Understanding Fish Habitat in a Tidally Restricted Urban Lagoon Website
Our overall project objective is to determine how and to what degree several economically important fish species utilize a newly-dredged urban lagoon that is only connected to a neighboring bay with a culvert. We will assess this by monitoring the movement patterns, physical conditions, sediment quality, water flow patterns, and available food items within the lagoon and the culvert area of the neighboring bay. While the use of culverts in urban areas is common, the degree to which different species will transit culverts to access new habitat is poorly known. Since fish are often caught in the lagoon and must transit the culvert to assess this habitat, the degree to which they move back and forth is also unknown. If the culvert poses a movement barrier, then it is possible that fishes can find their way into the Lagoon but may have a more difficult time finding their way out. Rapidly changing environmental conditions in the Lagoon could then pose a threat to fishes if they readily cannot find their way out. In addition, our proposed methodology will enable us to quantify the site fidelity to the lagoon, which can be a valuable tool for assessing functional recovery of the ecosystem post-removal of the culvert.
Specifically, we will 1) describe potential fish habitat within the lagoon with respect to physical parameters (water temperature, salinity, turbidity, dissolved oxygen), food sources (phytoplankton, zooplankton, small fish), and sediment characteristics (grain size and organic matter) and 2) monitor fish movement of certain species in and out of 880-foot long culvert connecting Alamitos Bay to CO Lagoon (pre-removal of the culvert). Our proposal combines traditional hydrological and physical measurements (using continuous water quality loggers) and food source quantification (using chlorophyll a, zooplankton tows, and seines) with novel fish movement methods (using passive tagging) to understand fish utilization of a tidally restricted lagoon.
Our site location in the heart of urban Long Beach offers a unique opportunity to obtain detailed information on key ecosystem processes in a field site of local, regional and national interest. Additionally, the short-term management of this marsh will be informed by our results. The different data gathered from carefully designed tagging studies is used to guide management decisions and provide feedback on how a particular action (in this case, eventual conversion from a culvert to an open channel) has improved conditions for fish. More information is needed about functional recovery of estuaries from activities such as dredging and culvert removal. This grant also represents an exciting opportunity to integrate science into the existing education curriculum at the Lagoon.
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