Slide 1: title
Slide 2: Nonnative trout invasions
Management issues
- Issues
- Alternatives
Research to model invasions
- Brook trout example
Management application
- Addressing “invasion vs. isolation”
Lessons learned
Slide 3: Nonnative salmonids
- Economic and social values
- Threats native species and ecosystem values
Slides 4 & 5: (map, Crawford and Muir, 2007)
Slide 6: Issues
Threats
- native species
- ecosystems
Slide 7: Issues
Threats
- Focus on native fishes
Slide 8: Four Major Management Alternatives
- Do nothing
- Prevention
- Eradication
- Coexistence
Slide 9: Management Alternatives
Do nothing when…
- No evidence of impacts
- Fishery judged to be too valuable
But…
- Monitor to track invasions
Slide 10: Management Alternatives
- Prevention
- Public education
- Regulation
Slide 11: Management Alternatives
Prevention
- Early detection
- Detectability (chart)
Slide 12: Managment Alternatives
Prevention
Barriers
- Prevent upstream invasion
- Isolate natives
Slide 13: Invasion versus isolation
- Will restored connectivity allow nonnatives to invade?
- Will installation of barriers to prevent invasions lead to extinction?
Slide 14: Management Alternatives
Eradication
- Selective
- Non-selective
Slide 15: Management alternatives
Non-selective eradication
- Use of toxins
- Flow diversion, pumping
Can be 100% effective, but…
- Non-target effects are a threat
- Expensive (e.g., >$1,000,000 US)
Slide 16: Management Alternatives
Selective eradication
- Trapping, fishing
- Pheromones
Can minimize damage to other species, but…
- Very seldom 100% effective
- Very expensive
Slide 17: Four Major Management Alternatives
Do nothing
- values burden of proof
Prevention
- Ineffective?
Eradication
- too little too late?
Coexistence????
Slide 18: Coexistence?
- Manage habitat to benefit natives
- Manage to discourage nonnatives
- Condition-specific interactions
- Habitat and nonnatives not separate
Slide 19: What is “coexistence?”
- Definition is case-specific.
- Stability through time - unstable
Slide 20: What is “coexistence?”
- Definition is case-specific.
- Stability = coexistence?
Slide 21: What is “coexistence?”
- Definition is case-specific.
- Spatial context.
Slide 22: What is “coexistence?”
- Spatial context.
Slide 23: What is “coexistence?”
- Definition is case-specific.
- Stability through time.
- Spatial context/scale.
- In practice co-occurrence = coexistence.
Slide 24: Managing for coexistence – key criteria
1. Other, more direct, alternatives to limit the invader are not feasible
Slide 25: Managing for coexistence – key criteria
2. Must be variation in the undesirable impacts of an established invader
Slide 26: Managing for coexistence - key criteria
3. Factors influencing this variability are understood – at least enough to develop testable hypotheses
Slide 27: Manageing for coexistence
4. We can manage those factors to effectively influence impacts
Slide 28: Can research help management?
Lessons from past experience?
Case study:
nonnative brook trout (Salvelinus fontinalis) in North America
Slides 29 & 30: Maps
Slide 31: Review of brook trout invasions: management relevance
Lessons Learned
Most research at small spatial and temporal scales
- ≠ management
- Aquariums
- Stream enclosures
- Etc.
Slide 32: Review of brook trout invasions: management relevance
Lessons Learned
- Many potential mechanisms, but no conclusive generalities
- Variable results among studies – difficult to compare
- Emphasis on studying impacts, less on invasion process
Slide 33: Review of brook trout invasions: management relevance
Lessons Learned
- Management limited to “no action” or eradication
- Managing for “coexistence” is seldom recognized
- Not much effort on weighing the options from research
Slide 34: Brook trout invasion: recommendations
- Need for a broader-scale predictive understanding
- Models to predict
- Occurrence of nonnatives
- Occurrence of natives
- Coexistence
Slide 35: Different mechanisms can explain the same pattern of coexistence
Slide 36: (Map) Predicting patterns of invasion by brook trout in Panther
Creek Idaho
(Benjamin 2006, Benjamin et al. 2007)
Slide 37 (Map) Predicting patterns of invasion by brook trout in Panther
Creek Idaho
(Benjamin 2006, Benjamin et al. 2007)
Slide 38: (Illustration)
Slide 39: Analysis
- Logistic regression
- Model selection (Burnham and Anderson 2002)
Slides 40, 41 (maps)
Slide 42:: Model Results (no AVB)
- Large brook trout model – inconclusive
- Small brook trout – predictable distribution
- Valley bottoms - connectivity
- Summer and winter temperature
- Natives and nonnatives coexist – for now
- Greatest overlap with cutthroat trout
- Coexistence management
- Habitat (Temperature)???
- Biotic resistance ???
- Barriers?
Slide 43, 44, 45 - charts
Slide 46: Summary
Large brook trout model – inconclusive
Small brook trout – predictable distribution
- Valley bottoms - connectivity
- Summer and winter temperature
Natives and nonnatives coexist – for now
- Greatest overlap with cutthroat trout
Coexistence management
- Habitat (Temperature)???
- Biotic resistance ???
Barriers?
Slide 47: Management Application
Invasion vs. Isolation
- Will restored connectivity allow nonnatives to invade?
- Will installation of barriers to prevent invasions lead to extinction?
Slides 48, 49, 50, 51: Charts
Slide 52: Definitions
- Invasion Barrier - A natural or human-constructed barrier that precludes upstream movement by stream fishes.
- Habitat Degradation - Whether salmonid habitat and the processes that create and maintain it have been altered by human activity.
- Fishing Exploitation - Fishing exploitation rate of subadult and adult (aged 2 and older) westslope cutthroat trout in a stream network.
- Potential Life History - The potential expression of migratory and resident life histories, respectively, for cutthroat trout in a stream network.
- Connectivity Potential - The potential for immigration and demographic support for a local population of cutthroat trout
- Effective Network Size - Size or spatial extent of the local population and its vulnerability to environmental variation and catastrophic events.
Slide 53: Now for a look at 48 scenarios
Slides 54, 55, 56: Charts
Slide 57: Lessons
- Nonnative salmonines are here to stay
- Widely established
- Impacts well-known
- Not the same everywhere all of the time
- Coexistence is underemphasized
- More information-intensive…
Slide 58: Lessons
- Complex problems ≠ simple solution
- Addressing stages of invasion
- Spatial and temporal variation in impacts
- Variable influences of different factors
- Tools for putting the pieces together
Slide 59: Lessons
- Good information is valuable
- $$$ emphasis “on the ground”
- Activity ≠ real progress
# stream miles “protected”
vs.
increased probability of persistence?
Slide 60: Lessons
- Good information is essential
- $$$ emphasis “on the ground”
- Activity ≠ real progress
- Where is action needed?
- What kind of action?
- Can we combine action and learning?
- If we can’t do it here we’re probably out of luck
(For more information contact the author at jdunham@usgs.gov)