Operational Plan for the Restoration of Diadromous Fishes to the ...

Genetic studies focused on alewife differentiation using mtDNA and microsatellite
data and often compared anadromous and landlocked forms. This section focuses
on the results for the anadromous form. Palkovac et al. (2008) found seven
anadromous populations in the Connecticut River were generally weakly
differentiated from each other using mtDNA and microsatellite data (mean FST=0.038
and 0.012, respectively) and that gene flow (Nm=3.11) did not appear to be restricted
at the geographic scale of the study (80 km between the most distant population).
Chilakamarri (2005) used microsatellite data to examine two populations of
anadromous alewife in Connecticut separated by about 40 km. She found a
moderate level of differentiation between the two populations (pairwise FST=0.058).
Using microsatellite data, Bentzen and Paterson (2005) compared the two
anadromous alewife populations in the Saint Croix River with populations in the
LaHave and Gaspereau Rivers. Anadromous populations were generally weakly
differentiated from each other within Saint Croix River (pairwise FST=0.008), weakly
to moderately differentiated between the Saint Croix and the LaHave and
Gaspereau River populations (pairwise FST ranged between 0.014 and 0.044), and
moderately differentiated between the LaHave and Gaspereau Rivers (FST =0.050)
This result is notable since the Saint Croix River was separated from the other rivers
by hundreds of kilometers. Bentzen (personal communication, December 3, 2008)
noted that the data indicate that alewife populations are genetically differentiated but
that the pattern and magnitude needed to be determined through additional study.
Several genetic studies show that introduced landlocked alewife populations are
very greatly differentiated from anadromous populations, suggests that the
introductions may have occurred in recent times, and demonstrate a certain amount
of resilience of alewife life history through these successful introductions. Bentzen
and Paterson (2006) concluded that the landlocked alewives in the St. Croix
watershed did not arise from the sampled anadromous population but rather a
separate introduction. Palkovac et al. (2008) suggested that landlocked populations
from seven Connecticut lakes diverged from a common anadromous ancestor no
longer than 5,000 years ago and as recently as 300 years ago. Ihssen and Martin
(1992) concluded that the Great Lake population of alewife is a recent invader that
likely originated form the Hudson-Mohawk Rivers via the Erie Canal and the New
York Finger Lakes. These accounts are notable in that they suggest that the
successful invasions may be recent (within the period of European settlement).
Numerous other alewife introductions have also been documented in lakes and
ponds of the New England and Mid-Atlantic states (Hendricks 2003).
Management Experience
The ASMFC is revising its management plan for alewife based upon closure of river
herring fisheries by many Atlantic coastal states and observed declines in
abundances (ASMFS 2008a, ASMFS 2007a). The plan recognizes that fish
transfers may be necessary to reestablish populations that have been extirpated
from their habitat due to dams or other factors. Fish transfers and hatchery
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