Use of encounter data to model spatio‐temporal distribution patterns of endangered smalltooth sawfish, Pristis pectinata, in the western Atlantic

Abstract

Sawfishes are among the most threatened fish species globally, with only the smalltooth sawfish (Pristis pectinata) currently regularly observed in the western Atlantic. The National Sawfish Encounter Database (NSED) documents reported encounters with sawfishes in the western Atlantic and contains 4945 reports of 8773 individual P. pectinata (1782–2011).Statistical modelling (generalized linear models and generalized additive models) and kernel density analyses were used to (1) identify spatio‐temporal patterns among encounter reports, including range reduction in the western Atlantic; (2) determine current distribution to identify areas and time periods where conservation and recovery efforts could be focused; and (3) identify and describe spatio‐temporal distribution patterns of large juveniles and adults.Pristis pectinata were found to be year‐round residents of Florida but showed relatively consistent spatial and temporal trends by life stage throughout the year. Although the historical range in the western Atlantic included coastal waters from North Carolina to Brazil, the current geographic range of the species was limited to Florida from 2001 through 2011, with occasional reports in neighbouring states, the Bahamas, and Cuba.Seasonally, encounters of all life stages peaked from March through July and annual recruitment of juveniles was apparent during the study period. Spatial hotspots based on increased numbers of encounters of large juveniles (201–340 cm) and adults (>340 cm) were identified in southern Charlotte Harbor, the Ten Thousand Islands, Florida Bay, the Atlantic side of the Florida Keys, and off St. Lucie in south‐east Florida. The analyses presented herein provide evidence of range reduction in the western Atlantic, provide an important tool for resource managers to focus research, monitoring, and conservation efforts, and may provide a framework to model and predict habitat use of other species. Copyright © 2014 John Wiley & Sons, Ltd.

Sympatric elasmobranchs and fecal samples provide insight into the trophic ecology of the smalltooth sawfish

“…Specifically, the application of stable isotope techniques on fin tissues of 2 sympatric elasmobranch species that have well-characterized diets (Snelson et al 1984, Cliff & Dudley 1991, Collins et al 2007), in conjunction with smalltooth sawfish, a variety of consumer species, and the 18S rRNA gene analysis has provi ded evidence to support the hypothesis that smalltooth sawfish feed primarily on fishes regardless of life stage. Further, this reliance on fish prey persists even though smalltooth sawfish and bull sharks Carcharhinus leucas move from estuaries to coastal habitats during their onto geny (Simpfendorfer et al 2005, Scharer et al 2012, Carlson et al 2014, Waters et al 2014. Moreover, our results support those of previous studies that suggested smalltooth sawfish and bull sharks partition their habitat while in the Charlotte Harbor estuarine system during their early life histories (see below).…”

“…Shallow, seagrass-covered carbonate mud banks are a common feature in the bay, which is inhabited by the greatest concentration of adult smalltooth sawfish in its range (Poulakis & Seitz 2004, Waters et al 2014. Florida Bay contains mud bottom, hard bottom, and macroalgal communities and has extensive red mangrove shorelines (Fernald & Purdum 1998).…”

“…For young-of-the-year and juvenile smalltooth sawfish, both random and directed sampling were conducted in the Charlotte Harbor estuarine system during the day using a 183 × 3 m center-bag haul seine and gill nets ranging in length from 30.5 to 183 m (detailed gear descriptions and sampling protocols may be found in Poulakis et al 2011). For adult smalltooth sawfish, bottom longlines consisting of 4.0 mm monofilament mainline and 50 to 100 gangions were deployed during May and July 2011 in areas of Florida Bay where adults are known to occur (Poulakis & Seitz 2004, Waters et al 2014. Gangions were terminated with 16/0 non-offset circle hooks baited with ladyfish Elops saurus, little tunny Euthynnus alletteratus, or Atlantic mackerel Scomber scombrus.…”

Environmental DNA detects Critically Endangered largetooth sawfish in the wild

“…Traditional fishing surveys using fishing gear (gillnets, lines) have proved useful (Thorburn et al 2007, Wiley & Simpfendorfer 2007, but are time consuming, logistically difficult in remote areas, expensive and may not detect animals even if they are present. Public encounter data have also been used to determine the distribution and habitat associations of smalltooth sawfish Pristis pectinata in Florida (Poulakis & Seitz 2004, Wiley & Simpfendorfer 2010, Waters et al 2014). This approach is less expensive, but relies on the distribution of observational effort, considerable outreach, the ability of the public to identify species correctly and their willingness to report encounters (particularly given the apprehension over reporting the capture of a listed protected species) to gather sufficient data (Wiley & Simpfendorfer 2010).…”

Facultative parthenogenesis in a critically endangered wild vertebrate

“…It currently occurs primarily in southwest Florida, U.S. [6], where it may have stabilized and started to recover (http://www.iucnredlist. org/details/18175/0 ).…”