Freshwater pests

  • Image, Freshwater pests.

    Freshwater plant and animal pests can have significant negative effects on the health of a waterway’s ecosystems. They can reduce the indigenous biodiversity through predation, competition for food and habitat, and by damaging aquatic habitats. Freshwater plant pests can cause economic losses by blocking water intakes for hydroelectricity generation and impeding drainage or irrigation. Pests can also affect a waterway’s suitability for recreational activities.

    We classified Freshwater pests as supporting information.

    Key findings

    In 2013, NIWA identified nine fish species, 11 invertebrate species, and 41 plant species as pests of greatest concern for New Zealand’s freshwater environments.

    Of the 61 species:

    • one fish, two invertebrate, and four plant species were likely to have been eradicated
    • some species were observed in only a few locations, whereas others were found across New Zealand
    • the algae didymo (Didymosphenia geminata) was present in more than 150 South Island rivers but not found in any North Island river systems.

    Figure 1

    Number of pest species of greatest concern by major taxonomic group, 2013
    Species group

    Species

    Species thought to be eradicated

    'Unwanted' or 'notifiable' species listed in the Biosecurity Act 1993

    Number

    Fish

    9

    1

    3

    Invertebrates

    11

    2

    2

    Plants (algae)

    2

    0

    1

    Plants (aquatic weeds)

    39

    4

    28

    Note: This list includes species thought to have been eradicated and/or listed under the Biosecurity Act 1993.
    Source: NIWA

    Figure 2

    Freshwater pests – plants, fish and invertebrates – interactive map

    Definition and methodology

    Observations of freshwater pests have been mapped from pre-1980 to 2013. The maps include observation data from three databases: NIWA’s Freshwater Fish Database, NIWA’s Freshwater Biodata Information System for invertebrates and plants, and the Ministry for Primary Industries’ Didymo Samples Database.

    The information held in these databases was supplied by a variety of individuals and institutions. Observations were made using different methods, including line fishing, electrofishing, nets and traps, snorkelling, diving, and spotlighting.

    Sites were classified by land cover using the River Environment Classification (Snelder & Biggs, 2002).

    Data quality

     Topic Classification   Relevance Accuracy 
     Pests, diseases and exotic species  Supporting information

     

    Direct

    Medium

    See Data quality information for more detail.

    References

    Snelder, T & Biggs, B (2002). Multiscale river environment classification for water resources management. Journal of the American Water Resources Association, 38(5), 1225–1239.

    Archived pages

    See Freshwater pests (archived April 2017).

    Updated 27 April 2017

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