Invasive Aquatic Species with the Potential to Affect the Great Sacandaga Lake Region
Tiffini M. Burlingame, Research Associate Lawrence W. Eichler, Research Scientist Charles W. Boylen, Associate Director Darrin Fresh Water Institute 5060 Lakeshore Drive Bolton Landing, NY 12814 TABLE OF CONTENTS
FISH
Alewife (Alosa pseudoharengu)s 3 Goldfish (Carassius auratus) 5 Northern Snakehead (Channa argus) 7 Grass Carp (Ctenopharyngodon idella) 9 Eurasian Ruff (Gymnocephalus cernuus) 11 Brook Silverside (Labidesthes sicculus) 13 White Perch (Morone americana) 15 Round Goby (Neogobius melanostomus) 17 Rainbow Trout (Oncorhynchus mykiss) 19 Sea Lamprey (Petromyzon marinus) 21 White Crappie (Pomoxis annularis) 23 Tubenose Goby (Proterorhinus marmoratus) 25 Brown Trout (Salmo trutta) 27 European Rudd (Scardinius erythrophthalmus) 29 Tench (Tinca tinca) 31
PLANTS & ALGAE
Ribbon Leaf Water Plantain (Alisma gramineum) 34 Flowering Rush (Butomus umbellatus) 36 Fanwort (Cabomba caroliniana) 38 Rock Snot (Didymosphenia geminata) 40 Brazilian Elodea (Egeria densa) 42 Water Hyacinth (Eichhornia crassipes) 44 Hydrilla (Hydrilla verticillata) 46 Frogbit (Hydrocharis morsus-ranae) 48 Yellow Flag Iris (Iris pseudacorus) 50 Purple Loosestrife (Lythrum salicaria) 52 Water Clover (Marsilea quadrifolia) 54 Parrot Feather (Myriophyllum aquaticum) 56 Variable Leaf Milfoil (Myriophyllum heterophyllum) 58 Eurasian Water Milfoil (Myriophyllum spicatum) 60 Southern Naiad (Najas guadalupensis) 62 Brittle Naiad (Najas minor) 64 Starry Stonewort (Nitellopsis obtusa) 66 Yellow Floating Heart (Nymphoides peltata) 68 Common Reed (Phragmites australis) 70 Water Lettuce (Pistia stratiotes) 72 Curly Leaf Pond Weed (Potamogeton crispus) 74 Water Chestnut (Trapa natans) 76 Swollen Bladderwort (Utricularia inflata) 78
MOLLUSKS
Mud Bithynia (Bithynia tentaculata) 81 Chinese Mystery Snail (Cipangopaludina chinensis) 83 Asian Clam (Corbicula fluminea) 85 Quagga Mussel (Dreissena bugensis) 87 Zebra Mussel (Dreissena polymorpha) 89 Piedmont Elimia Snail (Elimia virginica) 91 Wabash Pigtoe (Fusconaia flava) 93 Buffalo Pebblesnail (Gillia altilis) 95 Greater European Pea Clam (Pisidium amnicum) 97 European Ear Snail (Radix auricularia) 99 Atlantic Rangia (Rangia cuneata) 101 European Fingernail Clam (Sphaerium corneum) 103 European Stream Valvata (Valvata piscinalis) 105 Banded Mystery Snail (Viviparus georgianus) 107
ARTHROPODS Chinese Mitten Crab (Eriocheir sinensis) 110 Freshwater Shrimp (Gammarus fasciatus) 112 Asian Shore Crab (Hemigrapsus sanguineus) 114 Rusty Crayfish (Orconectes rusticus) 116
ZOOPLANKTON Spiny Waterflea (Bythotrephes longimanus) 119 Fish-hook Waterflea (Cercopagis pengoi) 121 Daphnia (Daphnia lumholtzi) 123 Eubosmina Waterflea (Eubosmina coregoni) 125 Calanoid Copepod (Eurytemora affinis) 127 Calanoid Copepod (Skistodiaptomus pallidus) 129
PATHOGENS AND PARASITES Parasitic Copepod (Argulus japonicus) 132 Viral Hemorrhagic Septicemia 134
Invasive Aquatic Species
Invasive aquatic species are exotic or non-native organisms living in, on or near water that have the potential to alter habitats, outcompete native species and seriously interfere with recreational and industrial water users. These species are often transported and introduced, either intentionally or unintentionally, thru human activities, generally with disastrous consequences. The following organisms are either currently present in Great Sacandaga Lake or present in the Northeast region with the potential to reach Great Sacandaga Lake in the foreseeable future. Preventing the introduction of these species is the only foolproof method to control their spread. An educated population provides the most effective means to minimize the impact of invasive species.
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Fish
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Alosa pseudoharengus Alewife
Habitat: Alewives are known to occupy all strata of a land-locked water body during the course of the year. Alewives have been found to prefer rocky habitats to sand sites. This may be related to their feeding on emerging insects associated with rocky areas. The majority of their time is spent in the limnetic zone. In late spring and summer they move into littoral areas for spawning and move into deeper water during fall. Alewives have a preference for warmer waters. Alwives move in large schools and are attracted to light. They move into shallow areas at night and return to deeper waters during the day.
Description: Adult alewife is typically 10 to 12 inches in length (25 to 30 cm), with a green back and silvery belly; they have a single black spot located behind the eye. Scales line up in a row along the belly. The alewife is mostly a filter feeder, but has been known to be piscivorous, feeding on fry as large as 50mm.
Principal Modes of Transport & Introduction: It is believed that the illegal stocking of alewives for forage is what fist introduced them to landlocked lakes. They may also be spread by fishermen using them as bait.
Annual Cycle: Landlocked alewives move from deep water to shallow beaches in lakes or move up streams to ponds to spawn in spring. Females usually move to the spawning areas just before the males. Spawning takes place at night in groups of two or three over a sandy or gravelly bottom. Freshwater females deposit 10,000-12,000 eggs. Eggs are broadcast randomly, are demersal (that is, they sink), and are not particularly adhesive. Adults leave the spawning area after spawning; no care is given eggs or young by the adult fish. In less than a week, the young alewives hatch to begin feeding on minute, free-floating plants and animals. By fall, the young alewives make their way back to the deep waters of lakes. Landlocked alewives reach an average length of about 6 inches when adults.
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Look Alike: The blue-back herring (A. aestivalis) is a physically similar species, and it is difficult to distinguish between the two. The only definable difference (alewife tend to have larger eyes, and blueback herrings have more "compressed" bodies, but these are difficult to enumerate unless directly comparing the two species in hand) is the color of the peritoneum in the two species. The abdominal cavity in the blueback herring is much darker, almost black, whereas the alewife has a paler abdominal cavity with some black spots.
Distribution:
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Carassius auratus Goldfish
Habitat: In the wild, goldfish can be found in slow-moving, freshwater bodies of water with cold water and aquatic vegetation. As with their close relative the carp, they thrive in slightly sludgy water. Able to withstand prolonged exposure to salinities above 15 ppt and can tolerate low levels of dissolved oxygen.
Description: Goldfish are small to moderately-sized fish with a deep body and rounded cross-section. They have a large head and eyes with a small mouth and a forked tail. Scales are large and the single dorsal fin has 3-4 stout spines at the leading edge. Color ranges from olive-bronze to deep golden along dorsal surface, fading to silvery-white along the belly. May grow up to 41cm in length, 2kg in weight and live for 30 years in captivity.
Principal Modes of Transport & Introduction: It is believed that most infestations are the result of people dumping aquariums or ornamental ponds into the lakes.
Annual Cycle: Spawning occurs in shallow water amongst weeds, and up to several hundred thousand small eggs (1-2mm diameter) are laid at once. Individual fish can spawn 3-10 lots of eggs at intervals of 8-10 days. Cold water during winter is essential for proper ova development.Eggs hatch in around a week. Young attach to aquatic plants for several days while yolk sac is absorbed.
Look Alike: Goldfish most closely resembles the Common Carp and Crucian Carp.
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Distribution:
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Channa argus Northern Snakehead Fish
Habitat: The Northern snakehead prefers stagnant shallow ponds or swamps with mud substrate and aquatic vegetation; slow muddy streams. Also occurs in canals, reservoirs, lakes, and rivers. It appears to occupy waters, usually with vegetation, close to shore, and also feeds in schools. The northern snakehead has been reported to be an obligate air breather, which means that it can live in oxygen-depleted waters by gulping air at the water's surface and survive several days out of water if kept moist.
Description: A long, thin fish with a single dorsal fin running the length of the fish. This species also has a single long anal fin similar to our native species, the bowfin (Amia calva). Overall color is brown with dark blotches. It has a somewhat flattened head with eyes located in a dorsolateral position on the anterior part of the head; anterior nostrils are present and tubular; dorsal and anal fins are elongated, and all fins are supported only by rays. The maximum size exceeds 85 cm.
Principal Modes of Transport & Introduction: This fish is popular in the Asian food market and most introductions are likely released for this purpose. The snakehead may move in stream and river networks, reproducing and spreading to adjacent watersheds.
Annual Cycle: This species reaches sexual maturity in 2 to 3 years at approximately 30-35 cm (12-14 inches) in length. Females release 1,300 to 15,000 eggs per spawn, which can occur 1 to 5 times per year. The floating eggs take 28 hours to hatch at 31oC, 45 hours at 25oC and much longer at cooler temperatures. Larvae remain in a nest guarded by their parents until yolk absorption is complete at approximately 8 mm in length. At approximately 18 mm the young begin feeding on small crustaceans and fish larvae.
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Look Alike: The Northern snakehead is very similar in appearance to the native bowfin.
Distribution:
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Ctenopharyngodon idella Grass Carp
Habitat: Grass carp inhabit sub-tropical and temperate climates and prefer large rivers, lakes, and reservoirs with abundant vegetation and relatively shallow waters. They are tolerant of a range of conditions may inhabit temperatures of 0-33° C, oxygen levels as low as 0.5 ppm, and salinities as great as 10 ppt.
Description: Grass carp has an oblong, slender body, a wide scaleless head, and very short snout. It is dark gray, silver, to olive in color with lighter sides and clear to gray-brown fins. It bears large cycloid scales with dark edges. Its dorsal fin bears 7-8 rays, anal fin 7-11 rays, and caudal fin about 18 rays. They are among the largest of the minnow family reaching weights of 30-50 kg and lengths of over a meter . Principal Modes of Transport & Introduction: In the U.S., grass carp were (and are still) often introduced to control submersed aquatic weeds. Grass carp can be used as part of an integrated management program to control aquatic vegetation, and they are a long-term control method that is relatively inexpensive and provides highly effective control for certain species. Grass carp can have harmful effects such as consuming all the vegetation, including desirable species.
Annual Cycle: Spawning occurs in summer months prompted by rising water levels of about 20cm or more and water temperatures of around 20° C. Grass carp migrate long distances to seek turbulent waters in which to spawn. Eggs are pelagic and left to drift downstream. They must remain suspended during their incubation and are very much dependant on adequate oxygen flow, therefore usually require long river stretches of turbulent rising waters. Since they require these conditions for spawning, they are not able to reproduce in many introduced habitats. Grass carp have a tremendous reproductive capacity with females producing 500,000-700,000 eggs and over 1,000,000 eggs in its native range. Eggs hatch within 2-3 days. Pelagic larvae emerge and seek shelter in vegetated areas of flood plains, reservoirs, and lakes. They may winter in deep holes within riverbeds. Males reach sexual maturity around the age of two years, while females take about three. Grass carp and may live as long as 30-50 years.
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Look Alikes: The Grass Carp can be distinguished from native cyprinids by the position of its anal fin, which is set far back on the body and the deep lateral grooves in its pharyngeal teeth . Native cyprinids have an anal fin that is more anterior than that of the Grass Carp, and have pharyngeal teeth that lack deep lateral grooves. The Grass Carp closely resembles Black Carp, but can be distinguished by its pharyngeal teeth and (in most cases) body color. The Grass Carp has long, serrated pharyngeal teeth (sometimes with hooks) whereas those of adult Black Carp are smooth and molariform. Adult Grass Carp are lighter in color than Black Carp, especially the fins.
Distribution:
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Gymnocephalus cernuus Eurasian Ruffe
Habitat: The Eurasian Ruffe can tolerate a wide range of ecological and environmental conditions. They are found in fresh and brackish water (with salinity up to 12ppt) and occur at depths varying from 0.25m to 85m. They are also able to thrive in eutrophic conditions
Description: Eurasian Ruffe is small, reaching up to 20cm in length, with olive brown coloring on the back and pale sides. They have spiny dorsal and anal fins. They are a bottom-dwelling fish. Under its spiny head, there are holes filled with mucus, and the skin, too, is covered with a thick coat of slime. The eyes of the ruffe are adapted to dim light, and thus the species is most active in the dark. Ruffe feed on a variety of benthic animals, fish eggs included.
Principal Modes of Transport & Introduction: It is believed that most infestations are the result of people dumping bait into the lakes. It is also believed that they are introduced into new locations in the ballast water of ships.
Annual Cycle: The spawning period of ruffe starts soon after ice meltdown and may last until July. The ruffe has the capacity to reproduce at an extremely high rate. A Ruffe usually matures in two to three years, but a ruffe that lives warmer waters has the ability to reproduce in the first year of life. A single female has the potential to lay from 130,000 to 200,000 eggs annually. Ruffe will leave the deep dark water where they prefer and journey to warmer shallow water for spawning. The primary spawning season for the ruffe occurs from the middle of April through approximately June.
Life, for the Eurasian ruffe, starts as an egg. Egg sizes typically range from 0.34 to 1.3 mm in diameter, depending on the size of the female. If the same female has a second batch in the same season, the eggs will be smaller than the first batch. The size of the second batch of eggs is about 0.36 to 0.47 mm, while the first batch of eggs goes from 0.90 to 1.21 mm in size. If the female lays twice in one season, there is usually one in late winter/early spring and one in late summer. Hatching occurs in 5–12 days in temperatures ranging from 10 to 15 degrees Celsius. The next
11 | P a g e stage in life is the embryonic/juvenile stage. Embryos that are freshly hatched are between 3.5 to 4.4 mm in size. These embryos are sedentary for 3–7 days, and in that time grow to about 4.5 to 5 mm in length. One week after the hatching, the young ruffe start to swim and feed actively, but they do not form schools at this age.
From here, the ruffe gradually mature until they are 2–3 years old, when they reach full maturity. At full length, the adult ruffe is usually around 20 cm, but at a maximum of 29 cm. Growth is usually occurs more when the ruffe is in clear, brackish waters. Generally, female and male ruffe do not live longer than 7 to 11 years.
Look Alike: It resembles the zander (pikeperch) and the perch, but differs from them in its body colour and joined dorsal fins.
Distribution:
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Labidesthes sicculus Brook Silverside
Habitat: Brook Silverside is most common in large rivers, streams, and impoundments near the surface of open waters or quiet areas around piers and boat launches.
