The Iliamna Lake system (59°30’N lat., 155°W lon.) is dominated by Iliamna Lake (the largest lake in Alaska at 2,622 km²) and Lake Clark (370 km²). Numerous smaller lakes feed into these lakes and eventually discharge to Bristol Bay via the Kvichak River. The lakes are oligotrophic and covered with ice from December through May with rare exceptions. The eastern end of Iliamna Lake is relatively deep (>150 m) but has numerous small islands, and ends in steep mountains. The western end of the lake is wider, shallower, has few islands and the land becomes flat tundra towards the outlet. Lake Clark is turbid from glacial flow during spring and summer, whereas Iliamna Lake is clear (Secchi disk transparency ~15 m). The mountainous habitat surrounding Lake Clark is protected by the Lake Clark National Park and Preserve.
We have two facilities on Iliamna Lake: one at Iliamna Village (pop. ~500) near the shore of the lake and the other on Porcupine Island at the eastern end of the lake. The facility at Iliamna village is used as a point of arrival/departure (there are several scheduled jet flights between Anchorage each day), for research on the Newhalen River, and as a staging ground for studies at Lake Clark or travel to Porcupine Island. Four or more scientists can be supported at the Iliamna Village facility, which is powered by large village generators and utilizes well water for drinking and cooking. We have a bunkhouse, a second house with bathroom and cooking facilities, and a third very large storage building (originally built to house airplanes) where we keep all boats and vehicles during the winter. The facility has a telephone and fax machine. Scientists can travel to Lake Clark by plane or by trailering a boat above the falls on the Newhalen River and motoring up. Large, comfortable facilities at Lake Clark can be arranged with the National Park Service station at Port Allsworth. Vehicles available at the Iliamna village include a Chevrolet pick-up and a GMC suburban.
Most of our Iliamna Lake research has been conducted from the facility at Porcupine Island, located in the most protected region of Iliamna Lake, near many major sockeye salmon spawning grounds. This facility is powered by a diesel generator and can comfortably support up to 15 scientists in three cedar buildings, one of which has cooking and showering facilities, another doubles as a limnology lab and one has a large classroom in the front. We have a well-equipped shop for fabrication of apparatus and repairs. The Porcupine Island camp is accessed directly by boat or float plane from Iliamna Village or by wheel plane and boat via the nearby village of Pedro Bay. Boats available at the Iliamna Lake system include a 24’ aluminum Workskiff with a closed cabin, a 23’ open deck aluminum seine skiff, and three 18’ Lunds (one equipped with a jet motor).
Much of the early research at Iliamna Lake involved investigating the limnology of the system (e.g., Mathisen 1966). Lenarz (1966), Gunnerod (1971), and Carlson (1974) examined the life histories and population dynamics of key zooplankters (Cyclops scutifer and Bosmina coregoni). Other studies involved fish/zooplankton interactions (H oag 1972), limnological effects of volcanic ash (Mathisen and Poe 1978), and density-dependent growth of juvenile sockeye salmon (Mathisen 1969). Margolis (1967) and Pennell et al. (1973) described the parasite fauna of sockeye salmon, and more recently, researchers examinedthe possible relationship between parasites and sexual dimorphism of adult male salmon (Berg et al. 1995) and fluctuating asymmetry (Berg et al. 1997).
The Iliamna Lake system was noteworthy for the cyclic abundance of adult sockeye salmon (Mathisen and Poe 1981), and the exceptional runs in some years (up to 20 million salmon escaped the fishery) stimulated early investigations of the role of salmon carcasses in nutrient cycling. Donaldson (1967) developed a phosphorus budget for the lake and evaluated the effect on salmon growth and survival of nutrients from the millions of salmon carcasses deposited annually. Subsequent workers used stable isotope ratios of nitrogen to demonstrate that the marine-derived contributions from salmon carcasses represent the major source of limiting nutrients to these oligotrophic lakes and streams (Mathisen et al. 1988, Kline et al. 1993).
The biological basis for the cyclic behavior of Iliamna Lake populations has not been determined, but modeling by Eggers and Rogers (1987) indicated that it might have been generated by random fluctuations in abundance and depensatory fishing mortality. This research resulted in a dramatic change in the management of the system’s populations. Fishing pressure was reduced in “off-peak” years to increase sockeye salmon abundance. Over the next few years, we will be able to better understand the success or failure of this approach to conserving the overall abundance and diversity of salmon populations. The lake system has about 100 identified spawning populations, which differ dramatically in abundance. Their conservation is complicated by the fact that they all pass through the fishery and enter the lake at about the same time (Jensen and Mathisen 1987) and have unequal tendencies to cycle.
The Iliamna Lake populations occupy diverse physical habitats and show a corresponding diversity of life-history patterns. Early investigations on fecundity by Mathisen and Gunnerod (1969) led to more detailed studies on the variation in egg size and fecundity among populations (Blair et al. 1993, Quinn et al. 1995). Studies on male salmon indicated that, like the Wood River populations, those in the Iliamna Lake system also display great variation in secondary sexual traits. In particular, males that spawn in beach environments show extreme development of the dorsal hump. Kerns and Donaldson (1968) described the behavior of these beach-spawning populations, and subsequent research showed that sexual selection favors not only large males but those with deep bodies for their length (Quinn and Foote 1994). These breeding populations spawn at high densities in very clear water near shore and are ideal for testing hypotheses in behavioral ecology related to homing and spawning-site selection (Blair and Quinn 1991, Hendry et al. 1995), effects of skewed operational sex ratio on male behavior (Quinn et al. 1996), sexual dimorphism (Quinn and Blair 1992), and other features of reproductive biology. The beaches are an unusual physical environment for spawning, characterized by very large substrate and wind-driven water circulation (Leonetti 1995). The large substrate makes the salmon eggs vulnerable to predation by sculpins (Cottus spp.), initially studied by Roger (1971) and more recently by Foote and Brown (1998) and Dittman et al. (1998).
The core of our research is to maintain limnological, adult and juvenile sockeye salmon sampling. Every year, faculty, staff, and students record information on physical features of the systems (e.g., lake level, water temperature, date of ice-off) that affect fish, and we also sample zooplankton. We sample the juvenile sockeye salmon and other fish species to assess abundance, growth rates, and community composition. We also count the spawning adult salmon in streams, ponds, beaches and island beaches, and collect information on fish size and age. All of these sampling activities are fully permitted by and coordinated with, the Alaska Department of Fish and Game, with whom we share our information freely. Analysis of the data that we collect, and ADF&G data, provides the basis for forecasts of the next year’s run of salmon. In addition, research projects by faculty members, graduate students, and undergraduate students explore many different aspects of the ecology, behavior, and genetics of the salmon and other species, interactions with wildlife and resident fishes, and the entire ecosystems.