Invasive Species

Kahshe Lake Sampling Program

The sampling undertaken by the Kahshe and Bass Lake Steward in 2017 and 2019 found no evidence of spiny water fleas, fish-hook water fleas, zebra mussel veligers, or freshwater jellyfish.

Background

Anyone who follows the local news outlets may have seen this March 22, 2018 news article and wondered if Kahshe Lake has been impacted by these ‘monsters.’

In 2017, the Federation of Ontario Cottagers’ Association (FOCA) notified lake associations that they were prepared to fund several pilot projects to begin a more comprehensive understanding of invasive species. The KBLA responded to this initiative with a proposed program for the sampling and determination of the presence of spiny waterfleas and zebra mussels. In preparing the proposal, it was determined that the Ontario Federation of Anglers and Hunters (OFAH) was offering a no-charge loan of dedicated sampling equipment and the analysis of water samples collected throughout Ontario for the two invasive species. Although the fishhook waterflea and freshwater jellyfish were not specifically addressed in the sampling program offered by the OFAH, the writer visually evaluated each of the samples collected for the presence of freshwater jellyfish. While this would not rule out smaller life stages such as eggs, frustule, or planula larvae or polyps of this species, it would certainly identify the presence of adult jellyfish and likely mature polyps or polyp colonies. In the case of the fishhook waterflea, the OFAH analysis of the water samples would have captured this species as well, as it is similar in size to the spiny waterflea.

With this as a basis, a proposal was prepared and was awarded funding by FOCA to cover a small number of related sampling costs and report printing. The terms of the FOCA award included the preparation of a final report and the completion of a FOCA project summary questionnaire with a minimum of five pictures documenting key pilot project activities and participating people by December 15, 2017. The questionnaire was completed on schedule and accepted by FOCA. This report constitutes the final component of the funded project.

In 2019, funding for several FOCA programs including the Invading Species Awareness Program was cut by the Provincial government; however, a group of concerned aquatic scientists from Muskoka and other parts of Ontario managed to coordinate a limited amount of invasive species sampling and the OFAH made sampling equipment it had available for sharing across Muskoka and other areas. As a result, we were able to conduct sampling of both Kahshe and Bass Lakes in 2019 and the KLRA provided funding for the laboratory identification of the collected samples. These findings have not yet been entered into the EDDMapS Ontario program, but this should take place at a later date.

What were we looking for?

Our aquatic studies have been focused on three invasive species that have been detected in other lakes in the Muskoka area, including Spiny waterflea, Zebra mussels, and freshwater jellyfish.

Results Summary: 2017 & 2019

While the laboratory did not report on the presence or absence of the fishhook waterflea, it is unlikely to have been present, as it is similar in size to the spiny waterflea.

The OFAH also did not specifically search for freshwater jellyfish; however, given their larger size, at a minimum, the mature hydromedusae would have been captured via both the horizontal and vertical haul methods employed in the study. As none were detected in any of the sampling sites, this particular life stage of the freshwater jellyfish does not appear to be present in Kahshe Lake.

The laboratory results for the 2019 sampling from both Kahshe and Bass Lakes also were found to be negative for zebra mussel veligers (larvae), spiny water fleas, and freshwater jellyfish. As both Kahshe Lake samples were adjacent to boat launching ramps, this provides a reasonable level of certainty that these organisms have not yet been introduced via the launching of contaminated boats or fishing gear from other lakes.

Spiny Waterflea

• Belongs to the class Crustacea, a group of animals such as crabs and shrimps that possess a hard exoskeleton (outer shell).
• Measure about 10mm in length, of which the tail spine comprises about 60%.
• Like all other Crustacea, its exoskeleton molts to grow. The spiny water flea is unique because it sheds only the exoskeleton that covers its body, retaining the exoskeleton that covers the tail spine.
• Tail spine is straight or slightly angled from the body, with 1-3 pairs of barbs, and a straight needle-like tip.
• Head has a single large, dark, compound eye; also present are a pair of jaws that are used to pierce and shred its prey.
• Has four pairs of legs; the first, longer pair is used for catching prey, whereas the other pairs of limbs are designed for grasping prey while they are being consumed.
• Voracious predators and can eat up to 20 organisms of zooplankton daily.
• Prefer large, deep, clear, oligotrophic lakes but will occur in slightly eutrophic waters like those of Kahshe Lake.

