Browsing by Subject "Fish species"
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Item An Evaluation of the Importance of Mysis relicta to the Lake Superior Fish Community(2010-05) Isaac, Edmund JacobMysis relicta is a major prey item for many fish species in Lake Superior, However, its importance to an entire fish community as a whole has not been quantified. We describe seasonal prey selection of the major fish species collected across 18 sites in Lake Superior, and again at five locations in western Lake Superior in 2006 using a selection index (Chesson's Alpha). We also used bioenergetics models to estimate the consumption of prey items by the fish community at the same locations. Additionally, we modeled the production of Mysis, to evaluate this prey resource in terms of demand and supply. We found that rainbow smelt, kiyi, and bloater selected for Mysis over other prey items during all seasons, while lake whitefish only selected for Mysis in the spring and summer. Cisco selected for large zooplankton, while all three sculpin species exhibited neutral selection of prey items. Burbot and siscowet selected for deepwater sculpin and Mysis during all seasons, with juveniles showing a stronger selection for Mysis than did adults. Mysis was the most consumed prey item lakewide, with higher annual consumption offshore than nearshore. Predation on Mysis was mainly from rainbow smelt, bloater, and lake whitefish nearshore, and deepwater sculpin and kiyi offshore. Our estimates of Mysis production (supply) were higher than the consumptive demand by the fish community at nearly all locations, with this balance indicating stability in the food web. Mysis relicta was found to be a sought after prey item by many fish species, and is directly responsible in supporting the fish communities both nearshore and offshore. Thus, Mysis plays a pivotal role in the structure and function of the Lake Superior fish community.Item Regional, Watershed, and Site-Specific Environmental Influences on Fish Assemblage Structure and Function in Western Lake Superior Tributaries(2005) Brazner, John; Tanner, Danny K; Detenbeck, Naomi E; Batterman, Sharon L; Stark, Stacey L; Jagger, Leslie A; Snarski, Virginia MThis report assesses the impact of human activities and forest fragmentation on fish communities in the western Lake Superior basin. Human-induced activities noted in the report included temperature changes, siltation, erosion, forest cover and forest manipulation, and invasive species. Specific results are reproduced below. “The relative importance of regional, watershed, and in-stream environmental factors on fish assemblage structure and function was investigated in western Lake Superior tributaries. We selected 48 second- and third-order watersheds from two hydrogeomorphic regions to examine fish assemblage response to differences in forest fragmentation, watershed storage, and a number of other watershed, riparian, and in-stream habitat conditions. Although a variety of regional, fragmentation, and storage-related factors had significant influences on the fish assemblages, water temperature appeared to be the single most important environmental factor. We found lower water temperatures and trout–sculpin assemblages at lower fragmentation sites and higher temperatures and minnow–sucker–darter assemblages as storage increased. Factors related to riparian shading and flow separated brook trout streams from brown trout (Salmo trutta) – rainbow trout (Oncorhynchus mykiss) streams. Functionally, fish assemblages at lower fragmentation sites were dominated by cold-water fishes that had low silt tolerance and preferred moderate current speeds, while fishes with higher silt tolerances, warmer temperature preferences, and weaker sustained swimming capabilities were most common at higher storage sites. Our results suggest that site-specific environmental conditions are highly dependent on regional- and watershed-scale characters and that a combination of these factors operates in concert to influence the structure and function of stream fish assemblages. Key points: This study was completed within 160 km of Duluth, Minnesota, in the Northern Lakes and Forests Ecoregion and within two ecological units, the North Shore Highlands (north shore streams) and the Lake Superior Clay Plain (south shore streams)which provided excellent contrast in hydrogeomorphic types. Functionally, south shore fishes tended to be silt-dwelling, trophic generalists with slow current preferences and a tendency towards nest-guarding spawning behavior. North shore fishes tended to be single-bout spawners with fast current preferences. From a management perspective, our results suggest that both timber management and wetland restoration or degradation decisions will need to be considered by resource managers when fish community health is a concern. For example, increasing percentages of mature forest cover should allow for salmonid–sculpin assemblages to become more prevalent in streams with the potential for cool or cold waters. Similarly, increased wetland cover should allow for a greater predominance of healthy warmwater fish assemblages assuming that other landscape features are not too badly degraded. By understanding the species structure and functional character of an assemblage and its relationship to landscape features, managers should be able to make at least a rough assessment of watershed condition. Lacking fish data, it might be easier to simply characterize forest cover and storage as a first step in identifying which watersheds likely contain streams that are degraded. Our results suggest that although in-stream habitat rehabilitation should continue to be used an important tool to improve biological conditions in streams, restoration