Ptychocheilus grandis

Invasion History

First Non-native North American Tidal Record: 1975
First Non-native West Coast Tidal Record: 1975
First Non-native East/Gulf Coast Tidal Record:

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General Invasion History:

Sacramento Pikeminnows (Ptychocheilus grandis) are a large predatory freshwater fish, native to the Sacramento-San Joaquin basin, and to the adjacent Russian River and Pajaro-Salina (Monterey Bay) basins (Page and Burr 1991; Gobalet 1993; Moyle 2002). They are a major native predator in the San Francisco Bay estuary Delta (Nobriga et al. 2006; Nobriga and Feyrer 2007). This fish was introduced to the Chorro Creek (Morro Bay), south of San Francisco Bay, and Eel River, north of the native range (Swift et al. 1993; Brown and Myle 1993). There was also an apparently failed invasion (only 7 fish captured) in the Elk River, a Humboldt Bay tributary (Kinziger et al. 2014). These introductions probably resulted from juvenile fishes in bait releases or as strays in stocked gamefishes.

North American Invasion History:

Invasion History on the West Coast:

Sacramento Pikeminnows were introduced to Chorro Creek, a tributary of Morro Bay, California, before 1975, and occur in the upper tidal regions of the bay (Swift et al. 1993). They tolerate salinities up to 8 PSU. Introduced pikeminnows are a concern as a predator of anadromous Steelhead (sea-run Rainbow Trout, Oncorhynchus mykiss). Removal programs, using electrofishing have been underway to remove, and eventually eliminate the pikeminnow population (Halligan and Otte 2011; Morro Bay National Estuarine Research Reserve 2017).

Sacramento Pikeminnows were discovered in the Eel River, in northern California, in 1979 and by 1987-1989 they were widespread through the Eel River system. They were most widespread in the mainstem of the river, but also found in the larger tributaries (Brown and Moyle 1997). Genetic studies indicate that the effective founding population was as small as three to four individuals (Kinziger et al. 2014). We have not found specific records for the estuary but assume that they occur there. The California Department of Fish and Wildlife conducted experimental removals, and private groups have organized fishing derbies in order to protect salmonid stocks, but these proved to be ineffective (Wilson 2010). In 2008, seven pikeminnows were caught in the Elk River, a small tributary of Humboldt Bay. Genetic analysis indicated that these fish were derived from the Eel River population (Kinziger et al. 2014).

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Description

Sacramento Pikeminnows (Ptychocheilus grandis) are a large, predatory freshwater fish of the family Cyprinidae. Fish of the family Cyprinidae, the carp and minnow family, have a single dorsal fin, abdominal pelvic fins, and a lateral line. They lack true spines in their fins. The four species of pikeminnows are the largest North American minnows, reaching maximum sizes of 440 mm Umpqua Pikeminnow (P. umpquae) to 1800 mm Colorado Pikeminnow (P. lucius). Pikeminnows have long conical heads, flattened between the eyes, and a large, terminal mouth, with the maxilla extending rearward of the eye. The body is slender, the caudal peduncle is narrow, and the tail is deeply forked. The Sacramento Pikeminnow has 8 dorsal and anal rays, and 65 to 78 lateral scales. This fish can reach 1150 mm but is usually 1000 to 1100mm in length. Young fish have silvery sides with a dark lateral band, and dark spot at the base of the tail. Adult fish have a gray-green back and silvery sides. Breeding fish have orange-tinted fins (Page and Burr 1991; Moyle 2002; California Fish Website 2018).

The four species of pikeminnows (Ptychocheilus spp.) are mostly confined to separate river basins in western North America (Page and Burr 1991), although the Sacramento Pikeminnow has been introduced to adjacent river basins. Pikeminnows were formerly known as 'squawfishes', a name given by white settlers, but now considered offensive. 'Pikeminnow' is more descriptive of these giant cyprinid fishes.

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Taxonomy

Ecology

General:

Sacramento Pikeminnows (Ptychocheilus grandis) are large, predatory freshwater fish. Male fish may develop nodes or tubercles on the head during the breeding season, but otherwise both sexes are morphologically similar. The fish mature at 200 to 250 mm, at an age of three to four years (Moyle 2002; California Fish Website 2018). They spawn in riffles and the tails of stream pools with gravel substrates. They tends to spawn in schools, with one female pursued by many males. The female dips close to the bottom, and releases a small batch of eggs, which are fertilized by one or several males. The eggs sink to the bottom and adhere to rocks and gravel. Females, 310 to 650 mm long, contained 15,000 to 40,000 eggs (Moyle 2002; California Fish Website 2018). Larvae remain in crevices of gravel until the yolk sac is absorbed, and then move into small streams and side pools. Juveniles move into deeper waters (Wang 1986). Sacramento Pikeminnows live for up to 16 years (Moyle 2002).