Description: The brook silverside is a small, slender species with an elongate caudal peduncle. The top of the head the anterior part of the back are somewhat flattened. A silver stripe extends from the front of the gill cover to the caudal fin and expands at the caudal fin case into a small silver spot. The jaws are long and adapted for feeding at the surface. They are greenish yellow, and the outer edge of the sickle-shaped dorsal and anal fins is light lemon yellow. Scales are small, with 74 to 87 scales in the lateral series.
Principal Modes of Transport & Introduction: It is believed that most infestations are the result of people dumping bait into the lakes.
Annual Cycle: Brook silverside are an annual species. They spawn at age 1 and then die. Reproduction occurs from mid-spring to summer, and spawning takes place in the open water of shallow areas. Males establish loosely defined territories. Adhesive eggs are fertilized in open water and become attached to plants, sticks, or the substrate.
Look Alike: The Book silverside very closely resembles the Inland silverside.
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Distribution:
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Morone Americana White Perch
Habitat: Occurs in fresh, brackish and coastal waters. Primarily found in brackish water but common in pools and other quiet water areas of medium to large rivers, usually over mud.
Description: Morone americana is a semi-anadromous fish that in its native range migrates from the saltier areas of bays and coastland into tidal-fresh portions of streams and rivers to spawn in spring. M. americana usually reach a length of 127-178mm and can weight from 250g on average to a record of 650g. The colouring of this species is variable from dark grayish-green, dark silvery green, or dark brown to almost black on back; pale olive or silvery green on sides; silvery white on belly. Other identifying characteristics include: The body is deepest just ahead of, or at the beginning of, the dorsal fin; There are no lines or stripes on the back or sides; When the spiny dorsal fin is pulled erect, the soft dorsal fin also becomes erect; The second and third bony anal spines are almost exactly the same length; and The anal fin usually has 8 or 9 soft rays behind the 3 bony spines.
Principal Modes of Transport & Introduction: Unauthorized stocking has been a source of spread to inland waters. They may also be spread by anglers using them as bait.
Annual Cycle: White perch are a prolific species. The female can deposit over 140,000 eggs in a spawning session, lasting just over a week. Several males will often attend a spawning female, and each may fertilize a portion of her eggs. The young hatch within one to six days of fertilization. White perch eggs take 2 to 5 days to hatch. When they first hatch, the tiny young are called prolarvae.
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They are only 2 or 3 mm long, and do not have fins yet. They have no mouths yet, so they use stored food energy from their yolk sac. They also cannot see yet. After about 13 days, the prolarvae have grown to about 4 mm long. Their mouths develop, and their eyes begin to work. They are now called postlarvae. When the postlarvae are 7 to 9 mm long, their fins develop and they are called juveniles. The juveniles stay in creeks and rivers where the water is murky and there are many plants. White perch become adults when they are 2 to 4 years old, and males are 72 to 80 mm long and females are 90 to 98 mm long. When there are many fish in an area, they may not grow as large.
Look Alike: The White perch is most often confused with White Bass (Morone chrysops).
Distribution:
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Neogobius melanostomus Round Goby
Habitat: The Round goby is a bottom dweller found in rivers and near the shore of lakes, preferring rocky habitats with many places to hide.
Description: The round goby is a bottom dwelling fish and is slightly flattened on the bottom of its body. Young round gobies are solid slate gray. Older fish are blotched with black and brown and have a greenish dorsal fin with a black spot. The raised eyes on these fish are also very distinctive. It is most readily distinguished from all other freshwater fish in North America by the presence of a fused pelvic fin that forms a suction disk on the ventral surface. Gobies also have a well developed sensory system that enhances their ability to detect water movement. This allows them to feed in complete darkness, giving them an advantage over other fish in the same habitat
Principal Modes of Transport & Introduction: Round Goby is probably transported by freighters in the ballast water during exchange.
Annual Cycle: Round gobies exhibit male parental care. Females can spawn up to six times during the spawning season, which spans April to September. Males will migrate from the deeper water, where overwintering occurs, into shallower breeding grounds during the beginning of the mating season. The males are territoral and will guard nests of eggs and newly hatched young, resulting in successful hatch rates of up to 95%. Its eggs are 4 mm by 2.2 mm in size. Female round gobies reach sexual maturity in 1 to 2 years while males do so in 3 to 4 years. The male releases a steroid sex pheromone that attracts females to their territory. The male may also use visual displays, such as changing color and its posture, along with sounds, during courtship. The females deposit their eggs in male-guarded crevices between rocks. Egg clutches can contain up to 5,000 eggs. Males defend these eggs from predators, and continuously fan them to provide the developing embryos with oxygenated water.
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Look Alikes: Round goby is very similar to the tubenose goby and the native sculpins. They can be distinguished from the sculpins by the fused pelvic fins (sculpins have two separate fins).
Distribution:
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Oncorhynchus mykiss Rainbow Trout
Habitat: Rainbow trout are primarily a freshwater fish, although sea-run populations, often known as steelhead, exist in some areas. It is unclear whether this migration to sea water is genetic or simply opportunistic, but it appears that any population of rainbow trout is capable of migrating to surviving in the sea if the need arises. Well-oxygenated, clean fresh water, with a temperature of around 12°C is preferred, although a range from 10°C to 24°C is tolerated.
Description: Rainbow trout are a deep-bodied, compressed species of fish, with extremely large sea-run individuals growing to 1220mm and 16.3kg. The general body shape is typical for a trout, with a moderately large head and a mouth that extends back behind the eyes. Rainbow trout have highly variable coloration. Rainbow trout that live in lakes have a very silvery appearance, usually with a dark olive-green color on the back. Occasionally the back is a deep steely blue, mostly in Rainbow trout that live well offshore in deep lakes or in small fish that have not yet spawned. Numerous spots are present on the back and extend about two-thirds of the way to the lateral line down the sides. The sides are silvery and largely free of spots, while the belly and ventral surface of the head are whitish. Eyes are an olive to bronze color. Sometimes a soft, metallic-pink color is present along the sides of the body and the head.
Principal Modes of Transport & Introduction: Rainbow trout have been introduced for sport and commercial aquaculture. Rainbow trout is highly valued as a sportfish, with regular stocking.
Annual Cycle: Fertilization is external, with the female trout excavating a hollow in streambed gravel for the eggs to be laid in. Between 700 and 4000 orange-red eggs are laid per spawning event. The male then fertilizes the eggs and they are covered with a layer of gravel. This 'nest' is known as a redd. Lake fish usually spawn in lake tributaries, where the young trout feed and grow before
19 | P a g e migrating downstream after about a year. Growing to maturity in the lake takes around 2 to 4 years, at which time they migrate back to the tributaries to spawn. Most fish will return to the tributary in which they hatched.
Look Alike: Rainbow trout may be mistaken for brown trout and landlocked salmon.
Distribution:
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Petromyzon marinus Sea Lamprey
Habitat: The sea lamprey lives in the open lake, migrating into streams to spawn. The larvae live in soft stream sediments.
Description: Lamprey are eel-shaped fish with a skeleton made of cartilage and they belong to a relic (primitive) group of jawless fishes called Agnathans. The sea lamprey has smooth, scaleless skin and two fins on its back (dorsal fins). The sea lamprey is parasitic; it feeds on other fish, using a suction disk mouth filled with small sharp, rasping teeth and a file-like tongue. These are used by the sea lamprey to attach to a fish, puncture its skin, and drain its body fluids.
Principal Modes of Transport & Introduction: It is believed that most the introduction to new locations is the result of people dumping bait into the lakes and natural migration patterns.
Annual Cycle: Sea lampreys have a complex life cycle. The first four years of their life are spent as ammocoetes ( blind worm-like larval stage) in the soft bottom and banks of waters that flow into lakes. They then transform into the parasitic adult stage and enter the lake to feed on landlocked Atlantic salmon (salmon), lake trout and many other fish species; which they prefer due to their small scales and thin skin. After twelve to twenty months in the lake the adults migrate back into the streams flowing into the lake to spawn, after which the adults die.
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Distribution:
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Pomoxis annularis White Crappie
Habitat: White Crappie lives in Freshwater areas with clear to turbid water and heavy structure. In river areas with slow or no current such as sloughs, backwaters, and oxbows. They Prefer 65-75 degrees F, but very tolerant of extremes. Schools will often seek deep water structure (up to 60 feet) during the day.
Description: The white crappie is a laterally compressed, deep-bodied fish with relatively large dorsal and anal fins. The completely joined dorsal fin contains five to six spines and 14 or 15 rays. The anal fin is slightly larger than the dorsal fin and has five to seven spines and 16 to 18 rays. The back and upper sides are light gray to green, the lower sides are silvery, and the venter is white. The most distinguishing characteristic is the marking patterns or spots on the sides of the fish. A white crappie will have distinct vertical bands of blue/gray spots. Dark margins occur on numerous scales in the nape and breast region, particularly during the spawning season. The dorsal, caudal, and anal fins contain several alternating light and dark bands.
Principal Modes of Transport & Introduction: White Crappie has been introduced for sport and commercial aquaculture. White Crappie is highly valued as a sportfish, with regular stocking.
Annual Cycle: White Crappie are a Spring spawner, beginning when the water hits 62-68 degrees F. Male digs a nest in coarse sand to marble sized gravel in 3-10 feet of water, and then entices females in to mate with him. Females leave only a small quantity of their eggs in each male's nest (spreading their genes as far as possible).
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Look Alike: White Crappie is often confused with its close relative the Black Crappie, with which it can hybridize. They may also be mistaken with Northern Rock Bass and Green Sunfish.
Distribution:
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Proterorhinus marmoratus Tubenose goby
Habitat: The tubenose goby is a bottom-dwelling species that can live in slightly brackish to freshwater. The usual habitat for this species is shallow bays, offshore banks, or flowing water of streams. However, it also can be found in ponds and canals overgrown with vegetation. When current is strong, it hides under boulders. It is often found under stone or among weeds, to which it retreats rapidly if disturbed.
Description: In general, gobies are mottled brown in color and have two dorsal fins, a rounded caudal fin and a blunt head. They have relatively large eyes and scales on their heads. Gobies are characterized by the fusion of their pectoral fins to form a suctorial disc. This unique structure distinguishes the goby from other fishes, including the similar-looking, native sculpin.
Principal Modes of Transport & Introduction: Tubenose goby is spread to new areas by boats ballast water through movement and exchange in many different water bodies. Tubenose gobies lay eggs on vegetation do they can also spread to new areas by being carried on a boat‘s hull, deck, propeller, or trailer that are not properly cleaned.
Annual Cycle: After fertilizing the eggs, the male remains to guard them from predators and keep them free from detritus. The eggs hatch after a few days. The larvae are born transparent, developing their coloration after dispersing to find a suitable habitat. Although the tubenose goby can live up to five years, males die after they spawn.
Look Alike: The tubenose can be distinguished from its round goby cousin because the tubenose has long anterior nostrils. The round goby also has thick lips and protruding eyes, and it can reach 25 cm in length. In contrast, the smaller tubenose goby rarely exceeds 11 cm in length.
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Distribution:
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Salmo trutta Brown Trout
Habitat: Brown trout are primarily a freshwater species, but can spend time in the sea, they hide in shallow water weed beds and rocky, boulder-strewn areas, and prefer a water temperature of 18- 23 degrees C (65-75 degrees F). Brown trout prefer cold, well-oxygenated upland waters.
Description: Brown trout get their name from the brown or golden brown hue on their bodies. Some of the other characteristics: their sides are silvery or yellow and bellies are white or yellowish; dark spots, sometimes encircled by a pale halo, are plentiful on the back and sides; spotting also can be found on the head and the fins along the back; rusty-red spots also occur on the sides; the small adipose (or fatty) fin in front of the tail has a reddish hue; sea-run brown trout have a more silvery coloration and the spotting is less visible.
Principal Modes of Transport & Introduction: Brown trout have been introduced for sport and commercial aquaculture. Brown trout is highly valued as a sportfish, with regular stocking.
Annual Cycle: Spawning takes place in shallow freshwater. Female covers the eggs by restirring the sand and fine gravel. After hatching at 12mm, larval brown trout remain in the gravel for 2-3 weeks until they are about 25mm long, when they emerge to begin feeding in the water column. Brown trout are territorial and begin establishing territories as juveniles. Juvenile trout from lake populations move from their natal inlets to lakes during the first 2 years of life. Juvenile brown trout either migrate to the ocean or stay in freshwater.
Look Alike: Brown trout closely resemble Atlantic salmon and rainbow trout, but salmon have no red coloration on the adipose fin and rainbow trout have lines of black spots on the tail. Young brown trout have 9-14 dark narrow marks along the sides and some red spotting along the lateral line.
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Distribution:
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Scardinius erythrophthalmus European Rudd
Habitat: Found in lakes, rivers, marshes, canals and ponds. They Prefer waters that contain large weed beds. The European Rudd can tolerate a pH range of 7.0 - 7.5 and temperature range of 10 - 22°C. They may also live in brackish waters.
Description: The European rudd is a somewhat stocky, deep-bodied fish with a forked tail, and the mouth is distinct with a steeply angled protruding lower lip. The scales are robustly marked, the back is dark greenish-brown, and the sides are brassy yellow tapering to a whitish belly. The pectoral, pelvic, and anal fins are bright reddish-orange, and the dorsal and tail fins are reddish-brown. Rudd is benthic cyprinid fish with omnivorous feeding habits and a lifespan of up to 15 years. The rudd diets primarily contain various macrophytes, bryophytes, and filamentous algae along with some animal material and detritus. Rudd were more zooplanktivorous in spring and autumn and less in summer and show a size-dependent diet shift from microcrustaceans while small, to macroinvertebrates at larger sizes.
Principal Modes of Transport & Introduction: Bait bucket release seems to be the primary mechanism by which rudd has gained access into open waters.
Annual Cycle: Reproduction occurs from April to August. Adhesive eggs are laid among vegetation. Fecundity ranges from 3500-232000 eggs. Maturation is at 2-3 years, 90-150 mm TL.
Look Alike: The European rudd is easily confused with the native golden shiner (Notemigonus crysoleucas) and sometimes the roach (Rutilus rutilus).
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Tinca tinca Tench
Habitat: The Tench is most often found in still waters with a clay or muddy substrate and abundant vegetation. This species is rare in clear waters across stony ground, and is absent altogether from fast-flowing streams. It tolerates water with a low oxygen concentration, even being found in waters where the carp cannot survive.
Description: Tench have a stocky, carp-like shape, olive-green skin, darker above and almost golden below. The caudal fin is square in shape. The other fins are distinctly rounded in shape. The mouth is rather narrow and provided at each corner with a very small barbel. Maximum size is 70 cm, though most specimens are very much smaller. The eyes are small and red-orange in color. Sexual dimorphism is weak, limited to the adult females having a more convex ventral profile when compared with males. Males may also possess a very thick and flattened outer ray to the ventral fins.The tench has very small scales, which are deeply imbedded in a thick skin, making it as slippery as an eel.
Principal Modes of Transport & Introduction: Tench may be stocked in ponds and lakes for recreational angling.
