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Study: Sarasota stormwater system can support snook, bass and more

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Dozens of fish species — including common snook and largemouth bass — use certain parts of the upper Phillippi Creek system, according to the first fish survey of this urbanized network of canals, retention ponds and wetlands in Sarasota County, Florida.

The survey — led by Mote Marine Laboratory and funded by Sarasota Bay Estuary Program (SBEP) — found the highest numbers and diversity of fishes around upper creek areas mimicking natural habitat: curving canals or ponds with wetland vegetation and sections of slower-moving water. Less naturalistic canals, with shorelines straightened for optimum drainage, generally hosted fewer fish of fewer species.

Urban waterways can lose ecosystem value — for example, ability to support economically important sport fish — due to pollution, altered water flow and loss of natural habitat. Scientists around the nation are investigating how to help these waterways better serve wildlife, ecosystems and communities. Phillippi Creek drains approximately 60 square miles (145 square kilometers) of Sarasota County land, with downstream waterways richer in natural habitat and upstream waterways bearing a clearer human fingerprint: more straightened, channelized canals, sediment traps and retention ponds.

“We want to understand how to balance the role of these waterways between stormwater management and ecosystem function,” said Mote staff scientist Dr. Jim Locascio. “Can upper Phillippi Creek be enhanced to benefit fish without sacrificing its performance as a drainage system? That’s what we hope our survey results will lead into. First we needed to learn how the system is functioning and understand whether some creek areas are more productive in supporting fish.”

“Typical stormwater drainage systems were designed to transport excess water directly from residential areas to the sea; this concentrates flow through a narrow area,” said Mote Staff Scientist Dr. Nate Brennan, who was also involved in the project. “Such systems can experience flash-flooding as well as very reduced flow, and they can transport nutrient-laden sediment downstream, all of which affects how many species can survive in the canals themselves and in downstream ecosystems such as estuaries and seagrass flats. However, slower and more consistently flowing waterways can be refuges with higher diversity of prey animals as well as high-value, predatory fish such as snook and largemouth bass. Upper Phillppi Creek is dominated by straightened canals, but it also includes good refuge areas and sites with potential to create more; that really interests us.”

Since the 1980s, Sarasota County has significantly enhanced its measures to prevent floods and enhance water quality, most commonly using wet ponds. Ponds help delay the discharge of runoff, capture sediments and protect downstream ecosystems. County officials and Mote scientists each want to know whether further enhancements will help support fisheries.

Based on discussions with Sarasota County and SBEP staff, Mote scientists surveyed fish and select invertebrates (such as shrimp) at about 70 sites – most along upper Phillippi Creek, north of Bahia Vista Street and east of Beneva Road, and one downstream from this junction: Red Bug Slough preserve. Sites represented three habitat types: canals with generally straightened shorelines maintained to drain storm water; secondary stage canals with more bent shorelines, restored wetland areas, a natural preserve and sediment traps; and retention ponds known as the Celery Fields.