Benthic Habitat Mapping of Cardigan Bay, in relation to the distribution of the Bottlenose Dolphin (Tursiops truncatus). A dissertation submitted in part candidature for the Degree of B.Sc., Institute of Biological Sciences, University of Wales, Aberystwyth. By Hannah Elizabeth Vallin © Sarah Perry May 2011 1 Acknowledgments I would like to give my thanks to several people who made contributions to this study being carried out. Many thanks to be given firstly to the people of Cardigan Bay Marine Wild life centre who made this project possible, for providing the resources and technological equipment needed to carry out the investigation and for their wealth of knowledge of Cardigan Bay and its local wildlife. With a big special thanks to Steve Hartley providing and allowing the survey to be carried out on board the Sulaire boat. Also, to Sarah Perry for her time and guidance throughout, in particular providing an insight to the OLEX system and GIS software. To Laura Mears and the many volunteers that contributed to participating in the sightings surveys during the summer, and for all their advice and support. I would like to thank my dissertation supervisor Dr. Helen Marshall for providing useful advice, support, and insightful comments to writing the report, as well as various staff members of Aberystwyth University who provided educational support. Finally many thanks to my family and friends who have supported me greatly for the duration. Thankyou. i Abstract The distribution and behaviour of many marine organisms such the bottlenose dolphin Tursiops truncates, are influenced by the benthic habitat features, environmental factors and affinities between species of their surrounding habitats. Cardigan Bay along the West coast of Wales is a thriving marine environment. Benthic habitat mapping of the seabed allows assumptions to be made between particular behaviours such as foraging and feeding in relation to varying bathymetric characteristics on a fine-scale environment. In addition to studying the bathymetric layout along Cardigan Bay the extent of the daily oscillating tidal changes were also investigated. The purpose of this was to see if the spring or neap and ebb or flood of a tide had any effect on the behaviour and activity level of T. truncates. Data was collected over a three month summer period whilst onboard a research vessel. Cetacean sightings data were collected, recording exact locations and behaviours of T. truncates. Following dedicated transect routes from New Quay to Ynys-Lochtyn, using specialised equipment, the boats own echo-sounder readings and Global Positioning System were used to continuously collect and calculate depth readings to create a 3-D visual image of the sea floor indicating any bathymetric features. T. truncatus spent the majority of observational time foraging with over 79% of individuals displaying this behaviour, and were observed most frequently around New Quay and Ynys Lochtyn headlands as well as within New Quay bay. Benthic mapping of the area gave rise to two particular features of interest just off New Quay headland, indicating regions of greater depths and steeper gradients, displaying gully features. However, these features do not indicate any association with increased foraging or feeding behaviour. The ebb and flood variation of diurnal tides have a strong influence on the occurrence of T. truncatus displaying foraging and feeding behaviours within Cardigan Bay. However, there is no significant difference between the monthly spring and neap tidal oscillations, and effects on the foraging and feeding behaviour of T. truncatus. There was also no significant difference between the tidal cycle and leaping and milling behaviour of T. truncatus. Throughout the survey period a high abundance of cetaceans within this coastal region were observed, the findings and bathymetric features supports the need for the continued conservation for T. truncatus within their home range of Cardigan Bay. Key words: Bottlenose dolphin (Tursiops truncates), bathymetric features, Cardigan Bay, tidal cycles, foraging, feeding. ii Table of Contents Acknowledgments ................................................................................................... i Abstract..................................................................................................................... ii Table of contents...................................................................................................... iii List of appendices..................................................................................................... iv List of tables............................................................................................................... v List of figures............................................................................................................. vi 1. Introduction .......................................................................................................... 1 1.1 Technological advancements............................................................................... 2 1.2 Benthic mapping studies in relation to cetacean distribution and behaviour.. 3 1.3 Tidal influences on cetacean distribution ............................................................ 6 2. Study Area................................................................................................................. 7 2.1 Cardigan Bay........................................................................................................... 7 2.2 Special Areas of Conservation.................................................................................7 2.3 Investigated Area...................................................................................................... 9 2.4 Wild life of Cardigan Bay........................................................................................ 10 3. Aims and Objectives.....................................................................................................12 4. Methods..........................................................................................................................13 4.1 Boat based surveys..................................................................................................... 13 4.2 Survey transect lines.................................................................................................. 13 iii 4.3 Effort data.................................................................................................................. 16 4.4 Sightings data............................................................................................................. 16 4.5 Data analysis................................................................................................................ 21 4.5.1 OLEX data................................................................................................................ 21 4.5.2 Sightings data analysis.............................................................................................. 21 4.5.3 Statistical analysis..................................................................................................... 22 5. Results............................................................................................................................. 23 5.1 Bathymetric maps......................................................................................................... 23 5.2 Visual display of sightings data................................................................................... 31 5.3 Behaviour and tide analysis.......................................................................................... 33 6. Discussion......................................................................................................................... 38 6.2 tidal influences on Tursiops truncatus........................................................................... 42 7. Conclusion.......................................................................................................................... 45 7.1 limitations and further studies....................................................................................... 46 8. References.......................................................................................................................... 48 List of Appendices Appendix 1: Additional OLEX and Arc map images. Appendix 2: Raw sightings information provided on CD and all statistical analysis output from Minitab of behavioural tide analysis. iv List of tables Table 1 Area distances of transect survey area....................................................... 14 Table 2 Ethogram of Tursiops truncatus behaviours ............................................. 17-18 v List of figures Fig. 1 Map of Wales sowing Cardigan bay and the Special Areas of Conservation........ 8 Fig. 2 Map of New Quay and Ynys-Lochtyn...................................................................... 10 Fig. 3 Image of the research boat, the Sulaire.................................................................... 13 Fig. 4 OLEX image of the transect survey area of Cardigan Bay.................................... 15 Image A-H Tursiops truncatus displaying a range of behaviours............................... 18-20 Fig. 5 Image to show seabed features off New Quay headland, with particular interest looking at a deeper gully feature........................................................................................ 23 Fig.6(A)