The Toronto Salmon Run

Guest Post by Sara Bowman, currently enrolled in the Professional Masters of Environmental Science program at the University of Toronto-Scarborough

The Toronto Salmon Run

Toronto has been called a lot of things, but I think my favourite is “A City Within a Park”. Between High Park, the Rouge, and countless other parks based around our river systems, there are so many opportunities for people to connect with nature and forget they live in a city that is 2.6 million people strong. Despite my frequent excursions into the parks of Toronto, I still will often see something new that spurs a whole whack of questions and excitement about the area I call home.

Case in point: the salmon run! Cycling to work on October 13th I was lucky enough to witness my very first salmon run along the Don River, between Sheppard and Finch. You couldn’t help but notice the nearly 2 foot long fish struggling northward against the current, especially when a few individuals would have a violent encounter followed by swimming speedily away. I whipped out my cell phone and took as many videos and pictures as I could without being late to work. All throughout my shift questions started cycling through my head. Where in the river do the fish spawn? How many types of salmon are in Lake Ontario? Where did they come from? How are they faring from a conservation perspective? In no particular order, here are some answers I found to these questions!

Photo Credit: Tony Bock, The Toronto Star

First of all – I think my salmons were Chinook, which is the largest of the Pacific Salmons[1]. Chinook Salmon were intentionally introduced to Lake Ontario some time in the 1960s (Coho Salmon, another Pacific Salmon species, was introduced at around the same time), mainly for sport fishing, and as a bio-control for non-native fishes[1]. Their introduction was also important for essentially replacing the native Atlantic Salmon and Lake Trout, which were the top predators[1]. Atlantic Salmon were extirpated from Lake Ontario in the late 1800s due to fishing pressures, and today programs like Bring Back The Salmon are undertaking re-introduction efforts, and also habitat restoration and public outreach so that extirpation doesn’t just happen again[2].

Although thousands of individuals of Chinook are stocked in Lake Ontario every year, it is believed that natural reproduction occurs, and that they are well on their way to becoming naturalized[1]. In an ocean system, Chinook Salmon migrates up streams (the ones where they were born) from the Pacific Ocean to mate and lay eggs (spawn). Once they have spawned, they die, unlike the Atlantic Salmon which makes the trip back down to the Ocean after spawning[3]. The adult female will choose a site to make her “redd” (essentially a nest for the fish eggs) based on the water velocity and depth, and on the composition of the substrate, which should be gravel[3]. At first I was confused about how the fish managed to get so large in just a year, but it turns out that once they hatch after 3-5 months, they can spend up to 2 years in the streams where they undergo certain changes to prepare them for salt-water life[3]. Once they are back in the Pacific, they will stay there to feed and grow for up to six years[3]!

Lake Ontario is home to seven species of fish in the family Salmonidae, of which only 3 are native: the Atlantic Salmon, the Lake Trout, and the Brook Trout[1]. The Brown Trout, Chinook Salmon, Rainbow Trout, and Coho Salmon were all introduced[1].  My first thought, and this may be yours to, is how Atlantic Salmon could be considered native to Lake Ontario – after all “Atlantic” is in their name, and the distance between the Atlantic and Lake Ontario is pretty far, even for a determined migrating fish. So how did the fish get into our lakes? The Ice Age. The last one ended about 12,000 years ago, and Toronto was under about a kilometer or two of ice. When the glaciers retreated northward, basins were carved into the land and were filled with the melted water, and because of all the extra water from the ice, the St. Lawrence connection between the lake and the ocean was stronger[4]. Because the Atlantic Salmon had some freshwater adaptations for when it was spawning, it was able to naturalize to its new all freshwater environment[1].

National Oceanic and Atmospheric Association, 1999 

As the 2012 Fishes of Toronto report explains, as settlement around Lake Ontario and its streams increased in the 1800s and 1900s, the river temperatures increased, erosion increased, pollution from sewage increased, and physical structures blocking migration like dams were built. This would ultimately result in the local demise of the species from Lake Ontario.  Luckily, as I mentioned above, restoration efforts are under way to restore Atlantic Salmon populations. I wondered whether or not here might be some detrimental effects on any of the salmonid populations when or if Atlantic Salmon makes a come back, but a study in Ecology of Freshwater Fish from 2012 by Jessica Van Zwol and others found that a mix of Atlantic Salmon, Brown Trout and Rainbow Trout in stream breeding grounds did not significantly impact productivity[5]. Lake Trout is another native of Lake Ontario that suffered major population declines. In the 1970s some restoration efforts were began, but today the population has to be maintained by fish reared in a hatchery – the amount of natural reproduction occurring is not enough to prevent the species from extirpation[2].  

