A new species of mudfish, Neochanna (Teleostei: Galaxidae), from northern New Zealand

A new species of mudfish, Neochanna, is described from Northland. Neochanna heleios n.sp. is known from only three ephemeral wetland sites on the Kerikeri volcanic plateau and is abundant only at the type locality. The new species has a head resembling that of the brown mudfish, Neochanna apoda, and a caudal region resembling that of the black mudfish, Neochanna diversus. It can be distinguished from all Neochanna species in having a reduced number of principal caudal fin rays (13 or less). Morphometric and meristic comparisons with N. apoda and N. diversus are provided

Flow cytometric characterization of freshwater crayfish hemocytes for the examination of physiological status in wild and captive animals

Enumeration of invertebrate hemocytes is a potentially powerful tool for the determination of physiological effects of extrinsic stressors, such as hypoxia, disease, and toxicant exposure. A detailed flow cytometric method of broad application was developed for the objective characterization and enumeration of the hemocytes of New Zealand freshwater crayfish Paranephrops planifrons for the purpose of physiological health assessment. Hemocyte populations were isolated by flow cytometric sorting based on differential light scatter properties followed by morphological characterization via light microscopy and software image analysis. Cells were identified as hyaline, semigranular, and granular hemocytes based on established invertebrate hemocyte classification. A characteristic decrease in nuclear size, an increase in granularity between the hyaline and granular cells, and the eccentric location of nuclei in granular cells were also observed. The granulocyte subpopulations were observed to possess varying degrees of granularity. The developed methodology was used to perform total and differential hemocyte counts from three lake populations and between wild and captive crayfish specimens. Differences in total and differential hemocyte counts were not observed among the wild populations. However, specimens held in captivity for 14 d exhibited a significant 63% reduction in total hemocyte count, whereas the relative hemocyte proportions remained the same. These results demonstrate the utility of this method for the investigation of subacute stressor effects in selected decapod crustaceans

Human Pancreas GH-Releasing Factor Analog Restores High-Amplitude GH Pulses in CNS Lesion-Induced GH Deficiency

Lesions of the ventromedial-arcuate (VMH-ARC) region of the hypothalamus result in impaired growth accompanied by a marked suppression in spontaneous GH secretory bursts. We studied the effects of an analog of the recently characterized human pancreas GH-releasing factor hpGRF (1-40) on GH secretory dynamics in freely moving chronically cannulated rats bearing electrolytic lesions of the VMH-ARC. Intravenous administration of the hpGRF analog (hpGRFa) caused a dramatic surge of GH within 5 min; plasma GH levels rose to values as high as 2900 ng/ml and remained significantly elevated for 15-30 min post treatment. The simultaneous iv administration of somatostatin-14 and hpGRFa resulted in a significant inhibition of the hpGRFa-induced GH release at 5 min but not at 15 min. These results clearly demonstrate that impaired GH secretion resulting from VMH-ARC lesions can be restored by hpGRF. The findings are promising in that hpGRF and its analogs may provide valuable agents for the diagnosis and treatment of disorders of growth secondary to CNS dysfunction

Ecology of common bully (Gobiomorphus cotidianus) in the Tarawera and Rangitaiki rivers: isolation by inland distance or anthropogenic discharge?

