Long-term site fidelity of endangered small-tooth sawfish (Pristis pectinata) from different mothers

Abstract

Understanding how endangered species use nursery habitats is vital for recovery planning. Research on the smalltooth sawfish (Pristis pectinata) has shown that areas of estuarine nurseries, called hotspots, are used consistently. The objectives of our study were 1) to determine whether 10 young-of-the-year smalltooth sawfish in an artificial, non-main-stem portion (i.e., a seawall canal system) of a hotspot were descended from one or different mothers and 2) to document long-term habitat use by these individuals. At least 4 mothers contributed to the group, which comprised siblings, half-siblings, and unrelated individuals. Young sawfish exhibited site fidelity to their capture location, spending 61% of their time there. Continuous residency lasted as long as 86 days, but these fish made small-scale diel (< 1 river km) movements between the capture location (day) and the nearby main-riverstem portion of the hotspot (night). Larger-scale (5-7 river km) downriver and upriver relocations between the capture location and the river mouth, including 2 other known natural hotspots, occurred after a tropical storm. This research shows that 1) young-of-the-year from different mothers can have high site fidelity at specific locations within a nursery hotspot and 2) these hotspots can be important for young-of-the-year even when there is a drastic change in freshwater inflow.