Thanks to the annual PIT Tagging Program, named for the type of tag used (Passive Integrated Transponder), the Sharklab maintains the largest and longest running mark-recapture and genetic database of any shark population in the world. The fishing, which is done with ~180 meter long gillnets made from a mesh of 20-pound test monofilament, is carried out in two major nursery areas, referred to as “The North Sound” and “Sharkland”. Gillnets are illegal in The Bahamas, but the lab maintains a research permit that allows their use (and we do so in a non-lethal manner). Each nursery is fished for six nights, with gillnets set at the same three stations each night. The nets remain in the water for twelve hours, a full tidal cycle, and are checked every fifteen minutes, with all captured sharks removed and transported to a fourth boat that serves as a tagging station.
|Photo credit: Matt Potenski|
|The Bimini Sharklab could not continue if it were not for our hardworking crew of dedicated volunteers.|
Sharkland, the first nursery to be fished, traditionally yields the most sharks of the two nurseries and is particularly hectic on the first night. This year’s catch, at 117 total (49 on the first night), is the lowest in recent years. Interestingly enough, neonates (newborn lemon sharks) constituted 56.4% of the total Sharkland catch, compared to last year’s 25.6%.
While the twelve nights of fishing during PIT may seem long and tiring, they are nothing compared to the twelve years, on average, it takes a lemon shark to reach sexual maturity. The slow-growing, late-maturing strategy, combined with relatively low reproductive output (fecundity), is characteristic of all sharks, not just lemons, and makes them highly vulnerable to over-fishing. If we as a planet are to successfully protect these apex predators, it is imperative that research such as that of Dr. Gruber’s Sharklab, continues to shed light on the life cycle of sharks. While the movement to protect sharks is there and the momentum is growing, conservation policies will only be effective if they are based on sound, empirical research.
Tyler Clavelle is the assistant lab manager at Sharklab. If you are interested in volunteering at the lab, please do not hesitate to contact Dr. Gruber at email@example.com, or our station managers at firstname.lastname@example.org. Please also visit our website www.miami.edu/sharklab for details.