Biologists Rescue Unborn Baby Sharks at Fish Markets

November 9, 2021
Nature
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Image Source: https://www.smithsonianmag.com/

It’s 3:00 a.m. on the island of Malta, and in the stillness before most residents wake to begin their day, a shark is about to give birth. This is especially strange, not just because it’s happening on land, but because the shark in question is dead.

Surrounded by vendors preparing for the start of their day at the wholesale fish market in Valletta, Greg Nowell carefully runs his fingers along the belly of the shark: a small-spotted catshark, a compact, slender creature only half a meter long, with cream-colored skin covered in a galaxy of black dots. Where the shark’s skin is thin around its internal organs and womb, Nowell presses inward with a finger and feels something rigid and hard. He pushes, gently, encouraging the object back toward the cloaca, the opening shared by the shark’s intestinal, urinary, and reproductive tracts. With a gentle pop, it emerges: a tiny egg case, no longer than Nowell’s pinkie finger, yellowish-brown in color and—though it might not look it—likely still thrumming quietly with life.

Nowell will do this for dozens more sharks before the morning is through. As vendors begin scaling bream and filleting grouper around him, he’ll move between plastic totes, each stacked several layers deep with sharks packed in ice, identifying females and feeling for their eggs. Each egg that he finds is dropped carefully into a container of salt water for transport back to his office. There, Nowell and the team at the organization that he founded, Sharklab-Malta, will try to give each unborn shark another shot at living.

Sharklab-Malta is one of at least three groups around the Mediterranean taking on the unlikely role of nursemaid to several species of sharks and their close relatives, skates. By collecting and raising babies from females that wind up in fishing nets—most often as by-catch—and then on fishmongers’ counters, the groups hope to make a small difference in a world that has not been kind to sharks.

The International Union for Conservation of Nature (IUCN) estimates that more than a third of the 1,147 shark, ray, and skate species in the world’s oceans face extinction. In a widely covered paper published earlier this year, researchers found that oceanic sharks and rays have declined by 71 percent in just the last half-century, primarily due to overfishing—both intentional fishing and unintentional capture by nets and hooks meant for others.

Before the sun’s first rays touch the tips of the palm trees and set the Mediterranean glittering, Nowell will leave the fish market with a handful of new egg cases sloshing in his care. The babies that emerge from them will play two roles: first, they will serve as ambassadors for their kind, teaching kids and adults to see sharks as fascinating, vital, and, hopefully, worth protecting. Second, they will act as guinea pigs, helping refine standardized procedures for raising babies like them. Nearly a decade after Nowell began the first experiments on market-collected egg cases, the scientists working with these eggs hope these methods are ready to be adopted for other species of sharks and skates.

Luckily, an estimated 30 to 40 percent of sharks and all skate species are oviparous: males fertilize the eggs internally, then females unload each growing embryo on the ocean floor enclosed in an egg case. This leathery pouch serves as a little external womb, packed with nutritious yolk that feeds the young shark as it grows.

This strategy is common enough in the shark family that egg cases are frequently found tossed up on beaches, hooked into tangles of seaweed. They’re most often dark brown or black, like an overstuffed leather wallet with a spindly, curling leg on each corner. (Or, in a COVID-19-era analogy: they look a bit like a face mask.) These egg cases are known to beachcombers in North America and Western Europe by the colorful name of “devil’s purse,” or in a less superstitious turn, “mermaid’s purse.”

The egg-case approach is also common enough that the scientists involved hope techniques from the Mediterranean could help species facing a much greater risk of extinction, unlike the relatively abundant small-spotted catshark.

“Some people ask, ‘If you’re taking these eggs and recovering sharks, are you saving the population?’ And we’re not,” Nowell says. “If we can put two back for every one [fished], fantastic. But ultimately what this whole process enabled us to do was look at a methodology, and develop a method that can be used anywhere in the world.”

Read More: https://www.smithsonianmag.com/innovation/biologists-rescue-unborn-baby-sharks-at-fish-markets-180978822/

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