The Problem of Carrying Capacity

A potentially serious problem with the hatchery solution is that all the salmon are sent to the same pasture: the North Pacific Ocean. To the extent that the pasture is getting overgrazed, the more new hatcheries we build, the fewer salmon will come back. And it is not just the ocean that may have limits to carrying capacity; some biologists believe that the draining and diking of the Columbia River estuary may have created a “bottle-neck to production” there.61

The facts are surprising. It has been estimated that during the historic peaks of salmon production in the 1850s, approximately 264 million salmon smolts were produced in the Columbia River Basin.62 While this is probably an overestimate, until very recently, we producing even more salmon smolts every year, mostly in Columbia Basin hatcheries. As the Corps of Engineers recently observed:

“Based on hatchery releases of nearly 203 million fish, and an estimated 145 million naturally-produced fish, a total of nearly 348 million salmonid smolts were present in the Basin in 1990. This is 32 percent above estimated smolt production numbers prior to 1850, yet adult returns remain low.”63

There was some truth to environmentalist historian Keith Petersen’s charge that “Dam-fodder smolts became official government policy.”64 As the Lower Snake River Compensation Program and other efforts got underway in the late 1960s and early 1970s, dams were killing a lot of juvenile salmon, mostly because of gas supersaturation and other construction-related problems that were later solved.

But after survival problems were fixed at the dams, hatchery production and harvest levels remained very high, inevitably wiping out less-productive wild runs. The hatchery smolts survived their migrations and probably reached the ocean in greater-than-historic numbers. As hatcheries raced to “mitigate” overestimated dam losses with higher and higher production, harvest levels set based on hatchery output not only weeded out wild runs, but also less productive upriver hatcheries.

As adult returns to the hatcheries began to drop, hatchery managers responded by pumping out more and more smolts. They are unwilling to do what farmers putting too many sheep on a pasture must do: take some of the sheep off. By the 1990s, it seemed possible that the river, the estuary, and even the North Pacific Ocean might all be overgrazed, but nobody was was willing to do anything about it.

Biologists are beginning to recognize that to understand the effect of changes in dam operations on salmon populations, we need to understand the whole ecosystem used by salmon, including the freshwater and saltwater components. The saltwater component, the ocean, has until recently been a black box. No one really knew what happened in the ocean. Massive hatchery releases in the ocean could actually reduce adult returns.65 The National Marine Fisheries Service did call for BPA to fund studies of this phenomenon in 1995, but the states and tribes de-prioritized the research.

Thus it is unknown whether it is even possible to increase salmon given such carrying capacity constraints.66 The Northwest Power Planning Council’s Independent Science Group has suggested that it is “speculative” and that there is “little empirical support” for the idea that the salmon bearing ecosystem in the Pacific Northwest and Northeast Pacific Ocean has considerable excess carrying capacity.67

Carrying capacity is not just a problem with building hatcheries. It is a problem with any means used to increase the survival of juvenile salmon. The possibility that we have already gotten enough smolts downriver alive to exceed carrying capacity means that the idea that we can significantly increase salmon production in the Columbia River Basin above present levels at all is inherently speculative. Our only hope for having more salmon in the river may be to limit adult harvest in the ocean.

61 See, e.g., Declaration of Douglas Neeley, Feb. 7, 1993, at 13, filed in IDFG v. NMFS, No. 93-1603-MA (D. Or.).

62 NWPPC, “Compilation of Information on Salmon and Steelhead Losses in the Columbia River Basin”, Appendix D of the 1987 Fish and Wildlife Plan.

63 U.S. Army Corps of Engineers, “Interim Status Report”, at 2-9.

64 K. Petersen, River of Life, Channel of Death 12.

65 See NRC, Upstream at  46 (Prepub. ed.)

66 See generally W. Pearcy, Ocean Ecology of North Pacific Salmonids, at 26-28, 91-94 (1992) (noting food limitation and competition in estuaries and North Pacific ocean).

67 ISG, Return to the River 48 (The principle is given “level 4” support, described at p. 47 as “speculative, little empirical support”)

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