Author: berg.229

Background

Migratory fish are species that move to accommodate their reproductive, feeding and refuge needs. Many fish migrate during only a small period of their lifetime. For several fish, migration takes place annually on a seasonal basis. Fish can migrate between marine and fresh water (diadromous fish) or between different fresh waters (potamodromous fish).

In the Great Lakes region, migrations are potamodromous and take on several different patterns. Some species, including Lake Sturgeon, Walleye, and Coaster Brook Trout migrate longitudinally from lakes to tributaries to spawn. Others migrate from lakes to coastal wetlands to spawn, like the Northern Pike. There are also species, such as the Lake Trout, that migrate from pelagic areas to near shore and off-shore spawning reefs. Not all migrations cover long distances, migrations by Great Lakes species range from 10s of meters to upwards of 200km. The following table summarizes a subset of Great Lakes migratory fish and their coarse migratory behaviors:

Common Name	Scientific Name	Most Commonly-Referenced Migratory Behavior
American eel	Anguilla rostrata	Between lake and river
Atlantic Salmon	Salmo salar	Between lake and river
Bluegill	Lepomis macrochirus	Within river
Brook Trout	Salvelinus fontinalis	Within river
Channel Catfish	Ictalurus punctatus	Within river
Lake Herring	Coregonus artedi	Between lake and river / within lake
Lake Sturgeon	Acipenser fulvescens	Between lake and river
Lake Trout	Salvelinus namaycush	Between lake and river / within lake
Lake Whitefish	Coregonus clupeaformis	Between lake and river / within lake
Longnose Sucker	Catostomus catostomus	Between lake and river
Northern Pike	Esox lucius	Between lake and river
Shorthead Redhorse	Moxostoma macrolepidotum	Between lake and river
Walleye	Sander vitreus	Between lake and river
Source: Great Lakes Inform: An Information Management & Delivery System, https://greatlakesinform.org/knowledge-network/758

Role in Great Lakes

Migratory fish play important structural and functional role in the Great Lakes. They influence the Great Lakes through direct and indirect mechanisms as consumers, ecosystem engineers, modulators of biological and chemical processes, and transport vectors (Flecker et al 2010). For example, species moving from one area to another move nutrients and energy between and among lake and riverine habitats. When fish or unfertilized eggs decompose, those nutrients are then available to the local foodweb.

Threats to Migratory Fish

• Tributary connectivity. Barriers that restrict upstream movement, such as dams and road crossings, can limit migration. If fish are unable to migrate to an ideal spawning habitat, they may be forced to spawn in sub-optimal conditions that result in reduced egg survival.
• Habitat degradation. Poor land-use practices in surrounding watersheds and pollution from urban or industrial sources contaminates migratory fish habitat.
• Invasive species. Invasive species stress migratory fish through competition and associated shifts in food web dynamics. They can prey on native fish and potentially out-compete native fish for food sources, resulting in sub-optimal diet for native fish.

Conservation Efforts

Several agencies are working to combat threats to migratory fish. These efforts include restoring tributary connectivity by removing dams, improving road crossings, and constructing fish passageways around barriers. Efforts also include restoring habitat by returning forest cover to riparian zones, recovering key native migratory fish species by stocking hatchery-reared fish and restricting harvest, and stopping the spread and controlling established invasive species.

Tracking Migratory Fish in Lake Erie

Tracking migratory patterns of fish is important for conservation efforts. The Great Lakes Fishery Commission established the Great Lakes Acoustic Telemetry Observation System (GLATOS) in 2010, with the goal of understanding fish behavior in relation to Great Lakes ecology and to provide useful information to fish managers. Acoustic telemetry is used to track fish movement. An acoustic tag that transmits a unique signal is implanted in the target species, and an acoustic receiver is used to decode the signal (Figure 1). Some transmitters can incorporate biological and environmental information such as pressure (to determine depth), temperature, and acceleration (to determine swimming behavior). Lake Erie migratory fish projects shared on GLATOS include studies of Lake Sturgeon, Muskellunge, Walleye, Grass Carp, Lake Trout, Sea Lamprey.

Figure 1: Acoustic tag and receiver. Source: http://glatos.glos.us/projects.

Case Study: Assessing adult Muskellunge movement in Buffalo Harbor, Lake Erie, and the Niagara River

Recently, Justin Brewer from the New York State Department of Environmental Conservation and the Niagara Musky Association partnered with the Habitat Enhancement and Restoration Fund to determine migratory patterns of muskellunge in Buffalo Harbor, Lake Erie, and the Niagara River. Knowledge of the seasonal use of these areas will help fishery managers better understand the habitat requirements of Muskellunge and will be used to direct habitat restoration projects. They are using the GLATOS array to document Muskellunge movement. Electro-fishing techniques were used to secure 10 viable musky samples from the Niagara River and Buffalo Harbor, 5 males and 5 females. Acoustic tags were surgically implanted into the musky and 6 acoustic receivers were planted to track them. These receivers are few of many that are updated to the GLATOS database, so if a musky is picked up outside of their study region, it will be detected. This is an ongoing study that will answer important questions about prime Muskellunge spawning habitat, viability, and whether it can be expanded.

