Assessing the Value of Recreational Divers for Censusing Elasmobranchs

Christine A Ward-Paige,Heike K Lotze

doi:10.1371/journal.pone.0025609

Abstract

BackgroundAround the world, researchers are using the observations and experiences of citizens to describe patterns in animal populations. This data is often collected via ongoing sampling or by synthesizing past experiences. Since elasmobranchs are relatively rare, obtaining data for broad-scale trend analysis requires high sampling effort. Elasmobranchs are also relatively large and conspicuous and therefore it may be possible to enlist recreational divers to collect data on their occurrence and relative abundance from daily dive activities. For this, however, a good understanding of the value of data collected by recreational divers is essential.Methodology/Principal FindingsHere, we explore the value of recreational divers for censusing elasmobranchs using a diverse set of data sources. First, we use a simulation experiment to explore detection rates of the roving diver technique, used by recreational divers, across a range of fish densities and speeds. Next, using a field survey, we show that inexperienced recreational divers detect and count elasmobranchs as well as experienced recreational divers. Finally, we use semi-structured interviews of recreational dive instructors to demonstrate the value of their recollections in terms of effort and their descriptions of spatial and temporal distributions of sharks in Thailand.Conclusions/SignificanceOverall, this study provides initial ground-work for using recreational divers for monitoring elasmobranch populations. If used appropriately, citizen-collected data may provide additional information that can be used to complement more standardized surveys and to describe population trends across a range of spatial and temporal scales. Due to the non-extractive nature of this data, recreational divers may also provide important insight into the success of conservation initiatives, such as shark sanctuaries and no-take zones.

Highlights

Scientists have been gathering data based on the experiences of citizen observers to describe patterns in animal populations for more than a century [1,2,3,4,5,6,7]
General trends in fish populations [10,11,12], including a few that comprise elasmobranchs [13,14,15,16,17], have been generated from data collected by citizen divers
Comparing different underwater visual censuses (UVC) techniques Over 30 simulations, the roving technique detected fish at lower densities than the belt-transect or the stationary point count techniques (Fig. 2); the difference was diminished with increased fish speed

Summary

Introduction

Scientists have been gathering data based on the experiences of citizen observers (e.g. citizen scientists and resource users) to describe patterns in animal populations for more than a century [1,2,3,4,5,6,7]. General trends in fish populations [10,11,12], including a few that comprise elasmobranchs [13,14,15,16,17], have been generated from data collected by citizen divers (i.e. recreational divers) All these projects used trained divers, which has advantages and limits the number of participants and areas and years sampled. Researchers are using the observations and experiences of citizens to describe patterns in animal populations This data is often collected via ongoing sampling or by synthesizing past experiences. Since elasmobranchs are relatively rare, obtaining data for broad-scale trend analysis requires high sampling effort. A good understanding of the value of data collected by recreational divers is essential

Methods

Results

Conclusion