Part A: Overfishing in Georges Bank
Georges Bank is an underwater bank situated along the eastern edge of the Gulf of Maine between Cape Cod and Nova Scotia. This region is one of the most biologically productive marine areas on the eastern seaboard, historically accounting for a large percentage of New England's commercial fish landings. The Georges Bank fishery is particularly well-known for its groundfishspecies such as cod, haddock, and flounder that feed near the bottom of the ocean.
- Look at the graph below of trends in Georges Bank haddock catch and mortality from 1969 through 2004.
- The histogram shows the annual haddock landingthe amount of fish that are caught and kept to sell.
- The red line shows the fishing mortality rate, Fthe rate at which fish are removed from a population due to fishing (as opposed to removals due to natural causes such as disease or predation). F can also be thought of as the percentage of a population that die in one year due to fishing.
Graph courtesy of NOAA.
Stop and Think
1: Describe the trends you see in the Haddock landings from 1969-2004. Are there steady trends or distinct turning points?
2: Calculate the difference between the greatest and least landing values. What percentage of the maximum yield was the minimum yield? In what years did these extremes occur?
3: Look carefully at the years 1985-2000. What does it mean for the fishing mortality to be consistently "high" while landings were consistently "low"?
Overfishing is the consequence of removing fish from the oceans faster than they can replenish themselves. This occurs when fishing mortality exceeds the Maximum Fishing Mortality Threshold (MFMT, or FTHRESHOLD). This value is normally equivalent to FMSY, where MSY (maximum sustainable yield) is the maximum catch the stock can sustain without impairing its ability to replenish itself through reproduction. Therefore, MSY is a measure of how many fish can be taken from the sea without causing the stock to become depleted.
Answer the following questions to check your understanding of the information provided in the Georges Bank Haddock Trends in Catch and Fishing Mortality graph above.
- According to stock assessments by the Northeast Fisheries Science Center, the value of FMSY for Georges Bank haddock is 0.26. During which years was Georges Bank haddock subject to overfishing?
Overfishing occurs when F > 0.26, so overfishing occurred from 1969-1973 and 1979-1994,
- Was Georges Bank haddock subject to overfishing as of 2004?
No, F2004 = 0.24, which is less than FMSY of 0.26.