Previous research has identified distinct genetic, life-history and reproductive differences between populations of common bully (Gobiomorphus cotidianus) upstream and downstream of a pulp and paper mill outfall on the Tarawera River in the Bay of Plenty, New Zealand. This study investigated the distribution of common bully in the Tarawera River by examining fish collected from upstream (37 km inland) and downstream (20 km inland) locations and comparing them to fish from similar inland locations (40 km and 17 km inland, respectively) in the nearby Rangitaiki River. Reproductive divergence was observed between upstream and downstream sites of both rivers by differing annual trends in gonadosomatic index. Stable carbon and nitrogen isotopes confirmed residency at each sampling site and otolith microchemistry demonstrated different life-history strategies between upstream and downstream populations. Diadromous recruits dominated in both downstream river populations, with a general disappearance of diadromy upstream. A mixture of diadromous and non-diadromous fish were found in the upstream Rangitaiki River, whereas diadromous recruits were absent in the upstream Tarawera River. A reduction in oculoscapular canal structures also coincided with loss of diadromy in fish from both rivers. A behavioural study to determine whether pulp and paper mill effluent may deter fish migration within the Tarawera River demonstrated a strong avoidance of effluent, but only at concentrations (>25%) greater than those that naturally occur in the river (<15%). The results of this study suggest that combinations of influences coupled with inland distance are likely to be responsible for the isolation of common bully subpopulations within the Tarawera River

Short Communication: Effects of temperature and chemical formulation on the acute toxicity of pentachlorophenol to Simocephalus vetulus (Schoedler, 1858) (Crustacea: Cladocera)

The influence of temperature on the acute toxicity of a technical formulation (86%) and pure formulation (99%) of pentachlorophenol (PCP) to less than 24-h-old Simocephalus vetulus neonates was determined with 48-h static toxicity tests. The technical grade PCP was significantly more toxic to S. vetulus than the pure PCP (P < 0.05). Sensitivity of S. vetulus to technical PCP also significantly increased with temperature (P < 0.05), but a significant temperature effect was not found with the pure PCP. The mean 48-h LC50 values for neonates exposed to technical PCP were 140 and 199 ug l⁻¹ at 22deg.C and 16deg.C, respectively, and for those exposed to pure PCP were 262 and 304 ug l⁻¹, respectively

Quantitative estimates of fish abundance from boat electrofishing

Multiple removals by boat electro-fishing were used to estimate fish populations in non-wadeable habitats in New Zealand lakes and rivers. Mean capture probability was 0.47±h0.10 (± 95% CI) from 35 population estimates made with 2-7 successive removals. The relationship between the population estimate from the Zippin method (Y)and the number of fish caught in the first removal (X) was significant (adjusted r2=0.84, P<0.001; Figure 2). The least-squares regression was Y = 1.55X 1.23. Mean density ± 95% confidence interval for 13 fishing occasions was 30±27 fish 100 m- 2. Mean biomass of fish for sites was 78±39 g m-2 (range 29 to 245 g m-2). Koi carp comprised the largest proportion of the fish biomass wherever they were present. The high biomasses of koi carp estimated in these results (mean 56±33 g m-2) suggest that they can reach problematic abundances in New Zealand. Bioniass of spawning koi carp can exceed 400 g m-2

Diet of rainbow trout in Lake Rotoiti: an energetic perspective

We characterised seasonal and ontogenetic changes in diet and prey energy density of rainbow trout (Oncorhynchus mykiss) in Lake Rotoiti, New Zealand, to better understand the prey requirements of trout in central North Island lakes. Common smelt (Retropinna retropinna) was the dominant prey item of rainbow trout larger than 200 mm (77.8% of diet by weight), followed by kōura (freshwater crayfish Paranephrops planifrons; 6.3%), common bully (Gobiomorphus cotidianus; 5.5%), and kōaro (Galaxias brevipinnis; 3.4%). Juvenile rainbow trout (<200 mm) consumed amphipods, aquatic and terrestrial insects, oligochaetes, tanaid shrimps, and smelt. Trout consumed kōaro only in autumn and winter; consumption of other species did not vary seasonally. The maximum size of smelt consumed increased with increasing trout size, but trout continued to consume small smelt even as large adults. Consumption of larger prey items (kōaro and kōura) also increased with increasing trout size. This study indicates the importance of smelt for sustaining rainbow trout populations, as predation on other species was relatively low. These findings provide a basis for bioenergetic modelling of rainbow trout populations in lakes of the central North Island of New Zealand

Age composition, growth, and reproduction of koi carp (Cyprinus carpio L.) in the lower Waikato, New Zealand

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