Poster Session at the American Elasmobranch Society Annual Meeting 2011
Spatiotemporal Distribution of Smalltooth Sawfish, Pristis pectinata, in Florida Waters
John D. Waters, George H. Burgess, Felipe C. Carvalho, Gregg R. Poulakis, and Tonya Wiley-Lescher
Historically, smalltooth sawfish (Pristis pectinata) have been observed from Texas to New York, however high mortality levels have resulted in a diminished population and "Endangered" status under the Endangered Species Act. Since 2009, sawfish have only been reported in Florida waters in the U.S. The National Sawfish Encounter Database (NSED) documents all known encounters of smalltooth sawfish in the United States and abroad, with over 5800 records documented worldwide to date. Encounters (sightings and captures) are voluntarily reported to the NSED from researchers and the general public. Data generated include: estimated total length, location based on a qualitative confidence scale, date, and water depth. Environmental data including salinity, dissolved oxygen, and water temperatures are reported with research encounters. To better answer when, where, and how big of a sawfish people are likely to encounter in Florida waters, the NSED manager has begun investigating the NSED data using advanced regressions. For preliminary investigations, a Generalized Linear Model (GLM) was used to identify potentially important biological and environmental factors that influence sawfish distribution and habitat use using R statistics. GLM parameters tested were total length (cm), depth (m), Recovery Region, and month. 2841 reports contained all four parameters to be used in the GLMs. Preliminary models did not include environmental data to the small number of encounters containing this information.
From Florida encounters, the database shows that sawfish are observed throughout Florida but show spatial trends by life stage through the year. From research encounters, sawfish have been observed at depths from less than 1 m to over 150 m, salinity 1.98 - 38.60 ppt, dissolved oxygen 3.5 - 9.1 mg/L, water temperatures 20.90 - 33.20 o C. Since ESA protections were implemented in 2003, the database has received more Very Small and Small Juvenile encounter reports, however there has been little change in the number of Large Juvenile and Adult encounters reported. Overall, the lack of environmental data (salinity, dissolved oxygen, temperature, tide, etc.) and limited geographic range of data collected from research hinders further progress. Most of the data containing environmental measurements are of Small and Very Small Juveniles in Recovery Region H from April to July.
As a continuing project, further integration of the database is required. Future models will incorporate non-linear terms in a General Additive Model (GAM) to better fit the data. In addition, the NSED will continue to add new encounters, fact check historic records, and solicit the public to report all encounters to the NSED.