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Endangered goby may actually be two species

An endangered fish in Southern California may be even more at-risk than was thought. Called the tidewater goby, this small fish lives in lagoons along the California coast and is threatened by coastal development, habitat loss and drought. Now, new research published in PLOS ONE suggests that the southernmost tidewater goby—which is found in only three lagoons in San Diego County—is a distinct species, increasing the urgency of protecting it.

Up to 2 inches long and nearly transparent, tidewater gobies live in shallow, brackish waters where streams flow into saltwater. They live only about a year but can breed year-round, with females competing for mates and males digging nursery burrows and guarding hundreds of eggs until they hatch.

A previous analysis of mitochondrial DNA suggested that southern tidewater gobies diverged from those along the rest of the state between 2 and 4 million years ago, prompting Camm Swift of the Natural History Museum of Los Angeles County and colleagues to investigate whether the two groups of fishes also differ morphologically. “The molecular differences focused the morphological investigation,” Swift says.

Using museum specimens of tidewater gobies from throughout their range, the researchers compared physical characteristics including fins and neuromasts, which are tiny organs that sense movement and vibration in water.

The researchers found that morphological differences are indeed enough to distinguish the two groups of fishes – notably, the southern gobies had fewer rays in their pectoral fins as well as more neuromasts on their heads – and concluded that the Southern Tidewater Goby is a new species.

Ironically, the Southern Tidewater Goby has lost habitat to tidal restoration in Southern California. Historically, many of the lagoons this fish depended on there were polluted by sewage or agricultural runoff, leading to eutrophication.

“The simplest solution is often to open the lagoon to the tide to improve water quality,” says Swift, who credits his interest in preservation to having witnessed suburban development as a child. “The better solution is to provide treatment marshes that remove nutrients before water enters the lagoon.”

For now, Swift and colleagues are searching for an existing suitable habitat to reintroduce the Southern Tidewater Goby. Efforts to breed the fish in captivity are also underway. “Establishing more populations in more lagoons while using captive breeding as a form of insurance may make the most sense,” he says.

Research Article: Swift CC, Spies B, Ellingson RA, Jacobs DK (2016) A New Species of the Bay Goby Genus Eucyclogobius, Endemic to Southern California: Evolution, Conservation, and Decline. PLoS ONE 11(7): e0158543. doi:10.1371/journal.pone.0158543

Image Credit: A photograph of the Southern Tidewater Goby courtesy of author Brenton Spies.

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