Mobilizing volunteers to sustain local suppression of a global marine invasion

Green, SJ, E Underwood, and JL Akins. 2017. Mobilizing volunteers to sustain local suppression of a global marine invasion.

Conservation Letters. DOI: 10.1111/conl.12426

Lionfish derbies and tournaments were first implemented in 2009 with the intent of increasing public awareness about the lionfish invasion in the western Atlantic, gathering specimens for research, and training volunteers to safely and effectively collect the venomous species. Since then, REEF has coordinated a series of derbies each year and assisted other organizations and groups in organizing and running their own derbies, resulting in the removal of tens of thousands of invasive lionfish.

The increasing number of derbies held across the region presents an excellent opportunity to investigate the extent to which volunteer removal activities during such derbies can be an effective means of population suppression. Using REEF lionfish derbies as a test case, REEF staff, affiliated scientists, and volunteers worked together to address six key questions: 1) What is the total area over which removal can be affected during a derby event? 2) Is capture during derbies size-selective? 3) To what extent are local invader populations suppressed by derby activities? 4) At what rate do lionfish re-colonize following derby events? 5) Is removal sufficient to reduce and sustain densities below those predicted to cause predation-mediated declines in native species? and 6) Is the magnitude of invader removal related to catch per unit effort (CPUE)? To answer these questions, the authors collected data on landings and participant effort over three years of lionfish derbies in both Key Largo, Florida and Green Turtle Cay, Bahamas.

The study documented that from 2012-2014, single day derbies reduced lionfish densities by 52% across an area of 192 km2 on average each year. Differences in recolonization and productivity between regions meant that annual events were sufficient to suppress the invasion below levels predicted to cause declines in native species in one region, but not the other. Population reduction was not related to CPUE, confirming the importance of in situ monitoring to gauge control effectiveness. Future work to assess rates of recolonization in relation to derby frequency will help guide management and control decisions.

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