1999 – The Center and two other conservation groups filed a lawsuit against the U.S. Army Corps of Engineers to stop construction on the Seven Oaks Dam on the Santa Ana River.
2000 – In the same year in which the fish was declared threatened under the Endangered Species Act, a Center lawsuit resulted in a court order compelling the U.S. Fish and Wildlife Service to map out and protect critical habitat for the Santa Ana sucker within a year.
2001 – In response to the Center's Seven Oaks Dam lawsuit, the Army Corps agreed to review the impacts of the dam on endangered species, including the Santa Ana sucker. The agency is still in the process of devising a Multiple Species Habitat Management Plan to minimize and mitigate the dam's effects.
March 19, 2002 – The Center and allies sued the Service after the agency failed to comply with the 2000 court order to designate critical habitat for the Santa Ana sucker.
February 26, 2003 – The Center secured a court order requiring the Service to designate and protect critical habitat for the Santa Ana sucker within the Los Angeles basin by the following year. Until the designation was complete, the court forbade the agency from approving any projects that would have harmed the sucker's habitat in the Santa Clara, San Gabriel and Santa Ana rivers and Big Tujunga Creek.
January 4, 2005 – Though the Service had designated 21,000 acres of critical habitat for the Santa Ana sucker in February 2004, the agency slashed protections to just 8,305 acres — none of it within the Santa Ana basin.
November 15, 2007 – The Center filed suit against the Service challenging the decision to slash the Santa Ana sucker's critical habitat.
January 15, 2009 – The Center reached a settlement with the U.S. Fish and Wildlife Service over the scientifically flawed and politically tainted decision to reduce the Santa Ana sucker's critical habitat. The Service agreed to make a new critical habitat proposal by December 1, 2010.
December 8, 2009 – As a result of our lawsuit, the Service proposed to protect a total of 9,605 acres, including the fish's namesake river, the Santa Ana.
December 2, 2010 – The Service finalized a critical habitat designation of 9,331 acres for the Santa Ana sucker.
November 22, 2011 – Four conservation groups — the Center for Biological Diversity, Sierra Club, San Bernardino Valley Audubon Society and California Trout — sought to formally intervene in a lawsuit filed by a dozen Southern California water agencies and towns against the Fish and Wildlife Service's designation of habitat protections for the Santa Ana sucker.
October 23, 2012 – A federal judge upheld the critical habitat protections designated for the fish in 2010.
July 25, 2016 – The Center for Biological Diversity and Endangered Habitats League announced our intent to sue the U.S. Army Corps of Engineers for its failure to assess harm to Santa Ana suckers regarding the effects of management of Santa Ana River flood-control projects, including operation of the Seven Oaks Dam, on the fish and its federally designated critical habitat.
August 22, 2016 – The Center and two partners filed a notice of intent to sue the cities of Colton and San Bernardino and their regional wastewater reclamation authority for illegally killing Santa Ana suckers.
September 15, 2016 – The Center and two allies filed a request with the Santa Ana Regional Water Quality Control Board to amend the permit of the Rapid Infiltration and Extraction (RIX) facility to require adequate water flows in the Santa Ana River for the Santa Ana sucker.