Lemon Shark Aggregation in Jupiter, Florida

Every year from January to mid April, lemon sharks meet and aggregate along the Eastern Coast of Florida.  Lemon sharks grow up to 13 feet long and average approximately 10 feet.  They are found in the shallower waters of the Bahamas and Caribbean as well as Florida. Lemon sharks get their name from the yellowish tinge to the skin on their back (with an off white belly) that is great camouflage when they are resting on the sea floor.  The skin has a mottled and pitted lemon feel to it.  The lemon shark is one of the larger species of sharks.  According to http://www.flmng.ufl.edu, Lemon sharks have an average growth rate of .21 inches/year.

  This shark is a blunt nosed shark with two dorsal fins of similar size. The snout is round and shorter than the width of the mouth. Its upper teeth are narrow and broad with triangular smooth-edged cusps and finely serrated bases. The lower teeth are narrow and triangular with smooth-edged cusps. Lemon sharks have between 3 and 5 ridges, or rows, of teeth on both the upper and lower jaw. Their long thin sharp teeth are designed to catch slippery fish, the mainstay of the shark’s diet.  Did you know, a young lemon shark loses an entire set of teeth, one at a time, every 7-8 days. They are grown rapidly in the back of the jaw and as the shark loses teeth they are rotated forward.

These sharks are know to really get their groove on in Jupiter, Florida.  The Shark Foundation has set up 18 acoustic monitors to track the sharks they have tagged for monitoring.  This project has given us an indepth look at both the mating habits of the female and the nomadic habits of the male lemon sharks.  From this one study, it has been found that a critical temperature of 24 ° C has now been identified as the most likely cue for both local movements and seasonal residence.

One might also ask about the birth defects from inbreeding of such as large gathering of sharks.  To avoid inbreeding problems within their relatively small populations, the sharks appear to have developed a mating strategy not yet unobserved in other shark species.  Female lemon sharks return to their natal grounds each year, much like sea turtles while male remain nomadic.  Females can also be impregnated by several males, which may cause a more varied gene pool.

Just recently the FWC has imposed a ban on fishing for these incredible creatures to protect them.  Females produce a litter only every other year, and it takes a long time for the young to come to maturity, 12 to 15 years.  Many of these juveniles will congregate in Bimini along the mangroves for protection until they reach maturity  to protect them from bigger sharks.   Without a fishing ban, it has been said that commercial fishing could wipe out the species within two years.

According to http://www.fisheries.vims.edu, Lemon sharks in their first year have a survival rate of only 39%, depending on conditions. After their first year this percentage increases dramatically to 88% annual survival rate.

Riveiera Force E has some trips planned to see this massive event.  The Jan 13th boat is full but they have another trip planned on the 26th.  Call them direct for details.

Also, Dr. Sam Gruber and his team from the Bimini Shark Lab are back in town next week for 2 months for the annual research on the winter aggregation of lemon sharks. Spearboard has helped out in the past as evidenced by these threads.  Lemon- Aid 2013 is under way on spearboard.com.  They are once again asking help from Spearboard members diving off Jupiter and Palm Beach. Please report on this thread any sightings of lemon sharks in that area for the next two months. You can also donate fish caught for bait to Dr. Gruber.  Here is the link for this post. 

SharkSavers SharksCount Program is a global “citizen science” initiative. They are reaching out to divers across Florida and providing tools to help you log and share your shark sightings so this important information can be applied to local conservation planning.

If any any way, big or small, personally or financially, you would like to help Dr. Gruber you may contact him at:

Bimini Biological Field Station

9300 SW 99 St

Miami FL 33176-2050

I think I shall have to add a boat trip out to see this impressive event.  Add this to my bucket list this year!