There were only two Vietnamese-Cajun crawfish joints in town just a couple years ago when Jonathan Kauffman decided to do this dual review for the Weekly, and now there are five. (The phenomenon comes to us via the Vietnamese-American communities along the Gulf Coast in Louisiana who found success opening crawfish restaurants down there.) Today Grub Street discovers that Rockin’ Crawfish is headed for 4724 Geary Boulevard (between 11th and 12th Avenues), which has lately been home to Cable Car Pizza. And this follows on November’s news that Cajun Crawfish Boil had opened just up the street at Geary and 18th, and on the earlier opening of Cajun House Louisiana Crawfish at 308 5th Avenue. Also, there was the October closure of four-month-old House of Crawfish at 2080 Van Ness. Red Crawfish, which was one of Kauffman’s subjects, is still around on Larkin in Little Saigon, and there is also now Crawfish Station at 9th and Irving in the Sunset.