Independent Data Paramount in Making Management Decisions
Early morning sample: Technicians Tyler Averett, left, and Mitchell Blake sort the catch from a gill net set overnight.
By Kelly Odom
Fish Eye News
N.C. Division of Marine Fisheries
On a cold winter’s morning, before dawn, two Division of Marine Fisheries technicians leave the dock headed for the Belhaven breakwall.
They reach their destination, where they had set nets the night before, and begin to pull the nets onto the boat, sorting the catch and recording every detail about the fish species, weight, length and the water it was caught in — salinity, temperature, etc.
“All that information goes into a database so that biologists can see trends … see the patterns of fish movement, fish sizes and fish species,” said Mitchell Blake, a former division technician.
He and another technician, Tyler Averett, collected the information a year ago for the Pamlico Sound Independent Gill Net Survey, one of several independent sampling programs that provide needed information to biologists working on fishery management plans, as well as stock assessments. And the information collected then is still being used today.
“We look at the time series of data for stock assessments, so the data Blake and Averett collected last winter is still vital information,” said Laura Lee, division senior stock assessment scientist.
Independent sampling is information collected by biologists that does not involve the commercial or recreational harvest of fish.
Dependent data, such as commercial landings or recreational port sampling, may not show everything because the fisherman is using gear designed to target for a particular species or size limit, and they fish in areas where they are most likely to catch fish.
In the Pamlico Sound Independent Gill Net Survey biologists use computer-generated random sampling sites and several different gill net mesh sizes so that they catch whatever is there.
“We see every species, and get samples of every size because our mesh size goes from 3 inches to 6 ½ inches in shallow and deep water, using horizontal and vertical grids, so pretty much if it is there we are getting a sample of it,” Blake said.
Every species in the net is weighed, counted, sized and checked for disease. All that information is documented.
The Pamlico Sound Independent Gill Net Survey also records water quality, bottom structures, development, grasses, water temperatures, salinity and oxygen, and every species in the water column from top to bottom in that grid.
“Some of the other things we look at are determining what kind of marsh it is, whether it is low sediment bank, high sediment bank, if it is beach ford, or swamp forest,” Blake said. “We have even started adding what type of construction is in the area — docks, marinas, basins, slope structure, etc.”
Every year, biologists collect more information, which allows managers to get a better picture of what causes certain trends, Blake said.
“Due to the longevity of the program, biologists can see the highs and the lows and they can create a real good forecast of what is going on,” he said.
This lends to more effective management. There are numerous processes that influence fishery populations, and the more biologists understand them, the better decisions they can make.