1. Movement patterns of Atlantic spotted dolphins (Stenella frontalis) and bottlenose dolphins (Tursiops truncatus) in relation to oceanographic fronts R.B. Griffin, * C. Hu +, and N.J. Griffin * * Mote Marine Laboratory + University of South Florida

2. Study Area

3. Atlantic spotted dolphin Stenella frontalis Bottlenose dolphin Tursiops truncatus

5. Methods One-day surveys approximately 140 km in length

6. Data Collected Location and abundance Digital photography for photo-identification Initial behavioral state Group follows

7. Group Follows Continuous documentation of behavioral events Sequential data—3 min intervals Periodic locations of animals when in vicinity of vessel Continuous underway surface oceanography Some radio-tagging data

8. S. frontalis dive data

9. Sea Surface Temperature 21 Feb 2000

10. Data Histogram for 19-21 March 2000 and 11-15 June 2002

11. Ocean Color (Chl) 25 Jan 2002

12. Underway SST: 12 April 2004 Sighting 6—S. frontalis

13. Surface manifestation of thermal front

14. Follow track with SST: 12 April 2004 Sighting 6—S. frontalis

15. Follow track with Chl: 12 April 2004 Sighting 6—S. frontalis

16. A B dLon dLat C Follow track with Chl: 12 April 2004 Sighting 6—S. frontalis

17. Km/deg Lon vary as a function of cos(Lat) 1 o Lat = 111.12 km 1 o Lon = 99.01 km at 27 o Lat tan angle CBA=(AC km/BC km) arctan CBA then converted to 360 o reference A B dLon dLat C

18. Tested hypothesis of uniform distribution of travel vectors, frontal vectors Tested differences in travel vectors between: 1)Possible feeding behavior 2)Season Circular statistics using Oriana (Kovach Computing Services) Rayleigh test Watson-Williams F-test Fronts and travel directions treated as axial data Tested equality of travel vectors, frontal vectors.

19. Ocean Color SST S. frontalis follows

20. Ocean Color SST T. truncatus follows

21. November-MayJune-October S. frontalis follows

22. T. truncatus follows November-MayJune-October

23. Griffin and Griffin 2003, 2004 S. frontalis in highest density between 20-30 m isobaths in winter months, lowest densities in summer, while T. truncatus did not differ by season. No seasonal variation in T. truncatus movement patterns, consistent with our earlier work.

24.  During winter months in the eastern Gulf of Mexico, S. frontalis travels primarily in a north/south direction, in same trend as frontal location. During summer, animals travel primarily in east/west direction.  Hypothesis: During winter, animals are foraging along fronts, which are better defined during this time of year. In summer, lower abundance and general east/west trend of movements suggest dolphins may be at higher densities farther from coast, with some animals making short-term foraging runs into shallower water.

25.  More work on frontal definition is needed.  Continued group follows and photo-identification are planned to understand movement patterns and behavior of continental shelf dolphins in the eastern Gulf of Mexico.

26. Harbor Branch Oceanographic Institution “Protect Wild Dolphins” Program Private donors Mote Marine Laboratory student interns