Wednesday, June 29, 2016

Cleaning Stations - Spas of the Sea

Image by Amy Kelley - Stoplight Parrotfish at cleaning station
Believe it or not, sea creatures have to "bathe" and visit the "dentist" to stay healthy.  They must get rid of internal and external parasites  and dead skin by getting their scales, teeth, nostrils, and gills cleaned.  

There are specific spots around the reef that are known as cleaning stations.  Fish and creatures that are familiar with the reef already know where to go, but visitors just passing through look for signs.  Cleaning stations are often on top of a coral head or in spaces between rocks or coral heads.  They are "staffed" by small fish such as wrasse and gobies, as well as cleaner shrimp.  

Image by Soratobi1 via Wikipedia
Image by Nathanial Kelley - Petersen Cleaner Shrimp

Cleaner shrimp wave their antennae around wildly (much like the Wacky Waving Inflatable Arm Flailing Tube Man) to let their "customers" know that they are open for business.  The fish and sea creatures swim up to a cleaning station and take the proper position to indicate that they want to be cleaned.  Opening their mouth wide or inclining their body lets the cleaners know that it's time to get down to business.    

Why do the cleaner fish and shrimp do this?  Do they get paid?  Yes, they do.  In the form of food.  These cleaners depend on the parasites and tiny organisms the pluck off of their customers.

Image by Saad Alafaliq via Flickr  - Moray eel at a cleaning station


Image by Philippe Bourjon via Wikipedia - Goat fish at a cleaning station
Image by Richard Ling via Wikipedia - Grouper at a cleaning station

But why don't the bigger creatures just eat the cleaners?  Well, if they did, they would throw off the natural balance that exists among the reef creatures and the cleaners would no longer clean them.  As a result, the bigger creatures would end up covered by parasites which they cannot remove on their own, and they would ultimately die.  This relationship of creatures working cooperatively and helping one another is called a symbiotic relationship.


Image by Nathanial Kelley - Great barracuda at a cleaning station
It's amazing to see this symbiotic relationship in action.  Especially when you get to see a top predator, like a barracuda, opening it's mouth, exposing its sharp teeth, and allowing small fish and shrimp to clean between his teeth and inside of his gills.  Not to mention the bravery of those little guys crawling into the mouth of a fish that would happily eat them under other circumstances.  But the cleaning station is a safe zone, and they all respect that fact.


Image by Amy Kelley - Blue tang at a cleaning station

Next time you are snorkeling or diving near a coral reef, slow down so you can observe the fish and their behaviors.  Now that you know what to look for, you will likely be able to find a fish visiting a cleaning station!  Don't get too close, or the fish being cleaned will get scared and swim away.  Take a minute and watch the cleaner fish and shrimp do their job, while the bigger fish enjoys his spa treatmentIsn't nature incredible?

 

Wednesday, June 22, 2016

Turtle with a long tail!

The other day while we were out at Capella Bay near Buck Island, some of our divers got a rare treat!  A big Hawksbill sea turtle with a REALLY long tail swam by.  None of them had ever seen a turtle like this before.  Only male sea turtles have a really long, beefy tail.  

Image by Jason Crump - Male Hawksbill sea turtle

The females have a much shorter tail, mostly hidden beneath their shell.  This is the most obvious distinguishing characteristic that helps us identify a male from a female sea turtle.




Why is this such a rare sighting?  We see sea turtles relatively often (considering they are endangered species) , but over 99% of the time we are looking at female sea turtles.  So where are all of the males hiding?  Male sea turtles spend most of their lives out in open ocean.  Believe it or not, life is safer for turtles out there.  But why?  There is a much higher population density in the near coastal environments.  In open ocean, creatures are so spread out that their chances of running into a predator are much less than in the coastal areas.  Male sea turtles only visit the near coastal areas to mate with the females and then head back out to open water.

Image by Nathanial Kelley - Female Hawksbill sea turtle

The female sea turtles have to take the risk of coming into the near coastal areas so they can feed.  They need to consume lots of calories to get big and strong, because when they are mature they will have to produce over 100 eggs each time they nest.  Female sea turtles nest multiple times per season.  That requires a lot of energy!




A huge "THANK YOU!" to our friend and local diver Jason Crump for capturing footage of this rare sighting of a male Hawksbill sea turtle and allowing us to share it!