efforts will have greater success if the potential interactions with landscape conditions are factored into the decision-making process. In some situations, manipulation of forest cover or watershed storage may have a greater impact on fish assemblage integrity than in-stream habitat improvements.”Item Water Quality (2000-08) and Historical Phosphorus Concentrations from Paleolimnological Studies of Swamp and Speckled Trout Lakes, Grand Portage Reservation, Northeastern Minnesota(2010) Christensen, Victoria G; Jones, Perry M; Edlund, Mark B; Ramstack, Joy MA paleolimnological approach was taken to aid the Grand Portage Reservation, in northeastern Minnesota, in determining reference conditions for lakes on the reservation. The U.S. Geological Survey, in cooperation with the Grand Portage Band of Chippewa Indians and the Science Museum of Minnesota, conducted a study to describe water quality (2000–08) and historical total phosphorus concentrations (approximately 1781–2006) for Swamp and Speckled Trout Lakes. Results from this study may be used as a guide in establishing nutrient criteria in these and other lakes on the Grand Portage Reservation. Historical phosphorus concentrations were inferred through paleolimnological reconstruction methods involving diatom analysis and lead-210 dating of lake-sediment cores. Historical diatom-inferred total phosphorus concentrations in Swamp Lake ranged from 0.017 to 0.025 milligrams per liter (mg/L) based on diatom assemblages in sediment samples dated 1781–2005. Historical diatom-inferred total phosphorus concentrations in Speckled Trout Lake ranged from 0.008 to 0.014 mg/L based on diatom assemblages in sediment samples dated 1825–2006. In both lakes, historical changes in diatom-inferred total phosphorus concentrations did not exceed model error estimates, indicating that there has been minimal change in total phosphorus concentrations in the two lakes over about two centuries. The pH and alkalinity values of waters in both lakes indicate that general water-quality conditions likely are not threatening fish or acid-intolerant forms of aquatic life. Lake-sediment cores from Swamp and Speckled Trout Lakes were collected in 2006 and dated back to 1781 for Swamp Lake and 1825 for Speckled Trout Lake. A large increase in sediment accumulation rate after 1960 likely was a result of logging along the northeastern shore of Swamp Lake in 1958. The diatom flora of Swamp Lake is very diverse with more than 280 diatom taxa found in the core samples. These diatoms included many rare or uncommon species and several unknown taxa. Minor increases in sediment accumulation rates in the Speckled Trout Lake core occurred between 1840 and 1880. These increases may have resulted from fires following droughts in northeastern Minnesota. Heinselman (1973) identified five periods of fire in the 1800s for the Boundary Waters Canoe Area, Minnesota: 1801, 1824, 1863–64, 1875, and 1894. Most of these fire periods followed prolonged droughts of subcontinental extent, including the 1864 drought. Similar to the Swamp Lake core, the diatom flora of the Speckled Trout Lake core was very diverse and dominated by softwater diatoms. More than 215 diatom taxa were found in the core samples including many rare or uncommon species and several unknown taxa. Results of loss-on-ignition analyses indicated that sediment from Swamp Lake historically has been dominated by the inorganic component with a shift to an organic component in modern sedimentation. Median values of recent (2000–08) total phosphorus concentrations in water-quality samples and diatom-inferred phosphorus in recent sedimentation in Swamp and Speckled Trout Lakes were similar. These similarities, coupled with strong analogues for subfossil diatom communities for both lakes within the 89 Minnesota lakes diatom transfer function, indicate that recent and historical diatom-inferred phosphorus reconstructions might be used to help establish reference conditions and nutrient criteria for Grand Portage Reservation lakes when a sampling program is designed to ensure representative phosphorus concentrations in water samples are comparable to diatom-inferred concentrations.Item A Winter Survey of Fishes in the Vicinity of the WLSSD Sewage Treatment Plant: November 1991-April 1992(University of Minnesota Duluth, 1992) Richards, Carl; Kutka, Frank; Tucker, PaulThe Western Lake Superior Sanitation District’s (WLSSD) waste treatment facility on the shore of the St. Louis River estuary contributes a large volume of warm effluent to the St. Louis River on a continuous basis. The effluent mixes with the river in a relatively shallow embayment adjacent to the treatment facility and forms an area approximately 0.5 kilometer in diameter in which water temperatures and conductivities may be considerably different than surrounding river waters. This mixing zone can also have chemical characteristics that contrast significantly with unmixed river water. During winter conditions, elevated temperatures within the mixing zone may provide a potential refuge for fish species that are unable to exist in the cold waters of the river, and, some native species may seek warmer temperatures during winter when they are available. Alternatively, fish species may avoid the elevated temperatures or water chemistry characteristics of the mixing zone. Either of these situations could result in altered fish community characteristics during winter months. The purpose of this study was to provide preliminary data on the types and relative abundances of fish that inhabit the mixing zone during several winter months. Surveys were only conducted within 0.3 km of the outfall pipe; results were compared to other winter fish abundance data from the St. Louis River estuary.