Michael Childress Department of Biological Sciences Clemson University

Michael Childress Department of Biological Sciences Clemson University

Why are blue crabs declining? How does drought impact blue crabs? How do you model blue crabs? How will climate change affect crabs? What is the forecast for blue crabs?

1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 21 23 25 27 29 211 213 Landings (millions lbs) 8 7 6 5 4 3 2 1 Year SCDNR Data

1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 21 23 25 27 29 211 213 Landings (millions lbs) Licenses (commercial) 8 7 6 5 4 3 2 1 Commercial Licenses 5 45 4 35 3 25 2 15 1 5 Year r 2 =.27, p =.59 SCDNR Data

1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 21 23 25 27 29 211 213 Landings (millions lbs) Log flow (cu ft/ s) 8 7 6 5 4 3 2 1 Edisto River Discharge year lag 4 3.8 3.6 3.4 3.2 3 2.8 2.6 Year r 2 =.113, p =.483 Childress 21 SCWRC

1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 21 23 25 27 29 211 213 Landings (millions lbs) Log flow (cu ft/ s) 8 7 6 5 4 3 2 1 Edisto River Discharge 1 year lag 4 3.8 3.6 3.4 3.2 3 2.8 2.6 Year r 2 =.161, p =.168 Childress & Parmenter 212 SCWRC

1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 21 23 25 27 29 211 213 Landings (millions lbs) Log flow (cu ft/ s) 8 7 6 5 4 3 2 1 Edisto River Discharge 2 year lag 4 3.8 3.6 3.4 3.2 3 2.8 2.6 Year r 2 =.29, p =.56 Childress 214 SCWRC

Why are blue crabs declining? How does drought impact blue crabs? How do you model blue crabs? How will climate change affect crabs? What is the forecast for blue crabs?

Freshwater Saltwater Mating March-May Egg incubation April-June Larval release June-Aug Juveniles Sept-March (19 mo) Megalopae Aug-Oct Zoeae July-Sept SCDNR Photos

Salinity Normal Conditions Drought Conditions

Combahee Ashepoo Edisto ACE Basin NERR

Salinity 1 5 1 15 2 25 3 35 ACE Basin NERR

Fishery Boundary ACE Basin NERR

Disease Prevalence (%) Juvenile Eaten (%) Median Salinity (psu) Crab Number 4 35 Salinity 45 4 Crab Abundance 3 25 2 15 1 5 Ashepoo Combahee Edisto 35 3 25 2 15 1 5 Ashepoo Combahee Edisto 1 2 3 4 5 6 7 8 9 Station 1 2 3 4 5 6 7 8 9 Station 2% 18% 16% 14% 12% Disease 8% 7% 6% 5% Predation 1% Ashepoo 4% Ashepoo 8% 6% 4% 2% Combahee Edisto 3% 2% 1% Combahee Edisto % 1 2 3 4 5 6 7 8 9 Station % 1 2 3 4 5 6 7 8 9 Station Crabs: r 2 =.8, p =.5298 Crabs: r 2 =.4, p =.5389 Salinity: r 2 =.277, p =.786 Salinity: r 2 =.743, p =.3 Childress & Parmenter 212 SCWRC

Crab Abundance Predation Disease Salinity Inflow Parmenter et al. 213 Estuaries & Coasts

Crab Number 25 Crab Forecast 2 15 1 5 Ashepoo Combahee Edisto Observed ARIMA Forecast J S DM J S DM J S DM J S DM J S DM J S DM J S DM Month (quarterly) Childress & Parmenter 212 SCWRC

Why are blue crabs declining? How does drought impact blue crabs? How do you model blue crabs? How will climate change affect crabs? What is the forecast for blue crabs?

