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Species of Concern: Coaster Brook Trout

Decision Analysis for Evaluation of Coaster Brook Trout for Federal Listing Pursuant to the Endangered Species Act of 1973


Below are the "Purpose" and "Background" sections, click here for a PDF file of the complete 77-page Decision Document.


Primary Author: Jennifer Szymanski


Jessica Hogrefe, Henry Quinlan, and TJ Miller provided extensive review and comment.


Portions of the document were taken directly from the petition finding, which was written by the Coaster Status Assessment Team and Jesse Wild (USFWS Washington Office).


Coaster Status Assessment Team: Jessica Hogrefe (USFWS Region 3), Henry Quinlan (USFWS Region 3), TJ Miller (USFWS Region 3), Bill Ardren (USFWS Region 5), Mark Brouder
(USFWS Region 3), and Jennifer Szymanski (USFWS Region 3).


The purpose of this document is to describe and explain the various decisions that were made in reaching our May 19, 2009 finding on the petition to list the coaster brook trout (Salvelinus fontinalis) as endangered under the ESA. This document describes our biological considerations, policy interpretations, and legal precedents that we used in arriving at this finding. This document further outlines our decision making process, including our objectives, alternatives, and sources of uncertainty.


The U.S. Fish and Wildlife Service (Service) was petitioned to list the coaster brook trout pursuant to the Endangered Species Act of 1973, as amended (ESA) in 2006. In March 2008, a positive 90-day finding was published indicating that the petition and the information contained within Service’s files suggest that the petitioned action warrants further evaluation. With this finding, the Service then must determine whether coaster brook trout warrants Federal protection under the ESA.


Listing decisions are made by the Service as a whole, with the Director as the final decision making authority. The status assessment and all associated analyses are performed by either the field or regional office. Based on that analysis, the status assessment team then makes a recommendation on the listing decision to the Regional Director. Once approved by the Regional Director, the recommendation is then forwarded on to the Washington Office for further analysis, formatting, and editing. Once this process is complete, the Director then signs the document, making it a final agency decision. The decision is then made public via publication in the Federal Register.


Legal Context - The Endangered Species Act of 1973 defines endangered as “any species that is in danger of extinction,” and threatened as “any species likely to become endangered in the foreseeable future.” The term species is broadly defined as “any species, subspecies, or distinction population segment of a vertebrate species…” A distinct population segment (DPS) is defined in policy as a population segment that is discrete from other individuals of the species, and significant to the taxon. Regardless of taxonomic status, in practice, listed entities are afforded the same protections. By regulation, threatened entities are afforded the same protection Coaster Brook Trout 12-Month Finding Decsion Document 2 as endangered unless otherwise noted via a section 4(d) rule. In determining whether an entity is entitled to the protection of the ESA, the Service must first determine whether the entity qualifies as a “species,” and if so, whether it is endangered or threatened as defined by the ESA.


Biological Context – The historical range of native brook trout extends along Hudson Bay across the Provinces of Nova Scotia, Quebec, and Ontario in Canada, and from eastern Iowa through Wisconsin and the Great Lakes drainage, through the New England states south to Cape Cod, the Hudson River, Connecticut River and other large New England rivers and in coldwater streams of the Appalachian Mountains south to Georgia in the U.S. Brook trout, like most other salmonids1 exhibits multiple life history forms: fluvial (stream resident), adfluvial (freshwater lake migrant), lacustrine (lake-dwelling resident), and anadromous (salt-water migrant). The listing petition addressed a specific life form of brook trout known as coasters. The coaster brook trout is defined as “a brook trout that spends all or a portion of its lifecycle in the Great Lakes.” Coasters represent the adfluvial and lacustrine life forms of brook trout that occupy the nearshore waters of the Great Lakes. The adfluvial form migrates from the lake into tributaries for spawning and the lacustrine life form completes its entire life cycle within the lake (Huckins et al. 2008). Coasters are not, therefore, a species or subspecies, or even a population unit in the traditional sense, but rather they are two types of life history forms of brook trout that occur within the Great Lakes.


Coasters have been long recognized as unique life forms by local, scientific, and regulatory communities. In “Fishes of Wisconsin,” Becker (1983) described coasters as brook trout that spend part of their life in the Great Lakes, but annals are replete with descriptions of fishermen catching lake-dwelling brook trout of record sizes, weights, and longevities long before then (Roosevelt 1884, Behnke 1994). Coasters were a prized game fish in the late 1800s and early 1900s, and the world’s largest brook captured was a coaster. Historically, coasters occupied 116+ populations distributed in Lakes Superior, Michigan and Huron (Bailey and Smith 1981, Dehring and Krueger 1985, Enterline 2000, MIDNR 2008). Today, coasters persist in 16 populations in Lake Superior; 4 of these occur within U.S. waters. Because of drastic declines in numbers and distribution, an international, multi-agency effort began formally in 1993 with the establishment of a brook trout sub-committee of the Lake Superior Technical Committee (Great Lakes Fishery Commission). The sub-committee led development of a brook trout rehabilitation plan for Lake Superior. The goal of the plan is to maintain widely distributed, self-sustaining populations of brook trout throughout their original habitats in Lake Superior (Newman et al. 2003).


