Considering it is one of my most favorite dive sites, it had been way too long since I had been for a dive at Julian Rocks at Byron Bay. While I love my chosen degree and profession, it had slowly began to feel like I spent majority of my time inside learning about marine creatures rather than being underwater interacting with them. I always learn best when I am in the moment interacting with something, so I took a ‘research’ day and made my way to Sundive at Byron Bay. We jumped on Sundive’s new and blue ‘Moby Duck’ boat and headed full force to the big rock. The usual suspects were there, Leopard Sharks, Wobbegongs, Rays, Mantis Shrimps, Morays, and the big schooling pelagic fish that make the rock "big-stuff" heaven. However, the stand out of the dive was a very large Queensland Grouper. I had been diving with Queensland Groupers a few times throughout my diving ‘career’ but had never seen one at Byron, and never seen one that big!
Due to her demanding, yet fleeting personality (yes, I am still talking about the grouper), I’m going to say she was a female so I deemed her ‘Big Sal’. Queensland Groupers, such as Big Sal, feed on lobsters, juvenile sea turtles and fish .. including small sharks. They can grow to a massive 3m and can weigh up to 600kg, thus, they are the largest bony fish to live on coral reef systems. Throughout their life, Queensland Groupers change colour; Juveniles have irregular black and yellow markings, while adults are primarily green-grey or grey-brown.
Unfortunately, these guys are important in subsistence fisheries, commercial aquaculture and recreational game fishing. Juvenile Big Sals’ are sold in the ornamental trade as a “bumble-bee grouper” due to their colouration. It is believed that large individuals of Queensland Groupers may be ciguatoxic - which, when consumed, is extremely dangerous to humans. Ciguatoxins are produced by the dinoflagellate, Gambierdiscus toxicus. These dinoflagellates are then eaten by big coral reef fish, such as Big Sal, which will accumulate in the skin, head, viscera and roe of the fish. While it will not majorly affect Big Sal, it will affect you if you eat her. Shortly put, Ciguatoxin plays havok with your sodium channels in the nervous system which leads to paralysis, heart contraction, and altering your hot and cold senses as well as your hearing. But, the positive to ciguatera poisoning (if there is one), is that the toxins wont cross your blood brain barrier, thus will just effect your peripheral nervous system. Contrary to popular believe, ciguatera cannot be destroyed by cooking and there is no effective treatment or antidote for ciguatera poisoning.
Video of Big Sal So, for all you fish lovers (in the food sense), just dont eat Big Sal (or the other 400 reef fish species known to contain ciguatoxins) and you’ll be fine. Have a look at the below video I chopped together for my friend Shawty, as it was her first dive at Julian Rocks. Big Sal makes a quick appearance (I was too busy filming sweetlips and unfortunately just got the tail end of her passing by)