Gillnetting is the primary means by which the BBFS catches juvenile lemon sharks for research purposes. Juvenile lemon sharks used in our Current Research are caught with gillnets, and every June, the BBFS captures the entire cohort of lemon sharks in two nursery areas in our PIT Tagging Program by using gillnets.
Gillnet set off the mangroves |
Juvenile lemon sharks inhabit the shallow mangrove lagoons around North & South Bimini. Their range is relatively small during the first 3-4 years of their lives, so laying gillnets in these areas is an effective way to capture and survey the populations of young sharks.
Each gillnet is ~180 meters long, and made from a mesh of 20 lb. test monofilament. The nets are weighted along the bottom, and reflective floats are attached to the top of the net to keep it hanging upright in the water.
At one end, the nets are attached to mangrove roots along the shoreline. The gillnet is then pulled straight out, perpendicular to shore and anchored at the other end.
Throughout the entire set, the gillnets are checked every 15 minutes to insure that no fish that are caught are harmed. Sharks that are caught in the nets are released and brought to one of the skiffs for transport. Any by-catch is immediately released.
Lemon sharks that are caught are transported to a holding pen, which is pre-constructed in the lagoon with plastic fencing.
Every lemon shark that is caught is evaluated for signs of stress, and the shark's condition determines the next step…
Juvenile lemon shark in the
holding pen |
If the shark is healthy and unstressed, it is worked up immediately. The data collected from the juvenile lemon sharks includes: sex, pre-caudal length measurement (PCL), fork length measurement (FL), total length measurement (TL), and a small fin clipping is taken for DNA & genetic analysis. Any additional comments about the shark's condition are also recorded in our database. After the work-up, the sharks are put in a pen so that their condition can be monitored.
Sharks that are removed from the gillnets, and appear to be stressed, are immediately placed in the holding pen. The sharks are then left to swim & recover before they are handled or worked-up.
Every juvenile lemon shark that is caught, is kept in the pen until the next day and fed. This is to insure that the sharks are released healthy, and with full stomachs.
For more information about gillnetting, see Eric Cheng's wetpixel.com feature on the 2003 BBFS PIT Tagging Program.
For more information on what research is done with the juvenile lemon sharks, see our Telemetry Overview.
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