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Salmon Escapement (Page updated April 27, 2016)

A weir type used in Japan to capture adult chum salmon in the river. Photo Credit: T. Saito

A weir and fish wheel used in Japan to capture adult chum salmon in the river. Photo Credit: FRA (HNFRI)

What is Salmon Escapement?

Escapement is the number of salmon that “escape” fisheries (i.e., are not harvested) and return to fresh water to spawn.

Why is it Important to Know Salmon Escapement?

Knowledge of escapement (i.e. the number of spawners) is necessary to develop spawner recruit relationships and forecast the production of the next generation, including the number of salmon potentially available to harvest. In addition, knowledge of total run-size for a population (escapement plus catch) is required to compute the survival and productivity of the previous salmon generation and monitor trends in abundance and/or productivity.

Escapement can be estimated using counting fences, mark recapture, visual surveys including area-under-the-curve, and electronic, video, and hydro-acoustic counters. Escapement data are a basic element in salmon fisheries management, including forecasting adult returns to fisheries.

The Working Group on Stock Assessment is compiling information on the state of knowledge of their spawner escapement data. The first step is to document the methods used to monitor and estimate salmon escapement in the NPAFC member countries.

For convenience, references and links to additional information are found at the bottom of this web page.

Escapement Monitoring and Estimation in Japan

Salmon (especially chum salmon) that have escaped coastal fisheries are often stopped during their upstream migration by weirs placed in the river to catch the fish for use as hatchery brood stock. At the weir, efforts are made to collect salmon for brood stock from a range of run timing components (i.e., early- and late-run). Although the weirs typically function as a barrier to upstream migration, some salmon are often allowed to continue their upstream movement and spawn naturally, both before and after the weir is operated. There is increasing interest in understanding the contribution of naturally-spawning fish to total salmon production, although routine escapement monitoring of naturally-spawning fish is not currently conducted.

Escapement Monitoring and Estimation in Korea

Salmon moving upstream beyond salmon fisheries are stopped by a weir in the river. The fish aggregating at the weir are collected and used for hatchery brood stock. Sometimes before and after the weir is functional, some fish may move upriver from the weir and spawn naturally. Routine monitoring of naturally-spawning fish is not conducted. Typically, almost all of the fish that escape coastal and river fisheries are collected at the weir and used for hatchery production.

Escapement Monitoring and Estimation in the Russian Far East (by N. Klovach, VNIRO)

Adult sockeye salmon aggregations in Kurilskoye Lake, Kamchatka.
Photo credit: KamchatNIRO

Sockeye salmon on the redd.
Photo credit: KamchatNIRO

The next generation of salmon. Photo credit: KamchatNIRO

Survey methods used to estimate Pacific salmon escapement abundance throughout the Russian Far East can be divided into three groups: visual survey, remote sensing, and aero-visual methods. Each method has its advantages and disadvantages. Therefore, selection of a survey method depends on several conditions, and foremost among them is the geographical location, accessibility, particular geomorphology, and hydrology of the river basin as well as the financial capabilities of the monitoring agency.

Visual surveys include visual foot surveys and surveys with fishing gear, enumeration fences, and mark-recapture programs.

Visual foot survey. This method is applicable to small streams where total enumeration is possible. Random enumeration is conducted in conditions of abundant Pacific salmon runs or in large river watersheds. In the latter case, monitoring sites are selected in a river channel or on the spawning ground where enumeration is performed, and collected data are extrapolated to the total spawning ground area of the watershed.

Several monitoring sites are selected in the reference river drainage. Location and dimensions of monitoring sites should be representative of the whole reference river, for example representative of the main river channel or tributaries, and comprise not <20% of their length. For a large river drainage (length >400 km) monitoring sites are usually selected in tributaries, which serve as reference rivers. In this situation, monitoring sites can comprise a lesser portion of the drainage area but not <10%.

Surveys with fishing gear. Escapement is estimated based on CPUE (catch per unit effort) indices: numbers of fish per trap-hour, by beach seine, or weight of fish per fishing-day by stationary pound net. There is a strong correlation between in-river net CPUE and daily escapements in the vicinity. This method is used to estimate chum salmon escapement in the Anadyr River. Estimates can be corrected on the basis of visual survey data collected at monitoring sites along the Anadyr River.

Mark-recapture. A portion of fish captured is marked and released, normally near the river mouth. Later, another portion(s) is captured upstream and the numbers of marked and unmarked individuals are counted. The proportion of marked to unmarked fish is used estimate escapement. This method is used to estimate Amur River chum salmon escapement.

