The number of illegal immigrants attempting to enter the US by crossing the Rio Grande has fallen dramatically since President Trump took office.

In March this year, only 4,143 people were detained by Border Patrol Agents at the notorious river crossing as opposed to 15,579 who were caught in January before Trump was in full swing in the White House.

The sharp decline has been chalked down to the president's tough line on immigration.

Border Patrol agents said migrants were no longer willing to risk the dangerous journey and pay steep smuggler fees now that the chances of them being allowed to stay in the US are so slim.

The phenomenon at the Rio Grande crossing is not isolated. Only 12,193 people were arrested across the entire Southwest border in March, 50,000 fewer than in October.

The number of immigrants arrested at the Rio Grande border crossing has fallen dramatically since President Trump took office in January

In Yuma, Arizona, only 336 were arrested trying to cross the border in March whereas 1,155 were stopped in January.

El Paso, another busy crossing in Texas, saw only 976 arrested in March, a decrease of 1,803 since January.

The drop bucks a five-year trend of increases. Since 2012, the total number of immigrants either arrested or turned away from the border has risen.

The end of 2016 brought the highest number of crossings with 56,000 arrested or turned away in September alone.

October, November and December were among the busiest months in the last five years as hundreds of thousands attempted to rush in to the country before Trump took office.

U.S. Customs and Border Protection attributes the decline since then to the president's crackdown.

The entire border has seen dramatic monthly decreases since Trump took office in Januaryn after a spike in attempted entries in October, November and December

The crossing is the busiest along the Mexican border with thousands pouring in every month to seek asylum in Texas. Above, a group of migrants remove their shoelaces after being caught by Border Patrol agents in April last year when traffic was heavier

The 1,885 mile stretch of water runs directly along the southeast Texas border

Thousands have died trying to make the crossing in treacherous parts of the river. Above, one group is led through it by a smuggler on March 14, 2017

On his third day in office, President Trump signed an executive order demanding the construction of a wall along the entire border. Above, a road crew is seen reinforcing the border next to the Rio Grande in Hidalgo last month

'Since the Administration’s implementation of Executive Orders to enforce immigration laws, the drop in apprehensions shows a marked change in trends,' it says.

On January 25, three days after being sworn in, President Trump signed an executive order demanding tougher regulations across the Southwest border.

Border Patrol agents have credited President Trump's tough stance on immigration with the decline

The order includes the construction of a physical wall to run the length of the border which Trump promised to deliver throughout his election campaign.

While he has not implemented new immigration laws, the order enforces rules already made. It places emphasis on removing anyone deemed ineligible, a threat which border officials say has spooked illegal migrants.

'Are you going to risk a 1,000-mile journey and pay $8,000 to be smuggled if you’re not sure you’ll get to stay? I wouldn’t,' Marlene Castro told The Los Angeles Times, describing how the once 'hot' Rio Grande crossing was now quiet.

The Rio Grande crossing is the busiest route for illegal immigrants entering the US from Mexico.

Thousands have died trying to complete the treacherous journey, many of them drowning in the river's troublesome waters.

Deaths in the river increased last year as immigrants tried to cross over new, uncharted sections of it. More than 300 died in just six months in 2015.

