Documentation of Atlantic Tarpon (Megalops Atlanticus) Space Use and Move Persistence in the Northern Gulf of Mexico Facilitated by Angler Advocates
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Received: 25 June 2020 Revised: 5 November 2020 Accepted: 10 November 2020 DOI: 10.1111/csp2.331 PERSPECTIVES AND NOTES Documentation of Atlantic tarpon (Megalops atlanticus) space use and move persistence in the northern Gulf of Mexico facilitated by angler advocates J. Marcus Drymon1,2 | Matthew B. Jargowsky1,2 | Michael A. Dance3 | Mitchell Lovell3 | Crystal LouAllen Hightower4 | Amanda E. Jefferson1,2 | Andrea M. Kroetz4,5 | Sean P. Powers4 1Coastal Research and Extension Center, Mississippi State University, Biloxi, Abstract Mississippi Atlantic tarpon (Megalops atlanticus, hereafter tarpon) are facing a multitude 2Mississippi-Alabama Sea Grant of stressors and are considered Vulnerable by the IUCN; however, significant Consortium, Ocean Springs, Mississippi gaps remain in our understanding of tarpon space use and movement. From 3Department of Oceanography and 2018 to 2019, citizen scientists facilitated tagging of 23 tarpon with SPOT tags Coastal Sciences, Louisiana State University, Baton Rouge, Louisiana to examine space use and movement across the northern Gulf of Mexico. 4Department of Marine Sciences, University Movement-based kernel densities were used to estimate simplified biased ran- of South Alabama, Mobile, Alabama dom bridge-based utilization distributions and a joint move persistence model 5 Southeast Fisheries Science Center/ was used to estimate a behavioral index for each fish. Tarpon showed consis- Riverside Technology, Inc., National Marine Fisheries Service, Panama City, Florida tent east–west movement from the Alabama/Florida border to Louisiana, and utilization distributions were highest in the Mississippi River Delta. Move per- Correspondence sistence was highest in Alabama and Mississippi and lowest in Louisiana. Our J. Marcus Drymon, Mississippi State University, Coastal Research and examination of tarpon space use and movement indicates that Louisiana is a Extension Center, 1815 Popps Ferry Road, critical, yet understudied, part of their range. Biloxi, MS 39532. Email: [email protected] KEYWORDS Funding information citizen science, Louisiana, migration, satellite telemetry, SPOT tag Alabama Coastal Conservation Association; Alabama Department of Conservation and Natural Resources Marine Resources Division; Billy Cenac; Chandeleur Brewing Company; Louisiana Coastal Conservation Association; Louisiana Wildlife and Fisheries Foundation; Mark Blanchard; Mississippi- Alabama Sea Grant Consortium 1 | INTRODUCTION economic significance to anglers across the Atlantic Ocean (Ault, 2008), especially in the Gulf of Mexico Atlantic tarpon (Megalops atlanticus, hereafter tarpon) (Davis, 2017). Unfortunately, tarpon populations in the is a highly migratory species with deep cultural and Gulf of Mexico are experiencing multiple stressors This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2020 The Authors. Conservation Science and Practice published by Wiley Periodicals LLC. on behalf of Society for Conservation Biology Conservation Science and Practice. 2020;e331. wileyonlinelibrary.com/journal/csp2 1of9 https://doi.org/10.1111/csp2.331 2of9 DRYMON ET AL. including habitat loss and degradation, reductions in 2 | METHODS water quality, and lethal (and sublethal) effects from commercial and recreational fisheries (Adams et al., 2.1 | Tagging 2014). Compounding these stressors, tarpon embody a suite of life history characteristics, such as long life Tarpon were captured in collaboration with anglers in span, low adult mortality, and large body size, all of the Alabama Deep Sea Fishing Rodeo tarpon catch-and- which lower compensatory capacity (Kindsvater, Man- release category, anglers in the Mobile Rotary and gel, Reynolds, & Dulvy, 2016). Consequently, tarpon are Mobile-Sunrise Rotary Tarpon Tournament, and mem- currently listed as Vulnerable by the International bers of the Grand Isle Tarpon Club (Table 1) using hook- Union for the Conservation of Nature (IUCN, Adams and-line gear. Once hooked, fish were brought alongside et al., 2014). the boat as quickly as possible and secured anteriorly Migration and movement of tarpon are well docu- with a lip grip and posteriorly with a tailer. While the fish mented. A recent synthesis of multi-year tagging efforts was submerged and oriented with its head into the cur- has revealed large-scale movements and partial migra- rent, fork length (FL) and girth (both in cm) were mea- tions by this species (Luo et al., 2020). By analyzing a sured, and a scale was removed to facilitate tag insertion combination of vertical habitat profiles and horizontal following Luo et al. (2020). Next, a