Episode 704: The Secret Sex Life of Fish

Fish are the most diverse group of vertebrates on the planet, ranging from the gigantic whale shark to the tinniest minnow. Because of their diversity, fish have evolved very varied reproductive strategies that aren’t widely known by the general public. Few people realize that some of these animals are capable of changing sex. Some fish species start their lives as females and later turn into males, others start as males and become females, while yet another group is comprised of simultaneous hermaphrodites, meaning they can spawn as both males and females. Discover the unique ways of how some fish species do this and why they likely evolved this way.

Experts

Meet the experts featured in this episode.

Episode Photos

Changing Seas

1 / 28

Bluehead Wrasse are a common sight on coral reefs in Florida, the Bahamas and Caribbean.

Changing Seas

2 / 28

Terminal phase Bluehead Wrasse are blueish-green in color, while females and initial phase males are predominantly yellow.

Changing Seas

3 / 28

John Godwin, Ph.D., together with his collaborators and students, studies Bluehead Wrasse on reefs in the Florida Keys.

Changing Seas

4 / 28

One of the study sites is near Carysfort Lighthouse off the coast of Key Largo, Florida.

Changing Seas

5 / 28

Terminal phase male Bluehead Wrasse pair-spawn with females.

Changing Seas

6 / 28

A female gravid with eggs.

Changing Seas

7 / 28

All terminal phase males begin their lives as either females or initial phase males.

Changing Seas

8 / 28

Initial phase males and females group-spawn together by rushing up into the water column.

Changing Seas

9 / 28

After releasing a “cloud” of eggs and sperm, the fish swim back down to the safety of the reef.

Changing Seas

10 / 28

Terminal phase males aggressively defend spawning territories from other terminal phase males and initial phase males who try to sneak in undetected among the females.

Changing Seas

11 / 28

Changing Seas Videographer Sean Hickey films John Godwin, Ph.D. as he preps to capture female Bluehead Wrasse for research.

Changing Seas

12 / 28

Once a terminal phase male disappears from its territory, the next largest female (or initial phase male) starts changing sex to replace the terminal phase male.

Changing Seas

13 / 28

Bluehead Wrasse aren't the only fish attracted to the bait placed in the net.

Changing Seas

14 / 28

To understand what happens in the body when females change sex, John Godwin, Ph.D. captures and tags females to re-capture them later after they’ve started changing sex.

Changing Seas

15 / 28

A tagged female Bluehead Wrasse on the reef.

Changing Seas

16 / 28

To induce sex change in the largest female, researchers remove terminal phase males from their spawning territory.

Changing Seas

17 / 28

This tagged female will be recaptured and examined after she has begun the process of sex change.

Changing Seas

18 / 28

Fish, which change sex from female to male, are known as protogynous (proto -first, gyno -female) hermaphrodites.

Changing Seas

19 / 28

It is fascinating and amusing to observe reef fish behavior in the wild.

Changing Seas

20 / 28

Felicia Coleman, Ph.D. and Chris Koenig, Ph.D. have spent large portions of their careers studying economically viable fish species such as grouper.

Changing Seas

21 / 28

Changing Seas Videographer Yoandy Vidal checks out the shot while Series Producer Alexa Elliott prepares to interview Chris Koenig, Ph.D. about his gag grouper research.

Changing Seas

22 / 28

Changing Seas producer Alexa Elliott interviews Felicia Coleman, Ph.D. about her gag grouper research while Production Assistant Monique Arenas works to adjust the lighting.

Changing Seas

23 / 28

ORA President Dustin Dorton (left) and ORA Production Manager Adam Heinrich (right) show Changing Seas Videographer Sean Hickey some of the species raised at the facility.

Changing Seas

24 / 28

A clownfish with a batch of eggs. Clownfish need a smooth surface to lay their eggs on.

Ned DeLoach

25 / 28

A mating pair of hamlets. Hamlets are simultaneous hermaphrodites.

Changing Seas

26 / 28

These clownfish raised by ORA are ready for their “forever home.”

Changing Seas

27 / 28

For some deep sea anglerfish species, the much smaller male permanently attaches to the female’s body. She provides him with sustenance while he provides her with sperm.

Changing Seas

28 / 28

A computer-generated image of a deep-sea anglerfish.

Special Thanks:

Fairfield Inn & Suites
by Marriott Ft. Pierce
6502 Metal Drive
Ft. Pierce, FL 34945
(772) 462-2900

Image Credits

Changing Seas would like to thank the following individuals and institutions who kindly allowed their footage, images and other media to be used in this production:

Anna DeLoach

Ned DeLoach

Grant Gilmore

Chris Koenig

NOAA’s Sustainable Seas Expedition, 2001

ORA

Bill Parks