Tolerate water temperatures from 5-28oC and migrate vertically in the water column to deeper, cooler waters in the day and surface waters at night.

Pathway of Introduction and Spread

• Reported in Lake Ontario in 1982, and found in all of the Great Lakes by 1987.
• They now occur in over 100 inland lakes in Ontario.
• Believed to have been introduced to the Great Lakes via ballast water discharge of commercial shipping vessels.
• Primarily reproduce parthenogenically (a form of reproduction where an individual develops from an unfertilized egg); therefore, they can colonize quickly with a single female.
• Sexual reproduction produces resting eggs that overwinter and can remain dormant for long periods.

Impacts

Spiny waterflea consume up to three times as much as native species of zooplankton such as Daphnia, which is an important food source for juvenile fish species. As a result, the spiny water flea competes directly with these juvenile fish for food. When populations of this invader are high, consumption is significant, and the amount of food available to native species of predatory zooplankton, smaller forage fish, and juvenile fish is reduced.

Other zooplankton predators may be affected directly through competition for food or indirectly because of a shift in prey items available. Small fish have difficulty consuming spiny waterflea and larger fish that prey on the species may experience reduced growth rates because the waterflea spines are indigestible (accumulate in the stomach) and do not offer any nutritional value. Also, the species can attach to foul fishing lines, downrigger cables, and other equipment used for fishing.

Planktivorous fish such as whitefish and lake herring feed on spiny waterflea. However, studies have indicated that juvenile fish smaller than 10cm in length are unable to use the spiny waterflea as a source of food due to the long tail spine, which prevents them from swallowing it.

Fishhook Waterflea

• Predatory cladoceran that collects in transparent cotton-like masses on fishing lines.
• Total length of 10 mm, with the tail spine comprising about 80% of the total length.
• Tail spine is strongly angled (~90o) from the body, with 1-3 widely spaced pairs of barbs, and a unique loop or “hook” at the tip.
• Head has a single, dark, compound eye and the dorsal egg pouch is elongated and pointed.
• Found in open deep waters, preferring the upper, warmer water layer but able to tolerate a wide range of water temperatures from approximately 8-30oC.

Pathway of Introduction and Spread

• Recorded in Lake Ontario in 1998, the St. Lawrence River by 1999, and Lake Erie by 2001. To date, have not been reported in inland lakes or elsewhere in Canada. In the United States, occurs in Lake Michigan, Lake Erie, and the connected Detroit River, and several Finger Lakes in New York State.
• Introduced probably via ballast water discharge of a commercial shipping vessel, with Great Lakes populations derived from the Baltic Sea.
• Reproduce parthenogenically and therefore, can colonize quickly with a single female.
• Sexual reproduction produces resting eggs that overwinter and may be transported, along with adults, to inland lakes in bait buckets, live wells, mud, bilge water, or on fishing and other equipment.

Impacts

Predation by fishhook waterflea on small native zooplankton has likely led to the declines observed in several zooplankton species in Lake Ontario. The fishhook waterflea may compete with native planktivorous fish or other zooplankton predators for food. Because of its barbed tail, the species attaches to fishing gear and clogs nets and trawls, fouling equipment used for recreational and commercial fishing.

Summary of Impacts of Both Waterfleas

• Researchers believe that spiny waterfleas are the greatest threat to the biodiversity and structure of native zooplankton communities on the Canadian Shield since acid rain.
• Since their main diet is zooplankton, they reduce food supplies for small fish and young sport fish such as bass, walleye, and yellow perch.
• A few animals can quickly multiply into a large population.
• They are easily spread between waterbodies on angling equipment and bait buckets and in live wells and bilge waters.
• Spiny waterflea introductions result in an average 30 to 40 percent decline in native populations of zooplankton.

Zebra Mussels

• The zebra mussel (Dreissena polymorpha) is a 3-5cm long freshwater clam with a brown and cream-colored striped shell originally from Eurasia.
• A female zebra mussel can produce up to one million eggs each year, with reproduction beginning when water temperatures reach 12°C or higher. Upon hatching, free-floating microscopic larvae (called veligers), are dispersed by water currents, wind, and wave action.
• Two to three weeks later, the zebra mussel larvae begin to develop their shell and become too heavy to float in the water. They then settle and secrete sticky fibers which they use to attach to any hard surface. They continue to grow and are soon large enough to be seen by humans.
• Depending on conditions, zebra mussels can live between two to five years, and grow up to five centimeters in length.

