Risk Assessment to manage aquatic weeds

1. Risk Assessment to manage aquatic weeds Paul Champion, Rohan Wells, Mary de Winton, Tracey Edwards NIWA, Hamilton

2. Introduction • How bad is your aquatic weed? - Weed Risk Assessment • How and where will it go? - Modelling invasions • How valuable is your waterbody? - Ecological assessment and Lake SPI • Building an aquatic weed management strategy – • High-risk species and sites • Surveillance • Incursion response

3. How bad is your aquatic weed? • Weed Risk Assessment models • Around for the past decade or so, mostly for screening imports • Pheloung (1995) used in Australia and New Zealand • Usually score of 1 or -1 allocated to each weed attribute • Rejection score (no importation if >6) • Further evaluate if score 1-6 • If an aquatic automatically score 5 • Model brands all aquatic spp. as potential weeds (Gordon & Gantz 2011)

4. Aquatic Weed Risk Assessment Model (AWRAM) Champion and Clayton (2000) • Model assesses: • Invasiveness – e.g.habitat versatility • Competitive ability • Dispersal – propagule/diaspore output, natural vs human (deliberate/accidental) • Impact – economic, environmental, recreational • Potential distribution – current vs uncolonised habitat • Resistance to management – scope of methods, effectiveness • Maximum theoretical score of 100

5. AWRAM score is a synthesis of characters relevant to the weed potential and management of a species Provides a means for managers/policymakers to prioritise species for control actions AWRAM requires well documented information on the species performance which can be supplemented with experiments and field observations (e.g. other spp. displaced, control)

6. NZ Top 16 SpeciesRanking Phragmites australis 75 Hydrilla verticillata 74 Zizania latifolia 68 Ceratophyllum demersum 67 Eichhornia crassipes 67 Egeria densa 64 Alternanthera philoxeroides 63 Lagarosiphon major 60 Nymphoides peltata 58 Typha latifolia 58 Gymnocoronis spilanthoides 57 Salvinia molesta 57 Myriophyllum aquaticum 56 Lythrum salicaria 54 Utricularia gibba 54 Iris pseudacorus 52

8. New Zealand Applications • Managing risks offshore (NO and UO) e.g. Trapa natans, Eurasian milfoil • NPPA for managing deliberate spread (Champion 2005) • NIPR national eradication programmes e.g. phragmites, SI hornwort • RPMS determine regional weeds for management

9. Status in NZ SpeciesStatus Phragmites australis NIPR Hydrilla verticillata NO, NIPR Zizania latifolia NO, NIPR Ceratophyllum demersum NIPR Eichhornia crassipes NO, NIPR Egeria densa RPMS, NPPA Alternanthera philoxeroides RPMS, NPPA Lagarosiphon major NPPA Nymphoides peltata RPMS, NPPA, eradicated Typha latifolia NO, NPPA, eradicated Gymnocoronis spilanthoides RPMS, NPPA Salvinia molesta NIPR Myriophyllum aquaticum RPMS, NPPA Lythrum salicaria RPMS, NPPA Utricularia gibba NPPA Iris pseudacorus RPMS, NPPA

11. International Applications • Australia to manage the aquarium/pond plant trade • (Petroeschevsky & Champion (2008); Champion et al. (2010)) • Guam and Micronesia for biosecurity plan (Sytsma et al. 2011) • USA national priority lists for management – 90+% selection of weed vs non-weed (Gordon et al. in press) • Europe proposed for use to determine target weeds at EU workshop (Champion et al. 2009)

12. Aquatic Weed Spread Hornwort • Submerged weeds • Economic/recreational/ecological impacts • Prohibited for sale, propagation and distribution (since 1982) • High weed risk scores (AWRAM) Egeria Lagarosiphon Utricularia

13. Hornwort • Naturalised from aquarium/pond liberations • Vegetative reproducing • U. gibba produces seed • Spreading but not saturated • Overall, 26.7% of 344 lakes recorded one or more of these pest plants Egeria Lagarosiphon Utricularia

14. Lakes Pre-1980 1980-1999 2000-2008 Other Sites Pre-1980 1980-1999 2000-2008 Surveyed Hornwort Egeria Lagarosiphon

15. Lakes Pre-2000 2000-2005 2006-2008 Other Sites Pre-2000 2000-2005 2006-2008 Utricularia distribution

16. 70 60 50 40 Cumulative first lake records 30 20 10 0 1970 1975 1990 1995 2000 2005 1950 1955 1960 1965 1980 1985 Year Spread rate Lagarosiphonmajor Utricularia gibba Ceratophyllum demersum Egeria densa

17. Legislation has reduced propagule pressure • ‘Sleeper’ colonies remain in garden ponds • Dispersal pathways in common • We can predict risk factors for lakes? • Modelling BRT approach (Compton et al. 2010) • Current distribution • Anthropogenic factors

18. Results: Spatial predictions

19. Indigenous Biodiversity Value Three components: • Indigenous biota • Endangered species • Habitat availability

20. Indigenous biota • Richness: total number of indigenous macroscopic species (fauna and flora) in the lake or wetland margins. • Abundance: area and cover present for flora; population size for fauna. • Representativeness: significance of the communities (not species rarity).

