Potential impacts of climate change on brook trout (Salvelinus fontinalis) populations in streams draining the Laurel Hill in Pennsylvania

Abstract

To establish a baseline for assessment of climate change effects on populations of brook trout (Salvelinus fontinalis) in southwestern Pennsylvania, we surveyed a collective of headwater streams for fish population status and the development of annual air and stream temperature profiles. The 20 streams selected, 10 located on each facing slope of an anticlinal fold on the Appalachian Plateau, Laurel Hill, historically supported self-sustaining brook trout populations. In these watersheds, anthropogenic activity was minimal and riparian canopy intact. Three, from each facing slope along with the cool-water receiving stream for the respective tributary network, received riparian air and in-stream temperature data loggers. Data loggers were retrieved after one calendar year and temperature profiles for all eight streams downloaded. From these, we analyzed the air/stream temperature relationship for the calendar year and during the growing season for each headwater stream. Wild brook trout were present in all streams along with mottled sculpins (Cottus bairdi) and occasional representatives of six other species. Streams varied in the number of days experiencing thermal stress for brook trout (>18 C) ranging from a minimum of 0 to a maximum of 67, and the slope of each individual air/in-stream temperature relationship correlated with temporal stress. Local differences in riparian cover and groundwater inputs appear to be responsible for the deviation from climate model predictions and suggest resiliency in these headwater ecosystems. Of more immediate concern is the potential for the interruption of connectivity among tributary networks. Thermal profiles of the cool-water receiving streams revealed air temperature as a strong correlate of in-stream temperature. A warming climate may progressively constrict these avenues of gene flow among resident brook trout tributary populations leading eventually to their genetic isolation.

Expert opinion on the status and stressors of brook trout, Salvelinus fontinalis, in Ontario

“…Expert opinion often varies at multiple scales. For example, climate change is a global issue (Argent & Kimmel, 2013;Regier & Meisner, 1990), which could have drastic effects on the distribution and survival of brook trout in Ontario (Chu, Jones, Mandrak, Piggott, & Minns, 2008;Chu, Mandrak, & Minns, 2005 Conclusions from this study are that brook trout populations are perceived to be imperilled in parts of the province, much of which has been associated with urbanisation within the watersheds of southern Ontario.…”

“…Expert opinion often varies at multiple scales. For example, climate change is a global issue (Argent & Kimmel, ; Regier & Meisner, ), which could have drastic effects on the distribution and survival of brook trout in Ontario (Chu, Jones, Mandrak, Piggott, & Minns, ; Chu, Mandrak, & Minns, ). Expert opinion varied dramatically among waterbody types and FMZs, such that climate change was not considered a primary contemporary stressor to brook trout.…”

“…For example, brook trout in the Lake Ontario tributaries is believed to have been reduced to approximately 21% of its historical distribution and is confined to the headwaters (Stanfield, Gibson, & Borwick, 2006), and only remnant population of coaster brook trout remain in the Great Lakes (Huckins, Baker, Fausch, & Leonard, 2008;Mucha & MacKereth, 2008). Causes for decline are varied and include, but not necessarily independently, exploitation (Huckins et al, 2008;Marschall & Crowder, 1996;Post et al, 2002), habitat degradation (Hudy et al, 2008;Mucha & MacKereth, 2008;Post et al, 2002), adverse impacts from agriculture (DeWeber & Wagner, 2014;Power, 1980), forestry (Kanno, Letcher, Rosner, O'Neal, & Nislow, 2015;Power, 1980), urbanisation (Stanfield et al, 2006;Stanfield & Kilgour, 2013) and land-use practices (Barton et al, 1985;Hudy et al, 2008;Stranko et al, 2008), fragmentation or water flow manipulation from dams or barriers (Power, 1980;Whiteley et al, 2013), species introductions including other salmonids (Ridgway, 2008) or invasive species (Kanno, Kulp, & Moore, 2016;Marschall & Crowder, 1996;Mitro, 2016), water quality (Marschall & Crowder, 1996;Power, 1980) and climate change (Argent & Kimmel, 2013;Regier & Meisner, 1990).…”

Predicting fine‐scale distributions of peripheral aquatic species in headwater streams

“…Each of our final models included climate and land cover variables that could be manipulated to build what-if scenarios. Due to long-term changes in water temperature and flow resulting from climate change, distributions of some salmonids, including brook trout, are expected to become even more constrained and fragmented (Haak et al 2010;Isaak et al 2010;Wenger et al 2011) until only fragile populations remain in small headwater stream thermal refuges (Flebbe et al 2006;Haak et al 2010;Argent and Kimmel 2013;Whiteley et al 2013;Trumbo et al 2014). Roberts et al (2009) found that the replacement of hemlock overstory with hardwood species in the Great Smoky Mountains National Park will have a negligible effect on long-term stream conditions, but impacts from the transition period from hemlock to hardwoods are likely to be significant.…”

Genetic Assessment Reveals Population Fragmentation and Inbreeding in Populations of Brook Trout in the Laurel Hill of Pennsylvania

“…), climate change (Meisner ; Flebbe et al. ; Argent and Kimmel ), and competition with nonnative species (King ; Flebbe ; Guffey ). The Eastern Brook Trout Joint Venture (EBTJV ) classified Brook Trout as extirpated in 41% of the subwatersheds examined, while another 51% of subwatersheds were found to have lost a significant portion of Brook Trout habitat.…”