REPRODUCTIVE STRATEGY OF
MERGINI TRIBE (SEA DUCKS) IS OPPOSITE SPECTRUM OF ANATINI TRIBE (DABBLERS)
- Sea ducks are less able to compensate
for an additional form of mortality such as hunting because these
species have a "K-selected" reproductive strategy:
- long lived, with low natural
mortality
- annual adult survival is high ( in a
healthy population),
- annual recruitment to breeding age
is low,
- annual breeding rates and success
are variable
- clutch sizes tend to be small
- low annual production or recruitment
rates to breeding age
- variable annual rates of non
breeding by adults
- deferred sexual maturity. (2-3
years)
- r- dabbler and K-diver species are at
the opposite ends of the threshold spectrum, R- DABBLERS (MALLARDS) ARE
OPPOSITE THE ABOVE LIST.
- The r-K concept indicates that
mortality rates should be
- highest in the r-dabblers
- intermediate in the
K-dabblers
- lowest in the K-divers
- Biologically, The Mergini tribe
should have the most restrictive bag limit yet it continues to be
grossly excessive
- The K-selected reproductive strategy
minimizes the importance of annual investment in reproduction and
maximizes the importance of annual survival.
- Management for recovery of declining sea
duck populations is difficult because K- selected life history traits
may limit rate of recovery
- Small population growth may result even
in the absence of threats.
- sea ducks are much more sensitive to
changes in adult survival than to annual variability in recruitment
- Population stability of sea ducks is
dependent on high adult survival and a few successful years of
production.
- Species which maintain population
stability through high adult survival are sensitive to increased
mortality. Long lived Sea ducks are much more sensitive to changes in
adult survival than to annual variability in recruitment.
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