Cephalopodcast

Eggcase from a skate. © J. Robertshaw

The Great Eggcase Hunt

With the coming of spring in the northern hemisphere also comes a time to hunt for eggs. But it’s not just about birds anymore. The folks over at the Shark Trust also want people to head to the beach to look out for the fecundity of fish.

Colloquially known as mermaid’s purses, eggcases are the protective capsules laid by skates and some rays**. Inside is a tiny baby skate and a big yolk sac. Typically the capsules have odd keels and horns to help them remain tangled in seaweed and camouflaged on the bottom. The young develop for several months before hatching out as miniature adults. But after hatching, the horny cases begin to breakdown and may come loose, washing up on the shore. Storms might also dislodge living ones from the bottom. If you find a lot of eggcases in an area, it may indicate that a skate nursery is located nearby. This kind of information is valuable to conservationist who are trying to protect these species.

Why does the Shark Trust want you to record eggcases? In recent decades several species of skate and ray around the…coast have dramatically declined in numbers…The identification of these critical areas will enable the Shark Trust to propose conservation measures, in order to reverse the decline of these charismatic animals.

So now’s your chance to contribute to skate and ray conservation and have a lot of fun at the same time.

They have a lot of resources for citizen scientists and for educators who want to organize a local eggcase hunt. And if you don’t live near the coast, you can still take some time this spring to create your own giant eggcases (PDF link) out of balloons and papier-mâché. Or better yet, make some chocolate ones that you can send to me!

• Great Eggcase Hunt
• A Fieldguide to Eggcases (PDF)
• **What’s the difference between a skate and a ray?

Rabbitfish Helping to Save the Reef

Continuing with my aquatic version of things vernal, there is news that rabbitfish might be helping to save the Great Barrier Reef. Many herbivorous reef fish species like parrotfish and tangs regularly graze on the fast-growing algae of the reefs. But apparently they only like to eat it when it’s young and not too weedy. This is where the rabbitfish comes in.

“Then, to our even greater surprise a fish we had never seen in this area before was observed grazing on the weed. The rabbitfish (Siganus canaliculatus), came out of nowhere and began to clear-fell the weed placed on the reef crest.”

The rabbitfish were caught on underwater videocams, in schools of up to 15 fish, grazing the crest, slopes and outer flats of the reef, and chomping away at more than ten times the rate of other weed-eaters.

• Red Orbit: Rabbitfish Helping to Save the Great Barrier Reef
• Science Daily: Rabbit Fish To The Rescue Of The Reef

sƎʇɐʞs ɹƎɥ :ɐ*