Decision Problem - In simplest terms, the task before us is to decide whether the coaster brook trout warrants protection under the ESA. We were petitioned to list the coaster brook trout throughout its native range in the coterminous U.S., and if not warranted, then to list the Salmon Trout River population of coaster brook trout.

The first step in this decision is determining whether the coaster brook trout is a listable entity pursuant to the ESA. There are three listable entities under the ESA: species, subspecies, and DPS. Coaster brook trout is not a species or subspecies but rather it is a life history form of brook trout that occurs within the Upper Great Lakes. We were petitioned to list the coaster brook trout throughout its historical range in the U.S., or if not warranted, then to list the coaster brook trout within the Salmon Trout River. For a 12-month finding, we are not limited to the petitioned entity. We could look solely at the petitioned entity (coaster brook trout) or we may elect to look at it more broadly (e.g., Eastern brook trout). Given this and the taxonomic status of coasters, there are two possible listable entities: species (eastern brook trout) and a DPS (a subset of the eastern brook trout range that includes coasters). Very early on in our decision process, however, we determined a species level evaluation would not be prudent given the wide range, the great number of seemingly viable populations distributed across its range, and the time constraints associated with a 12-month review. Thus, we focused on the DPS as our listable entity.


Our 1996 Policy on Distinct Population Segments (61 FR 4722: February 7, 1996) states that an admissible distinct population segment is one that is discrete and significant. A population segment may be considered discrete if it satisfies either one of the following conditions. One, it is markedly separate from other populations of the same taxon as a consequence of physical, physiological, ecological, or behavioral factors. Two, it is delimited by international governmental boundaries within which differences in control of exploitation, management of habitat, conservation status, or regulatory mechanisms exist that are significant in light of section 4(a)(1)(D) of the ESA. The purpose of the discrete standard is to require that an entity be adequately defined and described. The standard adopted does not require absolute separation of a DPS from other members of its species as this can rarely be demonstrated in nature for any population of organisms. The standard adopted allows for some limited interchange among population segments considered to be discrete, so that loss of an interstitial population could well have consequences for gene flow and demographic stability of a species as a whole.


If we determine that a population segment is discrete, we then consider its biological and ecological significance to the larger taxon to which it belongs. This consideration may include, but is not limited to: (1) evidence of the persistence of the discrete population segment in an ecological setting that is unique for the taxon; (2) evidence that loss of the population segment would result in a significant gap in the range of the taxon; (3) evidence that the population segment represents the only surviving natural occurrence of a taxon that may be more abundant elsewhere as an introduced population outside its historical range; and (4) evidence that the discrete population segment differs markedly in its genetic characteristics from other populations of the species. The purpose of the significance standard is to ensure only important elements of a taxon’s genetic and natural diversity are protected.


Owing to these requirements, our decision problem is multi-faceted. First, we need to determine whether there are any admissible DPSs of coaster brook trout. If one or more DPSs are identified, we then need to conclude our 12-month finding and determine whether such DPSs are endangered or threatened2. Lastly, if threatened or endangered, we need to select a single or an array of DPSs to propose for Federal candidate status3. If at any step, we determine that the set of criteria cannot be met, we must conclude “not warranted.”


The ultimate decision maker is the Director of the U.S. Fish and Wildlife Service (Service), but for our purposes, the proximate decision makers are the Region 3 Ecological Services managers: the Chief of Endangered Species and Assistant Regional Director of Ecological Services.



1 Salmonids, as a group, have a complex life history. There are three broad classifications of life history strategies: potamodromy, oceanodromy, and diadromy. Within each of these strategies, there are further divisions (e.g., anadromous, catadromous, fluvial, lacustrine) referred to as life history forms. Some species exhibit one life history form, but many express multiple forms. S. fontinalis expresses potamodromy and diadromy life history strategies although in the majority of its range, it is potamodromous. Within the potamodromous life history strategy, brook trout can be either fluvial (stream-resident), adfluvial (freshwater lake migrant), or lacustrine (lake-resident). See Appendix 1 for further discussion.


2 There are three possible conclusions to a 12-month finding: (1) warranted: the species warrants listing; begins the process of adding the species to the list of threatened and endangered species; (2) warranted, but precluded: thespecies warrants listing, but that listing is precluded by other higher priority listing actions; species becomes a
candidate for listing; (3) not warranted: the species does not warrant listing at this time; ends the listing process.


3 We prioritize species for potential listing according to their Listing Priority Number (LPN), which is based on the magnitude and immediacy of threats along with taxonomic status (e.g., species, subspecies). Under our current listing prioritization process, the highest possible LPN for a DPS is 3. This makes other listing actions with LPNs of 1 and 2 as higher priorities. Based on current funding and staffing levels, we are only able to process only listing actions with LPNs of 1 or 2 at this time. Thus, if we come to a ‘warranted’ determination, it would necessarily be ‘precluded’ due to our other higher priority listing actions.


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Last updated: February 10, 2016