Pathway of Introduction and Spread

• Discovered in North America in Lake St. Clair in 1988.
• Believed to have arrived in the ballast water of a ship traveling from a European port.
• Zebra mussels have spread quickly into all of the Great Lakes, the St. Lawrence River, connected waterways, and many inland lakes in southern Ontario.
• Zebra mussels are highly adaptable and can survive in lakes with a wide range of environmental conditions.
• Zebra mussels could spread throughout southern Ontario and regions of northern Ontario if prevention measures are not taken by recreational water users.

Impacts

The introduction of the zebra mussel has caused enormous changes to the Great Lakes basin ecosystem and has had major economic and social impacts. Mussels filter plankton out of the water, which depletes it as a food source for native species and also results in clearer water, thereby increasing sunlight penetration and promoting the presence of toxic algal growth and blooms. Large colonies can take over fish spawning areas and beaches, cutting the feet of potential swimmers. They also clog water intake lines because of their dense colonies.

Freshwater Jellyfish

The freshwater jellyfish is a hydrozoan which is most easily identified when it takes the form of a small, bell-shaped jellyfish, known as a hydromedusa.

Polyps overwinter by contracting into resting bodies called podocytes, which are essentially dormant cellular balls surrounded by a protective chitin-like membrane that allows them to withstand more extreme conditions than the active forms.  When conditions are favorable, the podocysts grow into polyps again.

Pathway of Introduction and Spread

• Freshwater jellyfish is an invasive species thought to have originated in China’s Yangtze River.
• Discovered in the U.S. in the Huron River near Ann Arbor, MI, in 1933, and in Lake Erie shortly thereafter.
• Been recorded in Lake Huron and Lake St. Clair, as well as dozens of inland lakes and streams throughout the region.
• In Canada, freshwater jellyfish have been documented in Quebec since 1955 and in Ontario since 1980.

Impacts

An evaluation of Kahshe Lake is important because recent media coverage has identified the lake as one of several lakes in Muskoka where freshwater jellyfish have been reported. The news report failed to mention that this was based on observations made back in 2005 and 2006, and not a recent finding.

The impact of this widespread jellyfish is unclear, but it is believed that its preference for predatory zooplankton, such as the rotifer Asplanchna, could influence relative zooplankton species structure.  Under laboratory conditions and in 4 mm of water, polyps are reported to have killed and fed on striped bass larvae.

Freshwater jellyfish are not considered dangerous to humans.  Although its stings can paralyze macroinvertebrates and small fish, its small nematocysts are not likely to penetrate human skin.

As such, the findings from the FOCA-funded testing of Kahshe Lake in 2017 have been entered into the EDDMapS program. An example of the EDDMapS for zebra mussel veligers and spiny water fleas in lakes in the Gravenhurst area for 2017 is presented below.

Jelly-Like Zooplankton in Kahshe Lake

As was first reported in 2021, there has been a noticeable increase in the population of Holopedium glacialis found in the waters of Kahshe Lake during certain periods. A summary of this species is provided below with more detailed information available in this report (Jellification of Zooplankton in Kahshe Lake Water).

• Holopedium glacialis is a type of water flea that is naturally found in inland lakes of Ontario.
• They float near the surface and are noticeable to swimmers in large populations.
• They are from 1.5 to 2.2 mm in size; however, because they are surrounded by a peasized gelatinous mantle comprised of one or more acid mucopolysaccharides, they are actually around 5mm in diameter.
• Increase in the population is related to gradual changes in the chemistry of lake water.
• No evidence in literature to indicate any negative impact on human health via dermal contact or limited oral exposure via recreational use of lake water.

Invasive Plants

Several invasive plant species pose serious problems in Ontario, mainly because of their propensity to spread quickly and out-compete native species for water and nutrients. The following link (Invading Plant Species) provides information on two species that are most prevalent around Kahshe and Bass Lakes: Invasive Phragmites and Japanese Knotweed.

What You Can Do

• If you have these or any invasive species on your property, get rid of it. Management options for control include mechanical excavation, flooding, herbicide application, and prescribed burning.
• Do not dispose of invasive plants in the compost pile – discard them in the regular garbage.  
• When hiking, prevent the spread of invasive plants and seeds by staying on trails and keeping pets on a leash.  
• If you find Invasive Phragmites, Japanese Knotweed, or other invasive species in the wild, contact the Invading Species Hotline at 1-800-563-7711, or report it online.