The Great Lake Sturgeon

The Relationship between Lake Sturgeon Life History and Potential Sensitivity to Sea Lamprey Predation

n 153 HOLLY MUIR AND TRENT M. SUTTON The Relationship between Lake Sturgeon Life History and Potential Sensitivity to Sea Lamprey Predation The lake sturgeon Acipenser fulvescens, a species native to the Laurentian Great Lakes, has a unique life history. Like other sturgeons, lake sturgeon are a slow-growing, long-lived species with delayed maturation; first spawning for males typically occurs between ages 12 and 15, while females become mature between ages 18 and 27. In addition, lake sturgeon spawn intermittently, with females spawning only once every four to nine years and males spawning every one to three years (Roussow 1957; Scott and Crossman 1973; Fortin, Dumont, and Guénette 1996; Bruch 1999; Bruch, Dick, and Choudhury 2001). Although these life-history traits are advantageous for buffering against extreme environmental conditions, they increase susceptibility to human-induced mortality and the negative effects of aquatic invasive species (Hay-Chmielewski and Whelan 1997; Auer 2004). Despite supplemental stocking, efforts to improve water quality, and permitted harvest reductions, lake sturgeon populations have been slow to recover from their imperiled state throughout the Great Lakes basin (Welsh et al. 2008). This slow recovery is not surprising, considering the great age-to-maturity characteristic of lake sturgeon. However, another potential factor that may be currently impeding lake sturgeon rehabilitation is aquatic invasive species. For example, the invasive parasitic 154 n Holly Muir and Trent M. Sutton sea lamprey Petromyzon marinus preys on and kills lake sturgeon in confined tank experiments (Patrick, Sutton, and Swink 2009). The objective of this chapter is to review the effects of aquatic invasive species on Great Lakes lake sturgeon populations , with an emphasis on the potential effects of sea lamprey predation on both the decline and slow rate of recovery of lake sturgeon. Aquatic Invasive Species in the Great Lakes The introduction and establishment of undesirable, nonnative plant and animal species is one of the greatest threats to the future of the Great Lakes and to species and community conservation worldwide (Finster 2007; Thresher 2008). The Great Lakes have been subject to invasion by nonnative species since European settlement (Mills et al. 1993). Development of the basin, including timber harvest, agriculture, hydropower development, and canal construction, as well as invasion of marine organisms, fish stocking, and overharvest, have resulted in rapid changes in what was once a simple, slowly evolving ecosystem (Fetterolf 1980). At least 182 nonindigenous species have been introduced into the Great Lakes since 1840, with over 40 percent of these invaders occurring after the opening of the St. Lawrence Seaway in 1959 (Ricciardi 2006). The Great Lakes have the highest rate of nonnative species invasions and introductions recorded in any freshwater ecosystem. Since 1960, the invasion rate is estimated to be 1.8 species per year, equivalent to one new invader being discovered every 28 weeks. Though not all nonnative species jeopardize the Great Lakes ecosystem (some, such as the Pacific salmon, have been intentionally introduced to support commercial or recreational fisheries), those that are considered to be injurious are capable of inflicting significant damage to the environment and the economy (Finster 2007). The degree to which native fish and their habitats are affected by injurious aquatic invasive species depends on the life-history traits of invading and of native species, as well as the ability of the ecosystem to withstand change (Ricciardi 2006). To date, little is known about the injurious effects of aquatic invasive species on lake sturgeon. The Voracious Sea Lamprey Of all the aquatic invasive species thought to impact lake sturgeon abundance, the sea lamprey poses the most serious threat. The sea lamprey is similar in appearance to the American eel Anguilla rostrata, but lacking a jaw and paired fins, and having seven pairs of gill pouches instead of the usual gill structure of bony fishes. The Sea Lamprey Predation n 155 life cycle of the sea lamprey involves distinctively different larval and adult feeding phases. Whereas larval lampreys, called ammocoetes, feed primarily on organic detritus, adults in their predacious stage feed on the blood of other fishes (their hosts) (Lowe, Beamish, and Potter 1973; Sutton and Bowen 1994). After spending an extended larval phase (3 to 10 or more years) buried in the sediment of streams, sea lamprey larvae metamorphose into parasites, developing eyes and teeth, and enter the lakes to feed. The period of metamorphosis between these two feeding phases is called “transformation,” and lampreys...