Floodplain farm fields provide novel rearing habitat for Chinook salmon

Abstract

When inundated by floodwaters, river floodplains provide critical habitat for many species of fish and wildlife, but many river valleys have been extensively leveed and floodplain wetlands drained for flood control and agriculture. In the Central Valley of California, USA, where less than 5% of floodplain wetland habitats remain, a critical conservation question is how can farmland occupying the historical floodplains be better managed to improve benefits for native fish and wildlife. In this study fields on the Sacramento River floodplain were intentionally flooded after the autumn rice harvest to determine if they could provide shallow-water rearing habitat for Sacramento River fall-run Chinook salmon (Oncorhynchus tshawytscha). Approximately 10,000 juvenile fish (ca. 48 mm, 1.1 g) were reared on two hectares for six weeks (Feb-March) between the fall harvest and spring planting. A subsample of the fish were uniquely tagged to allow tracking of individual growth rates (average 0.76 mm/day) which were among the highest recorded in fresh water in California. Zooplankton sampled from the water column of the fields were compared to fish stomach contents. The primary prey was zooplankton in the order Cladocera, commonly called water fleas. The compatibility, on the same farm fields, of summer crop production and native fish habitat during winter demonstrates that land management combining agriculture with conservation ecology may benefit recovery of native fish species, such as endangered Chinook salmon.

Headwater Streams and Wetlands are Critical for Sustaining Fish, Fisheries, and Ecosystem Services

“…The science of waterbody connectivity has advanced markedly in the time since the Rapanos case, and the 2015 Clean Water Rule was based on the demonstrated importance of physical, chemical, and biological connections of headwaters to the ecological condition of navigable waters and their biota (Leibowitz et al. 2018).…”

“…Examples include federally listed Coho Salmon and Chinook Salmon, species with juveniles that occupy headwater tributaries and seasonal floodplain wetlands during winter. During the rest of the year, these habitats are either dry or so small that they are not considered suitable salmon habitat (Brown and Hartman 1988;Sommer et al 2001;Jones et al 2014;Katz et al 2017; Woelfle-Erskine et al 2017). Nonetheless, these intermittent habitats can play a critical role in recruitment.…”

Growth and recruitment dynamics of young‐of‐year northern pike: Implications for habitat conservation and management

“…Overcoming these three challenges-achieving sufficient growth to overwinter, enabling interactions with other species, and loss of spawning and nursery habitats,-will necessitate coordination and partnerships beyond the traditional fishery and conservation communities (Katz et al, 2017;Sass, Rypel, & Stafford, 2017).…”

Debunking myths about Aldo Leopold's land ethic

“…The Yolo Bypass serves a variety of functions: it has provided flood control that has "saved valley communities numerous times" (Sommer et al 2001, 9); it has allowed for seasonal agriculture in the late spring and summer, with crops such as sugar beets, rice, safflower, and corn (Sommer et al 2001); it includes large areas of wetlands that are managed to provide habitat for migratory waterfowl and which also provide habitat for various species of shorebirds, raptors, songbirds, and mammals, including threatened species (Sommer et al 2001); it is used for recreation and education (bird-watching, hiking, guided tours); and it provides key aquatic habitat for 42 fish species, including 15 native fish species, some of which are threatened or endangered (Sommer et al 2001). Recent studies have focused on whether winter's flooded rice fields can serve as a rearing area for juvenile salmon; results are promising thus far (Katz et al 2017).…”

“…Proponents acknowledge improvements could be made to Yolo Bypass's design, and also, that the approach would not work in all regions (Sommer et al 2001), although others maintain that "the potential of managing a working agricultural landscape for the combined benefits to fisheries, farming, flood protection, and native fish and wildlife species…should have broad applicability for the management of floodplains throughout California and beyond" (Katz et al 2017). In any case, it seems to be an exemplar of restoration and conservation, with multiple benefits to humans and non-human species.…”