Wednesday, June 15, 2016

The Frustration of a Foggy Mask

Image by rkit via Pixabay

Have you ever had a mask that fogged up continuously?  You want to enjoy the beautiful colors of the coral reef, but all you can see is a foggy blur?  You spend more time messing around with your mask on the surface than you do with your face in the water.  You feel jealous at all of the amazing things everyone else keep seeing.  "Did you see that octopus!?"  "Did you see that flounder?"  "Look, a turtle!"  Despite your most noble efforts rinsing the fog out every 10 seconds and squinting your eyes to see past the fog, you don't see anything! 

Image by Petr Kratochvil via Public Domain Pictures Edited by Amy Kelley

Well, stress no more.  With a few tricks of the trade you will be seeing clearly in no time.

You may notice that new masks tend to fog even more than old masks.  Why is this?  When masks are assembled in the factory, a thin film of silicone ends up on the lenses.  That film helps make a water-tight seal between the lenses and the frame of the mask, but it also causes the mask to fog like crazy.   

The coating on the lenses can be removed in a few different ways.  

Image by William Warby via Flickr
  
Toothpaste (the white kind, that is slightly abrasive) can be used to scrub the film off the inside lenses by rubbing it around in a circular motion.  

Image by Christian Carter via YouTube
 
You could also use soft scrub to do the same thing.  

Image by Sun Ladder via Wikipedia

The quickest and easiest way to remove the film is by burning it off.  Carefully take a lighter and move the flame around the inside of the lenses.  It is important that you do not burn the silicone mask skirt or yourself when you do this.  When you notice a black film appearing, you will know that you are burning off the silicone residue.  Let it cool, then wipe away the film with a paper towel or tissue.  You can repeat this process until the black residue is no longer appearing.

After you have removed the silicone film and the lenses have cooled, you can apply a commercial defog solution for best results.  We sell Trident de-fog at the dive shop here in Secret Harbor.  

Image by Stephanie-inlove via Deviant Art

The next best option is using diluted baby shampoo.  Any soap would work, but the "No tears" aspect of baby shampoo makes it better.  As a last resort, if you don't have anything else, spit can also do the trick...but it doesn't work as well or last as long.  The key to using any defog solution is to apply it right before entering the water, and only give it a light rinse so the residue from the defog is still on the lenses.  If the lenses have a slippery coating, any condensation will bead-up and fall down to the bottom of the mask, leaving your view crystal clear.  


Image by OpenClipartVectors via Pixabay

If your skin is significantly warmer than the water temperature, the temperature difference will cause the inside of your mask to condensate more.  

Image by Rudyasho via Wikimedia Commons

To minimize this effect, submerge or splash your face to let your skin cool before putting your mask on.


Happy snorkeling!  I hope your next time out on the water is fog-free and full of amazing fish and creature sightings!

Image by Amy Kelley

Wednesday, June 8, 2016

What's that crackling sound?

Have you ever noticed that if you put your ears in the water near a coral reef, you can hear a crackling sound?  That sound is produced by the many species of parrotfish, sea urchins, and snapping shrimp!  

Parrotfish are one of the most abundant and colorful larger fish to be seen on the coral reef. 

Princess Parrotfish - Image by Laszlo Ilyes via Flickr

Stoplight Parrotfish - Image by Adona9 via Wikipedia


Queen Parrotfish - Image by Amada44 via Wikimedia Commons

Here in Secret Harbor and around the Virgin Islands you are likely to see numerous princess parrotfish, stoplight parrotfish, queen parrotfish, and various others.  Parrotfish are named for their bright colors and fused teeth that resemble a beak.  They predominantly use their pectoral fins to propel themselves through the water, moving them up and down like miniature wings.


video
Video by Amy Kelley  - Parrotfish eating

That crackling noise you hear is made by the parrotfish eating.  They scrape algae and coral polyps from the reef, often breaking off chunks of the coral's limestone skeleton.  Sound travels about four times faster and farther in water than it does in air.  That's why you can hear so many parrotfish munching on the reef at any given momentThey crunch and grind down the limestone, digesting the organic matter and getting rid of the indigestible bits.  


video
Video by Amy Kelley - Parrotfish pooping

If you watch them for a while, you will see them magically make sand when they poop out the crushed limestone debris.  Thanks to the parrotfish for keeping our beaches beautiful and full of sand!  

Check out this hilarious but informative video.    




