A new underwater shark capture method used by divers to catch and release nurse sharks (Ginglymostoma cirratum)

Abstract

We developed an alternative capture-and-release method for sharks using a simple poker-andhook tool for divers to quickly capture nurse sharks (Ginglymostoma cirratum) entering the intake canal of a nuclear power plant in Florida. The capture technique consists of using a short metal rod (poker) with a barbless J-hook (size 10/0) to snag the base of a shark’s tail (caudal peduncle), then safely hauling the individual into a boat by the buoy line that has been hooked to its tail. We captured 20 nurse sharks ranging from 11.8 to 80.3 kg, and 9 individuals were monitored over time. Six sharks were released into the canal and 3 sharks were put in an open tank for 23–24 days for daily observations. All hook wounds resulting from this technique were assessed between 9 and 42 days, and no ill effects were observed throughout the study period. The capture method caused a small superficial wound to the caudal peduncle that averaged 11.3 mm2 (standard deviation 8.7; n=23). Wound closure was observed after 9 days and re-epithelialization was almost complete (or the wound had completely healed) between 22 and 42 days. Landing nurse sharks this way is less traumatic than traditional methods (e.g., angling, netting). This study provides preliminary information on, and validates, the use of this tool as an efficient and less invasive capture method than traditional methods and as a method that could be applied to broader areas of shark research.