California authorities have filed lawsuits against 20 national restaurant chains for allegedly failing to warn customers about high levels of mercury in certain types of fish. California Attorney General Bill Lockyer filed the lawsuits on Thursday against restaurant chains including Landry's Restaurants, Red Lobster Seafood Restaurants, Olive Garden Italian Restaurant and Outback Steakhouse, accusing them of knowingly selling swordfish, tuna and shark without posting the mandatory warnings, reported Reuters.