Salvadoran immigrants wait on May 15 at the main migration center in San Salvador after being deported from Mexico. (Fred Ramos for The Washington Post)

In a different era, Oscar Galvez Serrano might have abandoned his mother’s tin-roof shack in the jungly Central American hills by now and set out for the United States.

Despite having been deported in March, Galvez said, he would have tried to quickly return to join his 11-year-old son in Sherman, Tex., and his siblings and cousins. He would have taken another job — roofing, landscaping or washing dishes. There is something different now, however, looming over Central Americans’ decisions on migration: President Trump.

Migrants used to feel that if they reached the United States illegally, they could stay. “They’ve gotten rid of all that,” said Galvez, 36. “I still hope I can go back there. I just don’t know when.”

Trump has credited his tough stance on illegal immigrants for the sharp decline in apprehensions of migrants at the U.S.-
Mexico border, tweeting in March that “many are not even trying to come in anymore.” In the first four months of the year, U.S. authorities have detained about 98,000 would-be immigrants heading north, a 40 percent drop from the previous year.

In El Salvador, which has contributed tens of thousands of border crossers in recent years, officials and potential migrants acknowledge that fewer people are heading to the United States. But they say that the slowdown may be temporary — and that the drop-off may not be as large as it seems.

The biggest decline in detentions at the border is for migrants from the Northern Triangle countries — El Salvador, Honduras and Guatemala — according to Kevin K. McAleenan, acting commissioner of U.S. Customs and Border Protection. Last month, 3,400 people from those countries were apprehended. The previous April, that figure was more than 16,000.

After Trump’s election, “we saw the drop in crossings almost immediately,” McAleenan said, adding that migrants thought that immigration enforcement “has strengthened and intensified.”

Trump has pledged to deport millions of illegal immigrants, build an extensive border wall and cut funding to “sanctuary cities” that refuse to cooperate with federal deportation efforts. Some of Trump’s promises, including the border wall, remain in doubt over opposition and budget battles in Congress.

But Salvadorans say they are taking their cues from undocumented family members in the United States, who are living in greater fear of deportation. Amid the talk of tougher border enforcement, smugglers have also raised their prices: A trip that once cost $6,000 could now cost as much as $10,000.

Measuring the total flow of migrants is difficult. Figures on border detentions do not tell the whole story, since many migrants evade capture. Starting in 2014, though, hundreds of thousands of Central American families fleeing violence and poverty surged toward the border. Many turned themselves in to the Border Patrol, asking for asylum because of the gang violence in their home countries. Such people were often allowed to live where they chose as they awaited a distant court date in the backlogged U.S. immigration system.

These days, more Central American migrants are resorting to sneaking across the border, a change that has contributed to the decline in apprehension numbers, according to U.S. and Salvadoran officials.

“This practice of turning themselves in to the migration authorities has diminished,” Héctor Antonio Rodríguez, the head of El Salvador’s migration agency, said in an interview. “They have lost confidence in the authorities. There is no confidence now to apply for asylum like before.”

Rodríguez agreed, however, that fewer migrants were making the trip north, as detentions in Mexico — which Central American migrants usually transit to get to the United States — also have fallen significantly this year. He said this was primarily because of Trump’s harsh rhetoric on illegal immigrants.

“We don’t know what laws have changed. What we do know is what our relatives tell us and how people at the street level are living,” said Manuel Flores, 33, a metalworker who was deported in 2009 and has three siblings in the United States. “The day Trump took office, they tell us, things changed.”

Two of his brothers have canceled plans to build a house in their home town of San Jose Las Flores, in a part of northern El Salvador where villages have sent migrants north for decades. Flores said his brothers did not want to risk a big investment at such a precarious time for migrants without papers. One of them quit a night-shift job because he does not want to be driving when fewer cars are on the road and he would be an easier target for police. On weekends, they now rarely leave the house.

“Many people have frozen their plans because of this fear,” Flores said.

The slowdown in migration could be temporary, officials here say.

Migrants and their families are watching closely to see whether the Trump administration moves ahead with mass deportations, or carries out its threat to prosecute parents for paying smugglers to bring their children to the United States. But the pressures pushing people north have not disappeared.

“People are waiting to see what will happen,” said Brendan Forde, a 73-year-old priest who attends to the rural villages in Chalatenango state in northern El Salvador. “I don’t think the desire has changed.”

In recent years, Northern Triangle countries have had some of the highest homicide rates in the world, as street gangs such as MS-13 and 18th Street have battled for supremacy. The gangs also have squeezed residents with extortion demands.

Since 2015, when there were more than 19,000 killings in the Northern Triangle, homicide rates have been falling in the region. In the first four months of this year, the number of homicides in El Salvador has dropped by about 50 percent compared with the same period last year, amid a government crackdown on gangs.

Nonetheless, immigration experts and officials here say thousands still wish to leave dangerous communities. Now, though, Salvadorans are moving internally and seeking refuge in other countries, such as Mexico, Costa Rica or Canada.

“I don’t think there’s any reason to believe the displacement has dropped off,” said Jeanne Rikkers, research director at Foundation Cristosal, a human rights organization in San Salvador.

A growing number of Central American migrants are seeking to stay in Mexico rather than continue the trip to the United States. Between November 2016 and March 2017, more than 5,000 Central Americans filed asylum applications in Mexico, an increase of 150 percent over the same period a year earlier, according to government statistics.

At the same time, Central Americans are facing a stricter asylum process in the United States, where they must demonstrate that they would be persecuted if they returned home, according to immigration lawyers and advocates. New guidelines issued by the Department of Homeland Security in February “signal to immigration and border agents to be even more hesitant in determining who has established enough ‘credible fear’ to gain asylum,” Adriana Beltrán, a Central America expert at the Washington Office on Latin America, a research and advocacy group, wrote in a report.

About 10 asylum seekers per week used to come to Sandra Guevara’s office in San Salvador for advice on the U.S. application process. Now, she said, the office sees about one person per week.

“It’s not necessarily that the [U.S.] laws have changed. What has changed is the way they are applying them,” said Guevara, the executive director of COIMSAL, an organization that helps people with legal migration. “Now they [U.S. authorities] are being more rigorous.”

Despite the “Trump effect,” many Salvadorans are still determined to get to the United States, where they have extensive family networks and the prospect of work.

Pedro Arias Alvarado, a 42-year-old construction worker and security guard, got picked up by authorities in southern Mexico on his way to the United States and sent back to San Salvador this month. He said he had left his home country because the $300 he makes each month does not cover his son’s university studies plus his other bills.

“Here, unfortunately, the situation we are in is critical,” he said, sitting in a processing center for deportees. “What we earn is not enough.”

Arias plans to return to the United States somehow.

“I’m going to work two or three months to save up, and see if I can travel,” he said. “I would like to go again.”

Gabriela Martinez in Mexico City contributed to this report.