THANK YOU TO ALL PARTICIPANTS!
Let's Be Early Birds and Stop the Worm!
Summary of workshop held on February 18, 2009 at CBU
We’d like to thank all of the participants of the Invasive Eel Swimbladder Nematode Workshop that was held at Cape Breton University on February 18th, 2009. We had 40 participants, with representatives from First Nations (Eskasoni/Unama’ki Institute of Natural Resources, and Waycobah Fisheries and Wildlife), Parks Canada, Department of Fisheries and Oceans, Provincial Fisheries, Atlantic Elver Fishery, South Shore Trading Company, Saint Mary’s University, Cape Breton University, Salmon River Salmon Association, Department of Natural Resources, and Louisbourg Seafoods).
The three key objectives of the workshop were:
1) information dissemination – getting the word out about the parasite
2) fostering collaborative partnerships – ensuring standardized protocols if possible, information sharing to reduce overlap
3) discussing research priorities – “if you had $1 million dollars to construct a research project on the invasive swimbladder worm, what would you do?” To start the workshop, there were a number of informative presentations:
- Parasites as agents of disease in animals (including humans)- Dr. Cheryl Bartlett, Canada Research Chair, Integrative Sciences, CBU
- An excellent overview of parasites and relevant terminology (e.g. infect = parasites that reside inside the host, infest = parasites that reside on the outside of the host)
- Clearly defined the terms intermediate hosts (required vector) and paratenic hosts (facultative vector)
- Parasites cause diseases and may or may not kill the organisms
- Talked about the differences between two common types of parasites: the flatworms and the roundworms (Anguillicoloides crassus is a roundworm)
- Focused on the life cycles of Dracunculoidea (the group of nematodes that includes A. crassus; Dracunculoidea are the DRAGON WORMS)
- Anguillicoloides crassus: An invasive swimbladder parasite of anguillid eels - What we know and where to go!- Cheryl Wall, MSc candidate, Saint Mary’s University and workshop co-host (Co-authors: Dr. David Cone (SMU) and Dr. Martha Jones (CBU)
- Originates from East Asia - Japanese eel, Anguilla japonica; no pathological effects in native host
- In other anguillid eels it can cause problems with swimbladder lining, increased anal redness, decreased host energy, and buoyancy control problems
- Presented life cycle information for the eel and the parasite
- Presented maps about what we currently know here in Cape Breton (the parasite is present at every site we have looked at); it is also present in NB and northern mainland Nova Scotia – it is not yet present in Prince Edward Island or southern Nova Scotia
- Why be concerned about A. crassus?
- Effects on commercial fishery?
- A. crassus can reduce the hardiness of eels in captivity (transport and market?)
- Importance of eel (“kat”) to First Nations
- Prevalence of A. crassus has been known to reach 100% within 1 year of introduction
- Decline of St. Lawrence eel populations: Restocking programs a risk?
- Eel MEK, Research and Mapping in the Bras d’Or- Shelley Denny, Biologist and Research Coordinator, Unama’ki Institute of Natural Resources
- Eels have been declining in the Bras d’Or, Elders have been expressing this for years, they have been trying to acquire funding to study eels for just as long, but there was no money available until SARA
- The objectives of the project are to explore eels in the Bras d’Or in a manner that is relevant to the Mi’kmaw; and to show the connection between land use and the eel
- The eel swimbladder parasite was not found in surveys done by Eskasoni Fish and Wildlife in 2000, but was found in 2008/2009 surveys
- Discussed food, social, and ceremonial (FSC) significance of eels to Mi’kmaw
- They are taking both a scientific and a TEK/MEK approach to studying eels in the Bras d’Or
- Elders suggested “No eel grass, no eels”
- Conducted nearshore mapping in 2007-08 to determine eel grass distribution; results presented
- Provided preliminary data for parasite distribution in the Bras d’Or
- Summary of sampling by Department of Fisheries and Oceans during summer 2008- Dollie Campbell, Research Technician, Bedford Institute of Oceanography, DFO (Co-authors: Dr. Rod Bradford and Dr. David Cairns (DFO))
- Objectives :
- To define the present distribution of the parasite
- To estimate intensity and prevalence of infection where present
- Explore indicators of potential impact on health of infected eels
- Which other (diadromous) species managed by DFO are susceptible to infection (2009)
- Discussed details of the 2008 Electrofishing survey (map with 139 river sites in mainland Nova Scotia)
- Presented estimated American eel densities for watersheds (no apparent trends)
- 1,510 eels retained for parasite analysis, length, weight, age analysis
- Objectives :
- Summary of projects and initiatives for Provincial Fisheries in our region- John MacMillan, Biologist, Inland Fisheries Division, NS Department of Fisheries and Aquaculture
- Responsible for freshwater fisheries for brook trout, brown trout, rainbow, landlocked salmon, perches, smallmouth bass, and chain pickerel
- Recreational fishery is worth about $52 million in direct and indirect expenditures
- Three provincial hatcheries: Margaree, Fraser Mills and McGowan lake
- Base of operation is in Pictou
- Special Trout Management Areas: reduced harvest of sea run brook trout has improved fisheries – angler creels have indicated a dramatic increase in size of the catch
- Cape Breton Rivers under Special Management include: Baddeck, Middle, Aspy, Lake-O-Law, and River Denys (2006) o Discussed population assessment methods and results for brook trout (River Denys Basin and Highland Lakes)
- Ensuring the future of American Eel in Atlantic Canada’s National Parks: A Community approach in partnership between PCA and First Nations- Deborah Austin, Parks Canada (Co-authors: Alyre Chiasson (U de Moncton) and Renee Wissink (Parks Canada))
- Eels are present in all Atlantic parks; however, large knowledge gaps exist (e.g. abundance, habitat, growth, basic ecology)
- Difficult to protect a species of which we know very little (avoid crises management response)
- Good fit with current initiatives to evaluate ecological integrity in Canada’s National Parks
- Excellent outreach opportunity: community groups including First Nations, NGOs and the general public
- Overall goal: to evaluate the status of American eel in Atlantic Parks
- Phase 1 – elvers (Sheldon traps and habitat collectors)
- Will be sampling for elvers again this summer
- Phase 2- adults
- Analysis of pre-existing data (e.g. electrofishing, smolt wheels)
- Length/weight/girth data collection and analysis
- Radio tagging is proposed as well to identify seasonal habitat use
- Concluding Remarks:
- Short term: Continue elver work with earlier deployment and more traps
- Long term
- Provide potential index sites for American eel
- Contribute to general understanding of the species ecology and recovery
- Work with aboriginal groups on a number of initiatives
- Getting the message out: Project UFO (Unidentified Foreign Organisms)- Dr. Martha Jones, Biology, CBU
INFORMAL NOTES FROM THE GENERAL DISCUSSION/QUESTIONS AFTER PRESENTATIONS
Are there adaptations in the eel to the infections?
Not really known for American eels; there may be something in the literature for European eels
Are there pathological effects in paratenic hosts?
They are in larval stages while passing through intermediate and paratenic hosts so it is likely that they are probably very small and are also not sucking blood at these stages; they will likely be affiliated with respiratory structures in intermediate and paratenic hosts
What is an ideal host for the worm?
Probably could not single out one preferred intermediate host; Anguillid eels are the final host for the worm, and the worm becomes sexually mature inside the eel swimbladder, then they die after they have reproduced
Do larger eels have more parasites?
Some studies have found correlations between size of eel and number of worms or mass of worms in the swimbladders; the number of worms per eel is probably proportional to how many things the eel eats, so it makes sense that the larger the eel, the more it’s eating and the more varied it’s diet will be – hence a greater likelihood of ingesting larval worms
Elver sampling – dates?
2 weeks after ice leaves lakes (at least for South Shore NS)
Lunar periodicity? Yes – best with full moon
Eel adults – movements in batches?
Silvers leave in fall, and the timing is affected by water temperature; the bulk of the silver eels exit the mouths of streams within over 1-2 nights. o If you want to capture silver eels, the best thing to do is ask a fisherman
Physiometrics – e.g. condition factor – are there baseline condition factors for “healthy eels” already available?
Condition factors (K) for eels are highly variable, it was suggested that it would be best to look at normal versus infected eels within the same river system/watershed, instead of across large areas – the typical caveats about variability in condition factor apply (e.g. seasonality, sexual maturity).
In addition, for infected eels, you may want to correct condition factor between infected and non-infected eels by removing the weight of the worms before calculating K.
There was some discussion about American eels (Anguilla rostrata) not being as affected as much as (A. anguilla) by infection – I wasn’t able to find a reference to this after the workshop (if anyone has a paper on this, please let me know)
We also discussed whether the eel populations will reach a threshold level of infection, after a peak in infection shortly after initial introduction. Some of the references from Europe do report on the “leveling off” of infection rates, but the threshold level seems to be highly variable from one system to another.
Any concern about biases in sampling methods and assessment of infection rates? (i.e. if certain methods are less likely to capture unhealthy eels, they may underestimate infection rates)
This something that should be given consideration; no one could recall reading any published papers that addressed this – both active (e.g. beach seines) and passive (e.g. traps) trapping methods are encouraged
Research priorities – We asked the hypothetical question “if you had $1 million for research, what would you focus on?
Several participants felt that research might be futile – “it’s going to be everywhere in the very near future”…(so why bother trying to survey where it currently is)
Others felt that “eels seem to be fine despite infection”
“It’s in all eel aquaculture facilities worldwide and we can’t get rid of it”
So why bother studying it?
There are many of us who feel that it is necessary to understand the distribution and ecology of the worm and its effects on American eels in our region for a number of reasons, namely:
- We don’t know how natural populations of American eels in our region are going to be affected by the invasive worm
- Infection rates of 100% can be reached within one year of introduction
- We are in the more northern part of the geographic range of American eel and studies have shown that the larger, more fecund females are found as you move northward throughout the range
- We do not know whether infected eels will be successful at migrating to their spawning grounds in the Sargasso Sea (See Palstra et al. 2007 – “Swimming performance of silver eels is severely impaired by the swimbladder parasite Anguillicola crassus” – this was about European eels, but a similar study should be carried out on the American eel.)
There appeared to be consensus that scientists should try to learn more about the “big black box” of migration to the Sargasso Sea for spawning. There was some discussion about the Ocean Tracking Network, and how eels might be a part of that. There was also some discussion about a study that researchers are going to undertake in the Sargasso Sea to attempt to learn more about eel migrations. If anyone is aware of who is doing this research, we’d like to know. Sounds interesting.
A number of workshop participants felt that genetics research would also be insightful. It would be good to know where our nematodes came from (was it a “leap frog” from the eastern United States (bilge/ballast), or a new introduction from Europe (sea chests/ballast)). Cheryl Wall will be doing some molecular work at Saint Mary’s University to investigate this.
Shelley Denny suggested that otolith research similar to her herring study should be done on eels as well. Examples included: Sr:Ca ratios to examine life history of eels (marine, brackish and fresh water habitation), and age analysis to better understand population demographics in our region.
If otoliths are part of your project, plan for it – they are expensive to process (either in-house or farmed-out (e.g. $33/otolith for annular aging, and ~$100/otolith for elemental analyses))
Otoliths should be stored dry prior to processing – please visit Steve Campana’s website for information about otolith storage, preparation and analysis
ASSUMPTIONS ABOUT HISTORY OF NEMATODE IN OUR REGION
It was emphasized that we should be careful about our assumptions about the history of the nematode in our region. Are there better ways of trying to piece together the time of invasion? The direction of spread? The rate of spread? It was suggested that we should attempt to get a better timeline of that history if at all possible.
Traditional Ecological Knowledge (TEK) and Mi'kmaw Ecological Knowledge (MEK) was also suggested as a good way of trying to piece together the history – Shelly Denny has incorporated these ideas into her research plan for this year.
MODELING – It was suggested that essentially the three things we are concerned about regarding the invasive worm are:
1) the mechanism of introduction into the eel population in our region,
2) how it spreads through the population, and
3) what will be the effect on production in the population? - Bruce Hatcher suggested that there are already some good epidemiological models for our area, ones that have come out of studies on another invasive aquatic pathogen, the MSX parasite in oysters in the Bras d’Or - If anyone knows of any modelers interested in taking on another project, please pass this information on to them.
Dissection Demonstration – led by Cheryl Wall Dissection instructions were provided to conference participants, please let us know if you would like to receive a copy of the instructions. Over 20 people stayed for the dissection demonstration, and a number of you commented on how useful you found it.
Both Cheryl and I learned a few things from doing the demonstration as well. Thanks to all participants who didn’t mind getting their hands slimy and jumped right in!
Thanks again to our sponsors: NSERC Atlantic Regional Opportunities Fund, Cape Breton University Faculty Association (www.cbufa.ca/news/), Project UFO (www.ProjectUFO.ca), Cape Breton University (www.cbu.ca), Unama’ki Institute of Natural Resources (www.uinr.ca), and Louisbourg Seafoods
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Folia Parasitologica 41: 65-70. _________, and B. Skorikova. 1998. Amphibians and larvae of aquatic insects as new paratenic hosts of Anguillicola crassus (Nematoda: Dracunculoidea), a swimbladder parasite of eels. Diseases of Aquatic Organisms 34: 217-222. _________, and H. Taraschewski. 1988. Revision of the genus Anguillicola Yamaguti, 1935 (Nematoda: Anguillicoloidae) of the swimbladder of eels, including descriptions of two new species, A. novaezelandiae sp. n. and A. papernai sp. n. Folia Parasitologica 35: 125-146. Moser, M.L., W.S. Patrick, and J.U. Crutchfield. 2001. Infection of American eels, Anguilla rostrata, by an introduced nematode parasite, Anguillicola crassus, in North Carolina. Copeia 2001: 848-853. Nagasawa, K., Y. Kim, and H. Hirose. 1994. Anguillicola crassus and A. globiceps (Nematoda: Dracunculoidea) parasitic in the swimbladder of eels (Anguilla japonica and A. anguilla) in East Asia: a review. Folia Parasitologica 41: 87-93. Nimeth, K., P. Zwerger, J. Wurtz, W. Salvenmoser, and B. Pelster. 2000. Infection of the glass-eel swimbladder with the nematode Anguillicola crassus. Parasitology 121: 75-83. Norton, J., D. Rollinson, and J.W. Lewis. 2005. Epidemiology of Anguillicola crassus in the European eel (Anguilla anguilla) from two rivers in southern England. Parasitology 130: 679-686. Palstra, A.P., D.F.M. Heppener, V.J.T. van Ginneken, C. Székely, and G.E.E.J.M. van den Thillart. 2007. Swimming performance of silver eels is severely impaired by the swim-bladder parasite Anguillicola crassus. Journal of Experimental Marine Biology and Ecology 352: 244-256. Peters, G., and F. Hartmann. 1986. Anguillicola, a parasitic nematode of the swim bladder spreading among eel populations in Europe. Diseases of Aquatic Organisms 1: 229-230. Pietrock, M., and T. Meinelt. 2002. Dynamics of Anguillicola crassus larval infections in a paratenic host, the ruffe (Gymnocephalus cernuus) from the Oder River on the border of Germany and Poland. Journal of Helminthology 76: 235-240. Richkus, W.A., and K. Whalen. 2000. Evidence for a decline in the abundance of the American eel, Anguilla rostrata (LeSueur), in North America since the early 1980s. Dana 12: 83-97. Sokolowski, M.S., and A.D.M. Dove. 2006. Histopathological examination of wild American eels infected with Anguillicola crassus. Journal of Aquatic Animal Health 18: 257-262. For additional information, please contact: Dr. Martha Jones (email@example.com)