Most call them "sting rays," and they do have a sharp, pointed stinger at the base of their long, skinny tails that is to be avoided. Bat rays are most often caught by accident, by those fishing for sturgeon, striped bass and sharks. Field scouts Abe and Angelo Cuanang discovered that the big bat rays roam the tidal bay flats to feed during high tides at night. Bat rays canvas the bottom for crabs, mud shrimp and clams, and the best bait is usually a whole squid. The Department of Fish and Wildlife, water districts and concessionaires will plant these lakes with rainbow trout this week (plant totals are provided by DFW only for East Bay Regional Park District lakes): Alameda County: 750 pounds at Lake Chabot in Castro Valley; 750 pounds at Del Valle Reservoir south of Livermore; 500 pounds at Quarry Lakes in Fremont; 500 pounds at Shadow Cliffs Lake in Pleasanton; 500 pounds at Lake Temescal in the Oakland hills. The Department of Fish and Wildlife opened the Smith River on Thursday to fishing, with enough rain to overcome the low-flow closures. The best fishing time this weekend for sturgeon, striped bass, sharks and surfperch will be from roughly noon to sunset, and will peak in the afternoon. Shadow Cliffs ramble: 2-mile wildlife walk on Lake Trail at Shadow Cliffs Lake in Pleasanton; meet at 9 a.m. at last parking lot near trailhead for Lake Trail. www.ebparks.org. Guided walk on shore of bay at Elsie Roemer Bird Sanctuary in Alameda; meet at 10 a.m. at Crown Memorial State Beach. www.ebparks.org. Combine easy walk with guided tour of 50-ton gun, last operational gun of its kind, at San Francisco Presidio; 11 a.m. to 3 p.m. at Battery Chamberlain, north end of Baker Beach parking lot (program repeated on Sunday). www.parksconservancy.org. Guided 3.5-mile walk to identify slime molds at Monte Bello Open Space Preserve in Palo Alto foothills; meet at 12:30 p.m. at parking lot on Page Mill Road. www.openspace.org. Wetlands Day: 4-mile walk one-way with car shuttle in Petaluma River delta; meet at 10 a.m. in Novato on Binford Road at gate for Pinheiro Fire Road. www.marincountyparks.org. Sunday stroll: 4-mile walk through oak, bay and redwood forest at Roberts Regional Recreational Area in Oakland hills; meet at 10 a.m. at lower parking lot. www.ebparks.org.