towed Smart Position position estimates, the authors determined that areas in and Temperature (SPOT) tag (Wildlife Computers) was the western (Vera Cruz, Mexico) and eastern (Florida attached via a 60 cm stainless tether covered with medi- Straits) Gulf of Mexico long suspected as important may cal grade Tygon tubing, terminating in a 64 mm titanium indeed serve as spawning locations (Luo et al., 2020); anchor (Fish 1–18) or a Domeier anchor (Fish 19–23), however, telemetered fish from Louisiana were lacking. both from Wildlife Computers. The fish was then held Larval, juvenile, sub-adult, and adult tarpon have all alongside the vessel until it resisted, at which point it was been documented off the coast of Louisiana (Stein III, released. A video detailing the cooperative tagging pro- Shenker, & O'Connell, 2016), including concurrent male cess can be viewed here. and female spawning-capable individuals (Stein III, Brown-Peterson, Franks, & O'Connell, 2012). Collec- tively, these lines of evidence suggest that the northern 2.2 | Data filtration Gulf of Mexico, particularly Louisiana, represents an important, yet understudied, region for this species. As facultative air-breathing fish, tarpon often come to the The northern Gulf of Mexico is home to several fish- surface to gulp air in what is termed “rolling behavior” ing rodeos, annual events that support large gatherings of (Babcock, 1951). This behavior enabled the SPOT tags to recreational anglers. Increasingly, these anglers are rec- transmit data to the Argos Satellite Platform (CLS Amer- ognized as conservation partners (Granek et al., 2008), ica, Inc). Kalman filters were applied to Doppler-derived often developing and voluntarily implementing resource- position estimates within the Argos platform. The conserving guidelines such as catch-and-release (Cooke, resulting position estimates were then downloaded from Suski, Arlinghaus, & Danylchuk, 2013). Consequently, the Wildlife Computers portal and filtered using a multi- rodeo anglers afford unique opportunities for scientists to step process. First, all Z position estimates were elimi- study fish movement. Since tarpon are notoriously elu- nated so that only position estimates with location sive fish that require substantial angler expertise to cap- classes A, B, 0, 1, 2, and 3 were retained. Next, land-based ture, scientists can benefit from working in concert with position estimates were removed, as were estimates indi- organized tarpon fishing tournaments that provide access cating a swimming speed in excess of 2 m/s (Weng et al., to fish, along with opportunities to interact with invested 2005). To eliminate position estimates from floating stakeholders (Humston, Ault, Schratwieser, Larkin, & SPOT tags that had detached from the fish, we followed Luo, 2008). criteria outlined in Hearn et al. (2013). Specifically, tags Given the cultural significance and inherent vulner- that repeatedly reached their maximum transmissions ability of tarpon, we sought to further investigate this (250) during an approximate three-hour period, a period species by partnering with anglers from fishing rodeos established by the hour the fish was originally tagged and a tarpon-focused club in the northern Gulf of Mex- (i.e., the start of its 24-hr cycle), were deemed detached. ico, all of which have implemented tarpon catch-and- This threshold was identified as the time needed for a tag release categories. In collaboration with these anglers, in constant communication with a satellite to reach its our objectives were to use satellite telemetry to examine maximum daily transmission limit and was indicative of tarpon space use and movement in the northern Gulf a detached tag floating at the surface (Hearn et al., 2013). of Mexico. The first location after detachment was used as a final, or DRYMON ET AL. 3of9 TABLE 1 Summarized SPOT tag deployment information from 23 tagged tarpon Est. Last Last Fish FL Weight Deployment Deployment transmission transmission Days at ID Angler PTT (cm) (kg) date location date location liberty 1 Chris Tew 169305 155 34.9 7/20/2018 Gulf State 8/3/2018 Lake Borgne, LA 14 Pier, AL 2 Chris Tew 169306 158 37.2 7/20/2018 Gulf State 8/5/2018 Mississippi River 16 Pier, AL Delta 3 Larry Eberly 169307 160 46.7 7/20/2018 Gulf State 8/18/2018 Mississippi River 29 Pier, AL Delta 4 Tom Eberly 169308 168 49.0 7/20/2018 Gulf State 8/22/2018 Breton Island, LA 33 Pier, AL 5 Larry Eberly 169310 158 39.0 7/20/2018 Gulf State 8/8/2018 Mississippi River 19 Pier, AL Delta 6 Tom Eberly 169311 148 37.6 7/20/2018 Gulf State 8/1/2018 Mississippi River 12 Pier, AL Delta 7 Brad Caban 169303 164 39.0 7/21/2018 Gulf State 9/7/2018 Mississippi River 48 Pier, AL Delta 8 Hayden Olds 169312 187 59.4 7/21/2018 Gulf State 7/23/2018 Petit Bois Pass, AL