Weight estimate

[Titahi brown]

I have a mate from Florida staying with me who is as keen as I am, we got out on Thursday and his first cast saw a small 5 kilo GT landed on his first cast, from there the day only got better with Queenfish coral trout and GT's falling victim to his shell shaping Glanz lure.  having never caught a GT prior to this he was wrapped as the day progressed.
 We moved about during the day exploring spots and both learning alot. The last fish of the day, shadowed his lure back to the boat where Dave left the lure sitting boatside as I had told him to do, when his rod doubled over.......  we dragged the fish to deeper water, the fight was short but brutle. The fish went 1 meter 70mm and was in good nick.











I was hoping someone with a bit more experience could give us a weight estimate based on the photos and length?


Cheers

[Felix Neuer]

I would guess around the 20-25 kilo mark.
it is always hard to guess from a picture, as some fish have a massive body, others are slim.

anyway a nice fish, congrats!

[Titahi brown]

Thanks felix for the response, we guestimated similarly.

Is there a formula for length x girth =weight ?

[Mark Harris]

A commonly used formula is fork length x fork length x girth x 2.75/1000000

It gives an approximate indication, nothing more than that.

[Titahi brown]

Thank you Mark, an estimation is a better option than a sling and suitable  50kg scale...

[Trevor Skinner]

Titahi,

I have an excel spreadsheet that was put together by the South African fisheries people. It's based on an African sample so won't be exact but it gives you some idea. It's not one of those silly 'fish weight calculators' either. The spreadsheet defines the parameters of the sample used in the formula. It covers most of the tropical and sub-tropical species that we typically fish for.

I'm off fishing for a few days from tomorrow but I'll send it to you early next week if that's OK.

Regards,


Trevor   

[Trevor Skinner]

Amr,

Not at home at the monent and fishing this weekend. Will post it when I get back.

Regards,


Trevor

[Cameron Mundy]

It's an excel spreadsheet not sure if you can post it on the forum it gives a 107cm GT a weight of 23,9 kilos hope this helps

[Titahi brown]

Thank you Trevor, much appreciated. Good luck for the weekend

[Mark Harris]

Is a calculation which uses length without girth for a fish that varies as much as a GT really of any use?

Some GTs are almost round and others long and skinny.

[Trevor Skinner]

Mark,

I think it is useful.

The length/weight relationship may vary considerably from fish to fish but provided the sample that determines the formula is large enough the degree of error is acceptable, at least in my opinion. What you have to avoid is saying that a 137cm fish unequivocally weighs 50kgs.

If you want to say that, you need to actually weigh the fish with a certified set of scales. Anything else is really only still an estimate which will have its own associated degree of error.

However, what you can say is that the fish probably weighs somewhere near 50kg give or take and, for me at least, that's good enough. I'm not pushing for records other than the goals I personally set for myself.


Just my take on it.


Trevor

[Mark Harris]

Yep fair enough for personal goals Trevor.  As long as folks do not start thinking that a certain length = a weight.

[Titahi brown]

Appreciate the responses guys, thanks. Mark I think only weight = actual weight a belly full of fusillers could make a difference. I dont envisage catching a record fish where I fish, but do hope to keep improving my PB.

 I am concious of getting fish back into the water in good nick, and without the benefit of a large volume washdown pump to prime the fish with water, measuring quickly before a photo seems like an easy option?

[Ali Saadi]

looks like 21-22 Kilos