Sea Run Brook Trout
Salvelinus fontinalis
Fish illustration used with permission: Copyright 2010 Sea Run Brook Trout Coalition, by artist James Prosek.
Common name: Eastern brook trout, squaretail, speckled trout, brookie, sea-run brook trout, salter
Scientific name: Salvelinus fontinalis
Classification: Brook trout are a type of char, alongside arctic char and lake trout (togue). They are also members of the salmonid family, like Atlantic salmon.
Range: Brook trout are native to eastern North America, from the Great Lakes east to the Atlantic Ocean, and down the Appalachian Mountains as far south as Georgia, where they are found in many high elevation streams. While they are all the same species, there are three distinct types of brook trout. The one most people are familiar with is the “classic” Eastern brook trout, which is the smallest of the three types. The Great Lakes have “coaster” brook trout, and northern New England still has pockets of sea-run or “salter” brook trout.
All brook trout prefer cold water between 50 and 65 degrees, and are most often found in clear, cool, oxygenated streams and lakes, in addition to coastal facing streams and brackish estuaries. In streams, the best conditions include a rocky bottom with no silt, a good mix of pools and riffles, and undercut banks with abundant vegetation and in-stream cover. In lakes and ponds, brook trout tend to inhabit shallow, spring-fed areas less than 15 to 20 feet in depth.
Although brook trout populations are declining across their historic range within the United States, a 2006 range-wide assessment by the Eastern Brook Trout Joint Venture (EBTJV) concluded that "Maine is the only state with extensive intact populations of wild, self-reproducing brook trout in lakes and ponds.”
Identification: The classic brook trout look includes an olive-green back with wavy yellow lines and spots. Along its sides, the brook trout’s color transitions from olive to orange or red, with scattered red spots bordered by pale blue. Its lower fins are orange or red, each with a white streak and a black streak, and its underside is milky white.
The sea-run brook trout, however, might not even look like the same fish at first glance. In salt water, brook trout take on a silvery hue more appropriate for the marine environment, similar to when a salmon parr undergoes smoltification. These brook trout also show a rainbow of paler hues that distinguish them from fish that stay in freshwater. On Mount Desert Island, Stanley Brook salters are purple, green, brown, and silver when they return to freshwater.
Size varies greatly, depending on water temperature, productivity, and available food sources. While individuals that live solely in mountain streams might never grow larger than 7 inches, the statewide average length of 3 year-old brook trout found in Maine lakes is 13.3 inches. These fish tend to weigh between 1 and 5 pounds. Stream populations are typically slower growing than lake populations, with sea-run trout growing the largest due to the abundance of food in the ocean. One account from the 1800s tells of a salter brook trout that weighed 14 pounds!
Life history: Brook trout spawn in the fall and hatching occurs in the following winter/spring, usually between February and April. Spawning occurs at water temperatures of between 40°F and 50°F. Once a male has courted a female, she will dig in the gravel to excavate a shallow hole, or redd, over a groundwater upwelling or the tail of a pool. The male fertilizes the eggs as they are deposited, and the female follows by sweeping gravel back over the eggs. She will likely then move upstream and start again, and eggs may be deposited by one pair of trout over a series of small redds, with total egg numbers ranging from 500-5000. Incubation takes at least 45 days, but longer in colder water. Newly hatched fry remain in the gravel until their yolk sac is absorbed, after which they emerge and live in a shallow area of the stream with low water speeds. When they grow into the juvenile stage, they will move into faster riffle areas.
By the end of their first summer, juvenile brook trout are typically about three to four inches long. They are short-lived; on average, brook trout live to be two to four years old, reaching maturity by their first or second year of life.
Ecological importance: Brook trout are a valuable prey species for many animals, including larger fish, herons, kingfishers, mink, otters, and snapping turtles. Salter brook trout, like any diadromous species, connect freshwater and marine environments by moving nutrients from the sea upstream.
Behavior and diet: What makes certain brook trout decide to take a vacation to the sea is still largely a mystery. No specific genetic markers have been found, and not all brook trout in coastal streams choose to make the trip. Some salters may even choose to overwinter in the ocean, before returning to the freshwater to spawn.