Annual Cycle: Tench reproduce by external fertilization. They spawn during summer, releasing thousands to millions of tiny eggs (c. 1mm diameter) amongst aquatic weeds. Fry hatch in around a week. Sexual maturity attained at around the age of two. Tench is Long-lived, with individuals surviving to 20 years of age or more.
Look Alike: Tench can be easily mistaken for other cyprinids (Common Carp, Goldfish, and Crucian Carp)
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Plants & Algae
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Alisma gramineum Ribbon-leaved Water-plantain
Habitat: The ribbon-leaved water-plantain grows in mud or submerged in shallow fresh or brackish water in marshy areas. The leaves and tiny purple-tinted white flowers may be submersed or not.
Description: The aquatic ribbon-leaved water plantain resembles its more common relative, common water plantain; however it is generally more diminutive in all dimensions, has aerial leaves that are not heart-shaped at the base and submerged leaves that are long and ribbon-like. The plant may however be identified with certainty by its styles which are strongly curved back. The small, three-petal flowers are white or pale pink with a yellow spot at the centre, are about 5-7 mm across and grow in a many-branched head with an average of about 60 flowers but up to 300. The species is also easily mistaken for another close relative, the narrow-leaved water-plantain, and these two were originally thought to be varieties of the common water-plantain.
Principal Modes of Transport & Introduction: Ribbon-leaf water plantain is spread by waterfowl carrying the seeds and or fragments. It may also be spread to new areas by being carried on a boat‘s hull, deck, ballasts, propeller, or trailers that are not properly cleaned.
Annual Cycle: The species is a short-lived perennial, although it often behaves as an annual. The leaves can develop both below water and above the surface and the flowers appear from June to September. The plant has the ability to self-fertilize and can produce a large quantity of seed. Successful germination may rely on freezing, the disturbance of the mud in which the seed falls or other
34 | P a g e factors; however it has been found that seeds can survive dormant for at least a few years until conditions become suitable for germination. Look Alikes: Ribbon-leaved water-plantain may be confused with various species of duck potato (Sagittaria spp.). The achenes of duck potato are arranged in a ball rather than a ring. Often the leaves of duck potato are arrow-shaped. When growing submersed it is easily confused with tapegrass (Vallisneria americana) or submersed forms of bur-reed (Sparganium spp.).
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Butomus umbellatus Flowering Rush
Habitat: It prefers shallow or slow moving water where it grows as an emergent plant in marshes, backwaters and along shorelines. Plants spread by underground rhizomes, forming dense stands and crowding out native species. Reproduction from seed is uncommon.
Description: The flowering stem, when present, may rise up to 1 meter above the water surface. The leaves are 0.6 to 0.9 meters long, fleshy, triangular in cross-section and twisted at the ends, and can be erect or floating on the surface. The plants flower from summer to fall depending upon conditions, and some populations rarely flower. The small three-petal flowers are white to deep pink to purplish brown in color, and occur on long slender stalks, arranged in an umbel-like spray of up to 30 flowers. The inflorescence is said to resemble an inverted umbrella frame. Flowering Rush can displace native riparian vegetation, decrease biodiversity, alter ecosystem function and change hydrologic regimes.
Principal Modes of Transport & Introduction: Flowering Rush is probably spread by people who plant it in gardens as an ornamental plant. It also spread by rhizomes and root pieces that break off and are carried on a boat‘s hull, deck, propeller, or trailers that are not properly cleaned.
Annual Cycle: Flowering rush is a perennial aquatic herb that emerges each spring from winter-hardy rhizomes.
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Look Alikes: The leaves of flowering rush resemble bur-reed (Sparganium spp.), another shallow-water emergent that is 1 to 4 feet tall. The several species of bur-reed in Wisconsin all have keeled (V- shaped) leaves and female flower parts that resemble small, spiked balls.
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Cabomba caroliniana Fanwort
Habitat: Fanwort prefers lakes and ponds, but can also be found in slow-moving rivers, streams, sloughs and ditches.
Description: Fanwort is a freshwater, submersed, perennial plant with short, fragile rhizomes. It is usually rooted in the substrate, but sometimes found drifting. Its stems are green to reddish brown. It has two types of leaves: submersed and floating. The submersed leaves are arranged in pairs or in whorls along the stem and the floating leaves are diamond shaped and are arranged in an alternating pattern. It has small white, pink or purple flowers that float on the surface and grow from the tips of the stems.
Principal Modes of Transport & Introduction: Fanwort may spread to new areas by stem fragments carried on a boat‘s hull, deck, propeller, or trailers that are not properly cleaned. It is also believed that infestations are the result of people dumping aquariums into the lakes.
Annual Cycle: Fanwort primarily reproduces via regrowth of stem or rhizome fragments, but can reproduce via seed. A small fragment can regenerate a whole plant that in turn, can reproduce clonally and spread rapidly, often replacing native species. It flowers from May to September, yet viable shoots have been observed in January beneath ice. Fanwort can form dense stands that clog drainage systems and interfere with swimming and boating. Plant fragments can be transported in rivers, streams or floodwaters, and by adhering to migrating wildlife and boats.
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Look-alikes Fanwort is often confused with watermilfoils (Myriophyllum), water buttercup (Ranunculus aquatilis) and Beck's watermarigold (Megalodonta beckii). The leaves of watermilfoils are whorled and the plants have small, flowers growing from where its leaves meet the stem. Water buttercup has alternately arranged leaves. Beck‘s watermarigold has yellow, composite flowers and sessile leaves, while Fanwort has white flowers and slender leaves.
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Didymosphenia geminata Rock Snot or Didymo
Habitat: Didymosphenia geminata, commonly referred to as "didymo", is a freshwater microscopic diatom. It is found in streams and rivers in much of North America. Didymo increasingly poses a threat to aquatic ecosystems because it forms extensive mats on stream beds. It occurs particularly in oligotrophic, clear-water montane or northern boreal streams. Didymo thrives in clear, shallow, warm and nutrient-poor water, and is influenced annually by weather and rainfall patterns. An important habitat requirement for D. geminata is high light levels.
Description Didymo is a single-celled, freshwater alga or diatom. While the individual cells are invisible to the naked eye, Didymo can form large colonies or mats that attach via a stalk to rocks and plants smothering the bottoms of streams and rivers with a thick yellow/brown layer of growth. The massive blooms can form distinctive flowing ‗rats tails‘ these stalks have a rough texture similar to wet wool and mimic strands of toilet paper, as opposed to other algal species which feel "slimy".
Principal Modes of Transport & Introduction: Recreational equipment, including boats, kayaks, lifejackets and fishing gear (particularly waders) is the most likely way for didymo to spread.
Annual Cycle: As the diatom cells attach to a rocky (or other) substrate and begin to produce stalks. The growths are visible to the naked eye, and are light tan to brown in color. This stage is common during the late winter or following periods of high flow, but can occur at any time of year, depending on the region. As the colonies grow, they merge together and may cover the substrate completely. Colonies attached to plant stems to form rope-like strands. As several small colonies coalesce and stalk production increases, the
40 | P a g e clumps become thicker. Under periods of low flow or with favorable growth conditions, the colonies have the opportunity to form blooms. The cells produce excessive amounts of stalk many times the length of the microscopic cells. As the stalks lengthen, they form ropy strands and are white in color. Some reports describe the strands as tissue, fiberglass, toilet paper, or sheepskins
Look-alikes: In the field, Didymo can be easily confused with other stalk-forming diatom species. In particular, the visual appearance of Didymo is very similar to its closest relatives, Cymbella mexicana and C. mexicana var. janischii. However, Didymo is distinctive to the touch. When Didymo stalks are pulled apart, there is some resistance and the stalks feel like wet cotton balls. Other diatom species have no such resistance, and they are slimy and slippery when the stalks are pulled apart.
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Egeria densa Brazilian Elodea
Habitat: It grows in still and flowing waters such as lakes, ponds, pools, ditches, quiet streams and seems to grow best in mildly acidic, nutrient-rich lakes. During winter, it survives along the bottom and resumes growing when waters reach 50 degrees Fahrenheit. It forms mats dense enough to restrict water movement, trap sediment and cause fluctuations in water quality.
Description: Brazilian waterweed is a submersed, freshwater, perennial herb, usually rooted in the substrate but in some cases, drifting. Its stems are cylindrical and simple or branched, and typically grow 1-2 feet long, but can grow up to 20 feet long. Leaves grow in whorls of 3 to 8 with short internodes making the plant look very leafy. The leaves have tiny serrations on the margin and smooth midveins. It has small, white and greenish flowers that extend roughly 1 inch above the water.
Principal Modes of Transport & Introduction: It is believed that most infestations are the result of people dumping aquariums into the lakes. It may also spread to new areas by plant fragments being carried on a boat‘s hull, deck, ballasts, propeller, or trailers that are not properly cleaned.
Annual Cycle: Reproducing via fragmentation allows it to spread from a single plant and tends to choke out slower-growing native plants. It can also out compete Eurasian water milfoil.
Look-alikes: Many other plants look similar to Brazilian elodea and those could be essential to an ecosystem. Brazilian waterweed is often confused with hydrilla (Hydrilla verticillata), American waterweed (Elodea canadensis) and common waterweed (Elodea nuttallii).
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Eichhornia crassipes Water Hyacinth
Habitat: Water Hyacinth invades lakes, ponds, rivers, marshes, and other types of wetland habitats.
Description: Free floating aquatic plant ranging from 0.5-1 m in height with distinctive air bladders that keep leaves afloat above the water; forms dense, floating mats. Leaves are thick, waxy, round, broad, 10-20 cm in diameter, cuplike, glossy, green leaves. The Stems are spongy, erect, stems (up to 50 cm long) inflated with air bladders towards the base. They have showy, lavender-blue, 6-petaled flowers; upper petals with a central, yellow, blue bordered blotch; 8-15 flowers occur on a single spike that can be up to 30 cm long. Fruit is a 3-celled capsule with numerous tiny seeds. This plant reproduces by fragmentation of stolons, adventitious root system, and to a lesser extent by seed.
Principal Modes of Transport & Introduction: It is believed people dumping aquariums or ornamental pond plants are often the means of spread. Water Hyacinth can also spread by seeds attached to boats and equipment that are not properly cleaned. The seeds may also be transported by waterfowl.
Annual Cycle: It reproduces chiefly by vegetative means and can quickly form dense floating mats of vegetation (populations can double in size in two weeks).
Look-alikes: Pickerelweed (Pontederia cordata) has purple flower spikes and lacks the conspicuous air bladder; not mat-forming.
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Hydrilla verticillata Hydrilla
Habitat: Hydrilla is found in the submersed plant community. The adaptability of this plant to a wide variety of environmental conditions has earned hydrilla its reputation as the perfect weed. Hydrilla can grow in a variety of substrates, in waters still or flowing, low or high in nutrients. Hydrilla may also threaten estuary systems, tolerating salinities up to 10 parts per thousand. Remarkably adapted to low light conditions, hydrilla can photosynthesize earlier and later in the day than most plants, grows well in turbid water and, when the water is clear, to depths exceeding 10 meters. Hydrilla typically occurs in dense, rooted stands, but live fragments may also be found drifting in large mats.
Principal Modes of Transport & Introduction: Hydrilla may spread to new areas by stem fragments and turions carried on a boat‘s hull, deck, propeller, or trailers that are not properly cleaned. Turions are smaller and are easily carried by water currents or waterfowl, providing a mechanism for long distance transport.
Description: Hydrilla is a perennial submersed aquatic plant with long slender, branching stems emerging from horizontal underground rhizomes and above ground stolons. The leaves are strap like and pointed with claw-like serrations along the outer margins. (The serrations are tiny but generally visible without magnification.) The leaves are typically arranged in whorls of 4 to 8. Small white flowers rise to the surface on slender stalks from the upper leaf axils. Hydrilla produces two types of over-wintering structures. Spiny green turions (5 to 8 mm long) are produced in the leaf axils. Small, somewhat crescent-shaped tubers (5 to 10 mm long), form along the rhizomes and stolons. The tubers have a scaly appearance under magnification and are pale cream to brownish in color.
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Annual Cycle: Hydrilla sprouts from over-wintering rhizomes, tubers and turions in the spring, the leafy stems growing rapidly toward the surface. Flowers, turions and tubers are produced during the growing season. The turions drop to the sediments when the leafy vegetation begins to break up in the fall. The plants die back completely to the sediments by early winter. The rhizomes, tubers and turions over-winter. The turions will sprout the following spring, but the tubers may remain dormant for several years in the sediments. The tubers and turions can withstand ice cover, drying, ingestion by waterfowl, and herbicides. In addition to reproducing vegetatively by way of tubers and turions, hydrilla propagates readily from stem or root fragment. The monoecious form can produce viable seeds. Seed production and viability is thought to be low relative to vegetative reproduction.
Look Alikes: Hydrilla may be confused with Brazilian waterweed, native waterweeds, water starworts and mare‘s tail.
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Hydrocharis morsus-ranae European Frog-Bit
Habitat: European frog-bit prefers quiet waters and can blanket shallow ponds, marshes and the edges of lakes. Like other aquatics, it can spread to new locations from plant fragments attached to boats and trailers. Thick mats of frog-bit inhibit light penetration and can hinder the movement of fish, waterfowl and boats.
Description: European frog-bit is a free-floating aquatic plant that resembles a miniature water lily. Leaves are thick, heart-shaped, 1 to 2 inches wide and smooth-edged with spongy, purplish-red undersides. Small, showy flowers are ½ inch across, appear singly and have three white petals and yellow centers. Roots are 3 to 8 inches long and unbranched, dangling from the underside of each rosette of leaves. Plants form a thick mat with tangled roots and runners.
Principal Modes of Transport & Introduction: Frogbit may spread to new areas by both turions and plantlets carried on a boat‘s hull, deck, propeller, or trailer that are not properly cleaned.
Annual Cycle: There are two primary methods of reproduction. Plants send out horizontal stems (stolons) which produce daughter plants that can break free and float to new locations. It also produces turions - compact winter buds that sink to the bottom in fall and float back up in spring to grow into new plants.
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Look-alikes: European frog-bit can be mistaken for water lily but its leaves are distinctly heart-shaped, leathery and much smaller than any of water lilies. Water lily flowers are much larger, with more than 3 petals.
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Iris pseudacorus Yellow Flag Iris
Habitat: Common in wet habitats including wet meadows, wet woods, fens, wet dune-slacks, and the edges of watercourses, lakes and ponds. It can also be found alongside coastal streams, on raised beaches, salt marsh and shingle.
Description: The yellow flag iris is a robust plant with beautiful bright yellow flowers. The roots and bulbs are thick and fleshy, and the narrow sword-shaped leaves are bluish-green with a prominent mid- rib. As in all irises, the flowers of yellow flag are composed of six perianth segments: three outer ones called "falls" which droop outward and down, and, alternating with the falls, three inner segments called "standards." The falls and standards of yellow flag are bright yellow with violet or brownish veins. In addition, each fall has a darker yellow-brown blotch near its base. There are usually 4-12 flowers on each branched flower stalk, and they appear in early spring.
