WASHINGTON - The U.S. Coast Guard saw a nearly fivefold increase in the number of migrants it intercepted off the coast of southern California in 2018, underscoring the challenge that will remain in stopping illegal migration even if President Donald Trump secures funding for his southern border wall.

The numbers, released to The Washington Post in recent days, show the service intercepted 1,022 migrants at sea there in the fiscal year ending Sept. 30. That was up from 213 in 2017 and 142 in 2016.

Nationwide, the number of migrant intercepts at sea dropped from 2,512 in 2017 to 1,668 in 2018, indicating a shift in which more migrants are now intercepted off the West Coast. The majority of migrants taken into custody there come from Central and South America, while migrants caught along the East Coast are more likely to come from Haiti or other islands in the Caribbean Sea.

A Coast Guard spokesman, Chief Warrant Officer 4 Barry Lane, said that the migrants intercepted at sea in 2018 come from numerous countries in the Western Hemisphere, including Mexico, Ecuador, Bolivia, Colombia and Guatemala. Others came from farther away nations that include China, Sri Lanka, India and Jordan, he said.

For years, the Coast Guard intercepted more migrants off the coast of Florida than anywhere else. Those numbers plummeted in 2017, after the Obama administration normalized diplomatic relations with Cuba and ended the so-called wet-foot, dry-foot policy that allowed most Cubans who made the 90-mile trip by sea to pursue legal residency.

The service also intercepted 209,000 kilograms of cocaine at sea in 2018, falling just behind its record grab of 223,843 kilograms in 2017. The majority of those drugs are interdicted by a handful of Coast Guard cutters in the eastern Pacific Ocean, as they meet ships heading from Central and South America.

Intercepts at sea represent a fraction of a much larger trend. Customs and Border Protection reported 415,517 total apprehensions at the southern border in fiscal 2017, and 521,090 more in fiscal in 2018. More than 60,000 migrants were arrested in each of the last three months attempting to enter the country illegally.

But the statistics will still serve as new fodder for advocates of the Coast Guard, whose service members are among the federal employees working without pay amid a partial government shutdown caused by a political dispute over President Trump's proposed southern border wall. Service members are due a pay check on Tuesday, and unlikely to get their money. The shutdown was 24 days old - and the longest in U.S. history - as of Monday.

Although the service is considered a part of the U.S. military, it has no funding because it is part of the Department of Homeland Security. Most other branches of service are part of the Defense Department, which has funding approved.

The shutdown also has threatened the pensions of Coast Guard veterans. Adm. Charles Ray, the service's No. 2 officer, said in an email to retirees on Saturday that there is the "distinct possibility" that retiree pay and money for the Survivor's Benefit Plan, an insurance policy for the surviving spouses of Coast Guard veterans, may be delayed if the shutdown continues into late January.

"Please be assured that we are continuing to work closely with the Department of Homeland Security, the Administration, and Congress to reduce the impacts of this funding lapse on our Coast Guard workforce - past and present - and I will keep you informed as additional information becomes available," Ray wrote.

The shutdown has put other strains on the service, as Trump seeks funding for the wall. The president has promised to fund new polar icebreaker ships for the Coast Guard, but funding for them is no longer a certainty. A Senate appropriations bill passed last year included $750 million for the first ship, but the House version did not include the money. It is not clear whether the money will be included if a spending bill makes it to the White House.

The Coast Guard commandant, Adm. Karl Schultz, has posted a series of social-media messages in recent days as he seeks to reassure the force.

"I recognize that there is anxiety & uncertainty about the status of your pay this evening," Shultz tweeted Monday night. "Your senior leadership team continues to work on your behalf. We will provide an additional update by 1200 EST. Continue standing the watch - I am proud of your unwavering devotion to duty."