Coral sea region billfish atlas

Sexing Billfish

Small (immature) fish

Male
Gonads thin and straplike
Female
Gonads short and triangular to rounded

Male: The testes can be very indistinct to the novice, but inspection of tissue lateral to and pressed against the intestine will reveal pale, pinkish organs. They continue from the vent forward to the level of the spleen.

Female: The ovaries do not extend as far forward as the testes and are obvious as 3-dimensional organs originating at the vent alongside the intestine.

Large (mature) fish

Male
Gonads with distinctive segmented appearance
Female
Gonads with uniform appearance

The most critical test is to cleanly sever the gonad and probe for the lumen (hole) through the centre along its length. The lumen will only be obvious in females. Also, the cross section will be uniform in appearance and of granular texture in females. When cut, mature male testes will exude white milt.

Note: Both testes and ovaries (gonads) are paired - one on the left and one on the right.

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Last updated - 22 August 98

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