Integration of a miniaturized conductivity sensor into an animal-borne instrument.

Predicting how marine animal populations respond to habitat changes is essential for developing conservation management strategies and this in turn demands environmental data at a wide range of scales, from large slow synoptic changes to much finer scales, scales appropriate to the animals’ ability to sample and be directly affected by them. In particular, relating marine mammal movements and behavior to fine-scale ocean structure requires oceanographic information on similar spatial and temporal scales.

The appropriate environmental information is usually not readily available especially in high latitude oceans. One way to solve this mismatch is to deploy oceanographic sensors on the animals themselves to obtain in-situ information without any spatial or temporal lag. Over the past 20 years, the use of miniaturized animal-attached tags for logging or relaying data about an animal’s movements, behavior, physiology and environment has enabled us to improve our understanding of this interaction, and in combination with surveys and other approaches, the ecology of free-ranging marine mammals.

In this study, we modified an existing miniature conductivity-temperature sensor of about 10x10mm and incorporate it into the proven design of a Satellite Relay Data Logger (SRDL). Reducing the size of the instrument by using a smaller sensor will allow the instrument to be deployed on a much wider range of species, including many other smaller ones. But it will also be advantageous in other important ways. It will make available space on the instruments for more complex sensor packages and geo-location approaches. It will also allow compatibility with other data relay modalities, mounting and attachment configurations or additional energy supplies while maintaining the current size and weight.

The conductivity measurements are based on electrodes limiting the measured external field and are therefore not influenced by the attachment method. This methodology provides for ecosystem studies of a range of marine animals (e.g. large cetaceans, fish, birds) that are not currently feasible. Here, we show the performance of the instrument package collecting data to demonstrate it can obtain data of sufficient quality to investigate the links between animal behavior and local physical conditions.