Distribution of vulnerable marine ecosystem indicator taxa in relation to fishing effort on
Cobb Seamount
Janelle M.R. Curtis1 and Cherisse Du Preez2
1
Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, BC, Canada
E-mail: janelle.curtis@dfo-mpo.gc.ca
2
Institute for Ocean Sciences, Fisheries and Oceans Canada, Sidney, BC, Canada.
The distribution of coldwater corals, sponges, and other structure-forming species have been
used in Pacific and Atlantic Oceans to indicate the potential locations of vulnerable marine
ecosystems (VMEs), which are defined as areas susceptibe to serious adverse impacts of bottomcontact fishing gears. Cobb Seamount, an isolated biodiversity hotspot in the Northeast Pacific
Ocean, supports diverse assemblages of coldwater corals and sponges. A recent survey of Cobb
Seamount mapped observed occurrences of VME indicator taxa and documented 95 incidences
of fishing impacts from 19 transects ranging in depth from 34-1154 m, including entanglement
of various fishing gears with corals. To evaluate the potential occurrence of VMEs on Cobb
Seamount, we used the spatially-referenced data from this survey to predict the distribution of
VME indicator taxa relative to the distribution of commercial sablefish fishing effort from 19962010. Specifically, we used a random forest technique to model the spatial distribution of 19
indicator taxa grouped at species, genus or family levels based on sablefish fishing effort and
environmental variables derived from a 20 m x 20 m resolution bathymetry raster. These
variables included depth, slope, aspect, rugosity, bathymetric position index, and seafloor
curvature. The most important predictors of the distribution of VME indicator taxa were depth,
rugosity, and slope. However, inclusion of sablefish fishing effort as an explanatory variable
significantly improved most models. Sablefish fishing effort was positively correlated with the
density and occurrence of VME indicator taxa. Thus, further research is warranted to determine
the potential for serious adverse impacts to VMEs on Cobb Seamount.