Video by Sisbro Studios via YouTube

Here's a great article and video by Scientific American: Parrotfish Poop Makes Beautiful Beaches

video
  Video by Amy Kelley - Long spine sea urchin

Sea urchins also contribute to the crackling sound on the reef.  They mainly eat algae, scraping it off of coral and rocks using 5 teeth-like plates on the bottom of their bodies.  Listen to a symphony of sea urchins via ABC Australia and scientist Ann Jones.

Image by Steve Childs via Flickr: Gobi and shrimp
Snapping shrimp use a specialized claw to produce a loud snapping sound for defense, hunting, and communication purposes.  You can often find them hanging out with gobies and hiding inside of corkscrew anemones.


video
Video by Amy Kelley - Snapping shrimp

Aqua Action Dive Center rents and sells snorkel gear if you'd like to snorkel in Secret Harbor and observe this underwater symphony first-hand!  Or better yet, come try scuba diving with us so you can spend some time under the sea and get an even closer encounter with our colorful fish and creatures!





Wednesday, June 1, 2016

What happened to this shark?

WARNING!  GRAPHIC IMAGES

Sharks are one of my favorite animals.  They are beautiful, graceful, intelligent, and powerful.  They are an important apex predator and they keep the ocean in balance and healthy.  I love seeing sharks in the wild.  My latest encounter with a shark while on a dive was a shocking one, and I will never forget it.

We were diving Cow Rock, probably the most famous dive site near St. Thomas in the US Virgin Islands.  It is located inside of a marine sanctuary, so the reef is especially healthy.  Cow Rock is a dive site with abundant marine life, colorful corals and sponges, numerous swim-throughs.  It is not uncommon to see a reef shark or a nurse shark on a dive at Cow.

This time we saw a Caribbean Reef Shark.  These sharks are usually seen swimming along the reef, but this one was on the bottom.  They are usually very shy, but this shark didn't move at all.  As we approached to get a closer look, we saw that the back section of it's body was missing!  It was clearly dead.  This broke my heart, but also made me want to investigate to understand how this could have happened.  I decided to spend my entire 45 minute dive investigating and taking photos to try to solve this mystery. 

Image by Amy Kelley


Image by Amy Kelley

The shark was severed completely, and everything behind the pelvic fin was gone.  Had it been intact, I think it would have been between 4 and 5 feet in length.  Sharks do not have any bone, just cartilage.  Would that have made it easier to tear apart?  It seemed like it had been there a day or two, since there was some slimy algae growth beginning on its skin, and the flesh was starting to break down.

Image by Amy Kelley

Image by Amy Kelley
Image by Amy Kelley


I'm pretty sure it was a female, since I did not see any claspers near her pevic fins.  Claspers are used by mating males to transfer sperm to the female.  Male sharks and rays have a set of claspers at the back of their pelvic fin while females do not.  

Image by Amy Kelley
 
There were distinct bite marks, especially on the left side of the shark.  It had to have been a sizable creature, based on the bite marks.  If you look closely, you can see a less dramatic mark of where the top teeth of the predator dug into its prey on the top of this shark's back.  Sharks can unhinge their jaws, so their bite mark can be very big and almost circular.

Image by Amy Kelley

Image by Amy Kelley

Image by Amy Kelley

 I searched for teeth from the predator, since they often lose teeth when eating.  Sharks have multiple rows of teeth, and when they lose one, a tooth from the next row will move forward to take its place.  If I could find a tooth, maybe it could help me to identify the shark or estimate the size of the shark that left these marks.  Unfortunately, I did not find any lost teeth.

On her right side there were some more bite marks and some scratches.  I'm not sure that these were inflicted by the same predator.
Image by Amy Kelley


Image by Amy Kelley

I was a surprised not to see too many creatures taking advantage of a dead shark on the reef.  It seems like it would be an easy meal.  I did see lots of fire worms and a brittle star.  And after I stirred things up a little bit with my investigation, some damselfish, yellowtail snapper, and a coney came by to check it out.  My husband was standing watch, and he later told me that he saw two other sharks in the distance, but they were not comfortable approaching with us there.  The sound of our bubbles often deters sharks too.

Image by Amy Kelley

I was still unsure what had happened to this beautiful creature.  

It was a shame that this shark's life had ended prematurely, but I decided that I would not let it be in vain.  I wanted to figure out what happened to her, learn something new from this encounter, and educate others. 

