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Male fishes usually have paired testes that produce sperm. Females usually have paired ovaries that produce eggs.

Internal - Dissection of an Eastern Blue-spotted Flathead

The fish is a male Bluespotted Flathead. The two long pale organs are the testes, the male gonads. The deep red strips of tissue either side of the backbone are the kidneys.

Image: Mark McGrouther
© Australian Museum

The method by which the eggs and sperm meet varies widely among fishes. Many species are broadcast spawners, shedding their eggs and sperm into the water to fertilise external to the body. Others such as sharks and rays have internal fertilisation where the sperm are released into the body of the female.