Matt's Whale Shark Blog: Back to Work and Lucky Sevens

Posted on January 28, 2008
Written by: Shark Savers

January 2008

I returned to Tanzania after a short holiday break and got right back to work. I spent one day in Dar es Salaam, just running some errands (and finally getting a cell phone that works here). I proceeded to spend the rest of the day on the phone and internet trying to organize and schedule my work. Early the next morning I hopped on a plane to Mafia Island. I settled in to the WWF house and set up getting out on the water for whale sharks.

I was itching to get out and see some sharks. I heard good reports from my sources – there were supposed to be many sharks in the area at this time. I woke up excited to go get wet. I set up my camera and snorkel gear and had a truck drive me the 14 kilometers across the island to the harbor on the west side. There had been a heavy rain in the night, and the road across to Kilindoni was pretty bad. It is usually an adventure driving this dirt track, but today the rains had made it extra slippery and rutted. Halfway across I looked up to see a huge, distinct rainbow arcing across the sky and offset by dark clouds behind it.

Whale Shark tagged with 0558. Photo: Matt Potenski

I jumped on one of the ecotourism boats and smiled as I saw two fins cruising just offshore. Within a few minutes I was in the water with one of these gorgeous giants. In three hours we encountered about 8 sharks, all swimming on the surface and actively feeding. I observed one shark with an old tag completely grown over with algae. I dived down and gently rubbed some of the green mass off the tag to reveal the number 0669. I remembered this shark and tried to swim around to the other side to get a look at its pectoral fin. This individual has an old shark bite wound in the trailing edge of its right pec fin. Sure enough, I observed the distinctive wound. This shark is an almost seven meter male that I originally tagged in January of last year. One whole year has gone by and he is back to enjoy the Mafia plankton buffet once again. I took some pictures and generally enjoyed being back in my “office”.

Buoyed by the great first day back, I spent the evening getting all my tagging gear together and checked so that I could start work in earnest the next day. I again went out with one of the resort boats and was able to encounter many sharks. I was able to put out my first shark tag of the season on Jan. 15th, when I found a 6.5 meter long male. It has been almost a year since I fired the speargun, but old habits stick and I made a fine shot into its back just below the dorsal fin. The shark didn’t react and swam calmly away, trailing its tag with #0556 displayed proudly. The next day I was able to deploy another tag - #0560 on another good sized male. I spent four out of my five days on Mafia Island on the water and was able to record six tagged shark resightings along with the two taggings.

I spent the last night on the smaller island of Chole at a resort owned by friends. It is one of the most beautiful and unique places I have ever been – all the rooms are treehouses and they are built within a complex of old ruins, huge baobab trees, and amazing sea views. So, four days of work were in the books and I had one relaxing night to catch my breath. I had to get up very early and take a ferry back to Mafia where I took the truck ride back over to the harbor.

I was rendezvousing with the ship Kairos to start another expedition. I got on the ship and make some quick hellos then jumped right into a whale shark lecture so that we could get out on the water. We went out to a sea rife with fins. We must have seen at least a dozen sharks. I didn’t waste any time and put out another two tags this first day. Surprisingly, I tagged two females. The population here at Mafia is heavily biased towards male sharks (approximately 3:1). I gave the two girls some body jewelry corresponding to tags #0561 and #0587. The following day we headed out, but the sharks were much harder to find. We finally located a few and I was able to put out an additional two tags - #0588 & #0630 on two males. The second one, #0630, had a very distinctive injury. It has a large horizontal cut in the front of its dorsal fin, causing a large flap to be folded over. As a scientist, I try not to anthropomorphisize my study subjects, but I couldn’t resist affectionately calling this shark “Curly”.

From a research standpoint this was a good day, but I couldn’t help feeling a little letdown after such a tremendous previous day. We came to the third day where I would just have the morning to observe sharks. The morning started slow with us looking around for a while before I finally spotted a fin. We found probably the smallest whale shark I have seen here at Mafia – almost 3 m (maybe 8 feet long) – a real shrimp. This shark was too small to tag, and was also swimming very fast – I couldn’t keep up with its speed. We searched elsewhere and found a few other sharks, including two that had lost their tags from last year. They both had the tag streamers hanging out of their sides, but the placard with the number was missing. I took some pictures to try to identify them by their spot patterns. I managed to retag one of these sharks – it has a wedge shaped cut in the back of its dorsal fin that makes it easy to identify. It was shark #0846 and is now # 0632.


Whale shark with free diver. Photo: Matt Potenski

We get a very special treat the last day as well – one of the whale sharks swam very close to out boat and then almost comes to a stop. We all got in the water and it swam very slowly and calmly about 6 feet below the surface. We stayed with the shark for almost a full 20 minutes, and I was able to get some very nice pictures of the shark. He just glided and let us freedive around him – every now and then rolling his eye to get a better look at us. It is a special way to end an excellent week with the whale sharks. I got seven tags out and will be back to see the sharks again real soon. Seeing some of the wounds on the sharks makes it easy for me to identify the shark, but also serves as evidence of the dangers to these docile behemoths even in areas where they are not actively fished. It reminds me that I still have a lot of work to do. Here in Mafia Island my job has two sides, science and outreach. A large part of what I want to do is to tag sharks so that we can learn about the population utilizing Tanzanian waters. However, I have almost as important a job in bringing my research home to the local inhabitants of Mafia Island. A group has formed on the island with the sole goal of promoting whale shark conservation, called WHASCOS. I am working hand in hand with WHASCOS to aid them in regulating ecotourism group sustainably, educating local fishermen, and helping to build a real sense of stewardship and value for the benefit of both sharks and people in the area.

I will be spending almost a whole month on Mafia Island thanks to the continued support of WWF-Tanzania, which will enable me to both be on the water with the sharks, and in the towns connecting the sharks to the people. Science helps immensely, but it takes more than science to effectively save sharks. I will be spending almost the entire month of February on the island and will hopefully get lots of work done. I will post more updates as my research continues…


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