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Fish
You can feel the difference between being outside on a brisk autumn morning or on a hot, sticky summer afternoon.
But even though outside temperatures are noticeably different, your interior body temperature tends to stay the same. That’s because humans are warm-blooded, or “endothermic,” creatures. Fish, meanwhile, are “ectothermic,” or cold-blooded.
Endothermic
(endo meaning “inside of,” or “within”; thermic meaning temperature)
These animals rely on their metabolisms to regulate their body temperatures. Food gets converted to energy, which helps the body maintain a near constant temperature. When the temperatures around an endothermic animal change, the animal will sweat, pant, shiver or use some other mechanism to try to maintain a stable temperature.
Ectothermic
(ecto meaning “outside of”)
These animals rely on the temperature of their environment to regulate their body temperatures. Many aquatic animals, like fish, are ectothermic. Because their internal temperature fluctuates with changes to their surrounding water temperature, many fish are potentially very vulnerable to climate change effects.
Ecosystems can be very sensitive to changes felt by different species, since organisms are linked together in food chains (which trace the path of that energy and nutrients may take as they move through an ecosystem). All of the interconnected and overlapping food chains in an ecosystem make up a “food web.”
There is a growing body of research that addresses how fish in Lake Huron will fare as temperatures rise. Much of this is focused on whitefish, a cold-water species that is commercially fished and is a staple food for the Anishinaabe.
Bruce Power, through the Nuclear Innovation Institute, has supported several of these research programs, including the Aquatic Biota program and the Environmental DNA (eDNA) program.
LAKE HURON FOOD WEB
INVASIVE PREDATOR
(Petromyzon marinus)
An aggressive, non-native parasite that fastens onto its prey and rasps out a hole with its rough tongue.
PISCIVORES (fish eaters)
(Oncorhynchus tshawytscha)
Pacific salmon species stocked as a trophy fish and to control alewife.
(Salvelinus namaycush)
Nearly eliminated by sea lampreys during the 1950s and 1960s. Stocking and lamprey control are resulting in its resurgence.
Photo credit: Great Lakes Fishery Commission
(Oncorhynchus mykiss)
A lake strain of non-native rainbow trout, rarely found deeper than 35 feet. Supplemented by stocking.
(Stizostedion vitreum)
Carnivorous night feeders, eating fishes such as yellow perch and freshwater drum, insects, crayfish, snails, and mudpuppies.
(Salmo trutta)
A European species introduced in the late 1880’s. Mostly does well in slightly degraded habitats.
(Lota lota)
Elongated, cylindrical, freshwater codfish.
FORAGE FISH
(Coregonus clupeaformis)
Native found in cold waters. Bottom feeder—diets have shifted to include zebra and quagga mussels.
Photo credit: Alavire
(Coregonus artedii)
A schooling fish, that prefer deep water, but move to shallower water in fall as upper waters cool. They are primarily plankton feeders, but also eat insects and small minnows.
(Perca flavescens)
Native that schools near shore, usually at depths less than 30 feet.
(Notropis atherinoides)
Numbers declined during the 1960s due to Alewife populations, but recent surveys show their resurgence.
Photo credit: Alavire
(Coregonus hoyi)
Native deepwater chub feeding on zooplankton and other organisms near the lake bottom. Harvested commercially for smoked fish.
(Osmerus mordax)
Found in both coastal and offshore habitats. Light-sensitive, so prefer deeper, cooler waters during the warmer seasons.
Photo credit: Alavire
(Myoxocephalus quadricornis thompsonii)
A native glacial relic that lives at the bottom of cold, deep water feeding on aquatic invertebrates.
(Lota lota)
Elongated, cylindrical, freshwater codfish.
MACROINVERTEBRATES
Larval insects and worms that live on the lake bottom. Feed on detritus. Species present are a good indicator of water quality.
Photo credit: Stephen Moore
(Hexagenia spp.)
A burrowing insect larvae found in warm, shallow water bays and basins, usually in soft sediments. The presence of this sensitive organism indicates good water quality conditions.
(Diporeia)
The most common species of amphipod found in fish diets that began declining in the late 1990’s.
Photo credit: Michal Manas
A mixture of native and non-native species of snails and clams are eaten by lake whitefish and other bottom feeding fish.
(Mysis relicta)
An omnivore that feeds on algae and small cladocerans. Migrates into the water column at night.
