Abstract
BackgroundIn recent years, large-scale acoustic telemetry observation networks have become established globally to gain a better understanding of the ecology, movements and population dynamics of fish stocks. When studying a species that uses different habitats throughout its life history difficulty may arise where acoustically suboptimal habitats are used, such as shallow, vegetated areas. To test the feasibility of active tracking in these acoustically suboptimal habitats, we quantified detection probability and location error as a function of several environmental variables with two transmitter types in a shallow freshwater embayment.ResultsWhen placed in nearshore areas (< 1 m deep), the higher-powered transmitter (158 dB) had significantly greater detection probability than the lower-powered transmitter (152 dB). For both transmitter types, detection probability declined at 200 m; however, at the 100 m distance the higher-powered transmitter had greater than 50% detection probability per ping cycle (50.4%) while the lower-powered transmitter was substantially less (29.4%). Additionally, detection probability increased when the transmitter was deployed within sparse, senescent Phragmites spp. vegetation (14%). Estimated positional accuracy of transmitters deployed at known locations (location error) was variable (error range: 13–259 m), and was generally higher for the more powerful transmitter. Location error was minimized when the lower-powered transmitter was located near softened shoreline areas compared to near man-made armored shorelines (i.e., rip-rap).ConclusionWhile benefits exist for maximizing transmitter power (e.g., increased detection range in open-water environments), use of a lower-powered transmitter may be advantageous for active tracking specific locations of fish inhabiting shallow water environments, such as in estuarine tidal marshes and shallow wetlands. Thus, when planning acoustic telemetry studies, researchers should conduct site-specific preliminary detection probability/location error experiments to better understand the utility of acoustic telemetry to investigate fish movements in acoustically suboptimal conditions.
Highlights
In recent years, large-scale acoustic telemetry observation networks have become established globally to gain a better understanding of the ecology, movements and population dynamics of fish stocks
Our results suggest that acoustic transmitters can be used in acoustically suboptimal, shallow water environments to achieve specific research objectives, but researchers must be aware of how the physical environment and habitat use of study species influence detection probability and accuracy of positional estimates
The use of acoustic telemetry is an applicable method in shallow freshwater embayments despite its known shortcomings
Summary
Large-scale acoustic telemetry observation networks have become established globally to gain a better understanding of the ecology, movements and population dynamics of fish stocks. If study objectives necessitate work in environments with these characteristics, radio telemetry (e.g., [4, 5],) or passive integrated transponders (e.g., [6],) are often utilized. While these other technologies may be better suited in some applications, they have their own limitations. When a species uses a range of habitats including both deep water across large spatial expanses and shallow habitats (e.g., during spawning), acoustic telemetry may be the best option to obtain information in all of these habitats. Examples include alosine and salmonid species that use marine, estuarine, and open lake habitats, but spawn in confined freshwater/ estuarine lotic systems
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