What can we do to ensure the future of these top open-water predators in Lake Ontario? For starters, we can be more conscious of what we are putting down our drains – it leads to the rivers and can pollute them. Be aware of proper chemical disposal. You can engage in tree planting programs along riverbanks to help prevent erosion. You can even help with salmon hatchery programs and habitat restoration to help give the populations a boost so that they can maintain their ecological roles, and be around for fishers to fish for generations to come.

Thanks for reading!!

References

1.Fishes of Toronto: A Guide to Their Remarkable World. City of Toronto, 2012. URL: 
https://www1.toronto.ca/City Of Toronto/Toronto Water/Files/pdf/F/Fishes of TO_PRINT_Feb23%5B1%5D.pdf
2. Lake Ontario Atlantic Salmon Restoration Program. Bring Back the Salmon Lake Ontario. 2013. URL:  http://www.bringbackthesalmon.ca/?page_id=12 
3. Chinook Salmon. NOAA Fisheries. Updated May 14, 2015. URL: http://www.nmfs.noaa.gov/pr/species/fish/chinook-salmon.html 
4. About Our Great Lakes: Background. National Oceanic and Atmospheric Administration. 
[U.S. Army Corps of Engineers and the Great Lakes Commission] Published 1999. URL: 
http://www.glerl.noaa.gov/pr/ourlakes/background.html 
5. Van Zwol, J., Neff, B., Wilson, C. 2012. The effect of competition among three salmonids on dominance and growth during the juvenile life stage. Ecology of Freshwater Fish. 21: 533-540. Accessed online: http://publish.uwo.ca/~bneff/papers/Van Zwol et al_Salmonid Dominance.pdf

Could today’s oil rigs be tomorrow’s biodiversity hotspots?

*Guest post by Bryan Flood -one of several posts selected from the graduate EES3001 Scientific Literacy course at University of Toronto-Scarborough.

New research by Jeremy Claisse and colleagues at Occidental College in Los Angles have discovered that secondary fish production at oil and gas platforms off the coast of California is up to an order of magnitude higher than other marine ecosystems. This includes reefs and estuaries, normally considered some of the most productive ecosystems on the planet.

Photo from: US Bureau of Ocean Energy Management - http://www.data.boem.gov/homepg/data_center/other/imagecate/imageview.asp?ID=292

The authors measured the total productivity at oil and gas platforms and divided by the platform’s footprint to get a per-square-metre productivity. Herein lies the secret: The authors attribute these phenomenal productivities to the large hardscape (physical surfaces of the rigs) to seafloor ratio.

Having a structure that spans the total water column creates a range of habitats for a diverse variety of species and life stages, as well as creating a complex structure with large surface area which translates directly into habitat. This habitat attracts many species including rockfish larvae, invertebrates and planktonic food resources. These form the base of the food web, subsequently attracting adult fish and other organisms.

These results have important implications for the future of the more than 7500 oil and gas platforms around the world that will need to be decommissioned at the end of their service life. Should they be dismantled, or left as artificial reefs? Should future platforms and wind turbines be designed with an afterlife as an artificial reef in mind? Could these structures one day dot the seas with aquatic metropolises?

Claisse, J., Pondella, D., Love, M., Zahn, L., Williams, C., Williams, J., & Bull, A. (2014). Oil platforms off California are among the most productive marine fish habitats globally Proceedings of the National Academy of Sciences, 111 (43), 15462-15467 DOI: 10.1073/pnas.1411477111

To Keep Invasive Asian Carp from the Great Lakes, Carp Catchers Get Creative

*Guest post by Noemie De Vuyst -one of several posts selected from the graduate EES3001 Scientific Literacy course at University of Toronto-Scarborough.

Some say fishing is a peaceful pursuit. Not so if you're one of the self-dubbed Carp-Hunters, a pair of Illinois fishing guides whose carp-catching antics have turned them into YouTube celebrities. Over the last three years, videos of their over-the-top methods have racked up hundreds of thousands of views.

They've netted carp while on water-skis, and speared them with samurai swords and costume Wolverine claws. In Illinois' rivers, the Asian carp are so abundant they practically jump into the outstretched nets themselves. In an ecosystem where the invasive species has largely displaced native fish, the Carp-Hunters’ new hobby has a higher purpose; “We care greatly about preserving out natural ecosystem”, their video’s intro reads. “Since we can’t bass fish anymore we have taken on this burden.”

Silver Carp in the Illinois River, 2009. Nerissa Michaels/Illinois River Biological Station, via Detroit Free Press. 