References

Great Lakes Inform: An Information Management & Delivery System. Migratory Fish. Available at https://greatlakesinform.org/knowledge-network/758 (Last accessed 29 October 2017).

Great Lakes Acoustic Telemetry Observation System. Available at http://glatos.glos.us/ (Last accessed 29 October 2017).

The Buffalo News. Why this musky study is an investment in the future. Available at http://buffalonews.com/2017/06/14/musky-study-investment-future/ (Last accessed 29 October 2017).

Flecker AS, McIntyre PB, Moore JW, et al (2010) Migratory Fishes as Material and Process Subsidies in Riverine Ecosystems. American Fisheries Society Symposium 73:559–592.

Background: We all know the story of the Asian carp invasion in the US. In the 1970s, fish farmers from Southern states in the US began importing Asian carp (Silver Carp and Bighead Carp) from China in an effort to control phytoplankton blooms in their aquaculture ponds and sewage treatment lagoons. Asian carp are filter feeders; they feed on small food items at the base of the food chain. Trouble began when fish escaped into the Mississippi River watershed after floods that breached the man-made lagoons in Arkansas. Asian carp can consume up to 20% of their body weight per day. They grow quickly and can decimate plankton populations, small floating organisms that form the foundation of the aquatic food chain and are an important food source to native fishes. Asian carp outcompete native fish populations and have quickly taken over the Mississippi watershed. Once they enter an ecosystem, they are extremely difficult to eradicate; Adult Asian carp have no predators in North America and females lay about half a million eggs each time they spawn. Asian carp continue to expand their range northward, threatening the Laurentian Great Lakes.

Asian Carp in the Great Lakes? Asian carp have not yet established sustainable populations in the Great Lakes. However, there have been several close calls.

• A Bighead Carp was caught 6 miles from Lake Michigan near Chicago below the first electric barrier.
• A Silver Carp was caught by the Asian Carp Regional Coordinating Committee (ACRCC) in the Des Plaines River in Illinois only 14 kilometers south of Lake Michigan.
• Environmental DNA (eDNA) evidence has been found in several locations on the Lake Michigan side of electric barriers. However, positive eDNA doesn’t necessarily indicate presence of live carp – the source could be from a dead fish, or transported through other sources such as bilge water from boats.
• Asian carp eggs, fry and fingerlings were found in the Wabash River in Indiana. If the Wabash River floods, there is potential for Asian carp to enter the Maumee River, which flows directly into Lake Erie.
• Between 1995-2000, three Bighead Carp were found in western Lake Erie. Follow-up surveys suggest that there is not a reproducing population in Lake Erie.

There is some speculation over whether Asian carp could have a stable population in the Great Lakes. Because Asian carp are filter feeders, they need algae and plankton to sustain larger populations. They may not be able to establish stable populations in deeper, colder lakes that are less productive, such as Lake Michigan or Lake Superior. If an invasion of Asian carp in the Great Lakes occurs, it will likely take several years for the population to become problematic, based on historical carp invasions and models of invasive species, and the size of the Great Lakes.

Preventing Asian Carp entry to the Great Lakes: Prevention efforts are ongoing to keep Asian carp from entering the Great Lakes. Current actions to block invasion to the Great Lakes focus on the Mississippi River Basin (MRB) and the Ohio River Basin (ORB). The shipping canal that connects the Mississippi River to Lake Michigan is the pathway of most concern in the MRB, and multiple barriers have been established there. In the ORB, agencies like the US Army Corps of Engineers and the US Fish and Wildlife are working together to identify potential pathways for carp to enter Lake Erie where future barriers could be most effective. Physical, electrical and behavioral barriers are being used in places were Mississippi River tributaries connect to the Great Lakes.

