Adam Joshua Daniel

Movements of Radio- and Acoustic-Tagged Adult Koi Carp in the Waikato River, New Zealand

Abstract The movement of koi, a highly colored variant of common carp Cyprinus carpio, was monitored for 18 months in the Waikato River, New Zealand, with both radiotelemetry and acoustic telemetry. Koi had large total linear ranges (mean, 39 km), and most fish (74%) monitored for more than 250 d traveled between the Waikato River and lateral habitat. Differences in total linear range and mean daily movement between years suggest a behavioral response associated with reduced habitat availability during periods of low flow. The movements of koi were highly variable and infrequent, suggesting that important long-range movements are missed in short-term studies (<250 d), resulting in underestimations of total linear range. Our data suggest that large numbers of koi could have been intercepted traveling between lateral habitat and the Waikato River during 1 of 2 years, indicating that point source removal would be highly effective. Received June 12, 2009; accepted January 20, 2011

Acoustic and radio-transmitter retention in common carp (Cyprinus carpio) in New Zealand

Common carp (Cyprinus carpio) are notoriously difficult to monitor in water temperatures above 20°C using telemetry owing to transmitter expulsion. To reduce transmitter loss, radio transmitters were anchored to the pelvic girdle and a polymer coating was applied to acoustic transmitters to reduce tissue irritation in two tank trials. Ten dummy transmitters were surgically implanted in each of four groups of adult koi carp, a highly coloured strain of C. carpio. Water temperatures ranged between 7 and 24°C. After 365 days, the control and test groups of each trial had similar expulsion rates (P ≥ 0.30; two-tailed Fisher’s exact probability test). Expulsion rates for uncoated acoustic transmitters were 60% (n = 6), coated acoustic transmitters 50% (n = 5), unanchored radio transmitters 60% (n = 6) and anchored radio transmitters 90% (n = 9). Expulsions occurred 15–362 days after implantation as a result of ulcers at or near the surgical wound. Bacterial infection of the wound appears to be the primary mechanism for transmitter expulsion.

Abundance of larval native and nonnative fishes in floodplain habitats of the lower Waikato River, New Zealand

Abstract The floodplains of many large rivers worldwide are important spawning and nursery habitats for multiple fish species. We investigated the potential importance of different floodplain habitats for fish larvae. Samples were collected from 14 sites along the Waikato River, northern New Zealand, from September to October 2010. Larval fishes were identified using traditional morphological identification and DNA analyses. Our results revealed high densities of invasive koi carp and goldfish larvae in flooded terrestrial habitats compared to other habitat types. Species richness was highest in the wetland habitat. Redundancy analysis revealed that koi carp and goldfish abundances were strongly positively correlated with chlorophyll a concentrations and zooplankton densities. Floodplain habitats seem to be important habitat for larvae of both native and introduced fish species in the lower Waikato River. Because introduced larval fish out-numbered native fishes in floodplain habitats managers should consider implementing measures that at key times provide controlled access to floodplain habitats for native species and also limit access of introduced fishes.