Fish That Lay Fish

Although sharks and some other fishes give birth to well-developed, live young, surfperches have taken it the furthest.

Unlike most fishes, surfperches give birth to live young. The embryos develop fully within the mother, gleaning nutrients and oxygen from her body, much like a human fetus does. The developing young suck in nutrients from the ovarian fluid with a modified gill. They also develop large, thin fins covered with capillaries which absorb oxygen from this fluid.

A large surfperch bearing her young, born both tailfirst and headfirst.
Photo: Jerry W. Gerard

 


 

A pregnant surfperch opened after death by disease to show adult young.
Photo: CAS Archive

As with other live-bearers, very few young are born, but few die before they are themselves able to reproduce. While many fishes may lay hundreds or, in the case of cod, millions of eggs, most surfperches give birth to three to ten very well-developed young. In fact, most males in the family are born sexually mature, capable of fertilizing females at birth.

Most surfperches are found only in the Pacific Ocean off North America. Only 6 of the 23 species live mainly in the surf-the others range from deeper waters off the continental shelf to tidepools.

An intact ovary, almost fully developed, from a black surfperch. At this time the embryos are easily seen through the ovarian tissue, tightly compacted together.
Photo: Jerry W. Gerard