named, needless to say, not after Stev-en, the particle physicist, but Alvin, thenuclear-power engineer and administra-tor.) Particle physics, Roy argues, farespoorly on the test: the Þeld has littlesigniÞcance for the rest of physics, letalone for biology and the social scienc-esÑit is relevant only to itself. He thinksparticle physics will lead not to a theo-ry of everything, as some proponentshave claimed, but a theory of nothing.

Roy is also upset that the new, sup-posedly tight-Þsted Congress has notturned its knives on the Þeld. ÒWhy areRepublicans taking money away fromschool lunch programs and keeping itfor particle physics?Ó he cries. ÒWhyarenÕt we moving to privatize this?Ó Roymaintains that particle physicists, if cutoÝ from the public dole, could tap intothe riches of such high-tech entrepre-neurs as Bill Gates or David Packard.

Roy oÝered his views to Robert Walk-er, a Republican who recently becamechair of the powerful House Committeeon ScienceÑso far to no avail. But theresearcher insists it is only a matter oftime before Congress imposes Òreallydraconian cutsÓ on particle physics. ÒIgive them two more years, or maybefour at most,Ó he says. Seekers of a Þnaltheory had better hurry.ÑJohn Horgan

SCIENTIFIC AMERICAN May 1995 21

MIC

HA

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AW

FO

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The annual return of salmon tothe streams of their birth is oneof natureÕs great pageants and a

dramatic prologue to the spectacle ofseasonal change near the rugged edgesof the earthÕs temperate zones. In theNorthern Hemisphere, however, evi-dence of fundamental changes in thisancient ritual has begun to accumulate.

For more than 20 years, various stud-ies on PaciÞc Rim rivers have noted thatthe size of this Þsh, prized by anglersand epicures alike, has declined. In astudy presented last October, biologistsBrian Bigler and John H. Helle made theÞrst thorough assessment of the prob-lem: reduced sizes are being foundthroughout the North PaciÞc, in a vastarea stretching from Japan to Califor-nia. ÒIt is astonishing and frightening,Ósays Bigler of Wards Cove Packing Com-pany, a commercial Þshing concern.

Previous problems with salmon, par-ticularly reduced populations on speci-Þc rivers, have convincingly been tied tohuman activityÑto hydroelectric damsand overÞshing as well as to loggingand pollution. In the latest Þndings,though, some more pervasive factorseems to be at work.

Helle, who is at the National MarineFisheries Service, and Bigler revieweddata from government records, pub-lished reports and other sources. Thetwo concluded that of 47 populationson speciÞc rivers (ÒrunsÓ) of the Þve

salmon species in the North PaciÞc, 45experienced decreases in average indi-vidual weight between 1975 and 1993.The losses were more than 25 percentfor nine runs and less than 10 percentfor 10 of the others.

The discovery is worrisome becausestudies of North PaciÞc salmon havelinked smaller body size to reduced re-productive success. Besides being illequipped to meet the demands of up-stream migration, small Þsh build infe-rior nests. They produce smaller eggsthat hatch diminutive, less hardy fry.

Unsettling trends have also been no-ticed among salmon in the North Atlan-tic. But, in general, the problem there isa decline in numbers, says Kevin D.Friedland of the National Marine Fish-eries Service. Waterwheels in the 19thcentury, then hydroelectricity and pol-lution, ended runs on many rivers inNew England and parts of Europe. Al-though restoration eÝorts had reestab-lished some runs by the 1970s, popula-tions have continued to dwindle.

In the PaciÞc, size reductions coincidewith increased numbers. Throughoutthe region, hatcheries serve to reestab-lish and sustain runs on rivers whereno wild stocks remain or to enhancewild populations. Virtually all salmonstocks on Japanese rivers are entirelybred in hatcheries, whereas on NorthAmerican and Russian rivers such Þshtend to be a minority. Total hatchery

CH

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life

Col

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ion

COHO SALMON returning from the PaciÞc to spawn in North American rivers havebeen getting smaller since 1975, losing an average of 0.012 to 0.059 kilograms a year.

