Monthly Archives: November 2012

INTERNS HELP TAG A GREAT WHITE SHARK

great white shark trackingOne of the most exciting events that an intern here gets to participate in is the tagging of a great white shark. On the morning of 3 November, we were asked to perform this task. Oliver Jewell is the manages our intern group and is also one of the resident biologists studying shark movements and the proposition of home ranges. Our intern team that day was comprised of Matt Smith, Tess Mahoney, Giovanni Vasser, Dawn Watson, and Christopher Algero. Also with us that day was our technology specialist, a highly skilled and fearless man named Ed. We gathered early that day to prepare the vessel, Lwazi, for her brief expedition. Once she was loaded with chum, had her GPS and radio attached, and the tracking hydrophone and computer were on board, Lwazi was driven down to the quay and launched.

After chumming for what did not seem like a very long time our first shark arrived. She was a large shark and would not be our last large shark of the day. Not 20 minutes had passed after her arrival before we were surrounded by sharks of sizes large and small. The duties at this time were important as those on their positions were at their best this day. Tess Mahoney and Dawn Watson were in the crow’s nest on the lookout for sharks, their words were relayed down to the people on deck so that no one was surprised by a shark. Listening closely to Tess and Dawn’s warning were Christopher, Matt, and Gio. Chris was on the bait line, it was his job to entertain the sharks and direct them closer to the boat when the time for tagging had come. Ed and Matt were on the chum line, their slosh of fish mush poured expertly from the bucket brought the sharks to the boat. Gio was working the decoy line, his duty was similar to Chris’ but with a chewy fake seal. Finally last but certainly not least was our skipper and team leader, Oliver Jewell.

After chumming for some time the waters had not emptied but cleared shortly of sharks. The bait line and decoy lines sat still on the surface. Shark, “Rita” took advantage of this fact. Her first strike was fast and powerful but Chris withdrew the line in time before she got to the bait, just as he thought the bait was safe she swiftly turned about for a second and immediately a third strike. After much deliberation Oliver decided to tag this swift shark.

Her shape was unique and intrigued our crew. She had a much sharper nose and was thinner than most great whites. This is most likely due to her eating pattern but nonetheless was a noteworthy trait. She had several injuries including a deep cut on her caudal fin. Another shark that had scars all around its face, aptly named “Maori”, was also near by. This same shark and several others had also attempted several times to investigate the chum bucket along with its accompanying crew to no avail. No avail other than to scare Ed and Matt that is.

When Oliver had prepared himself and his equipment, he stepped up to the proverbial plate and to the literal railing. He instructed Chris where to bring the shark when she passed again. It was just this moment that Tess and Dawn had spotted “Rita” rising from the depths as if she was some aqueous phantom from a Lovecraft epic. She approached the bait and in as much time as it takes me to write “the end” it was all over. Oliver had tagged her just beneath her dorsal fin. The crew took a brief moment to celebrate their successful tag and exchange high fives but there was still work to be done. We put away the chum and chumming supplies to being tracking.

We then tracked “Rita” for five more hours relying on the energy burst we had all received from the tagging along with some cheese and tomato sandwiches that had been prepared by the kitchen staff at the Great White House for us to eat. The tracking went swimmingly well although in later days “Rita” would prove to be a tricky lady to track in the coming days, but that is a tale for another time.

GIGANTIC CALVES AND THINNER MOTHERS!

Gradually as the calves are getting larger (both longer and thicker) – their mothers are getting thinner! The mothers do not feed while they are here off the South African coast, but sustain themselves from their thick layer of blubber, which they build up while they are feeding in the Sub-Antarctic waters from January to May.

The southern right whale mother and calf pairs are ruling the bay at the moment! Some days we have had more than 30 pairs. They mainly spend time travelling slowly along kelp, relaxed, rolling, and logging in the same place. The calves are by far the most active and often breach and play around the mother. Maria has been tracking the detailed behaviour of the mother and calves, and they are spending lots of time travelling, milling, or being submerged.

We have had at least five brindle calves frequenting the area. Since most of them have very distinct markings we were able to tell them apart.

Brindel calf

brindle calf

We had the dolphins on two occasions. A small group of Indo-pacific humpback dolphins had a feast where they were so active that the fish were thrown into the air. Also, the Indo-pacific bottlenose dolphins visited the bay and spent almost two hours surfing the waves.

The annual aerial survey of southern right whales off the South African coasts also took place in October. It was the 34th time that the Whale Unit from the Mammal Research Institute (MRI) of Pretoria have conducted the survey. Meredith Thornton, Ken Findley and Andre´ du Randt from MRI, were responsible for carrying out the survey this year.

They started on the 8th of October. The survey team takes photos of the callosity patterns of the mothers, each whale has a unique pattern and can be identified by this. Later the pictures will be analysed and matched to the current catalogue.

southern right whale heads

The different callosities have different names related to where they are positioned on the head of the whale.Behind the blowhole = Post blowholes; Side of the blowhole = Teardrop/subs; In front of the blowhole = Coaming; Along rostrum = Rostrals; On the edges of the lips (longer curved ones usually, if present) = Lip callosities; Large one in the front = Bonnet; Either side of the bonnet underwater = Chin callosities; Either side of the head in line with the blowhole, below the water & above the eye = Eyebrow callosities. Picture from Meredith Thornton, MRI.

Due to the harsh weather conditions the aerial survey was only finished on the 4th of November. Normally it is completed before the end of October and takes a maximum of two weeks. It is always a pleasure to have the team here and DICT hosts the team when they come. Thank you Meredith for the pictures.

Two special guests made it all the way from Sweden; Anna’s mother and cousin. They spent two weeks in the Greater Dyer Island area and went tracking with the team, diving on the shark boat, whale watching on Whale Whisperer, and flying with African Wings! Anna’s cousin went back with an even stronger determination to become a marine mammologist.

The team is looking forward to the summer and calmer weather conditions. Day by day we are seeing more and more tortoises on the roads when driving to Pearly Beach – a sure sign of summer approaching.