Autonomous Pinniped Environmental Samplers: Using Instrumented Animals as Oceanographic Data Collectors

Abstract

Data-recording tags applied to marine animals store data for later retrieval and can return valuable information on animal behavior and ecology, including habitat preference, physiology, and movement patterns, as well as environmental data. If properly instrumented, calibrated, and archived, data from these tags can add to the oceanographic datastream for parts of the ocean where data are sparse or lacking. Such data, from northern elephant seals instrumented with time?temperature?depth recorders (TTDR) and ARGOS platform terminal transmitters, is examined in this study. Northern elephant seals range widely over the northeastern Pacific on long foraging trips. The seals dive continuously on these trips to depths of 400?600 m. Between March 1998 and March 1999, six female and three male elephant seals were tagged in central California and data were collected during subsequent foraging trips. Temperature and depth were measured and stored every 30 s and retrieved after the animals returned to the rookery months later. Portions of the track where both ARGOS and TTDR data were available from these nine animals averaged 4634 km over 67 days with 2.4 ARGOS positions per day. Mean dive duration was 20 min and mean dive depth was 428 m. A comparison of temperature profiles from seal TTDR with Global Temperature?Salinity Profile Program (GTSPP) subsurface data showed very good agreement, as did surface temperatures to other sources of SST. Quality control of the data and entry into the World Ocean Database (WOD) is described. A total of 75 665 autonomous pinniped bathythermograph (APBT) profiles over the 41 702 km of seal trackline were added to the WOD. Biological autonomous sampling systems have immense potential to contribute oceanographic data in a cost-effective manner. The northern elephant seal represents but one species covering portions of the northeast Pacific Ocean. Research programs presently exist on a variety of species, including southern elephant seals and other pinnipeds, tunas and billfish, sharks, seabirds, marine turtles, and whales. With improving technology, such tags will be applied to even more marine animals and the approach described here can be applied to other species to improve ocean data availability.