It should be fish liver, not gonad. The fish liver is dark red and huge. In fish with mature gonads, the ovary has developed greatly, accounting for about 2/3 of the whole abdominal cavity, and its branch vessels can also be clearly seen. Eggs are prominent, round, easy to separate from each other, and sometimes a small number of translucent eggs can be seen. The ovary is orange or orange-red. When pressed lightly, no mature eggs flow out from the belly of the fish. Testicles are also obviously enlarged and white.