[MARMAM] NEW PAPER: The Influence of Topographic and Dynamic Cyclic Variables – PLOS ONE
Marijke de Boer
marijke.deboer at yahoo.co.uk
Fri Jan 24 23:27:17 PST 2014
I am pleased to announce the following paper recently published in Plos One.
The Influence of Topographic and Dynamic Cyclic Variables on the Distribution of Small Cetaceans in a Shallow Coastal System
De Boer MN, Simmonds MP, Reijnders PJH, Aarts G
PLoS ONE 9(1): e86331. doi:10.1371/journal.pone.0086331
The influence of topographic and temporal variables on cetacean distribution at a fine-scale is still poorly understood. To study the spatial and temporal distribution of harbour porpoise Phocoena phocoena and the poorly known Risso’s dolphin Grampus griseus we carried out land-based observations from Bardsey Island (Wales, UK) in summer (2001–2007). Using Kernel analysis and Generalized Additive Models it was shown that porpoises and Risso’s appeared to be linked to topographic and dynamic cyclic variables with both species using different core areas (dolphins to the West and porpoises to the East off Bardsey). Depth, slope and aspect and a low variation in current speed (for Risso’s) were important in explaining the patchy distributions for both species. The prime temporal conditions in these shallow coastal systems were related to the tidal cycle (Low Water Slack and the flood phase), lunar cycle (a few days following the neap tidal phase),
diel cycle (afternoons) and seasonal cycle (peaking in August) but differed between species on a temporary but predictable basis. The measure of tidal stratification was shown to be important. Coastal waters generally show a stronger stratification particularly during neap tides upon which the phytoplankton biomass at the surface rises reaching its maximum about 2–3 days after neap tide. It appeared that porpoises occurred in those areas where stratification is maximised and Risso’s preferred more mixed waters. This fine-scale study provided a temporal insight into spatial distribution of two species that single studies conducted over broader scales (tens or hundreds of kilometers) do not achieve. Understanding which topographic and cyclic variables drive the patchy distribution of porpoises and Risso’s in a Headland/Island system may form the initial basis for identifying potentially critical habitats for these species.
The paper can be downloaded from PLOS ONE:
Marijke de Boer, Ph.D
Marijke.deboer at wur.nl
Wageningen IMARES, Institute for Marine Resources and Ecosystem Studies,
Postbus 167, 1790 AD Den Burg, The Netherlands
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