Category: 2017

A Fishwheel-ARIS study to evaluate the ARIS length-based discrimination estimates of species composition for the Mission Hydroacoustic monitoring site

Studies and analyses conducted from 2009-15 have demonstrated the spatially-stratified hydroacoustic counts can be combined with species composition data from the fishwheels and Whonnock test fisheries to produce scientifically defensible estimates of the number of sockeye and pink salmon that pass the Mission hydroacoustic site in odd-number years (Robichaud et al. 2010; English et al. 2016). In 2013 and 2015, fish length data derived from images acquired by imaging sonar DIDSON was used in mixture-model discrimination analysis to derive species composition estimates for the near-shore strata monitored by the DIDSON systems at the Mission hydroacoustic site (Grant et al. 2014). Substantial differences have been observed between the DIDSON length-based species composition estimates for near-shore strata and those derived from fishwheel samples (English et al. 2016). Both methods have their strengths and weaknesses. For the fishwheel, species should be identified accurately, but sockeye and pink salmon may not be equally vulnerable to the gear. For the imaging sonar systems, both species should be equally vulnerable to being observed in the image, but the measurement of lengths from the DIDSON images is less precise than manual measurements and the length distributions of sockeye and pink salmon are highly overlapped. To date, the PSC1 estimates of sockeye proportions derived from DIDSON length-based approach have tended to be higher than those derived from the fishwheel samples. Being a next generation of DIDSON, the adoptive resolution imaging sonar (ARIS) can provide a much higher down-range resolution than DIDSON for fish images. Through this project, we will assess the reliability of the ARIS length-based species composition estimates and further explore the potential causes of the discrepancies between ARIS and fishwheel based species proportions.


Cowichan Adult Chinook Enumeration methodology change

Adult Chinook returning to the Cowichan River have been enumerated using a counting fence since 1988 as a PSC indicator stock. The operation of the fence has been met with various technical/environmental challenges over the years resulting in site relocation as well as several re-builds. Cowichan Tribes has expressed concern regarding negative impacts to fish including migration delays and physical damage.  This proposal will investigate the use of PIT tags as an alternative method for estimating escapement.   Specifically, tags returning from juvenile deployments will be expanded based on a mark rate from a sub-sample of the population.  PSC funding will be used to both deploy tags in juveniles as well as to support an estimate of mark rate in the adult population.

The use of PIT tags will also allow additional information to be collected including downstream survival of juveniles, marine survival estimates, age class composition and migration time.  Additionally, predation investigations may also be supported as PIT tags have been detected inside other animals and in scat within the surrounding area.

Bessette Creek Resistivity Counter

The installation of a temporary automated fish counting system (resistivity counter) is being proposed for the Bessette Creek watershed to provide accurate escapement information for Coho salmon. Escapements in this system are currently estimated via streamwalks and the Area-Under-the-Curve method. Migrations of returning Coho are multimodal and often extended over a long period. Their propensity to move during high water events, to occupy systems intermittently, and to behave cryptically/defensively once at their spawning grounds can make visual enumerations difficult. As a result, it is a real challenge to accurately enumerate Coho returns using ground surveys in complex habitat such as the Bessette Watershed. Visual counting conditions are frequently poor due to high flows, turbid and dark water conditions (tannins), which probably leads to an underestimate of the spawning escapement. One method that has proven effective in this situation is resistivity. It is able to remain in place during high water events if properly situated, can see past turbid conditions and can remain running for extended periods of time. An electronic counter, although initially expensive to install, can supply accurate escapement estimates of salmonids for many years to come at a fraction of the cost of existing labour intensive techniques. The information can be downloaded via telephone connection which accommodates remote monitoring of salmon escapement information into this system.

Operation over multiple years is necessary to calibrate the method with existing escapement estimates collected via streamwalk surveys. If the method proves successful, the plan is to replace traditional streamwalk surveys with resistivity counter monitoring on a long term basis. Long-term operation will be funded through existing Aboriginal Fisheries Strategy funding, providing a legacy of more accurate data and cost savings.


Size Selective Mortality and Early Marine Growth: Potential Mechanisms Regulating Salmon

Our goal is to address the Fraser River Panel Priority #2, the examination of mechanisms affecting early survival of Fraser River Sockeye Salmon, as early marine life is expected to set recruitment dynamic patterns of Pacific salmon. In this two-year project, we propose to examine the factors influencing the size of Fraser Sockeye during their first year at sea, a hypothesized critical time in determining their survival, given that fish must be large enough to avoid predators and have sufficient reserves to survive their first winter (Beamish and Mahnken 2001). Currently, there is no consensus on the importance of size-selective mortality and compensatory growth as mechanisms regulating the mortality and abundance of Fraser River Sockeye Salmon.

We propose retrospective and comparative analyses of growth characteristics derived from the scales of two Fraser River stocks demonstrating contrasting patterns of freshwater and marine residence and, importantly, opposite trends in adult returns. Over the last decade Harrison (sea type) has had a high number of adult returns contrary to Chilko (lake type) Sockeye Salmon returns, which have been low. These stocks differ in their life-history in that Harrison fry outmigrate to sea ~ 2 months after Chilko smolts (Beamish et al. 2016).

Our goals are to: (a) evaluate the extent of size-selective mortality, (b) determine the factors influencing juvenile length at the end of their first year at sea, and (c) determine the factors influencing the number of returning adults.