Getting to look into her prehistoric eyes, her complex gills, her powerful mouth and getting close enough to see her ampullae of Lorenzini was an amazing experience on a scientific level.  

It is a common myth that sharks have poor vision.  This is quite untrue.  Their vision in the water is up to ten times better than humans' vision.  Looking into these amazing eyes inspired me to do some research and learn more.  You can read more about shark eyesight by reading this article by Shark Savers.

Image by Amy Kelley
 
This shark we found had 5 gills on each side.  Reef sharks are Requiem sharks, a type of shark that needs to move water through its mouth and over its gills to breathe.  Oxygen is absorbed into the shark's blood vessels and delivered throughout his/her body.  That is why you normally see reef sharks swimming along the reef and not resting on the bottom.  You can learn more about sharks' gills and their anatomy by reading this article by Shark Trust.

Image by Amy Kelley

Ampullae of Lorenzini may just look like tiny pores on a shark's skin, but they are so much more interesting than that.  They are an interconnected system of jelly-filled sensory organs that help sharks detect electrical fields in the water.  The ampullae of Lorenzini enable sharks to find prey by sensing their muscle contractions, to sense temperature changes, and to navigate their way through the water by sensing Earth's magnetic field!

Image by Amy Kelley

Image by Chris_huh via Wikipedia

I hope this is the last time I see a dead shark.  It was both fascinating but heartbreaking at the same time.  Though the mystery has not been completely solved, my guess is that she was killed by another shark.  Either she was injured or ill, or in a dispute over territory.  

Other theories that I heard people say were:

She was hit and killed by a boat propeller - I don't think this is true, since reef sharks are not surface feeders.  They mostly eat fish, rays, and cephalopods (squid & octopus).  Also, the nature of her wounds did not look like a propeller to me.  Finally, she was found in a place that would make it highly unlikely to find boats because the dive site Cow Rock is a definite navigational hazard and the boat would be at extremely high risk of going aground.

Fishermen killed her - I don't think this is true either.  First of all, this is inside of a Marine Sanctuary (though that doesn't necessarily stop some people).  Secondly, the fins were still on the shark and the meatiest, most valuable part of the shark was not taken.

In trying to figure out possible causes of death I came across some extremely interesting videos, which raised new questions:

Shark mating on the Discovery Channel - A male shark bites down on a female's pectoral fin to pin her down so he can mate with her.  Was our shark the victim of a mating attempt gone wrong?  Interesting possibility, but I don't think so because the bite marks weren't right over her pectoral fin.  Plus, eating half of the female would not be a productive way to make baby sharks!

The aquarium official think that this was a turf war.  The female shark was tired of being bumped into by the male shark.  He was in her space.  Watching this video really helped me to understand that this clearly is possible.  There are known to be a couple of reef sharks at Cow Rock, and maybe this female was in another shark's zone.  But her tail was bitten off, unlike in the video where the whole shark was eaten, head first.

This made me realize that there are, indeed, apex predators even above the shark.  Bigger sharks and killer whales are definitely capable of killing a shark.  Not to mention humans, the most vicious apex predator of all.  This doesn't mean that I think an Orca killed this shark, but it does prove to me that there are apex predators capable of taking down a 5 foot reef shark.  I found one image that really makes me think another shark could have done this to her.
 
 Although I am pretty sure her death was all natural and unrelated to humans, please keep in mind that shark populations are incredibly important to our planet.  Without sharks, the apex predator of the ocean, Earth's largest ecosystem would not be able to stay healthy.  Without a healthy ocean, our planet cannot survive.  Read more about why sharks are important at Sharkallies.comAccording to this article by IFLScience, humans are responsible for killing between 100 million and 273 million sharks per year. 

Image by ReefQuest Conservation via Biology of Sharks and Rays
  
Their populations have decreased drastically, and we need to do all we can to save them.  For starters, do not support restaurants that serve shark.  Sadly, there are a few here in the Virgin Islands.  Next, do not support fishing operations that hunt sharks.  Finally, get involved in ocean conservation efforts.  Even something as simple as signing a petition to save sharks can make a difference.    

Here is a video clip of our strange shark encounter.

video
Video by Amy Kelley
 
 I would love to hear your comments.  I am very eager to solve this mystery, so please share this blog with any shark experts you may know!