Abundance and distribution of the round stingray, Urobatis halleri, near a heated effluent outfall

Heated seawater effluent released from coastal electric-generating stations alters the abundance and distribution of organisms near an outfall. It is hypothesized that large aggregations of round stingrays, Urobatis halleri, occurring near an outfall at Seal Beach, California are attracted to the heated effluent. Stingray densities were significantly higher at Seal Beach outfall sites than at a non-outfall site at Surfside; densities were also higher within 30 m of the surfzone than 31–60 m from the surfzone. Water temperatures were higher at Seal Beach than at Surfside, and were also higher within 30 m of the surfzone than 31–60 m from the surfzone. These results suggest U. halleri prefer warmer effluent water near the surfzone at Seal Beach to cooler, ambient water further offshore. Heated effluent, reduced swell exposure, and fresh water input may mimic natural estuarine conditions and provide U. halleri with an urbanized alternative to lost natural habitat.