It has recently become possible to store all logged data in a flash memory inside the CTD-SRDL tags, so that when the tag is recovered after a deployment, the whole dataset can be retrieved. Elephant seals typically perform more than 60 dives every day. This opens new and exciting potentialities in terms of ocean observation.
In parallel, TDR (time-depth recorder) archival tag are sometimes used in combination with CTD-SRDLs or with FastLoc GPS for the geo-positioning (C. Guinet, SO-MEMO). This technique requires that the loggers are recovered after their deployment on animal because there is no data transmission. This limits the range of their applicability. However, there are many species and deployment sites for which the rates of recovery are sufficiently high. The MK9 or MK10 archival tags, manufactured by Wildlife Computers, are widely used to record continuously pressure, temperature and light along the animal's foraging trip. The resolution and precision of temperature data is rather low, of order 0.5C, however the spatial and temporal resolution is often exceptionnally high.
Here we present some preliminary results from a CTD-SRDL tag deployed in the Kerguelen Islands by Christophe Guinet, and that has been recovered on land after the deployment period. Several similar tags are being recovered right now. These data are yet not available publicly from this website, but they can be obtained on demand. Some of the MK9/MK10 data are distributed on the MEOP portal in the MEOP-TDR database.
Temperature and salinity sections obtained by recovering a CTD-SRDL tag at the Kergulen Islands. Data owner: Christophe Guinet, CNRS, France.