Sustainable exploitation: a review of principles and methods

Abstract

Although the main theoretical framework determining how to exploit populations was derived almost 50 years ago, overexploitation is common. I review 10 major concepts underlying the regulation of exploitation: population increase can be exploited; density dependence is essential; quantifying density dependence is exceedingly difficult; sustainable exploitation involves reducing population size; population growth rate is usually mismeasured; sustainability has many conflicting definitions and the choice depends upon the objectives; it is better to monitor the population than the harvest; quotas are unstable; increasing effort is simple, reducing it is painful; exploit conservatively. I then give a brief account of each of the nine main methods that are used to determine sustainable exploitation and the uses, advantages and limitations of each. The nine techniques are: surplus production models, yield per recruit models, Robinson and Redford model, linking yield to recruitment and mortality, adjusting to population changes, comparing demography across sites, reducing to a fixed fraction of unexploited population size, full population models and adaptive management.

Genetic structure of Greater Sage-Grouse (Centrocercus urophasianus) in a declining, peripheral population

“…While there are numerous examples of sustainable harvest within high-quality habitats (Potts 1986, Sutherland 2001, Willebrand and Hornell 2001, Gonzalez Voyer et al 2003, excessive harvest can reduce spring breeding population size of gamebird species (Anderson and Burnham 1976, Small et al 1991, Williams et al 2004). Harvest of greater sage-grouse (Centrocercus urophasianus) has occurred throughout recorded history , Autenreith 1981, but relatively few studies address the impact of harvest on sage-grouse numbers.…”

How Sustainable Is The Use of Natural Resources in Brazil?

“…A basic principle of management is that a exploited population is usually kept below its carrying capacity, because productivity is maximized at intermediate densities (Sutherland 2001). Thus, Table 1.…”

“…Thus "sustainable use" can be translated as use which allows a population to survive, implying that losses (by mortality, due to exploitation or not, and by emigration) are balanced on the long run by gains (by natality and immigration). Therefore, a demographic approach is a precondition for evaluating if the exploitation is sustainable or not (Sutherland 2001). Following directly from Brundtland's definition, we used as the criterion of sustainability that the exploitation regime would allow the resource to keep on existing for future generations, in order to provide for their needs -which in general tend to increase or at least to remain constant.…”

Funciones y valoraciones de la caza y su gestión en España: estudios científicos sobre el colectivo cinegético

“…En general, los gestores reconocen que la regulación de la extracción en función de la disponibilidad es esencial para evitar un mayor declive de las poblaciones de perdiz, y por tanto para mantener o incrementar las bolsas de caza. Para que esto sea eficaz, una premisa esencial es que las estimas de las poblaciones sean fiables (Sutherland, 2001). Sin embargo, esto no se cumple en el caso de las poblaciones de perdiz roja, donde las decisiones sobre cuánto cazar se basan frecuentemente en valoraciones cualitativas de los gestores o los guardas del coto, y casi nunca en una metodología rigurosa de estima de abundancias .…”