Max Kaplan

Sealed tags ready to be deployed.

Two  acoustic recorders deployed on a reef in the US Virgin Islands in 2013.

Two  acoustic recorders deployed on a reef in the US Virgin Islands in 2013.


Soundscape Measurements

The marine environment is a noisy place, filled with biotic (fish, invertebrate) and abiotic (wind, rain, boats) sounds. These sounds often accompany behavioral processes such as feeding, spawning, or territorial defense. Monitoring the ambient sound field may be an important tool to gauge and track biological activity, species presence and diversity, and ecosystem health. While there has been some use of passive acoustic monitoring to achieve these objectives in terrestrial ecosystems, to date there have been few similar investigations in the marine environment.

I deployed broadband digital passive acoustic recorders developed at WHOI to assess species richness and relative animal abundance in the US Virgin Islands National Park in 2013. The goal of that project was to use short- (24 hour) and long-term (4 month) measurements to evaluate the spatial and temporal variability in the local soundscape of coral reef habitats across multiple sites. These acoustic recorders were deployed in a range of healthy and impacted coral reef sites in order to collect baseline recordings from locations with varying biological diversity. Those data were the basis of two recent publications. This approach may provide a novel means to assess both spatiotemporal heterogeneity and monitor marine ecosystem health, as well as track human activity in an area. More broadly, this investigation can help the managers and government agencies to identify changes in animal abundance and distribution, to designate key areas for protection, and to highlight areas that may be vulnerable to a changing environment.

I subsequently carried out out a follow-up project on a much larger scale in Maui, Hawaii, in collaboration with Dr. Marc Lammers of the Oceanwide Science Institute. We had eight reefs instrumented with acoustic recorders and temperature loggers and carried out concurrent visual surveys. The recorders were retrieved in January 2016, yielding a total of 16 months of data collection. These data are currently being worked up for publication.

Reef Acoustic Propagation

Research over the last several years has indicated that larval fish and invertebrates can detect and orient to sound. Accordingly, reef sound has been posited as potential cue that larval animals may use to select a suitable settlement site to live out their juvenile and adult lives. However, the distances over which sound might be detected and used by larval animals is mostly unknown as a result of only limited knowledge of both larval hearing abilities and patterns of reef acoustic propagation. This study seeks to address the latter question. Acoustic recording transects are being carried out on certain reefs in Maui that are also instrumented with passive acoustic recorders. Data from this investigation should help determine how far reef sound propagates, which will in turn help inform estimates of the distances over which larval animals may use this stimulus.

On-animal Fish Sound Recordings

Many of the sounds recorded on coral reefs are produced by fish. However, to date there have been only a limit number of studies that have looked into the species responsible for producing each sound. Thus, while we can identify this range of sounds it is often hard or impossible to attribute them to a given species. To fill this knowledge gap I have been working with David Mann of Humu and Loggerhead Instruments to build, develop, and test an on-animal accelerometer-based fish tag. This small tag (size of a quarter) can record for multiple days and can be attached externally to the fish. Preliminary lab tests indicate that only the tagged animal is recorded on the tag, which underscores the value of this approach. Enhancement of this technology is ongoing, as are lab tests on captive sea robins (Prionotus carolinus), a seasonally abundance fish.