These starfish face destruction. Scientists help their spouse.

Over the past decade, the sunflower starfish has gone from a powerful predator on the Pacific Ocean floor to extinction. The Nature Conservancy estimates that 5.75 billion sunflower starfish died in three years, a 94 percent global decline.

The cause, scientists say, is mainly climate change and warming waters, which have caused what they now call starfish wasting disease. Scientists are scrambling to figure out how to bring these creatures, whose 24 limbs can stretch out up to four feet, back from the brink.

Hope is slowly on the horizon.

The Scripps Institution of Oceanography’s Birch Aquarium near San Diego successfully hatched three sunflower starfish earlier this month, the latest success story in a collaborative effort between the institutions to help the starfish reproduce and eventually return them to the wild.

There’s a lot of opportunity for good genetic diversity when all of our different facilities work together, said Melissa Torres, the Birch Aquarium aquarist who directs the program.

Despite their charismatic nature, Ms. Torres said, sunflower starfish move quickly and decisively through kelp forests, feeding on sea urchins and other invertebrates that feed on kelp beds. But starting in 2013, sea stars began dying by the millions along the Pacific coast from Mexico to Alaska. That was the same year that parts of the Pacific Ocean warmed unusually as part of a wider marine heat wave called the Blob.

The starfish began to develop white lesions on their limbs that would dissolve the surrounding flesh and eventually lead to their death. Scientists found that the disease affected many species of starfish, but particularly damaged the sunflower starfish. In California and Oregon, the species is considered functionally extinct, meaning that the population has declined to the point that it no longer serves an ecological role or function.

Last March, federal officials recommended that sunflower sea stars should be protected under the Endangered Species Act.

Without enough sunflower sea stars, the urchins have destroyed nearly all of California’s kelp forests, which marine biologists call the lungs of the ocean.

Meanwhile, researchers at several zoos and aquariums in the United States are working furiously to restore the population, led in part by the Aquarium of the Pacific in Long Beach, California, and the Henry Doorly Zoo and Aquarium in Omaha.

Birch Aquarium, located at the University of California, San Diego, has five sunflower stars, one of the largest populations of sunflower starfish in captivity in California. But until recently, they didn’t know which were female or male. To determine sex, researchers induced spawning.

In the wild, starfish broadcast in the water, males freely releasing sperm and females freely releasing eggs, where they mix and, hopefully, spontaneously fertilize. In the aquarium, the researchers injected hormones into the legs of three sunflower stars, about 50 inches in diameter, and waited.

After a few hours, the starfish began to rise from their flat position in what the researchers described as a yoga-like downward dog pose. Eggs and sperm began to emerge slowly, and the researchers carefully collected them with glass pipettes. The genetic material was then immediately cryogenically frozen.

Ms Torres said further testing was needed to see if the offspring could survive disease or parasites. Once this is determined, the aquarium will be able to begin the fertilization process. And since the aquarium now knows the gender of all their sunflower starfish, they can mate them accordingly or even share starfish in aquariums for breeding purposes.

He said the aquarium is excited to be able to pass these genetics on to anyone else who doesn’t have the population size they need or the ability to get these genetics.

Creating multiple generations of sunflower starfish is the ultimate goal that has been successful at Friday Harbor Laboratories in the San Juan Islands. It took three years for juvenile sunflower sea stars in the lab to mature enough, but last February researchers helped the starfish complete their full life cycle.

Jason Hodin, a marine biologist who directs the Friday Harbor sunflower sea star project, described the success at Birch as quite a breakthrough.

Now, Dr. Hodin shares with Birch his secret to success, or what he calls our cookbook for raising starfish.

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