and a K-selected species with a common regulatory framework. Managing only
for the r-selected species might imperil the other species; while managing only
for the K-selected species would require foregoing the significant harvest poten-
tial in the r-selected species. While there are biological implications of various
objectives in a multi-species context, the articulation of objectives is a political
endeavor.
13.4 Assessing harvest levels
13.4.1Total harvest (H) versus harvest rate (h)
Assessments of harvest and harvest rate are related as
HhN, (13.6)where Nis abundance. Harvest is the total number of individuals killed and
retrieved by hunters in a specified time period. Harvest rate can be defined in dif-
ferent ways but is frequently the probability that an individual alive at the begin-
ning of a hunting period is killed and retrieved by a hunter during this period. As
is clear from the preceding equality, interpretation of an estimate of total harvest
as a measure of magnitude of exploitation is difficult in the absence of an estimate
of animal abundance. Harvest rate is thus more commonly used as a parameter
in population-dynamic and management models. However, in the actual estab-
lishment of harvest regulations, it is frequently easier to specify a harvest quota or
allowable number of individuals to be removed from the population.
In the models and discussion presented above, harvest has been referred to as
the total number of individuals removed by exploitation, and harvest rate as the
probability that an individual in the population prior to the hunting season dies
as a result of hunting. For many forms of exploitation, animals may be killed as
part of the exploitation process, yet not retrieved by hunters (e.g. Anderson and
Burnham 1976; Pollock et al. 1994). For example, birds may be shot by hunters
and their carcasses not located, or birds may be injured and escape the hunter only
to die subsequently as a result of gunshot wounds. In such situations, the term
“harvest” is typically reserved for the number of animals retrieved by hunters,
whereas “kill” is sometimes used to refer to the number of animals that die as
a result of exploitation.
13.4.2Harvest estimation when harvest is legal and observable
Several methods exist for sampling hunters in order to estimate harvest, and selec-
tion of an appropriate method depends heavily on the geographic scale of harvest
and the logistical ease with which hunters can be encountered either during or just
312 |Exploitation