英语听力：自然百科 Giving Fish a Bath 给鱼儿洗澡

The tropical night descends on a quiet beach, but just off shore, beneath the tranquil waves things are busy. A group of research scientists are scouring a coral reef looking for fish, or more accurately, the parasitic passengers attached to the fish. It’s all part of a field study being conducted by marine biologists Paul Sikkel and Donna Nemeth with funding from Earth Watch Institute.

"Our researchers are taking a look at some of the most intimate relationships that are happening among coral reef organisms, their parasites, their fish hosts, and the cleaning stations that they visit to get those parasites removed. "

Biologists estimate that parasites make up half of all organisms on the reef. Yet little is known about their impact. Some have developed somewhat gruesome survival strategies.

"We also caught a very large isopod called Exocorallana which actually burrows its way through the fish, usually through the anuses， it burrows inside of the fish and eat its way through the fish. It can kill it in an hour or so. "

Fortunately not all parasites are that large or that fatal. And more importantly there is a way fish with pesky parasites can get scrubbed clean.

"So a cleaning station is a place on the reef that has a cleaner goby or a shrimp or maybe both actually, where fish go to have parasites removed. These are very consistent and easy identifiable places on the reef. The fish know where they are, and we know where they are. "

These coral reef cleaning stations offer a glimpse at some of the most interesting animal behaviors on the planet. Small organisms, like this tiny goby, it might normally be a meal for a larger fish, somehow secures permission to enter the mouth of its potential predator. It’s a delicate balance, not only for these particular fish, but for the coral reef as a whole. And now conservationist are worried that the climate change may be threatening the reef eco-system, causing too many parasites and too few fish.

"We find , instead, in the sites that are more pristine have higher coral cover we tend to find fewer parasites on fish than in the sites that have lower coral cover and get more heavily impacted. "

The researchers suspect that unhealthy areas with less coral have more algae contributing to an abundance of parasites, which isn’t a good thing for their targets—the fish. And the problem, maybe exacerbated by changing water chemistry that could be lowering fishing immune systems.

To find out the fish-parasite ratio on this reef, the researchers have to collect lots of data. And that means, collecting lots of fish.

"We need to go into the coral reef environment at the times when these things are happening, in the morning when the fish are visiting the cleaning stations, or at night when the fish are resting. "

"We dive down and find the fish that we are interested in capturing, and we shine the light in the fish’s eyes, and it mobilizes the fish, and then we capture it with an aquarium net and then put it in a bait bucket. "

Then it’s time for earth watch volunteers to swoop in for an underwater bucket brigade.

"We then have snorkelers who act as runners. Our swimmers., they, we fill up a bucket of fish. We, they will take the bucket and swim it back to shore where we empty it into a larger container and then transport it back to laboratory and then another snorkeler will swim the bucket back out to us. It’s very, with their help to process 40 to 50 fish a night. "

Removing bucket loads of fish from a single reef could damage the eco-system. So the researchers need to find a way to bring them back alive.

" We take a lot of care to minimize the impact we have on the reef, so we spend the extra time to process the fish alive,and return it to the reef, alive, what is involved is placing the fish in a bucket of fresh water which we call a "fish bath service", or "fish spa servic" and we remove the parasites. "

The fish get to spend time in the spa and researchers get the parasites they need.

"If We can understand better the number of parasites that fish are normally carrying in the environment and the role that the cleaners play in adjusting those loads, we might be able to better understand how all of these parts of the reef are interconnected. "

This piscine cleaning service is giving researchers new insight into the inner workings of a complex habitat. And between the gobies and the researchers, there are a lot of well scrubbed fish on this reef.

Sponsored by National Geographic Mission Programs, taking science and exploration into the new millennium.