Chesapeake Bay Introduced Species Database


Pylodictis olivaris

Common name(s):
Flathead Catfish
Flathead Catfish are giant fish (up to 60 inches, 130 lbs), and very popular among anglers because of their size and tastiness. They are native to Mississippi and Gulf drainages. These catfish have been stocked or otherwise released into drainages in 18 states. The first Chesapeake release in 1965 was accidental; the Virginia Division of Fish and Game was keeping them in ponds on Hog Island Game Refuge for research when about 50 fish escaped into the James River during a flood. Although only a few fish were released at that time they established sustaining populations. Similarly, only 12 fish were stocked in the Occoquan Reservoir, but that was enough to establish a population. Populations of flathead catfish have been found in many other areas of the Chesapeake watershed, including the Susquehanna River, and it is suspected that small numbers of fish were released by anglers due to their popularity as a sport fish. This species? ability to colonize river systems, as well as its role as a top predator with an enormous appetite, means that unauthorized stockings by fisherman are a serious problem.
Image courtesy of Eric Engbretson, U.S. Fish and Wildlife Service.



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Environmental Tolerances

 
For Survival
For Reproduction
Minimum
Maximum
Minimum
Maximum
Temperature (ºC)
null null 22 23.9
Salinity (‰)
0 14 0 null
Oxygen
hypoxic      
pH
null null    
Salinity Range
fresh-meso


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Age and Growth

Male
Female
Minimum Adult Size (mm)
380 485
Typical Adult Size (mm)
700 700
Maximum Adult Size (mm)
1400 1410
Typical Longevity (yrs)
12 12
Maximum Longevity (yrs)
24 24


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Reproduction

Start
Peak
End
Reproductive Season
June June July
Typical Number of Young
per Reproductive Event
9100
Sexuality Mode(s)
dioecious
Mode(s) of Asexual Reproduction
Fertilization Type(s)
outcross-external
More than One Reproductive
Event per Year
no
Reproductive Strategy
iteroparous
Egg/Seed Form
demersal, epibenthic


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Development

Minimum Typical Maximum
Egg/Seed Development Time (days)
null 6.5 null
Larval/Seed Development Period (days)
null null null
Male Maturation Age (yrs)
2 4  
Female Maturation Age (yrs)
3 5  
Larval/Seed Form  
lecithotrophic


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Locomotion and Abundance in Chesapeake

Locomotion
Abundance
Larvae
sedentary rare
Juveniles
nektonic rare
Adults
nektonic rare


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Habitat Preferences

Larvae
Juvenile
Adult
Primary Horizontal Habitats
coarse woody debris; grass beds; rocky; nontidal freshwater unstructured; nontidal freshwater coarse woody debris; unstructured; nontidal freshwater
Secondary Horizontal Habitats
fresh (non-tidal) marsh; fresh tidal marsh fresh (non-tidal) marsh; fresh tidal marsh fresh (non-tidal) marsh; fresh tidal marsh
Reproductive Horizontal Habitats
n/a n/a coarse woody debris; grass beds; rocky; nontidal freshwater
Vertical Habitats
epibenthic nektonic nektonic
Substrate Type
clay; mud; sand; gravel; cobble; boulder; rock clay; mud; sand; gravel; cobble; boulder; rock clay; mud; sand; gravel; cobble; boulder; rock
Tidal Height Location
subtidal subtidal subtidal
Wave Exposure
moderate; low; protected
Water Flow
slow; fast; stagnant


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Trophic Interactions

Larvae
Juveniles
Adults
Trophic Status
non-feeding omnivore omnivore
Common Food/Prey Items
nonfeeding insect larvae; fish; crayfish; microcrustaceans crayfish; crabs; bivalves; fishes (Ictalurus furcatus; Ictalurus punctatus; Ictalurus nebulosus; Lepomis macrochirus; Pomoxis nigromaculatus; Dorosoma cepedianum; Alosa sapidissima; Paralichthys)
Common Competitors
Common Consumers
predatory fishes; crayfish predatory fishes; birds; otters humans


