We tend to think of fish as dead-eyed, cold-blooded creatures without much compassion. But with Father’s Day still fresh in mind, there’s at least one piscine species whose dads are deserving of respect: the three-spined stickleback. Not only does the male of this species build nests and care for the fertilized eggs, but sticklebacks are also rapidly adapting to a changing climate to keep their broods safe.
Sticklebacks—not to be confused with picklebacks—are two-inch bottom feeders that live throughout the Northern Hemisphere. Most species prefer slow-moving water, where the males make nests by gluing algae, sand, and other debris together with a protein substance produced in their kidneys. (The glue is called “spiggin” after the Swedish word for the animal, “spigg.”) Once the nest is complete, males woo mates with a zig-zag dance only a stickleback in heat could love.
If a female consents, he ushers her into the nest, where she lays between 40 and 300 eggs, all while the male pecks at her from behind to stimulate ovulation. (We said they were great dads, not necessarily great lovers.) As soon as she’s finished, the male darts into the nest to fertilize the eggs, then back out again to chase the female away. (The creature named for the pointy fins running down his spine isn’t a cuddler either.) Now a single-dad-to-be, the male guards his nest from other sticklebacks, predators, and erosion until the eggs hatch. He even fans the eggs to keep them oxygenated, which is the stickleback version of going to the store at 3 a.m. to pick up pepperoni rolls and lemon sherbet.
Constant guard duty and oxygen detail is a tall order, but male sticklebacks might soon have to deal with a bigger worry: climate change. Those family-friendly, slow-moving rivers and streams could speed up throughout much of the fish’s habitat, thanks to rising water levels, increased rainfall, and large-scale flooding. Last week, FEMA reported that over the next century, areas in the United States at risk of flooding will surge by 45 percent. Across the pond, Europe is still mopping up after weeks of record floods. All of this is bad news if you’re an animal that makes its home on a riverbed and your building material of choice is the consistency of muck.
But like I said, sticklebacks aren’t your ordinary dad. When the waters get rough, the fish get glueing.
“They need to put more glue into their nests to make them stronger,” says biologist Iain Barber of the University of Leicester. “Sticklebacks appear to be very well adapted to cope with changes in their environment —and can change their nests and nesting habits depending on the water flow levels.”
Barber warns, however, that producing spiggin requires a lot of the father's energy and making more of the sticky stuff could impinge on his ability to raise multiple broods. Even so, the research suggests sticklebacks are up to the task.
So far, the daddy dynamos appear to be standing up to increased water flow both in the lab and in the wild. The fish’s ability to adapt may be why several variations of the species exist in diverse habitats across the planet. Originally a saltwater fish, many sticklebacks became trapped inland about 10,000 years ago at the end of the last ice age. Now many species—including the three-spined stickleback—thrive in freshwater.
Unfortunately, such adaptability will unlikely be the norm for many species as the Earth’s climate changes. California, for instance, may lose 82 percent of its native fish. And fish aren’t alone, of course. Polar bears, pandas, right whales, sea turtles, orangutans, and many plant species face similar fates.
This may be the first and the last time you hear about the three-spined stickleback, but while human dads are out this week returning ugly ties, this little fish will be raising hundreds of kids in the face of a global environmental crisis—with spiggin as his only weapon.
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