This is Scientific Americans 60 Second Science. I'm Steve Mursky.

Oh!

There's the first of the allies.

All silvery, they're all about the same size. You can't tell the boys from the girls.

These will be the first. Stephen Gephart, Fisheries Biologist with the Connecticut

Department of Energy and Environmental Protection.

Gephart brought 400 Alewives down from the Nutmeg State to be released into the Bronx River on the grounds of the Bronx Zoo on April 20th.

The Bronx River was once so polluted that it was called an open sewer, but it's been cleaned

up to the point where it can now once again support these fish, which were common here in the 19th century.

Alewives are herring, they're kind of like a miniature shad.

John Waldman is an aquatic conservation biologist at Queens College who was on hand for the release.

They're born in freshwater, they rear for the first year in freshwater, then go to sea, spend a few

years growing larger, and then return to the river they were born in, much like salmon or a sturgeon or

shad. It's called an anagamous life history and this river appears to have a

small relic run that never really expanded because it was limited by the habitat.

And now there's a fish ladder on the first dam and these fish that are being stocked today, 400

alewives.

And the idea here is that if they spawn in this section, 400 return when they're old enough to spawn several years from now and want to go over the

fish ladder. In the meantime, several fish have used the fish ladder on their own this

week that were from wild fish that were existing as a little relic stock I believe in this section of the river.

So between the two I think the future looks very promising to have a much larger run.

The water here behind the Bronx Zoo is just perfect for ill-wif spotting.

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