Natural Hazards, Fish Habitat, and Fishing Communities in Alaska

—Fish and fishing communities are iconic symbols of Alaska. Volcanoes, earthquakes, and tsunamis also stand out as processes that define or shape the Alaska landscape. Alaska has numerous fishing ports that regularly rank in the top 10 ports for commercial landings by weight and value in the United States. In addition to commercial fisheries, subsistence fisheries and sport fishing play an important role in the economy and culture of Alaska. Alaska is home to one of the most active plate boundaries on the planet, where the Pacific Plate is subducting the North American Plate at rates greater than 5 cm/year. This process brings to Alaska earthquakes, tsunamis, and volcanic eruptions. Active plate boundaries around the Pacific basin also make Alaska vulnerable to transoceanic tsunamis generated by earthquakes thousands of miles away. Alaska is the most seismically active state in the United States by a large margin and one of the most active areas in the world. In this paper, we examine the distribution of fishing communities and fish habitat with respect to volcanic and earthquake hazards and discuss the possible implications of these natural hazards to fisheries. Because natural hazards cannot be prevented, communities must prepare for and minimize risk associated with such events. Understanding the nature and distribution of natural hazards is the first step in preparing for future events and limiting the impacts of those events. * Corresponding author: [email protected] Introduction Fish and fishing communities are central icons of Alaska and play an important role in the social and economic status of the state. Commercial, subsistence, and sport fisheries are important sources of income and food for communities throughout the state. For example, in 2005, commercial fishermen were paid nearly $1.3 billion for salmon, halibut, shellfish, groundfish, and herring harvested in Alaskan waters (ADFG 2006). Sport fishing is estimated to be worth more than $500 million annually (ADFG 2003). Similarly, subsistence fisheries, which are defined as fisheries for noncommercial, customary, and traditional uses, not only provide food and other necessities, but are a way of life. Subsistence fisheries are of such importance to communities that state and federal laws provide both protection for this type of fishery and give it priority over other uses of fish resources (Wolfe 1998). According to the Alaska Fish Distribution Database maintained by the Alaska Department of Fish and Game, the state contains more than 16,000 bodies of water, including streams, rivers, and lakes that are used by anadromous fishes such as salmon, char, and whitefish for spawning, rearing, or migration (Figure 1; Johnson and Weiss 2006). Coastal waters of the North Pacific Ocean, Bering Sea, and Arctic Ocean provide habitat important to many commercial fisheries. Other iconic features of the Alaskan landscape include natural hazards such as volcanoes and earthquakes. In this paper, we describe the distribution of these hazards relative to fishing communities and fish habitat. While other natural hazards, such as wildfire, exist in Alaska and have impacts at local scales, we focus our attention on regional or 376 ZimmErman Et al. statewide hazards associated with volcanoes and earthquakes. First, we describe the nature and extent of volcanic and earthquake hazards. Then, we discuss case studies of selected events with an emphasis on their potential or realized impacts to fishery dependent communities and fish habitat. To assess the relation of fishery-dependent communities and risk from volcanoes and earthquakes, we mapped the distribution of communities relative to volcanoes and earthquake risk. Sepez et al. (2005) used quantitative indicators to identify 136 communities considered to be dependent on involvement in commercial fisheries based on commercial fishery landings, number of processors, vessel registrations, number of crew licenses, and number of state and federal permit holders. Many more communities are also dependent upon recreational and subsistence fisheries, but limited data are available to reliably quantify dependence on these fisheries. Sport fishing-dependent lodges, guides, and communities are distributed throughout Alaska and are likely to be susceptible to hazards, but due to a lack of information concerning the distribution of sport fishing, we focus our discussion of risk to communities dependent on commercial fisheries. The communities identified by Sepez et al. (2005) are distributed throughout Alaska (Figure 2). Volcano Hazards in Alaska Alaska contains more than 40 historically active volcanoes that stretch 3,000 km from the Wrangell Mountains through Cook Inlet and along the Alaska Peninsula and Aleutian Islands (Miller et al. 1998). Based on the written record stretching back more than 200 years, an average of 1–2 eruptions occur each year, with most producing ash clouds, ash fall, and a variety of other products depending on the style and size of the event. Eruptions can be single pulses lasting minutes to hours or days, or they can be repetitive and chronic with numerous events occurring over months, years, and even decades. Alaska’s volcanoes Figure 1. Distribution of stream, river, and lake habitats used by anadromous fishes in Alaska. Data from the Anadromous Waters Catalog (Johnson and Weiss 2006). 377 natural haZards in alaska are typical subduction zone systems and erupt primarily andesitic lavas both explosively and effusively. Resulting processes impact areas immediately around the volcano and can affect terrain many tens or even thousands of kilometers away (Blong 1996; Myers et al. 2004). The eastern part of the volcanic arc, where oceanic crust is subducted beneath continental crust, tends to produce more silicic (and explosive) eruptions, compared to the western part of the arc, which has subduction of oceanic crust beneath another oceanic plate and where eruption of lava flows are more common. This transition occurs near the western end of Unimak Island. Fortunately, because of the sparse population in Alaska, few volcanoes in Alaska have communities or critical infrastructure immediately in harm’s way. The most common and far-reaching volcano hazard in Alaska is ash fall from ash clouds, produced during explosive fragmentation of ascending magma during volcanic eruptions of nearly all sizes and intensities. Ash—pulverized fragments of rock and volcanic glass less than 2 mm across—is ejected into the atmosphere where prevailing winds carry the ash for tens to thousands of kilometers. The largest of eruptions, such as the Novarupta eruption in 1912, can send ash around the globe. Ash clouds are a significant hazard to aircraft and can severely curtail or interrupt air travel, depending on the size and duration of the eruption. Fallout of ash, if heavy, can collapse buildings, damage vegetation, clog streams, and impact wildlife habitat for years. Energetic eruptions can also produce ballistics, pebbleto boulder-sized fragments of rock or pumice that travel as projectiles posing a serious hazard to people and structures within several kilometers of the vent. Pyroclastic flows and surges, avalanches or hurricane-force blasts of volcanic gas, ash, and rock debris, can travel away from a vent during explosive eruptions at speeds in excess of 100 m/s. The largest of pyroclastic flows accompanying significant eruptions can bury the landscape under hundreds of meters of debris, permanently changing the landscape. Lava flows and lava domes, products of effusive eruptions, are extremely hazardous in the immediate vicinity; sudden explosions can occur where lava comes into contact with Figure 2. Distribution of fishery dependent communities (circles) and active volcanoes (triangles)