Assessing the effect of recreational scallop harvest on the distribution and behaviour of foraging marine turtles
NAT A L I E WIL DERMANN,CHRIS T O PHE R S ASSO CHRISTIAN GREDZENS and MARIANA M. P. B. FUENTE S
Abstract The impact of fisheries on marine megafauna is widely known but most studies have focused on commercial fisheries, overlooking the effect of local recreational fisher- ies. This is particularly important for marine turtles in near- shore habitats that overlap with recreational fisheries. We assessed the effect of recreational scallop fisheries on the dis- tribution and behaviour of foraging marine turtles in the coastal waters of the upper Eastern Gulf of Mexico. Before and during the scallop season we quantified the density and overlap of marine turtles and vessels sighted, and satellite tracked four turtles to assess their distribution and behav- iour. The relative distribution of marine turtles sighted dur- ing the scallop season overlapped with 48%of the area most frequently used by harvesters, and marine turtle activity hotspots shifted between seasons. In addition, during the scallop season the home range size of individual turtles appeared to decrease, and turtles displayed frequent changes in travel speed and directionality.We hypothesize that such changes are probably related to the distribution and move- ment of vessels and the abundant presence of people in the water. Our study highlights the importance of considering recreational fisheries and their local effect on marine mega- fauna for informing future adaptive management practices. However, further studies are needed to quantify the direct and indirect impacts of recreational fisheries and to assess the degree of risk of associated activities to marine turtle populations.
Keywords Caretta caretta, Chelonia mydas, Eastern Gulf of Mexico, Lepidochelys kempii, marine turtles, recreational fisheries, scallop harvest, wildlife management
The supplementary material for this article is available at
https://doi.org/10.1017/S0030605318000182
Introduction
species (Crowder & Norse, 2008). Of particular concern is bycatch, the unintended capture of non-target organisms during fisheries operations, which is considered to be one of the most serious threats globally to long-lived marine megafauna such as marine turtles (Wallace et al., 2013). Further impacts from fisheries can occur from vessel traffic, which may affect the fitness of individuals, energy ex- penditure, changes in foraging activity, displacement and disturbance, and mortality (Hazel et al., 2007; Powell & Wells, 2011; Barrios-Garrido & Montiel-Villalobos, 2016). As a consequence, there has been substantial effort to evalu- ate and address the impacts of fisheries on marine mega- fauna (e.g. Zydelis et al., 2009; Lewison et al., 2014). Assessments of the interactions between sea turtles and
C
fisheries have focused mainly on commercial fisheries, with little attention to the effects of recreational fisheries (Powell & Wells, 2011; Altieri et al., 2012; Young et al., 2014). This is an issue as 12% of the world’s population fish recreationally (Cooke & Cowx, 2004). In the USA rec- reational fishing averaged over 73 million trips and c. 9 mil- lion users annually during 2007–2017 (NMFS, 2017). This may have substantial consequences, both direct and indir- ect, upon marine environments and species. The few studies conducted to date have shown that recreational fishing and related activities can have profound effects on animal popu- lations and coastal ecosystems, including depletion of fish populations and ecosystem collapse from trophic-level cas- cades (Cooke &Cowx, 2004; Altieri et al., 2012; Young et al., 2014). Recreational fisheries in marine environments are con-
NATALIE WILDERMANN,CHRISTIAN GREDZENS and MARIANA M. P. B. FUENTES (Corresponding author) Department of Earth, Ocean and Atmospheric Science, Florida State University, Tallahassee, FL 32306-4320, USA E-mail
mfuentes@fsu.edu
CHRISTOPHER SASSO National Marine Fisheries Service, Southeast Fisheries Science Center, Miami, Florida, USA
Received 23 October 2017. Revision requested 24 November 2017. Accepted 18 January 2018. First published online 3 July 2018.
centrated in coastal areas, which are also home to multiple species and populations of marine turtles. This is the case within the Big Bend Region of north-western Florida, which serves as important developmental habitat for green Chelonia mydas, Kemp’s ridley Lepidochelys kempii, and loggerhead Caretta caretta turtles (e.g. Schmid et al., 2003; Barichivich, 2006), and also supports Florida’s largest recre- ational bay scallop Argopecten irradians harvest. The scallop fishery occurs annually from late June to late September (Geiger et al., 2015), a period with water temperatures favourable for marine turtles (Schmid & Witzell, 2006).
Oryx, 2020, 54(3), 307–314 © 2018 Fauna & Flora International. This is a work of the U.S. Government and is not subject to copyright protection in the United States. doi:10.1017/S0030605318000182
ommercial, recreational and artisanal fisheries can have both direct and indirect impacts on threatened
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