Milt is the sperm and gonads of male fish, and although it is not white in all fish, it is sometimes called white roe because it is the male counterpart to the female roe. The milt from codfish is also called curl because it has a curly shape. In flatfish, salmon, and herring, for example, the milt is smoother. The volume of the fully developed sperm sac can be almost as large as the roe sac in the female. However, unlike fish eggs, sperm cells are microscopically small, about 10,000 times smaller. More than 10,000 sperm cells are often released for each fish egg during fertilization in the water. As an example, a large salmon can contain up to half a liter of milt.