hour rate for redbreast sunfish was 123, the highest of several warmwater streams tested during the survey. Some stocked rainbow trout and brown trout were also captured in the creek. High numbers of American eels were observed in the creek was well. Fish species such as mummichogs, silvery minnows, striped bass, and white perch were found at the head-of-tide of the creek. Brown trout naturally reproduce in the creek's headwaters. The Ithan-Darby Creek Wetlands and the Darby Creek Mouth Mudflat are listed on the Delaware County Natural Areas Inventory. The former is a "notable significance" site while the latter is an "exceptional significance" site, one of only four in Delaware County. The John Heinz National Wildlife Refuge is also in the vicinity of the creek and is an "exceptional significance" site. The Darby Creek Mouth Mudflat, which is a remnant tidal flat at the mouth of Darby Creek in Ridley Township and Tinicum Township, is inhabited by 14 "species of concern". At the John Heinz National Wildlife Refuge, which is a tidal estuary along the creek, supports various plant and animal species and is a critical migratory habitat for waterfowl. It is also designated as a National Wildlife Refuge. The Ithan-Darby Creek Wetlands contain old fields, wet meadows, and riparian buffers. They are inhabited by one "species of concern". The population of white-tailed deer in the Darby Creek watershed is large and "ecologically unsustainable", according to the U.S. Fish and Wildlife Service. Plant species of concern at the Darby Creek Mouth Mudflat include Amaranthus cannabinus, Baccharis halimifolia, Bidens bidentoides, Bidens laevis, Eleocharis obtusa, Eleocharis parvula, Heteranthera multiflora, Lycopus rubellus, Pluchea odorata, Sagittaria calycina, Sagittaria subulata, Schoenoplectus fluviatilis, and Zizania aquatica. Some, such as Eleocharis obtusa, Eleocharis parvula, and Heteranthera multiflora, have not been seen since 1994. However, four other species have been seen as recently as 2009. At the floodplain at the confluence of Ithan Creek and Darby Creek, the main trees species include silver maple, black willow, boxelder, and red maple. In the wetlands at this site, the main tree species include scattered black willow and silver maple. There are also patches of silky dogwood and wild rose, which are surrounded by assorted wetland plants, including herbs, grasses, sedges, and rushes. However, numerous exotic plants also inhabit the site. The watershed of Darby Creek and several other nearby creeks house most of the herptiles in Delaware County. The macroinvertebrate