(Dreissena polymorpha and Dreissena bugensis)
Established in Lake Huron in 1990 (zebra); 1997 (quagga). Filter-feeders that remove huge quantities of plankton.
ZOOPLANKTON
(microscopic animals found in the water column)
(Bythotrephes longimanus) Visual raptorial predator that can depress native waterflea populations.
Photo: Invasive Species Centre
(e.g., Diaptomus spp.). Omnivores that feed on both phytoplankton and microzooplankton.
Photo credit: Uwe Kils
(Oncorhynchus mykiss)
A lake strain of non-native rainbow trout, rarely found deeper than 35 feet. Supplemented by stocking.
(e.g., Cyclops bicuspidatus)
Carnivorous copepods that feed on rotifers and other microzooplankton.
Photo credit: David Reed
(Leptodora kindtii)
Slow moving and patchy distribution of small swarms at relatively low numbers.
Photo credit: National Oceanic Atmospheric Administration
A diverse group of microzooplankton that, depending on species, feed on phytoplankton, detritus, or other microzooplankton.
Photo credit: Britannica
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PHYTOPLANKTON
(algae found in the water column)
(aka Cyanobacteria)
Often inedible and frequently toxic; blooms in late summer and can look like spilled paint on the water surface.
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Cold-loving microscopic (single celled) plants encased in silica shells that support the first wave of production in the spring.
Microscopic (single-celled) plants that form the main support of the summer food web. Also includes large nuisance species such as Cladophora.
Motile, single-celled plants or animals frequently found in high numbers. Most eat bacteria and so may help funnel bacterial products back into the food chain.
Aquatic Biota program
The Aquatic Biota program is focused on:
Lake
whitefish
Round whitefish
Yellow perch
Researchers have investigated the genetic population structure of these fish, examined potential reasons that the fish might die while in the embryo stage, and looked at how various temperatures changes experienced during the embryonic stage might affect the survival and fitness of the fish at later times. [19]
Lake whitefish embryos were incubated at 0, 2, or 5 °C until they hatched, and were then acclimated to 14-16 °C. The different incubation temperatures did not strongly affect the genetic makeup of the fish. After about 19 months, the whitefish were exposed to heat shocks of +6 °C. Certain characteristics of the fish were affected by the heat shocks, including stress response, cell signaling, and protein processing in part of the cells.
In 2021, lake whitefish reared at 2 or 5 °C and then acclimated at 15 or 19 °C were tested for swim performance. The study found that the fish reared at colder temperatures were better swimmers: they were able to maintain a faster overall swim speed, and had a higher capacity for increasing their aerobic metabolic rates.
Researchers also compared the responses of round whitefish and lake whitefish to changes in incubation temperatures. They found that round whitefish are more thermally sensitive than lake whitefish. They also found that the temperature that a fish embryo experiences can influence the preferred temperature of a mature fish up to a year post-hatching. Round whitefish preferred a colder temperature than lake whitefish.
Environmental DNA
(eDNA)
[13]
There are plenty of fish in the sea (or lake!)—so how do you track them all?
Lake Huron has a volume of at least 3,500 cubic kilometres of water, making it the third largest lake in North America, after Lakes Superior and Michigan. How do scientists track fish populations in such an enormous volume, particularly when those fish like to swim around in deep or murky water? Many methods rely on underwater photo or video surveys, or physically capturing and examining fish.
One powerful method that has emerged in the past decade is known as environmental DNA (eDNA) assessment. [21] Fish shed mucous, feces, urine, gametes and skin cells into the water. By examining these materials, researchers can determine the relative abundances of different types of fish and invasive species and monitor changes to biodiversity over time.
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Many power stations, including hydroelectric dams and nuclear power plants, rely on passing water through a system. The Bruce Power plant, for example, draws in water from Lake Huron to act as a coolant for the condensers that are used to recycle the steam warmed by the fission reactors.
The water passed through the system only once, and screens are placed around the pump to help prevent fish from getting pulled in. However, small organisms and eDNA can pass through these screens.
As part of the eDNA program, researchers looked at the effectiveness of a contemporary technique called DNA metabarcoding, which allows many species to be identified from a single sample.
They found that this technique was effective at identifying species such as lake whitefish and ciscoes, which are important to local fisheries, as well as deepwater sculpin and round whitefish, which are rare species of special interest. An automated eDNA sampler has been deployed in the source water of the power plant, which will enable researchers to compare eDNA concentrations outside and within the plant.