Childress 21 SCWRC

Spatially-Explicit IBM Crab Model Individual-Based Subroutines Season (time) Settlement (season) (location) Dispersal (season) (sex) (stage) Inflow Salinity Temperature Oxygen Time (week) Stage (age) Survival (fishing) (salinity) (temperature) (dis oxygen) (predation) (disease) (cannibalism) Location (space) Growth (temperature) (stage) (age) Reproduction (season) (sex) (stage)

IBM Crab Model Spatial Structure Combahee Ashepoo Edisto Juvenile stage = J3 age = 2 disease = no reprod = no heading = 35 Male stage = M13 age = 15 disease = yes reprod = no heading = 355 Female stage = F18 age = 245 disease = no reprod = yes heading = 185

Landings (millions lbs) Trapped crab number Landings (millions lbs) 35 7 Model forecasts steep decline during 99-2 drought Model landings predict 32% of observed landing variation Thus, the IBM is even better at predicting crab abundance 3 6 25 5 2 4 15 3 1 2 Model 5 Landings 1 7 6 5 4 3 2 1 r 2 =.32, p =.439 1 15 2 25 3 35 Trapped crab number (model)

Why are blue crabs declining? How does drought impact blue crabs? How do you model blue crabs? How will climate change affect crabs? What is the forecast for blue crabs?

IPCC 214

Precipitation Evaporation P-E Seager et al. 29 J Climate Seager et al. 212 J Climate

NOAA NWS Climate Prediction Center

Flow (log cfs) 3.9 3.7 3.5 3.3 3.1 2.9 y = -.27x + 8.5963 Observed ARIMA Model 2.7 y = -.56x + 14.44 2.5 194 196 198 2 22 24 26 Year USGS 2175 Edisto River near Givhans Ferry, SC

Flow (log cfs) 3.9 3.7 3.5 Observed Slight Moderate Severe 3.3 3.1 2.9 2.7 2.5 194 196 198 2 22 24 26 28 Year Childress 214 SCWRC

Projected Crab Landings (millions lbs) Projected Crab Landings (millions lbs) Flow (log cfs) Flow (log cfs) 3.9 3.9 3.7 Observed 3.7 Observed 3.5 Slight 3.5 Moderate 3.3 3.1 2.9 2.7 Slope =.2 Amplitude =.2 2.5 194 196 198 2 22 24 26 28 9 8 Slight Freshwater Decrease 7 6 5 4 3 2 1 194 196 198 2 22 24 26 28 Year 3.3 3.1 2.9 2.7 Slope =.3 Amplitude =.3 2.5 194 196 198 2 22 24 26 28 9 8 Moderate Freshwater Decrease 7 6 5 4 3 2 1 194 196 198 2 22 24 26 28 Year Childress 214 SCWRC

Projected Crab Landings (millions lbs) Projected Crab Landings (millions lbs) Flow (log cfs) Flow (log cfs) 3.9 3.9 3.7 Observed 3.7 Observed 3.5 Severe 3.5 Extreme 3.3 3.1 2.9 2.7 Slope =.4 Amplitude =.4 2.5 194 196 198 2 22 24 26 28 9 8 Severe Freshwater Decrease 7 6 5 4 3 2 1 194 196 198 2 22 24 26 28 Year 3.3 3.1 2.9 2.7 Slope =.5 Amplitude =.5 2.5 194 196 198 2 22 24 26 28 9 Extreme Freshwater Decrease 8 7 6 5 4 3 2 1 194 196 198 2 22 24 26 28 Year Childress 214 SCWRC

Year Source DF F P r2 215 Full 24 9.895.1.7425 Amplitude 4 49.64.1.6512 Slope 4 6.323.3.811 A X S 16.851.6248.11 29 Full 24 14.54.1.8145 Amplitude 4 34.85.1.355 Slope 4 44.7.1.453 A X S 16 2.8.246.28 Childress 214 SCWRC

Frequency (%) 16 14 34% 12 1 8 6 32% 34% 4 2 1 2 3 4 5 6 7 8 1979-213 Observed Blue Crab Landings (million lbs) Childress 214 SCWRC

