harvestable resource, the most basic fisheries management system depends on annual assessments of total returns of adults. Total returns consist of all fish of a given species and “stock” accounted for in catch plus the remainder that manage to escape harvest in fisheries to return as spawners to their freshwater locations of origin. Consequently, the number of spawners that succeed in returning to a given lake or stream is also commonly known as the “escapement”. Thus, annual assessments of salmon escapement and associated variables are critical activities required to satisfy federal, First Nations/treaty tribal, provincial, and state fisheries agency mandates in several areas including: (1) stock conservation, (2) compliance with fiduciary obligations to aboriginal fisheries groups, (3) harvest management, (4) habitat conservation and management, (5) indexing and maintenance of ecosystem integrity, and (6) stock and habitat research.

The collection of salmon escapement information involves a diverse set of activities including specification of stream survey enumeration plans, training of field surveyors, data gathering and documentation, data review and upload, data analysis or synthesis of summary estimates, and release of the data to both internal (i.e. fisheries agency personnel) and external clients.  In Canada the coordination of these activities is performed by federal (Stock Assessment Division of Fisheries and Ocean’s Science Branch) or provincial stock assessment groups.  In the U.S. these activities typically are coordinated by the state and tribal fishery managers.

Standards

Standards are intended to provide information of a specific quality, in terms of accuracy, precision, and reliability, to attain specific objectives, and so the standards for salmon escapement programs vary depending according to scientific objectives.  Ultimately the choice of standards rests with the principal investigator and balance between program objectives, resources, and characteristics of the species and environment.

The accuracy, precision and reliability of escapement estimates are affected by characteristics such as the assessment method, species behaviour, hydrological and other environmental conditions (as seen in Table 1 below).  It is often highly demanding on resources to gain information about the accuracy (i.e., the amount by which the average of repeated estimates exceeds or falls below the true value of the indicator in nature) of a specific assessment method under certain conditions, so such studies are typically rare.  However from the limited information available, there are several types of assessment methods with common aspects of accuracy, precision, and reliability, while recognizing that exceptions occur (Table 1). 

Enlarge Image

Protocols and Guidelines

Escapement assessment methods are well described in the scientific fisheries literature (see example references below), including peer-reviewed papers, published manuscript reports, and text books.  However, study designs can vary among locations and species to best achieve a balance between objectives, resources, species behaviour and environmental conditions which has contributed to a high diversity among the methods used to estimate salmon spawner numbers and other life stages such as redds, eggs, and juveniles (e.g. fry, smolts, etc.).  Typically assessment methods are described in manuscript reports, stream narratives, or stock assessment reports to communicate the quality of the annual escapement estimate or assessment program.  Table 2 lists common survey methods used to enumerate salmon spawners:

Table 2. Common survey methods for salmon spawners.

Enlarge Image

Resisitivity counter at Deadman River, B.C.

Resisitivity counter at Deadman River, B.C.

General References (methods for estimating spawning escapement)

Atkinson, C. E. 1944. The problem of enumeration of spawning populations of  sockeye salmon. Int. Pac. Salmon Fish. Comm. Annu. Rep. 1943: 37-44.  

Canada Department of Fisheries and Oceans, Pac. Reg., Field Serv. Br. 1986. Fishery officer's guide to consistency in the collection, recording, and use of  sub-district salmon management data. CDFO Unpubl. manual: 22p.      

Canada Department of Fisheries and Oceans, Pac. Reg., Field Serv. Br. 1986. Corroboration exercises in field counting techniques for the enumeration of spawning salmon. CDFO Unpubl. manual: 50p.   

Fredd, L. C. 1966. Review and analysis of fish counts, counting techniques and related data at Corps of Engineers dams on the Columbia and Snake Rivers. U. S. Army Corps of Engineers, Fish. Eng. Res. Program Prog. Rep. 3: 91-95.   

Hilborn, R. 1983. Design of the B.C. salmon escapement monitoring system: notes from a workshop. Misc. Coop. Fish. Res. Unit Rep. 6: 25 p.   

Ricker, W. E. 1975. Computation and interpretation of biological statistics of fish populations. Bull. Fish. Res. Board. Can. 191: 382 p.

Ricker, W. E. (Ed.). 1968. Methods for assessment of fish production in fresh waters. Int. Biol. Prog. Handbook 3: 313 p.   

