MEXICO CITY - Mexico's efforts to save the critically endangered vaquita, the world's smallest porpoise, has suffered a major blow after one of just 30 creatures thought left in the wild died soon after being captured by authorities.
The vaquita marina, known as the "panda of the sea" for the distinctive markings circling its eyes, has been pushed to the brink of extinction by illegal gillnet fishing.
The Mexican government and conservation groups have launched an unprecedented plan to save the species by taking as many as possible to a protected marine reserve.
Mexico's environment minister Rafael Pacchiano had lauded Saturday's capture of a mature female - the first animal of reproductive age to have been caught - as "a great achievement that fills us with hope."
The captured vaquita, however, "suffered complications" and its condition deteriorated, Pacchiano tweeted.
Attempts by authorities to release it back into the Gulf of California - the only place in the world vaquitas are found - proved unsuccessful.
Pacchiano announced the vaquita's death on Sunday, and said "we remain committed to saving the vaquita from extinction."
Authorities were awaiting autopsy results to understand the cause of death. The International Committee for the Recovery of the Vaquita (CIRVA), which designed the programme, said "the entire rescue team is disconsolate because of this devastating loss."
CIRVA said that while the rescue operation involved significant risk, scientists warned that "the risk of extinction due to mortality in fishing nets was much greater than the risk of rescue efforts."
The current initiative, which began in October, is trying to locate the remaining vaquitas using acoustic monitoring, visual searches and dolphins trained by the US navy.
Captured vaquitas will be transported to a marine sanctuary, where it is hoped they will breed before being released back into the wild.
The vaquita has been nearly wiped out by gillnets used to fish for another species, the also endangered totoaba fish, whose swim bladder is considered a delicacy in China and can fetch as much as US$20,000 (S$27,291) per kilogram.
In June, Mexico announced a series of measures to protect the vaquita, including a permanent ban on gillnets in its habitat. The government has committed more than US$100 million to save the vaquita while supporting the local fishing community.