Evaluating Risks Posed by the Live-Bait Trade in Ghost Shrimp
Researcher:
Bruno Pernet
Assistant Professor
Department of Biological Sciences
California State University Long Beach
Long Beach, CA 90840
E.: bpernet@csulb.edu
T.: 562.985.5378
Tools:
Revised:
March 4, 2009
CSU professor Bruno Pernet (left) and graduate student Bruno Passarelli collect ghost shrimp at Elkhorn Slough in Monterey Bay. Credit: Kerstin Wasson, Elkhorn Slough National Estuarine Research Reserve
March 4, 2009
Contact: Christina S. Johnson, csjohnson@ucsd.edu, 858-822-5334
LONG BEACH – Populations of the ghost shrimp Neotrypaea californiensis are genetically homogenous along the West Coast, CSU Long Beach biologists report.
The species’ lack of population structure alleviates concerns that anglers who dump their bait buckets into coastal waters might release ghost shrimp with genes different from local shrimp. California imports ghost shrimp from Washington for the live-bait trade.
Ghost shrimp imported from Washington and purchased at a Los Angeles County bait shop. Photo: B. Pernet
Based on mitochondrial DNA analyses of two genes from specimens collected between San Diego and central Washington, "Northern and southern ghost shrimp likely exchange genes routinely," says CSU Long Beach professor Bruno Pernet, who led the California Sea Grant-funded study.
“There are no apparent genetic differences between northern and southern populations,” he says. “We think our study suggests that there is little chance of introducing new genes to southern populations.”
The conclusion is consistent with the general pattern that species with long larval periods usually show little genetic differentiation over large spatial scales, says co-investigator James Archie, also of CSU Long Beach.
The larval period of ghost shrimp is about six to eight weeks, compared with about a week for some common marine snails, chitons and limpets.
Ghost shrimp are 3- to 5-inch-long mud-eating invertebrates that burrow in soft sediments of coastal waters. They have a large claw and translucent shell. The easiest way to find them is to look for their burrow holes in mudflats at low tide. Ghost shrimp, along with other mud-dwelling invertebrates, are favorite food for many species of fish, hence their use as bait.
Although there seems to be little genetic risk associated with the use of ghost shrimp as live bait, the potential to introduce and spread parasites through the practice remains a concern, says Sea Grant trainee Bruno Passarelli, a graduate student at CSU Long Beach working on the project.
An introduced parasite from Asia – possibly introduced via ballast water – is currently being blamed for a decline in the related burrowing shrimp Upogebia pugettensis in Washington. “We know it can happen,” Passarelli says.
CSU Long Beach biologists are in the process of evaluating species of parasites on imported ghost shrimp and their viability in warmer southern waters. They are also surveying California sportfishing shops about what species they sell for live bait and their quantities, to further evaluate ecological risks posed by the live-bait trade.
In addition, they have developed genetic markers that allow them to differentiate N. californiensis from the closely related species N. gigas. This work has shown that one of the two species, but not both, are dominant at the sites sampled.
Sediments in Anaheim Bay where Neotrypaea gigas is common. Most of the holes are ghost shrimp burrows. Photo: B. Pernet
In Anaheim Bay, for example, N. gigas comprised 97 percent of the total ghost shrimp collected, compared with 3 percent for N. californiensis, while at Dog Beach in San Diego, N. gigas comprised 1 percent, compared with 99 percent for N. californiensis.
Why should anyone care about distributions of two closely related burrowing invertebrates?
“Ghost shrimp are like earthworms except more active,” Pernet explains. “A single square meter of mudflat can have 450 ghost shrimp. Each of their burrows may descend a foot or more.”
“Because they are constantly excavating these burrows, and because they are constantly pumping water through them, they have a profound affect on a habitat’s physical structure and geochemistry,” he says. “We want to know their populations are healthy and what environmental conditions support healthy numbers.”
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NOAA’s California Sea Grant College Program (www.csgc.ucsd.edu) is a statewide, multi-university program of marine research, extension services, and education activities administered by the University of California. It is the largest of 32 Sea Grant programs and is headquartered at Scripps Institution of Oceanography at the University of California, San Diego. The National Sea Grant College Program is part of the National Oceanic and Atmospheric Administration (NOAA), U.S. Department of Commerce.
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