Fisheries Ecology Division, Southwest Fisheries Science Center, NOAA National Marine Fisheries Service, 110 Shaffer Road, Santa Cruz, California 95060, USA.
Ecol Appl. 2012 Jul;22(5):1472-82. doi: 10.1890/11-0480.1.
We examined the response of fishes to establishment of a new flow regime in lower Putah Creek, a regulated stream in California, U.S.A. The new flow regime was designed to mimic the seasonal timing of natural increases and decreases in stream flow. We monitored fish assemblages annually at six sample sites distributed over approximately 30 km of stream for eight years before and nine years after the new flow regime was implemented. Our purpose was to determine whether more natural stream flow patterns would reestablish native fishes and reduce the abundances of alien (nonnative) fishes. At the onset of our study, native fishes were constrained to habitat immediately (<1 km) below the diversion dam, and alien species were numerically dominant at all downstream sample sites. Following implementation of the new flow regime, native fishes regained dominance across more than 20 km of lower Putah Creek. We propose that the expansion of native fishes was facilitated by creation of favorable spawning and rearing conditions (e.g., elevated springtime flows), cooler water temperatures, maintenance of lotic (flowing) conditions over the length of the creek, and displacement of alien species by naturally occurring high-discharge events. Importantly, restoration of native fishes was achieved by manipulating stream flows at biologically important times of the year and only required a small increase in the total volume of water delivered downstream (i.e., water that was not diverted for other uses) during most water years. Our results validate that natural flow regimes can be used to effectively manipulate and manage fish assemblages in regulated rivers.
我们研究了鱼类对美国加利福尼亚州下帕塔溪新水流模式形成的响应，该溪流是一条受到调控的河流。新的水流模式旨在模拟溪流流量自然增减的季节性时间。在新水流模式实施之前的八年和之后的九年，我们每年在大约 30 公里的溪流上的六个采样点监测鱼类群落。我们的目的是确定更自然的水流模式是否会重新建立本地鱼类并减少外来（非本地）鱼类的数量。在我们研究开始时，本地鱼类被限制在引水坝下游不到 1 公里的栖息地，而外来物种在所有下游采样点都占据了数量优势。在新水流模式实施后，本地鱼类在超过 20 公里的下帕塔溪中重新占据了主导地位。我们提出，创造有利的繁殖和育幼条件（例如，春季增加水流）、较低的水温、在溪流全长保持流水条件以及通过自然发生的高流量事件将外来物种排挤出去，促进了本地鱼类的扩张。重要的是，通过在一年中生物重要的时间操纵水流，仅在大多数水年需要少量增加输送到下游的总水量（即未用于其他用途的水），就实现了本地鱼类的恢复。我们的结果验证了自然水流模式可用于有效地操纵和管理受调控河流中的鱼类群落。