21. Endangered species • New Zealand Threat Classification System lists R. Hitchmough; L. Bull; P. Cromarty (Comps) 2002; --2007; also using de Lange et al. (2009)

22. Habitat availability Extent or area for indigenous vegetation (wetland, emergents and submerged vegetation) • Natural character (water quality, development of catchment) & • Impact of invasive spp.

23. Worked example -Lake Kai-Iwi

24. Worked example -Lake Kai-Iwi Indigenous biota • Indigenous species number • 17 plant, 10 bird, 2 fish, 5 invertebrate spp. 4/6 • Abundance • 75-95% submerged plant cover over 10 m+ depth range, 95% fringe of emergent spp., rapid transition into terrestrial scrub. Dense populations of common bully etc 5/6 • Representativeness • Mixed charophyte dominated submerged vegetation, kuta and Baumea arthrophylla dominated emergent vegetation, Trithuria dominated turf 6/6 • Total score 5/6

25. Worked example -Lake Kai-Iwi Threatened species • Acutely threatened • Bittern (non-resident but breeding habitat in adjacent wetlands), Trithuria inconspicua (largest population in Central Northland), dune galaxias (extinct) • Chronically threatened • Red-billed gull (non-resident), long-fin eel (?), kakahi (rare) • Dabchick (several pairs resident), freshwater crab (large population), Centrolepis strigosa (rare) • Total score5/6

26. Worked example -Lake Kai-Iwi Habitat availability • Dense indigenous submerged vegetation 0 - 13.7 m deep 5/6 • Indigenous emergent vegetation occupies an almost continuous margin of ~ 5 m 3/6 Total score 4/6

27. Worked example -Lake Kai-Iwi • Indigenous biota 5 • Endangered species 5 • Habitat availability 4 • Total score 14 • Champion et al. (2001) ranked this lake #1 • Wells & Champion (2009) rated this lake as outstanding

28. Aquatic Plants as lake condition indicators • Non mobile, macroscopic, perennial life form • Long-term integrators of environmental conditions • Aquatic plants respond to Water clarity, Habitat complexity & Environmental disturbance • Littoral zone emphasis (vs Pelagic zone)

29. Invasive Impact Components Native Condition Components LakeSPI Components • Native Max Depth • Native Diversity • Charophyte Meadows • Native Distribution • Native Ratio • Invasive Ratio • Invasive Species Impact • Invasive Depth Impact • Nature of Invasive Cover • Invasive Maximum LakeSPI INDEX Invasive Impact INDEX Native Condition INDEX

30. LakeSPI Indices Native Condition INDEX Based on diversity and quality of indigenous plant communities Invasive Impact INDEX Based on the degree of impact by invasive weed species LakeSPI INDEX Provides an overall indication of lake ecological condition

31. Uses of LakeSPI • Describe ecological condition • Monitor trends & access changes over time • Compare lakes of contrasting depth & type • Rank the state of lakes • Prioritise lake management actions • Assess catchment & management initiatives • Contribute towards national & regional reporting

32. LakeSPI describes ecological condition… Rotorua lakes 2008/09 Invasive Impact Index Native Condition Index

33. Monitors changes over time… Change in Rotorua lakes over last 20 years Rotomahana Rotorua Rerewhakaaitu Rotokakahi Okaro Okareka Tarawera Okataina Rotoehu Rotoma Tikitapu Rotoiti % Change In LakeSPI Index 1988 – 2008/9

34. Management Strategies Lake Rotopouua 300 m Lake Rotootuauru Lake Humuhumu Lake Rotokawau Lake Waingata Lake Kanono

35. Risk ManagementHigh-risk Sites and Pathways Prevent spread of weeds by managing sources (e.g. ban motorised boats) Awareness/decontamination procedures for vectors

36. Transfer by human activities • Boats and trailers • Float planes • Weed harvesters • Weed cutting boats • Fishing equipment/nets • Coarse fish and aquarium release

37. Risk ManagementSurveillance and Incursion Response • Target high-value water bodies • For submerged spp. need: • Good identification skills • Good water clarity (possible to use sonar) • Identify entry points, anchorages, fishing spots etc.

38. Surveillance by manta board Lake Rotomahana, Bay of Plenty Region

39. Risk ManagementSurveillance and Incursion Response • Incursion response: • Delimitation survey • Containment • Control/eradication • Follow-up

40. Grass Carp

41. Acknowledgements Thanks to all the NIWA team, regional councils, DOC and MAF staff involved in these projects