Principal Modes of Transport & Introduction: The yellow flag iris is commonly used as an ornamental plant for landscapingand water gardens. Vegetative spread through local perturbation is also a way to spread yellow flag iris; clipped, trampled, or buried stems of established plants may produce shoots and roots. It also spreads downstream by broken rhizomes and possibly by seed.
Annual cycle: Yellow flag iris reproduces by seeds as well as by vegetative reproduction.
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Look Alikes: Iris pseudacorus especially when not in bloom, might be confused with other native irises, which have more-or-less identical leaf structure and size. They may also be confused with larger Typha (cat-tail) species, which look similar in structure and height.
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Lythrum salicaria Purple Loosestrife
Habitat: This plant's optimal habitat includes marshes, stream margins, alluvial flood plains, sedge meadows, and wet prairies. It is tolerant of moist soil and shallow water sites such as pastures and meadows, although established plants can tolerate drier conditions. Purple loosestrife has also been planted in lawns and gardens, which is often how it has been introduced to many of our wetlands, lakes, and rivers. The plant's reproductive success across North America can be attributed to its wide tolerance of physical and chemical conditions characteristic of disturbed habitats, and its ability to reproduce prolifically by both seed dispersal and vegetative propagation.
Description: Purple loosestrife is a perennial herb 3-7 feet tall with a dense bushy growth of 1-50 stems. The stems, which range from green to purple, die back each year. Showy flowers vary from purple to magenta, possess 5-6 petals aggregated into numerous long spikes, and bloom from July to September. Leaves are opposite, nearly linear, and attached to four-sided stems without stalks. It has a large, woody taproot with fibrous rhizomes that form a dense mat.
Principal Modes of Transport & Introduction: Purple Loosestrife is commonly used as an ornamental plant for landscaping. Most of the seeds fall near the parent plant, but water, animals, boats, and humans can transport the seeds long distances. Vegetative spread through local perturbation is also characteristic of loosestrife; clipped, trampled, or buried stems of established plants may produce shoots and roots.
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Annual Cycle: Optimum substrates for growth are moist soils of neutral to slightly acidic pH, but it can exist in a wide range of soil types. Most seedling establishment occurs in late spring and early summer when temperatures are high. Purple loosestrife spreads mainly by seed, but it can also spread vegetatively from root or stem segments. A single stalk can produce from 100,000 to 300,000 seeds per year. Seed survival is up to 60-70%, resulting in an extensive seed bank. Mature plants with up to 50 shoots grow over 2 meters high and produce more than two million seeds a year. Germination is restricted to open, wet soils and requires high temperatures, but seeds remain viable in the soil for many years. Even seeds submerged in water can live for approximately 20 months. Plants may be quite large and several years old before they begin flowering.
Look Alikes: This species may be confused with the native wing-angled loosestrife (Lythrum alatum) found in moist prairies or wet meadows. Wing-angled loosestrife has a winged, square stem and solitary paired flowers in the leaf axils. It is generally a smaller plant than the Purple loosestrife.
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Marsilea quadrifolia WATER CLOVER
Habitat: Found in wet conditions of slow-flowing rivers and streams, muddy shorelines to roadside ditches.
Description: Water Clover is a aquatic to amphibious fern. Four-leaf clover-like leaves monochromatic green, downy on first appearance (as fiddleheads) becoming glabrous when mature. Land leaves 1.5 - 4 cm broad. Sporocarps bear a single posterior tooth, are covered in hair that later sheds, and borne on short stalks that arise 1 – 12 mm above the junction of the petiole and rhizome. In wet conditions, male and female spores germinate and cross-fertilize to produce new plants.
Principal Modes of Transport & Introduction: Water Clover may spread to new areas by fragments carried on a boat‘s hull, deck, propeller, or trailers that are not properly cleaned. It is also believed that infestations are the result of people dumping aquariums into the lakes or ornamental ponds.
Annual Cycle: The plant produces sporocarps, these needs to be lightly abraded and then immersed in water. The sporocarps will then swell and burst to release the spores. The spores germinate immediately, the highly developed prothallus remains inside the large seed-like spores. The first roots and shoots appear in 2 - 3 days. Mature plants bearing sporocarps can develop in as little as 3 months. Spore germination in the family occurs after rupture of the sporocarp wall allows the sporocarp contents to be hydrated. A gelatinous structure emerges from the sporocarp, breaking it into valves and carrying the sori into the water. Spore germination (gametophyte growth) and fertilization occur immediately.
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Look Alikes: M. quadrifolia is sometimes confused with M. mutica. M. quadrifolia having a solid green leaf color, peduncles that attach higher up on the petiole and sporocarps bearing a tooth.
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Myriophyllum aquaticum PARROT FEATHER
Habitat: Parrot feather is found in both the emergent and the submersed plant communities of freshwater lakes, ponds, and slow moving streams. It is also adapted to waters with some salt intrusion. While it grows best when rooted in shallow water, it has been known to occur as a floating plant in the deep water of nutrient-enriched lakes. It is well adapted to life at the water‘s edge and can survive when stranded on dewatered river banks and lake shores.
Description: Long unbranched stems arise from roots and rhizomes. Unburied rhizomes function as a support structure for adventitious roots, and provide buoyancy for emergent growth. Emergent stems may grow to a height of 30 cm above the water surface. Slender, feather-divided leaves occur along the trailing stems in whorls of 4 to 6 leaves. Whorls are openly spaced toward the base, and more closely arranged toward the growing tip. Leaves are 2.5 to 5 cm long, with 10 to 18 leaflet pairs, flattened midribs and a short petiole. The emergent leaves are robust, vibrant green, and covered with a waxy coating. Submersed leaves, in contrast, are limp and brownish, and often in a state of deterioration. Small white flowers (female only) are inconspicuous, and borne in the axils of the emergent leaves.
Principal Modes of Transport & Introduction: Parrot feather may spread to new areas by fragments carried on a boat‘s hull, deck, propeller, or trailer that are not properly cleaned. It is also believed that people dumping aquariums or ornamental pond plants are a means of spread.
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Annual Cycle: Parrot feather is an aquatic perennial that propagates through root division and plant fragments. Plants usually flower in the spring but fall flowering also occurs. Male and female flower parts occur on separate plants, and male plants are only known to occur in the plant‘s native range. As a result, parrot feather populations in the United States do not produce seeds. Plants die back to their rhizomes toward the end of the growing season. New shoots begin to grow rapidly from overwintering rhizomes as water temperatures rise in the spring.
Look Alikes: When emergent stems and leaves are not present, parrot feather may be confused with bladderworts, hornworts, mermaid weeds, water crowfoots, and other leafy milfoils.
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Myriophyllum heterophyllum VARIABLE WATER-MILFOIL
Habitat: Variable water-milfoil is an extremely well adapted plant, able to thrive in a wide variety of environmental conditions. It grows well in still and flowing waters, and can survive under ice. Variable water-milfoil grows rooted in water depths from 1 to 5 meters on various substrates including organic muck, silt, sand and gravel. Plants stranded on dewatered shorelines form erect spikes known as ―terrestrial morphs.‖ The morphs, resembling miniature pine trees, will remain in this land-adapted form until the waters return, at which time they will ―morph‖ back into submersed aquatic plants.
Description: Variable water-milfoil is a submersed, aquatic plant with branching stems emerging from dense, spreading roots. Featherdivided leaves are arranged in densely packed whorls. (Leaves along lower portions of the stem may not be in perfect whorls, i.e., some leaves may be slightly offset.) There are generally 4 to 6 leaves per whorl and 5 to 14 pairs of thread-like leaflets on each leaf. The dense leaf arrangement gives this plant a bottle brush appearance. Stems may be green and slight, but most often they are thick, robust and reddish in color (even bright red). Flowers and bracts are arranged in whorls on an emergent flower spike. The tiny white flowers occur in the axils of the bracts. The bracts are bladeshaped, serrated, and more than twice the length of the flower. Winter buds (or turions) are formed in the fall at the base of the stems or on the rhizomes.
Principal Modes of Transport & Introduction: Fanwort may spread to new areas by stem fragments carried on a boat‘s hull, deck, propeller, or trailers that are not properly cleaned.
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Annual Cycle: Variable water-milfoil is an extremely hardy aquatic perennial that propagates through root division, fragmentation, turions and seeds. Flowering spikes typically emerge from the water in mid to late summer, but not all colonies produce flowers. Auto-fragmentation may occur during the growing season with stem sections developing roots even before they separate from the parent plant. Toward the end of the growing season some plants break apart and die back to their rootstalks; others overwinter intact. New growth sprouts from turions, roots, overwintering plants and plant fragments as the water begins to warm in the spring, growing rapidly toward the surface. Certain milfoils are able to hybridize with other, closely related, milfoil species.
Look Alikes: May be confused with bladderworts, hornworts, mermaid weeds, water crowfoots, and other leafy water-milfoils.
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Myriophyllum spicatum EURASIAN WATER-MILFOIL
Habitat: Eurasian water-milfoil is an extremely well adapted plant, able to thrive in a wide variety of environmental conditions. It grows well in still and flowing waters, tolerates mild salinities and can survive under ice. Eurasian water-milfoil grows rooted in water depths from 1 to 10 meters, generally reaching the surface in depths of 3 to 5 meters. Though adapted to a wide variety of substrate types, this species seems to favor fine-textured, inorganic sediments.
Description: Branching stems of Eurasian water-milfoil emerge from dense, spreading roots. The leaves are arranged in whorls of 3 to 6 leaves (4 leaves per whorl is common). The whorls are openly spaced along the stem, with 1 to 3 cm between nodes. The leaves are finely feather-divided, typically with 12 to 24 pairs of thread-like leaflets on each leaf. Since the leaves of other milfoil species generally have fewer than 14 leaflet pairs, counting leaflets can provide helpful clues to identifying Eurasian water-milfoil. (Note that the occasional Eurasian milfoil leaf may have as few as 5 leaflet pairs. For this reason it is always advised to count leaflet pairs on several leaves, taken from various points along the stem.) The tips of the leaves often have a blunt, snipped-off appearance. Flowers and bracts occur in whorls on slender flower spikes that rise above the water surface. The bracts have smooth margins and the flowers are generally larger than the bracts. Eurasian water-milfoil does not form winter buds.
Principal Modes of Transport & Introduction: Eurasian water-milfoil may spread to new areas by stem fragments carried on a boat‘s hull, deck, propeller, or trailer. Wave action or a duck paddling through a milfoil bed can also cause stems to break.
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Annual Cycle: Eurasian water-milfoil is an extremely hardy aquatic perennial that propagates through root division, fragmentation, and seeds. Flowering spikes typically emerge from the water in mid to late summer, but not all colonies produce flowers. Auto-fragmentation may occur during the growing season with stem sections developing roots even before they separate from the parent plant. Toward the end of the growing season some plants break apart and die back to their rootstalks; others overwinter intact. New growth sprouts from roots and overwintering plants and plant fragments as the water begins to warm in the spring, growing rapidly toward the surface. Certain milfoils are able to hybridize with other, closely related, milfoil species.
Look Alikes: May be confused with bladderworts, hornworts, mermaid weeds, water crowfoots, and other leafy water-milfoils.
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Najas guadalupensis SOUTHERN NAIAD
Habitat: Southern naiad is found in the submersed plant community, inhabiting ponds and steams and occasionally brackish waters. This species seems to be more tolerant of warm water temperatures, turbidity and eutrophication than other Najas species.
Description: The stems of naiad species are very long and have many branches. All naiads have very narrow, inch-long leaves that have definite teeth on their margins. Southern naiad leaves are less than 1/16 inch wide. With a hand lens, very tiny teeth can be seen along the leaf margins. Naiad leaves are arranged oppositely on the stem, or sometimes in whorls of three. The leaves are deep green to purplish-green. The flowers are very small and inconspicuous.
Principal Modes of Transport & Introduction: Southern naiad may spread to new areas by stem fragments carried on a boat‘s hull, deck, propeller, or trailers that are not properly cleaned.
Annual Cycle: Unlike most aquatic plants, southern naiad is a true annual, dying back completely in the fall and relying upon seeds to return in the spring. Vegetative reproduction may occur during the growing season. Tiny flowers occur in the leaf axils through midsummer and seeds occur by mid to late summer.
Look Alikes: European naiad, thread-like naiad, and slender naiad. Southern naiad may be confused with some of the small form, fine-leaved pondweeds.
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Najas minor BRITTLE NAIAD
Habitat: Brittle naiad is found in the submersed plant community, growing in ponds, lakes, and slow moving streams in depths up to 5 meters. Preferring sand and gravel, the plants thrive in a wide range of substrates. Brittle naiad is tolerant of turbidity and eutrophic (nutrient rich, productive) conditions.
Description: Unlike most aquatic plants, Brittle naiad is a true annual. Seedlings grow from slender roots, developing stems up to 2.5 meters long that often branch profusely near the top. The leaf arrangement is not strict, and leaves may appear to be opposite, sub-opposite, in whorls or clumps. The leaves are small (rarely more than 3.5 cm long) and very slender (0.3 – 0.5mm wide), strapshaped, pointed and serrated. Unlike all native naiads whose leaf serrations or spines are virtually invisible to the unaided eye, the leaf serrations of Brittle naiad, though tiny, can usually be observed without magnification. Visible serrations, therefore, provide a key characteristic for identifying this invader. A second characteristic that distinguishes Brittle naiad from native naiad species—including the most common by far, Najas flexilis—is the abruptly protruding (as opposed to gently flaring) blocky or fanshaped leaf base. The upper margin of the leaf base is finely toothed or fringed in appearance. You may need to carefully pull the leaf away from the stem and use a hand lens to see the base clearly. (Note: The leaf base of Najas gracillima, is also blocky and toothed) Like all naiads, the flowers are small, inconspicuous, and borne in the leaf axils. The seeds are purplish, 1.5 to 3.0 mm long, spindle shaped and slightly curved, with rectangular indentations arranged in distinct longitudinal rows.
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Principal Modes of Transport & Introduction: Brittle Naiad may spread to new areas by stem fragments carried on a boat‘s hull, deck, propeller, or trailer.
Annual Cycle: A true annual, Brittle naiad grows anew from seeds each spring. Seeds form in the leaf axils from July through September. Although Brittle naiad can reproduce by fragmentation during the growing season, the primary means of reproduction appears to be by seed. It is estimated that a productive, one-acre infestation will produce tens of millions of seeds per season. During the late summer or early fall, the stems of Brittle naiad become brittle, and break up. Seeds remain attached in the leaf axils, and wind and water currents disperse the fragments.
Look Alikes: May be confused with native naiads, some fine-leaved pondweeds, and some stoneworts.
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Nitellopsis obtusa Starry Stonewort
Habitat: Starry Stonewort is sometimes found in deep, slow moving water where other plants are scarce. Starry stonewort tends to occur at depths of 1-6 m. Starry Stonewort is known to maintain permanent populations in freshwater or brackish water with salinity up to 5%. It experiences suppressed growth at water temperatures of 30°C. It can withstand low light conditions.
