Discovery of a host fish species for the threatened New Zealand freshwater mussel Echyridella aucklandica (Bivalvia: Unionida: Hyriidae)

ABSTRACT

Larvae (glochidia) of Unionida mussels form obligate symbiotic associations with host fish to complete their life-cycle. To identify previously unknown host fish associations for the threatened New Zealand Echyridella aucklandica, glochidia infestation on fish by two mussel species was quantified in four Waikato streams. A host for E. aucklandica was identified for the first time, with glochidia found to attach and encyst on the common smelt Retropinna retropinna but not on other fish species caught. In contrast, E. menziesii was found on a range of fish species but not on the two R. retropinna caught. Encysted E. aucklandica glochidia showed evidence of growth on the gills of host fish. These preliminary results provide critical knowledge of host–glochidia interactions in sympatric New Zealand unionid species to support integrated conservation management targeting both unionid communities and host fish populations.

KEYWORDS:

• Freshwater mussel
• unionid
• host fish
• symbiosis
• Retropinna retropinna
• conservation

Acknowledgements

The authors thank Thomas Allen and Elmie Senekal for laboratory and field assistance. Thanks to Nora Palmer (Paepaeruru Trust), Brent Pini and Noel Bamber for land access, and to the anonymous reviewers for valuable feedback on the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research was funded by The New Zealand Ministry of Business, Innovation and Employment (MBIE) grant to NIWA for the ‘Cultural Keystone Species: Co-management and restoration’ Programme (Grant No. CK01X1616; Animal Ethics Project No. 191).