Enumeration fences. This method strives for total counts of adult salmon passing through the barrier en route to the spawning grounds and also can regulate abundance on the spawning grounds. Enumeration fences can be erected on small streams, or second and third-order tributaries, where the river channel is gentle enough for a net to be stretched across it and risks of flood are minimal. This method is used on the Ozernaya River to estimate Kurilskoye Lake sockeye salmon escapement.

Other approaches used to estimate escapement include remote sensing techniques such as hydro-acoustics and video and photo recording methods.

DIDSON hydro-acoustic unit in operation in the Chilko River, British Columbia. Photo credit: CDFO

Hydro-acoustic methods. Hydro-acoustic techniques involve counting the fish as they travel within the range of the hydro-acoustic detection system. The mobility of hydro-acoustic units, simplicity of installation and maintenance in the river at almost any site in the watershed, and operational efficiency in data processing are advantages of using hydro-acoustics. A serious drawback for full implementation of hydro-acoustics is the high cost of the units. Hydro-acoustic systems are used to enumerate fish in the rivers of the Kamchatka Peninsula, continental coast, and Chukotka, and rivers draining into the Sea of Okhotsk.

Remote sensing with video and photo recording. The use of video equipment for recording Pacific salmon escapement began in 2012. A video survey was conducted in the Iska River watershed (Sakhalin Bay of the Sea of Okhotsk). This method is still in the developmental stage.

A third set of techniques to estimate escapement include aero-visual methods.

Aero-visual methods. These methods allow for efficient coverage over vast areas by observing a large number of watersheds quickly. This factor is extremely important for large river drainages, especially where the ground-transportation infrastructure is poorly developed, as is the case along the continental coast in the northern part of the Sea of Okhotsk and in Kamchatka.

Fish counting at a particular site within a river or lake is the basis of this method. Salmon aggregations are counted by tens, hundreds, or thousands, depending on fish abundance and density. Counting accuracy depends on fish density, distribution in the river channel, light conditions, tree crown density, river depth, and water transparency. Small aircraft or helicopters travelling at speeds of 100-120 km/hr at a height of 100-150 m are usually used to perform these surveys.

Aerial view of salmon in the Chilko River, British Columbia. Photo credit: CDFO

Aero-visual surveys of salmon spawning watersheds are usually conducted close to completion of the main portion of the run for each salmon species to minimize errors in estimating escapement. If possible, aero-visual surveys are usually followed by photo documentation at particular spawning sites.

On the Kamchatka Peninsula, aero-visual methods have been used since 1950. More than 50 years of aero-visual survey experience has been gained by observations on the northern coast of the Sea of Okhotsk. A comprehensive system estimating total salmon escapement throughout the Kamchatka Peninsula has existed until 2005. Every year there was funding available for 500-600 flight hours. Currently, lower funding has reduced the survey period to 250 flight hours. Reference watersheds are surveyed and data are extrapolated to the whole region with similar conditions for salmon reproduction.

Estimating escapement is the basis for the preseason salmon-run forecast. Total salmon enumeration provides for maximum accuracy in estimates, however, this method has a random character. Estimates of escapement based on enumeration of reference rivers, which are extrapolated to regions of similar conditions for salmon reproduction, reflect salmon stock status.

Escapement Monitoring and Estimation in Canada (by A. Tompkins and J. Irvine, CDFO)

Sockeye salmon migrating through a tunnel on the Somass River system, British Columbia. The camera looks down onto the tunnel providing a top view (bottom panel) and uses a mirror to provide the side view (top panel). The lines on the back wall are used to identify species-specific size categories, in this case ‘jack’ sockeye. Photo credit: CDFO

The Canadian Department of Fisheries and Oceans (DFO) Pacific Region conducts escapement monitoring for five species of salmon native to British Columbia (B.C.). Tompkins and Baxter (2015) NPAFC Doc. 1604 summarize the escapement methodology and management of escapement data for Pacific salmon stocks monitored by the DFO. Escapement programs are delivered at three levels of intensity: indicator, intensive, and extensive programs, in order of monitoring effort, and accuracy and precision of estimates. The collection of salmon escapement information involves a diverse set of methodologies with a range of accuracy and precision from qualitative observations of presence/absence, to indices of total abundance, or to relatively accurate counts of spawners. The enumeration method used is dependent on the stream characteristics, hydrological conditions, the behavior of the fish, and availability of resources. Visual surveys (walk, snorkel, boat) including aerial counts (helicopter, fixed wing) are commonly used to provide an index of escapement from year to year. Mark recapture studies, fixed weir and fence counts, provide generally escapement estimates of higher accuracy and precision but typically require more effort and resources to implement.

