Topwater Caranx Ignobilis: Giant Trevally (GT) > Reports & Expeditions

Black GTs are like London Buses...

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Mark Harris:
Very interesting Andy and well dug out.

In summary, that is saying that sexual predictions based on colour were correct in 90% of cases in the East African population surveyed.  And in the mature examples, (70 cm or longer) close to 100% correct.

That is pretty strong evidence at least for that particular population.

Ed Nicholas:
Sick picture man.

Loving the detective research Mr Rowe. Thats exactly the sort of survey that we need more of but look at the date .. 1957!! Guys were doing more then than we are now, crazy.

Andy Rowe:
Men, thats only a snippet of the original paper, the abstract i think. The original you can pay for in Nature magazine if anyone is really keen but i think that distills the main point. There is more info on the net. The same question came up a some years back on this forum and i remember reading one paper from a study in Hawaii which claimed capture of a hybrid giant and bluefin trevally!!

 I still think the males have the ability to go from dark grey on top to really dark (black) when they are stressed, angry or in mating mode. In places like hawaii and the marquesas where the background structure is dominantly dark basalts; a silver fish in ambush would stick out like you know what; so perhaps in these localities the females also have the ability to pigment dark. This theory is just based on observation and a rudimentary understanding of fish biology though.

John Cahill:
The black ones I have seen have all been milting so they must be males that are 'ready to go' in my humble opinion! :o

John Cahill:

--- Quote from: Mark Harris on June 09, 2013, 07:25:43 PM ---The harry monk all over my shirt in this pic has absolutely nothing to do with me though.



--- End quote ---

hehehehe ;D

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