Kooky as their methods may be, the Carp-Hunters have something in common with government agencies on either side of the Great Lakes; they're both battling the highly invasive Asian carp.
Though the U.S. and Canadian officials may not be going after the invaders with the same flair – not everybody gets to name their fishing boat the “Carpocalypse” - they've been labouring to keep the fish out of the Great Lakes since escapees from fish farms were discovered in the 1990's. With their enormous appetites and extraordinary ability to reproduce at speed, Asian carp would be disastrous to ecosystems and economies if they ever reached the Great Lakes.

First brought to North America in the 1970's, Asian carp already dominate some US waterways. The town of Havana, Illinois, just 85km downstream of Carp-Hunters fishing grounds, is thought to have one of the highest abundances of Asian carp on Earth. Here, the carp make up 60% of the fish community.

The uphill battle to keep carp from the Great Lakes has popped up in the news recently. In early October, the routine testing of 200 sites found a single sample of silver carp environmental DNA (or eDNA) in the Kalamazoo River, a tributary to Lake Michigan.

What does it mean that this one sample tested positive? The presence of eDNA shows only that silver carp material was present at the site. What it can't tell us is whether the carp was alive, or how many fish there might have been. In fact, the presence of eDNA doesn't tell us that a silver carp was present at the site at all; it's possible that scales or tiny amounts of mucous were transported by boats or fishing equipment, or even in bird droppings. With no silver carp sightings in the Kalamazoo, it seems likely the positive result comes from one of these explanations.

Despite the low likelihood that silver carp had really spread to the Great Lakes, news of the positive eDNA result was quickly picked by many local news outlets. Within days, the US Fish and Wildlife Service sped through the collection and testing of 200 more samples, and appealed to anglers to report any carp sightings.

Why such a quick response for a finding with such high uncertainty? If Asian carp were to spread to the Great Lakes, it's feared they take over aquatic ecosystems and cause the fishing and angling industries millions of dollars of loss. Silver carp are especially worrisome, since they have a taste for the same microorganisms and algae that many native species rely on.

By late October, the results of Michigan's second batch of eDNA testing were announced; all samples were negative. For now, it seems the silver carp have crept no closer to the Great Lakes watershed. Canada and the US continue to monitor their waterways closely and to put in new measures to prevent the spread of the fish. This past July, Fisheries and Oceans Canada opened a new Asian Carp Science Lab. In a political climate that has squeezed environmental sciences from all sides, the funding of a new facility highlights the carps' immense potential to cause damage.

So even with their home-built contraptions, it looks like Illinois’ Carp-Catchers are doing their bit for the Great Lakes.


  
For more information on eDNA sampling at the Michigan Department of Natural Resources:
http://www.michigan.gov/dnr/0,4570,7-153--340230--rss,00.html
http://www.asiancarp.us/edna.htm

For details on the new Asian Carp Lab at Fisheries and Oceans Canada:
http://news.gc.ca/web/article-en.do?nid=865809

And to see those Carp-Hunters do their thing:

https://www.youtube.com/watch?v=hN2gMP3Q2Z4

Fisheries and food webs: a whole system approach to cod recovery

The collapse of cod fisheries around the world is a breathtaking example of over exploitation and poor planning. But with reduced fishing pressure why have cod populations shown such slow or stagnant population recovery? This has been an extremely active area of research for fisheries scientists. In a recent paper by Casini and colleagues in the Proceedings of the National Academy of Sciences, they found that over-fishing of cod in the Baltic Sea has led to a regime shift, where a small planktivorous fish called sprat now dominate the system. But its not just that there is a new dominant, sprat seem to really change how the ecosystem operates, to the detriment of cod recovery. When the ecosystem was cod dominated, zooplankton abundance was unrelated to sprat abundance but did appear to be dependent on hydrological environmental variables. In the new sprat-dominated system zooplankton numbers are negatively related to sprat abundance and the environmental controls of zooplankton abundance do not appear to be important. So why is this bad for cod recovery? Adult sprat compete with larval and juvenile cod for zooplankton and sprat consume cod eggs. The authors suggest that a good cod recovery plan will involve managing key aspects of the food web. This paper reveals how a whole food web or ecosystem approach is necessary for understanding population controls of important fisheries species.

M. Casini, J. Hjelm, J.-C. Molinero, J. Lovgren, M. Cardinale, V. Bartolino, A. Belgrano, G. Kornilovs (2009). Trophic cascades promote threshold-like shifts in pelagic marine ecosystems Proceedings of the National Academy of Sciences, 106 (1), 197-202 DOI: 10.1073/pnas.0806649105