Estimation of Fraser River – South Thompson Age 0.3 Chinook Aggregate Escapement

The goal of the project is to estimate the spawning escapement of the Fraser River – South Thompson age 0.3 aggregate (ST0.3A Chinook). The ST0.3A escapement will be estimated using Coded Wire Tags (CWT), Genetic Stock Identification (GSI), and CWT exploitation rate indicator stock data from escapement and Fraser River fisheries. To achieve this objective, we will increase recovery of CWTs from Chinook carcasses in the Lower Shuswap River; conduct a high-precision mark-recapture project and CWT sampling in the Middle Shuswap River; collect age samples across the South Thompson watershed; produce a CWT release group of Middle Shuswap River smolts (to augment the Lower Shuswap indicator stock); and analyze GSI and age data from the Albion Test Fishery.


Taku River Canadian Fishery Sampling & Stock Assessment

Data acquired through the Lower Taku River commercial and assessment fisheries are vital elements of the Taku River fishery management and stock assessment programs. Sampling involves the inspection for and recovery of coded-wire tag (CWT) information from Chinook and coho salmon which is used in the estimation of smolt production, the inspection for and recovery of spaghetti tags from Chinook, sockeye, and coho to support abundance metrics, the collection of otoliths from sockeye to estimate contributions of enhanced sockeye salmon, and the collection of age, sex, and length samples from Chinook, sockeye and coho salmon caught in the fisheries. These baseline stock assessment data are used for stock recruitment analyses, preseason forecasting programs for Chinook and sockeye salmon, and monitoring stock health.


Stikine Fishery Sampling & Stock Assessment

Data acquired through sampling of the Lower Stikine River Canadian commercial and assessment fisheries are central elements of the Stikine River fishery management and stock assessment programs. Sampling involves the inspection for and recovery of coded-wire tag (CWT) information which is used in the estimation of smolt production of Chinook and coho salmon, the inspection for and recovery of spaghetti tags from Chinook to support abundance metrics, the collection of otoliths from sockeye to estimate contributions of enhanced sockeye salmon, the collection of egg diameter data to determine the contribution of Tahltan Lake sockeye salmon, and the collection of age, sex, and length samples from Chinook, sockeye and coho salmon caught in the fisheries. These baseline stock assessment data are used for stock recruitment analyses, preseason forecasting programs for Chinook and sockeye salmon, and monitoring stock health.

Origins of Chinook Salmon Harvested in Southeast Alaska Fisheries

U.S. fisheries in Southeast Alaska (SEAK) harvest stocks of Chinook salmon bound for river systems in Alaska, Canada, and the continental U.S. Thus, fisheries in SEAK are managed under the purview of the Pacific Salmon Treaty (PST), in which an abundance-based management framework is used for Chinook fisheries. This requires management to have access to reliable information on stock-specific catch, escapement, and recruitment to forecast indices of abundance in PST fisheries.

This project aims to improve fishery management and provide independent estimates of stock composition in commercial troll and sport Chinook salmon fisheries in Southeast Alaska. Further, the project will take the analysis beyond basic estimation of stock composition by combining genetic assignment of individuals from selected stocks and fisheries with their associated age and mark information to provide additional information about Chinook salmon in SEAK fisheries for Chinook Technical Committee needs. This type of information has been used to measure the effectiveness of management actions in SEAK as well as to contribute to applications outside of SEAK (e.g. estimating age-specific terminal returns of stock groups and forecasting returning run sizes). This project is an integral part of a larger SEAK genetic stock identification program for Chinook salmon, which includes comprehensive coverage of major gillnet, troll, and sport fisheries.


Stikine – Tahltan Lake Adult Sockeye Enumeration

The Tahltan Lake weir project monitors sockeye salmon escapement in the most important Stikine River sockeye spawning Lake. In 1993, the Transboundary Technical Committee (TTC) established an escapement goal of 24,000 fish for the Tahltan stock, which takes into account an escapement of 20,000 naturally spawning fish and up to 4,000 fish needed for broodstock to meet objectives of the Canada/U.S. Stikine River enhancement program. When coupled with stock identification techniques, an accurate count of Tahltan Lake sockeye permits estimation of escapement drainage-wide.

It is the primary tool for identifying whether or not both Tahltan Lake and Stikine River mainstem escapement goals have been achieved. Tahltan Lake counts are used to forecast future adult sockeye salmon production and will guide management actions in subsequent years through abundance based management. Data gathered through this project is also used to determine appropriate egg-take levels at Tahltan Lake designed to boost adult production in the Stikine River through the joint Transboundary sockeye enhancement program.

Southeast Alaska Coastal Monitoring

Alaska stocks of pink (Oncorhynchus gorbuscha) and Chinook salmon (O. tshawytscha) spend large portions of their life histories in marine waters within the U.S. Exclusive Economic Zone (EEZ) and beyond the 200-mile EEZ of the coastal States. However, the strength of salmon year-classes is often set during the early overwintering phases of immatures or during the nearshore seaward migration phase of juveniles. Thus, the Alaska Fisheries Science Center (AFSC), Auke Bay Laboratories (ABL) initiated the Southeast Alaska Coastal Monitoring (SECM) project in 1997 to better understand the effects of climate and near-shore Ocean conditions on year-class strength of salmon and ecologically-related species. This research in turn provides improved information for resource management of salmon in the Pacific Salmon Treaty (PST) northern boundary. In particular SECM data provides a forecast index for northern southeast Alaska (SEAK) Transboundary River Chinook salmon returns, an annual pink salmon abundance forecast, and long term environmental and population data that are used by harvest managers in the PST northern boundary, which includes PST Chapter 2 pink salmon treaty issues in districts 101, 102, 103, and 104.