The Salmon Food Chain
06/11/22 10:58
Salmon are part of a complex food web.
Western Red Cedar trees extend roots into nutrient-rich soil along river banks enriched by the decomposition of salmon that ended their life cycle on the spawning grounds.
As they returned from the ocean to the rivers of their origin, the migrating salmon nourished black bears, grizzly bears, eagles, ringed kingfishers, otters, seals, sea lions, orcas, and people.
Whether for food or for sport, people account for an awful lot of salmon taken from the ocean and rivers.
There was a time when salmon was abundant; rivers and streams filled with them in late summer and autumn.
These days, salmon runs are only a fraction of what they once were.
A thriving salmon population comprises an essential part of a healthy food chain, and the fish gain much of their mass in the Pacific Ocean.
Researchers with the University of British Columbia Institute for the Oceans and Fisheries are mapping the food web in coastal waters, such as the Salish Sea, and out in the North Pacific.
Dr. Genyffer Troina says they leave rivers for the coast and then out to oceanic waters to feed and grow.
Dr. Troina is studying stable isotopes and fatty acids, which help her determine the position of salmon in the food web.
She says preliminary analysis of samples caught in the pacific show examples of salmon prey now consuming species the salmon normally eat.
It may indicate they are shifting to a higher position in the food chain and becoming competitors.
However, she says more analysis is needed to know what they are eating, whether they share the same region, and would be competitors with salmon for prey.
Salmon that lack proper nutrition may be too slow to escape predators, more prone to diseases, less likely to reach their spawning rivers, and produce eggs that are not as healthy.
Studying the interaction of predators and prey in the North Pacific can help better understand how salmon are affected by ocean temperatures, heat waves, and other problems related to climate change that deplete prey or make it less nutritious.
Troina says as they took samples farther south, there were fewer salmon.
“What I saw when I was in the field collecting samples was interesting, that as we moved south we could see that the dominance of species changed, and we saw that it was a reflection of how much salmon we caught.”
She says they would see a lot of jellyfish, very few salmon, or dominance of other fish, while in other places with a different water temperature there was a greater diversity of species.
In these areas of higher diversity, Troina says there were a lot of squids, small fish that could be prey or could be competing with salmon, a lot of salmon, shrimp, and krill, but not many jellyfish.
“We saw this difference in space, and we want to look at this in terms of how it is affecting the food web, and also how it is associated with water temperature.”
Closer to shore, Ph.D. candidate Jacob Lerner studies the food web of coastal BC, particularly as it relates to Chinook salmon.
“A lot of my personal research has been investigating the pelagic food webs and understanding the connections from the base of the food web, plant matter, the phytoplankton, up to the large chinook salmon and onwards, understanding what is eating what, where everything fits in.”
Lerner says they are finding the coastal food web is alot more discrete than expected.
“The food web in the Strait of Georgia, the food web in Queen Charlotte Sound, and Juan de Fuca Strait, they’re all different and they’re very specifically based on the primary production at the base of the food web, so the amount of phytoplankton, this plant matter at the base of the food web that is there.”
Lerner says the food webs are all different but are generally healthy.
He says they found no evidence of rising water temperatures affecting the food chain of coastal BC, but global warming is always a concern.
Lerner says during the heatwave experienced by coastal Alaska in the mid-2000s, there was evidence prolonged heat led to a mini-collapse at the bottom of the food chain.
“This cascaded up to poor health in the species in the higher positions in the food web, like the small fish, and large fish, we don’t see that currently in BC. That’s always of concern, prolonged heat waves and warmer weather, but currently, we haven’t seen anything like that we just see discrete and variable food webs across the BC Coast.”
Lerner says one difference they are looking at is the fat content in Chinook salmon, with higher amounts of lipids found in those that require more energy to reach spawning grounds hundreds of kilometres away from the coast.
The Chinook with higher energy and speed is feeding in a different region.
Lerner says the most nutritious Chinook feeding Southern Resident orcas, or ending up on the tables of coast communities may be coming from the north coast or the Gulf of Alaska.
He says something important to understand is this input of energy from marine food webs is not present in BC.
Lerner says the next step is to determine how these different regional food webs drive the energy stimulation in Chinook salmon.
“The regions are different, and we know that the Chinook in the region accumulate different amounts of energy. The question is, is the function of the marine food web feeding it, is that where the high energy Chinook stocks are getting their high lipid content, the high-fat content from, or is it just a function of their biology.”
He believes answering that question will help create a more refined approach to salmon management.
Dr. Troina says there is a need to have a greater understanding of the food webs that are part of the life cycle of salmon.
She says the high seas are one part of the life cycle, “where they are going to feed and grow and then come back to lay their eggs, so this is a very important part of the life cycle and we don’t know what is happening there.”
Dr. Troina says what happens in the North Pacific defines how much salmon will return, and knowing what is going on will help find ways to manage salmon and other species throughout the whole food web.
