Ebook Pennsylvania Coastal Zone Management Program
The flathead catfish (Pylodictes olivaris) is native to the Mississippi River drainage and some other Gulf of Mexico watersheds, however, introduced populations have become established in a number of drainages in the Southeastern United States (Kwak et al. 2004, Jackson 2000, Moser and Roberts 1999, Dobbins et al. 1999) reaching relatively high densities for a predatory fish. Major effects on sunfishes (Lepomis and related species), catfishes and bullheads (Ictalurus and Amieurus), minnows, and herrings populations (Ashley and Buff 1987, Thomas 1995, Odenkirk et al. 1999, Moser and Roberts 1999) have been observed. As a result, rigorous control programs have been instituted in a number of areas. For example, intensive electrofishing in the Satilla River, GA, aimed at keeping the flathead catfish (FCF) population from gaining community dominance, has reduced the average size of FCF, although abundance remains high (Harrison 2004).
Flathead catfish were first documented in the Delaware River drainage in 1997, when a pair was caught in Blue Marsh Reservoir (Mike Kaufmann, Pennsylvania Fish and Boat Commission, personal communication). FCF were first observed in the Schuylkill River Fishway in 1999 (at the Fairmount Dam) during a routine cleaning. Since this discovery of flatheads in the Philadelphia area, they have been reported in several additional Schuylkill River locations. Only a few reports have been confirmed in the main stem of the Delaware River. Anglers now report catching FCF below the Holtwood and Safe Harbor dams on the Susquehanna River.
The abundance of flathead catfish is often difficult to estimate because of low capture efficiencies using many standard large fish collection techniques, such as, high frequency boat electrofishing (e.g., Stauffer and Koenen 1999). Flathead catfish are also not as frequently caught in traps with scented baits as channel catfish (Ictalurus punctatus), presumably because of their preference for live food. Similarly, FCF are not typically caught on scent baits and other hook-and-line baits commonly used by anglers to catch channel catfish and bullheads. A number of targeted sampling techniques have been employed with limited success including low frequency electrofishing (Stauffer and Koenen 1999, Gilliland 1987, Harrison 2004), unbaited hoop nets, and rod-and-reel using live fish bait; resulting catch rates were often low and some of these techniques show size selectivity. The effectiveness of these techniques also seems to vary with environmental conditions (e.g., temperature and water conductivity), season, and biological status of the fish.
In 2002, the Introduced Flathead Catfish Pilot Study was initiated out of a desire to better understand the impact populations of introduced FCF might have on Delaware Estuary fisheries. This study represents a cooperative effort of the Pennsylvania Flathead Catfish Consortium, comprised of Pennsylvania Sea Grant (PASG, Sea Grant), the Philadelphia Water Department (PWD, the Water Department), the Monell Chemical Senses Center (MCSC, Monell Center) and the Academy of Natural Sciences of Philadelphia (ANS, the Academy), in cooperation with the Pennsylvania Fish and Boat Commission. Because of the negative impacts introduced FCF have had on native fish communities in other areas of the country, the consortium felt it was important to investigate possible population control strategies.
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