MEXICO CITY -- Tuesday's statement by the Mexican Navy stated that it had begun a controversial plan, to place concrete blocks on the bottom of the Gulf of California in order to capture illegal nets that would drown critically endangered vaquita Marina porpoises.

Eight of these tiny and elusive porpoises are still living in the Gulf, also called the Sea of Cortez. They cannot be captured or bred in captivity.

Vaquitas are caught and drowned in illegally set gillnets by fishermen for totoaba. This fish is highly prized in China, where it can fetch thousands of dollars per kilogram.

The Mexican government has abandoned all efforts to keep small fishing vessels out of the 110-mile (288 km) "zero tolerance” area near San Felipe in Baja California. This is where few vaquita remain.

Tuesday's approval of the plan to sink 193 concrete block was unanimous. Environmentalists expressed concern that remnants of nets could be left attached to the blocks, which could cause further harm to sea life.

"This is a surprise because the environmental impact report was approved in record speed, in just six weeks. "It wasn't open to public comment," stated Alex Olivera, Mexico representative for Center for Biological Diversity.

Mexico's Environment Department admitted that there was no public comment. However, it said that this was because no one had asked for one. It is well-known for its speedy approval of government projects.

There are many doubts about the plan. Every kilometer beyond the zero tolerance zone, it would scatter one block and attack it with a metal hook. It is unclear how or if any snagged wires would be found underwater.

Olivera stated that a net can be caught on hooks. We don't know how long these nets are.

Ghost nets are abandoned nets that can kill marine life for many years.

Out of fear over reprisals, another expert said that the plan could discourage illegal fishermen by making them lose their nets to the snags.

He said that the navy should regularly remove any snagged or entangled nets because "other species could be endangered down there."

The navy announced the plan in a statement. It made no mention of "recovering the detained nets." In reality, divers would have to descend and manually remove the nets from each of the 193 blocks every few day.

The defiance displayed by fishermen and the lucrative nature illicitly traded in dried totoaba bladders means that there is no guarantee that fishermen will not physically mark the locations of the blocks and fish surrounding them.

The Mexican government ended its policy of keeping fishing boats from the "zero tolerance zone" in the upper Gulf last year. The Mexican government then created a sliding scale of penalties for more than 60 fishing boats that are seen in the region on multiple occasions.

Olivera expressed doubts. He said, "They can't be monitoring these blocks every single day."

The United States filed the first ever trade-based environmental complaint under U.S.-Mexico Canada trade pact earlier this year. It argued that Mexico was failing to protect the species.

Mexico has accepted to be investigated. The treaty was signed in 2020 and could result in trade sanctions.