| There are two ways to discover a deep-sea, glow-in-the-dark shark new to science. If you're Bill Murray in the 2004 film "The Life Aquatic," you cram a ragtag crew of filmmakers and musicians into a World War II submarine. You pilot it deep into the abyss where suddenly a glowing, bus-sized mystical 'jaguar shark,' who supposedly ate your best friend, swims slowly overhead. You are awed by the shark's majesty, while a Brazilian rock star croons in the background. You vow to not destroy the sea beast, partially for its beauty. If you're anyone else, you stumble upon a dead shark after it's been dragged up in a net. Scientists do pilot submersibles, like Murray in "The Life Aquatic," but they are pricey and time-limiting. Unlike Hollywood, real discoveries of so-called 'glow-in-the-dark' sharks more often occur when scientists scour exotic fish markets or use deep-sea fishing gear themselves. Some shark scientists now question whether overfishing is driving a recent uptick in glowing, sharp-toothed discoveries from the deep. Monday brought the latest species discovery. Federal biologist Mark Grace and his co-authors described a new shark species in the journal Biotaxa. The fish, dubbed the American pocket shark (Mollisquama mississippiensis), makes its own light and is shorter than the average pencil. The team accidentally caught and killed the pocket shark in a fishing net while investigating the diet of deep-diving sperm whales. The discovery made national headlines. Newsweek called the shark "adorable." Smithsonian magazine said it looked "like a tiny sperm whale." Almost all headlines used "glow-in-the-dark" to attract readers. The shark's anatomy has two bioluminescent features — skin that emits light and a gland that likely spews a brilliant cloud of light. To scientists, the shark's glow was the least exciting part. "Finding a new bioluminescent shark is not particularly notable," said Matt Davies of Saint Cloud State University, who researches bioluminescence but was not involved in the study. Some scientists believe that 75 percent of fish in deep water are bioluminescent. Davies estimates that 10 percent of all shark species produce their own light in some way, including almost all sharks from the families Etmopteridae and Dalatiidae — the deep-water dwellers. Species discoveries of glowing sharks seems to be happening "every two or three years," according to Davies. A new lanternshark species made headlines in 2017. Two year earlier, a 'ninja lanternshark' made waves across social media. Almost all new discoveries come from dead specimens. One scientist, David Ebert, has built a 30-year career visiting fish markets in places such as Taiwan, Zanzibar and Sri Lanka looking for dead sharks. He has described 40 new species of sharks and chimeras, known as ghost sharks, by collecting carcasses accidentally caught by people fishing deeper and deeper each year to land profitable catches. Twenty years ago, deep-sea sharks didn't commonly show up in nets and market tables as accidental catch. Deep water fisheries weren't as common as they are today. "Some fish markets in Asia... I've been going to for 30 years," said Ebert. "The fishermen tell me they are fishing deeper." Many scientists question the value of collection-based discoveries, like that of the American pocket shark. Not observing sharks' glowing behaviors directly means that scientists depend on inference. "We know [they emit light] from the anatomical structures," said Davies. There are many theories about why deep-dwelling sharks have these glowing body features. Mating and finding food at 700 miles underwater top the list. "[These federal scientists] catch this thing and kill it. They never actually saw this thing swimming — so they don't know jack about its biology," said David Gruber, a biologist not involved with the discovery. Gruber employs different kinds of cameras to observe bioluminescence directly, in action and at depth. He wants to see a future where scientific endeavors are no-kill and collection-free. He doesn't want to have to rely on overfished and exploited ocean habitats to gather shark knowledge. Unfortunately, that vision is still the stuff of Hollywood. | 
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