Experimental assessment of lionfish removals to mitigate reef fish community shifts on northern Gulf of Mexico artificial reefs

Ka Dahl,Wf Patterson,Ra Snyder

doi:10.3354/meps11898

Abstract

Substantial declines in reef fishes were observed at northern Gulf of Mexico artificial reef sites between 2009�2010 and 2011�2012, a period that bracketed the appearance of invasive lionfish in this ecosystem. Small demersal reef fishes, the predominant prey of lionfish in other sys- tems, displayed the greatest declines. However, a confounding factor during this time was the Deepwater Horizon Oil Spill (DWH) in summer 2010. In some areas, targeted lionfish removals have been demonstrated to mitigate negative effects on native fishes. Therefore, we conducted a 2 yr experiment to examine the effectiveness and ecological benefits of targeted lionfish removals at artificial reefs (n = 27) off northwest Florida, USA, where lionfish densities reached the highest recorded in the western Atlantic by 2013. All lionfish were removed via spearfishing from 17 reefs in December 2013, 9 of which were periodically re-cleared of lionfish through May 2015. Remain- ing sites served as uncleared controls. Both juvenile and adult lionfish quickly recruited to cleared reefs, with lionfish reaching pre-clearance densities in <1 yr on reefs cleared only once. Removal treatment significantly affected reef fish community structure at experimental reefs, but removal effort was insufficient to achieve substantial gains for most taxa, and declines in several taxa were observed throughout, regardless of treatment. It is unclear whether chronic effects of the DWH or regionally high lionfish densities were more important factors in explaining trends observed in reef fish communities, but small-scale targeted lionfish removal efforts had few positive impacts overall on native reef fish communities in this study.

Highlights

Indo-Pacific lionfishes, Pterois volitans/miles complex, have exhibited an extensive and rapid invasion in the western Atlantic Ocean, earning the species the distinction of being the most successful marine fish invader to date (Whitfield et al 2002, Morris & Akins 2009, Albins 2013)
The objectives of the study were to evaluate the effectiveness of targeted lionfish removals as a means to control lionfish densities, as well as to evaluate the effectiveness of lionfish removal for native reef fish community recovery
Study sites consisted of 27 artificial reefs within the Escambia East-Large Area Artificial Reef Site (EELAARS; 260 km2), which is located approximately 32 km south of Pensacola, FL, USA (Fig. 1)

Summary

Introduction

Indo-Pacific lionfishes, Pterois volitans/miles complex (hereafter ‘lionfish’), have exhibited an extensive and rapid invasion in the western Atlantic Ocean, earning the species the distinction of being the most successful marine fish invader to date (Whitfield et al 2002, Morris & Akins 2009, Albins 2013). At the time of this writing, lionfish have established an invaded range of over 7 million km, in diverse habitat types beyond their native coral reefs across tropical and sub-tropical western Atlantic Ocean waters, including the Caribbean Sea and Gulf of Mexico (GOM) (Schofield 2009, Côté et al 2013, Schofield et al 2014). By late 2010, lionfish had been observed in eastern, northern and western regions of the GOM (Schofield 2010, Fogg et al 2013, Dahl & Patterson 2014, Nuttall et al 2014). In the short span of time since initial observations, lionfish populations in the northern GOM (nGOM) have increased exponentially and have reached high densities (> 20 fish 100 m−2) on artificial reefs, yet their densities on natural reefs remain 2 orders of magnitude lower (Dahl & Patterson 2014)

Objectives

Methods

Results