be more protective, without long-term sacrifice of harvest, than actions that do
not consider the population state.
In most situations, managers do not directly control either the total harvest (H) or
the harvest rate (h). Instead, they implement and enforce some regulations that are
thought to influenceHorh. Understanding the link between the management
actions (regulations and enforcement) and the population dynamics is important,
and assumptions about this link should be examined carefully. In fact, the underlying
endeavor of the manager is to understand how implementation of regulations affects
the achievement of management objectives—all the intermediate effects do not neces-
sarily need to be understood if the objectives are obtained. To this end, an experi-
mental or adaptive harvest policy (see 13.7.2 and 13.7.3) can be useful, particularly
when data are sparse.
13.3.2Harvest management objectives
Clearly thought out and articulated objectives are crucial to proper harvest man-
agement. For a single species, the simplest objective is to maximize sustainable
harvest. But as with any managed system, there are frequently many objectives
for a harvested system. For instance, maximizing harvest opportunity, maintaining
the population size above some target level, having regulations that are easy to
understand and enforce, preventing decline or extinction, and avoiding having
to forbid harvest of the resource at any time are all possible objectives. Any of
these objectives can be included formally in an analysis of harvest. For example,
a constraint could be added to the objective of maximizing harvest to provide a
minimum number of birds for other purposes such as birdwatching (see Johnson
et al. 1997). Finding the right balance between these objectives is a political decision,
but it has a large impact on the harvest strategy that is implemented. In the PBR
framework, two objectives are implied: allowing harvest, but constraining that
harvest to guard against uncertainty and to allow recovery. These constraints are
induced indirectly through the recovery factor (FR).
The harvest of multiple species increases the complexity of the management
problem, especially when the harvest processes or population dynamics for each
species are not independent. In this case options include: managing for one
species, and hoping for the best with regard to the others; managing primarily for
one species while incorporating other species through constraints; or managing
for a total yield across all species (either weighted or unweighted), perhaps con-
strained by minimum population sizes on each. Final management objectives are
often the result of compromise among objectives of various stakeholders. This
compromise might be significant if the objectives are conflicting. For example, as
Newton (1998) discusses, imagine harvesting two species, an r-selected species
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