Probability (%) Probability (%) Probability (%) Probability (%) 16 14 12 1 8 6 4 2 Slight Freshwater Decrease 38% 36% 26% 18 16 14 12 1 8 6 4 2 Moderate Freshwater Decrease 89% 1% 1% 1 2 3 4 5 6 7 29 Projected Blue Crab Landings (millions lbs) 8 1 2 3 4 5 6 7 29 Projected Blue Crabs Landings (million lbs) 8 25 2 15 1 Severe Freshwater Decrease 28% 1% 71% 6 5 4 3 2 Extreme Freshwater Decrease 56% 43% 5 1 1% 1 2 3 4 5 6 7 29 Projected Blue Crab Landings (millions lbs) 8 1 2 3 4 5 6 7 8 29 Projected Blue Crab Landings (millions lbs) Childress 214 SCWRC

Why are blue crabs declining? How does drought impact blue crabs? How do you model blue crabs? How will climate change affect crabs? What is the forecast for blue crabs?

1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 21 23 25 27 29 211 213 Landings (millions lbs) Log flow (cu ft/ s) 8 7 6 5 4 3 2 1 Edisto River Discharge 2 year lag 4 3.8 3.6 3.4 3.2 3 2.8 2.6 Year r 2 =.29, p =.56 Childress 214 SCWRC

1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 21 23 25 27 29 211 213 Landings (millions lbs) Log flow (cu ft/ s) 8 7 6 5 4 3 2 1 Edisto River Discharge 5 year MA 4 3.8 3.6 3.4 3.2 3 2.8 2.6 Year r 2 =.469, p <.1 Childress 214 SCWRC

1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 21 23 25 27 29 211 213 215 217 219 221 223 225 227 229 231 233 235 Crab landings (millions lbs) 8 7 6 5 4 3 2 1 Observed F2 Model MA5 Model 215 = 5.83 215 = 4.59 Year Childress 214 SCWRC

1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 21 23 25 27 29 211 213 215 217 219 221 223 225 227 229 231 233 235 Crab landings (millions lbs) 8 7 6 5 4 3 2 1 Observed Slight Moderate Severe Year Childress 214 SCWRC

Model 215 235 29 FA2 Model 5.836 (+14%)???? MA5 Model 4.591 (-1%)???? SCBCRABs slight 5.465 (+7%) 5.47 (+8%) 6.44 (+26) SCBCRABS moderate 4.126 (-19%) 4.272 (-16%) 4.294 (-16%) SCBCRABS severe 3.294 (-35%) 2.724 (-47%).887 (-83%) 213 SC blue crab landings = 5.98 Childress 214 SCWRC

Sanchez-Rubio et al. 211 Fisheries Bulletin Why are blue crabs declining? Decreasing freshwater input to estuary Wilber 1994 Fisheries Bulletin

How does drought impact blue crabs? Droughts increase disease and high salinity stress Parmenter et al. 213 Estuaries Lee & Frischer 24 American Scientist

How do you model blue crabs? IBMs allow for integration of multiple effects Childress 21 SCWRC

How will climate change affect crabs? Droughts will become more severe Colton Seager et al. et 213 al. 212 Fisheries Journal & Oceanography of Climate

Landings (millions lbs) What is the forecast for blue crabs? Landings will continue to decrease if rate of freshwater decline continues at the present level 9 8 7 6 5 4 3 2 1 SC Blue Crab Landings Year SCDNR Data

Funding NOAA-UCAR Subaward Z14-1556 SC Sea Grant R/CF-1 & R/CF-15 NERR Graduate Research Fellowship Clemson Research Incentive Fund Collaboration Clemson M Ptacek SC Seagrant J Davis, E Fly ACE Basin NERR A Segars, J Leffler SC DNR D Whittaker, L DeLancey, A Fowler CISA K Dow, D Tufford Field assistants K Parmenter K Smith Conservation of Marine Resources Team