Investigation of the Relative Habitat Value of Oil/Gas Platforms and Natural Banks in Enhancing Stock Building of Reef Fish in the Western Gulf of Mexico
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Investigation of the relative habitat value of oil/gas platforms and natural banks in enhancing stock building of reef fish in the western Gulf of Mexico Gregory W. Stunz, Matthew J. Ajemian, Matthew K. Streich, Rachel Brewton, Charles Downey, and Quentin Hall SEDAR52-RD-02 July 2017 INVESTIGATION OF THE RELATIVE HABITAT VALUE OF OIL/GAS PLATFORMS AND NATURAL BANKS IN ENHANCING STOCK BUILDING OF REEF FISH IN THE WESTERN GULF OF MEXICO GRANT NA14NMF4330219 FINAL REPORT Submitted To: National Marine Fisheries Service Southeast Regional Office State/Federal Liaison Office 9721 Executive Center Drive North St. Petersburg, Florida 33702 Submitted By: Gregory W. Stunz, Ph.D. Matthew J. Ajemian, Ph.D. Matthew K. Streich Rachel Brewton Charles Downey Quentin Hall Harte Research Institute for Gulf of Mexico Studies Texas A&M University-Corpus Christi 6300 Ocean Drive Corpus Christi, TX 78412 November 2016 2 Stunz and Ajemian Final Report to MARFIN November 2016 ACKNOWLEDGEMENTS We are appreciative of the National Marine Fisheries Service (NMFS), Marine Fisheries Initiative for funding this study (GRANT #NA14NMF4330219). Special thanks to Bob Sadler with NFMS for helping us with business administration and facilitating other programmatic matters for the grant as well as Gregg Gitschlag for the technical monitoring and advice. We would like to thank the many people that contributed to the execution of this study and made it a success, including members of the Fisheries and Ocean Health Lab at the Harte Research Institute: M. Robillard, J. Wetz, J. Williams, T. Topping, Q. Hall, A. Tompkins, K. Gibson, A. Ferguson, D. Norris, and M. Hargis for logistical support during field trials. 3 Stunz and Ajemian Final Report to MARFIN November 2016 TABLE OF CONTENTS ACKNOWLEDGEMENTS ............................................................................................................ 2 LIST OF FIGURES ........................................................................................................................ 4 LIST OF TABLES .......................................................................................................................... 5 II. ABSTRACT ............................................................................................................................... 6 III. EXECUTIVE SUMMARY ...................................................................................................... 7 IV. PURPOSE ................................................................................................................................. 9 A. Description of the problem............................................................................................... 9 B. Objectives of the project ................................................................................................ 12 V. APPROACH ............................................................................................................................ 13 A. Description of the work performed ................................................................................ 13 Fish Community Comparison - (Obj. 1) ............................................................................... 13 Red Snapper Size Structure, Age, and Growth - (Obj. 2) ..................................................... 20 Red Snapper Fecundity - (Obj. 2) ......................................................................................... 26 Red Snapper Trophic Ecology - (Obj. 3) .............................................................................. 31 B. Project management ....................................................................................................... 34 VI. FINDINGS .............................................................................................................................. 35 A. Actual accomplishments and findings ........................................................................... 35 Fish Community Comparison - (Obj. 1) ............................................................................... 35 Red Snapper Size Structure, Age, and Growth - (Obj. 2) ..................................................... 49 Red Snapper Fecundity - (Obj. 2) ......................................................................................... 61 Red Snapper Trophic Ecology - (Obj. 3) .............................................................................. 70 Overall Summary .................................................................................................................. 85 B. Significant problems ...................................................................................................... 88 C. Need for additional work ............................................................................................... 88 VII. EVALUATION ..................................................................................................................... 89 A. Attainment of project goals and objectives .................................................................... 89 B. Dissemination of project results ..................................................................................... 89 VIII. REFERENCES .................................................................................................................... 90 4 Stunz and Ajemian Final Report to MARFIN November 2016 LIST OF FIGURES Figure 1. Rigs to Reefs Options .................................................................................................... 11 Figure 2. Map of artificial reefs (red stars) and natural banks (green circles) surveyed .............. 15 Figure 3. Map of the study area depicting locations ..................................................................... 22 Figure 4. The study area was comprised of nine sites .................................................................. 28 Figure 5. Non-metric multidimensional scaling (nMDS) ............................................................. 39 Figure 6. Shade plot of square-root transformed species counts .................................................. 41 Figure 7. Red Snapper (RS) density estimates (# of individuals/m2) from ROV transects. ........ 42 Figure 8. Estimated total abundance of Red Snapper ................................................................... 42 Figure 9. Length (A) and weight (B) frequencies of Red Snapper captured ................................ 51 Figure 10. Histograms displaying age (A) and cohort (B) frequencies of Red Snapper. ............. 52 Figure 11. Logistic growth models of Red Snapper TL-at-age (A) and TW-at-age (B) data ....... 55 Figure 12. Male:Female ratio of Red Snapper .............................................................................. 61 Figure 13. The condition index, relative weight (Wr), for Red Snapper ...................................... 62 Figure 14. Mean gonadosomatic index (GSI) of male and female Red Snapper ......................... 63 Figure 15. Mean GSI per month and habitat of female Red Snapper ........................................... 64 Figure 16. The percent Frequency of Occurrence of spawning capable female Red Snapper ..... 64 Figure 17. A multidimensional scaling (MDS) ordination of oocyte stage distribution .............. 66 Figure 18. Batch fecundity (A) and annual fecundity (B) by age and habitat .............................. 67 Figure 19. Histogram of Red Snapper used in a.) diet and b.) stable isotope analysis ................. 71 Figure 20. Cumulative prey curves plotting mean (±SE) of unique prey items. .......................... 72 Figure 21. Percent by weight of Red Snapper diet collected by size class ................................... 77 Figure 22. Feeding strategy diagrams of Red Snapper collected.................................................. 78 Figure 23. Scatterplot and linear regression of Red Snapper δ 15N (a) and δ 13C (b) values ........ 79 Figure 24. Scatterplot of Red Snapper carbon (δ13C) and nitrogen (δ15N) values ........................ 80 Figure 25. Scatterplot and linear regression of stable nitrogen (δ15N) and carbon (δ13C) ............ 81 Figure 26. Stable nitrogen (δ15N) and carbon (δ13C) ratios. ......................................................... 82 Figure 27. Carbon (δ13C) and nitrogen (δ15N) isotope values ± SE of Red Snapper .................... 83 5 Stunz and Ajemian Final Report to MARFIN November 2016 LIST OF TABLES Table 1. Physical characteristics of natural banks and artificial reefs surveyed ........................... 16 Table 2. Record of various taxa observed during ROV surveys................................................... 36 Table 3. Relative abundance (i.e., MinCounts) of five federally managed species ...................... 38 Table 4. Species most contributing to between-habitat dissimilarity ........................................... 39 Table 5. Growth models fit to length-at-age data for Red Snapper collected ............................... 53 Table 6. Growth models fit to weight-at-age data for Red Snapper collected .............................. 54 Table 7. Results of likelihood ratio tests comparing logistic growth model ................................ 56 Table 8. Overview of female reproductive characteristics from Red Snapper ............................. 66 Table 9. Diet of Red Snapper. ....................................................................................................... 73 Table 10. Results from a two way crossed PERMANOVA on diet composition .......................