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Between October 8, 2001 and February 22, 2002, panelists representing different perspectives from Alaska, British Columbia, and Washington were available to answer students' questions related to salmon biology on the Salmon Summit Web site. In selecting participants for the Salmon Summit panel, we tried to choose panelists with different opinions and different backgrounds. The opinions expressed by the panelists were their own. They may not agree with those of other panelists, and do not necessarily reflect the opinions of 7th Floor Media.
The panelists are not currently online. However, you will find the questions submitted by the students and the responses received from the panelists, below.
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| Q - How fast do salmon reproduce? | | Q - What kinds of diseases do salmon get?
Which one is the worst? | | Q - When we were dissecting our salmon we found out that Alaska salmon have a certain fungus on their tongues. Why don't Canadian salmon have the same fungus? | | Q - What are some of the main rivers besides the Yukon and The Kuskokwin that are major salmon spawning rivers. | | Q - How many rivers are there in Vancover that have salmon in them? | | Q - Why do some people think that hatchery salmon may threaten the strength of wild stocks? | | Q - Do salmon care whose eggs they lay milt on, or whose milt goes on their eggs? | | | Q - How fast do salmon reproduce? | |
A - The question is a little vague. Does it mean how fast does the act of reproduction take, or how fast can they get to the spawning grounds once they start their migration, or how many years does it take before fish are mature and ready to spawn? I'll answer the first one but can answer all of them if you like.
How fast is the act of spawning?
It's somewhat different for each species of salmon. In terms of sockeye salmon, once males and females arrive on the spawning grounds, females start to select spawning areas, and compete for them with other females, while males hang out and wait. Once a female has selected a site, the males start to compete amongst themselves to hang out near her in anticipation of her releasing her eggs into her redd, so that they can release their sperm. These behavioural acts and competition can extend for a period of just a couple days to a couple weeks. After spawning, the female tends to hang around the redd and usually dies a week or so later. The males may try to spawn with another female but also will die within another week. Within a month, most of a spawning is finished within any given spawning area.
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Scott Hinch
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A - Salmon reproduce themselves on cycles ranging from 2 to about 6 years, depending on the species. This is the total time period from when parents spawn until the next generation returns from the ocean. However, the number of returning salmon that one spawning pair produces varies greatly depending on several factors including: how many total salmon spawn in a stream, the quality of the habitat, and the percentage of young sea-going salmon (smolts) that survive in the ocean.
Coho salmon is a good example. As the total number of spawners decreases, the number of smolts and adult offspring that a pair of spawners produces increases up to a point because competition for space and food among young salmon in the stream is reduced, so that they grow faster and a higher percentage survive to enter the sea as smolts. The quality of habitat affects survival which also affects the rate at which salmon reproduce (as well as the total number of salmon a stream can support).
Our best estimate for coho salmon in good habitat in Southeast Alaska is that if there were very few spawners in a stream, a pair would produce about 190 smolts entering the ocean. If about 10% survive in the sea, which is a typical long-term average for coho salmon, there would be 19 returning adults. However, the number of returning adults could be only 6 if only 3% of smolts survive in the ocean or as many as 57 if 30% survive. These are estimates of the "maximum" rate at which we believe typical Southeast Alaska coho salmon could reproduce if very few were were allowed to spawn, resulting in very little competition among fry in the stream. However, if no fishing were allowed and all returning salmon were allowed to spawn, two spawners would just replace themselves, on average.
One job of fishery biologists is to estimate the number of spawners that, on average, produces the greatest surplus of adult salmon for harvest. These estimates are used to set biological escapement goals for fishery managers. For a typical coho salmon population in Southeast Alaska, we estimate that the maximum number of adult salmon will be available for harvest when the total number of spawners is such that about 80-90 smolts are produced by a pair. Under average marine survival conditions (10% survival rate), this would equal about eight returning adults per spawning pair which would allow six (75% of the returning run) to be harvested (this is probably as close as I'll get to a single direct answer to your question). However, in year when survival of smolts in the ocean is only 4%, a pair would produce only 3 or 4 returning adults, and the harvest would have to be limited to only about 1/3rd to half of the returning run in order to meet the escapement goal. You can see that natural survival of salmon in the ocean is one of the main things that fishery managers have to consider in determining the rate at which salmon have reproduced so they can do a good job managing salmon fisheries. Also, I should point out that some species and stocks are not as productive as Southeast Alaska coho, so that a pair of spawners might only produce perhaps four returning adults under average conditions, instead of eight.
