New Eggs from ‘Alien Elders’

By Nigella Hillgarth, executive director

The wolf-eels at Birch Aquarium at Scripps laid eggs this month! This is an unusual and exciting occurrence by a really remarkable fish.

We kept the eggs on display with their parents for a few weeks but have since taken them away for safekeeping. The eggs are behind the scenes, under the care of our world-class aquarists. Check out the photos of the eggs under a microscope, taken at four weeks. Even at this early stage you can see signs of development, especially their huge eyes.

A bundle of wolf-eel eggs, each measuring about 1/4-inch in diameter.

A wolf-eel egg at four weeks shows signs of development, especially huge eyes.

This is the first spawning by this particular pair of wolf eels, which came to us in 2009 from the Oregon Coast Aquarium. These eggs are the third batch of wolf-eel eggs laid at Birch Aquarium at Scripps since we opened in 1992.

Wolf-eels (Anarrhichthys ocellatus) look rather like true eels in shape, with long grey bodies and big black spots. These eel-like fish have big heads with large jaws and teeth  – engagingly ugly animals that have been compared to “alien elders.” This is a wonderfully apt description! Wolf-eels can grow several feet long, and they have powerful jaws that give them an amazing ability to crush their prey. Their strong teeth and mouths can withstand the spines of large sea urchins and the shells of crabs and snails.

These animals are found in the Pacific Ocean from Japan to Alaska and all the way down to Southern California. They are found in sub-tidal areas of the cold Pacific Northwest, but can live up to 700 feet deep in warmer waters. The juveniles live close to the surface in the pelagic zone, forming part of the zooplankton for approximately their first two years of life. As wolf-eels grow bigger, they look for nooks and crevices to inhabit on the bottom of the ocean.

By four years of age, wolf-eels find a partner and are thought to mate for life. They are mature enough to breed at about seven years. The female lays several thousand eggs and wraps her body around them to form an almost translucent mass that is bigger than a baseball. The wolf-eel couple guards the eggs fiercely. After about three months, the eggs hatch and start their life independent of their parents in the open ocean.

For the next several weeks, our aquarists will care for the eggs, replicating ideal conditions in the wild as closely as possible. Even so, not much is known about raising baby wolf-eels. Any eggs that hatch will be kept on site or distributed to other public aquariums for display. We will post an update soon!

The female wolf eel wraps herself protectively around the mass of eggs.

The wolf-eel parents fiercely protect their eggs.

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Scripps Institution of Oceanography UC San Diego