Abstract
Understanding how endangered marine species rely on coastal habitats is vital for recovery planning. The smalltooth sawfish (Pristis pectinata ) is one of several critically endangered sawfishes worldwide known to use coastal habitats during their early life history. In a Florida estuary, juveniles were monitored to characterize seasonality, recruitment, and habitat use. Sawfish were captured year round. Captures of neonates allowed determination of the size at birth and the timing of parturition which peaked between April and May. Although sampling occurred throughout the estuary, five locations called hotspots had the greatest catch rates. Most juveniles had an affinity for water <1 m deep, water >30 degree C, dissolved oxygen concentrations >6 mg L super(-1), and salinities between 18 and 30 psu. Movements of juveniles were monitored over two years using acoustic tags and an array of acoustic receivers distributed in both main-stem habitats and nonmain-stem habitats of the highly altered, flow-managed tidal Caloosahatchee River, Florida. Over three-fourths of the P. pectinata used non-main-stem habitats, and almost half used these habitats more than 10% of the time. Daily activity space of P. pectinata was 0.7 km of river distance and they remained in the nursery under a wide range of environmental conditions. Sawfish moved upriver as salinity increased. Salinity patterns had a greater effect on the distribution of <1-year-old P. pectinata than on that of older individuals. Research on P. pectinata has shown that hotspots within the nurseries are disproportionally important during early life history. The objectives of this portion of the study were to determine whether selection of a hotspot by 10 small juveniles was maternally- or offspring-driven and document subsequent use of this and other known hotspots by these individuals. Analyses of microsatellite and mitochondrial DNA suggested the presence of four full-sibling dyads and a single half-sibling pair, along with several unrelated individuals; this implied that at least four mothers contributed to the group (selection of the hotspot was offspring-driven). On average, juveniles spent 61% of their time at one hotspot. Larger-scale movements between hotspots occurred after passage of a tropical storm and smaller-scale movements exhibited a diel pattern at two hotspots. The official Smalltooth Sawfish Recovery Plan was published in 2009 by the National Marine Fisheries Service. Included in the recovery plan were specific research objectives that need to be met to help protect and recover the remaining P. pectinata population. This dissertation addresses all or part of at least 31 of the research objectives (i.e., Action Items) listed in the recovery plan that pertain to the juvenile life stages of P. pectinata.