Finally, I should point out that spawners are not only important because they directly produce the next generation. After they die, their carcasses add nutrients to the stream which contribute to the food chain that supports future generations of salmon, particularly species like coho that remain and feed in the stream for a year or more.
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Leon Shaul
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A - Salmon reproduction is really interesting! I'll outline the several steps in the process for you:
(1) when they return to rivers and streams, parents spawn in nests (called "redds") that the female digs in the gravel,
(2) her fertilized eggs incubate for a couple of months before they hatch (the colder the water, the longer it takes),
(3) as they use up the rich food they carry in their yolk sacs, the little fry wiggle up through the gravel into shallow areas where they begin to exercise in the current, learn to feed on their own and hide so they aren't eaten by other fish, birds, or other animals,
(4) depending on the species, the young salmon may live in freshwater for just a short time or as many as several years,
(5) as the juvenile fish get ready to head downstream to the ocean, their bodies change to be able to survive in saltwater (they become what are called "smolts" - this transition is really cool!),
(6) once in the ocean, they migrate long distances, feeding on all sorts of different things that allow them to grow very large, and finally... they return to the streams where they were born to become parents themselves. This whole cycle of life can take just a couple of years or can be two or three times as long, depending on the species.
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Steven Leider
| | |  | | Q - What kinds of diseases do salmon get?
Which one is the worst? | |
A - Salmon can get many types of diseases, both in salt and fresh water. Parasite, viral, and bacterial infestations are common and can be dangerous for many salmon species. Here are a few diseases common in Alaska:
Whirling Disease - parasites that cause young salmon to swim in a circle. They cause damage to soft tissue in fish.
Tapioca Disease - a parasite that creates small white cysts in the meat of fish. It looks like small white balls under the skin of salmon.
IHN - Infectious haematipoietic necrosis - a viral disease that is characterized by a sudden rise in mortality especially in young fish.
BKD - Bacterial kidney disease - a bacteria infection that causes kidney, spleen and liver lesions.
Both IHN and BKD are very dangerous diseases.
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Scott Walker
| | | | | Q - When we were dissecting our salmon we found out that Alaska salmon have a certain fungus on their tongues. Why don't Canadian salmon have the same fungus? | |
A - I have no idea about this one. I talked to our disease and fungus expert and he had never heard of this one before. He has also been asked this question two times previously. Your questions have been making the rounds of my co-workers.
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Scott Walker
| | | | | Q - What are some of the main rivers besides the Yukon and The Kuskokwin that are major salmon spawning rivers. | |
A - Hundreds of rivers in Alaska are major producers of Salmon. Hundreds of rivers in Alaska are major producers of Salmon. The following rivers are mentioned due to their size in area and drainage. In Southeast Alaska major rivers include: Unuk River, Stikine River, Taku River, Chilkat River and the Chilkoot River. Major rivers in Southcentral Alaska Include: Susitna River, Knik River and the Copper River. In Southwest Alaska along with the Kuskowkim River is the Kvichak River.
The Alaska Department of Fish and Game has a stream catalog that currently contains around 15,000 streams, rivers or lakes around the state which have been specified as being important for the spawning, rearing or migration of salmon. It is believed that this number represents less than 50% of the streams, rivers and lakes actually used by salmon species.
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Scott Walker
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A - Some of the other major salmon rivers include (to name just a few of the most important by region):
Russia: Kamchatka, Ozernaya
Western Alaska: Kvichak, Wood, Egegik, Ugashik, Chignik, Karluk
Cook Inlet: Kenai, Kasilof, Susitna
Prince William Sound: Copper River
Southeast Alaska: Chilkat, Situk
Transboundary: flowing from B.C. through Alaska: Taku
Northern B.C.: Nass, Skeena
Southern B.C.: Fraser
Washington, Oregon, Idaho: Columbia
California: Klamath, Sacramento
I should also mention that some regions, like Southeast Alaska have few large salmon rivers but thousands of small streams flowing directly into the sea that collectively produce millions of salmon.
