Ok, Thx to you my 2 Arowana are currently going through a gender identification crisis -- or rather I am (most assuredly they already know
).
But kudos on taking the time to write and publish a book regarding one of the more mysterious aspects of Asian Arowana keeping.
Actually I'm not at all interested in breeding my Aros even if they were opposite sex, it's more just curiosity/personal convenience. But I checked out your book on Amazon (though I don't use Amazon so I'm sorry I can't buy it), and could see your main points and quite interesting info by clicking on the photos.
But getting back to my first point, if I correctly understand your criteria, it's possible that I've mis-guessed the gender of one or maybe both of my Aros (both from Malaysian farms): a GHXB that I guessed/kinda felt was male, and a BBXB that I have been guessing is a female. I've had them since last Dec & Jan, when they both were about 10-10.5".
Of course I'm fully open to the possibility I've been wrong with 1 or both, so would appreciate your opinion on their gender. Here are some pix of them taken with the last few hours: