Throughout their native range, eastern brook trout populations are in decline. Scientists cite a number of reasons for the phenomenon, including habitat loss, human encroachment, overfishing, invasive species, poor water quality, runoff, acid precipitation, acid mine drainage, and other contaminants.
A number of scientific studies have indicated that brook trout and other salmonoid species experience a much higher mortality rate when anglers fish with baits vs. artificial lures. The high mortality rates that occur with baits usually stem from gut-hooking.
In Maryland, the Maryland Biological Stream Survey (MBSS), an ongoing assessment of the state’s streams revealed regarding brook trout behavior. Surveys found that brook trout populations decreased when human structures such as roof tops and paving were present.
The link between human activity and the decline of wild trout is complex. Although the exact cause is not known, one possibility is that paving, buildings, and other structures combine to raise stream temperatures which affect nearby brook trout populations. Eastern brook trout cannot survive in streams where temperatures exceed 70 degrees F for extended periods.
Scientific studies have shown that a number of factors can contribute to stream warming. Headwater ponds and impoundments are known to adversely affect stream temperatures. When a pond is built in-line with a stream, the surface water of the pond warms. As the water re-enters the stream it increases the stream temperature below the pond. This condition is known as a thermal impact.
In addition to raising stream temperatures, dams can restrict or totally block fish passage. In some areas, networks of dams restrict fish passage along entire watersheds. These range from modern day flood control projects to obsolete mill ponds that may have been abandoned for centuries. Culverts can also act as barriers to fish passage.
In many streams, brook trout often face competition from non-native brown trout, rainbow trout, and other species. Similar threats occur in northern lakes where non-native fish have been introduced. Invasive microorganisms also threaten brook trout populations, including didymo and whirling disease.
In southern Appalachian streams, brook trout have declined sharply due to the effects of logging, sedimentation, the introduction of non-native trout, and other changes.
In response to brook trout declines, several states have implemented restoration plans:
For decades, the Commonwealth of Pennsylvania has studied brook trout within its borders. According to Pennsylvania’s Brook Trout Conservation Strategies, more than 5,000 miles of wild brook trout streams exist within the state. The state brook trout plan includes efforts to maintain and restore habitat, monitor fish populations, reduce pollution, educate anglers, and other plans.
In 2006 the Maryland Department of Natural Resources (DNR) listed brook trout as a “Species in Greatest Need of Conservation” leading to the development of a brook trout Fisheries Management Plan. The state has since implemented trout habitat restoration projects, invasive species control programs, and other efforts.
Brook trout restoration has also been addressed by national and regional efforts. The Eastern Brook Trout Joint Venture utilizes a cooperative strategy to help sustain healthy, fishable, brook trout populations from Maine to Georgia.
Another organization, the National Fish Habitat Partnership focuses on conserving and restoring fish habitats throughout the U.S., leveraging federal, state, and private funding sources.