Combining Power Analysis and Population Viability Analysis to Compare Traditional and Precautionary Approaches to Conservation of Coastal Cetaceans

Abstract

Traditionally, marine resources have been managed such that controls on new developments are implemented only when harmful effects on other environmental or economic interests can be demonstrated. This approach poses particular problems for the conservation of coastal cetaceans because potential threats to their populations are diverse and likely to interact, individual threats may result from multiple sources, and the problems inherent in studying cetaceans result in considerable scientific uncertainty and low statistical power to detect any effects. Consequently, many countries are adopting integrated coastal management programs and precautionary management principles. In practice, however, issues continue to be dealt with within traditional frameworks that require demonstration of harm. Because cetaceans are long‐lived, they demand long‐term studies, and populations could decline to dangerously low levels before management action is taken. We illustrate these problems using a case study from the Moray Firth, Scotland. This inshore area will soon be designated and managed as a “special area of conservation” to protect bottlenose dolphins ( Tursiops truncatus) under the European Community's Habitats Directive. The population is small and isolated, and it faces a wide range of potential threats, but there remains considerable uncertainty over the magnitude of each threat. We combined power analysis and population viability analysis to explore the relative consequences of adopting either traditional or precautionary approaches to management. In this case, our results reaffirm the need for precautionary management. More generally, we illustrate how this approach can be used to provide a more scientific basis for determining the level of precaution required to address particular management issues in this and other marine systems.

Individual Recognition

“…Photo-identification of natural markings is increasingly being used to collect data on individual animals for application to demographic studies (Thompson et al, 2000;Lusseau et al, 2006;Bradshaw et al, 2007). Although information obtained from photo-identification is highly valuable (Hammond, 1990;Blackmer et al, 2000), processing data in large catalogues can be labour-intensive and subject to human error (Kelly, 2001).…”

“…Such insights could provide a quantitative foundation for the re-evaluation of the regional, national and global conservation status of this species, thus strengthening international maritime protection policies amongst Mediterranean countries (Thompson et al, 2000;Sibly et al, 2005;Fagan and Holmes, 2006). For example, the creation of photo-libraries at local, national and regional scales, within which individual life-histories of individuals could be developed as well as knowledge about small and large scale migrations of male and female turtles, e.g.…”

“…The ability to identify individuals within a population is often a starting point for ecological and conservation studies (Thompson et al, 2000;Sibly et al, 2005;Lusseau et al, 2006;Bradshaw et al, 2007;McMahon et al, 2007). Realistic estimates of population size and life history parameters are central to effective wildlife management, but are often difficult to measure in long-lived and elusive migratory marine vertebrates (Caughley, 1994).…”

“…The ability to recognize individuals from naturally occurring features has many advantages over conventional marking techniques including: animals are not physically captured, identifiable characteristics are stable over time, and the behaviour of the animal is less likely to be affected by the identification system (Hammond, 1990;Blackmer et al, 2000). Photographic identification, in which researchers photographically capture these natural markings to identify and re-identify individuals, has proven to be a useful tool in long-term monitoring of wild animal populations (Thompson et al, 2000;Forcada and Aguilar, 2003;Bradshaw et al, 2007). For example, whisker patterns are used in lions, facial scale patterns in sea turtles, pelage spot patterns in whale-sharks, fin shape and scarring in dolphins (Richardson et al, 2000;Thompson et al, 2000;Arzoumanian et al, 2005;Ogutu et al, 2006).…”

“…Photographic identification, in which researchers photographically capture these natural markings to identify and re-identify individuals, has proven to be a useful tool in long-term monitoring of wild animal populations (Thompson et al, 2000;Forcada and Aguilar, 2003;Bradshaw et al, 2007). For example, whisker patterns are used in lions, facial scale patterns in sea turtles, pelage spot patterns in whale-sharks, fin shape and scarring in dolphins (Richardson et al, 2000;Thompson et al, 2000;Arzoumanian et al, 2005;Ogutu et al, 2006).…”