Random Stories

Shark Defense
In mid-September, two guys from Shark Defense, Inc. came to the lab to run some tests on a shark repellent they're developing. We went out to the spot where we usually to the shark dives, and when we baited the water, half a dozen or so 5-6ft reef sharks showed up, as usual. One of the Sharklab staff was in the water with a video camera to shoot the experiment, and I was in the water with a still image digital camera. One of the SDI guys got in the water with a canister of repellant, and I stayed behind him with the camera to take pictures and also watch his back in case sharks came around behind him. When the sharks came in close to take the bait, the repellant was released into the water. Immediately, the sharks scattered. When more bait was thrown into the water, they wouldn't take it. Instead, they circled below near the bottom, if they stayed around at all.

Later in the day, they tested the repellant on juvenile lemon sharks from our pens out back. We put the sharks into tonin immobility (sleep) by flipping them over onto their backs. Once in tonic, the SDI guys released chemicals near the sharks to test their reaction. First they would test a controls, such as tumeric, or saline solution, by injecting it into the water with a syringe. The sharks showed no reaction. Other chemicals induced a small couch from the shark, but when the repellant they are developing was released, it caused the sharks to violently come out of tonic. This is good. It means that if the chemical is so strong that it wakes them from tonic, then it would act as a good repellant.

Juvenile Lemon Workup
For the last few days, we used gillnets to capture sharks on out back behind the lab. By yesterday afternoon, we had eight juvenile lemons in our pens out back, and each one had to be worked up. First, we transport the shark from the pen to our boat by walking it out by hand. We do this by catching the shark in a dipnet and grabbing it just in front of its first dorsal fin. Lemon sharks are extrememly flexible, so it's important to make sure your hand does not slip back farther. If that happens, the shark can twist itself enough that it can bite you. Once we walk the shark out to the boat, we put it in a measuring trough, which is just a large pvc pipe cut in half, filled with water, and with a measuring tape along the bottom. We take several length measurements, its weight, check the sex, check for a PIT tag, take a DNA sample, note its condition (such as fin rot, any scars, distinguishing characteristics, etc), and check the status of its umbilical hole (closed, open, just closed). It's very cool to handle the sharks during the workup, and even though they are small (less than 100cm), they can still do some serious damage if they bite. In the picture above, I'm taking the shark out of the measuring trough after the workup and about to walk him back to the pen. The hardest part of handling the sharks is fighting the reflex to let them go when they start thrashing. If you hold them correctly in front of the dorsal fin, just behind the gills, they don't really fight. They kind of just continue to "swim", only they're not going anywhere because you're holding them. However, you can feel when they're about to "go" because they tense up, and you know a thrash is coming. If you let go while they're thrashing though, they're usually pretty upset so they're looking to bite. And if you happen to release it when it's facing you, there's a good chance it will bite you. Unfortunately, it's also not good to squeeze the sharks hard. That's another instinct you need to fight when they start thrashing. Instead, you're supposed to just stiffen your fingers without squeezing harder. The sharks will calm down after a few seconds, but it's hard to not let go when they thrash like that. And all the while you absolutely have to make sure your hand does not slip back behind that first dorsal fin.