Brook Trout in a Changing World
Rhode Island Freshwater Fishing
Corey Pelletier, Fisheries Biologist
In modern day, many of our ecological communities are struggling to survive and adapt to changing environmental conditions. Occurring from a local to global scale, a host of threats are impacting unique and sensitive habitats, causing detrimental effects. Many questions in ecology and biology are now pointed at determining and measuring the impact of climate change. Development also plays a compounding role in impact to the environment and ecological communities. Furthermore, the question of how to approach and mitigate the impacts created by a changing environment remains even more complex.
Climate change and development are as present in Rhode Island as in the rest of the nation. Both aquatic and terrestrial ecosystems have and continue to be impacted. Focusing on a single species that has an intrinsic value to both people and ecological communities in the northeastern US, the eastern brook trout (Salvelinus fontinalis) is at the forefront of impact by climate change and development. As a native species to the northeastern US, including Rhode Island, the brook trout is a coldwater species that requires high standard of water quality for survival. In 2015, RIDEM’s Fish and Wildlife Division released an updated Wildlife Action Plan (RIWAP). This plan identifies a comprehensive strategic plan for wildlife conservation and species of greatest conservation need (SGCN) within the state. Brook trout are one of many freshwater species listed as a SGCN due to a variety of threats to habitat.
Brook trout require a fairly specific set of water quality characteristics in order for survival. Most importantly, clean and cold water are a baseline necessity. Along with cold water, high levels of dissolved oxygen must be present. Typically wild brook trout are found in waters that remain below 68 degrees Fahrenheit year round. Generally, these trout are found in small to medium sized streams that contain significant cover and structure provided by boulders, woody debris, and undercut banks. The ideal habitat tends to be small headwater streams that are fed by groundwater and natural springs where conditions are suitable for few other fish species. Brook trout act as an excellent indicator species for stream quality due to their sensitivity to outside threats such as pollution and sedimentation.
There are numerous factors that pose threats to brook trout habitat. In the RIWAP, several threats are identified which are known to cause negative impact to these sensitive habitats. The greatest threat identified in the RIWAP is listed as development and urban areas. Development often increases stormwater runoff which acts as a source of pollution, provides excess sediments into waterbodies and even increases water temperature. Dams remain high on the list of threats by creating a barrier for fish movement as well as increasing water temperature during summer months. Nutrient loading from agricultural runoff, clearcutting of riparian zones along stream corridors, and sewage discharges into freshwater are some of many issues impacting water quality necessary for trout survival. Climate change poses more of a long term impact to brook trout and their native range. Globally, air temperatures are increasing which have a gradual effect on both surface and groundwater temperatures. All of these impacts individually and in combination, present challenges to the survival of our wild brook trout populations.
Actions can be taken at all levels in order to reduce impact to brook trout habitat and preserve this relic species. Action begins with awareness at a broad scale. Protection of our waterbodies and improving water quality is one of the most important ways to protect not only brook trout but all other aquatic and terrestrial species. Simply maintaining a riparian zone by leaving trees and other vegetation along stream banks protects water quality by reducing erosion and sedimentation as well as provides shade to the stream channel. Reduction of impervious surfaces, such as paved driveways and parking lots, is imperative for maintaining brook trout habitat in order to reduce excess runoff and increased potential for erosion and sedimentation. In areas of new development, actions including leaving a proper riparian zone and creating permeable roadways and parking areas may make the difference in the survival of a wild brook trout population. Removal of dams and impassable culvert crossings is essential to creating connectivity between isolated populations. Also, removal of dams often helps to reduce downstream water temperatures during summer months when trout are most susceptible to thermal stressors. As such a sensitive species to impaired environmental conditions, brook trout are an important indicator species to the rest of our aquatic systems which must be protected.
In a changing world where the effects of climate change are becoming ever so present, we must take precautionary measures to preserve and protect our ecological communities and species diversity for generations to come.