Nova Southeastern University NSUWorks HCNSO Student Theses and Dissertations HCNSO Student Work 3-28-2017 Age and Growth of Whale Sharks (Rhincodon typus) near the South Ari Atoll, Maldives Cameron T. Perry Nova Southeastern University, [email protected] Follow this and additional works at: https://nsuworks.nova.edu/occ_stuetd Part of the Marine Biology Commons, and the Oceanography and Atmospheric Sciences and Meteorology Commons Share Feedback About This Item NSUWorks Citation Cameron T. Perry. 2017. Age and Growth of Whale Sharks (Rhincodon typus) near the South Ari Atoll, Maldives. Master's thesis. Nova Southeastern University. Retrieved from NSUWorks, . (437) https://nsuworks.nova.edu/occ_stuetd/437. This Thesis is brought to you by the HCNSO Student Work at NSUWorks. It has been accepted for inclusion in HCNSO Student Theses and Dissertations by an authorized administrator of NSUWorks. For more information, please contact [email protected]. Age and Growth of Whale Sharks (Rhincodon typus) near the South Ari Atoll, Maldives By Cameron T. Perry Submitted to the Faculty of Halmos College of Natural Sciences and Oceanography in partial fulfillment of the requirements for the degree of Master of Science with a specialty in: Marine Biology and Coastal Zone Management Nova Southeastern University Thesis of Cameron T. Perry Submitted in Partial Fulfillment of the Requirements for the Degree of Masters of Science: Marine Biology and Coastal Zone Management Cameron T. Perry Nova Southeastern University Halmos College of Natural Sciences and Oceanography March 2017 Approved: Thesis Committee Major Professor: ______________________________ Mahmood Shivji, Ph.D. Committee Member: ___________________________ Joana Figueiredo, Ph.D. Committee Member: ___________________________ Bradley Wetherbee, Ph. Table of Contents LIST OF FIGURES .................................................................................................................... V LIST OF TABLES ................................................................................................................... VII ABSTRACT ........................................................................................................................... VII 1. INTRODUCTION .............................................................................................................1 2. OBJECTIVES ....................................................................................................................5 3. METHODS ......................................................................................................................6 3.1 STUDY AREA ....................................................................................................................... 6 3.2 STUDY POPULATION ............................................................................................................ 7 3.3 SURVEYS ............................................................................................................................ 7 3.3.1 Visual Estimates ......................................................................................................... 7 3.3.2 Laser Photogrammetry............................................................................................... 7 3.3.3 Tape Measurements ................................................................................................... 8 3.3.4 Photo Identification .................................................................................................... 9 3.3.5 Sex Determination .................................................................................................... 11 3.4 STATISTICAL ANALYSES ....................................................................................................... 12 3.4.1 Regression Analysis .................................................................................................. 12 3.4.2 Precision of tape and laser measurements .............................................................. 12 3.4.3 Differences between New, Transient and Returning Sharks .................................... 12 3.4.4 Growth parameter determination ........................................................................... 13 3.4.5 Age and Growth ....................................................................................................... 13 3.5 JUSTIFICATION OF THE MODEL ............................................................................................. 14 3.6 LONGEVITY ....................................................................................................................... 15 3.7 AGE AT MATURITY ............................................................................................................ 