Bringing data to the surface: recovering data loggers for large sample sizes from marine vertebrates

Abstract

Background: Despite the utility of data loggers for studying the fine-scale behavior and energetics of marine organisms, most studies using these tools have had relatively low sample sizes due to various factors including the logistical difficulty of physically recovering the loggers. Here, we report a simple methodology for recovering large numbers of data loggers over a broad search area, which has proven successful even for large, itinerant marine species. Techniques described include the use of VHF telemetry, a high-speed search vessel, GPS, and custom maps of the search area in order to record logger float package locations and optimize recovery strategy. Results:We have deployed data logger packages on 193 sharks of 8 different species in the Gulf of Mexico, with a recovery rate of 97.4 %, retrieving 188 of the loggers with a total of over 4260 h of fine-scale acceleration data. Lost float packages are likely due to scavenging of sharks that succumbed to post-release mortality and ingestion of the packages by larger sharks. Mean (±SD) deployment time for the packages was 22.9 ± 22.5 h (range 0.7-205 h), and mean overall displacement distance was 31.3 ± 28.2 km (range 0.62-231 km). Animals showed a tendency to swim offshore after tagging, with 75 % of packages recovered at a bearing between 180° and 290° relative to their tagging location. Sharks swam to deeper water after tagging, with maximum depths reaching an average of 11 ± 8 m greater at the end of the track versus the start. Due to the high recovery rate and the reusability of these data loggers, we have successfully documented the post-release outcome of 188 sharks at a cost of approximately $535 per shark, compared to a cost of $4200 per shark to have done the same work with satellite tags. Conclusions:Given the high recovery rate and the cost-effectiveness of these tags, our results illustrate clear advantages in cost and data quality of this method compared to studies using conventional satellite tags.

A novel method for determining post-release mortality, behavior, and recovery period using acceleration data loggers

“…Indeed, for species capable of resting on the seafloor, a stationary depth trace may not be an accurate proxy for mortality, and the movement data provided by ADLs could allow for investigations on a broader range of taxa than are appropriate for other tagging methods. Additionally, the ability to recover tags and re-use them can allow for increased sample sizes, further improving post-release mortality estimates (Lear and Whitney 2016). Based on our findings, we propose that ADLs can be used to fill knowledge gaps regarding post-release mortality and sub-lethal behavioral effects in a wide variety of coastal taxa.…”

“…The need for recovery also increases time and labor costs, and limits deployment duration in studies of pelagic or highly mobile species. Although packages can be detected by a VHF receiver from up to 25 km away once they float to the surface, detection range is variable depending on air and sea conditions (Lear and Whitney 2016).We achieved 100% package recovery over periods of up to 72 h at large. Even when accounting for recovery costs and the one-time cost of the VHF receiver equipment (∼$1000), the ADL method is still 1/4th to 1/8th the cost (per shark) of using satellite tags (Lear and Whitney 2016).…”

“…In an assessment of release timing accuracy, Whitmore et al (2016) found an overall mean variance of 1% in actual GTR release time compared to expected time. Floating tag packages were detected using a hand-held VHF receiver (R45-20C, Advanced Telemetry Systems, USA), and retrieved by vessel (see Lear and Whitney 2016).…”

Correlations of metabolic rate and body acceleration in three species of coastal sharks under contrasting temperature regimes

“…Despite these challenges, accelerometry is likely to provide accurate estimates of FMR, particularly during activity, and offers additional benefits over other methods. These benefits include ready commercial availability and inexpensive costs compared with other types of sensors (Whitney et al, 2012;Lear and Whitney, 2016), as well as relatively easy and non-invasive attachment mechanisms. However, external tag attachments can sometimes affect energy expenditure and swimming behaviour through increased drag and negative buoyancy, particularly in small animals (e.g.…”

Was my science project eaten? A novel approach to validate consumption of marine biologging instruments

“…Instances of BI consumption are commonly determined by a qualitative examination of instrumentrecorded data and, depending on the BI, evidenced by changes in behavioral patterns or tailbeat frequencies, elevated temperatures, temperature delays with respect to the depth profile, and negligible light levels [1,22,[24][25][26][27][28][29][30][31][32]. Tag consumption may be obvious in some cases, such as when zero-valued light levels in epipelagic waters concurrent with elevated temperatures clearly indicate BI consumption by an endotherm [22].…”