The most extreme version of this type of manipulation is to switch back and forth between u(t) = 0 (all extracted resources allocated to elevating the average quality of individuals in the population) and u(t) = 1 (all extracted resources allocated to increasing population abundance).
Research is sorely needed on whether the demographic advantages of increasing population abundance via captive breeding can outweigh the genetic disadvantages of losing fitness in captivity.
Theoretical studies and laboratory experiments have indicated that negative density-dependence in population growth may reduce the risk of extinction and increase population abundance of rare species during long periods of adverse environmental conditions, which are more likely to occur under high levels of environmental variance [14], [29], [30].
Previous research indicated that planting switchgrass increased rodent population abundance but reduced recruitment and community diversity.
Regardless of individual distribution, the estimation precision becomes higher with increasing total population abundance and the sampled fraction.
Insects, however, may again be an exception, because their natural fluctuations in abundance could buffer them against extinction, even when fragmentation increases population variability.
Little research has also addressed under what conditions an increase in population abundance due to captive-rearing might offset fitness reductions induced in captivity.
Thus, an unresolved enigma in evaluating the likelihood that captive breeding programs can translate into self-sustaining salmonid populations, is whether, and how, increases to population abundance (N) provided by captive-rearing could offset reduced fitness in the wild of captive-reared fish and their progeny.
As sample density declined, the probability of a survey availability event, defined as a survey yielding indices >125% or <75% of the true population abundance, increased and that increase was disproportionately biased towards underestimates.
