WASHINGTON -- The University of California at Merced has escaped another potential environmental snare, as the Bush administration has decided not to protect a small wetlands-loving crustacean under the Endangered Species Act.

In a decision to be formally announced Monday, the Fish and Wildlife Service has determined the midvalley fairy shrimp shouldn't be designated as endangered or threatened.

"I think it's a wise decision," Merced Democrat Dennis Cardoza said Friday. "They have already [protected] a significant amount of habitat, and the species will be helped by those earlier decisions."

Fish and Wildlife Service officials, in documents prepared for the Monday announcement, say they will continue to review new scientific information about the shrimp's status. Overall, though, the officials contend any potential threat can be handled with existing rules and protections.

"From what we know of the current range and distribution of the species, it is well-represented by occurrences on protected lands and in areas with little or no known current threat," the Fish and Wildlife Service stated, in documents provided Friday to San Joaquin Valley lawmakers.

Like Cardoza, Mariposa Republican George Radanovich hailed the agency's decision. Radanovich and Cardoza have criticized the current Endangered Species Act and are pressing for it to be revised.

Environmentalists, though, worry that federal officials aren't doing enough to protect vulnerable species.

"Fairy shrimps swim upside down with graceful, rhythmic beats of their 11 pairs of delicate legs," the Center for Biological Diversity states on its Web site, adding that "the midvalley fairy shrimp is a vital part of this web of life."

The soft-bodied, short-lived shrimp favor the seasonal wetlands known as vernal pools in Merced, San Joaquin, Sacramento, Contra Costa, Solano, Fresno and Madera counties.

The Center for Biological Diversity, joined by a group called Vernalpools.org, filed the original petition to protect the midvalley fairy shrimp in October 2001. The main motivation is not because anyone thinks the shrimp is cute. Rather, by protecting the shrimp, environmentalists hope to stanch the loss of Central Valley habitat.

By some counts, well over 90% of the region's original vernal pool habitat has been paved over, plowed over or lost in other ways.

"Vernal pools are one of the most threatened habitat types in the world, and are destroyed or altered in a number of ways including direct destruction due to development and indirect hydrologic changes," the environmentalists stated in their original petition.

Endangered species proposals often are controversial, but the fairy shrimp family has been a particularly hard case ever since the University of California chose its new Merced campus. The campus location already has been shifted to better protect sensitive vernal pools, and UC Merced proponents fear getting bogged down in further disputes.

A decade ago, the Fish and Wildlife Service designated four other fairy shrimp species found throughout the Central Valley as threatened or endangered. The midvalley fairy shrimp is generally similar to these other species, though it has a smaller overall range and tends to like shallower pools of water.

Last April, the Fish and Wildlife Service announced there was enough evidence to warrant investigating whether federal protections should be extended to the midvalley fairy shrimp.

"High annual losses of vernal pool habitat prior to 1997 ... high population growth estimates, and threats from specific proposed development projects such as the new University of California at Merced campus" all potentially render the species vulnerable, officials noted at the time.

At the same time, Fish and Wildlife Service officials cautioned then that there could be good reasons not to protect the midvalley fairy shrimp, including the fact that protections already extended to other shrimp species would serve as adequate protection.