So Many Salmon, But So LittleOcean warming may be shrinking the size of PaciÞc salmon

+3 +4 +5 +6

1 IN1,000

1 IN 100

1 IN 10

1 IN 1

Death fromRussian roulettein Russia and

elsewhere

Dyingfromsome

cancer

SOURCE: Up to Your Armpits in Alligators? by John and Sean Paling; all figures are annual risks for the U.S. except where specified

Things thathappen tohalf thepopulationanywhere,anytime

Death fromsome causehere, there andeverywhere

Copyright 1995 Scientific American, Inc.

contribution to the North PaciÞc is about5.5 billion young salmon a year; the cor-responding number of wild young isbelieved to be about 20 billion.

In recent years hatchery productionmay have reached such a level that itmore than compensates for the reduc-tions in annual returns caused by hu-man activity. This fact, combined withrelatively high survival rates of wild Þshand record harvests, has led some Þsh-eries experts to suggest that the totalnumber of salmon in the PaciÞc is high-er now than it has ever been.

Some biologists argue that hatcher-ies genetically weaken stocks by allow-ing unsuitable Þsh to survive. Theirweaknesses then enter wild populationsthrough interbreeding. But that notionis not rigorously supported by experi-mental data, and it is generally down-played as an explanation for size re-ductions. There is also little evidencethat another oft-cited culprit, commer-cial gill netting, is responsible either.

Instead the explanation that seemsbest to Þt the facts concerns the amountof plankton, krill, young Þsh and otheredibles the marine environment servesup. This so-called oceanic carrying ca-pacity, some experts suggest, can nolonger sustain the salmonid hordes.ÒYouÕre getting older, smaller Þsh per-

vading the ocean,Ó Bigler says. ÒItÕs atextbook example of population re-sponse to overgrazing of limited foodresources.Ó Supporting this thesis arerecent Þndings of a precipitous drop inPaciÞc zooplankton populations overthe past 44 years.

Carrying capacity is quite complex,however, and teasing apart its inßuenceon salmon size is proving challenging.Whether Þsh Þnd food depends on cur-rents, temperature, light, chemical con-ditions and the mix of organisms in thefood web. All these factors are, in turn,entangled with climate. ÒWeÕre dealingwith a very new idea in Þsheries sci-ence: that climate and the marine envi-ronment can cause rather abrupt chang-es in ocean survival trends,Ó states DickBeamish of CanadaÕs Department ofFisheries and Oceans.

Since the mid-1970s water ßows oncertain key rivers, such as the Fraser inBritish Columbia, have been abating,and water has become warmer. Suchhavoc, some researchers reason, couldbe caused only by climate changesÑspeciÞcally ones traceable to the recur-ring El Ni�o Southern Oscillation in thePaciÞc and the North Atlantic Oscilla-tion, because of their vast movementsof warm ocean water.

Indeed, recent studies have correlat-

ed salmon population size to climatephenomena. In the Atlantic, a signiÞ-cant factor underlying sparse popula-tions is fewer salmon that spend morethan one winter at sea before returningto spawn. Such Þsh are important tothe well-being of Atlantic salmon stocksbecause of their robustness and superi-or spawning. Friedland recently foundthat their populations rise and fall inproportion to the size of the area of theocean that is between four and eight de-grees Celsius, and his latest work sug-gests that the mechanism may be close-ly tied to variability in their annual mi-ration pattern, as inßuenced by climate.

Similar correlations have been estab-lished between PaciÞc salmon and cli-mate. In the late 1980s researchersfound that the abundance of pink,chum and sockeye rose and fell withthe expansions and contractions of theAleutian low-pressure index, an enor-mous winter-weather system.

In the end, far from being anotherstraightforward example of the conse-quences of human meddling, the caseof the mysterious shrinking salmonmay turn out to be much more compli-cated. ÒNatureÕs pretty tricky,Ó says RayHilborn of the University of Washington.ÒA lot of changes going on out there wecanÕt control.Ó ÑGlenn Zorpette

Copyright 1995 Scientific American, Inc.Copyright 1995 Scientific American, Inc.