November meeting

At this month’s club meeting, we have a special guest, Dr Laura Ryan to talk about shark behaviours and deterrents. Come to our meeting to learn more about sharks. There will be a presentation of recent activities and a meat raffle. The spear gun and fins raffles are still ongoing as well.

Below is the abstract of her talk:

Shark perspective: vision and electroreception in sharks 

It is important to understand a shark's behaviour from their perspective. Sharks have very different eyes to our own so see things very differently. They also have an extra sense, which is the ability to detect weak electric fields. Neurobiology Dr Laura Ryan will discuss these senses with the implication this can have in regard to human encounters with sharks. As a keen surfer and free diver, Laura’s research has implications in the design of shark deterrents and she will share her extensive knowledge on current commercial shark deterrent devices.

We covered a lot of grounds at this month's meeting, including shark deterrents, competitions and social dives. Laura started her talk with the history of shark deterrents. The earliest research on shark deterrents can be traced back to world war II. Most of the studies were based on trial and error. Hence, Laura aims to develop a more scientific way to study how to prevent shark bites. 

 

Sharks have very bad vision. They don't have colour vision and can't see things very clearly in the water, just as we do. However, their eyes can pick up high contrast in the water, which helps them see something approaching in the murky water. Laura looked into how different shapes of decoys can attract shark attacks. Shapes similar to seals may be mistaken and attract the attack from the great white as they are very visual hunters. 

 

Sharks are also equipped with electroreceptive organs. They can detect bioelectric fields and use them for hunting. One of the shark deterrents developed based on this electroreception is the shark shield. Some members are curious about whether to turn it on all the time or not. Laura suggested that sharks that we cannot see are the most dangerous ones. Therefore, it is better to let it on all the time when using it. However, she also emphasised that these devices were made to give you the time to leave the water, not that you can swim with sharks.

 

In the end, Laura answered many questions and had inspiring discussions with our members. We all learnt a lot about sharks!

After the talk, our vice president Shaune talked about the Taylor shield, which was held at Ulladulla earlier this month. Many members attended the competition and had a great time. He encouraged everyone to attend the competition because you will be able to meet up with experienced divers and learn from them. It is also a very good social event.

 

Mick also shared his story of competing in the Sydney Kingfish Cup this year. He shot a 14.95 kg kingfish and won the championship. Mick and Ko dived both days during the weekend. The first day was granted with a warm and sunny day. However, the water was murky. They didn't find much bait fish but a big school of Australian salmon. The second day got worse and even had a bit of rain during the day. The water was green and visibility was no more than 3-4m. Ko spotted a school of kingfish but he rushed and took a bad shot. He surfaced and told Mick to dive down immediately. Mick dived down and saw nothing. Suddenly, two kingfish came into his sight. He waited and plugged a headshot on one of them. Andy and Ryan, who competed at the kingfish cup, also got their 8th and 9th prize on the presentation night. Congrats to them all!

October Meeting

At this month’s meeting, we had our president – Kade talk about how to chase kingfish in the Sydney water. Yellowtail kingfish […]

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