'Burnt Hot Dog' sea cucumbers raise red flags for threatened global fisheries

http://www.eurekalert.org/pub_releases/2016-03/caos-hd032116.php

Public Release: 22-Mar-2016
'Burnt Hot Dog' sea cucumbers raise red flags for threatened global fisheries
Sea cucumbers -- the floppy cousins of starfish and sea urchins -- are particularly vulnerable to pollution and overfishing; scientists say this is bad news for ocean ecosystems worldwide
California Academy of Sciences

Holothuria edulis -- a type of slow-moving sea cucumber about the size of a classroom ruler -- boasts an important ocean role despite its uncanny resemblance to an overcooked sausage. This "Burnt Hot Dog" sea cucumber takes center stage in a new genetic study that digs into the animal's valued spot in marine ecosystems across Japan's Okinawa Island as well as its extreme vulnerability to environmental stress and overfishing. A team of researchers, including an expert from the California Academy of Sciences, says their study's findings are an urgent call for increased fisheries management and protections for ecologically important sea cucumbers, sometimes called the "vacuum cleaners of the ocean," worldwide. The study was recently published in the journal Conservation Genetics.

Sea cucumbers, the often-overlooked cousins of starfish and sea urchins, are soft-bodied marine invertebrates that appear in myriad sizes, shapes, and thrilling colors in every ocean on Earth. More than 1,500 species -- including pleasingly-named "Sea Apples," "Strawberries," and "Sea Pigs" -- inhabit global oceans from the shallows to the mysterious deep seafloor.

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"It's easy to underestimate the sea cucumber," says Dr. Iria Fernandez-Silva, an Academy postdoctoral research fellow. "Sea cucumbers look goofy, move slowly, and barf up their guts when startled, but these invertebrates are superstar ocean cleaners that are hugely important to marine ecosystems.

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Like other sea cucumbers, nocturnal H. edulis use their guts to help clean seafloors and coral reefs. These Burnt Hot Dog invertebrates take shelter during daylight hours before emerging at night to inch along the sandy seafloor in search of food. Feeding tentacles help the animal shove sand and rubble through its digestive system as it moves, absorbing nutrients from detritus (dead plant and animal matter) and expelling cleaner, oxygenated sand in its wake. Healthy marine ecosystems rely on animals that provide these types of frequent cleaning services; without them, an abundance of detritus can impact plant and animal health, which in turn decreases the health of the ecosystem as a whole.

A rapid rise in East Asia's consumer demand for sea cucumbers for both food and medicine has increased fishing pressures in many parts of the world. Overfishing can spell extinction for species of sea cucumber that already face serious pollution and habitat destruction threats worldwide. For example, populations of Holothuria whitmaei and H. scabra -- once common in the entire Indian and Pacific oceans -- have recently declined 60 to 90 percent in most of their traditional ranges. Today, at least 16 species of sea cucumber are considered threatened with extinction by the International Union for Conservation of Nature (IUCN) Red List, a global authority on the conservation status of plants and animals.

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When caught in Okinawa, Japan, H. edulis is prepared and dried for food, medicine, or export overseas. A recent uptick in commercial demand for H. edulis -- a species that hasn't historically been targeted by fishing interests -- could be an indicator that more desirable sea cucumber species are becoming difficult to find in oceans worldwide.

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Hawaii provides a heartening example of environmental stewardship in the South Pacific. In June of 2015, Hawaii's State Board of Land and Natural Resources passed an emergency ban on the taking and selling of sea cucumber species in state waters, which appeared to be experiencing "imminent peril" due to overfishing for export overseas. Earlier this year, Governor David Ige signed a more detailed, large-scale ban on commercial sea cucumber take that outlined a preliminary plan for more sustainable fisheries along Hawaii's shores. Fernandez-Silva and her colleagues hope that Japan and other global entities will follow suit, protecting ecologically important -- and threatened -- marine species before they are lost forever.

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