Spatial and temporal variation in positioning probability of acoustic telemetry arrays: fine-scale variability and complex interactions

Abstract

Background: As popularity of positional acoustic telemetry systems increases, so does the need to better understand how they perform in real-world applications, where variation in performance can bias study conclusions. Studies assessing variability in positional telemetry system performance have focused primarily on position accuracy, or comparing performance inside and outside the array. Here, we explored spatial and temporal variation in positioning probability within a 140-receiver Vemco Positioning System (VPS) array used to monitor lake trout, Salvelinus namaycush, spawning behavior over 23 km 2 in Lake Huron, North America.Methods: Variability in VPS positioning probability was assessed between August and November from 2012 to 2014 using 43 stationary transmitters distributed throughout the array. Various analyses were used to relate positioning probability to number of fish transmitters in the array, wave height, and thermal stratification. We also assessed the prevalence of 'close proximity detection interference' (CPDI) in our array by analyzing detection probability of 35 transmitters on collocated receivers.Results: Positioning probability of the VPS array varied greatly over time and space. Number of fish transmitters present in the array was a significant driver of reduced positioning probability, especially during lake trout spawning period when the fish were aggregated. Relationships between positioning probability and environmental variables were complex and varied over small spatial and temporal scales. One possible confounding variable was the large range of water depth over which receivers were deployed. Another confounding factor was the high prevalence of CPDI, which decreased exponentially with water depth and was less evident when wave heights were higher than normal.Conclusions: Some variables that negatively influenced positioning can be minimized through careful planning (e.g., number of tagged fish released, transmitter power level). However, results suggested that the acoustic environment was highly variable over small spatial and temporal scales in response to complex interactions between many variables. Therefore, models that predict positioning or detection efficiencies as a function of environmental variables may not be attainable in most systems. The best defense against biased study conclusions is incorporation of in situ measures of system performance that allow for retrospective analysis of array performance after a study is completed.

Use of an acoustic telemetry array for fine scale fish behaviour assessment of captive Paiche, Arapaima gigas, breeders

“…As described in another study (James, Fischer, Laube, & Spindler, ) we were expecting an homogeneous distribution on all directions as the test transmitter was placed approximately at the centre of the array. Nevertheless as previously mentioned (Bergé et al., ; Binder et al., ) this finding showing an oriented distribution could be attributed to sound wave reflection on the pond shoreline, which slope is not perfectly similar on all its length. But if we consider the observed accuracy (<1 m) we still have highly reliable position accuracy as fish average size was 1.67 ± 0.15 m. This accuracy around the meter range is similar to that obtained with Chinook salmon in similar 4,000 m 2 enclosure using a 9‐hydrophone array (Semmens, ) and an 8‐hydrophone array in a 10,000 m 2 natural lake (Baktoft et al., ).…”

“…Theoretical detection distance (few‐hundred meters) was virtually higher than the largest possible distance (diagonal) of the pond used in this study, which corresponded to 102 m. Nevertheless the effective average detection rate reached only 66.55%. The reason, as mentioned in other studies (Binder et al., ; Hartill, Morrison, Smith, Boubée, & Parsons, ), is probably due to fish orientation or position close to the shore inducing signal absorption, background noise or signal collisions when numerous transmitters are present that did not allow a valid calculation position by the LOTEK's U‐Map software. A small percentage of detections corresponded to out of pond bearings (6.4%) and some in‐pond wrong bearings too (1.1%) identified by the speed filter.…”

“…Technical and miniaturization improvements have permitted the development of ultrasonic telemetry equipment in aquatic environments (Crossin et al., ; Hussey et al., ) or GPS system in aerial or terrestrial studies, which allow a much higher positioning frequency (Abecasis, Bentes, Lino, Santos, & Erzini, ; Bellquist, Lowe, & Caselle, ; Binder, Holbrook, Hayden, & Krueger, ; Binder et al., ; Espinoza, Farrugia, Webber, Smith, & Lowe, ; Espinoza, Heupel, Tobin, & Simpfendorfer, ; Farmer, Ault, Smith, & Franklin, ; Lowe, Topping, Cartamil, & Papastamatiou, ; Martins et al., ; Mason & Lowe, ; Pursche, Suthers, & Taylor, ; Semmens, ; Simpfendorfer, Heupel, & Hueter, ; Topping, Lowe, & Caselle, ; Villegas‐Ríos et al., ).…”

Evaluation of acoustic telemetry grids for determining aquatic animal movement and survival

“…For spatial heterogeneity in detection range, more closely spaced receivers in one habitat may be required to equal the detection efficiency in adjacent habitats. In habitats with high bathymetric relief where detection efficiency varies substantially, adaptive receiver placement is a paramount consideration (Binder, Holbrook, Hayden, & Krueger, ). For temporal heterogeneity, if the research question requires confirmation of the presence of an animal on time‐scales much longer than sporadic interference from dynamic variables, then it may not be necessary to quantify such effects.…”

Field testing a novel high residence positioning system for monitoring the fine‐scale movements of aquatic organisms

“…Recent advances in biotelemetry have revolutionized the scales at which aquatic organisms can be monitored in the wild, with data on the locations of individuals being collected more frequently and over larger geographic areas than previously possible (Baktoft et al., ; Binder, Holbrook, Hayden, & Krueger, ; Biesinger et al., ; Cooke et al., ). One area that has seen dramatic advancement has been the use of acoustic telemetry to gain accurate estimates (within a few meters) of the two‐dimensional (2D) positions of aquatic organisms tagged with acoustic tags (Binder et al., ). Acoustic telemetry positioning systems typically consist of several stationary receivers arranged in a regularly spaced array of near equilateral triangles or squares with overlapping detection ranges.…”