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Literature Review: Examines Relationships among Land Use, Stream Temperature, Habitat, and Competition between Brook and Brown Trout Populations Dustan Hoffman Department of Resource Analysis, Saint Mary’s University of Minnesota, Winona, MN 55987 Keywords: Land Use, Brook Trout, Brown Trout, Competition, Water Temperature, Riparian Zone, Agriculture, Forest, Climate Change Abstract Brook trout (Salvelinus fontinalis) commonly occur in cold water streams with a natural riparian zone and stream morphology. Brown trout (Salmo trutta) withstand warmer water temperatures and more degraded stream conditions than brook trout. This review focuses on four key themes: (a) riparian zone, (b) water temperatures, (c) stream condition, and (d) competition between brook and brown trout. GIS mapping of land use, stream characteristics, and climate change models were used to identify land use practices and their influence on water temperature. Climate change models tend to indicate rising temperatures in the future and, consequently, a reduction in suitable trout habitat. Altering land use practices may prevent water temperature increase and preserve crucial brook trout habitat. Competition for stream habitat and food resources exists among trout species, favoring brown trout over brook trout. Forested and densely-vegetated riparian zones support ideal conditions for stream quality and temperature buffering as opposed to riparian zones with grazing, cropland, and human disturbance. Introduction increase, impacting brook trout negatively (Carlson, Hendry, and Letchers, 2007). Research Problem Description Significance of Research Land use practices of stream riparian zones within southeast Minnesota include forest, agriculture, cropland, road crossings, and urbanization. Derivation from natural stream quality and riparian zone conditions through land use practices has shown increases in water temperature (Vondracek, Blann, Cox, Nrebonne, Mumford, Nerbonne, Sovell, and Zimmerman, 2005). Climate change models indicate slight increases in air temperature increase water temperature, reducing the amount of suitable habitat for trout (Mitro, Lyons, and Sharma, 2011). In addition to decreased habitat, competition between brook and brown trout would The introduction of non-native brown trout to southeast Minnesota caused a decrease in the range and abundance of native brook trout (Carlson, 2007; McKenna and Johnson, 2011; Hudy, Thieling, and Gillespie, 2008). Brown trout withstand warmer water temperatures and handle degraded stream conditions more easily than brook trout (Hudy et al., 2008), which creates concern for the more sensitive and less abundant native brook trout. A difference observed in the 2005 and 2011 Minnesota trout angling publication indicates there has been a 32% (25 to 17) reduction of streams in southeast Minnesota where wild brook trout were the only salmonoid species reported (Minnesota Department of Natural Resources, (MNDNR) 2005; MNDNR, 2011). Understanding land use characteristics of riparian zones and their relationship to stream temperatures may aid management and researchers in preserving the native brook trout populations (Hastings, Johnson, and Mitro., 2011). If predicted climate changes take hold, suitable stream habitat will be lost and brown trout would be forced to move to headwater reaches, increasing pressure on brook trout populations (Flebbe, Roghair, and Bruggink, 2006). stream quality, negatively impacting native brook trout and all other trout populations (McKenna et al., 2011; Vondracek et al., 2005). Identifying land use within a riparian zone may be useful in predicting, categorizing, and prioritizing management practices in a position where climate changes occur (Trout Unlimited, 2011; Hudy et al., 2008; Stranko, Hilderbrand, Morgan, Staley, Becker, Roseberry-Linclon, Perry, and Jacobson, 2008). Forested Land Forest cover exceeding 68% within a riparian zone has been used as a predictor in a land cover model developed by Hudy et al., (2008) to determine the likelihood of brook trout populations in the eastern United States. In addition, 94% of all streams with suitable trout habitat contained more than 68% forest land in the riparian zone (Hudy et al., 2008). However, heavily spring-fed streams within southeast Minnesota have been shown to be more independent temperature buffering systems even with tree cover removed (Hastings et al., 2011). Additional studies outside of southeast Minnesota indicate Maryland brook trout were seldom found in watersheds which contained 4% or more impervious land cover including, agriculture, forest clearing, and urbanization (Stranko et al., 2008). Often times, the removal of forested land cover results in increased agriculture