MESO > Newsletters > Volume Index

Marine Environmental Update Bulletin

December 19, 2000: NMFS Proposes Range Extension for Southern California Steelhead ESU

In August 1997, the National Marine Fisheries Service listed the Southern California steelhead (Onchorhynchus mykiss) Evolutionarily Significant Unit (ESU) as an endangered species and defined its southern limit as Malibu Creek in Los Angeles County, California, based on the best information available at that time. In February 2000, the NMFS designated critical habitat for this ESU that includes all accessible and occupied waterways, including the adjacent riparian zone, below long-standing impassable natural barriers within the range of the ESU.

Based on newer information (see below), the NMFS is proposing under the Endangered Species Act to extend the current range of this endangered ESU to San Mateo Creek in northern San Diego County, California. Within the redefined Southern California steelhead ESU, only naturally-spawned populations of steelhead, and their progeny, which reside below naturally occurring and man-made impassable barriers (e.g., impassable waterfalls and dams) are proposed for listing. At this time, the NMFS is proposing to list only the anadromous life forms of O. mykiss in those river basins south of Malibu Creek.

In the original proposed listing determination for the Southern California steelhead ESU (61 FR 41541), the NMFS indicated that the current range of the ESU extended to the southernmost extent of the species range which was thought to be Malibu Creek in Los Angeles County based on the best available information. Many comments were received during the public comment period indicating that the southern boundary of the ESU should be extended further south to either the southern extent of the species historical range, the Mexican border, or some other location. The NMFS reviewed the available references to O. mykiss occurring historically and more recently in streams south of Malibu Creek and concluded in its final listing determination that there was insufficient information to revise the southern boundary of this ESU even though some information indicated that O. mykiss might occasionally occur as far south as the Santa Margarita River in San Diego County (62 FR 43937).

In February 1999, an angler reported the catch of a juvenile juvenile steelhead/rainbow trout in the lower reach of San Mateo Creek. Based on this report, the State of California Department of Fish and Game (DFG) initiated a field investigation to confirm the presence of O. mykiss in the San Mateo Creek watershed. The results of this investigation were presented in a February 2000 report prepared by DFG entitled: "Steelhead Rainbow Trout in San Mateo Creek, San Diego County, California" (DFG, 2000).

In May 2000, the DFG conducted a follow up survey in conjunction with biologists from the NMFS and the Fish and Wildlife Service in the upper portion of San Mateo Creek just above the gauging station on Camp Pendleton, including the lower reach of the tributary Devils Canyon Creek. This limited survey effort observed three (3) adult O. mykiss in the mainstem pools and approximately 15-20 juveniles in Devils Canyon Creek. DFG biologists have speculated that the larger size class of O. mykiss may be holdover fish from the population found in 1999, whereas the smaller juveniles may be the progeny of these holdover fish.

The complete text of the proposed rule is available from MESO (text only or 149 KB Adobe™ Acrobat™ file). Comments on the proposed rule must be received by February 20, 2001. Requests for public hearings must be received by February 2, 2001. Comments and requests for public hearings or reference materials should be sent to the Assistant Regional Administrator, Protected Resources Division, National Marine Fisheries Service, Southwest Region, 501 West Ocean Boulevard, Suite 4200, Long Beach, CA 90802-4213. For further information contact Craig Wingert, (562) 980-4021, or Chris Mobley, (301) 713-1401.

Federal Register, Volume 65, Number 244, Tuesday, December 19, 2000, pp. 79328-79336.