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: Adobe Creek Reservoir, Arkansas River (below
Pueblo Dam), Barr Lake, Bear Creek Reservoir, Boedecker Reservoir,
Boulder Reservoir, Boxelder Lake #3/Smith Lake, Boyd Lake,
Chatfield Reservoir, Cherry Creek Reservoir, Douglas Reservoir,
Holbrook Reservoir, Horsetooth Reservoir, Jackson Reservoir, John
Martin Reservoir, Jumbo Reservoir, Navajo Reservoir, North Sterling
Reservoir, Prewitt Reservoir, Prospect Lake, Pueblo Hatchery, Pueblo
Reservoir, Union Reservoir, Windsor Reservoir
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–30ºC (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
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
