fisheries

Asian grass carp pose ecological threat to Great Lakes: �Թϱ�� scientist part of Canadian-American research team

ullahnor — Fri, 27 Jan 2017 20:10:56 +0000

Asian grass carp pose ecological threat to Great Lakes: �Թϱ�� scientist part of Canadian-American research team

ullahnor Fri, 01/27/2017 - 15:10

Cutline

�Թϱ�� biologist Nick Mandrak says that while not all invasive species have a high ecological impact, grass carp are voracious eaters, capable of consuming 40 per cent of their body weight per day (photo by Ken Jones)

Don Campbell

Author legacy

Don Campbell

Topic

Breaking Research

fisheries

Great Lakes

Carp

�Թϱ�� Scarborough

ecology

Asian grass carp pose a significant ecological threat to the Great Lakes and that threat could be extreme over the next 50 years.

This is the major finding of a large binational risk assessment authored by a team of American and Canadian researchers, including Nick Mandrak, associate professor of biological sciences at �Թϱ�� Scarborough.

“We don’t want grass carp in the Great Lakes, and we need to act now in order to eradicate the population in the Sandusky River,” says Mandrak, referring to the grass carp population already spawning in the Sandusky River in Ohio, which is connected to Lake Erie.

The peer-reviewed study, led by Fisheries and Oceans Canada and coordinated by the Great Lakes Fishery Commission, has researchers from Fisheries and Oceans Canada, �Թϱ��, the U.S. Geological Survey and the U.S. Fish and Wildlife Service.

Mandrak himself has conducted risk assessments on silver and big head carp in the past and also authored the first Canadian risk assessment of Asian carp in 2004 when he worked at Fisheries and Oceans Canada.

He says while not all invasive species have a high ecological impact, grass carp are different. For one, they’re voracious eaters, capable of consuming 40 per cent of their body weight per day. As a result, they can grow quite large, up to 30 cm long in their first year of life, meaning they have no natural predators in the Great Lakes. They also produce a lot of eggs, which means even in the short period of time when they can be eaten by larger fish, there are often too many to make a dent in their numbers.

And if you think a cold Canadian climate will deter them, think again. Mandrak has done field research on grass carp living in Siberian lakes covered by more than a metre of ice.

A joint American and Canadian report co-authored by �Թϱ�� Scarborough Associate Professor Nick Mandrak finds that grass carp pose a significant threat to the Great Lakes. (Photo courtesy of the Asian Carp Regional Coordinating Committee)

Grass carp were first introduced to North America from Asia as bio-control agents in the 1960s. They were brought in specifically to control aquatic vegetation like weeds growing in aquaculture ponds mostly used by the channel catfish industry.

“Unfortunately, they escaped from those controlled environments into the wild either by floods or through being released on purpose,” says Mandrak.

Since then, they’ve migrated up the Mississippi River into the Great Lakes region where they are reproducing in the Sandusky River. Grass carp have already been found in Lakes Michigan, Erie and Ontario.

The concern is that since fish don’t obey borders, there’s nothing preventing them from entering Canadian waters. Once there, Mandrak says grass carps could severely decimate wetlands, which are important spawning habitats for native fish.

“We need to be concerned because we share the Great Lakes, and the economic impacts would be significant especially when you look at commercial fishing and tourism,” he says.

Mandrak points to one aquatic system in South Africa where 13 of the 14 aquatic species of vegetation were destroyed within two years of grass carp being introduced.

He adds we’re at the point early in the invasion curve where grass carp populations can be eradicated if rapid response is taken. If not, we could end up with scenarios from the past like sea lampreys and zebra mussels, two species that upended the ecology of the Great Lakes.

“This study organizes a lot of the information we know about grass carp and the risk they pose to the Great Lakes,” Mandrak says. “Now we need to figure out what next steps can be taken to manage the problem.”

What brought sea louse epidemic to BC salmon? �Թϱ�� researchers explain

lanthierj — Wed, 20 Jul 2016 14:39:04 +0000

What brought sea louse epidemic to BC salmon? �Թϱ�� researchers explain

lanthierj Wed, 07/20/2016 - 10:39

Cutline

Salmon swarm about a diver inspecting a pen on a fish farm in British Columbia (photo by Natalie B. Fobes/National Geographic/Getty Images)

Peter McMahon

Author legacy

Peter McMahon

Topic

Global Lens

Faculty of Arts & Science

Research & Innovation

fisheries

salmon

Environment

Subheadline

“This is a lesson about the importance of better coordinating and timing regional treatment and being aware of warming ocean temperatures"

High ocean temperatures and poor timing of parasite management likely led to an epidemic of sea lice in 2015 throughout salmon farms in British Columbia's Queen Charlotte Strait, a University of Toronto-led study has found.

