Abiotic affinities and spatiotemporal distribution of the endangered smalltooth sawfish, Pristis pectinata, in a south-western Florida nursery

Abstract

Understanding how endangered marine species rely on coastal habitats is vital for population recovery planning. The smalltooth sawfish (Pristis pectinata) is one of several critically endangered sawfishes worldwide known to use estuaries and rivers during their early life history. In a Florida estuary designated as critical habitat by the USA government, juveniles were monitored to characterise seasonality, recruitment, and habitat use. Stretched total length ranged from 671 to 2172 mm (n = 137, mean = 1248 mm). Sawfish were captured year round. Captures of neonates with embryonic rostral sheaths allowed refinement of the size at birth (671–812 mm) and confirmed a protracted timing of parturition (November–July), which peaked between April and May. Although sampling occurred throughout the estuary, five locations had the greatest catch rates. Most juvenile sawfish had an affinity for water <1 m deep, water >30°C, dissolved oxygen >6 mg L–1, and salinity between 18 and 30. Greater catch rates for sawfish >1 year old were associated with shoreline habitats with overhanging vegetation such as mangroves. These results detail habitat use within a recognised nursery that can be used for conservation of the first endangered marine fish species in the USA.

Kemp's Ridley Sea Turtle Saga and Setback: Novel Analyses of Cumulative Hatchlings Released and Time-Lagged Annual Nests in Tamaulipas, Mexico

“…Researchers have identified several areas within the Charlotte Harbor Estuary that are disproportionately more important to juvenile smalltooth sawfish, based on intra-or inter-annual (within or between year) capture rates during random sampling events within the estuary (Poulakis 2012;Poulakis et al 2011). These areas were termed "hotspots" and also correspond with areas where public encounters are most frequently reported.…”

All nurseries are not created equal: large-scale habitat use patterns in two smalltooth sawfish nurseries

“…The Caloosahatchee and Peace rivers were de fined as smalltooth sawfish Pristis pectinata nurseries by Poulakis et al (2011) based on criteria defined for elasmobranchs by Heupel et al (2007). Within these nurseries, multiple lines of evidence gathered over almost a decade have documented specific areas of high use, or nursery hotspots, for juvenile smalltooth sawfish (Simpfendorfer et al 2010, 2013, 2016, Nagelkerken et al 2015, Hollensead et al 2016).…”

“…Random sampling was conducted during the day from February through September (period of highest catch rates; Poulakis et al 2011) using two 30.5 m (100 ft) or two 61 m (200 ft) gill nets with 102 mm (4 in.) stretch monofilament mesh set perpendicular to shore about 100 m apart.…”

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

“…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.…”

“…In the Charlotte Harbor estuarine system, both species are born within the Caloosahatchee River and other rivers where they have affinities for different salinities (smalltooth sawfish: 18 to 30 psu, Poulakis et al 2011;bull shark: 7 to 20 psu, Heupel & Simpfendorfer 2008). However, bull sharks have a tendency to move out of the Caloosahatchee River during their first year, while smalltooth sawfish remain in the river for as long as 3 yr (Simpfendorfer et al 2005, likely explaining the lack of overlap between isotopic ellipses on the δ 13 C axis.…”