The pouched lamprey (Geotria australis), one of four Southern Hemisphere lamprey species, is New Zealand’s only freshwater representative of the agnathans. In contrast to that of Northern Hemisphere lampreys, the reproductive ecology of Southern Hemisphere lampreys is poorly understood, with no documented nesting sites or spawning behaviours. In the present study, we utilized passive integrated transponder tags to track migratory adult G. australis to locate spawning sites. Across 2 years, six cryptic nesting sites were discovered, each containing eggs and a single male and female lamprey. The postspawning pairs were all located underneath large boulders, with the eggs forming a coagulated cluster that adhered to the underside of the boulder. Both the male and female lamprey survived spawning for over 105 days. The observed spawning nests highlight a substantial divergence in the reproductive behaviour between Northern and Southern Hemisphere lampreys, as the present observations of G. australis are the first that support clustered cryptic egg deposition and an extended time to mortality postspawning. This study offers the first insights to the long-standing mystery of Southern Hemisphere lamprey reproduction.

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This study used an experimental approach to compare the passage success of native and exotic fish species from the temperate Southern Hemisphere over an artificial baffled fish ramp designed for overcoming low‐head (≤1.0 m) fish migration barriers. Passage efficiency was, on average, lower for the exotic species [koi carp (Cyprinus carpio), rudd (Scardinius erythrophthalmus) and rainbow trout (Oncorhynchus mykiss)] compared to the native species [inanga (Galaxias maculatus), redfin bully (Gobiomorphus huttoni) and common bully (Gobiomorphus cotidianus)]. Nonetheless, there was considerable variation between individual species, with rainbow trout outperforming common bully and juvenile inanga, but koi carp and rudd failing to pass any of the ramps. The differences in predicted probability of passage success between the native and exotic fish species in this study were sufficient in some cases to indicate the potential for the baffled fish ramps to operate as a selective migration barrier. Nonetheless, further testing is required to validate these results across a broader range of conditions before deployment.

Globally, many freshwater fishes are declining in distribution and abundance, but for many species conservation measures are hindered by a limited knowledge of their ecology. Recent development of 12‐mm half‐duplex (HDX) passive integrated transponder (PIT) tags has broadened the potential application of this technology for studying habitat selection and migration of freshwater fishes. However, the limited read range of the smaller 12‐mm PIT tags can limit their functionality in ecological studies. The present study used four migratory fish species to test the efficacy of different PIT antenna designs for detecting 12‐mm HDX tags in small‐ and medium‐sized rivers. Three types of pass‐through antennae were created and coupled to either a single reader or multiplexor board. Across single‐reader and multiplexor systems, the detection efficiencies for Giant Kokopu Galaxias argenteus, Shortfin Eel Anguilla australis, and New Zealand Longfin Eel Anguilla dieffenbachii ranged between 87% and 97%. Adult Pouched Lamprey Geotria australis also had a high detection rate of 74%, even though several other migration routes existed that were unmonitored. Overall, the present study shows that with appropriate antenna design, the 12‐mm HDX PIT tag can be effective for monitoring a variety of fish species. Although the antennae in the present study had a maximum width of 6.1 m, the spaced double‐coil antenna design may increase efficacy of the 12‐mm tag in larger rivers. Received April 27, 2017; accepted September 1, 2017 Published online October 30, 2017

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