Russell, L. R. 1975. An annotated bibliography on salmonid marking, enumeration and trapping techniques. B. C. Fish and Wildlife Branch Fish. Tech. Circ. 18: 194 p.    Ref #: 1-75

Seber, G. A. F. 1982. The estimation of animal abundance and related parameters. Charles Griffin & Co. Ltd., London: xvii + 654 p.

Smith, C. J. and P. Castle. 1994. Puget Sound chinook salmon (Oncorhynchus tshawytscha) escapement estimates and methods – 1991. NW Indian Fisheries Commission, Olympia, WA., NW Fishery Resource Bulletin Project Report Series 1:
Straty, R. R. 1960. Methods of enumeration of salmon in Alaska. Trans. 25th N. Am. Wildl. Nat. Resour. Conf.: 286-297.   

Symons, P. E. K. and M. Waldichuk. 1984. Proceedings of the workshop on stream indexing for salmon escapement estimation, West Vancouver, B. C., 2-3 February 1984. Can. Tech. Rep. Fish. Aquat. Sci. 1326: 258 p. 

Comparison of Methods

Andrew, J. H., G. D. Sutherland, and T. M. Webb. 1988. Abundance, age, size, sex and coded wire tag recoveries for chinook salmon escapements of Atnarko River, 1984-1986. Can. Manusc. Rep. Fish. Aquat. Sci. 2014: viii + 87 p.        

Bailey, R.E., C.K. Parken, J.R. Irvine, B. Rosenberger, M.K. Farwell. 2000.  Evaluation of utility of aerial overflight-based estimates versus mark-recapture estimates of Chinook salmon escapement to the Nicola River, B.C.  Canadian Science Advisory Secretariat, Research Document 2000/152.

Beidler, W. M., T. E. Nickelson, and A. M. McGie. 1980. Escapement goals for coho salmon in coastal Oregon streams. Ore. DFW. R&D Inf. Rep. Ser., Fish. 80-10: 30 p.   

Bocking, R. C., J. R. Irvine, K. K. English, and M. Labelle. 1988. Evaluation of random and indexing sampling designs for estimating coho salmon (Oncorhynchus kisutch) escapement to three Vancouver Island streams. Can. Tech. Rep. Fish. Aquat. Sci. 1639: 95 p.   

Johnston, N. T., J. R. Irvine and J. C. Perrin. 1986. A comparative evaluation of fence count, mark-recapture and Bendix sonar estimates of salmon escapements in the Keogh River a variable-flow coastal B. C. stream. Can. Tech. Rep. Fish. Aquat. Sci. 1453: 44 p.   

Johnston, N. T., J. R. Irvine, and C. J. Perrin. 1987. Instream indexing of coho salmon (Oncorhynchus kisutch) escapement in French Creek, British Columbia. Can. Tech. Rep. Fish. Aquat. Sci. 1573: 37 p.

McBride, D. and D. Mesiar. 1981. Nushagak sonar enumeration project, 1980. Alaska Dept. Fish Game Bristol Bay Data Rep. 83: 45 p.   

Namtvedt, T. B., N. V. Friese, D. L. Waltemyer, M. L. Bethe and D. C. Whitmore. 1977. Investigations of Cook Inlet sockeye salmon. Alaska Dep. Fish Game. Tech. Rep. for period July 1, 1975 to June 30, 1976: 75 p.   

Robson, D. S. and H. A. Regier. 1968. Estimation of population number and mortality rates. Pages 124-158, In: Ricker, W. E. (Ed.). 1968. Methods for assessment of fish production in fresh waters. Int. Biol. Prog. Hanbook 3:   313 p.   

Tschaplinski, P. J. and K. D. Hyatt. 1990. Abundance, migration timing, and biological characteristics of sockeye salmon (Oncorhynchus nerka) returning to Henderson Lake, Vancouver Island during 1988. Can. Tech. Rep. Fish. Aquat. Sci. 1758: iv + 82 p.   

Tschaplinski, P. J. and K. D. Hyatt. 1991. A comparison of population assessment methods employed to estimate the abundance of sockeye salmon (Oncorhynchus nerka) returning to Henderson Lake, Vancouver Island during 1989. Can. Tech. Rep. Fish. Aquat. Sci. 1798: 101

Zubik, R. J. and J. J. Fraley. 1988. Comparison of snorkel and mark-recapture estimates for trout populations in large streams. N. Am. J. Fish. Man. 8: 58-62.


| Go Back