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  • Hanauma Bay Biological Carrying Capacity Survey 1st Annual Report: May 2018 - May 2019

    For:

    City and County of Honolulu Parks and Recreation Department Hanauma Bay Nature Preserve Honolulu, Hawai‘i Location:

    100 Hanauma Bay Road 96825

    Prepared for:

    City and County of Honolulu: Parks and Recreation Hawai‘i Board of Land and Natural Resources

    Prepared by:

    Sarah J. L. Severino M.Sc. Ku‘ulei S. Rodgers Ph.D.

    University of Hawai‘i: Hawai‘i Institute of Marine Biology

    Coral Reef Ecology Laboratory/Coral Reef Assessment and Monitoring Program

    May 2019

  • II

    Table of Contents TITLE PAGE…………………………………………………………………………...…………I

    TABLE OF CONTENTS……………………………………………………………………..…II

    LIST OF TABLES………………………………………………………………………………III

    LIST OF FIGURES……………………………………………………………………….……IV

    EXECUTIVE SUMMARY……………………………………………………………….………1

    INTRODUCTION……………………………………………………………………..…………2

    PROJECTED SCOPE OF WORK DETAILS…………………………………………………5

    Task 1: Find sources and references of historical data. ……………………………6

    Summary of studies performed within Hanauma Bay with added

    discussion of current levels of human use while each study was being

    performed. ………………………………………………………….……………6

    Historical Fish Biomass…………………………………………………6

    Historical Coral Cover…………………………………………………..9

    Historical Environmental Studies…………………………….………10

    Task 2: Human Counts………………………………………………………..………11

    Task 3: Direct Human Impact Monitoring and Experimentation……………….…13

    Coral Skeleton Experiment………………………………………………...…13

    Secchi Disk Measurements……………………………………..……………23

    Sediment Trap Accumulation…………………………………………………28

    Coral Colony Surveys…………………………………………………………31

    Coral Recruitment Surveys………………………………………………...…35

    Task 4: Analysis of yearly monitoring of CRAMP sites. ……………..……………35

    Comparison of Hanauma Bay CRAMP sites over time. ………..…………35

    Task 5: Analysis of temperature data from inner reef flat.………………...………36

    Current temperature patterns and comparison between seasons…….…36

    Predictive assessment of bleaching impacts and patterns.………….……37

    Discussion and Findings………………………………………………………………39

    Management & Educational Recommendations…………………………………...42

    ACKNOWLEDGMENTS………………………………………………………………………49

    Budgetary Spending……………………………………………………………………..……49

    Materials and Supplies…………………………………………………………………..……50

    REFERENCES…………………………………………………………………………………51

    APPENDICES……………………………………………………………………………….…53 A. Annotated Bibliography and Timeline……………………………………………………...………53

    B. Human counts data.………………………………………………………………………..………..97

    C. Coral trampling breakage data.……………………………………………………………………103

    D. Secchi water clarity measurement data………………………………………………….………109

    E. Sediment accumulation data.…………………………………………………………...…………115

    F. Adult coral survey data………………………………………………………………………..……117

    G. CRAMP data………………………………………………………………………….……………..123

    H. Temperature data………………………………………………………………….……………….124

  • III

    List of Tables Table Page

    1. Summary of data collected in visual count surveys and coral trampling

    experiments…………………………………………………………………………..…….11

    2. Coral breakage, coral cover, rugosity and human use (swimmers + waders)

    at the HBNP………………………………………………………………………………..17

    3. Results of correlation test between the June and October visual water

    clarity and environmental parameters………………………………………………...…25

    4. Coral cover (m2) represented in each of the permanent transects

    within Hanauma Bay as of December, 2018……………………………………………33

    5. Temperature (°C) average, minimum and maximum for temperatures taken

    throughout the year, only summer months, and only winter months within

    Backdoors, Keyhole, Channel, and the offshore CRAMP site……………………..…37

    6. Comparison of inner reef coral cover between Brock & Kam (2000) carrying

    capacity report and 2019 carrying capacity report…………………………………..…41

    List of Figures Table Page

    1. The six most common in abundance and five most contributing to

    biomass fish species found on the inner reef flat surveys of

    Hanauma Bay in 1991 (Stender and Russel, 1991)…………………………………….7

    2. Resources fish density from a metadata analysis performed by

    Friedlander et al.

    (2018)………………………………………………………………………………….……..8

    3. Eleven Sectors of Hanauma Bay used to separate visual human

    counts and activity…………………………………………………………………………12

    4. Comparison between visual human counts and human counts derived from

    photographs, time of day, and human activity (beach, wade, swim)…………….…..13

    5. Experimental design within sectors of Hanauma Bay……………………………..….14

    6. Coral skeletons were secured within transects for trampling study……………...….15

    7. Calculation of percent loss of coral skeleton during trampling studies…………...…16

    8. Comparison of percent skeletal loss per day in each transect of

    the Hanauma Bay Nature Preserve………………………………………………….….18

    9. Average percent skeletal loss per day regressed against the average

    percent of swimmers and waders of each transect within Hanauma

    Bay over the June coral trampling study…………………………………………….….20

    10. Average percent skeletal loss per day regressed against the average

    percent of swimmers and waders of each transect within Hanauma

    Bay over the October coral trampling study. ………………………………………...…21

    11. Average percent skeletal loss per day during the June 2019 study of

    coral skeletons place along a transect in each sector paired with the

    proportion of swimmers and waders typically present in that sector…………………22

  • IV

    List of Figures cont. Table Page

    12. Average percent skeletal loss per day during the October 2019 study

    of coral skeletons place along a transect in each sector paired with

    the proportion of swimmers and waders typically present in that sector……………22

    13. Secchi disk measurement conducted along a transect………………………………..23

    14. A comparison of visual horizontal secchi disk measurements …………………..….24

    15. Sediment accumulation (g/day) during the month of June as it relates

    to the proportion of swimmer and waders typically present in each sector……….…28

    16. June (grey) and October (black) sediment accumulation (g) per day

    regressed with proportion of visitors in present in each sector of Hanauma Bay…..29

    17. Sediment accumulation (g/day) during the month of October as it relates

    to the proportion of swimmer and waders typically present in each sector……….…30

    18. Average sediment accumulation per day per transect averaged between

    a shore-most positioned sediment trap and an ocean-most positioned

    sediment trap along the 15 m transect…………………………………………………..31

    19. Coral composition at e