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Posted January 11, 2000

Assessing Genetic Distinctiveness of Wild Maine Atlantic Salmon

By Irving Kornfield, Professor of Zoology

Federal agencies have proposed protecting wild Maine Atlantic salmon as a "distinct population segment." To qualify for listing, salmon must be shown to be a discrete segment of the population and be significant component of the species. Naturally reproducing salmon in Maine's Downeast rivers possess characteristics that distinguish them from those in the Canadian Maritimes. However, it is not clear whether these differences arise from genetic or environmental causes. Further, past restocking efforts of salmon in Maine rivers has clouded the significance of any distinctiveness. There is considerable scientific debate concerning the data upon which the federal government is relying in this proposed rule. Therefore, rigorous, evaluation by external scientists is required.

The Basis of Endangered Species Act Listing . . .

The National Marine Fisheries Service and the Fish and Wildlife Service decided not to list the Atlantic salmon as a threatened species in March, 1995. At that time they concluded that the available biological evidence indicated that Atlantic salmon did not meet the definition of species under the Endangered Species Act (ESA) and therefore concluded that the action to list was not warranted. However, in September, 1995 the services proposed to list salmon in seven rivers as a threatened Distinct Population Segment (DPS) under the ESA. In December, 1997, the services withdrew their proposed rule, finding that the Gulf of Maine DPS was not likely to be come endangered in the foreseeable future, and thus, an ESA listing was not warranted.

As part of the debate during that period, I served as chair of the Genetics Committee of the Governor's Atlantic Salmon Task Force. The findings of that Committee were that formal listing of salmon in these rivers was not justified on the basis of the scientific information presented in the proposed rule because: (1) the magnitude of past stocking of Maine rivers of salmon of synthetic origin facilitated introgression and eliminated local variability, and (2) current natural reproduction was likely that of offspring from hatchery fish rather than from "native" strains. In November, 1999, the federal services proposed a rule to list the Atlantic salmon as endangered. This proposed rule recognized a Gulf of Maine DPS to include all naturally reproducing wild populations of Atlantic salmon having historical river-specific characteristics.

To qualify for this ESA listing, the fish must be recognized as constituting a "distinct population segment" of the species. To be considered as a DPS, there are two critical elements that need to be demonstrated: (1) the discreteness of the population segment in relation to the rest of the species, and (2) the significance of the population segment to the species. To qualify as discrete, the population segment must satisfy one of two conditions: it must be markedly separated from other populations as a consequence of ecological, behavioral or other biological factors, and/or be managed differently across international boundaries To qualify as significant, the population segment must be different such that its loss would change the geographic distribution of the species, or it must differ in some unique way, such as in its genetic characteristics. In other words, these units must be demonstrated to be reproductively isolated. Based largely on data generated by genetic studies from a federal laboratory, the services have concluded that Atlantic salmon in many of the rivers emptying into the Gulf of Maine meet these criteria, and thus, should be protected.

Complicating Factors . . .

Evaluation of the information used to infer significance is open to debate. The genetic data necessary to independently review the federal finding have not been made available. One significant confounding issue is the impact of past stocking history of the species. Maine's rivers have been stocked with salmon for well over 100 years. However, salmon returns to these rivers have been irregular, and it is unclear whether stocked fish have returned in biologically significant numbers. While services conclude that the overall effect of past stocking efforts on wild salmon is minor, the extent and duration of this activity may have significantly altered the basic genetic composition of the fish such that they retain little of the original, native genetic structure. DNA analyses, similar to that used in forensics analysis, can address this question. Such studies are required and some are in progress at the University of Maine and elsewhere.

The services asserted that there are several biological characteristics associated with Maine fish, such as timing of reproduction, that distinguish them from salmon in other areas. However, variation in such attributes is controlled by both environmental and genetic influences. Thus, such differences need not reflect fundamental discreteness, a requirement for DPS status.

A final complication is that there is no scientific yard-stick which provides a threshold value for how genetically "unique" a population must be for it to be considered significant for ESA listing.

In sum, in light of the considerable scientific controversies outlined above, a rigorous independent, external scientific evaluation of the data is required.

For further information feel free to contact:

Irv Kornfield, Professor of Zoology, 207-581-2548, IrvK@umit.maine.edu

Dr. Irv Kornfield is a professor at the University of Maine with a Ph.D. in ecology and evolution. His research interests are population biology and molecular systematics. Dr. Kornfield's research is supported by the National Science Foundation, UM/UNH Sea Grant, the State of Maine (Dept. of Inland Fisheries and Wildlife), and the Maine Aquaculture Innovation Center.

If you would like to receive addition copies of this white paper or any other papers in the series, please contact:

Judith Round, College of Natural Sciences, Forestry, and Agriculture, University of Maine, 5782 Winslow Hall, Orono, Maine 04469-5782

Telephone: (207) 581-3229; E-Mail: judy.round@umit.maine.edu

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