Dear all,
The following research papers are now available at the website of
Organisation Cetacea (ORCA). They can be viewed by clicking on the link
below and then going to the “Downloads” page on the menu bar:
http://www.orcaweb.org.uk/index.html
Masters Thesis:
Using Oceanographic Features to Predict Areas of High Cetacean Diversity
Dylan Walker
Abstract
Current conservation legislation is focused on prioritising areas of high
species diversity.Despite this, most oceanic habitats, particularly
offshore, remain poorly studied and have received little protection. This
study used oceanographic and physiographic features to predict areas of high
cetacean diversity. Strong links have been identified between the
distribution of cetaceans, their prey, and a suite of physiographic and
oceanographic variables (e.g. Murase et al. 2002, Tynan et al. 2005).
Cetacean diversity was therefore predicted using a cumulative environmental
scoring system (CES) for the features depth (m), slope (°), chlorophyll-a
(mg/m3), and frontal significance (arbitrary value) present
within a series of pre-set study squares. The predictive power of the CES
was tested using Simpson’s Diversity Index (SDI) scores derived from an
extensive combined cetacean database from the eastern North Atlantic. Data
for 18 species (approximately a quarter of the world’s cetacean diversity)
was provided by Organisation Cetacea (ORCA) and Brittany Ferries Surveys
(BFS). Results showed that a significant positive correlation only existed
between depth and SDI scores (rs38 = 0.336, p <0.05), and between slope and
SDI scores (rs38 = 0.370, p<0.05). Further analysis involving SDI scores for
species groups ‘baleen whales’, ‘dolphins’, and ‘beaked whales and
sperm whale’ revealed that only the ‘dolphins’ group showed a
significant positive correlation with depth (Rs38 = 0.422, p = 0.009) and
slope (Rs38 = 0.538, p = 0.001). This study is the first of its kind to use
remotely gathered environmental variables to predict cetacean diversity, and
in so
doing, has highlighted a significant relationship between shelf-break
habitats with high slope and depth characteristics and high dolphin
diversity. Although a number of limitations exist, this research illustrates
the potential value of CES as a tool in conservation management, thereby
identifying a need for the further development of this
concept.
Posters submitted to the European Research on Cetaceans 19. Proc. 19th Ann.
Conf. ECS. La Rochelle, France. April 2005. European Cetacean Society:
The Distribution of Fin Whales in the Bay of Biscay in relation to
Bathymetry and Sea Surface Temperature.
Farah Chaudry, Nicola Clark, Neal Reay, Ronan Scullion, & Kelly Macleod
Abstract
Despite being one of the most abundant species in the North Atlantic, very
little is known about the distribution of fin whales (Balaenoptera physalus)
in relation to oceanographic parameters, including bathymetry and sea
surface temperature (SST). Fin whale distribution peaked in August (58.5% of
sightings). Mean SST at sighting locations (July – October) was 20.24°C
(n = 470, SD = 1.01°C), with a mean depth of sightings at 3350.0m (n = 470,
SD = 1049.2m). There was a significant positive correlation between the
number of sightings with increasing depth (250m intervals) (Pearson
correlation = 0.520, p = 0.027) and between number of sightings and
increasing temperature (0.5 °C intervals) (Pearson correlation = 0.744, p =
0.006). Fin whales in the Bay of Biscay show a preference for deep waters
off the continental shelf region. Substantial changes in depth over small
areas may encourage upwelling of cold, nutrient rich waters to the surface,
enhancing productivity. While there appears to be a significant correlation
between fin whale sightings and SST, these increased temperatures may induce
the high productivity of prey, rather than having a direct impact on whale
abundance or distribution. Although the euphausiid bloom occurs in April,
fin whales do not aggregate until July, when euphausiids are large enough to
become attractive prey. Future studies should focus on primary productivity
in the region, and the effect of food on the migration of fin whales to the
Bay in the summer months. Further studies should be carried out with
expanded survey effort into the south-western shelf region of the Bay of
Biscay.
Mapping Cetacean Biodiversity in the Bay of Biscay
Dylan Walker, Marde McHenry, Ronan Hickey, Steffania Clemente, Nel Beaumont,
& Kelly Macleod.
Abstract
One aim of current conservation research is to prioritise areas with high
species diversity for protection (Purvis and Hector 2000). Diversity indices
have rarely been applied to cetaceans due to a lack of survey effort in
offshore areas where the majority of species occur. These habitats are,
however, known to be threatened by the effects of anthropogenic impacts such
as overfishing, fisheries bycatch, and pollution. We utilized the
Organisation Cetacea (ORCA) openaccess database incorporating 4500
cetacean sightings over a wide geographical area including shelf, slope and
oceanic habitats in order to map and compare cetacean biodiversity by
habitat within the Bay of Biscay and English Channel. The study area was
divided into quarter ICES squares and divided into three habitats based on
depth. The number of species occurring in each box was ascertained and a
Biodiversity Index (BI) score was developed that attributed the highest
scores to the species occurring in the least number of squares. The lowest
BI was found in the shelf habitat (5.20). The values for oceanic and slope
habitats were 10.53 and 13.31 respectively. Slope habitat was found to have
had a significantly greater BS than shelf habitat (p 0.0001). No significant
difference was found between the oceanic habitat and either of the other
habitats. The results indicate that oceanic, and particularly slope areas,
support a higher diversity of cetaceans than shelf waters. All 20 existing
and 30 proposed Marine Protected Areas in the Northeast Atlantic are in
shelf waters. However, our results indicate that this habitat is likely to
have relatively low cetacean diversity. We therefore recommend that greater
emphasis be placed on slope and oceanic regions for marine conservation.
For further information please contact Dylan Walker by email at:
[EMAIL PROTECTED]
or visit the ORCA website at:
www.orcaweb.org.uk
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