Forget the circle of life. In this fisheries decision, we are playing for keeps.

Life doesn't  go in a circle. Nature is always changing and it never comes back to exactly where it was. That's why what we do matters.

An example is the climate, which we are changing by burning fossil fuels, and the resulting northward march of the ranges of plants, animals and bugs.

The spruce bark beetle plague has made it north to the Alaska Range. We will never again live the reliably cold, snowy winters or that I remember in Anchorage 40 years ago.

[Spruce beetle devastation returns to Southcentral Alaska — and moves north]

Change is not so obvious in the ocean, but we can also permanently transform the magnificent and incomprehensibly complex marine ecosystem. We have done so in many places.

A century ago, herring swarmed Kachemak Bay in enormous schools that took half an hour to pass. In 1926, a biologist recorded the crazy scene in Halibut Cove Lagoon, as 50 beluga whales fed on a roiling, flashing school of fish.

"Cormorants, murres, surf scoters, and divers were there in tens of thousands, and scores of bald eagles were circling about," he wrote.

Those schools were soon fished out. They never came back.

No one alive remembers that circus of life. The packs of belugas that chased the herring run up the bay are gone, too, recorded only in local histories.

We don't know what else is missing. The machinery of the ecosystem is too complex.

Herring perform a critical role as a conduit of energy—calories—from the plankton they eat to their predators, including salmon, halibut, birds and whales. Along with obscure little fish such as sandlance and smelt, they provide forage for a vast array of creatures.

If you pull the fuel line out of a car, it won't go. But ecosystems have alternative energy routes. Kachemak Bay life survived after herring, perhaps with larger runs of the other forage fish species.

It might take decades until one of those species has a bad year and food isn't available for salmon and halibut. Then we would all scratch our heads and wonder about the bad fishing year, assuming it is a natural phenomenon, never thinking of herring.

[Emptied tide pools tell the story of Kachemak Bay's disrupted ecosystem]

This didn't happen only in Kachemak Bay. In the early 1980s, mismanaged commercial fishing knocked down several herring runs in Southeast Alaska that never came back.

In Prince William Sound, a rich spawn of herring in the spring of 1989 occurred amid the oil spilled by the tanker Exxon Valdez. Four years later, the run collapsed and never recovered.

The rational conclusion is that herring runs don't come back once damaged, at least not in time spans human beings are used to waiting.

The great numbers in these huge runs probably provide protection from predators. Without those swarms of fish, the few individuals left are easy pickings.

There's nothing we can do to build them back. We can't make herring swarms. Even a century without fishing may not be enough.

This week, the Alaska Board of Fisheries will decide the fate of the last great commercial sac roe herring fishery in Southeast Alaska, the famous spring explosion of life that happens in Sitka Sound.

Alaska Native groups have asked the board to reduce the commercial catch and create conservation zones around subsistence areas to exclude commercial harvest. The Assembly of the City and Borough of Sitka and the local Fish and Game Advisory Committee support the concepts.

Alaska Natives have stepped forward as protectors of the herring run because herring eggs are a traditional food used at celebrations. For countless generations their people have lowered spruce branches into Sitka Sound upon which herring lay eggs.

Years ago, I joined Chugach Natives who were gathering herring roe from kelp in Prince Williams Sound. The eggs are the essence of fresh, salty goodness, translucent, better than caviar. I can still feel them popping between my teeth.

Sitka Natives have been unable to fulfill their subsistence needs for roe five of the last seven years. But even as the run declined, a commercial fishery has continued stripping roe for sale in Japan, sending herring flesh to the grinder for use in fish farms.

It's a cultural and spiritual issue for the Natives, who face the permanent loss of an ancient practice. It's like no more turkey for Thanksgiving—forever.

Biologists for the Alaska Department of Fish and Game say they have done a good job of managing the fishery. Although the run has declined from a peak six years ago, their data show herring numbers are still above average over the long span of measurements.

It's possible, they say, that the herring are spawning away from where the Sitka Natives are looking for them. Spawning areas change.

But Natives says that's not true. Aaron Bean, an Assembly member who has worked on these issues for years, said he has a fast boat and knows how to find the spawn, and he can no longer get the eggs he needs.

In 2013, Bean asked the Board of Fisheries to add herring to a list in Alaska's Forage Fish Management Plan, which outlaws commercial fishing for these keystone species—although herring would be specifically excluded from that restriction.

"It's in the best interests of the fishermen that the fish in the ocean be able to eat," Bean said.

The board voted down calling herring what it is—and no one can dispute it is a forage fish.

I don't doubt that Fish and Game has managed herring well using the tool they have, a computer model that predicts the maximum sustained yield based on dive survey data.

But Bean and his tribespeople are right. Maximum sustained yield is not the right equation.

Herring must be managed in the context of the ecosystem, considering their changing food supply and the species other than humans that eat them. Climate change has warmed the water, affecting plankton, and whales have multiplied in Sitka Sound, consuming herring.

The old rules of thumb may not work anymore. And getting it wrong just once could be permanent.

We can't afford more losses like that.

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