Sounds fishy!
Small populations of fish can be tracked directly, allowing scientists to better understand their movement patterns, spawning locations and other behaviours.
The fish are caught, a tag is attached, and the fish are released back into the wild. The tags act as transmitters by broadcasting a series of sound pulses into the water. These pulses, which carry a unique identifier for each tag, are picked up by a network of receivers placed at the bottom of the lake.
If the signal is picked up by three or more receivers, the exact location of the fish can be pinpointed, allowing researchers to track the fish as it swims.
This is the method used by GLATOS, the Great Lakes Acoustic Telemetry Observation System. Established in 2010 by the Great Lakes Fishery Commission, GLATOS helps connect acoustic telemetry researchers (which include Canadian, US, and Indigenous fishery scientists and biologists) with the equipment and databases they need to complete their research projects.
Source: https://glatos.glos.us/map
The Ciscoes of Lake Huron
“You ask any kid in the community here… They don’t know what a chub is… The chub have been gone for so long that people don’t talk about them anymore. They don’t remember them anymore.”
– Elder and past fish harvester, Saugeen Ojibway Nation [22]
Commercial chub fishing used to be an important part of life for the Saugeen Ojibway Nation. But in the past several decades, commercially viable chub have become scarce in Lake Huron.
Chubs are a flock of six deep-water fish in the genus Coregonus, including shortjaw cisco, bloater, deep-water cisco, kiyi, and longjaw cisco. Together with lake herring, these fish are commonly referred to as ciscoes. Chub and ciscoes are planktivores, meaning they feed on small organisms called plankton. They are also a critical prey fish for other important species such as the lake trout.
Coregonus species
NPS.gov
Lake Chub
2.dnr.cornell.edu
NPS.gov
Shortjaw
Cisco
oswegocountytoday.com
NPS.gov
Deep-water Cisco
NPS.gov
Bloater
canr.msu.edu
NPS.gov
Kiyi
oswegocountytoday.com
glaquarium.org
Researcher Alexander T. Duncan performed an investigation into the local and traditional ecological knowledge of the SON regarding the status of ciscoes in Lake Huron.
“Fish harvesters are often the first to observe declines and depletion in a given species due to their time spent on the waters and their dependence on the resource,” Duncan says. [23]
For the past 300 years, ciscoes and other deep-water fish in Lake Huron have been impacted by a number of setbacks that have made it difficult to study and manage these fish. Factors include overharvesting, a collapse of the deep-water fish community, introductions of invasive species such as sea lamprey, alewife, and dreissenid mussels, and the introduction of stocked predatory salmonids.
To help fill in the knowledge gaps on these fish populations, Duncan interviewed and collected stories and data from 16 past and present fish harvesters (11 band members from Nawash, and five from Saugeen).
This Indigenous ecological knowledge (IEK) was then used to sample lake herring and chub from October to December 2019, measuring sizes and taking DNA samples. The size of the chub were small in comparison to previous harvests, according to the participants. Lake herring populations, meanwhile, appear to be in a healthy state in the waters around the Saugeen Peninsula. Lake herring is a traditional food fish, but is significantly less marketable than other species.
Collecting, understanding, and valuing Indigenous ecological knowledge has the potential to inform fisheries governance going forward, says Duncan:
"Taking observations and insights of fish harvesters seriously could play a major role in the future of the resource and how it is monitored...
"Conversely, ignoring this knowledge or disregarding it for its anecdotal nature could prove fatal for the resource as exemplified by the collapse of the Atlantic cod fishery (Neis 1992; Bavington 2010). The latter example more closely aligns with what happened with the chub, a decline that occurred while SON fish harvesters were vocal and in objection to the stocking of predatory salmonids.
"Again, this ignorance of SON fish harvester observations and IEK is occurring with lake whitefish, which continue to decline."
Monitoring the conditions of nearshore habitats, wildlife, and the lake
Spotlight:
Saugeen Ojibway Nation Coastal Waters Monitoring Program
Run by the Saugeen Ojibway Nation (SON) Environment Office, the Coastal Waters Monitoring Program (CWMP) aims to build an extensive baseline inventory of the Saugeen Ojibway Nation territory habitats and wildlife.