Sacramento Pikeminnows are considered warmwater fishes. They can tolerate temperatures of 30 C but prefer 18-28 C (Cech et al. 1990; California Fish Website 2018). They have been collected at 8 PSU (Halligan and Otte 2011). Typical habitats are rocky and sandy pools of small to large rivers, lakes, and reservoirs (Page and Burr 1991). They are widespread in the freshwater portions of the Sacramento-San Joaquin Delta (Feyrer and Healy 2003; Brown and Michniuk 2007; Leidy 2007) and are rare in the brackish Suisun Marsh area (Matern et al. 2002). Juvenile Sacramento Pikeminnows feed primarily on insect larvae, gradually increasing the proportion of fish from ~10% to 75% as size increases from less than 100 to more than 400 mm (Brown and Moyle 1997; Nakamoto and Harvey 2003; Nobriga et al 2006). Although the pikeminnow's predation on salmonids is a major concern to fisheries managers, other fishes were more frequent as prey in the Eel River (Brown and Moyle 1997; Nakamoto and Harvey 2003) and Sacramento-San Joaquin Delta (Nobriga et al. 2006).

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Habitats

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Life History

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Tolerances and Life History Parameters

Maximum Temperature (ºC)	30	Cech et al. 1990
Minimum Salinity (‰)	0	This is a freshwater fish,
Maximum Salinity (‰)	8	Field (Halligan & Otte 2011)
Minimum Dissolved Oxygen (mg/l)	2.1	Cech et al. 1990
Minimum Length (mm)	200	Moyle 2002
Maximum Length (mm)	1,150	Moyle 2002
Broad Temperature Range	None	Warm temperate
Broad Salinity Range	None	Limnetic-Mesohaline

General Impacts

Ecological Impacts

Sacramento Pikeminnows (Ptychocheilus grandis) are opportunistic predators on salmonids, minnows, and freshwater sculpins (Cottus asper, C. aleuticus) (Brown and Moyle 1997; Halligan and Otte 2011). In comparisons of streams with and without Pikeminnows, densities of sculpins were 21X higher in streams without pikeminnow (White and Harvey 2001).

Economic Impacts

Fisheries- Predation by Pikeminnows are a concern in the Eel River and Morrow Bay drainages, where they have been introduced (Brown and Moyle 1997). A removal program was conducted to reduce the Pikeminnow population in Chorro Creek, a Morro Bay tributary (Halligan and Otte 2011), and similar removal efforts have been attempted, but considered ineffective in the Eel River (Wilson 2010).

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Regional Impacts

P120	Eel River		Ecological Impact	Predation
Ptychocheilus grandis are opportunistic predators on salmonids, cyprinids, and freshwater sculpins (Cottus asper, C. aleuticus) (Brown and Moyle 1997). In comparisons of streams with and without P. grandis, densities of sculpins were 21X higher in streams without pikeminnow (White and Harvey 2001).
P070	Morro Bay		Ecological Impact	Predation
Predation by Ptychocheilus grandis was considered a major threat to a population of anadromous Steelhead (Oncorhynchus mykiss in Chorro Creek, a Morro Bay tributary. A removal program was conducted to reduce the Pikeminnow population (Halligan and Otte 2011). Predation by the Sacramento Pikeminnow may have also led to the extinction of the Tidewater Goby in Morro Bay (Lafferty et al. 1999).
P070	Morro Bay		Economic Impact	Fisheries
A removal program was conducted to reduce the Pikeminnow population in Chorro Creek (Halligan and Otte 2011) and is still continuing (Morro Bay National Estuarine Research Program 2017).
P120	Eel River		Economic Impact	Fisheries
Predation by Sacramento Squawfishes is a concern for management of anadromous salmon or trout, and have prompted studies of the biology and feeding of this fish (Brown and Moyle 1997).. Experimental removal efforts have been made by the California Department of Fish and Wildlife, and private groups have organized fishing derbies, but large-scale removal efforts have been considered futile (Wilson 2010).
CA	California		Ecological Impact	Predation
Predation by Ptychocheilus grandis was considered a major threat to a population of anadromous Steelhead (Oncorhynchus mykiss in Chorro Creek, a Morro Bay tributary. A removal program was conducted to reduce the Pikeminnow population (Halligan and Otte 2011). Predation by the Sacramento Pikeminnow may have also led to the extinction of the Tidewater Goby in Morro Bay (Lafferty et al. 1999)., Ptychocheilus grandis are opportunistic predators on salmonids, cyprinids, and freshwater sculpins (Cottus asper, C. aleuticus) (Brown and Moyle 1997). In comparisons of streams with and without P. grandis, densities of sculpins were 21X higher in streams without pikeminnow (White and Harvey 2001).
CA	California		Economic Impact	Fisheries
A removal program was conducted to reduce the Pikeminnow population in Chorro Creek (Halligan and Otte 2011) and is still continuing (Morro Bay National Estuarine Research Program 2017)., Predation by Sacramento Squawfishes is a concern for management of anadromous salmon or trout, and have prompted studies of the biology and feeding of this fish (Brown and Moyle 1997).. Experimental removal efforts have been made by the California Department of Fish and Wildlife, and private groups have organized fishing derbies, but large-scale removal efforts have been considered futile (Wilson 2010).

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