RESEARCH Effects of Recent Volcanic Eruptions on Aquatic Habitat in the Drift River, , USA: Implications at Other Region Volcanoes

JOSEPH M. DORAVA* ciers on the northern and eastern flanks of Redoubt Vol- Alaska Volcano Observatory cano. During and following eruptions in 1989–1990, severe U.S. Geological Survey physical disturbances to the habitat features of the river ad- 4200 University Drive versely affected the fishery. Frequent eruptions at other Cook Anchorage, Alaska 99508, USA Inlet region volcanoes exemplify the potential effects of vol- canic activity on Alaska’s important commercial, sport, and ALEXANDER M. MILNER subsistence fisheries. Few studies have documented the Institute of Arctic Biology recovery of aquatic habitat following volcanic eruptions. The University of Alaska Fairbanks eruptions of Redoubt Volcano in 1989–1990 offered an op- Fairbanks, Alaska 99775, USA portunity to examine the recovery of the macroinvertebrate community. Macroinvertebrate community composition and ABSTRACT Numerous drainages supporting productive structure in the Drift River were similar in both undisturbed salmon habitat are surrounded by active volcanoes on the and recently disturbed sites. Additionally, macroinvertebrate west side of Cook Inlet in south-central Alaska. Eruptions samples from sites in nearby undisturbed streams were have caused massive quantities of flowing water and sedi- highly similar to those from some Drift River sites. This simi- ment to enter the river channels emanating from glaciers and larity and the agreement between the Drift River macroinver- snowfields on these volcanoes. Extensive damage to ripar- tebrate community composition and that predicted by a ian and aquatic habitat has commonly resulted, and benthic qualitative model of typical macroinvertebrate communities macroinvertebrate and salmonid communities can be af- in glacier-fed rivers indicate that the Drift River macroinverte- fected. Because of the economic importance of Alaska’s brate community is recovering five years after the distur- fisheries, detrimental effects on salmonid habitat can have bances associated with the most recent eruptions of Re- significant economic implications. The Drift River drains gla- doubt Volcano.

Commercial and sport fishery resources of the Cook and that adequate allocations of the remaining fish are Inlet region are economically important to the State of made in a fair way among the various users. This Alaska and generate hundreds of millions of dollars management challenge is undertaken with a series of annually. Additionally, many local residents rely on the tools that includes regulating subsistence, sport, and fisheries for subsistence and recreation. The sockeye, commercial fishing and land uses. However, aligned chinook, coho, pink, and chum salmon fisheries in the along the western side of Cook Inlet are five active Cook Inlet region thrive because much of the surround- volcanoes (Figure 1) that need to be considered in this ing land is undeveloped, water quality is unimpaired, management paradigm. These volcanoes have com- and seasonal streamflows are adequate to support bined to produce more than 90 volcanic eruptions abundant diverse spawning and rearing habitat. Signifi- cant challenges for managers of this fishery are to during the last 10,000 years (Riehle 1985). Recent ensure that adequate riverine habitat is available to eruptions at several of these volcanoes have significantly support the fish, that adequate escapements are allowed affected water quality (Mathisen and Poe 1978, Whet- into the rivers and estuaries to sustain the population, stone 1955, 1956, Wilcox 1959), changed channel geometry (Dorava and others 1993, Waythomas and Dorava 1999), and destroyed riparian vegetation (Dorava KEY WORDS: Aquatic habitat; Volcanoes; Lahars; Lahar-runout flows; and Meyer 1994). These volcanogenic alterations de- Macroinvertebrates; Community structure; Communit