Cormorant fishing has been a tradition for over 1,300 years. Climate change might spell its end.

Once a flourishing and popular practice, ukai has been in decline for decades as more commercially successful practices dominate the market and leave little need for the usho.

Nowadays, most usho in Gifu City in Japan make most of their money from tourism. Tour boats pass by to watch the usho catch fish that they'll later eat as part of their tour.

Current usho are amongst the 17th or 18th generation to practice cormorant fishing.

They raise and train their cormorants from hatchlings and follow the same tradition as their parents before them.

During the 16th and 17th centuries, British and French kings practiced cormorant fishing as a leisure activity.

King James I was known to own cormorants and use them in this manner. There are records that King James I introduced cormorant fishing to other European aristocrats by sending them cormorants as gifts.

The ayu that usho and their cormorants fish for are most active at night.

Once the cormorants are in the water, their instincts kick in, and they chase after all the fish scattered throughout the riverbeds.

The cormorants have been trained since hatchlings to catch fish and return to the boat, where the usho will massage their neck to get the fish back out.

Cormorants can keep track of how many fish they catch and, if they aren't rewarded with fish for themselves, will stop diving for more fish.

Usho have an imperial mandate to send ayu that they catch with their cormorants to the imperial household.

The mandate originates from Samurai Warlord Oda Nobunaga, who was fond of the ayu and worked to protect the tradition, being the first to give the cormorant fisherman the title usho.

Local usho attribute the changes to unpredictable weather. Heavier rains and floods on what was once a calm river have started to disrupt the ecosystem.

Because of the increased temperatures of the river, reaching a high of 86 degrees Fahrenheit, ayu spawn a month later than usual.

Flood barriers built in response to heavier rains reduce the amount of large rocks flowing into the river bed. The rocks are key to growing algae, which the ayu feed on. With fewer large stones, the ayu has dwindling access to a key food source.

The larger rocks also form a habitat for the ayu, and with smaller rocks and sand in the riverbed, the ayu have fewer places to breed, eat, and live.

In some cities, boats allow visitors to eat and drink while they watch the usho work.

In Gifu City, one of the most popular cities for cormorant fishing, the spectacle draws in over 100,000 people a year and brings in approximately $2.5 million USD a year.

The same environmental factors that impact the ayu have carried boats off course or canceled tours at the last minute.

Recently, an economic development body known as ORGAN set up elevated riverside viewing decks on a trial basis. The decks are an attempt to recreate the boat experience and are even hosted by apprentice geishas and other traditional performers.

Toichiro Adachi, the son of the usho, Youichiro Adachi, is training to become a cormorant master but spends his days working computers making high-precision machine tools.

"I want my son to inherit my job, but it's tough to make a living," Adachi told Reuters. "If we cannot catch fish anymore, our motivation is gone and there's no meaning in what we do."

"For me, cormorants are my partners," Adachi told Reuters.

Cormorants in the wild live for 10 years, but cormorants under the care of their usho can live for up to 30.

When a cormorant dies of old age, it is ceremonially cremated. At the closing of each fishing season, all the usho hold a vigil presided over by a Buddhist priest to honor all the cormorants that passed away that year.

"They are essentially members of my family," Shuji Sugiyama told the South China Morning Post. "I am constantly checking on their health and making sure they're rested and well-fed. I don't see myself as their master; I am part of their team."