Each year, Fraser River sockeye enter the Fraser River to spawn between July and September. Until recently, the Late run sockeye pooled off the mouth of the Fraser River for three to six weeks before entering the river.

In the past several years, a large portion of these sockeye salmon have died during in-river migration to their spawning areas. Estimates of the number of fish dying prior to reaching the spawning areas have dramatically increased since 1995. In 2000 and 2001, there was approximately 90 per cent mortality of potential spawners, with only about 10 per cent of this stock successfully reaching the spawning grounds. Fisheries and Oceans Canada is extremely concerned about the Late run Fraser River sockeye stock because of these low survival numbers.

High fish mortality results from the early migration pattern of sockeye into the Fraser River. However, the exact cause(s) of the early migration are thus far unknown.

Fisheries and Oceans Canada and the Pacific Salmon Commission sponsored a number of research projects in 2001 and 2002. The research is designed to better understand the migratory behaviour and the associated mortality as well as to identify the cause(s) of the phenomena. A tagging study is being conducted to track fish migration. Assessments of the effects of water quality, ocean conditions, physiology, contaminants, fish disease, and enhancement projects are also underway. Although no answers to the early migration behaviour have been found, the scientists involved in the studies now have a clearer picture of the overall problem.

Tagging Studies

Fisheries and Oceans Canada (DFO), in conjunction with the Pacific Salmon Commission, is conducting an internationally funded tagging study on migrating Fraser River sockeye. The objective of this study is to obtain information on the migration timing and survival of Late run sockeye.

Radio transmitters have been inserted into the stomach of about 1,000 sockeye in marine and freshwater areas. Radio-tagged fish have a thin wire antenna protruding from the mouth and an external, orange spaghetti-shaped cinch tag attached behind the dorsal fin. These fish are tracked as they enter the Fraser River and throughout the watershed as they migrate toward their spawning grounds. To date, about 400 sockeye have been tracked en-route to their spawning grounds.

Differences in timing between Late run and other sockeye stocks are evident based on tagging results. Late run fish have taken two to three weeks longer to reach spawning grounds than other sockeye stocks, which indicates that some delay occurred before entering the river. In the past few years, Late run sockeye were migrating at about the same time as other sockeye stocks. In 2002, some Late run sockeye entered the Fraser River early, however to date no evidence of mortality prior to spawning is apparent.

Please notify Fisheries and Oceans Canada if a fish with an external orange spaghetti tag and a radio tag in the stomach is seen or caught. Remove the radio tag and the spaghetti tag and contact DFO immediately. In the Lower Mainland, call (604) 666-8833 or in the BC Interior (Kamloops), call (250) 851-7705. Individuals returning radio tags to DFO, along with information on time and place of capture, will be sent the complete tracking history of the fish and a small token of appreciation for participating in the study. The information obtained through the returned tags will directly contribute to improved management and conservation of Fraser River sockeye.

Fisheries and Oceans Canada is also conducting a tagging program in the Thompson River to assess the success of migration and spawning of Adams River and Lower Shuswap sockeye. External disk tags have been attached to approximately 20,000 sockeye. Although these tags cannot be tracked, specially trained crews will collect tagged fish at the spawning grounds to obtain information. The public is asked not to remove any external disk tags from dead fish in order to ensure a successful completion of the study.

Fish Disease Study

A fish disease study is one avenue of research to explain the high mortality rates of Late run fish prior to spawning. A parasite called Parvicapsula, which affects the kidney of sockeye, has been identified as a source of mortality during migration. (This parasite does not have any known effect on human health.)

Warmer water temperatures may speed up the effects of Parvicapsula. As adult sockeye enter freshwater and prepare to spawn, their ability to fight off disease decreases. Research on fish disease will study the transmission and infection rates of Parvicapsula. The relationship between water temperature and the effects of Parvicapsula on migrating adult salmon is also being assessed.

Late Run Sockeye Physiology Study

To better understand the Late run mortality rates, a variety of physiological data will be collected from fish displaying normal and abnormal river entry behaviour. Differences in osmoregulatory ability (the ability to regulate the difference in density between salt water and freshwater), stress response, energy content and reproductive success will be assessed.

The cues responsible for triggering the osmoregulatory change from saltwater to freshwater may have been triggered too early, forcing early migrants into freshwater. Similarly, some unknown stress factor in the Strait of Georgia may also promote early river entry. Salmon do not feed after entering the Fraser River, so they complete their upstream migration and spawning with the energy reserves brought from the ocean. Recent scientific work has shown that this initial energy state is lower now than in previous years. Early entry may be a function of initial energy state, and therefore energy exhaustion is a plausible explanation for high pre-spawning mortality.

Studies are also being conducted on the reproduction of Late run Fraser River sockeye from different river-entry timing groups, to determine the connection between parental physiological conditions and offspring survival.

Oceanography Study

The collection of oceanographic data continues through 2002 to improve understanding of the effect of ocean conditions on fish behaviour and the water conditions encountered in the open ocean, on the west coast of Vancouver Island, and within Juan de Fuca and Johnstone straits. Climate changes that affect ocean conditions may have an effect on fish physiology or biological processes, which then influence the migration and distribution of the returning fish.

Preliminary findings indicate that there have been significant year-to-year differences in water properties and water distribution during the period of 1995-2000 compared to earlier years. Changes in the timing of other salmon species returning to the Strait of Georgia have also been reported. In addition, there have been changes in the behaviour and migration timing of salmon to other systems outside of the Strait of Georgia. This may support the hypothesis that these changes are linked to global climate-related processes. More research on ocean conditions will further test this hypothesis.

Contaminants Study

It may be possible that recent introductions of new chemicals into the Fraser River and Strait of Georgia are responsible for the abnormal behaviour of Late run sockeye. These fish may be susceptible to chemicals that can mimic or interfere with their normal reproductive development. Research continues through 2002 to determine if chemicals could directly or indirectly change the migration behaviour in salmon. For example, estrogen can mimic changing reproductive timing.

Enhancement Projects

Enhancement efforts are important for improving depressed sockeye stocks, such as Cultus Lake sockeye. Until the early migration of Late run Fraser River sockeye can be explained or resolved, or until the behaviour of these fish returns to normal, enhancement activities are being used to facilitate the maintenance of the wild stock. Without human intervention, stocks such as the Cultus Lake sockeye may become extinct.

The goal of fish culturing techniques is to obtain a relatively small, but genetically diverse, number of fertilized eggs that can then be nursed to maturity. It is recognized that cultured fish have a 50 per cent greater survival rate compared to fish reared in the natural environment. These kinds of stock recovery efforts seek to maintain the diversity of the stock, while increasing the number of returning spawners.

In 2002, an intensive enhancement initiative is being carried out on the Cultus Lake sockeye stock. As part of these enhancement efforts, tests are done to determine the optimal handling procedures, holding containers, water source and other treatment options that will maximize the survival rate to maturity for these fish. The timing of collection of broodstock, as well as the incubation, are also important factors in the success of enhancement projects that are being tested.

Once these research projects conclude and the information is analyzed, Fisheries and Oceans Canada will provide updates. In the meantime, the Department remains committed to meeting conservation goals for Late run Fraser River sockeye to ensure that a sustainable spawning population is maintained.

Contacts:

Alan Cass
Research Biologist
Fisheries and Oceans Canada, Pacific Region
(250) 756-7142

Wayne Saito
Cdn. Chair, Fraser River Panel
Fisheries and Oceans Canada, Pacific Region
(604) 666-3271