Description: Starry Stonewort forms dense colonies of upright, plant-like stems sprouting whorls of slender, tentacle-like branches. The tiny, cream-colored, star-shaped reproductive structures called "bulbils" that occur at the base of branch clusters are distinctive. Even before they are evident to the naked eye the bulbils can be detected by feel, by gently squeezing the stems at the whorls. The tiny bulbils are distinctly "firm" relative to the soft gelatinous feel of the rest of the algae.
Principal Modes of Transport & Introduction: Starry stonewort is spread to new areas by being carried on a boat‘s hull, deck, ballasts, propeller, or trailers that are not properly cleaned.
Annual Cycle: This stonewort is usually a summer annual, but in some years, if the winter is mild, it may not fully die back. This species very rarely produces spores. It is thought that spore production is controlled by light levels. This species spreads mainly by means of the star-shaped bulbils that occur on the lower stem nodes. These bulbils stay viable for several years.
Look Alikes: Starry Stonewort may be mistaken for Nitella (nitells, spp.) and Muskgrass (chara, spp.).
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Nymphoides peltata YELLOW FLOATING HEART
Habitat: Yellow floating heart is found within the floating-leaved plant community. It can grow in various substrates (sand, mud, gravel, etc.), in littoral areas ranging from the damp mud along the water‘s edge to water depths of 4 meters.
Description: Rounded to heart-shaped floating leaves emerge on long stalks from rooted stems. Each rooted stem supports a loosely branched group of several leaves. Note that all heart-shaped floating leaved plants that are native to Maine produce only one leaf per rooted stem. The leaves are typically wavy (shallowly scalloped) along the outer edges and have purplish undersides. Leaves average 3 to 10 cm in diameter. The flowers are showy (3 to 4 cm in diameter), bright yellow with five distinctly fringed petals. They are held above the water surface on slender stalks with 1 to 5 flowers per stalk. The fruit capsule is 2.5 cm long and contains numerous seeds. The seeds are oval and flat (about 3.5 mm long) and hairy along their outer edges.
Principal Modes of Transport & Introduction: Yellow floating heart is a popular aquatic garden ornamental for outdoor water gardens. This would allow it to be spread to new areas by water (during rain events) and/or by waterfowl. Is may also spread to new areas by being carried on a boat‘s hull, deck, ballasts, propeller, or trailers that are not properly cleaned.
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Annual Cycle: Yellow floating heart is an aquatic perennial that propagates by seeds, fragmentation, and spreading rhizomes. Most floating leaved plants lack the ability to propagate by fragmentation, but in the case of yellow floating heart broken leaves with attached stem parts will form new plants. Viable seeds are produced abundantly and germinate readily. Seed hairs help the seeds float and aid their attachment to waterfowl, increasing possibility of spread to new areas.
Look Alikes: May be confused with European frogbit, fragrant water lily, little floating heart, spatterdock, and watershield.
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Phragmites australis Common Reed
Habitat: Common reed thrives in sunny wetland habitats. It grows along drier borders and elevated areas of brackish and freshwater marshes and along riverbanks and lakeshores. The species is particularly prevalent in disturbed or polluted soils with alkaline and brackish waters, but will tolerate highly acidic conditions. It can grow in water up to 6 feet deep and also in somewhat dry sites. It can be found along roadsides, ditches, open wetlands, riverbanks, lake shores, dredged area, and disturbed or undisturbed plant communities.
Description: Common Reed is a tall perennial wetland grass ranging in height from 3 to 20 feet. Strong leathery horizontal shoots, called rhizomes, growing on or beneath the ground surface give rise to roots and tough vertical stalks. Cane-like stems, 1 inch in diameter, support broad sheath-type leaves that are .5 to 2 inches wide near the base, tapering to a point at the ends. Large dense, featherlike, grayish purple plumes, 5 to 16 inches long, are produced in late June to September. The plant turns tan in the fall and most leaves drop off, leaving only the plume-topped shoot. The root system is comprised of rhizomes that can reach to 6 feet deep with roots emerging at the nodes. Common reed reproduces by spreading rhizomes that form large colonies.
Principal Modes of Transport & Introduction: Common Reed has been used in many wetland rehabilitation and stabilization projects. It is used to revegetate disturbed riparian areas, control shore erosion, stabilize river and canal banks, and reduce wave action on watershed structures. It also may spread to a new area by sprouting from a rhizome fragment or from seed carried on a boat‘s hull, deck, propeller, or trailer.
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Annual Cycle: Common Reed spreads easily and extensively by seed; also by an extensive, aggressive system of horizontal and vertical rhizomes that can live for 3-6 years.
Look Alikes: Common Reed is distinctive and much taller than most other grasses, particularly the non-native form. Wild rice (Zizania aquatica), though quite tall, lacks the feathery appearance; large non- flowering plants of reed canarygrass (Phalaris arundinacea) appear similar but lack hairy ligules.
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Pistia stratiotes Water Lettuce
Habitat: The plant prefers stationary or slow moving streams and could become established in most areas. Like other floating plants, water lettuce can survive for long periods when stranded on mud banks or in other damp situations such as a roadside culvert where it may even take root.
Description: As its name implies, water lettuce resembles a floating open head of lettuce. Water lettuce has very thick leaves. The leaves are light dull green, are hairy, and are ridged. There are no leaf stalks. Water lettuce roots are light-colored and feathery. Its flowers are inconspicuous.
Principal Modes of Transport & Introduction: It is believed people dumping aquariums or ornamental pond plants are often the means of spread. Water Lettuce can also spread by plant fragments attached to boats and equipment that are not properly cleaned.
Annual Cycle: Seeds from the muddy bottom germinate in late November-early December and float to the surface as seedlings. Flowering and reproduction commences early in the plant's life − about the 4th or 5th leaf stage, when plant densities are high. Propagation is through flower pollination or by stolons (20 cm long), which produce daughter plants. Water lettuce is sensitive to frost and can grow in polluted water.
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Look Alikes: Water Lettuce is not likely to be confused with any other floating plants.
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Potamogeton crispus Curly-Leaf Pondweed
Habitat: Curly-leaf pondweed is found in the submersed plant community. Generally preferring soft sediments, it grows in waters that are shallow or deep, still or flowing. Curly-leaf thrives where many other aquatic plants do not, for example in waters that are shaded, disturbed, polluted or turbid.
Description: Curly-leaf pondweed is an invasive aquatic perennial that is native to Eurasia, Africa, and Australia. It was accidentally introduced to United States waters in the mid-1880s by hobbyists who used it as an aquarium plant. The leaves are reddish-green, oblong, and about 3 inches long, with distinct wavy edges that are finely toothed. The stem of the plant is flat, reddish-brown and grows from 1 to 3 feet long. The plant usually drops to the lake bottom by early July.
Principal Modes of Transport & Introduction: Curly-leaf pondweed can spread by plant fragments attached to boats and equipment that are not properly cleaned.
Annual Cycle: Curly-leaf pondweed, an aquatic perennial, is adapted to growing in cool Plants sprout from rhizomes and turions in the late fall and grow through the winter, reaching maturity relatively early in the season (late spring through early summer). Flowers and turions are produced during the growing season and the plants generally begin breaking up by mid-July. The turions scatter with the plant fragments and drop to the sediments, where they lie dormant until the water begins to cool again in the fall. In addition to propagation by turion and creeping rhizomes, curly-leaf pondweed produces seeds. Little is known, however, regarding the importance of seeds in the spread and propagation of this plant.
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Look Alikes: May be confused with various types of pondweeds.
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Trapa natans WATER CHESTNUT
Habitat: Water chestnut grows in the floating-leaf and submersed plant community. It thrives in the soft sediments of quiet, nutrient rich waters in lakes, ponds and streams. The plant is well adapted to life at the water‘s edge, and prospers even when stranded along muddy shores.
Description: Water chestnut has two distinct leaf types. The floating leaves are somewhat triangular (or fan shaped) in form, with conspicuously toothed margins along the outside edges. The upper surface of the leaf is glossy, the undersides covered with soft hairs. The leaves are arranged in a loose, radiating pattern or rosette and joined to the submersed stem by long leaf stems, or petioles (up to 5 cm long). Spongy inflated bladders in the petioles provide buoyancy for the rosette. The rosettes are anchored to the sediments on stems reaching lengths of up to 5 meters. The first submersed leaves to emerge are alternate, linear and entire, but these give way as the plant develops to feather-like finely divided, leaf-like roots (or root-like leaves—there is ongoing debate as to which is correct). The upper leaf-roots contain chlorophyll, causing them to be greener. When water levels drop, those lower down anchor the plant to sediments. Small white flowers appear above the rosettes in mid to late July, each emerging from its own stalk from the axils of the floating leaves. When the fruits form they submerse and dangle beneath the rosette. The fruits are woody and nut-like, typically with four sharp barbs.
Principal Modes of Transport & Introduction: Water Chestnut is used as an aquatic garden ornamental for outdoor water gardens. This would allow it to be spread to new areas by water (during rain events) and/or by waterfowl. It may also be spread to new areas on a boat‘s hull, deck, propeller, or trailer that are not properly cleaned.
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Annual Cycle: Unlike most aquatic plants, water chestnut is a true annual. Plants sprout anew each year from seeds overwintering in the sediments. Submersed stems grow rapidly to the surface, where the floating rosettes form and the flowers and fruits develop. During the growing season rosettes may become detached and float to new areas. Water chestnut flowers from July to September. The fruit, or nuts, begin to appear by late summer. Each water chestnut seed can produce 15 to 20 new rosettes and each rosette can generate up to 20 seeds. At the end of the growing season, frost kills the plants and decomposition is rapid. The nuts fall and sink into the sediment where they over-winter and sprout in the spring. The nuts may remain viable for up to 12 years but most germinate within 2 years. The nuts have sharp barbs that readily attach to boating gear and wildlife and are easily dispersed by natural and human processes.
Look Alikes: Water chestnut is not easily confused with other aquatic plants.
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Utricularia inflata Swollen Bladderwort
Habitat: Floating freely in shallow water, or loosely attached to the sediment.
Description: Swollen bladderwort is a member of a group of freely floating, rootless, carnivorous aquatic plants. It obtains its nutrients from the water and from tiny creatures that it captures in its seed- like bladders. These bladders are actually traps that use a vacuum to capture small invertebrates that trigger a trap door. Once inside the bladder, the plant secretes enzymes to digest the prey, providing the plant with nutrients. When in flower, the plant forms a very distinctive wheel-like floating platform that supports a yellow snapdragon-like flower. These flowers extend about six inches above the water surface.
Principal Modes of Transport & Introduction: Swollen Bladderworts spread to new areas by fragmentations being carried on a boat‘s hull, deck, ballast, propeller, or trailers that are not properly cleaned. The plant is also be transported by waterfowl flying from lake to lake.
Annual Cycle: Swollen bladderwort reproduces from small fragments and from seed. A Florida botanist reports that when plants become stranded on mud, they can produce long threadlike branches with each bearing a tiny tuber at its tip. When not in flower, swollen bladderwort floats below the water's surface.
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Look Alikes: May be confused for white water buttercup (Ranunculus aquatilis) and watermilfoils (Myriophyllum spp.) when without bladders or flowers. When not flowering, identifying native bladderwort plants from swollen bladderwort is very difficult. Other bladderworts (Utricularia intermedia and U. minor) are much smaller with flowers less than 9 mm wide. U. intermedia has bladders on separate stems from the "leaves‖.
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Mollusks
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Bithynia tentaculata Mud Bithynia
Habitat: Commonly found in freshwater ponds, shallow lakes, and canals. This species is found on the substrate in fall and winter and on aquatic macrophytes in warmer months. It lives mostly in shoals, but is found at depths up to 5 m.
Description: The Mud bithynia has a shiny pale brown shell, oval in shape, with a relatively large and rounded spire consisting of 5–6 somewhat flattened whorls, no umbilicus, and a very thick lip. The aperture is less than half the height of the shell. Adult snails possess a white, calcareous, tear-drop to oval-shaped operculum with distinct concentric rings. The operculum of juveniles, however, is spirally marked. The operculum is always located very close to the aperture of the shell). The animal itself has pointed, long tentacles and a simple foot with the right cervical lobe acting as a channel for water. The shell is usually no larger than 12–15 mm; the snail is sexually mature by the time it reaches 8 mm in size.
Principal Modes of Transport & Introduction: They can spread by attaching to aquatic plants, boats, anchors, decoy anchors, other recreational gear and equipment placed in the water. Some movement by waterfowl may also spread this invasive to new waters.
Annual Cycle: It lays its eggs on rocks, wood and shells in organized aggregates arranged in double rows, in clumps of 1–77. Egg-laying occurs from May to July when water temperature is 20°C or higher, and sometimes a second time in October and November by females born early in the year. The
81 | P a g e density of eggs on the substrate can sometimes reach 155 clumps/m2. Fecundity may reach up to 347 eggs and is greatest for the 2nd year class. Eggs hatch in three weeks to three months, depending on water temperature. Oocytes develop poorly at temperatures of 30 - 34°C. Growth usually does not occur from September to May.
Look Alikes: Mud Bithynias are difficult for non-specialists to conclusively identify. Native snail species and young nonnative mystery snails could look similar to them . Distribution:
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Cipangopaludina chinensis Chinese Mystery Snail
Habitat: Chinese mystery snails prefer the quiet water of lakes, ponds, roadside ditches and slower portions of streams. Though they spend a good portion of their lives under the water surface, half buried in the bottom sediments, Chinese mystery snails may also be encountered with their trap doors sealed up tight, floating along at the water's surface.
Description: The Chinese mystery snail can be identified by their relatively large globose shells and concentrically marked opercula. The Chinese mystery snail has a width to height ratio of 0.74– 0.82, the shell has 6.0–7.0 whorls, and the inner coloration is white to pale blue. This species has a small and round umbilicus and the spire is produced at an angle of 65–80º. It exhibits light coloration as a juvenile and olive green, greenish brown, brown or reddish brown pigmentation as an adult. In juveniles, the last shell whorl displays a distinct carina, and the shell contains grooves with 20 striae/mm between each groove. Juveniles also have a detailed pattern on their periostracum consisting of 2 apical and 3 body whorl rows of hairs with long hooks on the ends, distinct ridges and many other hairs with short hooks . Principal Modes of Transport & Introduction: It is believed that most infestations are the result of people dumping aquariums into the lakes.
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Annual Cycle: This species is ovoviviparous. Females live up to 5 years, while males live up to 3, occasionally 4 years. All females generally contain embryos from May to August and young are born from June through October in eastern North America in shallow water, then females begin migrating to deeper water for the winter in the fall. Females bear more young in their 4th and 5th years than in other years
Look Alikes: Once in a body of water, the Chinese mystery snail may be transported, as adults or tiny juveniles, via bait buckets and water holding areas on boats.
