Around 8 million people are expected to visit Barcelona in 2015.

As the summer sun starts to come out in force and the high-season crowds descend on Barcelona, the city famous for a remarkable tourism-led rejuvenation is in the midst of an unprecedented crisis over how to manage the millions of people visiting it each year. Nowhere better illustrates this than the Barceloneta, a former fisherman’s quarter now at the center of a lucrative tourist trade that continues to boom amid an otherwise sluggish economy.

The Barceloneta flags that seem to hang off every other flat, and the somewhat less-ambiguous “Cap pis touristic (no more tourist flats”) signs, may go unnoticed by the casual visitor, but it’s hard to spend long in the neighborhood, or any other central part of Barcelona for that matter, without realizing that something is afoot in Spain’s most-visited city.

Last year Barceloneta erupted in spontaneous protests as thousands of furious residents organized protests against the “drunken tourism” they claimed was making life in the once-peaceful neighborhood impossible. Crowds berated tourists for bad behavior and demanded an end to Airbnb-style short-stay rental flats that they said were turning residential buildings into “youth hostels.”

Since then the city council has responded with a string of measures – community police patrols, a direct line to report disturbances in tourist flats, greater regulation of tourist flats – but the discontent continues, and the anti-tourist flat signs are only increasing.

According to Sergio Arnás, a lifelong resident of the neighborhood and spokesman for La Barceloneta Diu Prou (Barceloneta Says Enough!) campaign group that organized last summer’s protests, little has changed and further protests are almost inevitable.

He said short-stay tourist flats remain widespread and many people are forced to share buildings with noisy temporary neighbors. The result, he said, is plenty of sleepless nights and a simmering frustration in a once-tranquil neighborhood.

“But we’re not campaigning simply against anti-social behavior. Tourist flats bring insecurity and property speculation to the neighborhood,” he told me.

"No more tourist flats," reads a sign in the popular beachside Barceloneta neighborhood.

Arnás echoed what many other resident have told me in recent weeks: tourist flats and drunken behavior are only symptoms of a deeper problem – the unsustainable numbers of tourists visiting the city each year.

Across Barcelona there is unease at the influence of so many visitors. In each neighborhood the specific complaints vary, but the cause, everyone seems to agree, is the mass-tourism model adopted by local authorities more than two decades previously.

In the Gràcia neighborhood residents have occupied a building that was set to become the latest in a string of hotels to open in the area, claiming that the recent surge in tourists was pushing up prices and forcing locals out. In its place they have opened a housing office to assist people facing eviction — Catalonia suffered more than 22 percent of the 68,000 evictions carried out across Spain in 2014. Outside the office a large banner reads: “One more tourist equals one fewer neighbor.”

Similar protests have taken place throughout Ciutat Vella which holds the most hotels, while the areas surrounding top attractions Park Güell and Sagrada Familia have also witnessed protests by neighbors who feel inconvenienced by the city’s runaway tourism success. The famous La Boqueria market is another point of conflict. Following complaints from stallholders, authorities have banned large tour groups at peak times in an effort to lure local shoppers back to the market.

But while tourism is being blamed for an increasing laundry list of problems, the sector remains essential to the city’s economy – representing between 12 and 14 percent of the municipality’s GDP.

The challenge facing Barcelona’s leaders is to find a way to harness the industry without alienating residents and allowing the city to become a jaded tourist trap, or, the “new Venice.”

Barcelona’s tourism sector has been one of the principal topics in the run-up to municipal elections on May 24.

Recent surveys suggest no candidate will win enough votes for an outright majority, but the two leading candidates – incumbent Xavier Trias (CiU) and Ada Colau of the Barcelona en Comu coalition – could hardly be more opposed in their plans for the future of the city’s tourism industry.

Trias has presided over years of sustained growth for the industry and record-breaking numbers of visitors – 7.5 million in 2013 – and shown support for the hotel lobby’s aim of reaching 10 million. Aside from a few minor issues, Trias insists, the city’s tourism model is a success.

Colau, in contrast, has warned of a “tourism bubble” and described the current tourism model as “out of control.” She has also waded into the heated debate over so-called tourist flats, suggesting owners should be encouraged to convert the properties into social housing, a move likely to find stiff resistance from the vocal supporters of the model who claim Airbnb rentals offer an important means to pay the bills.

A conference organized by the Asociación Catalana de Profesionales de Turísticos (Catalan Association of Tourism Professionals) last week highlighted the complexity of the problem as politicians from all the major parties attacked varying aspects of the current tourism model.

“The protests in Barceloneta last year are a symptom that something is not working,” Sara Jaurrieta of the Catalan Socialist Party (PSC) told the conference.

Many others shared her analysis, but there was no consensus on a solution.

Whatever the result of the upcoming elections, it is clear the new administration has a challenge on its hands if it’s to preserve the city’s golden goose of tourism while avoiding a repeat of last year’s protests.