1. Physical Barriers: Dams and screens are common physical barriers to Asian carp. Dams across the Mississippi prevent Asian carp from swimming further upstream. However, most dams are not optimized to reduce carp passage. Lock and Dam #8 is the only dam on the river that has been adjusted to target carp. The Des Plaines River Bypass Barricade was built between the river and the Chicago Sanitary and Ship Canal to prevent Asian carp dispersal during a possible flooding event. Physical barriers are often used in combination with electrical and behavioral barriers.
2. Electrical Barriers: Electrical barriers send low-voltage, pulsing, direct current through underwater electrodes, creating an electrified field throughout the water column. They block fish by shocking them if they get to close because a portion of electrical energy applied to the water transfers to the fish. The electric current also inhibits a fish’s ability to maintain its position in the current. When fish encounter the current, they experience galvanotaxis. Galvanotaxis is a process that immobilizes muscles and physically stops fish from moving through the barrier. It can also lead to taxis, or forced swimming. This process sometimes causes trauma or is lethal, and may requires extra infrastructure to remove dead fish. Stronger electrical currents are required to effect small fish or juveniles, which may translate to young carp passing through this type of barrier. Several electrical barriers are in use within the Chicago Sanitary and Shipping Canal to block Asian carp from entering Lake Michigan.
3. Behavioral Barriers: Physical and electrical barriers are non-selective; there has been an increasing interest in barriers that use behavioral deterrents instead, such as sound, light and bubbles, because they have the potential to be species specific.

   

   Sound barriers were initially dismissed, but Asian Carp respond differently to sound than other fishes. The sensory mechanism in Asian carp are aggravated by complex noise, so they avoid it. Asian carp have Weberian ossicles that connect their swim bladder and inner ear. The ossicles provide carp with broad hearing and greater sensitivity than other Midwestern and Great Lakes. For example, Lake Sturgeon, Paddlefish, and Bluegill Sunfish detect sounds at much lower frequencies because they lack the connection that helps amplify sound. The use of higher frequency sound has the potential to modify carp behavior while minimizing the effect on native fish. Ambient light influences fish several aspects of fish behavior – orientation, location of food, communication between conspecifics, and avoidance of predators. Strobe lights introduce unnatural light levels that can impact fish behaviors and illicit an avoidance response. Strobe lights are not as effective in daytime or in highly turbid areas, and are suggested to be more effective when used in combination with other barriers. Bubble curtains are another type of behavioral barrier; they use a dense plume of noisy bubbles to repel fish. They also act as an unnatural visual cue for fish to avoid. Bubble curtains can be less efficient in locations with periodic high water events because they may be unable to maintain equal air pressure across differing depths. Behavioral deterrents don’t block fish 100% of the time because some fish are less sensitive or learn to ignore the barriers. Behavioral barriers are sometimes used in combination with other behavioral barriers and with physical or electrical barriers.

If Asian carp establish stable populations in the Great Lakes, it could cause declines in abundances of native fishes. Carp will compete with native fish for food and habitat. Several federally and/or state listed threatened and endangered fish rely on the Great Lakes and have been historically impacted by other Great Lakes invasives – the introduction of Asian carp could amplify those impacts and further harm these organisms.

Side Dish: The Scientific American recently published an article that encourages Americans to “carpe eat’um”. Because Asian carp are viewed negatively and are more difficult to prepare than other fish, people are not inclined to bite into a fillet o’ carp. Now, there is a movement to put Asian

carp on the menu, promoting the idea that if you can’t beat them, eat them. There is some concern over the commercializing carp. If a market develops demand for carp, people may not want to eradicate them, and may even want to spread them intentionally. However, other fish could be swapped for carp if they were eradicated, perhaps another invader could substitute for carp on the menu.

References:

National Wildlife Federation. Asian Carp Threat to the Great Lakes. Available at https://www.nwf.org/Wildlife/Threats-to-Wildlife/Invasive-Species/Asian-Carp.aspx (last accessed 21 September 2017).

Noatch MR, Suski CD (2012) Non-physical barriers to deter fish movements. Environmental Reviews 20:71–82. doi: 10.1139/a2012-001

Scientific American. Carpe Eat’um: Invasive Asian Carp Leap into Restaurants, Grocery Stores. Available at https://blogs.scientificamerican.com/guest-blog/carpe-eat-um-invasive-asian-carp-leap-into-restaurants-grocery-stores/ (last accessed 26 September 2017).

Scientific American. Great Lakes Defenders Have a Shocking Idea to Stave Off Invasive Carp. Available at https://www.scientificamerican.com/article/great-lakes-defenders-have-a-shocking-idea-to-stave-off-invasive-carp/ (last accessed 21 September 2017).

US Army Corps of Engineers. Going Green: Protecting our Great Lakes from the invasive Asian carp (2013). Available at http://www.usace.army.mil/Media/News-Archive/Story-Article-View/Article/478051/going-green-protecting-our-great-lakes-from-the-invasive-asian-carp/ (last accessed 26 September 2017).

Vetter BJ, Cupp AR, Fredricks KT, et al (2015) Acoustical deterrence of Silver Carp (Hypophthalmichthys molitrix). Biological Invasions 17:3383–3392. doi: 10.1007/s10530-015-0964-6

Zielinski DP, Sorensen PW (2015) Field test of a bubble curtain deterrent system for common carp. Fisheries Management and Ecology 22:181–184. doi: 10.1111/fme.12108