Young brook trout feed on plankton and progress to insects until they are adults. Adult brook trout are extremely opportunistic and eat a variety of insects, often preferring adult and nymph forms of aquatic insects. They will also eat beetles, ants, and small fish when they’re available. Larger brook trout, like the salters, will also feed on other fish or shrimp in addition to insects. In one instance, the National Park Service reported that the stomach of a brook trout contained a subadult 5-lined skink.
Cultural importance: The Maine Department of Inland Fish and Wildlife (MDIFW) estimates that 70% of the state’s 32,000 miles of rivers (and at least 1500 ponds and lakes) have what it takes to support brook trout fisheries. For avid anglers, catching one of Maine’s native brook trout is a bucket list item. These fish not only make for a delicious catch, but are also responsible for a sizable amount of tourism dollars. In 2005, the brook trout was designated a State Heritage Fish. While anglers are allowed to keep some of what they catch, many voluntarily practice catch and release.
Threats: The main threats facing Eastern brook trout are non-native species, habitat impediments, and land development. Brook trout have been eliminated from much of their native range because they are very sensitive to illegal introductions, especially warm water species like bass, muskie, and perch. Other fish that have been intentionally stocked in ponds and streams for fishermen, like brown trout, can be more aggressive than brook trout, and outcompete for resources.
All brook trout, including salters, are harmed by habitat impediments like dams and culverts. These structures block access to spawning grounds, cold refuges during the summer, and migration up and down stream. As land development continues, more streams may be choked underneath roads, and sediment dumped into waterways. Warming waters due to climate change affect their reproduction, and may allow viruses to more easily infect fish.
Restoration efforts: Luckily, brook trout are incredibly resilient in undisturbed habitats. In northern Maine, brook trout can be found in just about any stream with a source of cold water. Minimizing the loss of existing critical habitat is one of the best ways to ensure species survival.
Brook trout in Maine are primarily managed by MDIFW, who are constantly monitoring and evaluating brook trout fisheries across the state. They utilize two primary management strategies for stocking brook trout in Maine: stocking full grown fish for immediate fishing opportunities, and stocking small young fish that will be allowed to grow before being caught. Stocking allows fishing in lakes and ponds that otherwise would not be capable of supporting wild populations. There are also a number of self-sustaining populations of wild brook trout, with length and bag limits that vary based on the population’s characteristics.
However, much remains unknown about sea-run brook trout in the state. Salters are not a commercial species, so their numbers are not tracked closely by the state Department of Marine Resources. It was only recently that brook trout were even added to Maine DMR’s website under the “Do You Know Your Catch” section. Salters haven’t traditionally been of interest to Maine’s Department of Inland Fisheries and Wildlife either, since they focus on freshwater species.
Community action has many times proven to be the driver for salter conservation. 4 years ago in Massachusetts, led by the local Trout Unlimited chapter, residents of Wareham voted no on a proposal to develop the area around the headwaters of Red Brook. Red Brook is one of the last remaining salter brook trout habitats in MA, and has been the site of ongoing restoration for decades. Hopefully, this decision can set a precedent, where choosing to preserve our local natural treasures is commonplace.
Fishery: There is no commercial fishery for brook trout. There is a strong recreation fishery for the species, which includes both natural and stocked populations, which are tracked and managed closely by the MDIFW. In stocked areas, there is also fishing opportunity for hybrids between rainbow trout and other species. For example, when a male brook trout breeds with a female brown trout, their offspring is called a “tiger trout”, and if the female is a lake trout the offspring is called a “splake”. However, details of the salter brook trout fishery is a closely guarded secret, which makes them harder to manage.
Sources:
https://observer-me.com/2021/02/09/news/sea-run-brook-trout-are-maines-least-appreciated-gamefish/
https://www.nwf.org/Educational-Resources/Wildlife-Guide/Fish/Brook-Trout
https://www.maine.gov/ifw/fish-wildlife/fisheries/species-information/brook-trout.html
https://www.maine.gov/ifw/fish-wildlife/fisheries/wild-brook-trout.html
https://vtfishandwildlife.com/learn-more/vermont-critters/fish/brook-trout
https://www.fws.gov/species/brook-trout-salvelinus-fontinalis
https://www.anglersjournal.com/freshwater/from-shore-to-sea
https://hhltmaine.org/12519/nature-notes-brook-trout/
https://www.tu.org/magazine/from-the-president/saving-salters-and-saving-new-england/