Large-scale space use of large juvenile and adult smalltooth sawfish Pristis pectinata: implications for management

Abstract

The smalltooth sawfish Pristis pectinata is an endangered species endemic to the Atlantic Ocean. The only known viable populations occur in the USA along both coasts of Florida and in the western Bahamas. Little is known about habitat use and movement ecology of large juvenile and adult smalltooth sawfish. Although Critical Habitat—a management designation in the USA—has been identified for small juveniles, it has yet to be identified for these life stages. Between May 2016 and April 2019, we used passive acoustic telemetry and 3 large data sharing networks of receivers to track movements of 43 large juvenile and adult smalltooth sawfish. During this study, 24 females and 19 males were implanted with transmitters with estimated 4 or 10 yr battery lives. These tagged individuals were detected off the southeastern USA on 461 receivers ranging from off the coast of Brunswick, Georgia, to the lower Florida Keys, and along the Gulf coast to Apalachee Bay, Florida. Seasonal migrations were undertaken by 58% (43% mature; 57% immature) of the tagged individuals, with the remainder being apparent residents of their tagging locations. Tagged sawfish from both size classes and of both sexes migrated, which indicates that neither sex nor length is a predictor of whether a sawfish will migrate or not. Although both coasts of Florida were used for migration, most individuals consistently used the same coast when they migrated. The areas surrounding Boca Grande, Cape Canaveral, and the lower Florida Keys were heavily visited sites that could be further evaluated as potential Critical Habitat for these life stages. Understanding the movement patterns of this Critically Endangered species is essential for creating policies to protect areas important for promoting growth of the population.

Environmental DNA evidence of the Critically Endangered smalltooth sawfish, Pristis pectinata, in historically occupied US waters

“…Scientific survey methods such as gill nets, bottom longlines, and electronic tagging have been used to assess the contemporary occurrence of P. pectinata in their core range in SWFL (Poulakis et al, 2011; Graham et al, 2021). However, such methods may not be effective in the non‐core range, where the species may be re‐establishing (Magnuson, Benson & McLain, 1994; Lewison et al, 2004).…”

Commercial fishery bycatch risk for large juvenile and adult smalltooth sawfish (Pristis pectinata) in Florida waters

“…From May 2016 to September 2019, individuals were detected on 461 acoustic receivers ranging from off the coast of Brunswick, Georgia, to the lower Florida Keys and along the Gulf of Mexico to Apalachee Bay, Florida; these receivers were divided into regions (Figure 1; Graham et al, 2021). In general, sawfish moved north from the Keys in spring (March–May) on both Florida coasts and travelled to Charlotte Harbor on the Gulf coast and to Cape Canaveral on the Atlantic coast.…”

Sawfish, Read in Tooth and Saw: rostral teeth as endogenous chemical records of movement and life-history in a critically endangered species

“…Current knowledge of the locations of sawfish populations is limited in many areas, with particularly little detailed understanding of nursery areas outside of a few heavily studied nursery hotspots in Australia (largetooth sawfish, green sawfish) and Florida (smalltooth sawfish) (Poulakis et al, 2011; Feldheim et al, 2017; Huston et al, 2017; Scharer et al, 2017). Feeding areas, or movement corridors for adult sawfish of all species are less well studied (Graham et al, 2020).…”

“…However, community-based approaches and opportunistic catch data is often of low-resolution. Further, designation of important habitat is often done without the opportunity for thorough assessment of local behavior and ecology, as evidenced by habitat designation of the smalltooth sawfish in the United States which is only now being supplemented by direct studies of movement and location using telemetry (Wiley & Simpfendorfer, 2010; Norton et al, 2012; Graham et al, 2020), and presence/absence studies using environmental DNA (eDNA) techniques (Simpfendorfer et al, 2016; Lehman et al, 2020).…”