and human-dominated land use, which will in turn create changes to habitat within a stream (Flebbe et al., 2006). Brook and brown trout biomass was positively correlated to higher percent values of forested land over cultivated, pasture, and grasslands in southeast Minnesota (Vondracek et al., 2005; Blann, 2000). Delimitations of the Problem Delimitations for this literature review include the native brook trout region of the United States, though brook trout and brown trout have been stocked in other areas of the continent. Rainbow trout are stocked in streams of southeast Minnesota; however, their abundance and likelihood of reproducing naturally in streams with wild brook trout is minimal (MNDNR, 2011). Temperature models used for this literature review consisted of models for eastern and midwest sections of the United States, rather than a continental or global scale. Literature Review Riparian Zones Southeast Minnesota contains a section known as the Driftless Area, where remains of glacial deposition or “drift” are absent from the last glacial period (Trout Unlimited, (TU) 2011). Limestone geology and karst topography account for the many spring-fed streams in this unique area (Blann, 2000). Many of the land use practices in the past century have degraded 2 Although wooded areas may provide a more extensive overhead cover, relationships with sediment load and turbidity of streams were further reduced in riparian zones with native grasses and forbs (Vondracek et al., 2005). Consideration of species in wooded areas may be a concern, as non-native species such as box elder, Acer negundo, have a short life expectancy, and may shade out valuable native grasses and forbs, which reduce sedimentation (Vondracek et al., 2005). Typically, forested land cover has been linked to cleaner and colder water sources for trout to persist in than agricultural and urban riparian zones (McKenna et al., 2011). McKenna et al., (2011) the best trout habitat in one area included land cover of pasture and forest patches. Views among studies have not all indicated negative relationships to agricultural land use in a riparian zone. Trout Unlimited (2011) created a stream assessment on 819 subwatersheds in which 616 watersheds received best score in land conversion security, stating that risk of future conversion to agricultural land was low because much of the land was already converted. Within the same study however, only 4 of 819 watersheds scored a best in the watershed condition analysis (Trout Unlimited, 2011). Management plans have also been developed to use rotational grazing to improve riparian zones and stream characteristics such as width, bank height, and flooding lanes (Moechnig, 2007). Stream characteristics such as width and depth have been implied to be a crucial part of the mean water temperature (Vondracek et al., 2005), which is a limiting factor to both brook and brown trout. Agricultural Land Much of southeastern Minnesota has been converted for agricultural grazing and crop land, which have caused dramatic changes in stream habitat. Management practices that restore a stream system to presettlement condition can take up to an additional 50 years before stream morphology has fully recovered (Hudy et al., 2008). Stranko et al. (2008) report brook trout showed a trend of inhabiting streams with low agricultural impact, low human impact, low water temperature, low sedimentation, and high forestation. In addition, Flebbe et al. (2006) state land use pertaining to agriculture and human land use are likely to reduce the suitable habitat for trout and become subject to water warming. Agricultural land within a riparian zone can cause water quality and sedimentation problems especially in hilly terrain; however, a densely vegetated riparian zone can reduce these impacts (Newcombe and Jensen, 1996). The Driftless Area within southeast Minnesota consists of steep valleys and bluff land terrain (Blann, 2000). According to Water Temperature Brook and brown trout are known to survive in water temperatures ranging from 4° to 24° Celsius (C) (Carlson et al., 2007; Stranko et al., 2008), though optimal feeding ranges may fall within a tighter temperature range. Through stream temperature monitoring, studies have identified key factors such as the waters width, depth, velocity, and canopy cover to dictate stream temperature directly (Hastings et al., 2011). Other studies identify climate warming as the largest threat to trout populations, since water warming would reduce the amount of suitable trout habitat (Hastings et al., 2011; Stranko et al., 2008; McKenna et al., 2011; Trout Unlimited, 2011). In a 15 year 3 study of brook trout, stream water temperatures were recorded at higher levels where brook trout were extirpated, compared to streams where they