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Corbicula fluminea Asian Clam
Habitat: C. fluminea is found in lakes and streams of all sizes with silt, mud, sand, and gravel substrate. They can tolerate salinities of up to 13 ppt for short periods andd temperatures between 2 and 30 degrees Celsius. It prefers fine, clean sand, clay, and coarse sand substrates. It is usually found in moving water because it requires high levels of dissolved oxygen. C. fluminea is generally intolerant of pollution.
Description: A small light-colored bivalve with shell ornamented by distinct, concentric sulcations, anterior and posterior lateral teeth with many fine serrations. The light-colored shell morph has a yellow- green to light brown periostracum and white to light blue or light purple nacre while the darker shell morph has a dark olive green to black periostracum and deep royal blue nacre. The shells of the yellow morphs were straw yellow on the outside and white on the inside; those of brown morphs were dark brown and purple, respectively. Asian clams are filter feeders that remove particles from the water column. They can be found at the sediment suface or slightly buried. The ability to reproduce rapidly coupled with low tolerance of cold temperatures can produce wild swings in populaton sizes from year to year in northern water bodies.
Principal Modes of Transport & Introduction: C. fluminea spreads when it is attached to boats or carried in ballast water, used as bait, sold through the aquarium trade, and carried with water currents.
Annual Cycle: C. fluminea is a hermaphrodite (both sexes are found on one organism) and is capable of self- fertilisation. Sperm is released into the water, caught by another clam, and brooded in the gills. The larvae are released through the excurrent siphon and sent out into the water column. Spawning can continue year around in water temperatures higher than 16 degrees Celsius. The water temperature must be above 16 degrees Celsius for the clams to release their larvae.
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Spawning occurs from spring to fall. Maximum densities of C. fluminea can range from 10,000 to 20,000 per square meter, and a single clam can release an average of 400 of juveniles a day and up to 70,000 per year. Reproductive rates are highest in fall . Larvae spawned late in spring and early summer can reach sexual maturity by the next fall. C. fluminea maximum lifespan is 7 years, but it varies according to habitat, with an average lifespan of 2 to 4 years.
Look Alike: C. fluminea is easily confused with Corbicula fluminalis, C. fluminalis is overall smallerl in size. Most easily, they can be distinguished by the amount of ribs on the shell; C. fluminea has 7 to 14 ribs per cm, C. fluminalis 13 to 28.
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Dreissena bugensis Quagga Mussels
Habitat: They can live in waters ranging from warm and shallow to deep and cold. They are also able to tolerate brackish water.
Description: The quagga mussel shell has a rounded angle or carina. The quagga is light tan to almost white, with narrow stripes or mottled lines. It is fan-shaped, with pointed edges at either side. The ventral (bottom-side where the 2 shells attach) side of the quagga mussel is convex which makes the quagga mussel topple over when placed ventral side down on a flat surface. Quagga mussels feed all year, even in winter when its cousin the zebra mussel lies dormant. Some researchers believe that Lake Erie's dead zone is likely the partial work of the tiny quagga mussel‘s non-stop feeding, its ability to live in deep water (it has been found at depths up to 130m) and the excretion of phosphorous with its waste.
Principal Modes of Transport & Introduction: Quagga mussels are spread to new areas by being carried on a boat‘s hull, deck, ballasts, propeller, or trailers that are not properly cleaned.
Annual Cycle: The quagga mussel is a prolific breeder, possibly contributing to its spread and abundance. Dreissena are dioecious (either male or female) with external fertilization. A fully mature female mussel is capable of producing up to one million eggs per year. After fertilization, pelagic microscopic larvae, or veligers, develop within a few days and these veligers soon acquire minute bivalve shells. Free-swimming veligers drift with the currents for three to four weeks
87 | P a g e feeding by their hair-like cilia while trying to locate suitable substrata to settle and secure byssal threads.
Look Alikes: Zebra mussels are similar in appearance to the quagga mussel. When placed on a surface zebra mussels are stable on their flattened underside while quagga mussels, lacking a flat underside, will fall over.
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Dreissena polymorpha Zebra Mussels
Habitat: Zebra mussels and their close relative the Quagga mussel are the only freshwater mollusks that can firmly attach themselves to solid objects through the use of thread-like structures call ‗byssal threads‘. They are generally found in shallow (6-30 feet deep), algae-rich water.
Description: The zebra mussel (Dreissena polymorpha) is a tiny (1/8-inch to 2-inch) bottom-dwelling clam. Zebra mussels look like small clams with a yellowish or brownish D-shaped shell, usually with alternating dark- and light-colored stripes. They can be up to two inches long, but most are under an inch. Zebra mussels usually grow in clusters containing numerous individuals.
Principal Modes of Transport & Introduction: Zebra mussels are spread to new areas by being carried on a boat‘s hull, deck, ballasts, propeller, or trailers that are not properly cleaned.
Annual Cycle: Zebra mussels usually reach reproductive maturity by the end of their first year. Reproduction occurs through spawning when sperm and eggs are released into the water. Spawning peaks at water temperatures of about 68 degrees F. A fertilized egg results in a free-swimming, planktonic larva called a ‗veliger.‘ This veliger remains suspended in the water column for one to five weeks, and then begins to sink, eventually attaching to a stable surface (e.g., rocks, dock pilings, aquatic weeds, water intakes, boat hulls) on which to live, grow and reproduce. They attach to these surfaces using adhesive structures called byssal threads.
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Zebra mussels feed by drawing water into their bodies and filtering out most of the suspended microscopic plants, animals and debris for food. This process can lead to increased water clarity and a depleted food supply for other aquatic organisms, including fish. The higher light penetration fosters growth of rooted aquatic plants which, although creating more habitats for small fish, may inhibit the larger, predatory fish from finding their food. This thicker plant growth can also interfere with boaters, anglers and swimmers. Zebra mussel infestations may also promote the growth of blue-green algae, since they avoid consuming this type of algae but not others. Zebra mussels attach to the shells of native mussels in great masses, effectively smothering them.
Look Alikes: Zebra mussels are similar in appearance to the quagga mussel (Dreissena bugensis). When placed on a surface zebra mussels are stable on their flattened underside while quagga mussels, lacking a flat underside, will fall over.
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Elimia virginica Piedmont Elimia Snail
Habitat: Found in freshwater rivers and streams with cobble bottoms and boulders. Pleurocerids are usually found in lotic erosional environments, in riffles or shoals with rock or sand substrate, and especially frequently on rocks in slower areas of medium size reaches. Elimia virginica usually inhabits slow to medium velocity rivers and streams with firm and clean gravel, cobble and rock substrate (Smith 1980). Pleurocerids in general are sensitive to abiotic stresses, and the E. virginica is not tolerant to siltation. the snail was found to inhabit regions with water temperatures up to 27.5 degrees C, dissolved oxygen between 7 and 14 ppm, CaCO3 concentration from 42-160 ppm, pH from 7.6-9.0 and CO2 concentration from 0-10 ppm.
Description: Elimia virginica belongs to the family Pleuroceridae, a group of snails with thick, elongated shells. The opercula are withdrawn, proteinaceous, corneous, and paucispiral. The shells are dextral and have a very high and narrow spire, with little space in the incisions between the whorls. This species has two distinct shell morphologies, one smooth and one lirate (i.e. finely lined or grooved). Specimens of this species often vary in coloration; in general, E. virginica is yellow to chestnut in hue, but it may or may not exhibit 2 darker brown spiral bands. Juveniles (snails with an aperture height of no more than 7 mm) display the banding more frequently than adults. It is straightforward to distinguish the female of this species by way of the external genital sinus. Elimia virginica from New York State and the Connecticut River range from 27– 33 mm high, with an aperture height of 9–12 mm .
Principal Modes of Transport & Introduction: They can spread by attaching to aquatic plants, boats, anchors, decoy anchors, other recreational gear and equipment placed in the water. Some movement by waterfowl may also spread this invasive to new waters.
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Annual Cycle: E. virginica is dioecious and lays its eggs from spring to summer, in particular in June and July. This species, unlike softer shelled physid snails, grows very slowly, and has the lowest intrinsic rate of increase (this means that populations grow very slowly).Individuals of this species are often sexually mature within one year; and can live 5 years.
Look Alike: E. virginica can be confused with the very similar liver elimia (Elimia livescens ) and the sharp hornsnail (Pleurocera acuta).
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Fusconaia flava Wabash pigtoe
Habitat: The Wabash pigtoe is found from creeks to large rivers with moderate current in mud, sand or gravel. However, it is more common in streams than rivers. On the Huron River, it seemed to prefer a firm bottom of sand and fine gravel. In the Clinton it was found on a firm sand bottom.
Description: The Wabash pigtoe is up to 7.6 cm (3 inches) long , and is triangular to quadrate in shape. The shapes of headwater to river forms vary. Headwater forms are more rounded and river forms have a more prominent posterior ridge. The shell is fairly thick and compressed. The anterior end is gently rounded, the posterior end bluntly pointed. The dorsal margin is short and straight. The ventral margin is rounded anteriorly and bluntly pointed posteriorly. Umbos are broad and raised slightly above the hinge line. The beak sculpture has three to four weak concentric bars. The periostracum (outer shell layer) is smooth, yellowish-brown to dark brown in older individuals. Faint green rays are visible in younger individuals. On the inner shell, the left valve has two pseudocardinal teeth, which are heavy, rough, and serrated. The anterior tooth is narrow and elongate, the posterior one is heavy and triangular. The two lateral teeth are short and straight. The right valve has one large, serrated, pseudocardinal tooth, and one (sometimes two) are short, straight and stout. The beak cavity is deep and wide. Although the nacre is white, occasionally it is has a pink or salmon tint and is iridescent posteriorly.
Principal Modes of Transport & Introduction: They can spread by attaching to aquatic plants, boats, anchors, decoy anchors, other recreational gear and equipment placed in the water. Some movement by waterfowl may also spread this invasive to new waters
Annual Cycle: Age to sexual maturity for this species is unknown. They are gonochoristic (sexes are separate) and viviparous. The glochidia, which are the larval stage of the mussels, are released live from the female after they are fully developed. In general, gametogenesis in the Fusconaia flava is
93 | P a g e initiated by increasing water temperatures. The general life cycle of a Fusconaia flava, includes open fertilization. Males release sperm into the water, which is taken in by the females through their respiratory current. The eggs are internally fertilized in the suprabranchial chambers, then pass into water tubes of the gills, where they develop into glochidia. Fusconaia flava is a short- term brooder. Females brood fertilized eggs in their marsupial pouch. The fertilized eggs develop into glochidia. There is no parental investment after the female releases the glochidia.
Look Alike: Fusconaia flava can be easily confused with Pleurobema sintoxia, particularly in upper reaches of river systems. The sulcus of Fusconaia flava becomes more prominent in more downstream populations, making it more distinguishable from Pleurobema sintoxia. The Wabash pigtoe generally has a deeper beak cavity. When present in females, glochidial packets from the Wabash pigtoe also tend to be orangish while the round pigtoe has white glochidial packets.
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Gillia altilis Buffalo Pebblesnail
Habitat: The Buffalo pebblesnail is usually found in freshwater stream environments. Its globose shell is adapted for inhabiting high-velocity lotic environments, because it allows for a large, muscular foot that can suction to rocks. It also commonly inhabits warmwater, shallow lacustrine habitats with mud substrate.
Description: The shell of this species is inflated but still conical, and usually yellow to green, with 2–4 whorls when eroded and ~4.5 when intact. Each whorl is distinctly shouldered. The umbilicus is either not apparent or very small. The columella is not thickened and the shell can be thin or thick. The shell aperture is oval to ear-shaped. When viewed laterally, the outer lip of the shell bends forward. The chitinous, oval, yellow to green operculum shows paucispiral markings and has a subcentral nucleus. The mantle is black or shows dark pigmentation, which is also seen in the nape, the anterior part of the snout, the top of the tentacles, and along the edge of the peristome. The radula of the Buffalo pebblesnail looks like a single serrated blade with 51–55 tooth rows.
Principal Modes of Transport & Introduction: They can spread by attaching to aquatic plants, boats, anchors, decoy anchors, other recreational gear and equipment placed in the water. Some movement by waterfowl may also spread this invasive to new waters.
Annual Cycle: The Buffalo pebblesnail exhibits separate sexes and sperm is transmitted to the female through a penis that extends from the nape of the male. This species lays its eggs in hemisphere-shaped capsules, singly or in clumps up to six at a time on leaves and stems of macrophytes
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Look Alike: It is very difficult for non-specialists to conclusively identify. Native snail species could look similar to them.
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Pisidium amnicum Greater European Pea Clam
Habitat: The Greater European Pea Clam is found in freshwater lakes and slow-moving rivers with soft bottoms; water temperatures of 1-21ºC. Pea Clams are typically a rheophilic species in its native range but can also occur in lakes. It prefers sand but has also been recorded on mud and gravel. It can survive anoxic conditions under ice cover but may be limited in some upper river reaches where temperatures do not exceed 15–17ºC in July. Pea Clams are capable of closing its shell to induce anoxia, metabolic quiescence, and anaerobiosis, and can survive for 200 days at 0ºC.
Description: This small bivalve has a height to length ratio of 0.74–0.81 and is relatively long, oval shaped, and heavily striated with a shiny yellow or brown epidermis. The beaks are located towards the posterior by about 2/3 of the total shell length. Inside the shell, the cardinal teeth are closer to the anterior lateral teeth than to the posterior lateral teeth, the 2nd cardinal tooth is a thick peg covered by the thinner 4th cardinal, and the 3rd cardinal curves around the 2nd cardinal. In live specimens there is only an anal siphon.
Principal Modes of Transport & Introduction: Pea clams are spread to new areas by being carried on a boat‘s hull, deck, ballasts, propeller, or trailers that are not properly cleaned.
Annual Cycle: Pea Clams can live up to 3 years, mature at 4 mm. It is hermaphroditic, ovoviviparous, and can undergo cross-fertilization. Eggs incubated in a brood-sac in the parent; embryos develop and are released as miniature adults. The pea clam is iteroparous, reproducing twice, once at age 2 and once at age 3. Recruitment takes place when water temperatures reach 15–20ºC. Maturation of individuals and egg-laying occur between July and October, and eggs are brooded for around 9– 10 months. The number of embryos per adult varies from 5–29. Lifespan is typically 1–3 years.
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Look Alike: It is very difficult to distinguish between the fingernail clam and the pea clam.
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Radix auricularia European Ear Snail
Habitat: Found in freshwater lakes, ponds, and slow-moving rivers with mud bottoms. R. auricularia can live on boulders or vegetation in low or high flow environments and is capable of tolerating anoxic conditions, but tends to prefer very lentic waters in lakes, bogs or slow rivers where there is a silt substrate. It can tolerate polysaprobic waters, or areas of major pollution and anoxia with high concentrations of organic matter, sulphides and bacteria.
