Tamar Snapper Research
About 18 months ago Simon Conron of Victorian Marine and Freshwater Resources Institute asked if I would be interested in filling out a fishing diary for him so they could gain some information on Tasmanian snapper. Over a period of time we have learnt quite a bit and also have gained some valuable knowledge on this precious fish.
Ageing and growth rates
The last two and a half seasons I have been sending snapper otolith (ear bones) to the institute where they can gain valuable information on growth rates, aging and also distribution. I suffered some setbacks extracting otoliths, and unfortunately, my wife threw out a set from a 10.6 kg snapper. I would have loved to find out how old he was.
I sought the help from two of my fishing mates to help me extract the otolith. Francisco Nieria or Pancho as he is better known is a recognized marine biologist at the A.M.C. and Sean Brodie a Victorian Fisheries Officer and snapper and mulloway expert. Both Sean and Pancho showed me two different methods of extracting them .I mastered Sean's technique the quickest, but I was lucky enough to get a first hand lab demonstration from both of my fishy mates.
After breaking several sets of smaller fish I managed to send over around 15 sets of snapper otolith to Simon and Sean .The fish where of mixed sizes between 700 gms to 11.5 kg. Out of all the otoliths I have sent I have only received information back on around five sets. I found the information to be very interesting and this is what I found out.
4 kg = 7 years, 4.2 kg = 7 years, 6.5 kg = 16 years, 8.75 kg = 20 years, 10.3 kg = 26 years and 11.5 kg = 27 years. These were some of the larger ones that I had sent over. Some of the smaller fish have not been aged as yet. As you can see the growth rate is very slow. The otolith is not only used for ageing and growth, but they also contain a chemical DNA signature called Beriam. This can enable scientist to locate where fish have been spawned. Snapper in each state have a different DNA signature inside their otolith. It was interesting to find out that the otolith that I sent to Victoria had no matching chemical signature on file at the institute. This probably means Tasmania's snapper stocks are not linked to that of Victorian fish, but more research needs to be done to confirm this.
In all the textbooks I could find it states that snapper normally spawn in water surface temperatures higher than 18 degrees. I found this to be hard to believe after catching several big fish over 20 pounds in water temperatures less than 15 degrees which have been full of spawn and roe. My theory was more reinforced when Sean spent a week fishing with me in the Tamar late in the season. Apart from having a holiday he desperately wanted to catch a Tassie snapper. After a full weeks fishing to no avail, the second last night that we fished Sean's rod buckled over out of the blue and his dream came true, an 8.75 kg fish. Apart from being over the moon we both gained some valuable information out of the fish. The snapper was a big female and was in spawn. A sample of the eggs were put in alcohol and sent back to Victoria for examination. The egg expert found the fish was about two weeks off spawning and the water temperature was well below the 18 degree mark. Maybe Tasmanian snapper have adapted to the colder water temperature for spawning.
Tag and Release
Half way through this season Simon also issued me with some Vic tags. Out of the ten fish that I caught this season five fish were released and four had tags in them. I was once a fisherman that when I caught a snapper I would kill it and take it home to eat, but after learning how slow that they grow and knowing that the Tamar numbers aren't as prolific as other places I now get just as much enjoyment out of letting the odd one go with a tag in them. I have a hope that one day one of my boys will catch one of the tagged fish. If by chance someone does catch one of the tagged fish I would appreciate it if you could please give me a ring or come and see me at Charltons fishing.
I have also been filling out a detailed diary which tells researches where I caught the fish, the time of day, type of bait used, how many rods that I use, hook style and size, depth of water, fork length and quantity. This enables researches to get a better picture of the Tamar estuary and all the population of snapper it may hold at certain times of the year. Hopefully next year I can write another article and tell you more about the findings of the Tamar snapper. I feel honoured to have been given the opportunity to be involved in the first research done on Tassie snapper.
Tight lines, Damon Sheriff.