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Upper Russian Lake typical of the many scenic lakes on the Kenai Peninsula just 45 minutesfrom Anchorage by small plane. Trout, rainbows and Dolly Varden are found in abundance.Alaska Travel Division Photo.

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WILLIAM R. MEEHAN*

FISHING AND TIMBER HARVESTING are southeastAlaska's most important industries. Salmon and troutoften spend most of their freshwater life in streamsthat flow through forested watersheds. In the glacier-formed U-shaped valleys common in southeast Alaska.much of the best timber is found in the valley bottomsin close association with salmon and trout streams.This makes timber harvesting more difficult because

28 Spec. Issue No. 1, Vol. 25, Spring,1974.

logging activity can affect streams and the fish popu-lations which inhabit them.

Two major types of habitat are important to salmonand trout. The first is spawning habitat. In riffles con-taining clean gravel of the proper size, the eggs aredeposited in nests or "redds" which the fish havescooped out to a depth of a foot or more. The eggs arethen covered with gravel and remain in the redd for

NATURALIST

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several months as the embryos grow and develop intofry or young fish. During this period of incubation theeggs must receive a good supply of water to furnishnecessary oxygen and to remove the waste productswhich build up as the embryos develop. An increasein sediment in the stream as a result of careless log-ging practices can smother the gravel beds, reducingthe flow of water to the eggs, and resulting in fewerfry being produced.

Stream temperature is another factor that is impor-tant to the well being of the incubating eggs. Treesand brush along the stream banks help shade thestream and maintain the cool temperatures necessaryfor good growth and survival of salmon and trout inthe summer. In winter, this vegetation may also helpinsulate the stream by slowing down heat loss throughradiation back into the atmosphere. In Alaska, wherewinter temperatures often drop well below freezingfor long periods, this insulating effect may be as im-portant as maintaining cool temperatures during thesummer. In either case, the moderating effect of vege-

tation on fish habitat is an important consideration inplanning timber harvest.

The second type of habitat which is important forsalmon and trout is nursery or rearing habitat. Theseare the areas in which the young fish feed and grow.The young of some species, notably pink and chumsalmon, do not remain long in fresh water before theymigrate to sea. Others, such as coho salmon and steel-head trout, may reside in the streams for severalmonths or years before migrating to the ocean. Somefish are entirely freshwater residents even though theymay have access to the sea. In addition to cool, clean,well-oxygenated water the nursery areas must providecover and food for the fishes that inhabitat them. Here,too, excess sediment can create unfavorable condi-tions by reducing the habitat for aquatic insects—amajor source of food for the young fish.

*Formerly fisheries biologist with the Forestry Sci-ences Laboratory in Juneau, Alaska, now on the staffof the Forest Service's Forestry Sciences Laboratoryin Corvallis, Oregon.

Typical rearing or nursery area—a small tributary to Kadashan Creek, Chichagof Island. Smalltraps were set to capture young fish as part of a study to estimate production of fish in smallstreams.Photo by William R Meehan.

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A weir on an experimental section of a small rearing stream on Admiralty Island.Photo by William R. Meehan.

Because of the somewhat different requirements ofthe spawning and rearing areas, they may be quite dis-similar. Typical spawning streams are often quitelarge, consisting of a series of riffles and pools wherethe flowing surface waters can be oxygenated. Therearing areas, on the other hand, are often small tribu-taries, meanders of the main stream, sloughs, andother slow-moving water, rich in plant and inverte-brate animal life.

Because spawning streams are usually large, it iseasier to give them proper consideration when plan-ning timber sales during logging operations. Thesmaller streams and tributaries, so important to youngand resident fish, have received too little attention inthe past. Recent research in this field has emphasized

30

the important role of these small water courses. Muchmore attention is given these streams now than wasthe case just a few years ago, and this trend will un-doubtedly continue.

Logs and other logging debris which wind up in thestream are other potential hazards. Like sediment, finelogging debris (tree needles, bark, and twigs) is notcompatible with high quality fish habitat. Log jamsmay block access to spawning grounds and generallyprevent within-stream migrations. But some largematerial might be beneficial, for example, where coverwas previously lacking or where more pools wereneeded. Each stream must be considered individually.Whenever possible logging should be conducted sothat debris does not enter the stream channel in thefirst place.

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Southeast Alaska has more than its share of precipi-tation and overcast skies throughout the year. Theseconditions help to reduce the problems outlined so far.For example, research has shown that increases instream temperature after clearcut logging are con-siderably less in southeast Alaska than in manysoutherly areas. The cool, moist climate of southeastAlaska also helps promote rapid revegetation and thelush plant growth found commonly throughout theregion.

In order to better understand the habitat require-ments of salmon and trout in southeast Alaska, andthe effects of land use practices on fish habitat, aresearch program has been undertaken by the U.S.Forest Service. This project is headquartered at theForestry Sciences Laboratory, a unit of the PacificNorthwest Forest and Range Experiment Station, lo-cated at Juneau. Two permanent study areas havebeen established. One is at the Young Bay Experimen-tal Forest on Admiralty Island: the other is in theKadashan Creek watershed on Chichaof Island.

At Young Bay, research has been conducted to learnhow sediment accumulates in gravels of various typesand how this in turn affects survival of incubatingsalmon eggs. An artificial stream channel was con-structed so that researchers could control the volumeof water flow through the channel. its velocity, andthe size and shape of gravels. In another series ofexperiments, the extent of gravel shift was studiedunder various water-flow conditions. Since gravelmovement can seriously affect developing eggs, it isimportant to know the potential consequences of thoseactivities which alter normal streamflow patterns.

In the Kadashan watershed, research has been con-ducted to determine the role of small tributaries andbackwater areas in producing salmon and trout. Smalldams or "weirs" have been constructed on some ofthe tributaries. Biologists use the weirs to study themigration patterns of fish. In other studies, young fishare captured, marked, and released back into thestreams. Later, fish are again captured in the samearea of the stream. The ratio of marked to unmarkedfish helps the biologist estimate the number of youngfish using the stream. Studies are also made of thefoods available to fish, such as aquatic insects.

In addition to the permanent study areas at YoungBay and Kadashan, Forest Service scientists haveconducted studies related to fish habitat in severalother areas of southeast Alaska. Some of these studiesinclude an examination of the effects of forest fertiliz-ation on water quality, bioassays to determine thetoxicity of the herbicide 2, 4-D to young salmon andtrout, and development of a technique for studyingthe composition of gravel in the streambed.

The Alaska Department of Fish and Game, theEnvironmental Protection Agency, and the NationalMarine Fisheries Service are cooperating with theForest Service in studying various aspects of the fishhabitat-timber harvest problem. These agencies, andothers, are also working independently to find answersto some of the questions facing resource managers.Our ultimate goals are to provide those responsiblefor managing our natural resources with informationto help them in making good land use decisions, andih so doing to help conserve our natural resources forthe continued enjoyment a.nd use of future generations.

Capturing fish in an experimental section of a small tributary stream, using portable electro-shocker. This stream on Admiralty Island.Photo by William R. Meehan

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