SCBCRABS Blue Crab Forecast Model

SCBCRABS Blue Crab Forecast Model
Opinions expressed in this blog are solely those of the author and do not necessarily reflect the opinions of the collaborative scientists or funding agencies that supported this research.

Friday, June 5, 2015

SC Blue Crab Forecast Presentation

Here is a presentation that explains the recent SC blue crab forecast and how it was constructed.  The video is approximate 45 minutes long.

Click here to view this video.

Wednesday, June 3, 2015

Blue Crab Landings Long Range Forecast

The forecast for next year is a slight decrease in landings followed by eight years of modest increase in landings. This line graph show the forecasted blue crab landings for South Carolina based on 100 runs of the SCBCRABS forecast model.  The output is in millions of lbs. blue crabs landed versus year.  The line represents the average of all runs of the model and the thin error bar represents one standard deviation or the range where 67% of the model landings were located.  The black diamonds represent the actual reported commercial landings for the state of South Carolina by year.  The colors on the graph represent the level of freshwater input to the coast as measured by annual discharge of the Edisto River.  When annual average flows exceed 1250 cubit feet / second it is sufficiently high to support crab population growth but when if falls below 1250 cubit feet / second, like during a severe drought, crab population decreases.  Green regions are years where three of the three prior years were above this critical minimum flow.  Yellow regions are years where two of the three prior years were above minimum flow. Orange regions are years where one of the three prior years were above minimum flow and red regions are years where none of the three prior years were above minimum flow.  These effects are felt for five years and are cumulative so it takes a long time to go from red flow conditions back to green.  You will note that the SCBCRABS model forecast tends to increase in green years, remain the same in yellow years, decreases in orange years and decrease severely in red years.

Forecast Landings for 2015

The 2015 blue crab landings for South Carolina are forecasted to be 3.69 million lbs.  This is down from the previous' years landings of 3.84 millions lbs. and represents a decrease of 2.8%.  The confidence range this prediction is from 2.11 to 5.28 million lbs.  Individual annual landings may increase as much as 38.9% or may decrease as much as 44.4%.