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Researchers Studying Impact of Popular Imported Fishing Bait, Including Ghost Shrimp

Published: July 15, 2009

Ask Southern California anglers what kind of bait they like to use and the answer often is “ghost shrimp.”

Although the crustaceans can sometimes be found in local shallow, muddy ocean tidal inlets like Alamitos Bay and Huntington Harbour, many fishermen buy the live shrimp and other bait such as worms that are imported by Southern California bait shops.

But what impacts could this imported bait have on local native marine life? That’s what Bruno Pernet, an assistant professor of biological sciences at CSULB is looking at. He is being assisted by graduate student Bruno Passarelli.

“We’re interested in whether or not live bait that are imported into the state pose a risk of the introduction of non-native species into California marine waters,” Pernet explained. “We’ve been doing this study that’s funded by California Sea Grant that focuses mostly on shrimp as a model, but we’ve broadened it a little bit.” They are examining local bait from Los Angeles, Orange and San Diego county coasts and comparing them to imported bait.

“We have three main questions. First, what species are brought into California as live bait—what are imported species from other states or from other countries, and in what numbers are they brought in every year?”

The California Department of Fish and Game has such a heavy workload that checking for import permits is a low priority, Pernet said. “There essentially is no government data as far as we can tell about what’s brought in and in what numbers. We’re in the middle of doing a survey of bait shops in the state to try to figure out the answer to that question. That’s to set up what the potential risk is. It’s pretty amazing. You can go to a bait shop and buy worms from Korea and Vietnam and Maine, or shrimp from Washington state.

“A second question is, of these things that are imported, can they survive in local waters? We’re doing a simple physiological tolerance test to see if they can survive in the temperatures of marine waters of California,” Pernet continued.

“The last question is that when you import these species, there’s a potential for them to become invasive, but there’s also a potential for parasites that are associated with them to be released into the environment and become invasive,” he said. “We’re interested in looking at parasites brought in on live bait, and for that, we’re really focusing on ghost shrimp.”

They are surveying the parasites imported with ghost shrimp from Washington and as well as the natural distribution of those parasites along the West Coast because that information isn’t well known.

Ghost Shrimp:Photo courtesy of Bruno Pernet

“The ghost shrimp that is imported from Washington is the same species as the one that live down here, but it’s coming from thousands of kilometers away. But it turns out that some of the parasites on it are probably not native down here. That’s still a little up in the air,” he pointed out. “One of the parasites we’re studying castrates the ghost shrimp. That’s important because that might influence ghost shrimp populations if they suddenly decrease reproducing.”

Ghost shrimp are about six inches long and live in soft or muddy sediments where they dig deep burrows of up to three feet, Pernet noted. “They scrape mud off the sides and eat it, and their burrows are constantly changing. They’re doing a lot of excavating like earthworms do in terrestrial systems. The other important thing is that they’re pumping water through there all the time so they can breathe. If there are pollutants buried in the sediments, those get exposed to the water, or if there are pollutants in the water, the sediment gets exposed to them, so they really modify their habitats. People call them ecosystem engineers because they really change the physical structure of their environment.”

Although the shrimp aren’t found in large quantities in Southern California, they’re common along the Oregon and Washington coastlines. There, the shrimp can be considered a pest because they stir up sediment that interferes with the growth of valuable oyster populations, Pernet explained.

Moreover, “Some of the parasites that we’re looking at in ghost shrimp that are brought in from Washington use the shrimp as an intermediary host for one stage of their life cycle, but another stage of their life cycle is spent in fishes. So, the parasite might be brought down and have some effect on ghost shrimp populations, but they also might have some effects on fish populations. We just don’t really know about those.”

Pernet said the parasites aren’t likely to affect humans who eat fish that have consumed the bait shrimp, but they could influence shrimp or fish growth.