Research Document - 2003/067
Application of the Precautionary Approach and Conservation Reference Point to the Management of Atlantic Seals: A Discussion Paper
By Hammill, M. and Stenson, G.
Resource management usually involves a tradeoff between conservation, economic and political concerns in establishing harvest levels. Often, decisions fail to consider the uncertainty associated with the available information on the resource, with negative consequences.
The Precautionary Approach (PA) brings scientists,resource managers and stakeholders together to identify clear management objectives, to establish specific benchmark or reference levels, to enable the status of the resource to be evaluated and to identify specific management actions that would be triggered when a population approaches or falls below the benchmark(s). Canada has subscribed to the Precautionary Principle outline in the Rio convention. Within this framework, Conservation, Precautionary and Target reference points can be identified and linked to specific actions to aid in managing the resource. The PA also recognizes that the amount of information concerning the status of a resource may vary and that a lack of information is not sufficient to delay taking a management decision.
Harp seals, hooded seals and grey seals are commercially exploited to varying levels throughout Atlantic Canada. The availability of scientific information concerning the status of these resources (abundance, reproductive and mortality rates) also varies between the three species. A conceptual framework for applying the PA to Atlantic seal management is outlined. For a Data Rich species, two precautionary and a conservation reference level are proposed. A precautionary reference level could be established at 70% (N70) of the pristine population size or a proxy of the pristine population (e.g. maximum population size). When populations fall below N 70 , conservation objectives assumes a greater role in the setting of harvest levels, and measures are put in place to allow the population to increase above the precautionary reference level. A second precautionary level is established at 50% of the estimated pristine population size, while a conservation limit resulting in closure of commercial harvesting is established at 30% of the estimated maximum population size.
Species with no recent population data are considered Data Poor and require a more risk adverse approach to their management. This could be accomplished by identifying the maximum allowable removals that will ensure that the acceptable risk of the population falling below this reference point is only 5%. This level has been referred to as the Potential Biological Removal (PBR) and is easily calculated using default values and an estimate of abundance. Since the only data required is an estimate of population size, it or a similar approach is appropriate for data poor species. The PBR approach has the added advantage that the simulation trials used to establish the appropriate population size (NMin) ensured that the formulation was robust when the model assumptions were relaxed and plausible uncertainties were included.
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