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Comments

Life History: Envirnmental Tolerances: Temperature- This species' preferred temperature in a thermal gradient was 31.5-33.5 C (Goodchild 1993). The temperature range fro reproduction was observed in WI (Goodchild 1993) Salinity- Pylodictus olivaris in VA estuaries occasionally occurs at salinities above 5 ppt (Murdy et al. 1997). In NC, this fish has been collected at salinities as high as 6 ppt (Pennsylvania Fish and Boat Commission 2002). Some fish in the Cape Fear estuary NC, had Paralichthys lethostigma (Southern Flounder) and Callinectes sapidus (Blue Crabs) in their gut contents (Ashley and Buff 1997; Guier et al. 1981). The initial site of their accidental release at Surry VA (Burkhead et al. 1980) is in the oligohaline-low mesohaline zone. In experimental tests, the mean 96-h survival level was 14.5 ppt for fishes transferred directly from fresh to synthetic seawater (Bringole et al. 2005).

Age and Growth: Adult Size- The data on minimum adult size came from KS (Carlander 1969) . The largest known specimens weighed at least 31,000 g (Jenkins and Burkhead 1993), and the VA record 25,900 g (Jenkins and Burkhead 1993). Longevity - 'Typical' values are somewhat arbitrary. The number of fishes in samples, and the frequency of samples, measured in various places, steadily decline with estimated age. Four locations had fishes at age-class X, 8 batches of 1-4 fish were reported at age-class XII, but very few fish were found over age-class XV (Carlander 1969). Reproduction: Typical Number of Young per Reproductive Event- The range is 4,076 to 100,000 eggs per female (Goodchild 1993). Development: Egg Development Time- Egg development was observed at 24-28 C (Jenkins and Burkhead 1993). Maturation Age: The rate of maturation varies geographically and with temperature and feeding conditons. The range has been given as 4-6 years (Jenkins and Burkhead 1993) or 2-5 years (Munger et al. 1994). Locomotion and Abundance- Abundance- Very few small juveniles of this species are captured; they inhabit the runs and riffles of rivers (Jenkins and Burkhead 1993). Adults are 'rare to uncommon' (Jenkins and Burkhead 1993). Other Life History Features- Pylodictis olivaris has a striking ability to start populations from small groups of individuals. James River and Occoquan Reservoir populations started from ~ 50 and 12 individuals, respectively (Jenkins and Burkhead 1993). An Altmaha River, GA population started from a presumably small unauthorized stocking (Thomas 1993) and a Cape Fear River, NC population started from 11 fish (Guier et al. 1981).
Community Ecology: Habitat Preferences: Primary Horizontal Habitats- Larvae stay in a nest guarded by adults 'near cover or in a cavity' (Jenkins and Burkhead 1993). Juveniles occur in streams, young and juveniles are usually associated with riffles' (Jenkins and Burkhead 1993). Adults are found in 'Moderate to deep pools' (Jenkins and Burkhead 1993), and 'pools with logs and other debris' (Page and Burr 1991). Estuarine habitat preferences have not described. Substrate Type- This catfish prefers 'hard or only slightly silted bottoms' (Jenkins and Burkhead 1993). Other Habitat Conditions- This fish is tolerant of turbidity, but prefers hard bottoms (Jenkins and Burkhead 1993).

Trophic Interactions: Food/Prey - Insect larvae predominate in fish <100 mm; more fish and crayfish are found in 100-250 mm fish (Carlander 1969; Jenkins and Burkhead 1993). Stomach contents of Cape Fear River, NC adults by frequency are: 46% fish; 38% bivalves; 12% insects; 4% crustacea. However, the contents are 99.4% fish by weight (Guier et al. 1981).


This data was last modified on Friday, February 25th, 2011.
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