Description: The ear-shaped aperture, which contains no operculum, is around 5 times higher than the spire. The shell is thin and very inflated such that the last whorl comprises 90% of its volume. The umbilicus is either wide or covered, the shell has a rounded and broad spire that pinches in steeply at the apex, and there are 4–5 whorls with deep sutures between them. The color of the shell is yellow, beige or tan. The mantle is pigmented with a line of dark spots along its edge. This species also has tentacles that are lobate, fan-shaped and wider than they are high. The blood contains blue hemocyanin. This species can grow to ~30 mm in height and 25 mm in width as a full grown adult. However, most individuals in a population only grow to approximately half the maximum size.
Principal Modes of Transport & Introduction: It is believed that most infestations are the result of people dumping aquariums into the lakes. However, it may also be introduced by on pieces of plants.
Annual Cycle: It is a hermaphrodite, undergoing oogenesis in spring as daylight hours increase and spermatogenesis in late summer and early fall as daylight hours decrease. It breeds biennially. Eggs develop faster as temperature increases from 10ºC upward but fail to survive and develop at 36ºC.
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Look Alikes: European ear snail is very similar and easily confused with the native snails.
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Rangia cuneata Atlantic Rangia
Habitat: Rangia cuneata inhabits low salinity estuarine habitats and is as such most commonly found in areas with salinities from 5-15 PSU. R. cuneata possess both extracellular (blood and body fluid) and intracellular mechanisms of osmoregulation, which enables them to respond to sudden salinity changes in many estuaries. They can cross the 'horohalinicum', the 5-8 PSU salinity boundary which usually divides fresh and salt-water invertebrates, making them one of the few freshwater clams to become established in brackish water as such thriving in a zone unfavorable for many animals. Competition and predation may explain its scarcity in high salinity environments. A combination of low salinity, high turbidity and a soft substrate of sand, mud and vegetation appear to be the most favorable habitat for R. cuneata. Although larvae prefer coarser sediment for settlement, adults are often found in muddy sediments.
Description: The valves of Rangia cuneata are thick and heavy, with a strong, rather smooth pale brown periostracum. The shells are equivalve, but inequilateral with the prominent umbo curved anteriorly. An external ligament is absent or invisible, but the dark brown internal ligament lies in a deep, triangular pit immediately below and behind the beaks. Both valves have two cardinal teeth, forming an inverted V-shaped projection. The upper surface of the long posterior lateral teeth is serrated. The inside of the shell is glossy white, with a distinct, small pallial sinus, reaching to a point halfway below the posterior lateral. The pallial line is tenuous. Rangia cuneata is a non selective filter-feeder, turning large quantities of plant detritus and phytoplankton into clam biomass but the species also appears to obtain organic matter and phosphate from the sediment by direct ingestion or by feeding on bacteria associated with these materials.
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Principal Modes of Transport & Introduction: Rangia cuneata spreads when it is carried in ballast water, sold through the aquarium trade, and carried with water currents.
Annual Cycle: It was found that gametogenesis was initiated when the water temperature rose above 15 °C and with salinities above 0 PSU or below 15 PSU. Despite the broad tolerance of adults to environmental changes, embryos are much more vulnerable; they do not develop at 0 PSU, with 18-29 °C and 6-10 PSU being optimal conditions. Larvae however, tolerate 8-32 °C and 2-20 PSU. Growth of larvae was best at high salinities and high temperatures as the survival of the larvae is reduced by the interaction of temperature and salinity at low salinity – high temperature and high salinity – low temperature combination. Larvae are capable of selecting substrates, based on physical, biological and chemical factors but although they prefer coarser sediment, this is not necessary for settlement and metamorphosis.
Look Alike: Rangia cuneata look very similar to native clams.
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Sphaerium corneum European Fingernail Clam
Habitat: The fingernail clam is found in freshwater lakes and slow-moving rivers; prefers eutrophic, shallow waters with vegetation; lives in the sediment. It cannot tolerate extremely high organic pollution. Nor does it tolerate desiccation well. The fingernail clam has a high capacity for anaerobiosis and is able to survive anoxic conditions for around 400 days at 0ºC and for 9 days at 20ºC. It prefers hard waters with high magnesium, calcium, and bicarbonate concentrations. It is found on fine sand, mud, silt, organic matter, and sometimes on gravel.
Description: This fingernail clam has an oval, thin shelled, lustrous brown to gray, and somewhat inflated shell with a height to length ratio of 0.80–0.88. Juveniles‘ shells are more yellow. The dorsal shell margin is curved and there are low central beaks with straight edges on either side. The shell is covered in evenly spaced striae that become finer and fade out toward the beaks. The narrow 4th and 2nd cardinal teeth are very close to parallel and the former overlaps the latter. The narrow and curved 3rd cardinal is parallel to the hinge plate and expanded and often bifurcates posteriorly. It can grow to around 9–13.5 mm in length. The fingernail clam is mainly a filter feeder but can also deposit feed. It prefers diatoms but also ingests other types of phytoplankton.
Principal Modes of Transport & Introduction: Fingernail clams are spread to new areas by being carried on a boat‘s hull, deck, ballasts, propeller, or trailers that are not properly cleaned.
Annual Cycle: fingernail clams are self-fertilizing, the young developing inside the water tubes of the adult; mussels have a very elaborate and intriguing process; the larvae, called glochidia, develop inside the adult female and are released into the water where they eventually attach onto a host fish;
103 | P a g e then they parasitize the fish for about two weeks until they drop off and develop on the stream bottom into an adult.
Look Alike: The European fingernail clam looks very similar to the pea clams that are in the same family.
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Valvata piscinalis European Stream Valvata
Habitat: Found in freshwater lakes and streams. In its native range, this species‘ presence has been associated with oligotrophic nearshore zones, clear-water habitats more than turbid water, sparsely vegetated lakes or sites dominated by Chara spp. and Potamogeton spp., littoral habitats with high siltation rates, lentic and stagnant waters or slow streams, fine substrates (mud, silt and sand) – especially during hibernation, and aquatic macrophytes – for laying its egg masses. The snail appears to be somewhat resistant to declines in macrophyte cover, because populations have been recorded to survive in ponds after vegetation cover almost completely disappeared. This species is found anywhere from 0.5–23m. The European stream valvata tolerates varying calcium concentrations and generally does not require very high temperatures to survive. Individuals can overwinter in mud, often experiencing growth during this cold period, although some populations may experience mortality in frozen littoral zones.
Description: The European stream valvata has a somewhat pinched aperture and an attenuate spire. Spire height tends to increases in more eutrophic conditions. Shells of this species often exhibit 4–5 whorls and are white to beige with more orange to red pigmentation apically. The operculum shows spiral markings of around 10 turns, originating almost centrally. The animals are yellow colored, spotted grey and white, with blue eyes and darker pigmentation on the snout, mantle and base of the penis. Valvatids all exhibit a bipectinate ctenidium (respiratory organ) that is visible as the animal moves. Mature adult European stream valvata snails are 5 mm high and 3–5 mm wide. The species is an efficient feeder, grazing on epiphytic algae and detritus, and in more eutrophic environments is capable of filter feeding on suspended organic matter and algae. They can also rasp off pieces of aquatic vegetation.
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Principal Modes of Transport & Introduction: The European stream valvata are spread to new areas by being carried on a boat‘s hull, deck, ballasts, propeller, or trailers that are not properly cleaned. People dumping aquariums may also be a means of introduction to new areas.
Annual Cycle: The European stream valvata is known for its rapid growth and high fecundity. It reproduces as a hermaphrodite, one individual acting as the male and the other as the female, and has no free larval stage. It may spawn 2 or 3 times in a year, laying up to 150 eggs at a time which are deposited on vegetation. Hatching normally occurs in 15–30 days. Individuals breed around the age of 1 and usually die at 13–21 months.
Look Alike: The European stream valvata snail can be confused with V. sincera, a native species; however, the native species has a more spherical aperture, a wider umbilicus, a conical spire and more widely spaced and rough growth lines on the shell in comparison with the introduced species.
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Viviparus georgianus Banded Mystery Snail
Habitat: Found in lakes and slow-moving rivers with mud bottoms. his species thrives in eutrophic lentic environments such as lakes, ponds and some low-flow streams. The banded mystery snail often lives at high densities, sometimes up to around 864/m2.
Description: The banded mystery snail has a relatively globose, dextral shell with 4–5 whorls separated by distinct sutures. The outer lip of the shell is quite thin and the overall coloration is yellow-green. There are abundant rows of hairs with distinctly hooked ends and ridges on the periostracum. The umbilicus is narrow or not apparent, and the operculum is round to oval with concentric circular markings that radiate from an off-centre origin located towards the top left. There are always 4 darkly pigmented bands that wrap around the shell spirally, but which are sometimes only visible from inside. One-year old snails are 12–17 mm high; at 2 years, 17–21 mm high; and at 3 years, 21–30 mm high. The banded mystery snail is known to be a facultative or even obligate filter-feeder. But standard grazing also seems to be an option.
Principal Modes of Transport & Introduction: It is believed that most infestations are the result of people dumping aquariums into the lakes.
Annual Cycle: The Banded mystery snail breeds and lives in shallow waters, often amongst macrophytes, in spring to fall, then moves out to deeper areas in the fall in order to overwinter away from shore. Most growth generally occurs when waters become warmer in spring and summer, although reduced growth continues in winter.
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The banded mystery snail lays eggs singly in albumen-filled capsules. Females generally brood eggs for 9–10 months. Females can brood more than one batch of young at a time and the number of young in one brood is positively related to the size of the female. Female banded mystery snails live 28 – 48 and males live 18 – 36 months.
Look Alikes: The banded mystery snail can be mistaken for many native snails. They are sometimes confused with zebra mussels too.
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Arthropods
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Eriocheir sinensis Chinese Mitten Crab
Habitat: Chinese mitten crabs occur in both fresh and salt water.
Description: Its claws are equal in size and covered with fur-like setae (soft bristles), or mittens, and eight sharp-tipped walking legs (no swimming legs). The adult carapace (body shell) is 8-10cm wide, and light brown to olive green in color.
The mitten crab is an omnivorous predator that will devour just about anything it can catch and swallow, including native freshwater crayfish. Mitten crabs also burrow, and in large numbers can cause substantial damage to unprotected riverbanks.
Principal Modes of Transport & Introduction: The mitten crab is a delicacy and crabs have been imported live illegally to markets.
Annual Cycle: At the age of two to five years old the crabs leave their burrows along the riverbanks of freshwater rivers and tributaries to mate and spawn in saltwater estuaries, migrating overland when necessary. Once the crabs have mated, the males are believed to die, leaving the females to brood the eggs. In the spring the eggs hatch into larvae and after about six to seven weeks these metamorphose into juvenile crabs, which then migrate back up the river into freshwater to complete the life cycle.
Look Alikes: Small mitten crabs may be confused with the Harris mud crab, because of their similar size and appearance.
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Gammarus fasciatus Freshwater Shrimp
Habitat: G. fasciatus is a freshwater benthic species that can tolerate some very low levels of salinity. It occurs in both rivers and lakes and is particular abundant in shallow well oxygenated areas. G. fasciatus survives well at water temperatures around 10–15°C. Starting at 20°C, temperatures are less tolerable. The length of time G. fasciatus can tolerate a specific water temperature above 20°C decreases with increasing temperature. Temperatures of around 34–35°C and more cause relatively rapid mortality. G. fasciatus is frequently associated with thick macrophyte beds.
Description: The 1st antenna, which is typically longer than the 2nd antenna of this species, exhibits a 2–7 segmented accessory flagellum. There are no cylindrical appendages on the coxal gills. The uronites have obvious dorsal spines and the telson shows a deep cleft, almost to the joint with the body. G. fasciatus can grow to 14 mm in length. G. fasciatus feeds on detritus and sediments, coarse and fine particulate organic matter, filamentous algae, diatoms, animal matter, its own species, and zooplankton such as Daphnia spp. smaller individuals feed on detritus more frequently.
Principal Modes of Transport & Introduction: G. fasciatus are transported in either solid or liquid ballast, arrival on aquatic plants, arrival with stocked fish, dispersal via canals, and/or introduction via fish bait.
Annual Cycle: The mating process is preceded by preliminary behaviors such as special movements, like dances performed by the male in order to attract the female. The legs play an important role in reproduction. The sexually mature male clasps the female with the second pair of his legs and carries her with him as he is swimming or walking. The male pleopods do not function in copulation. The ova develop in the brood pouch, which are projections of the female legs. Hatching occurs after all the appendages of the embryo have developed. The young usually
112 | P a g e remain in the mother's marsupium until it is delivered by the female. Unlike other Crustacea, the young G. fasciatus do not undergo metamorphosis. G. fasciatus can produce on the order of 20 embryos in a given clutch.
Look Alike: Freshwater shrimp are very difficult to differentiate with the naked eye.
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Hemigrapsus sanguineus Asian Shore Crab
Habitat: This versatile crab inhabits any shallow hard-bottom intertidal or sometimes subtidal habitat. They can live on artificial structures and on mussel beds and oyster reefs. They also tend to aggregate at high densities under rocks where they overlap habitats with native crab species. Hemigrapsus can tolerate wide ranges of salinity and temperature as well as damp conditions in the upper intertidal regions. It is actively breeding and expanding its population within its nonnative range. Because the species is tolerant of a wide range of environmental conditions
Description: This shore crab has a square-shaped shell with 3 spines on each side of the carapace. Males have a fleshy, bulb-like structure at the base of the moveable claw finger. Carapace colors can be green, red, orangish brown or purple. Claws have red spots; legs are light and dark banded. Adult carapace width ranges from 1.4 inches to 1.7 inches. This crab being an opportunistic omnivore (it feeds on macroalgae, salt marsh grass, larval and juvenile fish, and small invertebrates), it could potentially negatively impact populations of such native species as fish, shellfish and other crabs by predation and by general food web effects. It could also out-compete native mud crabs, blue crabs and lobsters.
Principal Modes of Transport & Introduction: The shore crabs are spread to new areas by boats ballast water movement and exchange in many different areas.
Annual Cycle: This species is highly reproductive, breeding from May to September, with females capable of producing three to four clutches per season, each containing up to 50,000 eggs. Free-floating larvae can be transported over long distances during the month that it takes them to develop into juveniles and settle out of the water column.
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Orconectes rusticus Rusty Crayfish
Habitat: Rusty crayfish inhabit lakes, ponds and streams. They generally dig small pockets under rocks and other debris, though under some circumstances they may dig more substantial burrows. Unlike some other crayfish species that may inhabit seasonal waterbodies, the Rusty crayfish needs permanent (year-round) water.
Description Rusty crayfish have robust claws with black bands at the tips and an oval gap when closed. They also have dark, rusty spots on each side of their carapace as though you picked up the crayfish with rust-colored paint on your forefinger and thumb. (The spots may not always be present or well developed.) Like all crayfish, they are an opportunistic omnivore. Rusty crayfish feed on a variety of aquatic plants, benthic invertebrates (like aquatic worms, snails, leeches, clams, aquatic insects and crustaceans), detritus (decaying plants and animals and the associated bacteria and fungi), fish eggs, and small fish. The Rusty crayfish is an aggressive species, and is known to displace native crayfish
Principal Modes of Transport & Introduction: The Rusty crayfish was probably first introduced by non-resident anglers who brought them here to use as fishing bait. Once the crayfish populations were well established, the sale of trapped Rusty crayfish by bait dealers may have increased the rate of spread.
