Salmon feed salmon?

Four salmon food groups

Last Thursday I presented to the Cohen Commission through the public forums process.

One of the key points I tried to make was that salmon represent a huge energy source. It’s an energy source that involves salmon acting as huge sponges to absorb energy from the North Pacific — growing from smolts to adults as they circulate the currents of the ocean.

That energy returns in the form of adult salmon and is deposited deep into the interior of BC — and wherever else salmon migrate to.

This energy can be tracked. There are certain isotopes of carbon (C) and nitrogen (N) that only come from marine/ocean sources: C13 and N15 . These isotopes are left behind all over the landscape as spawning adult salmon die, decompose and are eaten and then deposited through animal waste — and absorbed by plants.

You know the old saying when answering a questions in the affirmative: “does a bear shit in the woods?”

Well, yeah, it does… and if it’s been eating salmon that pile of poop has important nutrients in it for other critters.

Here’s a few of the slides:

In making reference to a few of the scientists that have been studying this; here’s a follow-up with some of the research that’s available readily online.

Fertilization of of terrestrial vegetation by spawning Pacific salmon_(Ben-David, et al. 1998)

Spawning Pacific salmon (Onchorhynchus) transport marine-derived nutrients into streams and rivers. Subsequently, these marine-derived nutrients are incorporated into freshwater and terrestrial food webs through decomposition and predation.

inbound salmon and outbound salmon (Fujiwara and Highsmith, 1997)

In essence, this study found that decomposing adult salmon carcasses added nutrients to estuaries that increased production of very small critters which are a key food source for chum fry.

I think this might be referred to as the ‘cycle of life’…

The energy and nutrients transported from the ocean by salmon can be released into aquatic environments such as streams, lakes, and estuaries through carcass decay. If the imported material is sufficient to substantially increase primary or secondary productivity of the systems, anadromous behavior of Pacific salmon can be viewed as an adaptation to provide increased food sources for their offspring.

salmon carcasses increase growth rate (Wipfli et al., 2003)

We tested the hypotheses that marine-derived resource subsidies (salmon carcasses) increase the growth rates of stream-resident salmonids in southeastern Alaska and that more carcasses translate into more growth […]

This study illustrates that marine nutrients and energy from salmon spawners increase growth rates of resident and anadromous salmonids in streams. This elevated growth should translate into increased survival and reproduction, ultimately elevating freshwater and marine salmon production.

Ecological relationships between salmon runs and aquatic community nutrition and productivity may be important considerations for salmon stock protection and restoration and for freshwater and marine ecosystem management.

Spawning pinks benefit coho fry (Michael jr, 1985)

This paper examines the relationship between the number and biomass of pink salmon spawning in Skagit River and the resulting return of adult coho salmon which were rearing as age-0 fish in the watershed at the time of spawning. From 1967 through 1985, during the odd-numbered years, there is a strong direct correlation between the biomass of pink salmon spawners… and recruit per spawner for coho salmon…

Traditional salmon management has concentrated on one species at a time. In order to take advantage of the enhancement benefit conferred by pink salmon spawners it will be necessary to examine interspecies impacts, reduced consumptive fisheries, changes in land use activities, and changes in stream flows from a much broader perspective than is presently employed.

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And there are many more studies with similar messages.

Notice the date on many of these?

Several from the mid to late 1990s and into early 2000s.

Curiously, this was a similar time when Canada’s Wild Salmon Policy began it’s early incantations — 1999 or so. The Policy has lots of nice words about ecosystem-based management, conservation, and so on… however, next to nothing implemented on the ground.

This year, a brave decision was made in late Aug. to close commercial fisheries targeting the huge run of Fraser sockeye to protect weaker stocks (e.g. Interior coho and steelhead) that are often caught in the marine mixed-stock fisheries. This is a step in the right direction.

One must ask though… what about all the years of taking 80% of the sockeye runs, or other salmon runs? How much did that starve the ecosystem from that essential influx of nitrogen and carbon and energy?

Including the next generation of salmon…?

Gee, could there be a link with the across-the-board declines?

Could there be a link to the healthier returns this year, due to huge declines in salmon commercial fishing pressure over the last 6-8 years?

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