A total of 566 koi carp (Cyprinus carpio) from the lower Waikato region were aged from scales and opercular bones, and growth was modelled with the von Bertalanffy growth function. There was no difference in growth rate between male and female carp. Growth of koi carp between zero and 3 years of age was lower than that of common carp in europe and Australia. however, after 5 years of age the growth of koi carp was higher than that of common carp in europe, but still below that of carp in Australia. males rarely lived in excess of 8 years, whereas females lived to 12 years. mean total fecundity calculated from 44 running-ripe females was 299 000 oocytes (±195 600 sd) (range 29 800-771 000). relative fecundity ranged from 19 300 to 216 000 oocytes kg-1 total body weight, with a mean of 97 200 (±35 000 sd) oocytes kg-1. Feral koi carp in the Waikato are capable of multiple spawnings within their lifetimes. Within a spawning season, Waikato populations of feral koi carp contained females that spawned once, and females that had the potential to have spawned repeatedly. Female gonadosomatic index (Gsi) varied with season and was negatively related to water temperature.

Koi carp is an ornamental variant of the common carp, Cyprinus carpio L., that was introduced to New Zealand in the 1960s and has since become a major aquatic pest. A total of 1265 wild adult koi carp were caught by boat electric fishing, dart tagged and released at multiple sites in the lower Waikato River and associated lakes and wetlands between September 2002 and February 2005. Subsequent recaptures by boat electric fishing and recreational fishing returned 76 koi carp (6% of all tagged fish). Of these, 85% were recaptured less than 5 km from their release site; only one fish moved more than 50 km. On seven occasions, pairs or small groups of koi carp (20% of all tag returns) that had previously been tagged and released at the same locations and times were subsequently recaptured together after considerable periods of time at liberty (mean 551 days ± 419 SD). Adult koi carp in the Waikato River showed a high degree of site fidelity, exhibited prolonged social groupings and females moved downstream more often than males.

No abstract

Poor larval survival is a bottleneck to commercial hatchery production of the tropical black-lip rock oyster, Saccostrea echinata. This study investigated the synergistic effects of water temperature and salinity on embryonic and larval development across each major larval life stage. Results showed that water temperature and salinity have a significant effect on embryonic development of S. echinata and that embryos did not develop below 17 °C and 14 psu. Survival was high (55-100%) across all treatments and larval stages, and shell size was used primarily to determine larval response to treatments. Larval shell size increased as water temperature and salinity increased, reaching optima at 32 °C and 23 psu for D-veligers (mean DVM 78.18± 0.85 μm), at 32 °C and 26 psu for umbonate larvae (mean DVM 183.40 ± 2.60 μm), and at 32 °C and 29 psu for eyed larvae (mean DVM 249.64± 3.22 μm). It is recommended that S. echinata embryos and larvae are cultured within 28-32 °C and at salinity optima for each larval stage: embryo development at 32 psu, D-veligers and umbonate larvae between 23 and 26 psu, and eyed larvae between 28 and 30 psu. This is the first investigation of the combined effects of water temperature and salinity on S. echinata and provides valuable information to accelerate commercial aquaculture of this tropical species.