remained (Stranko et al., 2008). Ground water sources have been observed to maintain lower stream water temperatures in Maryland (Stranko et al., 2008), which may also play a key role in the sustainability of trout populations in southeast Minnesota’s spring fed streams. oftentimes a predictor of trout presence (Hudy et al., 2008.) Models using five instream habitat variables along with riparian vegetation have predicted brook trout presence with 79% accuracy (Rashleigh, Parmar, Johnston, and Barber, 2005). Water quality, hydrology, and sediment load can all be significantly impacted by the land use practices within a watershed, catchment, and riparian zone of trout streams (Blann, 2000). Climate Change Stream Geomorphology Based on current trends in climate change, models have been developed to represent possible scenarios of increased temperature (Hastings et al., 2011). One best case scenario where air temperatures increased by 1°C followed by water temperature increased by 0.8°C, resulted in a loss of 7.9% of the brown trout population and a 43.6% loss of the brook trout population (Hastings et al., 2011). Similarly, a model prepared by Flebbe et al. (2006) indicated that an increase of air temperature by 1°C would increase water temperatures by 0.94°C, resulting in a loss of 21.6% of trout habitat in the Appalachians. Trout Unlimited (2011) produced a Conservation Success Index (CSI), which implied that 769 of 819 subwatersheds in the Driftless Area would score a rating of poor should climate change increase air and water temperatures. In addition to climate change affecting water temperature, stream morphology has the ability to dictate water temperatures as well (Moechnig, 2007; Hastings et al., 2011; Vondracek et al., 2005). Width-to-depth ratios have been related to stream temperature and stream sedimentation, pointing to the importance of a narrow and deep stream channel for carrying away substrate and reducing the surface area, which decreases potential sun warming (Vondracek et al., 2005). The gradient of a stream and watershed can also play a role in sediment transport (Vondracek et al., 2005). Stream restoration work by Trout Unlimited has narrowed and deepened stream channel sections to aid in sediment carrying capacity and temperature buffering (Hastings et al., 2011). Management methods for properly grazed riparian areas have been developed to taper steep stream banks, which in the long run will reduce sediment loads during spring flooding events (Moechnig, 2007). Sedimentation McKenna et al. (2011) noted at sites where fewer brook trout were observed than their land use model predicted, sedimentation and turbidity was greater than sites where brook trout abundance was what the model had predicted. As cited in McKenna et al. (2011), Marshall and Crowder, 1996; Nislow and Lowe, 2003; Curry and MacNeill, 2004; and Kocovsky and Stream Conditions Stream conditions play a significant role in the overall species abundance and are 4 Carline, 2006, determined high levels of sedimentation to be unfavorable habitat conditions for brook trout. Vondracek et al. (2005) suggest the establishment of permanent and contiguous grassy and wooded sections in a riparian zone to be the best method to decrease sediment entering a stream system. competition has likely restricted brook trout in southeast Minnesota to inhabiting stretches of stream where brown trout compete for habitat (McKenna et al., 2011). Hudy et al. (2008) state the invasion of brown trout to streams where brook trout exist may offset improved land use practices expected to preserve brook trout populations. Of the 73 streams in southeast Minnesota where wild brook trout populations exist, only 17 are currently reported to be free from competition of non-native brown trout (MNDNR, 2011). Habitat Improvements Stream restoration efforts have included channel depth and width reconstruction, habitat bunkers, bank modifications, riffle and pool establishment, and other key instream improvements (Hastings et al., 2011). As pointed out by Vondracek et al., (2005), in-stream improvements on trout habitat should not overshadow the longterm problems of land use within a stream riparian zone and catchment. Proper vegetative buffering to avoid the introduction of excess sediment and allow for shading helps a stream maintain suitable water temperatures and quality for trout and other cold water fish (Stranko et al., 2005; Hasting et al., 2011; Hudy et al., 2008; Blann, 2000). Summary Land use practices at a riparian and catchment level have immense impact on the geomorphology and species presence of a stream (Stranko et al., 2008; McKenna et al., 2011; Vondracek et al., 2005; Hastings et al., 2011; Blann, 2000). Climate change models have predicted increases in both air and water