The sexes are separate and generally occur in about equal numbers.

Most sharks and rays bear their young alive in an advanced stage of development after an embryonic period of six to 12 months. The skates and elephant fish, however, lay relatively few large eggs in horny capsules, depositing them on the sea floor.

The vast majority of bony fish shed several thousand very small transparent eggs, which float in the upper layers of the sea. Some species produce fewer eggs, which are attached to seaweed or rocks, etc. Spawning usually occurs in spring or summer, sometimes during the autumn. Hatching takes place within a few days, the incubation period depending on the temperature. The tiny larvae in their first few days live on their store of yolk, but when this supply is depleted they begin feeding on small planktonic organisms. At this early stage they are entirely planktonic and may be widely dispersed by means of currents.

by Lawrence James Paul, B.SC., Fisheries Division, Marine Department, Wellington.

• New Zealand Sea Anglers' Guide, Doogue, R. B., Moreland, J. M., Heath, E. W. (1961)
• A Treasury of New Zealand Fishes, Graham, D. H. (1956)
• Sea Angler's Fishes of New Zealand, Parrott, A. W. (1957)
• The Queer and Rare Fishes of New Zealand, Parrott, A. W. (1960).