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

Subdrainage
0.73
0.72
0.71
0.70
0.69
0.68
0.67
0.66
0.65
0.64
0.63
Current and Future Lambda Values for Penobscot
Subdrainages
Kenduskeag
Lower Penobscot & Passadumkeag
Piscataquis Lower
Piscataquis Upper
Lambda
East Branch Mattawamkeag
Lambda_Current
Lambda_Future
East Branch
Figure 1. Changes in lambda due to cumulative dam effects on survival of smolts
and returning adults. X-axis depicts different management reaches in the basin. Yaxis
is lambda, the population growth rate.
Improving ocean survival improves to the point where populations in free-flowing
rivers are self-sustaining (Lambda = 1) with stocking held at current levels was
modeled next (Figure 2). This scenario assumes that all stocking occurs in the
specified reach; therefore, each reach has an equal chance of response. Habitat
limitations are not considered. “Removed” data indicate after dam removal and
“Current” data indicate current conditions with the dams in place. The West Enfield
line includes returns to the Penobscot upstream to Weldon and the Mattawamkeag.
The Piscataquis Lower predictions are for the Piscataquis between Howland and
Dover-Foxcroft, while the Upper Piscataquis predictions include the effects of the
additional three dams upstream of Howland after dam removal. The sub-population
of the Lower Piscataquis has the strongest predicted response to dam removal,
while West Enfield and Upper Piscataquis populations will likely have only modest
changes because there remains at least one dam on their migratory route. In spite of
dam removal, all reaches in the Penobscot basin that still have at least one dam
show markedly lower population size than a free-flowing river.
PRFP Page 136