Abstract
Satellite-based oceanographic data products are a valuable source of information on potential resource availability for marine species. Satellite oceanography data may be particularly useful in biotelemetry studies on marine species that feed at low trophic levels, such as zooplanktivorous whales, sharks, and rays. The basking shark, Cetorhinus maximus, is a well-documented zooplanktivore in the western North Atlantic, yet little is known of its movements and spatial ecology in this region. A combination of satellite tag technologies were used to describe basking shark movements with respect to concurrent satellite-observed oceanographic conditions in order to test for selection of these environmental variables. Satellite-linked ‘smart’ position only transmitting tags (SPOTs, N = 10) were used to assess horizontal movements, activity space, and habitat selection, while pop-up satellite archival tags (PSATs, N = 7) were used to describe depth preferences of basking sharks during summer and fall. The duration of SPOT tracks ranged from 5 to 45 days. Basking sharks used relatively small activity spaces in three focal areas off Massachusetts: Vineyard Sound, the Great South Channel, and Cape Cod Bay. These sharks appeared to select areas with shallow bottom depths, high primary production and chlorophyll concentrations, and steep surface gradients, but significant selection for these variables was only detected between mid-August and mid-October when the sharks were primarily located in Cape Cod Bay. Basking sharks in the southern Gulf of Maine during summer and fall focus their activities in discrete areas likely to support high primary and secondary productivity. Habitat selection may also be influenced by mating and social activity at times, but further research is needed to differentiate these behaviors from foraging activity. Satellite-based biotelemetry and oceanography are powerful tools that together can provide valuable new insights into habitat selection patterns of highly mobile marine species.
Highlights
Satellite-based oceanographic data products are a valuable source of information on potential resource availability for marine species
Using data from pop-up satellite archival tag (PSAT), we found that basking sharks primarily preferred the upper water column (
High resolution movements from smart’ position only transmitter (SPOT)-tagged sharks were compared to satellite-based oceanographic measurements concurrent with the periods of tracking, thereby providing new insights into environmental factors that influence habitat selection in this region
Summary
Satellite-based oceanographic data products are a valuable source of information on potential resource availability for marine species. Satellite oceanography data may be useful in biotelemetry studies on marine species that feed at low trophic levels, such as zooplanktivorous whales, sharks, and rays. The basking shark, Cetorhinus maximus, is a well-documented zooplanktivore in the western North Atlantic, yet little is known of its movements and spatial ecology in this region. A combination of satellite tag technologies were used to describe basking shark movements with respect to concurrent satellite-observed oceanographic conditions in order to test for selection of these environmental variables. Analysis of sightings data from the Gulf of Maine and Bay of Fundy indicate that basking sharks may seasonally shift their distributions in relation to environmental variables (depth, temperature, chlorophyll concentrations, circulation patterns) that influence the distribution of their copepod prey [12,16]. Individual movement and habitat selection patterns within these areas have not been examined
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