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Leon Shaul
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A - The Fraser River is the single largest producer of wild salmon in BC and indeed Canada.
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Scott Hinch
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A - In Washington, the biggest river by far is the Columbia, encompassing an area the size of France. Although some areas were blocked from access by spawning salmon when large hydroelectric dams were built, this is still the largest basin (containing a network of many rivers and streams) for salmon spawning in the state. There are also many, many smaller, but important salmon spawning rivers in Puget Sound and along the Washington Coast. In Puget Sound these include the Skagit and Snohomish rivers, and along the coast the Chehalis system.
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Steven Leider
| | | | | Q - How many rivers are there in Vancover that have salmon in them? | |
A - Within the city of Vancouver (not including any of the other adjacent municipalities) there is only one stream where you can find wild salmon. This is Musqueam Creek which drains southward out of the University Endowment Lands and through the Musqueam Reserve into the Fraser River. Wild chum and coho salmon have been observed there (although there has been some artificial enhancement of these species over the past few years). Wild cutthroat trout are relatively abundant and some of these may be resident year round in the stream and others may spend some of their life in the ocean before returning to spawn (just like chum and coho). There has been some recent attempts to rehabilitate a stream which drains northward out of the Endowment Lands into English Bay. This Spanish Banks Stream has had habitat created where there was none and chum and coho salmon stocked. Perhaps one day this stream will again produce wild salmon.
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Scott Hinch
| | | | | Q - Why do some people think that hatchery salmon may threaten the strength of wild stocks? | |
A - There are a number of potential problems for wild stocks: loss of genetic fitness because of interbreeding with hatchery fish, competition with hatchery fish, over-fishing by fisheries targeting hatchery fish, and disease transfer.
The hatchery environment is very different than the stream environment, which can result in rapid genetic changes in hatchery fish so they can grow and survive better under conditions in the hatchery environment. The effect is greatest in species like coho salmon that spend a lot of time as juveniles in freshwater. Wild juvenile coho salmon exhibit aggressive, territorial behavior that helps them survive and grow in the wild but does not serve them well in hatchery rearing tanks where fish have to remain in close contact and don't have to compete much for food. They become "domesticated" which means they become dependent on the hatchery and less able to survive in the wild. This becomes a problem in cases in which a lot of the salmon reared in the hatchery do not return there, but "stray" into wild systems, interbreed with wild fish and reduce the fitness of the wild population (i.e. its ability to survive).
Hatchery fish compete for food with wild fish and can also attract predators that also feed on wild fish, at times when hatchery fish are not as available. If fisheries are managed primarily to harvest hatchery salmon, it can result in over-fishing of wild stocks.
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Leon Shaul
| | | | | Q - Do salmon care whose eggs they lay milt on, or whose milt goes on their eggs? | |
A - Basically it's the males that decide where the milt gets deposited. Dominant males who are courting individual females will deposit milt on her eggs the moment she releases them. However, in some situations, smaller sub-dominant males, who have been fighting with the dominant ones, and even small sneaker males (these may be a year younger - termed 'Jacks', and have been lurking off in the distance) will all rush in the moment the female lays her eggs. At this point, there can be a flurry of activity in the nest with milt being deposited by any or all of these males. Generally, the dominant males fertilize most of the eggs, but not always. In some cases all of the males have some degree of success. There is some evidence that the strategies of the sneakers and others are inherited, so it may not be surprising that all of the males have a certain degree of success sometimes at fertilizing eggs.
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Scott Hinch
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A - Salmon do pair up, male and female, around the nest during mating. The males are territorial and from my observations, males in pairs are usually full sized fish that can defend their place by the nest and are also apparently acceptable to the female. However, in most species there are also small males that have been growing in the sea for a shorter period (usually called jacks) and in some cases have never gone to sea (called precocious parr). These small males usually do not pair up with a female, but remain as near the nest as they can and dart in and attempt to fertilize eggs when the pair are actively spawning.
Also, in many streams two or more species are spawning in the same area at once. We sometimes find hybrids of two species (a common cross that I've seen is the pink-chum cross, sometimes called chumpies). Salmon appear to try to mate with their own species, but in cases where the species are mixed together and actively spawning at the same time, these hybrids seem to indicate that cross fertilization sometimes occurs when milt of one species contacts eggs of another.
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Leon Shaul
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