Annual Cycle: Rusty crayfish mate in late summer, early fall or early spring. Males transfer sperm to the females, but external fertilization does not occur until the water temperature increases. The expelled eggs are fertilized by the sperm and are attached to the swimmerets underneath the crayfish's abdomen with white patches. These white patches are called glair, and the eggs adhere to this mucus-like substance.
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Depending on the water temperature, rusty crayfish eggs hatch in 3 to 6 weeks. Young crayfish will undergo 3 to 4 molts while attached to the mother's swimmerets and remain with the mother for several weeks. Once the young have left, they undergo 8 to 10 molts before becoming mature. Maturity usually occurs the following year. Maturity is considered to be at a length of 4.4 cm. After mature, adult males will molt twice annually, and adult females will molt once annually.
Look Alikes: May be confused for the Nail polish crayfish (Orconectes immunes), The Northern Clearwater Crayfish (Orconectes propinquus) and, The Northern crayfish (Orconectes virilis).
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Zooplankton
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Bythotrephes longimanus Spiny Waterflea
Habitat: Spiny waterfleas are more common in deep, cool lakes. However, they also inhabit warmer lakes where surface water temperatures exceed 25° C.
Description: The creature is small (1 to 1.5 cm long) with transparent exoskeleton, a large black eye spot on the side of the head, and four pairs of legs. Most distinctive is the crustacean's long, barbed tail spine. Spiny waterfleas are often first noticed by anglers, when they become entangled in fishing lines. When the line is pulled from the water, something resembling tiny straight pins waving about perpendicular to the line may be noticed. These are the miniscule creatures, raising and lowering their tails as they cling to the line.
Once well established in the waterbody, spiny waterfleas compete directly with other zooplankton feeders in the ecosystem (eating up to three times as much food as similar species). Their sharp spine prevents fish of a certain size class from eating them. It is believed that both of these impacts have the potential to trigger disturbances throughout the aquatic food web.
Principal Modes of Transport & Introduction: The Spiny waterflea may spread to new areas by being carried on a boat‘s hull, deck, propeller, or trailers that are not properly cleaned. Fishing equipment and bait buckets are also a means of transport for the spiny water flea.
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Annual Cycle: Spiny waterfleas reproduce rapidly, (both sexually and asexually) producing numerous offspring during the growing season, and "resting eggs" that overwinter in the sediments.
Look Alikes: The spiny waterflea very closely resembles the fish-hook waterflea (Cercopagus pengoi).
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Cercopagis pengoi Fish-hook Waterflea
Habitat: The fish-hook water flea can tolerant a wide range of salinity and temperatures.
Description: Body size from 1-3 mm in length without tail, 6-13 mm with tail; tail has three pairs of barbs and a characteristic loop near the end.
Principal Modes of Transport & Introduction: The Spiny water flea may spread to new areas by being carried on a boat‘s hull, deck, propeller, or trailers that are not properly cleaned. Fishing equipment and bait buckets are also a means of transport for the spiny water flea.
Annual Cycle: The Water Flea usually reproduces asexually in the summer months to take advantage of the abundant food sources, while sexual reproduction occurs later on in the year when water temperature drops. Dormant eggs laid in late autumn helps the dispersal of the species and enable the species to survive the inhospitable conditions of the winter.
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Look Alikes: The fish-hood water flea very closely resembles the spiny water flea.
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Daphnia lumholtzi Water Flea
Habitat: Daphnia or ―water fleas‖ have rapidly invaded a wide variety of habitats, including flood-plain lakes, large rivers and lakes. Water fleas are freshwater living. They are tolerant of poor water quality and can even survive in waters with virtually no dissolved oxygen. Water fleas are very tolerant of a wide range of temperatures and are especially tolerant of high temperatures as a result of its tropical/sub-tropical origins.
Description Water fleas are really small crustaceans that belong to a group of organisms called cladocerans, and are relatives of freshwater shrimp. The most distinguishing characteristics of this daphnia are the long helmet and tail spines. The helmet is much larger than the native species and the tailspine is normally as long as the body length. Other distinct characteristics are the fornices that extend to a sharp point instead of being rounded and the ventral carapace margin which has approximately 10 prominent spines.
Principal Modes of Transport & Introduction: The Water flea may spread to new areas by being carried on a boat‘s hull, deck, ballast-water, propeller, or trailers that are not properly cleaned. Fishing equipment, bait buckets, and stocked fish are also a means of transport for the water flea. The resting eggs of water fleas have hairs and spines that could grip boats or other objects and thus aid dispersal.
Annual Cycle: Water fleas can reproduce asexually in great numbers through parthenogenicity often in warmer months of the year and can make up a large portion of the plankton in some water bodies. During favorable reproductive seasons Water Flea populations are comprised solely of females that can
123 | P a g e generate up to 10 offspring per individual every three days with sexual maturation of offspring occurring at 4 days old. They can also reproduce sexually via fertilization of eggs when resources are scarce. When stressors or other unfavorable conditions are present Water fleaeggs called ephippia or ―resting eggs‖ can be produced, these eggs can lay dormant under unfavorable conditions for quite some time until better conditions trigger them to hatch.
Look Alikes: Water fleas can be confused with many of the native and non-native water fleas.
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Eubosmina coregoni Waterflea
Habitat: E. coregoni are found at all depths, but it appears to prefer warm epilimnetic water and occasionally concentrates at a depth of 10m.
Description: Females of this waterflea exhibit larger and more variable traits with respect to the carapace and antennules than do males. The females‘ large antennules are located anteriorly and ventrally. The females‘ post abdominal claw is emarginate near the tip and has proximal pecten only, with 3–5 short spines. That of the male becomes very narrow distally. The anterior sensory bristle of this species is near the end of the rostrum and close to the attachment of the antennules. There is no mucro or the mucro is extremely small. The lateral headpore is close to the attachment of the mandibles but relatively far from the headshield. They range in size from 0.2–0.8 mm in length.
E. coregoni filter feeds and feeds raptorially, selecting specific phytoplankton in the water column. It specifically selects particles of 0.5–5 μm in size and thus is much more tolerant of eutrophic conditions and the presence of cyanobacteria. Larger cladocerans experience difficulty feeding in the presence of cyanobacteria because they do not feed selectively and longer algae filaments clog their filtering apparatuses.
Principal Modes of Transport & Introduction: Waterfleas are spread to new areas by boats ballast water movement and exchange in many different areas.
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Annual Cycle: Reproduction in E. coregoni can occur either between sexual females and males, or parthenogenetically in asexual females. E. coregoni can produce resting eggs that can stay dormant in the sediments for long periods of time. These eggs will hatch under the influence of specific environmental conditions.
Look Alike: Most waterfleas look similar to the naked eye.
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Eurytemora affinis Calanoid Copepod
Habitat: E. affinis is epibenthic, inhabiting both the sediments and the water column. E. affinis is found at high concentrations in warm epilimnetic and littoral waters. Some studies have suggested that this species is an epibenthic species that displays diurnal migration patterns in which 60% of the population enters the water column at night. Eurytemora affinis is a euryhaline (occurring in salt, brackish and freshwater) species.
Description: E. affinis is around 1.2–1.3 mm in length; females 1.1-1.5 mm, males 1.0-1.5 mm. This copepod exhibits a caudal ramus that is more than 3 times as long as wide and has 5 obvious setae. When viewed laterally, the maxillipeds are shorter than the width of the body. Females have a 5th leg and the 5th leg has no endopods. Adult females exhibit lateral processes, one on each side of the genital region and the metasomal wings. This species passes through 6 naupliar stages and 5 copepodite stages before it is considered mature E. affinis has been characterized as a filter feeder of nannoplankton
Principal Modes of Transport & Introduction: E. affinis are spread to new areas by a boats ballast water movement and exchange in many different areas.
Annual Cycle: E. affinis can live for up to 73 days and the juvenile stage lasts around 11–37 days. Females can lay around 2–34 sexual eggs per day, which develop in 1–14 days (taking the longest at temperatures of 5ºC and developing most quickly at temperatures around 22ºC). This species carries sexual eggs until they hatch. Diapausing eggs are usually produced in the fall and then stay in the sediments, remaining viable up to 10–18 years, even in anoxic conditions. Eggs have the ability to survive passage through the digestive tracts of various fish species. Diapausing egg production is related to short day length, low temperature, and high copepod population density.
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Skistodiaptomus pallidus Calanoid Copepod
Habitat: Found in freshwater lakes. S. pallidus occurs in beta-mesotrophic to eutrophic habitats with higher total phosphorus and total nitrogen in comparison with those inhabited by two congeners in the United States, S. pygmaeus and S. oregonensis. S. pallidus can also tolerate more suspended solids and greater turbidity than the latter two. S. pallidus is typically found in waters with a pH range of 7.5–8.6 and a conductivity range of 77–660 μScm-1. This species prefers to dwell in cool waters.
Description: The endopod of the 1st leg of this copepod species is bifurcate. Unlike some other diaptomids, the antepenultimate segment of the right 1st antenna has no distinct appendage and is not produced into a blunt point in males. The male left 5th leg is shorter than the right, reaching to the end of or slightly past the 1st segment of the right exopod. There is a scythe-like inner process on the terminal exopod segment of the male left 5th leg. Females have 3 urosomal segments, rounded metasomal wings with small sensilla, and a somewhat expanded genital segment. Females are around 0.8–1.2 mm long while males are around 0.7–1 mm long. S. pallidus feeds on phytoplankton, especially individual algae >53 μm in size. It can also selectively and intensely prey on some rotifer species.
Principal Modes of Transport & Introduction: S. pallidus could be introduced accidentally in bait buckets, in fishing equipment, or by recreational boaters.
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Annual Cycle: S. pallidus produces some eggs that go through a diapause stage before they hatch and some that do not. Breeding in general takes place from around March to November and females can produce up to around 20 eggs per brood. Diapausing eggs produced between June and October hatch from December to June of the following year. When production of diapausing eggs occurs in the summer it may aid populations to avoid fish predation. These eggs have been known to reach densities of 105 per m2 in the sediments of some habitats. Such high densities may help mitigate the effects of a poor year in reproduction and recruitment. It may take around 7 weeks for resting stages to hatch. One study found that it takes around 66 days at 10ºC and 15 days at 25ºC for development to the adult stage. There are 2–5 generations per year in different parts of this species‘ range.
Distribution:
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Pathogens & Parasites
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Argulus japonicus Parasitic Copepod
Habitat: Ectoparasitic; attaching to freshwater fishes, especially on koi carp, goldfish, and other ornamental fishes.
Description: This ectoparasitic copepod exhibits great morphological variation within and between populations. In general, individuals are shaped like shields and are golden brown with stumpy tails. Their ribbed suckers, with rods exhibiting 5–9 imbricate plates, emerge from the maxillules. The long mouth tube juts out ventrally from the head and can be fully retracted into the body. There is a preoral spine on the ventral midline and there are post-antennal spines. The first antenna displays a knob at the anterior edge and the second antenna comprises two knobbed sections in the basal part and three sections in the distal part. Swimming legs are flagellated.
Principal Modes of Transport & Introduction: It is believed that most infestations are the result of people dumping aquariums and ornamental outdoor water gardens into the lakes. Attaches to freshwater fish and can be moved to different water bodies by bait fish.
Annual Cycle: Reproduction in dioecious A. japonicus is sexual and output is high. Although mating occurs on the body of the host fish, females lay 1–9 strings of 5–226 eggs in 1–6 rows on hard substrate, which they cover in gelatinous excretions. Eggs hatch best at 20–30ºC, and hatch in 15 days at 35ºC and in 61 days at 10ºC. Newly hatched larvae survive for one or two days on nutrition from their yolk sacs but soon require nutrition from the host‘s epithelial cells and mucus. After hatching, the rest of the life cycle (excluding egg-laying), takes place on the body of the host fish in 30–100 days. A. japonicus lays eggs continuously, although in winter eggs may stay dormant until warmer temperatures conducive to hatching occur in spring. As this species develops it
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Distribution:
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Viral Hemorrhagic Septicemia of Fishes
Description: Viral hemorrhagic septicemia (VHS) virus is a serious pathogen of fresh and saltwater fish that is causing an emerging disease in the Great Lakes region of the United States and Canada. VHS virus is a rhabdovirus (rod shaped virus) that affects fish of all size and age ranges. It does not pose any threat to human health. VHS can cause hemorrhaging of fish tissue, including internal organs, and can cause the death of infected fish. Once a fish is infected with VHS, there is no known cure. Not all infected fish develop the disease, but they can carry and spread the disease to other fish. The World Organization of Animal Health has categorized VHS as a transmissible disease with the potential for profound socio-economic consequences. Because of this, they list VHS as a disease that should be reported to the international community as an exceptional epidemiological (study of diseases in large populations) occurrence.
Transmission: VHS can be spread from fish to fish through water transfer, as well as through contaminated eggs, and bait fish from infected waters. The emerald shiner is a particularly popular bait fish and is among the species afflicted.
Survivors of the disease can become lifelong carriers of the virus, contaminating water with urine, sperm, and ovarian fluids. The virus has been shown to survive two freeze/thaw cycles in a conventional freezer, suggesting both live and frozen bait could be a transmission vector. In Europe, the gray heron has spread the virus, but it does so mechanically; the virus is apparently inactive in the digestive tract of birds.
Prevention: Thoroughly cleaning boats, trailers, nets and other equipment when traveling between different lakes and streams help to prevent the spread of VHS. Chlorine bleach kills the VHS virus, but in concentrations that are much too caustic for ordinary use. Disinfecting stations can be found at various inland lake boat launches.
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Symptoms: Fish that become infected experience hemorrhaging of their internal organs, skin, and muscle. Some fish show no external symptoms, but others show signs of infection that include bulging eyes, bloated abdomens, bruised-looking reddish tints to the eyes, skin, gills and fins. Some infected fish have open sores that may look like the lesions from other diseases or from lamprey attacks. Living fish afflicted with VHS may appear listless or limp, hang just beneath the surface, or swim very abnormally, such as constant flashing circling due to the tropism of the virus for the brain.
Where is VHS found in New York?
Lake Ontario St. Lawrence River Lake Erie Conesus Lake Skaneateles Lake Seneca-Cayuga Canal Private Pond in Ransomville
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References
The Center for Aquatic and Invasive Plants. University of Florida.
The Global Invasive Species Database. Invasive Species Specialist Group (ISSG).
Maine's Interactive Field Guide to Aquatic Invaders. Maine Volunteer Lake Monitoring
Program.
Nonindigenous Aquatic Species. Ed. Pam Fuller. U.S. Department of the Interior/USGS.
NY Invasive Species Home. Cornell University.
The PLANTS Database | USDA PLANTS. U.S. Department of Agriculture.
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