The role of baitfish in the spread of AIS · For a pathogen to spread along the baitfish pathway, a...

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

thom4412@umn.edu

Twitter: megmcea

Dr. Nicholas Phelps