The PN3 group on Top Predators, held a workshop in Reykjavik, Iceland, 11-15 January 2005. Preliminary analyses of seabird and marine mammal sighting data from the 2004 G.O. Sars cruise were presented, discussed and further analysed at the workshop.
From left: Henrik Skov (DHI, Denmark), Erik Olsen (Institute of Marine Research, Norway), Thorvaldur Gunnlaugsson (Marine Research Institute, Iceland), Gordon Waring (NOAA, USA), Gisli Vikingsson (Marine Research Institute, Iceland), Droplaug Ólafsdóttir (Marine Research Institute, Iceland), Leif Nøttestad (PI, Institute of Marine Research, Norway)
By Erik Olsen and Leif Nøttestad, Instiute of Marine Reserarch (Norway)
The workshop was hosted in an excellent manner by the Sea Mammal Research Group at the Marine Research Institute in Iceland. During four intensive days numerous analyses were presented and discussed. So far the main products of the PN3 group will be six separate scientific papers, most of which will be presented in a more final state at the MAR-ECO meeting in Lisbon in June. These papers include:
1. Analysis of abundance and distribution of marine mammals along the ridge to make estimates of density of whales, and construct distribution maps. This is the first time sighting data on whales have been recorded in the region south of the Charlie Gibbs Fracture Zone to the Azores. The only earlier data from this region comes from position recorded by whalers in the 18th and 19th century.
2. Distribution of seabirds along the the ridge based on sighting and contour maps of estimated densities. The paper will focus on reporting for the first time continuous sightings data on seabirds between the region south of the Charlie Gibbs Fracture Zone (CGFZ) and the Azores and on comparisons of results for the northern part of the Ridge and the CGFZ with data from a cruise in 1989 (Skov et al. 1990).
3. A comparison of distribution of marine mammals in 2004, with the distribution in the 1990’s (determined from Icelandic data) and from the 18th and 19th century based on historical whaling records.
4. Relationship between the number of seabirds observed and the abundance of zooplankton (copepods and krill). We found an increase in seabird observations with increasing plankton biomass at the stations along the MAR, indicating that the birds searching for high density prey patches to feed there.
5. Marine mammal “hot-spots” along the MAR. During the cruise a handful of small areas showed an extremely high abundance of whales. We have used the acoustic data to look into the detailed prey distribution at each of these sites to try to understand what made the animals aggregate exactly there.
6. Distribution and abundance of marine top predators in relation to oceanographic features measured at different scales along the Mid-Atlantic Ridge. This is a geostatistical analysis of habitats along the MAR to develop models that can predict the distribution according to oceanographic parameters like bottom slope, temperature, currents, salinity, chlorophyll etc.
Satellite tagging among the plans
PN3 will also attempt to attach satellite transmitters on large baleen whales close to the Azores in April 2005, and plans for this fieldwork were discussed during the workshop. As soon as this is carried out we will post a report here at www.mar-eco.no.
The Mid-Atlantic ridge at Thingvallir, Iceland.
Future plans for adding MAR-ECO activities to the NASS whale sighting surveys in 2007 were also discussed, and PN3 will work towards using this extensive set of cruises to increase the ecological knowledge of top predators along the MAR.