The Los Angeles-based production crew for "Sharknado 3" refused to work on Thursday for the third straight day. The roughly 40 employees on strike -- some of them union members, some of them not -- are asking for a contract with the International Alliance of Theatrical Stage Employees (Iatse).

Union contracts in the film and television industry offer production staff health and pension benefits that tend to otherwise be unavailable. The agreements also guarantee longer turnaround times between work as well as overtime pay, according to Vanessa Holtgrewe, assistant director for Iatse's motion picture and television production department. She says it's increasingly uncommon for even relatively low-budget movies such as "Sharknado 3" to work without union contracts. The union has a strong presence in Hollywood, with 14 locals representing over 38,000 workers.

"Sharknado 3" staff walked picket lines in Burbank and Santa Clarita on Thursday morning. Striking employees and their supporters have also taken to Twitter to raise awareness, some using the hashtag #strikenado. "No contract, no airborne marine mega-predators," tweeted the Motion Picture Editors Guild, a Iatse local.

"Sharknado 2" was produced with a union contract, according to Holtgrewe. (She doesn't know if the original version was, too.) At any rate, management doesn't seem to be taking the issue very seriously this time.

"We are happy to report that we have reached an agreement with the International Brotherhood of Selachimorpha, which represents the sharks in our film," an attorney representing production company Asylum said in a statement. "We will be increasing the amount of chum at the craft services table and will no longer require our employees to sleep without moving,"

Selachimorpha is a superorder of fish that includes all sharks.

A call left with Asylum on Thursday morning was not returned.

"It makes it crystal clear why these employees need representation," says Holtgrewe, when asked about the company's statement.

The latest installment of the made-for-TV film series is set in Washington, D.C., and features NBA owner Mark Cuban as president of the United States and conservative columnist Ann Coulter as vice president. Similar to its predecessors, the plot of "Sharknado 3" revolves around a waterspout tornado that sweeps up sharks and drops them into a city, wreaking havoc.

The film is slated to debut in July on Syfy, but an industry insider recently told a prominent film news site that the strike will likely push back the original release date.

Correction: A previous version of this story referred to the "post-production crew." In fact, the strikers are part of the "production crew."