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The role of baitfish in the spread of AIS
Identifying hazards and quantifying riskMeg McEachran, MAISRC Graduate FellowNicholas Phelps, PhD
Sam Cook, Duluth News Tribune
Baitfish fast facts:
• Minnows are most popular live bait
• $2.4 million bait industry supports even larger recreational fishing industry
• High volume, minimal testing, low traceability, lots of complexity and uncertainty
The use of live bait for recreational angling has been identified as a potential pathway for the spread of invasive species and fish disease.
What’s the actual risk and what should we do about it?
For a pathogen to spread along the baitfish pathway, a series of steps must occur.
Identifying the hazards Quantifying risky behaviors
For a pathogen to spread along the baitfish pathway, a series of steps must occur.
Identifying the hazards Quantifying risky behaviors
Identifying the hazards
• Hazard: biological organism that causes disease in the organism(s) of interest
• Recent survey of Minnesota bait shops found several viruses, parasites, and bacteria in golden shiners.
Dozens of pathogens, lots of uncertainty, limited resources. What’s a manager to do?
Do nothing Precautionary Principle
Reactive management of outbreaks
Test for and regulateeverything
Allow everything, ban nothing
Ban live bait
Dozens of pathogens, lots of uncertainty, limited resources. What’s a manager to do?
Do nothing Evidence-based hazardprioritization
Precautionary Principle
Reactive management of outbreaks
Balance benefits of live bait use with risks
Test for and regulateeverything
Allow everything, ban nothing
Identify and target the most hazardous pathogens
Ban live bait
All fish pathogens
Are fish of concern susceptible?Are bait species considered not susceptible due to
significant uncertainty or lack of empirical evidence?
Are legal baitfish species susceptible ?
Is the potential pathogen listed by any of the following?: World Animal Health Organization, Minnesota Department of Natural
Resources, Minnesota Statutes, Bait Industry, or American Fisheries Society?
Yes No
YesNo
Not considered in the ranking exercise
Not considered in the ranking exercise but flagged
for future consideration
Yes No
Yes No
Selected for consideration in the
hazard ranking exercise
Not considered in the ranking exercise
Ecological impact
Economic impact
Colonization potential
Likelihood of transfer
Prevalence in MN baitfish
Current distribution
Host species
Total Weighted Risk Score = Sum of all individual criteria scores (Criteria Weight * Risk Score)
Total Risk Score
We asked the experts: what factors are most important for determining which pathogens present the greatest risk to wild fish health?
Type of Stakeholder-Expert Number Average years of experience (min-max)
Average confidence on a 1-10 scale (min-max)
Agency 12 19 (1-33) 6.17 (2-8)
Research/Academia
8 17 (3-35) 6.25 (3-9)
Industry/Enthusiasts
4 30 (10-40) 4.5 (2-6)
Probability densities of total risk scores
Infectious pancreatic necrosis virus
Spring viremia of carp virus
Black spot disease
Total Weighted Risk Score
Prob
abili
ty d
ensit
y
Enteric redmouthdisease
Heterosporosis
Asian fish tapeworm
Fathead minnow nidovirus
Viral hemorrhagic septicemia virus
Furunculosis
Black grub
Golden shiner reovirus
Probability densities of total risk scores
Infectious pancreatic necrosis virus
Spring viremia of carp virus
Black spot disease
Total Weighted Risk Score
Prob
abili
ty d
ensit
y
Enteric redmouthdisease
Heterosporosis
Asian fish tapeworm
Fathead minnow nidovirus
Viral hemorrhagic septicemia virus
Furunculosis
Black grub
Golden shiner reovirus
ConclusionsThere’s a lot of uncertainty and variability when it comes to fish pathogens and we need to embrace this, not avoid it.
Gathering expert opinion is an important tool for incorporating this variability and uncertainty.
The hazard ranking framework was effective at differentiating between clusters of pathogens, but decisions about acceptable risk have to be made by managers.
For a pathogen to spread along the baitfish pathway, a series of steps must occur.
Identifying the hazards Quantifying risky behaviors
For a pathogen to spread along the baitfish pathway, a series of steps must occur.
Identifying the hazards Quantifying risky behaviors
Quantifying risky behaviors
Two approaches to understanding angler behaviors:1. Randomly distributed mailed paper questionnaire (n=4000)
Purpose: to collect data on bait-related behaviors that can be generalized to the whole populationResults : 669 respondents
2. Non-random intercept survey administered at boat launches (n=1000)Purpose: to collect same-day, ecologically valid data to reduce social desirability and memory biasResults : 305 respondents
Postcard survey: number of respondents that reported using live minnows varied between intercept survey locations.
Of the 49 people that reported using live bait minnows that day, 15, or ~30%, stated that they released or planned to release their leftover minnows.
Proportion of respondents that released their live bait varied slightly by region, but small sample size does not permit a statistical interpretation.
Mailed survey: a majority of mailed survey respondents reported using live minnows.
99/452, or ~20%, of bait users reported releasing their leftover live baitfish.
Although bait users took an average of 24 trips per year and most did not release bait, a small number of anglers reported taking over 100 trips per year and releasing live bait.
Popular fishing areas experience more release events than less popular areas, though proportion of people who release is similar across zones.
Fewer release events More release events
ConclusionsRate of release is likely between 20% (mailed survey estimate) and 30% (postcard survey estimate) and perhaps even higher.
Number of release events varies by region in the state, suggesting hotspots for interventions.
The small number of anglers who take 100+ trips per year and who release live baitfish may be good targets for intervention
For a pathogen to spread along the baitfish pathway, a series of steps must occur.
Identifying the hazards Quantifying risky behaviors
Next steps: putting it all together
Quantifying the number of trips that result in the release of a fish infected with a dangerous pathogen
Next steps: putting it all togetherQuantifying the magnitude and complexity of this pathway will help us understand the current risk it presents and estimate “what if” scenarios: what might happen if a virulent pathogen were to enter the bait supply?
We can conduct sensitivity analyses to determine which steps in the pathway are most important for overall risk, and identify targets for management interventions.
What can managers do: Provide education about proper bait disposal, even for native bait species, and provide means to proper disposal (e.g. trash cans at launch sites)
What can you do: Talk to your friends and family who fish, model good bait disposal practices, and follow all bait-related laws and regulations.
AcknowledgementsFunding: LCCMR-ENTRF
Advisory Group:
Kelly Pennington (MNDNR)
Sean Sisler (MNDNR)
Rob Venette (UMN, MITPPC)
Kristen Nelson (UMN, NRSM)
David Fulton (UMN, USGS)
Fernando Sampedro (UMN, AHC)
Dominic Travis (UMN, CVM)
AIS Detectors & Other Volunteers
The role of baitfish in the spread of AIS: identifying hazards and quantifying risks
Meg McEachran, Graduate Research Fellow
Twitter: megmcea
Dr. Nicholas Phelps
