NOAA Teacher at Sea
Aboard R/V Savannah
July 7 – July 18, 2012
Mission: SEFIS Reef Fish Survey
Location: Atlantic Ocean, off the coast of St. Augustine, Florida
Date: July 11, 2012
Latitude: 29 ° 55.96’ N
Longitude: 80 ° 31.29’ W
Air Temperature: 27.6°C (81.7°F)
Wind Speed: 5 knots
Wind Direction: from S
Surface Water Temperature: 28.12 °C (82.6°F)
Weather conditions: Fair
Science and Technology Log
Catching bottom fish at the reef
Pulling in a successful catch of reef fish provides scientists with an important sampling source of fish numbers and species diversity.
The process requires a systematic and complex capture protocol. As with any well-designed science investigation, the equipment needs to be robust and the sequence of steps in the process of fish takings must be followed with consistency. The methods and materials are kept as similar as possible in multiple sites over a wide area.
The area to be sampled is mapped out in advance with electronic navigation tools.
This habitat is where the targeted fish species – red and vermillion snapper, gray triggerfish, black sea bass, red porgy, scamp, squirrelfish, almaco jack and amberjack, among others – are most likely found.
Chevron fish traps are used to trap fish for scientific study. Fish trapping using these devices is not permitted by sport or commercial fishermen. When the traps are received from manufacturers, they are not rigged sufficiently to withstand the rigors of trapping fish near undersea ledge formations.
Traps are sometimes snagged on nearby ledges as they are hoisted toward the boat. The side where the cable is attached must be reinforced using a rebar rod to avoid deforming and possibly rupturing the trap.
Heavy metal ballast weights are fixed to the bottom of the traps and cable attachments are added on the reinforced side.
The trap’s wire lattice is cut at the top to create small openings for stringers (cords with attached wooden blocks) that dangle bait fish inside the trap. A larger opening is cut on one side of the trap to function as an escape hatch for trapped fish if the trap becomes unretrievably wedged at the bottom.
Four stringers, each with four menhaden bait fish are tied and suspended into each trap’s quadrants, and attached to the trap bottom with a clasp. Additional menhaden are scattered on the floor of each trap.
Underwater video cameras are attached above the entrance of the trap and on the opposite side. The entrance camera monitors fish that may be entering the trap. The other camera allows scientists examine the habitat near the trap and to note other species in the vicinity.
The traps are readied for deployment on the stern of the R/V Savannah. A horn blast from the wheel house signals when the boat is positioned over the reef coordinates.
The trap is pushed off the back deck and sinks to the bottom.
Two floating numbered “poly balls” are clipped to each trap. They are released one by one after the trap goes down. Six pairs of poly balls function as buoys to mark the pick-up location of each trap.
After all the traps are in place, a CTD is lowered over the side of the boat to determine conductivity, temperature and depth, as well as salinity, of the fish sampling site. CTD data is transmitted and stored electronically in the dry lab.
Ninety minutes after they are dropped, the fish traps are raised in the order in which they were laid.
Last night scientists and crew were line fishing for reef fish to supplement the trapped specimens. There were some amazing fish catches using the rods and reels off the stern of the R/V Savannah. I didn’t catch any fish, but I did manage to catch some amazing nighttime pictures of the activity with my camera.