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PRESENT & PAST ISSUES
Fukushima: Are Yukon salmon radioactive?
Fukushima was a nuclear power plant in Japan. Following an earthquake and the resulting tsunami in March 2011, the plant has been leaking radiation into the ocean. This has raised concern for our salmon and if they are still safe to eat.
Integrated Fukushima Ocean Radionuclide Monitoring (InFORM) is a network of people from a variety of agencies and Universities and includes citizen scientists. They assess radiological risk to Canada’s west coast and share the information on their website (https://fukushimainform.ca/). They are confident that Fukushima radiation levels do not pose a risk to either humans or the ecosystems of Western Canada.
Health Canada’s analysis found that natural radiation was much higher than radiation from Fukushima. Fukushima radiation is typically below the detection level. Alsek Sockeye (2015 to 2017, 29 samples), Yukon River Chinook (2015 & 2016, 20 samples), Yukon River Chum (2015 to 2017, 30 samples), and Porcupine Chum (2017, 10 samples) were tested for radiation. Most samples showed no detectable Fukushima radiation but 1 Yukon River Chum and 2 Alsek Sockeye samples had just detectable levels of non-natural radiation.
Over-escapment: Is there such a thing?
Over-escapement is described as having more salmon spawn than is required to meet the fisheries management goal. It may result in fewer offspring per spawning adult but it might be necessary to conserve salmon biodiversity and promote re-colonization of habitats.
Support for the concept of over-escapement is usually a result of the Ricker stock-recruitment curve, which estimates the maximum sustainable yield (MSY) of a discreet population of fish. However, this overly simplistic model only accounts for harvest considerations and does not consider how spawners affect the broader ecosystem. Scientists found a deficiency of marine derived nutrients (nutrients from salmon) in north western U.S. freshwater systems from diminished salmon returns, with a decrease of more than 90% of some nutrients. Scientists encourage fishery managers to consider salmon as important contributors of nutrients to increase the habitat productivity of streams. The enriched habitat sustains the production of invertebrates, other fish and species of birds and mammals that consume returning adult salmon. The carcasses release nutrients which feed invertebrates and results in fatter juvenile salmon more capable of overwintering and contributing to stock production of wild Chinook salmon.
Several scientific papers support the idea that over-escapement does not have a negative long term effect on salmon populations. Scientists found a decrease in offspring at high spawning escapements but no evidence that over-escapement led to a collapse or near-collapse of salmon populations. In addition, Scientists considered that positive effects existed from having a large number of spawners, including that high numbers of spawning salmon encourage them to explore new habitats, which can result in re-colonizing extirpated populations or creating new populations.
Prior to fishery management, salmon persisted through ice ages, volcanoes, and river changes. Salmon faced difficult times, but they adapted and survived both gradual and rapid stresses. It is believed that a highly variable life history, including straying of spawners during periods of high abundance, are some of the reasons they were able to adapt and survive.
Catch and release of salmon
Salmon may be released to allow an angler to capture and keep a larger fish. Some anglers only catch and release fish. The effects of catch and release to fish will vary. The effects will depend on the angler’s skill in landing, handling and releasing it. A strong, healthy fish will be better able to withstand additional stress than a fish in poor condition. The effect will be greater when fish are already stressed from environmental conditions such as warm water temperatures. When a fish is captured and released more than one time the effects will be cumulative.
Commercial Fishing Along the Yukon River
Commercial salmon fisheries in Alaska target summer and fall chum. The commercial Chinook fishery fell by about 50% in 1998 and has not recovered since. Catches since 2008 have been very small. The Canadian commercial fishery is centered in the Dawson area, with a smaller fishery in the Minto area. Fall chum are targeted. Catches have been low since the closure of the Han Fisheries plant and associated roe market in 1997. The Chinook fishery was reduced to less than 50% in 1997 and has either been closed or has had very low captures since.
Definitions of Subsistence fisheries
The US has a complicated subsistence system. Alaska defines subsistence as “…non-commercial, customary and traditional uses of wild, renewable resources…for direct personal or family consumption as food, shelter, clothing, tools, or transportation…”. The fish captured may be used for customary trade or barter. Except where specifically exempted, it is open to all Alaskans outside of the non-subsistence areas. The federal government can over-ride the state on federal lands. In Canada the subsistence fishery is almost exclusively the First Nation fishery. Salmon may be caught for food, cultural and ceremonial purposes and for trade with other First Nations.
Net size restrictions
This generally refers to the net mesh size. Mesh sizes are selective. A larger mesh catches larger fish, and a small mesh captures smaller fish. Smaller fish can swim, or struggle, through larger mesh. Large salmon are less likely to be gilled in the small mesh net. Restricting net mesh to smaller sizes allows a greater portion of the largest salmon to successfully migrate to spawning grounds. These include the large, egg-rich females. However, there is a concern that the salmon most likely to be captured in any regulated net size will be selectively removed from the spawning population.
Quality of escapement
Harvest sharing and border escapement objectives are based on numbers of adult salmon. There is no consideration of sex, size or age composition. The average size and age of Yukon River Chinook has changed. This is probably a result of decades of size and sex selective fisheries. Quality of escapement includes the health of the individual salmon. Rising river temperatures may cause direct effects to fish health. It may also increase the rate of infection and virulence of diseases and parasites. The health of salmon that have struggled free of nets may also be effected.
Perspectives on Escapement
There are different perspectives on salmon escapements. Perspectives of managers are based on estimates of the total number of salmon entering the river and then the cross border escapement to Canada. The estimates are used to make decisions on openings for the fisheries. Fisher’s perspectives will mainly be based on the number and condition of the salmon they catch. Their perspectives may also be based on long term local experience and oral tradition. This may include periods of abundance and scarcity. This may cause a difference in perception of escapement between managers and fishers.
The fishery manager’s perspective of escapement may be based on achieving the greatest number of returning adults from the lowest numbers of fish allowed to spawn (maximum sustainable yield). They do this from estimates of salmon spawning and calculations of how many salmon will be produced from each salmon that spawns. Generally, lower numbers of spawners produce more adults than very high numbers of spawners. However environmental conditions and ecosystem needs are not considered. Fishers’ perspective of escapement is usually based on having sufficient spawners to ensure the safety of the salmon run and the fishery under all environmental conditions.
The Salmon Sub-Committee has taken action on a variety of issues over the past several years to ensure that salmon resources are preserved for future generations. Some key accomplishments follow: