Invasive Species

This week is National Invasive Species Week, so I figured a good blog topic this week would be invasive species.  Invasive species regularly crop up in my conversations with fishers and other members of the public but people often don't realize that invasive species or more correctly invasive alien species has a very specific definition.  A good understanding of what is and what isn't a invasive species and some of the principles associated with invasive species is essential for understanding and addressing this important issue.  As an aside I am reminded of the time when I was a student and presented about sea lamprey as a pest that needed to be eradicated from the great lakes to group that included Portuguese fishery biologists.  In the Great Lakes sea lamprey are an invasive species and millions are spent trying to eliminate them but in Portugal sea lamprey are native and considerable efforts are being made to save that species.  Needless to say the questions were spirited until the context of sea lamprey as an invasive species was better communicated (ahh the mistakes we make when we are learning). 

Invasive Asian giant hornet, AKA the murder hornet, is an example of one of the more highly publicized invasive species.  I included it here because who isn't freaked out about a two inch (5cm) pissed off stinging insect with the nickname murder hornet.  Image taken from May 3,2020 CTV News article "Invasive 'murder hornets' have been spotted in the U.S." - Jean-Francois Monier/AFP/Getty.

Invasive Species - Some Basics

So what is an invasive species?  Different sources word their definition differently but all definitions have the following in common. 

1. The species; regardless if it is an animal, plant, fungus, protist, bacteria or virus; is one that does not naturally occur in the given area or region.  
2. The species was introduced into this new area by human activity.  Species introduced from natural processes such as range expansion are usually not considered invasive species.  
3. The species has a negative impact upon on the environment and/or upon the economy.   Species that are introduced have to have a noticeably impact on native species, on the environment, or on something important to humans in order to be considered a nuisance and an invasive.  This impact can be very costly.  In the great lakes millions of dollars are spent each year combating invasive sea lamprey. Environment Canada estimates that the estimated annual cumulative lost revenue caused by just 16 invasive species is between $13 to $35 billion and that invasive species that damage the agricultural and forestry industries results in an estimated $7.5 billion of lost revenue annually. Impacts are not just economic.  When green crab invaded Antigonish Harbour in NS, eelgrass in the estuary declined by over 95% resulting in a 50% decline in Canada geese and common goldeneye.  Many invertebrate species that grow on the eelgrass beds and that are crucial prey for many other species in the food web were also thought to have significantly declined.
4. The species reproduces at a quick rate. Species that reproduce slowly are usually easier to control and often don't have the same degree of impact on native species.

More than a few invasive species biologists have pointed that by most definitions humans are the ultimate invasive species. Wit aside, species that aren't from a given area but don't meet the other criterion are usually referred to as exotic, non-native, introduced species. While not considered invasive they can still cause issues.  For example Striped Bass which are having a significant negative impact on salmon and trout populations are not actually an invasive because they are a naturally occurring species. Much of the confusion around muddling the waters around recovery efforts often blurs the lines between invasive and non-invasive species. 

When talking about invasive species invasive species biologists generally adhere to a few core principles that have been proven to be true.  Some of these princples are:

• early detection is key.  The sooner an invasive species is detected the early its impacts can be addressed.  The longer it goes undetected the larger and more spread out the population becomes.  Bigger, more spread out populations are much more challenging to address than smaller contained populations.
• early intervention is important.  The sooner an invasive species population is dealt with the sooner it can be eradicated, neutralized, or contained.  Waiter longer allows the population to grow and spread out confounding efforts to mitigate its impact.  An unfortunate reality is that detection and responses often take time and can be confounded by political and bureaucratic processes that further delay the response.  Too often this allows the invasive species population to establish (gain a firm foothold) making it nearly impossible to contain.  Smallmouth Bass and Chain Pickerel in southern NS and sea lamprey in the great lakes (sorry it was were I cut my teeth on invasive species) are examples of where invasive populations were allowed to establish.  These populations are now never going to be eradicated resulting in lasting and ongoing economic and environmental damage.
• impacts from invasive can be more complicated and more far reaching than first considered. When Sea lamprey were first introduced into the Great Lakes the impact on Lake Trout, then the top predator in the Great Lakes, was profound.  The annual harvest fell from thousands to tens of tonnes of fish.  Initially it was thought that was the only species affected, but as it turned out the impact that lamprey had on lake trout, effectively displacing it as the top predator,  changed the whole food web structure.  Once abundant bait fish were wiped out as species that were once controlled by Lake Trout became more abundant changing the structure of the prey populations below them.  These type of regime shifts are not uncommon when dealing with invasive species.
• once established invasive species populations will spread.  Because of their higher reproductive rates and ability to out compete native species or exploit parts of their new environment (niche) invasive species have greater reproductive success.  This leads to a larger and larger invasive population.  Eventually competition between the members of the invasive species will drive some of those members to seek out new habitats, resulting in more and more of the ecosystem being exploited by the invasive species causing increased environmental damage and economic cost.  
• public awareness and engagement is very important.  As I indicated above early detection and response are very important to dealing with invasive species.   Public awareness and active reporting helps in detection and monitoring of invasive species populations.  Public will to act and deal with invasive species issues also plays a big role in motivating politicians and bureaucrats to commit resources to deal with invasive species.  Lastly, it is a sad truth that one of the biggest vectors for the movement of  many invasive species into new areas is people deliberately introducing the invasive species.  The spread of many invasive species can be followed and very often it can be seen as a progression along a major roadway or transportation corridor.  Public education and awareness around the impacts is therefore a big tool in invasive species biologist toolbox to stop the spread.  

ASF Program Director for NB, Nathan Wilbur, with smallmouth bass he caught in the mainstem of the Southwest Miracmichi River.  The bass escaped from Miramichi Lake despite containment efforts by DFO.  

ASF and Invasive Species

The biggest invasive species issue that ASF is involved with is our efforts to eradicate an invasive Smallmouth Bass population in Miramichi Lake.  While usually involved with issues on a much broader scale (provincially, regionally, nationally and internationally), ASF undertakes some bigger local focused projects when the threat to Salmon is significant, there is need for larger organization like ASF to move the project forward, and there are lessons to be learned that can be applied to other areas/regions.   Miramichi Lake, like many of our large dam removal projects in Maine, was deemed to be one of these situations. 

Over a decade ago Smallmouth Bass were introduced as an invasive species into Miramichi Lake.  As part of their response, DFO implemented and maintains a containment barrier and monitoring program to keep the bass confined to the lake.  They did not deem it necessary to develop an eradication plan, despite the threat that this invasive species population poses to such an economically important salmon river as the Miramichi.  ASF stepped in and with our many partners have developed a plan to eradicate this invasive species once and for all, eliminating the threat and potentially saving the government thousands of dollars annually.  Dealing with that illegal introduction and developing the eradication plan has been plagued by numerous jurisdictional and bureaucracy issues,.  This past year the plan suffered a major setback when DFO's containment strategy failed and bass were found in the mainstem of the Southwest Miramichi just below the lake.  Despite this the first nation led coalition has persisted and are posed to begin implementation of the eradication plan this fall. 

The eradication plan will involve the use of Rotenone, a naturally occurring fish pesticide that has been used by indigenous populations for thousands of years.  While i may be shocking to say or hear that the lake and part of the river will be treated with a fish killing pesticide this has been studied very carefully and identified as the only way to conclusively eliminate the ecological and economic damage that will be caused by letting the invasive species continue to persist and grow.  "Poisoning the lake", while technically an accurate and certainly convenient headline/sound byte that grabs readers/listeners attention,  doesn't reflect the degree of care and consideration that has gone into balancing the costs of short term impact against the long term costs both economically and environmentally.  When looking at this issue on those terms it is the only viable solution and one that has been successfully used before in other systems across Canada.  For more information on the history, the treatment plan, incuding specifics on how rotenone breaks down naturally and how other compounds will be used to neutralize the rotenone so that it doesn't impact untargeted areas, I encourage you to reach out to Nathan or other members of the Miramichi Lake coalition. 

Chain pickerel, which have found their way into the LaHave River, are no friend to Atlantic salmon. (Robert Short/CBC)  Taken from June 8, 2017 CBC Article by Paul Withers "Chain pickerel invade critical Nova Scotia salmon habitat"

Nova Scotia 

For me here in NS, this project is especially important one that I hope to learn from as we are now facing a similar issue.  Smallmouth Bass, and another even nastier invasive species Chain Pickerel, were deliberately introduced into southern NS over a hundred years ago.  As a result these species have been long established in many of our major rivers and lakes, especially in the southern 1/2 of our province.  These populations are established such that they are well beyond the point where eradication is a feasible option. Now the focus for these populations s on managing them in these infested systems (keeping them at a acceptable level) and preventing their spread further into new territory within these systems.  Just last year Kejimkujik National Park announced changes to its harvest regulations and introduced new measures within the park designed to do just that.  The Province of NS also changed its rules a few years ago making it illegal to have live fish in your possession and making regulations to stop fishing in any water bodies that get new introductions of invasive species.  Despite these efforts invasive species are continuing spread into new systems.  It is with these newly established populations, where eradication is still possible, that we can look to the lessons learned from Miramichi Lake project. 

The invasive plant Japenese Knotweed growing on PEI.  This species can choke out native species of plants and has the potential to dramatically alter the riparian zones of trees and bushes that line rivers and streams. 

PEI

According to a PEI government website, PEI has recognized 6 common invasive plants and 5 common invasive insects (https://www.princeedwardisland.ca/en/information/environment-water-and-climate-change/invasive-plant-and-animal-species).   Undoubtedly PEI has many more invasive species, as clearly from context this isn't intended to be a comprehensive listing of all invasive species on the Island, rather a simple list of some of the most common invasive species for the public to watch out for. The site does point the reader to more comprehensive sources such as the PEI Invasive Species Council and PEI Nature Tracker.   Thankfully at least from a salmon perspective, PEI doesn't yet have an invasive fish species problem.  There have been concerns around Rainbow Trout an introduced non-native species, but recent published work (Canadian Journal of Fisheries and Aquatic Sciences, 2018, 75(11): 1949-1959, https://doi.org/10.1139/cjfas-2017-0342) by PEI Council President, Scott Roloson, is showing that these species are likely not causing an invasive species level of impact.  One potential invasive species concern for salmon and trout on PEI has to do with the invasive plant, Japenese Knotweed.  This ornamental plant, which escapes from nurseries and gardens, can grow very rapidly and will out out compete most native bushes and trees.  Once established it becomes very difficult to remove, since leaving even a small root can be enough reestablish the plant.  When it becomes established along rivers it can drastically alter the composition of the riparian zone.  Riparian zones provide important shade, woody debris, and nutrients to streams.  They also act as critical barriers to erosion preventing sediment, such as fine sand and silt from entering the stream.  Riparian zone management  is a major concern everywhere but especially on PEI.  For salmon and trout any invasive species that can impact the riparian zone has the potential to have significant impacts on stream function and fish populations. 

What to do

What can you do? As I mentioned earlier in this article public awareness and involvement is crucial in dealing with invasive species.  By knowing what plants and animals are native to your area and what ones aren't you can take actions to help stop the spread of invasive species.  Help stop the spread, get informed.  You can get more information on invasive species by:

• contact your government office.  Fisheries, natural resources, and environment department offices will all have information on invasive species or can point you in the right direction.
• get involved or attend meetings and seminars for your local river and environmental organizations.  These organizations often are involved in dealing with invasive species and can use your support.  They often offer great programs for free, such as one identified in the first pic of this blog where Clean Annapolis River Project was hosting a bunch of free seminars to promote National Invasive Species Awareness Week,.  
• visit, either virtually or in person, a natural history museum or interpretive center in your area
• contact your local library.  Librarians are wonderful people that can help you find out anything you would like to know, and I am not just saying that because I married one.

By getting informed, taking appropriate actions, and being vocal about invasive species issues you can make a real difference and help preserve and protect your environment.  

Cheers