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                  <text>C O L O R A D O

P A R K S

&amp;

W I L D L I F E

Invasive Species Fact Sheet:
Waterfleas
Bythotrephes longimanus (Spiny), Ceropagis pengoi (Fishhook), Daphnia lumholtzi
Waterfleas are zooplankton aquatic crustaceans that have a
jumpy or jerky mode of swimming. The Daphnia waterflea was
introduced from the aquarium trade and fish stocking. They are
native to Africa, Asia and Australia. Like invasive mussels, the
Bythotrephes and Ceropagis were introduced into the Great Lakes
from ships' ballast water coming from Eurasia. Unlike the fleas
dogs are known to carry, waterfleas are very different. They do not
live outside the water, and do not bite or harm people or pets.
Locations in Colorado:
• Bythotrephes longimanus (spiny): no known
• Ceropagis pengoi (fishhook): no known
• Daphnia lumholtzi: Chatfield State Park, Douglas Reservoir,
John Martin State Park, Navajo State Park, Pueblo Lake State
Park and Pueblo State Hatchery
Identification:
• Unique body shape: distinguished from other zooplankton by
its long tail (70% of body is tail)
• Depending on age – the spine may contain 1-4 barbs (the
older the water flea the more barbs)
• Head is mostly a single large black eye
• Swimming antennae propels flea through the water, allowing
travel between shallow and deeper waters.
• Range in length from 0.4 to 1.6 mm, depending on sex (females are larger) and age
Biology:
• Found mostly in temperate freshwater lakes, can tolerate
brackish water
• Most abundant in the summer and fall
• Can tolerate temps between 4º-30º C (39º-86ºF) and .04 to
8% salinity
• Both sexual and asexual life cycles, depending on environmental conditions
• Less than two weeks per generation with asexual life cycle
• Resting eggs may lie dormant for long periods of time, allowing the spread of these exotics into different bodies of water
• Resting eggs may also pass, unharmed, through the digestive
tracts of fish
Bythotrephes longimanus (Spiny)

Pathway of introduction and
spread:
• Eggs and adults are easily transported
in: ballast tanks, bilge water, bait buckets,
live wells, and on fishing lines, anchor lines, and nets
• It only takes one adult or egg to start an infestation
• If female waterfleas die out of water, under certain conditions
they produce eggs that resist drying and freezing, which can
establish a new infestation later
Negative impacts:
• Outcompete native juvenile fish for food, causing low survival rates, and because barbs stick in throat, are unpalatable
to juvenile fish
• Avoid predation by larger fish by retreating to deeper waters
during the day (10-20m) where they are less visible and
ascending (0-10m) at night where food is abundant and
temperatures higher, increasing metabolism and growth rates
• Their long spines can cause them to become entangled on
fishing lines and can clog eyelets of fishing rods
Management:
Once waterfleas are established, they are almost impossible to eradicate. Educating the public and following state watercraft inspection
and decontamination procedures are the best methods to contain
current infestations and prevent further spread to new waters.
Prevention:
Preventing the spread of invasive waterfleas is the best strategy;
here is what you can do:
• CLEAN all plants, animals and mud from your fishing gear,
boat, trailer, and equipment before leaving the water. Clean
your boat, tackle, downriggers, trailer, waders, etc. with hot
water (above 120ºF) when you get home
• DRAIN live wells, ballast and bilge water before you leave the
water body
• DRY boats and equipment to dry completely before launching in other waters
• DISPOSE of unused bait in the trash, not in the water

Ceropagis pengoi (Fishhook)

Images courtesy of Michigan Dept. of Environmental Quality

Daphnia lumholtzi

COLORADO PARKS &amp; WILDLIFE • 6060 Broadway, Denver, CO 80216 • (303) 297-7295 • cpw.state.co.us

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