The DFO maintains salmon escapement data, including individual spawner survey records and population escapement estimates, in the Salmon Escapement Database (NuSEDS). Annual abundance estimates are maintained by population, as defined by freshwater location and run timing. The NuSEDS database currently reports salmon spawning observations for 9000+ individual populations but escapement estimates are available for 1200+ populations. Individual population estimates go back as far as the early 1950s, but there are variations in the methodologies used and their reliability. Thus, the quality of the data must be considered when interpreting escapement information.

Salmon escapement estimates and metadata by population (e.g. number of surveys, survey dates, estimate method, etc.) are publicly available through the internet at:

http://open.canada.ca/data/en/dataset/c48669a3-045b-400d-b730-48aafe8c5ee6.

DFO also maintains a publicly accessible database of recruits/spawner data for sockeye, pink, and chum salmon described by Ogden et al 2015.

Escapement Monitoring and Estimation in USA

Alaska (by E. Volk and A. Munro, ADF&G)

The Alaska Department of Fish and Game (ADF&G) manages salmon fisheries to achieve spawning escapement goals, or targets, to provide sustained yields and ensure long-term viability of salmon stocks. Currently, there are approximately 300 established escapement goals in Alaska.

Pink salmon on the spawning grounds of Southeast Alaska. Photo credit: A. Piston, ADFG

The Auke Creek Research Station, Southeast Alaska, where downstream counts of pink salmon fry and upstream counts of adults are monitored. Photo credit: J. Joyce, NOAA Fisheries

Each year, escapements for these stocks and others without formal goals are reported in Area Management Reports. Since 2010, the department has produced a publically accessible report that is a statewide compilation of salmon escapements and escapement goals. The most current report can be found on the ADF&G website at:

http://www.adfg.alaska.gov/index.cfm?adfg=specialstatus.akfishstocks.

Past reports can be found by searching the ADF&G Publications Searchable Database

http://www.adfg.alaska.gov/sf/publications/.

Recently, Volk and Munro (2015) NPAFC Doc. 1588 was prepared for the Stock Assessment Working Group and NPAFC. This document provides an overview of field and analytical approaches used to estimate escapements in Alaska (including assumptions, qualifiers and issues associated with those methods). This information provides recent escapement data for all assessment projects tied to formal escapement goals as an example of what is produced in ADF&G’s annual statewide escapement goal report.

Washington (by E. Neatherlin, WDFW)

The Washington Department of Fish and Wildlife (WDFW) manages salmon and steelhead populations to achieve its primary mission: to preserve, protect, and perpetuate fish, wildlife, and ecosystems while providing sustainable fish and wildlife recreational and commercial opportunities. In many parts of Washington State WDFW co-manages salmonid populations in common with Native American tribes, as mandated by US treaties.

Data collection and escapement estimation methods for these populations vary considerably. Data collection methods include (but are not limited to) fish and redd counts by foot, boat, plane, or helicopter (Johnson et al. 2007). Escapement estimation methods include (but are not limited to) expansion of redd, trap, peak live, and dead fish counts, Area Under the Curve (AUC), mark-recapture, and video monitoring. A WDFW website, Salmon Conservation and Reporting Engine (SCoRE), is available to the public that contains more detailed descriptions of these methods.

SCoRE homepage: https://fortress.wa.gov/dfw/score/score/

Escapement data: https://fortress.wa.gov/dfw/score/score/maps/map_salmon_recovery.jsp

References and Additional Information

Japan

Miyakoshi, Y., et al. 2012. The occurrence and run timing of naturally spawning chum salmon in northern Japan. Environ Biol Fish 94:197-206. DOI 10.1007/s10641-011-9872-5

Morita, K. 2014. Japanese wild salmon research: toward a reconciliation between hatchery and wild salmon management. NPAFC Newsl 35: 4-14.

Saito, T. 2015. Biological Monitoring of Key Salmon populations: Japanese chum salmon. NPAFC Newsl 37: 11-19.

Korea

Kang, M., et al. 2016. Biological monitoring of a key Korean salmon population: Namdae River chum salmon. NPAFC Newsl 39: 15-20.

Russia

Koval, M., et al. 2014. Biological monitoring of a key salmon population: Ozernaya River sockeye salmon of West Kamchatka. NPAFC Newsl 35: 15-20.

Escapement estimates have been documented in a series of NPAFC Documents. (Please note escapement data are not reported for 2003 or 2008.) See following list.

