Petition to List Lynn Canal Pacific Herring under the Endangered ...

D. Significance
Under the DPS Policy, once a population has been determined to be discrete, the
NMFS must then consider whether the population is significant to the taxon to which it
belongs. The DPS policy states that a population may be considered significant based on,
but not limited to, the following factors:
1) Persistence of the discrete population segment in an ecological setting unusual or
unique for the taxon,
2) Evidence that loss of the discrete population segment would result in a significant
gap in the range of a taxon,
3) Evidence that the discrete population segment represents the only surviving
natural occurrence of a taxon that may be more abundant elsewhere as an
introduced population outside its historic range, or
4) Evidence that the discrete population segment differs markedly from other
populations of the species in its genetic characteristics.
Because precise circumstances are likely to vary considerably from case to case, it
is not possible to describe prospectively all the classes of information that might
bear on the biological and ecological importance of a discrete population segment.
(USFWS-NMFS 1996).
Lynn Canal Herring are significant to the taxon based on seven factors detailed
below: 1) Unique ecological setting, 2) Significant gap in range, 3) Marked differences in
genetic characteristics, 4) Ecosystem significance, 5) Evolutionary potential, 6) Marginal
populations, and 7) Cultural significance.
1. Unique Ecological Setting
The Lynn Canal Herring population occupies a unique ecological setting that may
translate into adaptive potential for the Pacific Herring species. Overall salinity levels
may be much lower in Lynn Canal than in other regions of Southeast Alaska because of
the isolated nature of the inlets and bays, and the significant inputs of freshwater from
glaciers and rivers. Salinity levels have been correlated with genetic differentiation in
Atlantic Herring (Bekkevold et al. 2005).
Baltic herring spawn in coastal low salinity habitats where larval retention is high
due to limited large-scale hydrographical activity (Lehmann et al. 2002) and
therefore developing larvae have high probability of experiencing a predictable
environment. Across the North Sea–Baltic Sea transition zone spatially variable
but locally predictable environmental conditions suggest that herring from
different spawning locations experience stabilizing selection for different salinity
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