The sea lice spread to migrating juvenile wild salmon, resulting in the highest numbers of sea lice observed on wild salmon in a decade.

In spring of 2015, a team of �Թϱ�� ecologists led by postdoctoral researchers Andrew Bateman and Stephanie Peacock found that more than 70 per cent of fish the team sampled in the Strait's Broughton Archipelago had at least one sea louse: the highest prevalence of such parasites since 2005.

“It was sort of a perfect storm of environmental conditions and mismanagement of treatment,” says Peacock, a postdoctoral fellow in the �Թϱ��’s department of ecology and evolutionary biology when the research was conducted.

“A lot of people talk about how sea lice are natural, but in farms, you have these parasites in larger numbers. Juvenile wild salmon are then exposed as they migrate past these areas.”

Because farmed salmon are in open net pens and share water with nearby wild salmon, the parasites can transmit to young wild salmon who wouldn't normally encounter sea lice until later in life. These young fish are sometimes as small as three centimetres in length, while sea lice themselves can be close to one centimetre in diameter.

“Getting sea lice at such an early age affects young salmons' health and their ability to fend off predators,” says Peacock.

(Image below: juvenile chum salmon infested with sea louse parasites/ photo by Stephanie Peacock)

Based on the numbers of lice on juvenile salmon in 2015, researchers predicted an additional 9 - 39 per cent decline in returning pink salmon due to the outbreak.

Explaining an epidemic

In order to determine the cause of this outbreak, the team assessed the evidence for four contributing factors:

influx of lice on returning adult pink salmon
sea surface temperature
the timing of chemical treatments to control sea lice on salmon farms
resistance of sea lice to chemical treatment on farms

“Even though parasite treatments on farms were effective, we saw that treatments failed to protect wild salmon, and this happened at a time of unexpected warming in ocean water in these regions,” says Martin Krkosek, assistant professor in �Թϱ��’s department of ecology and evolutionary biology. Krkosek was Bateman’s and Peacock's supervisor and study co-author.

The fall of 2014 did have a healthy return of adult pink salmon, bringing sea lice into near-shore waters where they could infect farmed salmon. High ocean temperatures during winter months then likely accelerated sea-louse development, enabling populations to grow quickly and reach higher numbers than they would under normal ocean temperatures.

Also in 2015, individual salmon farms did not coordinate anti-louse treatments, with some farms delaying treatment until just prior to the time when juvenile salmon migrate past farms. As a result, sea lice from those farms could have spread to adjacent farms, hampering area-wide control of the outbreak.

“Furthermore, during the juvenile wild salmon migration, farms are supposed to treat for sea lice within 15 days of when a threshold number of lice are found on adult farmed salmon,” says Peacock. “But in 2015, some farms waited several months before they treated.”

“The strategy might have been 'wait until the migration to treat' but it kind of backfired because the louse populations were allowed to grow in the meantime, and the lice spread to other nearby farms. It likely created a bigger problem down the road.”

Preventing the next outbreak

“We were surprised to see that some farms don’t seem to be following their license conditions,” says Peacock. “We thought maybe there were more infractions in 2015 that may have led to higher numbers of sea lice, but when we looked back over 10 -15 years, the rate of such infractions was about the same. The big difference in 2015 really seems to be the combination of a lack of proactive parasite treatment and higher water temperatures.”

The team suggested the solution to such an outbreak in the future would likely be an earlier, coordinated parasite treatment effort between salmon farms – something the researchers say is lacking in this area and across the country.

“Sea lice used to be a problem a decade or so ago, then parasite management changed and it seemed like the problem had been effectively managed for several years. Then it wasn't managed well all of a sudden,” says Krkosek. “This is a lesson about the importance of better coordinating and timing regional treatment and being aware of warming ocean temperatures."

The results of the team's study appear in a paper published in the July edition of the Canadian Journal of Fisheries and Aquatic Sciences.

(Photo above by Stephanie Peacock)

fisheries

Asian grass carp pose ecological threat to Great Lakes: �Թϱ��� scientist part of Canadian-American research team

What brought sea louse epidemic to BC salmon? �Թϱ��� researchers explain

Explaining an epidemic

Preventing the next outbreak

Asian grass carp pose ecological threat to Great Lakes: �Թϱ�� scientist part of Canadian-American research team

What brought sea louse epidemic to BC salmon? �Թϱ�� researchers explain