temperatures, resulting in the loss of suitable trout habitat (Hastings et al., 2011; Stranlo et al., 2008; Flebbe et al., 2006). Brook trout are more sensitive to water quality and temperature than brown trout, and are therefore more likely to be limited by these qualities (Stranko et al., 2008 Carlson et al., 2007). In certain areas competition with brown trout displaced and decreased native brook trout populations (Hudy et al., 2008). In southeast Minnesota there are only 23.3% (17 of 73) of streams where wild brook trout populations exist, but brown trout have not been reported (MNDNR, 2011). Competition between Native Brook Trout and Introduced Brown Trout A well-vegetated riparian zone has been more positively associated to healthy brook trout populations than the more adaptable brown trout (Vondracek et al., 2005). Competition between brook and brown trout occurs in several ways. Studies have indicated that non-native trout species usually grow faster in streams where they co-exist with native brook trout (Carlson et al., 2007). Flebbe et al. (2006) suggests competition for reproductive habitat between native and non-native trout becomes a concern when climate changes occur. Habitat References Blann, K., 2000. Catchment and Riparian Scale Influences on Coldwater Streams and Stream Fish in Southeast 5 Minnesota. Graduate School Thesis for University of Minnesota, 1-116. Retrieved January 26, 2012 from Steve Klotz by e-mail. Carlson, S. M., Hendry, A., and Letchers, B. 2007. Growth Rate differences Between Native Brook Trout and Nonnative Brown Trout. Journal of Fish Biology, 71, 1430-1447. Retrieved January 26, 2012 from Science Direct database. Flebbe, A. P. 2006. Spatial Modeling to Project Southern Appalachian Trout Distribution in a Warmer Climate. Transactions of the American Fisheries Society, 135, 1371-1382. Retrieved January 26, 2012 from Science Direct database. Hastings, J., Johnson, K., and Mitro, M. 2011. TUDARE Stream Monitoring Protocols for Evaluating Stream Restoration Benefits, Including Resilience to Climate Change. Wisconsin Department of Natural Resources and TUDARE. September 2011, 1-53. Retrieved from Jeff Hastings through e-mail February 2, 2012. Hudy, M., Thieling, T., Gillespie, N., and Smith, E. 2008. Distribution, Status, and Land Use Characteristics of Subwatersheds within the Native Range of Brook Trout in the Eastern United States. North American Journal of Fisheries Management, 28, 10691085. Retrieved from Anne Timm, USFS, February 2, 2012. McKenna, J. Jr., and Johnson, J. 2011. Landscape Models of Brook Trout Abundance and Distribution in Lotic Habitat with Field Validation. North Americam Journal of Fisheries Management, 31, 742-756. Retrieved from John Hoxmier, MNDNR, through e-mail February 7, 2012. Mitro, M., Lyons, J., and Sharma, S. 2011. Wisconsin Initiative on Climate Change Impacts: Cold Water Fish and Fisheries Working Group Report. 131. Retrieved February 28, 2012 from Google Scholar. Moechnig, H. 2007. Managing Grazing in Stream Corridors. Minnesota Department of Agriculture. 1-31. Retrieved from TUDARE symposium March, 2011. Minnesota Department of Natural Resources. (MNDNR) 2005. Trout Angling Opportunities in Southern Minnesota. State of Minnesota, Department of Natural Resources, 148. Retrieved at Mills Fleet Farm, 2005. Minnesota Department of Natural Resources. (MNDNR) 2011. Trout Angling Opportunities in Southern and Central Minnesota. State of Minnesota, Department of Natural Resources, 168. Retrieved at Westend Bait Shop, Winona, MN, 2011. Newcombe, C., and Jensen, J. 1996. Channel Suspended Sediment and Fisheries: A synthesis for Quantitative Assessment of Risk and Impact. North American Journal of Fisheries Management, 16, 693-727. Retrieved from Google database, February 28, 2012. Rashleigh, B., Parmar, R., Johnston, J., and Barber, M. 2005. Predictive Habitat Models for the Occurrence of Stream Fishes in the Mid-Atlantic Highlands. North American Journal of Fisheries Management, 25, 1336-1366. Retrieved from Web of Science, February 28, 2012. Stranko, S.A., Hilderbrand, R., Morgan II, R., Staley, M., Becker, A., RoseberryLincoln, A., Perry, E., and Jacobson, P. 2008. Brook Trout Declines with Land Cover and Temperature Changes 6 in Maryland. North American Journal of Fisheries Management, 28, 12231232. Retrieved from Anne Timm, USFS, by e-mail Feb 2, 2012. Trout Unlimited. 2011. CSI Driftless Area Brook Trout. Trout Unlimited. Retrieved from Steve Klotz, MNDNR, by e-mail on February 8, 2012. Vondracek, B., Blann, K., Cox, C., Nerbonne, J., Mumford, K., Nerbonne, B., Sovell, L., and Zimmerman, J. 2005. Land Use, Spatial Scale, and Stream Systaes: Lessons from an Agricultural Region. Environmental Management, 36, 775-791. Retrieved from John Hoxmier by e-mail February 7, 2012. 7