ChesMMAP Field Methods

Vessel

ChesMMAP fishes from the R/V Bay Eagle, a 65' aluminum hull, twin diesel-engine vessel capable of housing crew and scientists for multi-day deployments.  The vessel is fully equipped with navigational electronics, dry lab, wet lab, galley, mess and sleeping quarters.  We have rigged the vessel to be an efficient trawler by constructing and installing a removable modular platform, trawling winch, A-frame, and net reel (view pictures below).

Gear

Our net is a 45-foot 4-seam balloon otter trawl with 6-inch stretch mesh in the  wings and body,  and 3-inch stretch mesh in the cod end, with no liner.  The doors are four-foot steel V doors weighing 185lbs. each, with a 'tickler chain' attached between them.

Sensors

We use three Netmind sensors - one on each wing and one on the headrope. This allows us to measure the net width and height in real time to assure the net is fishing properly.

Stations 

ChesMMAP has five cruises a year, occurring in the months of March, May, July, September and November.  Each cruise samples 80 stations ranging from just outside the Chesapeake Bay Bridge Tunnel north to Poole's Island (near Baltimore, MD).

We divide the bay in to 5 regions  and stations are selected prior to each cruise.  Stations are selected according to a random stratified design, incorporating both latitudinal and depth strata.

At each station the net is trawled along the bottom for 20 minutes, with the current, at a speed of 3.0-3.3 knots. 

Each cruise takes approximately 8 working days to complete.

Data Collected

The catch at each station is first sorted by species.  For the majority of the species - a group weight (per species) is taken along with individual lengths.  A sub sample of each species (~3-10 individuals) is removed from the catch and taken for further sampling.

Pictured Above: Four Size Classes of Weakfish 

All data is recorded electronically using Scantrol Fish Measuring Boards.  Data is also taken on habitat and invertebrate species caught in the net.