Delanceyplace: Why Sharks Matter

Today's encore selection -- from Why Sharks Matter by David Shiffman. Shark biodiversity and biogeography:
"According to the latest edition of the field guide Sharks of the World, there are 536 recognized species of sharks. They range in size from the dwarf lanternshark, which could fit in your hand, to the school bus­-sized whale shark. Many -- like the sandbar shark (#BestShark) -- have the particularly sharky shape you're familiar with from movies or from visiting your local aquarium, but some, like the angel shark, are flat and capable of burying themselves in the sand to wait for prey. Some deep­-sea weirdos like the frilled shark are almost snake-like in appearance and movement. Many are gray or brown in color; some are blue; some, like the goblin shark, can be bubblegum pink. Some sharks have beautifully elaborate patterns of stripes or spots. Some are sleek, like the shortfin mako shark, which is among the fastest animals in the world. Others, like the angular roughshark, have just about the least hydrodynamic shape I can imagine: they look like the ocean's overinflated footballs.

"Recognizable sharks have been swimming in the ocean for more than 400 million years. This means that the first shark was on Earth not only well before dinosaurs trod the land but before trees existed. Though we've lost many species over the eons, sharks as a group have survived every mass extinction event in Earth's history -- which makes the conservation challenges they've faced in the past 50 years all the more heartbreaking. While we're talking about ancient sharks, let me assure you that, no, the giant and ancient megalodon is not still alive. It is definitely super-duper extinct. People claiming otherwise are lying to you, for reasons that remain unclear to me despite a decade of refuting this really strange folk legend. I've received death threats from people who believe I am part of a global conspiracy to hide the truth about megalodon. Once I even interacted with someone online who emphat­ically made the bizarre and obviously false claim that she had seen the US government rounding up and killing megalodons -- and that she had barely escaped with her life once the shark-killing soldiers spotted her.

"Sharks' habitats are as diverse as the animals themselves. Some sharks are found on coral reefs, while others, like the Greenland shark, are found under Arctic ice. (Fun fact about Greenland sharks: they have been found with digested polar bear and reindeer meat in their stomachs. These are probably the remains of scavenging animals that drowned, but I enjoy imagining a polar bear getting slurped from below as it swims between ice floes.) Some sharks live in the open ocean, where they'll never see a hard surface their entire lives. Some sharks live in the deep sea, where it's so dark that sunlight never reaches. The megamouth shark, a deep-sea animal with the world's coolest scientific name -- Megachasma pelagios, which means 'the giant mouth of the deep' -- has bioluminescent gums that entice prey to swim right into its mouth.

"US Navy Seals jokingly say that you can test whether there are sharks nearby by dipping your finger in the water and tasting it -- if it's salty, there are probably sharks around. While technically accurate -- there are sharks just about everywhere there's ocean -- the implication is incom­plete, because there are also sharks that live in fresh water. No, I'm not just referring to the bull shark, which Discovery's Shark Week program­ming wrongly claims year after year is the only shark that can enter fresh water. I'm also talking about Glyphis sharks, sometimes known as river sharks, which live almost their entire lives in fresh water. Unfor­tunately, river sharks are some of the most critically endangered sharks in the world, in no small part because they live closer co humans than ocean-dwelling sharks do.

Speartooth shark (Glyphis glyphis) at the Melbourne Aquarium

"What we already know about shark biodiversity is amazing, but it's what we don't know yet that many attendees at my public talks find shocking. We are still discovering new species all the time. A new species of chondrichthyan fish is discovered about every two weeks. Some of them get tons of media attention, like a new species of 'walking shark,' so called because they can crawl on their fins out of water for shore peri­ods of time, or a new species of dogfish named after shark science legend Genie Clark (Genie's dogfish, Squalus clarkae). Others are little known outside of science nerd circles. There's plenty left to discover. (But no, that doesn't mean that megalodon is still hiding out there.)

"Unfortunately, the threats these species face are as diverse as their habitats and color patterns, which means that there's no one-size-fits-all solution. For instance, creating no-fishing zones is less helpful to a spe­cies that moves around a lot and spends limited time in protected areas. Nor is a ban on selling shark fins especially useful for the many species killed for reasons having nothing to do with their fins. Generally speak­ing, any solution to a complex worldwide conservation problem simple enough to fit on a bumper sticker is perhaps too simple to be helpful."

Why Sharks Matter: A Deep Dive with the World's Most Misunderstood Predator
author: David Shiffman  
title: Why Sharks Matter: A Deep Dive with the World's Most Misunderstood Predator  
publisher: Johns Hopkins University Press  
date: 2022 Johns Hopkins University Press  
page(s): 15-17