It’s too early to tell how abundant the veined rapa whelk, which eats other shellfish, is in the Chesapeake Bay, but preliminary numbers don’t look good, researchers say.

Scientists first detected the non-native predator in the Bay in 1998. More than 1,300 whelks have been brought in since the Virginia Institute of Marine Science has been monitoring the species; 411 of those in late April and early May.

“You can see, there’s been a lot of them collected just recently and that number isn’t a good sign,” said Roger Mann, VIMS marine science professor. “That tells you that there are a lot of them out there.”

Researchers say it will take several years’ worth of information to estimate the size of the whelk population or exactly how far the snail-like creatures roam.

Native to the Sea of Japan, veined rapa whelks gobbled up shellfish in the Black Sea after their European introduction about 50 years ago. Scientists think the whelks came to the Bay in the ballast tanks of ships.

Researchers trying to learn more about how the rapa will affect the native Bay species are offering a bounty on the whelks to help them map the species’ distribution.

Mann estimates that VIMS has paid less than $5,000 worth of bounties. Originally set at $5, the bounty later dropped to $2 because VIMS couldn’t afford the first price.

“We collected a lot more than we initially thought,” he said. “We lowered the bounty because our bank account wasn’t that big.”

But dropping the bounty meant raising the difficulty level for watermen, Mann said. “People were pretty good about bringing them in, but at the same time these guys were going to lose money helping us out.”

So the bounty has been raised. Live rapa whelks will garner the $5 bounty, and $2 will be given for dead animals.

Juliana M. Harding, another VIMS scientist, said the current range of samples is from the mouth of the Rappahannock River in the north, to the Chesapeake Bay Bridge-Tunnel in the southeast, to just above the James River Bridge in the southwest.

VIMS has set up a Rapa Hotline — 804-684-7361 — to report rapa whelks and request a pickup. Callers should provide their name, collector’s name (if different from caller), date whelks were collected, status of whelks (dead, live, empty shell), phone number and where the whelk was collected. A member of the VIMS staff will call to verify the pickup address and where to mail the bounty. VIMS cannot pay a bounty to callers who do not leave a phone number.