15 iii 4. RESULTS ...................................................................................................................... 16 4.1 REGRESSION ANALYSIS ....................................................................................................... 16 4.1.1 Visual and Laser Measurements Regression ............................................................ 16 4.1.2 Tape and Visual Measurements Regression............................................................. 17 4.1.3 Tape and Laser Measurements Regression .............................................................. 18 4.2 PRECISION OF TAPE AND LASER MEASUREMENTS ................................................................... 19 4.3 AVERAGE SIZES OF NEW, TRANSIENT AND RETURNING SHARKS ................................................ 19 4.4 GROWTH PARAMETERS ...................................................................................................... 25 4.5 AGE AND LENGTH.............................................................................................................. 25 4.6 GROWTH RATES ................................................................................................................ 26 4.7 JUSTIFICATION OF MODEL .................................................................................................. 28 4.8 AGE AT MATURITY AND LONGEVITY ..................................................................................... 30 5. DISCUSSION ................................................................................................................. 30 5.1 COMPARISON OF LENGTH MEASUREMENT METHODS ............................................................... 30 5.2 AVERAGE SIZES OF NEW, TRANSIENT AND RETURNING SHARKS ................................................ 31 5.3 GROWTH PARAMETERS ...................................................................................................... 32 5.4 AGE AT MATURITY AND LONGEVITY ..................................................................................... 34 6. CONCLUSIONS ............................................................................................................. 40 7. ACKNOWLEDGEMENTS ................................................................................................ 43 8. LITERATURE CITED ....................................................................................................... 44 9. APPENDIX A. ................................................................................................................ 49 iv List of Figures FIGURE 1: SOUTH ARI ATOLL, MALDIVES (FIGURE MODIFIED FROM RILEY ET AL., 2010). THE MALDIVES (A), THE ARI ATOLL (RED BOX IN B) AND SPECIFICALLY THE SOUTH ARI ATOLL (C) INDICATES THE LOCATION OF MY STUDY. ............................................ 6 FIGURE 2: LASER PHOTOGRAMMETRY USED TO DETERMINE TOTAL LENGTH. ...................... 8 FIGURE 3: TAPE MEASUREMENT METHOD USED TO DETERMINE TOTAL LENGTH. ................. 9 FIGURE 4: IDENTIFICATION PHOTOGRAPH. ........................................................................ 10 FIGURE 5: MATCH OF IDENTIFICATION PHOTOGRAPH AND THE CORRESPONDING PHOTOGRAPHS IN THE MWSRP DATABASE. .............................................................. 10 FIGURE 6: SEX DETERMINATION. MALES ARE IDENTIFIED BY THE PRESENCE OF TWO EXTERNAL ORGANS, CALLED CLASPERS (A). FEMALES ARE IDENTIFIED BY THE ABSENCE OF THESE ORGANS (B). ................................................................................ 11 FIGURE 7: RELATIONSHIP BETWEEN VISUAL AND LASER MEASUREMENT METHODS. A RED LINE WITH A SLOPE OF ONE (PERFECT MATCH) ADDED FOR REFERENCE. ..................... 16 FIGURE 8: RELATIONSHIP BETWEEN TAPE AND VISUAL MEASUREMENT METHODS. A RED LINE WITH A SLOPE OF ONE (PERFECT MATCH) ADDED FOR REFERENCE. ..................... 17 FIGURE 9: RELATIONSHIP BETWEEN LASER AND TAPE MEASUREMENT METHODS. A RED LINE WITH A SLOPE OF ONE (PERFECT MATCH) ADDED FOR REFERENCE. ..................... 18 FIGURE 10: AVERAGE NUMBER OF NEW SHARKS SEEN PER SEARCH EFFORT (DAYS) THROUGHOUT EACH MONTH AND YEAR OF STUDY. .................................................... 20 FIGURE 11: SIZE FREQUENCY OF NEW SHARKS SEEN PER YEAR. THE RED LINE ASSOCIATED WITH EACH YEAR IS THE AVERAGE SIZE OF NEW SHARKS SEEN DURING THAT YEAR. .. 21 FIGURE 12: SIZE FREQUENCY OF TRANSIENT SHARKS SEEN PER YEAR. THE RED LINE ASSOCIATED WITH EACH YEAR IS THE AVERAGE SIZE OF TRANSIENT SHARKS SEEN DURING THAT YEAR. ................................................................................................... 22 FIGURE 13: SIZE FREQUENCY OF RETURNING SHARKS SEEN PER YEAR. THE RED LINE ASSOCIATED WITH EACH YEAR IS THE AVERAGE SIZE OF RETURNING SHARKS SEEN DURING THAT YEAR. ..................................................................................................