Studying southern blue fin tuna

Catching tuna in a net is challenging but it ensured the fish was well looked after during the landing process
Jarrod Day
So I took my own advice from last week and did do the 'drop everything and go' too head down to Portland in search of southern bluefin tuna. Though I did jump on board Reel Time Fishing Charters with Matt Boultin, the day was more about research than catching and getting a feed, which I would have liked mind you.

Still, on boarding the boat, I was met by Matt and deckhands, Aleks and Katie. Also on board were local angler Scott Gray whom works part time for the Victorian Department of Primary Industries and two other gentlemen, Sean Tracey and Klaas Hartmann that work for the Institute for Marine and Antarctic Studies (IMAS).

The project undertaken was led by IMAS and funded by the Fisheries Research and Development Corporation, the Victorian Recreational fishing trust, the Tasmanian Fishwise Community Grant Scheme and the NSW recreational fishing trust.

Once on the boat, a blood sample was taken immediately.
Jarrod Day

The study of Southern blue fin tuna is forever ongoing and on this day amongst a plethora of tests being conducted the main study is to understand the post-release survival of southern blue fin tuna from recreational fishing. Basically if a southern blue fun tuna is caught and then released, does it survive?

Through Sean, Klaas and Scott’s study they can tell if the fish has survived by the behaviour of the fish which is recorded by the Sat tag. Specifically, the tag records the water temperature and the depth the fish is at every few minutes. If the fish dies, as an example, they might see the fish sink to the sea floor from the transmitted data. If this happens the tag will release from the fish, float to the surface and transmit its data to satellites which then gets sent to a computer. If the fish survives they would expect to see a normal, diurnal dive pattern for the period the tag stays on the fish – which in the case of the fish we tagged is 180 days.



The P Sat Tag was then inserted into the back of the fish.
Jarrod Day

The other thing being looked at is how stressed a southern blue fin tuna gets during a fight. To do this they take blood samples and measure lactate, cortisol and glucose levels. The thought is the longer the fight time the more stressed the fish will be. The obvious question is then are they stressed to a point that effects their survival. By combining the tagging results with the blood results they will hopefully get an answer to this.




Although this study is not focused on the movement of southern blue fin tuna, the tags provide info on the approximate movement of each fish we tag. That way, they can see where the fish go after they are tagged, particularly how they move around Australia and into the Indian Ocean and Tasman Sea, etc, rather than small scale daily movements.

Gently releasing the fish after the tagging process.
Jarrod Day

With this study and more being conducted, the research and results will provide us with information that is currently not known about southern blue fin tuna. While little is currently known about southern blue fin, having the ability to do such research thanks to the funding from Fisheries Research and Development Corporation, the Victorian Recreational fishing trust, the Tasmanian Fishwise Community Grant Scheme and the NSW recreational fishing trust will open up a whole new element to what these blue water speedsters are up to.

IMAGE JARROD TO GO UNDER JARROD'S INTRODUCTION
Jarrod Day

This week I hit the local coastline around Western Port in search of yellow eye mullet. For some, Mullet are a tasty fish and being one of the highest in omega 3 oils, on the plate they are favored. For myself, they make a great bait but what ever your preference, mullet are easy to catch and can be a lot of fun on light tackle right around the coast.

IMAGE GARY TO GO UNDER GARY'S INTRODUCTION
Jarrod Day

Gary Brown goes back to basics and looks at the advantages of using a running sinker rig in fast current locations. Gary explains how to tie the rig correctly along with its advantages over other rigs.


While Lee Brake has returned from FNQ, he takes the time to look at a relatively new fishing technique using Vibe lures. Vibes have a huge advantage over other lures styles and Lee looks at why using vibe lures is so effective.

Until next week, see you on the water,
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