Applying a statistical analysis technique called ‘distance sampling’, we can potentially generate population estimates for macro-marine or terrestrial species on any scale and in any location throughout the world. The desired precision and unbiased nature of such estimates are related to sample size, survey coverage, methodology, including accurate measurements of sighting distance and angle. Irrespective of whether surveys are dedicated to monitoring cetaceans, pinnipeds, birds or terrestrial species, our observers record all incidental species sightings to facilitate an ecosystem approach and understanding of inter-population dynamics.
An essential part of long-term management of cetacean (whale, dolphin and porpoise) populations and their habitat is a robust and cost-effective means of monitoring relative abundance and density (e.g. animals per km2) before, during and after any marine activities. Abundance and density estimates can provide useful information at a rudimentary scale; however, more detailed information on the distribution of animals can be obtained by applying density surfacing modelling techniques. These techniques use satellite data and mathematical models to describe how density is related to a range of habitat variables (e.g. depth and distance from coast) using data collected along survey transects or within the confines of shore studies when point sampling is preferentially employed. Such a model can then be extrapolated to the whole survey area to provide a picture of how density varies at a fine spatial scale.
Visual data collection and analytical methods developed by Centre for Research into Ecological and Environmental Modelling (CREEM), based at the University of St. Andrews, Scotland, and the adoption of the associated ‘Distance’ software programme, in conjunction with the recommended techniques of other industry experts, are typically employed to maintain consistency and comparability. Depending on the complexity of a survey, observers can be supervised in the field by technical and statistical experts to ensure that survey methods are implemented correctly. Post survey, the focus of a project changes to data processing and analysis, the complexity of which is generally the determining factor in the time requirement for these studies. All the visual shipboard, installation, shore or terrestrial-based data need to be validated and converted into a standard format prior to any analyses.