Habitat Associations and Behavior of Adult and Juvenile Splittail (Cyprinidae: Pogonichthys macrolepidotus) in a Managed Seasonal Floodplain Wetland

Abstract

Although there is substantial information about the benefits of managed seasonal wetlands to wildlife, little is known about whether this habitat can help support “at risk” native fishes. The Sacramento splittail Pogonichthys macrolepidotus, a California Species of Special Concern, does not produce strong year classes unless it has access to floodplain wetlands of the San Francisco Estuary and its tributaries. Our study examined the potential use of managed inundation to support spawning and rearing of splittail in years when the availability of seasonal habitat is limited. Wild adult splittail were captured during their spawning migration and transferred to a 3.8-ha engineered wetland, where they successfully spawned shortly after introduction. Radio telemetry studies suggested that post-spawning adults were relatively sedentary over the study period. Adult splittail were primarily located in habitats with open water or light vegetation, and in the deepest portions of the wetland. Snorkel surveys showed that early stages (mean 21-mm fork length [FL]) of young splittail produced in the wetland were strongly associated with shallow areas with shoreline emergent terrestrial vegetation and submerged aquatic vegetation, but moved offshore to deeper areas with tules and submerged terrestrial vegetation at night. Larger juveniles (mean 41-mm FL) primarily used deeper, offshore habitats during day and night. At night, schools of both younger and older juveniles dispersed, and individuals were associated with the bottom of the water column. These observations have important implications for the construction of managed and restored wetlands for the benefit of native fishes.

Use of a Managed Flow Pulse as Food Web Support for Estuarine Habitat

“…Examples of targeted flow actions in the San Francisco Estuary include: (1) managed seasonal inundation experiments in Yolo Bypass to support native fish rearing (Katz et al 2017;Sommer et al , 2020b; (2) a summer 2018 effort to direct more low-salinity flow into Suisun Marsh-a key region in the system for many species-using a unique water control structure (Sommer et al 2020a); and (3) the North Delta flow action described in the current study. However, there is a major conceptual difference between the Suisun Marsh (Sommer et al 2020a) and Yolo Bypass (Sommer et al 2008(Sommer et al , 2020b experiments and the current effort. The North Delta flow action represents a rare but increasingly important example of a targeted action in a specific geographic region of the estuary.…”

Climate Change Impacts on San Francisco Estuary Aquatic Ecosystems: A Review

“…As an example, agricultural areas could be modified in several ways to improve their value for juvenile salmon rearing (e.g., Herbold et al 2018). Managed flooding has also been examined on a pilot scale for other species such as Sacramento Splittail (Sommer et al 2002(Sommer et al , 2008.…”