Harvest management - Ecological Applications: Toward a Sustainable World - page 172

7 Harvest management

Harvesting always involves reducing a population below its carrying capacity. By doing this, density-dependent
factors are relaxed and the population responds by raising its birth rate and dropping its death rate - producing
a surplus that can be harvested without further reducing the population. Harvest managers aim to take the
maximum sustainable yield (the highest the population can support indefi nitely) or the optimum economic yield
(producing the highest profi t per organism harvested). But this is easier said than done.

Chapter contents
7.1 I n t r o d uction 173

7.1.1 Av o i d i n g the tragedy of the commons 173

7.1. 2 K i l l i n g just enough - not too few, not too many 174

7. 2 H a r v e s t management in practice - maximum sustainable yield (MSY) approaches 178

7. 2 .1 M a n a g e ment by fi xed quota - of fi sh and moose 178

7. 2 . 2 M a n a g e ment by fi xed effort - of fi sh and antelopes 181

7. 2 . 3 M a n a g e ment by constant escapement - in time 182

7. 2 . 4 M a n a g e ment by constant escapement - in space 183

7. 2 . 5 E v a l u a t i o n o f t h e MSY approach - the role of climate 184

7. 2 . 6 S p e c i e s that are especially vulnerable when rare 185

7. 2 .7 E c o l o g i s t 's r o l e i n the assessment of MSY 186

7. 3 H a r v e s t models that recognize population structure 186

7. 3 .1 ' D y n a m i c p o o l m o dels' in fi sheries management - looking after the big mothers 187

7. 3 . 2 F o r e s t r y - axeman, spare which tree? 190

7. 3 . 3 A forest bird of cultural importance 191

7. 4 E v o l u t i o n of harvested populations - of fi sh and bighorn rams 191

7. 5 A broader view of harvest management - adding economics to ecology 193

7. 6 A d d i n g a sociopolitical dimension to ecology and economics 195

7. 6 .1 F a c t oring in human behavior 195

7. 6 . 2 C o n f r o n t ing political realities 197

Key concepts
In this chapter you will
recognize that sustainable harvesting is a primary aim of resource management, permitting future
generations to enjoy the same opportunities as we do
note that sustainable harvesting is most challenging when the organisms are small and hidden
from view, with birth and death rates that respond sensitively to climatic fl uctuation, and where
multiple exploiters are involved (ocean fi sh are more diffi cult to manage than forest trees)

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