The CWMP monitors the conditions of nearshore habitats, wildlife, and the lake, including measurements of water quality, water temperature, larval fish communities, vegetation and aquatic invertebrates. The data will help the CWMP understand variability and fluctuations in the conditions of nearshore fish communities and coastal vegetation communities, and how they relate to water quality and other environmental conditions over time.
SON’s Anishnaabe ways of knowing and understanding the environment, described as Traditional Ecological and Cultural Knowledge, is integral to the CWMP. This rich information is anchored by “place” (SON Territory), passed on through generations and across families, and is action-based, where learning and understanding is accomplished through doing.
In 2022, the CWMP examined sites for species diversity, total fish abundance, and round goby (an invasive species) abundance.
Invasive species
Biodiversity is like life's grand symphony: each species of animal, plant, and microorganism plays a unique note that contributes to an overall harmony in the ecosystem.
Much like a jarring, discordant note throws off a composition, the introduction of an invasive species disrupts the interplay of organisms in an ecosystem, leading to imbalances that can cause a loss of diversity.
Not all non-native species are considered invasive. An invasive species is one that causes harm through negative impacts on the environment (for example, by competing with native species for resources, like food, water, and territory), the economy, or society in general.
According to the ELPC, how climate change will ultimately impact biodiversity in the Great Lakes will depend on four factors [24]
How are new, non-native species introduced into the Great Lakes?
They can cross oceans by stowing away in the ballast water (held in tanks on ships to provide stability and maneuverability) on shipping vessels. Once in the Great Lakes, species can spread within the lakes and between them as they hitchhike on boats, trailers, and other gear used by commercial and recreational lake goers.
As the climate changes, flora and fauna respond by trying to stay within their preferred environmental conditions. Known as “range shift,” this phenomenon is one of the prime ways that invasive species are introduced. Different species respond to these environmental changes at different rates, and to various degrees, which can disrupt interactions between species. [25]
According to the Status of the Great Lakes 2022 report, the establishment of aquatic non-native species has slowed over the past 10 years in comparison to the 20 years prior. From 2011 to 2020, four new non-native species were established in the Great Lakes. All were species of zooplankton – tiny animals that drift along with currents rather than swimming on their own.
Photo Credit:
Elizabeth Whitmore And Joseph Connolly, Cornell University
Current key invasive species in the region
Sea lamprey
A long, slimy, eel-like creature snakes its way towards an unsuspecting fish. It lashes out, mouth open to reveal concentric rows of needle-sharp teeth surrounding a serrated blade of a tongue. The creature sinks its teeth into the side of the fish, latching on with the suctioning power of 10 vacuum cleaners. Its tongue rasps through scales and flesh, secreting an enzyme that prevents blood from clotting. Then the creature settles in to feast on the fish’s blood and fluids.
It sounds like something straight from a cult classic horror film. But, although they’ve earned the nickname “vampire fish,” sea lamprey aren’t fictional. They’re a real problem for the Great Lakes ecosystem.
Invasive species at
a GLANSIS
The Great Lakes Aquatic Nonindigenous Species Information System (GLANSIS) provides a comprehensive set of tools including species profiles, a mapping tool, risk assessments, a custom-generated list of invaders, an educator hub, and more. The site relies on professionally verified data and is focused entirely on the sensitive Great Lakes region.
On a national level, the Invasive Species Centre provides a range of resources to help manage invasive species in Canada. A hub for collaboration and knowledge sharing, the Invasive Species Centre connects stakeholders with the knowledge and technology they need to prevent the introduction and combat the spread of high-risk invasive species.
Spiny Water Flea
Photo Credit:.adkwatershed.org
Brittle waternymph
Photo Credit: biolib.cz
Fishhook waterflea
Photo Credit: cfb.unh.edu
Curly-leaf Pondweed
Photo Credit: Valerie Dillion
Nestled in the heart of Southampton, Fairy Lake offers a tranquil respite for residents and tourists alike.
Spotlight
on Fairy Lake
Encircling the lake is a one-kilometre-long nature trail adorned with sculptures carved into tree stumps. A diverse community of fauna call the lake home, including several species of frogs, turtles, fish, ducks and more.
In 2021, researchers began a multi-year study to assess the health of the lake, followed by an ecological restoration project based on the results of the study. The initiative, administered by Environment@NII and funded by Bruce Power, is a collaboration between the Town of Saugeen Shores, the University of Waterloo, the Invasive Phragmites Control Centre, and the Historic Saugeen Métis.