eDNA investigations in the Pāuatahanui Catchment

An exploration into fish presence and distribution

May 23, 2024

The Pāuatahanui Catchment has four main streams that feed into the Pauatahanui inlet, The Kakaho Stream, Horokiri Stream, Duck Creek and the Pāuatahanui Stream which is fed from the Haywards Hill, Judgeford, Belmont area. The Pāuatahanui Stream is the largest of the six catchments that flow into Te Awarua o Porirua. The stream provides a habitat for a range of indigenous and threatened fish species, including the giant kōkopu, short-jaw kōkopu, longfin eel, inanga and redfin bully. Piharau (lamprey), which are considered to be nationally vulnerable, have also been observed in the catchment

Through EPA’s Wai Tu Whera o Te Taiao, a funded eDNA project was undertaken to better understand what is living in each of the sub-catchments of the Pāuatahanui Stream and get a better understanding of fish distribution. From this information we hope to gain insights into potential fish passage barriers in the catchment. - Read on to see what we discovered and where

Upper Moonshine

Batch: 518902

Lower Moonshine

Batch: 531227

Haywards Stream

Batch: 531215

Pāuatahanui - mid catchment

Batch: 531209

Flightys Stream

Batch: 514042

Belmont Stream

Batch: 531221

Upper Moonshine

Lower Moonshine

Tuna: Shortfin Anguilla australis

Haywards Stream

Tuna: Shortfin Anguilla australis

Pāuatahanui - mid catchment

Tuna: Shortfin Anguilla australis

Flightys Stream

Tuna: Shortfin Anguilla australis

Belmont Stream

Tuna: Shortfin Anguilla australis

Upper Moonshine

_{Tuna: Shortfin Anguilla australis}

_{Tuna; Longfin Anguilla dieffenbachii}

_{Kōkopu, Banded Galaxias fasciatus}

_{Kōaro Galaxias brevipinnis}

Lower Moonshine

_{Tuna: Shortfin Anguilla australis}

_{Tuna; Longfin Anguilla dieffenbachii}

_{Piharau, Lamprey Geotria australis}

_{Kōaro Galaxias brevipinnis}

_{Kōkopu, Banded Galaxias fasciatus}

_{Kōkopu, Shortjaw Galaxias postvectis}

_{Kōkopu, Giant Galaxias argenteus}

_{Īnanga Galaxias maculatus}

_{Bully, Redfin Gobiomorphus huttoni}

_{Bully, Common Gobiomorphus cotidianus}

_{Brown trout Salmo trutta}

Haywards Stream

_{Tuna: Shortfin Anguilla australis}

_{Tuna; Longfin Anguilla dieffenbachii}

_{Kōkopu, Banded Galaxias fasciatus}

_{Kōkopu, Shortjaw Galaxias postvectis}

_{Kōkopu, Giant Galaxias argenteus}

_{Īnanga Galaxias maculatus}

_{Bully, Redfin Gobiomorphus huttoni}

_{Bully, Common Gobiomorphus cotidianus}

_{Brown trout Salmo trutta}

_{Smelt, Common Retropinna retropinna}

Pāuatahanui - mid catchment

_{Tuna: Shortfin Anguilla australis}

_{Tuna; Longfin Anguilla dieffenbachii}

_{Kōaro Galaxias brevipinnis}

_{Piharau, Lamprey Geotria australis}

_{Kōkopu, Banded Galaxias fasciatus}

_{Kōkopu, Shortjaw Galaxias postvectis}

_{Kōkopu, Giant Galaxias argenteus}

_{Īnanga Galaxias maculatus}

_{Bully, Redfin Gobiomorphus huttoni}

_{Bully, Common Gobiomorphus cotidianus}

_{Brown trout Salmo trutta}

_{Smelt, Common Retropinna retropinna}

Flightys Stream

_{Tuna: Shortfin Anguilla australis}

_{Tuna; Longfin Anguilla dieffenbachii}

_{Kōkopu, Banded Galaxias fasciatus}

_{Kōkopu, Giant Galaxias argenteus}

_{Īnanga Galaxias maculatus}

_{Bully, Common Gobiomorphus cotidianus}

Belmont Stream

_{Tuna: Shortfin Anguilla australis}

_{Tuna; Longfin Anguilla dieffenbachii}

_{Piharau, Lamprey Geotria australis}

_{Kōkopu, Banded Galaxias fasciatus}

_{Kōkopu, Giant Galaxias argenteus}

_{Kōkopu, Shortjaw Galaxias postvectis}

_{Īnanga Galaxias maculatus}

_{Bully, Common Gobiomorphus cotidianus}

_{Bully, Redfin Gobiomorphus huttoni}

_{Bully, Giant Gobiomorphus gobioides}

_{Brown trout Salmo trutta}

_{Smelt, Common Retropinna retropinna}

The monitoring sites depicted on the map were selected on the basis of getting a good capture of the whole catchment, getting a separate report for each stream and also considering upper and lower sites to highlight sections of potential migration loss

Across all 6 samples, banded kōkopu, longfin and shortfin eels were detected. Koaro had also made it to "Upper Moonshine" but none of the other Galaxias were recorded. "Pāuatahanui-mid" on the other hand had the largest number of different fish species, with an Average TICI score of 97. Upper Moonshine had the least diversity of fish, but gets the highest TICI score at 110 (Excellent) - this indicates that there is likely some barriers for the fish to access this part of the catchment as it is presenting as an otherwise healthy ecosystem

Next steps are to attempt to understand why each of the survey sites, Upper Moonshine in particular, aren't receiving the same diversity as the lower sites. With presumed fish passage barriers at play we encourage everyone in the catchment to survey the streams on their property and to assess whether remediation is required