Saildrone’s first mission in the North Sea, in partnership with Havforskningsinstituttet, Norway’s Institute of Marine Research (IMR), surveyed sandeel, North Sea saithe, and herring—three important species with significant commercial and ecological value. Two saildrones deployed from Bergen spent more than 200 days combined studying the temporal-spatial dynamic of fish aggregations and school formations in an exceedingly busy area of the North Sea. The mission was a pilot study to evaluate the performance of the Saildrone platform in a region of dense marine traffic and also included comparison studies with the research vessel Eros.
The saildrones sailed repeated transects in two areas: the standard Aberdeen-Hanstholm transect and English Klondyke. High plankton density was found in the western part of the Aberdeen-Hanstholm transect; salinity appeared to be one possible factor explaining the heterogeneity of plankton density in both vertical and horizontal structure. Sandeel appeared diurnally at various depths from 2 m to near the sea bottom. There was only a weak tendency that the schools were distributed deeper around midday. However, their diverse vertical distribution indicated underlying drivers of their behavior other than light.
"As an integrated sensor platform, the saildrone is very good. It records a large set of quite advanced sensor data with high quality. I have been in other surveys with commercial vessels or research vessels, and it’s hard to have all those sensors operating at a high level of quality at the same time. The Saildrone sensor package is a big advantage, and it allows us to see what kinds of factors can affect the biology and physical conditions in the sea."
Espen Johnsen, IMR chief acoustician and principal investigator.
The echograms captured during the mission were consistent with those observed by other platforms, with one exception: They revealed schools of fish close to the surface, and in one, backscatter above the surface suggested diving seabirds.