Salmon energy: what really is the “maximum sustainable yield”?

the full cycle -- Kline, jr.

Did you take highschool physics class and learn about the laws of thermodynamics?

Thermodynamics is the study of energy, which exists in many forms, such as heat, light, chemical energy, and electrical energy. Energy is the ability to bring about change or to do work.

First Law of Thermodynamics: Conservation.

Energy cannot be created or destroyed; it can only be changed from one form to another. The total amount of energy in the Universe remains the same, merely changing from one form to another.

Second Law of Thermodynamics: Entropy.

In all energy exchanges, if no energy enters or leaves the system, the potential energy of the state will always be less than that of the initial state… entropy. For example, a car that runs out of gas will not run again until fuel is put in. The flow of energy maintains order and life. Entropy wins when organisms cease to take in energy and die.

Hmmm… let’s think about this for a moment.

Salmon start life as little fry. They swim out into the North Pacific and consume energy in the form of ocean critters. Salmon eventually return to their natal streams. Along the way the bundle of energy that they have become, is consumed by other critters — seals, orcas, eagles, etc.

Salmon enter their stream, swim up to their spawning grounds, some of the energy they consumed in the North Pacific is transferred into eggs and sperm, which is deposited into the gravel.

The adults die, however, it is by no means entropy. The adult carcasses are still bundles of energy that are in turn consumed by all sorts of critters. The bulk is most likely consumed by bugs. The bugs in turn become food for other critters… like baby salmon for example, or critters that baby salmon may feed on (esp. baby sockeye hanging out in lakes). Nothing is wasted.

And thus the first law of thermodynamics: energy is neither created nor destroyed; it just changes form.

_ _ _ _ _ _

But what about the second law?

What if one critter in the ecosystem (e.g. us, humans) decide that we want to take 80%, or 60%, or whatever % of the total energy supply returning to freshwater ecosystems in the form of adult salmon?

Aren’t these adult salmon sort of like the gas in the car tank?

Isn’t this a cycling of energy — fresh water to North Pacific to fresh water — that has been occurring for millions of years?

Sure we humans might put some of that energy back into the system through sewage treatment plants… however, a lot of it is exported to places that don’t have salmon: Wal-mart in Nebraska, Total in Wisconsin, Fred Meyer in Wichita… etc.

Add in that by us-humans taking energy out of the cycle and putting it somewhere else, we take energy away from the critters that rely on it — including the next generation of salmon.

Do a web search of Robert Bilby and “marine derived nutrients” and you can find lots of research on this simple fact.

Or this link: Impacts of marine-derived nutrients on stream ecosystem functioning

Energy and nutrient subsidies transported across ecosystem boundaries are increasingly appreciated as key drivers of consumer–resource dynamics. As purveyors of pulsed marine-derived nutrients (MDN), spawning salmon are one such cross-ecosystem subsidy to freshwaters connected to the north Pacific.

With this in mind… what is the “maximum sustainable yield” of salmon in human fisheries?

Should one critter be taking anywhere between 50%-80% of the total nutrients and energy returning to fresh water systems from deep within the North Pacific?

If this practice continues… when does entropy set in? How do you spell precautionary?

Energy and nutrient subsidies transported across ecosystem boundaries are increasingly appreciated as
key drivers of consumer–resource dynamics. As purveyors of pulsed marine-derived nutrients (MDN),
spawning salmon are one such cross-ecosystem subsidy to freshwaters connected to the north Pacific.

Leave a Reply

Your email address will not be published. Required fields are marked *