INTERSTATE FISHERIES MANAGEMENT PROGRAM IMPLEMENTATION FOR NORTH CAROLINA By A. Blake Price and Jeff Gearhart Completion Report for Cooperative Agreement No. NA 87FG0367 /3 Study II DOCUMENTATION AND REDUCTION OF BYCATCH IN NORTH CAROLINA FISHERIES JOB 4: Large Mesh (> 5-inch) Gillnet Discard Mortality of Spotted Seatrout (Cynoscion nebulosus), Weakfish (Cynoscion regalis), Southern Flounder (Paralichthys lethostigma), and Red Drum (Sciaenops ocellata) in Roanoke Sound, Core Sound, and the Neuse River, North Carolina August 2002 ABSTRACT A large mesh (> 5.0 in stretched mesh) gillnet discard mortality study was conducted in Pamlico Sound, Pungo River, and Hatteras Island at high and low salinity sites to determine delayed mortality estimates of red drum (Sciaenops ocellata) and striped bass (Morone saxatilis). Large mesh gillnets were soaked for approximately 12 hours. Upon retrieval, live fish were transferred to net pens located near the capture site and held for 72 hours. Mortalities and water quality data (temperature, dissolved oxygen, and salinity) were collected at 24 hr intervals. Delayed mortality estimates were 33% for red drum and 8% for striped bass. Logistic regression analysis was employed to model the effects of area (Outer Banks or River sites), mesh size, trial, fish length, dissolved oxygen, temperature, and salinity on mortality for each species. Temperature was related to mortality for both species. Salinity and mesh size were also related to red drum mortality. The results offer insights for fishery managers developing Fishery Management Plans (FMPs) and may assist in bycatch mortality estimates for each of these species. Recommendations include expansion of the study to fishery-dependent gillnet fisheries, establish more consistent observer coverage, implement control groups to measure the confounding effects of handling, transport and confinement stress in future delayed mortality studies. 4-ii TABLE OF CONTENTS ABSTRACT ......................................................................................................................................... 4-ii TABLE OF CONTENTS .................................................................................................................... 4-iii LIST OF TABLES ............................................................................................................................... 4-iv LIST OF FIGURES ............................................................................................................................... 4-v INTRODUCTION ................................................................................................................................. 4-6 METHODS ............................................................................................................................................ 4-7 PROJECT LIMITATIONS ................................................................................................................... 4-9 RESULTS .............................................................................................................................................. 4-9 Catches .............................................................................................................................................. 4-9 Total Mortality .................................................................................................................................. 4-9 At Net Mortality .............................................................................................................................. 4-10 Delayed Mortality ........................................................................................................................... 4-10 Day of Death ................................................................................................................................... 4-12 Water quality ................................................................................................................................... 4-13 Statistical analyses........................................................................................................................... 4-13 DISCUSSION ...................................................................................................................................... 4-16 CONCLUSION ................................................................................................................................... 4-17 Striped Bass ..................................................................................................................................... 4-17 Red Drum ........................................................................................................................................ 4-17 RECOMMENDATIONS .................................................................................................................... 4-18 ACKNOWLEDGMENTS ................................................................................................................... 4-19 LITERATURE CITED ........................................................................................................................ 4-20 4-iii LIST OF TABLES Table 1. Number of striped bass and red drum caught by month in the large mesh (5.0, 5.5, 6.0, 6.5 in stretched mesh) gillnet discard mortality study conducted at sites located in Pamlico Sound and Roanoke Sound, NC during the 2001 fishing season. ............................. 4-9 Table 2. Length frequency distributions of striped bass captured in the large mesh (5.0, 5.5, 6.0, 6.5 in stretched mesh) gillnet discard mortality study conducted in Pamlico Sound and Roanoke Sound, NC during the 2001 fishing season. ........................................................... 4-10 Table 3. Length frequency distributions of red drum captured in the large mesh (5.0, 5.5, 6.0, 6.5 in stretched mesh) gillnet discard mortality study conducted in Pamlico Sound and Roanoke Sound, NC during the 2001 fishing season. ........................................................... 4-11 Table 4. Percent mortality (at net delayed) of striped bass and red drum caught by mesh size in the large mesh (5.0, 5.5, 6.0, 6.5 in stretched mesh) gillnet discard mortality study conducted in Pamlico Sound, and Roanoke Sound, NC during the 2001 fishing season. ............................................................................................................................................... 4-11 Table 5. Total mortality, at net mortality (upon capture), and delayed mortality of striped bass and red drum caught in the large mesh (5.0, 5.5, 6.0, 6.5 in stretched mesh) gillnet discard mortality study conducted in Pamlico Sound and Roanoke Sound, NC during the 2001 fishing season. ......................................................................................................... 4-12 Table 6. At net mortality by month (Apr – Aug) of striped bass and red drum caught in the large mesh (5.0, 5.5, 6.0, 6.5 in stretched mesh) gillnet discard mortality study conducted in Pamlico Sound and Roanoke Sound, NC during the 2001 fishing season. ........................... 4-12 Table 7. Delayed mortality of striped bass and red drum caught in the large mesh (5.0, 5.5, 6.0, 6.5 in stretched mesh) gillnet discard mortality study conducted in Pamlico Sound and Roanoke Sound, NC during the 2001 fishing season. ........................................................... 4-12 Table 8. Water quality data collected during the large mesh (5.0, 5.5, 6.0, 6.5 in stretched mesh) gillnet discard mortality study conducted in Pamlico Sound and Roanoke Sound, NC during the 2001 fishing season. Data include mean water temperature (C), mean dissolved oxygen content (mg/L), and mean salinity (ppt) for the Outer banks and river sites by month. .............................................................................................................. 4-14 Table 9. Summary of stepwise logistic regression analyses of independent variables on 72-h discard mortality of striped bass caught in large mesh gillnets (5.0, 5.5, 6.0, 6.5 in. stretch mesh) in Pamlico Sound and Roanoke Sound, NC during the 2001 fishing season. .................................................................................................................................... 4-15 Table 10. Summary of stepwise logistic regression analyses of independent variables on 72-h discard mortality of red drum in large mesh gillnets (5.0, 5.5, 6.0, 6.5 in. stretch mesh) in Pamlico Sound and Roanoke Sound, NC during the 2001 fishing season. ....................... 4-15 4-iv LIST OF FIGURES Figure 1. Sample sites for the large mesh (5.0, 5.5, 6.0, 6.5 in stretched mesh) gillnet discard mortality study conducted in Pamlico River and Pungo River (Map A), and Roanoke Sound (Map B), NC in the 2001 fishing season. ..................................................................... 4-8 Figure 2. Day of death for striped bass and red drum caught in the large mesh (5.0, 5.5, 6.0, 6.5 in stretched mesh) gillnet discard mortality study conducted in Pamlico Sound and Roanoke Sound, NC during the 2001 fishing season. ........................................................... 4-13 4-v INTRODUCTION Large mesh gillnets (> 5.0 in stretched mesh) are common finfish gear used throughout the inshore waters of North Carolina. These nets are typically utilized in the flounder (Paralichthys spp.) fishery. There are many bycatch and discard mortality issues surrounding large mesh gillnet fisheries.