Survivor Vaquita porpoises escape extinction longer than expected
by NOAA Fisheries 6 Aug 2022 18:51 UTC
A pair of vaquita swimming south of the town of San Felipe, Baja California. Note the nick in the dorsal fin of the larger individual in the foreground. This was likely caused by past interactions with gillnets, from which the animal successfully escaped © Todd Pusser
At least seven to eight remain but deadly fishing is on the increase.
Projections previously indicated that the critically endangered vaquita could be extinct by now. While vaquita remain on the edge of extinction, new research shows the few survivors are reproducing. They may have found ways to evade the gillnets that have otherwise decimated the species.
An international team of researchers published More vaquita porpoises survive than expected today in Endangered Species Research. The research also documented high levels of illegal fishing within the last tiny stronghold for vaquita. The area is supposed to be a no-entry and no-fishing area according to Mexican regulations. This illegal fishing puts the survival of the vaquita at greater risk.
"Finding any vaquita in the area is a surprise, given the rapid declines detected in previous surveys," said Lorenzo Rojas-Bracho, the lead author of the new research who, at the time of the research, was with the United Nations Development Program - Synergy at the National Commission of Natural Protected Areas, Mexico. "These survivors are the future of an endemic species of Mexico, and must be protected."
Small-scale fishermen use the gillnets to catch shrimp and fish, but the nets can accidentally kill vaquita. Scientists stressed that the only way to help save the vaquita is to prevent gillnets from being set in the small area where these small porpoises are found. The paper reiterates that until fishers can make a living without using gillnets, extinction is unavoidable. Alternative fishing gear that would not entangle vaquita exists, but requires additional investment, effort, and enforcement to implement. None of this alternative fishing gear was observed being used in recent surveys.
"Against all the odds, we still have one last chance to save the vaquita," said Barbara Taylor, a research scientist at NOAA Fisheries' Southwest Fisheries Science Center and coauthor of the paper. "Give these animals a chance and they can survive."
Few Vaquita Remain
The research used an established method called expert elicitation to determine a minimum number of vaquitas seen on shipboard surveys in 2019 and 2021. The surveys concentrated on the 12 by 24 kilometer area where nearly all detections of vaquitas in recent years have been made.
The number seen can be taken as an estimate of the minimum number of individuals. There is not enough information available to determine an overall population size of how many vaquita are left. That is in part because crews of vessels fishing illegally have damaged and stolen acoustic monitors that could provide more detailed and long-term data.
"In the absence of direct data on the quantities of interest, expert elicitation is the next best alternative for providing quantifications that can be used for decision making," said Len Thomas of the Centre for Research into Ecological and Environmental Modeling at the University of St. Andrews in Scotland, who helped lead this recent process.
Researchers estimated that seven to 15 vaquitas were seen in 2019 and five to 13 were seen in 2021, with calves sighted both years. This indicates that the surviving animals are still reproducing. The 2021 survey estimated the most likely number of vaquita seen was between seven and eight. Finding any of these small porpoises was a surprise, given a model that projected the 2018 population size of vaquitas and rate of decline. Observing these survivors seemed miraculous given the almost-certain increase in the number of gillnets known to be the sole threat to the species.
Signs Suggest Porpoises May Learn to Avoid Fishing Gear
The scientists identified clues suggesting that some remaining vaquitas may have learned to be more wary of gillnets. They noted that a few vaquitas appeared to avoid gillnets during an effort in 2017 to capture and protect some remaining animals in captivity. Some also had scars from previous gillnet encounters that they have survived.
"If you kill 99 percent of the animals, the 1 percent that are left are probably not random. Models do not necessarily account for the intelligence of vaquitas that may have learned how to escape gillnets," Taylor noted. "That could help stave off extinction of the species a little longer, but vaquita are not far from disappearing because gillnets remain the primary means of making a living in nearby towns and even protecting the small area where vaquitas remain seems beyond enforcement abilities. Until fishers have access and training in alternatives to gillnets, vaquitas' extinction is guaranteed."
"I have said several times that vaquitas are very resourceful and if we stop killing them, they will recover," Rojas-Bracho said. "Mexico has all the "ingredients" for management actions to prevent this species from becoming extinct and, in the long term, to recover."