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

estoration objective by natural recolonization; it uses a range of starting population
sizes and intrinsic rates of increase from one generation to the next (Table 1). The
model indicates that achieving Measure 7.1 (633,300 adult shad returns in 35-40 years)
by natural recolonization would require either a very high rate of increase for a
prolonged period or a very large starting population. For example, this target could be
reached with a starting population of 2500-5000 fish that on average doubled in
abundance every five years. This level of reproduction might be expected in bacteria,
but not in shad. If the rate of reproduction is reduced to 1.5 or 1.25, the size of the
starting population would have to be 40,000 to 135,000 fish. DMR is not aware of shad
populations in Maine or elsewhere that consistently are achieving these levels of
reproduction; remnant populations on the east coast that have been greater than about
1000 fish; or any large river restoration that has been accomplished by natural
recolonization. DMR has concluded that reliance on natural recolonization is not a valid
management strategy.
DMR next modeled restoration at two fry stocking levels (Table 2). The model
assumes one adult return for each 318 hatchery fry released and 100 adult returns for
each 86 spawning adults (reproduction rate = 1.1627907) based on data presented in
Restoration of American Shad to the Susquehanna River: Annual Progress Report
2000. For simplicity the model assumes a starting population of 0 and no repeat
spawning. While reformatting the model for presentation, DMR discovered an error in
its original calculations. The corrected model indicates that fry stocking would have to
continue for a longer period of time than originally reported, and that the higher stocking
rates are needed to achieve the shad restoration objective.
DMR considered the consequences of the recommendation made by USFWS and
NOAA to delay an active restoration program. Delaying activity for at least five years
would make it more difficult to reach the achievable population target of 633,000 fish in
50 years. There is no guarantee that the private Waldoboro Hatchery would be
available to produce shad after a five-year hiatus, and there currently are no other
hatcheries in New England with the capacity or capability of producing 12 million shad
fry. In addition, the proposed schedule for testing passage effectiveness at mainstem
dams for multiple species and making improvements at a single time would be
jeopardized. DMR has determined that delaying active restoration carries too great a
risk for the restoration.
The State and federal agencies have not come to agreement about the source of
broodstock that would be used to produce hatchery-reared fry. Potential sources of
1200 adult shad remain as limited as they were when the Strategic Plan to Restore
American Shad (Alosa sapidissima) to the Penobscot River, Maine was completed in
2001. NOAA has recommended an extensive comparison of biological characteristics
(e.g. degree of iteroparity, age at maturity, duration of freshwater rearing, migration
distance to spawning ground) of stocks within 500 miles of the Penobscot. We believe
this recommendation is unrealistic. DMR’s experience is that minimum mortality occurs
if total transport time of adult shad broodstock is 3 hours or less, and that mortality
significantly increases, especially for large females, when total transport time is 5 hours
or more. The Operational Plan compares potential broodstock sources in the Gulf of
Maine with a maximum transport time of 5 hours (Table 3). The Merrimack is the only
population that can provide sufficient broodstock with certainty.
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