Ecological Forecasting Techniques Used In Anticipating Lower 2003 North Carolina Pink Shrimp Harvests
North Carolina’s 2003 harvest of pink shrimp could be significantly lower than the previous year’s harvest of 840,000 pounds as a result of abnormally cooler water temperatures in estuarine nursery grounds during the winter period when juvenile pink shrimp are most vulnerable, according to a new forecasting capability used by federal marine scientists.
This ecological forecast from NOAA’s National Centers for Coastal Ocean Science reflects a new public service aimed at predicting impacts of chemical, biological, and physical ecosystems changes in the nation’s coastal areas. NCCOS expects such ecological forecasts will become an increasingly frequent aspect of its work on coastal science issues and their impacts on mainstream society concerns and interests.
The North Carolina pink shrimp forecast for this year is based on a two-week low temperature of 4.68 degrees Celsius (40.4 degrees Fahrenheit) during the important time that juvenile pink shrimp are in key North Carolina estuarine nursery grounds. Those low temperatures may be related to increased shrimp mortality as a result of the shrimps’ inability to adapt to changing salinities when water temperatures are unusually cool. The waters this year were cooler than the two-week lows of 41.9 degrees F in 2000 or 2001, when total North Carolina harvests for the February-July period were 110,000 and 203,000 pounds (heads on) respectively. The 840,000-pound pink shrimp harvest in North Carolina for the same period in 2002 was valued at more than $1.8 million.
The 2003 two-week temperature low is the fourth lowest since NCCOS’s laboratory in Beaufort, N.C., began its temperature monitoring efforts in 1962. Pink shrimp in North Carolina are at the northern limits of their temperature tolerance and are therefore particularly sensitive to temperature variations.
North Carolina’s pink shrimp harvest varies from year to year, with estuary temperature the key factor in declines and increases. The number of pink shrimp available for harvest over the first seven months of the year is strongly influenced by environmental conditions in estuaries where post-larval shrimp develop over winter months as juveniles. (North Carolina’s larger harvests of brown shrimp are not taken at the same time of year.)
In addition to pink shrimp (Farfantepenaeus duorarum), an important fisheries resource in North Carolina and in the South Atlantic and Gulf Coast states, other living marine species in North Carolina also have over-wintering juvenile stages sensitive to low estuary temperatures. The NCCOS ecological monitoring techniques are expected to be valuable also in anticipating more general indicators of estuarine conditions for other species – such as seatrout and red drum – similarly sensitive to low temperatures.