TINRO. 1993. Catch data and salmon enhancement production in Russia. NPAFC Doc. 41.

TINRO. 1994. Statistics of Russian Catches of Pacific salmon. NPAFC Doc. 103.

Radchenko, V.I. 1995. Russian statistical data on commercial catches, escapement, average weight of Pacific salmon in 1994. NPAFC Doc. 170 (Rev 1).

Radchenko, V.I., and O.A. Rassadnikov. 1996. Russian Pacific salmon statistics 1995. NPAFC Doc. 233.

Ministry of Agriculture and Food of the Russian Federation Department of Fisheries. 1997. Biostatistical information on salmon catches in Russia in 1996. NPAFC Doc. 283 Rev. 1.

TINRO-Center. 1998. Biostatistical information on salmon catches in Russia in 1997. NPAFC Doc. 377.

TINRO-Center. 1999. Biostatistical information on salmon catches in Russia in 1998. NPAFC Doc. 449.

TINRO-Center. 2000. Biostatistical information on salmon catches, escapement, outmigrant number, and enhancement production in Russia in 1999. NPAFC Doc. 505.

TINRO-Center. 2001. Biostatistical information on salmon catches, escapement, outmigrant number, and enhancement production in Russia in 2000. NPAFC Doc. 573.

TINRO-Center. 2002. Biostatistical information on salmon catches, escapement, outmigrant number, and enhancement production in Russia in 2001. NPAFC Doc. 646.

TINRO-Center. 2003. Biostatistical information on salmon catches, escapement, outmigrants number, and enhancement production in Russia in 2002. NPAFC Doc. 736.

TINRO-Center. 2005. Russian Pacific salmon hatchery releases, commercial fishery catch statistics, and sport fishery harvest statistics for 2004 season. NPAFC Doc. 918 Rev 1.

TINRO-Center. 2005. Biostatistical information on salmon catches, escapement, outmigrants number, and enhancement production in Russia in 2005. NPAFC Doc. 999.

Anonymous. 2007. Biostatistical information on salmon catches and escapement in Russia in 2006. NPAFC Doc 1063.

TINRO-Center. 2008. Biostatistical information on salmon catches, escapement, outmigrants number, and enhancement production in Russia in 2007. NPAFC Doc. 1136

TINRO-Center. 2010. Biostatistical information on salmon catches, and enhancement production in Russia in 2009. NPAFC Doc. 1269.

TINRO-Center. 2011. Biostatistical information on salmon catches, and enhancement production in Russia in 2010. NPAFC Doc. 1329.

TINRO-Center, and VNIRO. 2012. Biostatistical information on salmon catches, escapement and enhancement production in Russia in 2011. NPAFC Doc. 1430 Rev 1.

Klovach, N.V., et al. 2013. Biostatistical information on salmon catches, and enhancement production in Russia in 2012. NPAFC Doc. 1487.

Klovach, N.V., et al. 2014. Biostatistical information on salmon catches, and enhancement production in Russia in 2013. NPAFC Doc. 1502.

Klovach, N.V., et al. 2015. Biostatistical information on salmon catches, escapement and enhancement production in Russia in 2014. NPAFC Doc. 1565 Rev 4.

Canada

Ogden, A.D., et al. 2015.  Productivity (Recruits-per-Spawner) data for Sockeye, Pink, and Chum Salmon from British Columbia. Can. Tech. Rep. Fish. Aquat. Sci. 3130: vi + 57 p.  Data and report available at:
http://open.canada.ca/data/en/dataset/3d659575-4125-44b4-8d8f-c050d6624758

Tompkins, A., and B. Baxter. 2015. Pacific salmon escapement estimation methods and data for Canada. NPAFC Doc. 1604.

Tompkins, A., et al. 2014. Biological monitoring of key salmon populations: technological improvements in escapement estimation in British Columbia. NPAFC Newsl 36: 20-25.

USA

Johnson, D.H., et al. 2007. Salmonid Protocols Handbook: Techniques for assessing status and trends in salmon and trout populations. American Fisheries Society. Bethesda MD. p. 478.

Orsi, J., et al. 2014. Biological monitoring of key salmon populations: Southeast Alaska pink salmon. NPAFC Newsl 36: 13-19.

Washington Department of Fish and Wildlife. (2016). Salmon Conservation and Reporting Engine. Retrieved from https://fortress.wa.gov/dfw/score/score/

Volk, E.C., and A.R. Munro. 2015. Pacific salmon escapement estimation methods and data for Alaska. NPAFC Doc. 1588.






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