Western Red Cedar trees extend roots into nutrient-rich soil along river banks enriched by the decomposition of salmon that ended their life cycle on the spawning grounds.
As they returned from the ocean to the rivers of their origin, the migrating salmon nourished black bears, grizzly bears, eagles, ringed kingfishers, otters, seals, sea lions, orcas, and people.
Whether for food or for sport, people account for an awful lot of salmon taken from the ocean and rivers.
There was a time when salmon was abundant; rivers and streams filled with them in late summer and autumn.
These days, salmon runs are only a fraction of what they once were.
A thriving salmon population comprises an essential part of a healthy food chain, and the fish gain much of their mass in the Pacific Ocean.
Researchers with the University of British Columbia Institute for the Oceans and Fisheries are mapping the food web in coastal waters, such as the Salish Sea, and out in the North Pacific.
Dr. Genyffer Troina says they leave rivers for the coast and then out to oceanic waters to feed and grow.
Dr. Troina is studying stable isotopes and fatty acids, which help her determine the position of salmon in the food web.
She says preliminary analysis of samples caught in the pacific show examples of salmon prey now consuming species the salmon normally eat.
It may indicate they are shifting to a higher position in the food chain and becoming competitors.
However, she says more analysis is needed to know what they are eating, whether they share the same region, and would be competitors with salmon for prey.
Salmon that lack proper nutrition may be too slow to escape predators, more prone to diseases, less likely to reach their spawning rivers, and produce eggs that are not as healthy.
Studying the interaction of predators and prey in the North Pacific can help better understand how salmon are affected by ocean temperatures, heat waves, and other problems related to climate change that deplete prey or make it less nutritious.
Troina says as they took samples farther south, there were fewer salmon.
“What I saw when I was in the field collecting samples was interesting, that as we moved south we could see that the dominance of species changed, and we saw that it was a reflection of how much salmon we caught.”
She says they would see a lot of jellyfish, very few salmon, or dominance of other fish, while in other places with a different water temperature there was a greater diversity of species.
In these areas of higher diversity, Troina says there were a lot of squids, small fish that could be prey or could be competing with salmon, a lot of salmon, shrimp, and krill, but not many jellyfish.
“We saw this difference in space, and we want to look at this in terms of how it is affecting the food web, and also how it is associated with water temperature.”
Closer to shore, Ph.D. candidate Jacob Lerner studies the food web of coastal BC, particularly as it relates to Chinook salmon.
“A lot of my personal research has been investigating the pelagic food webs and understanding the connections from the base of the food web, plant matter, the phytoplankton, up to the large chinook salmon and onwards, understanding what is eating what, where everything fits in.”
Lerner says they are finding the coastal food web is alot more discrete than expected.
“The food web in the Strait of Georgia, the food web in Queen Charlotte Sound, and Juan de Fuca Strait, they’re all different and they’re very specifically based on the primary production at the base of the food web, so the amount of phytoplankton, this plant matter at the base of the food web that is there.”
Lerner says the food webs are all different but are generally healthy.
He says they found no evidence of rising water temperatures affecting the food chain of coastal BC, but global warming is always a concern.
Lerner says during the heatwave experienced by coastal Alaska in the mid-2000s, there was evidence prolonged heat led to a mini-collapse at the bottom of the food chain.
“This cascaded up to poor health in the species in the higher positions in the food web, like the small fish, and large fish, we don’t see that currently in BC. That’s always of concern, prolonged heat waves and warmer weather, but currently, we haven’t seen anything like that we just see discrete and variable food webs across the BC Coast.”
Lerner says one difference they are looking at is the fat content in Chinook salmon, with higher amounts of lipids found in those that require more energy to reach spawning grounds hundreds of kilometres away from the coast.
The Chinook with higher energy and speed is feeding in a different region.
Lerner says the most nutritious Chinook feeding Southern Resident orcas, or ending up on the tables of coast communities may be coming from the north coast or the Gulf of Alaska.
He says something important to understand is this input of energy from marine food webs is not present in BC.
Lerner says the next step is to determine how these different regional food webs drive the energy stimulation in Chinook salmon.
“The regions are different, and we know that the Chinook in the region accumulate different amounts of energy. The question is, is the function of the marine food web feeding it, is that where the high energy Chinook stocks are getting their high lipid content, the high-fat content from, or is it just a function of their biology.”
He believes answering that question will help create a more refined approach to salmon management.
Dr. Troina says there is a need to have a greater understanding of the food webs that are part of the life cycle of salmon.
She says the high seas are one part of the life cycle, “where they are going to feed and grow and then come back to lay their eggs, so this is a very important part of the life cycle and we don’t know what is happening there.”
Dr. Troina says what happens in the North Pacific defines how much salmon will return, and knowing what is going on will help find ways to manage salmon and other species throughout the whole food web.