Comparative Performance of Current-generation Geolocating Archival Tags
Abstract:The performances of the current-generation Lotek Wireless LTD2310 and the Wildlife Computers Mk9 geolocating archival tags were compared. The depth, temperature, and light level sensors of 15 LTD 2310 and 15 Mk9 archival tags were evaluated through hydrocasts of these, along with a calibrated Sea-Bird SBE39 temperature and depth probe, to nearly 500 m. Three experiments were conducted; each included five archival tags of each type simultaneously deployed in hydrocasts, along with the SBE39 probe. In all three experiments, the average differences between depth sensors on the Mk9 archival tags and the SBE39 were significantly greater than those between the LTD2310 archival tags and the probe depths for the hydrocast stops at about 500 m, 300 m, and 200 m. The standard errors about the average depth values for those hydrocast stops in Experiments 1 and 2, were greater for the LTD2310 tags, but for Experiment 3 the standard errors were greater for the Mk9 tags. The average differences between the LTD2310 and Mk9 archival tag temperatures measured by their stalk sensors and the SBE39 probe temperatures were similar in all three experiments over a temperature range of from about 9° to 27° C. The standard errors about the average temperature values were similar in all three experiments. The temperatures recorded by the Mk9 archival tag body temperature sensors lagged significantly, while those of the LTD2310 sensors were close to the temperatures recorded by the SBE39 probe during descents and ascents. The standard errors about the average tag body temperature values in all three experiments are greater for the Mk9 tags. Following the stabilization of light sensors at maximum depths (about 500 m) and darkness, during the three hydrocast ascents the 15 LTD2310 and 15 Mk9 archival tag light sensors indicated an average sensitivity to light at 440 m and 380 m, respectively. Two separate experiments conducted with archival tags implanted in the peritoneal cavity of tunas provided estimates of the accuracy and precision of geolocation based on ambient light level data. The computed distances between the average estimated geolocations, from three LTD2310 and three Mk9 archival tags recovered from captive yellowfin tuna Thunnus albacares, to the tank location (7°25'N-80°10'W) were 43.7 nm and 32.1 nm, respectively. The computed distances between the average estimated geolocations, from 13 LTD2310 and 15 Mk9 archival tags from bigeye tuna Thunnus obesus, released and recovered in association with a moored buoy, to the actual buoy location (1°59'S-95°11'W) were 118.5 nm (1.975 dd) and 162.8 nm (2.713 dd), respectively.
Document Type: Research Article
Publication date: 2006-03-01
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