Boat electrofishing survey of common smelt and common bullies in the Ohau Channel

We conducted a boat electrofishing survey of the Ohau Channel, which flows from Lake Rotorua to Lake Rotoiti, on 13 December 2007. The purpose of the survey was to investigate the longitudinal pattern in densities of common smelt (Retropinna retropinna) and common bullies (Gobiomorphus cotidianus) along the Ohau Channel. We caught 1,267 fish comprising three native fish species and two introduced fish species in 1.58 km of fished distance at a total of 10 sites. Native species caught were the common smelt, common bully and longfinned eel (Anguilla dieffenbachii) and introduced species were rainbow trout (Oncorhynchus mykiss) and goldfish (Carassius auratus). Assuming that the bow-mounted anodes effectively fished a 4 m swath then the total area fished was 6,328 m2 (0.632 ha). Common smelt densities varied among the 10 different sites in the Ohau Channel ranging from 0 to 10.6 fish 100 m-2. Smelt density was higher at the upstream end of the channel near the weir at the Lake Rotorua outlet, decreasing with increasing distance from the weir. Smelt were found in the littoral zones but were not caught in mid-channel habitats. In the upstream reaches of the Ohau Channel, directly below the weir, a high number of juveniles (4.4 fish 100 m-2) were captured compared to the amount of juveniles captured at the other sites (0 – 1.2 fish 100 m-2). Common bully densities varied among the 10 different sites in the Ohau Channel ranging from 0.2 to 58.3 fish 100 m-2. No longitudinal pattern in the distribution of common bullies was evident along the channel. The highest densities were found halfway along the Ohau Channel where there was an abundance of dense macrophyte beds. Common bully densities were found to be much higher in the edge habitats with macrophyte beds compared to the mid-channel habitats and the willow edge habitat where there were relatively low densities. Size frequency data shows that there is generally a higher proportion of small bullies than larger ones suggesting that recruitment is occurring. Both adult and juvenile rainbow trout were observed in the Ohau Channel. Most of these individuals were found in the upstream section of the channel below the weir and ranged from a 75 mm juvenile to a fully grown adult about 500 mm long. Large longfinned eels were also captured and were only found in the downstream section of the Ohau Channel in willow-dominated edges. In the bottom third section of the channel, near the possible artificial embayment, goldfish were present

Laboratory captivity can affect scores of metabolic rates and activity in wild brown trout

Phenotypic scoring of wild animals under standardized laboratory conditions is important as it allows field ecologists and evolutionary biologists to understand the development and maintenance of interindividual differences in plastic traits (e.g. behaviour and physiology). However, captivity is associated with a shift from a natural familiar environment to an unfamiliar and artificial environment, which may affect estimates of plastic phenotypic traits. In this study, we tested how previous experience with laboratory environments and time spent in captivity affects behavioural (i.e. activity) and metabolic (i.e. standard and maximum metabolic rates) scoring of our model species, wild brown trout Salmo trutta. We found that individuals with previous experience of laboratory captivity (10.5 months earlier) showed higher activity in an open field test than individuals with no prior experience of laboratory captivity. Previous experience with captivity had no significant effect on metabolic rates. However, metabolic rates seemed to increase with increasing time spent in captivity prior to the collection of measurements. Although there are benefits of keeping wild animals in captivity prior to scoring, our results suggest that while allowing for sufficient acclimatization researchers should aim at minimizing time in captivity of wild animals to increase accuracy and ecological relevance of the scoring of plastic phenotypic traits

Prevalence and severity of cardiac abnormalities and arteriosclerosis in farmed rainbow trout (Oncorhynchus mykiss)

Cardiovascular disease may pose a major threat to the health and welfare of farmed fish. By investigating a range of established cardiovascular disease indicators, we aimed to determine the prevalence, severity and consequences of this affliction in farmed rainbow trout (Oncorhynchus mykiss) from an open cage farm in the Baltic Sea, an open cage farm in a freshwater lake, and a land-based recirculating aquaculture system. We also aimed to identify environmental, anthropogenic and physiological factors contributing towards the development of the disease. The majority of trout possessed enlarged hearts with rounded ventricles (mean height:width ratios of 1.0-1.1 c.f. similar to 1.3 in wild fish) and a high degree of vessel misalignment (mean angles between the longitudinal ventricular axis and the axis of the bulbus arteriosus of 28-31 degrees c.f. similar to 23 degrees in wild fish). The prevalence and severity of coronary arteriosclerosis was also high, as 92-100% of fish from the different aquaculture facilities exhibited coronary lesions. Mean lesion incidence and severity indices were 67-95% and 3.1-3.9, respectively, which resulted in mean coronary arterial blockages of 19-32%. To evaluate the functional significance of these findings, we modelled the effects of arterial blockages on coronary blood flow and experimentally tested the effects of coronary occlusion in a sub-sample of fish. The observed coronary blockages were estimated to reduce coronary blood flow by 34-54% while experimental coronary occlusion adversely affected the electrocardiogram of trout. Across a range of environmental (water current, predation), anthropogenic (boat traffic intensity, hatchery of origin, brand of feed pellets) and physiological factors (condition factor, haematological and plasma indices), the hatchery of origin was the main factor contributing towards the observed variation in the development of cardiovascular disease. Therefore, further research on the effects of selective breeding programs and rearing strategies on the development of cardiovascular disease is needed to improve the welfare and health of farmed fish

Oxygen- and capacity-limited thermal tolerance: blurring ecology and physiology

No abstract available

Demographics of extra-articular calcaneal fractures: Including a review of the literature on treatment and outcome

Introduction: Extra-articular calcaneal fractures represent 25-40% of all calcaneal fractures and an even higher percentage of up to 60% is seen in children. A disproportionately small part of the literature on calcaneal fractures involves the extra-articular type. The aim of this study was to investigate the incidence of extra-articular calcaneal fractures in a Level 1 trauma centre, define the distribution of the various types of fractures and compare patient demographics between extra- and intra-articular calcaneal fractures. In addition the literature was reviewed for the most common types of extra-articular calcaneal fractures with regard to incidence, treatment and clinical outcome. Methods: The radiological records between 2003 and 2005 were reviewed for intra- and extra-articular calcaneal fractures. Patient gender-distribution and age were compared. A literature search was conducted for the treatment of extra-articular calcaneal fractures. Results: In this 3-year study period a total of 49 patients with 50 extra-articular calcaneal fractures and 91 patients with 101 intra-articular fractures were identified. The median age for the first group was 32.7 years, and for the second group 40.3 years; P = 0.04. Male predominance was significantly less pronounced for extra-articular (63%) compared with intra-articular fractures (79%; P = 0.04). Conclusion: One-third of all calcaneal fractures are extra-articular. Significant differences exist between the intra- and extra-articular groups, in terms of lower age and male-female ratio. The literature study shows inconsistencies in treatment options, but most extra-articular fractures are well manageable conservatively

The New Era of Physio-Logging and Their Grand Challenges.

International audienc

Boat electrofishing survey of common smelt and common bullies in the Ohau Channel in December 2008

We conducted a boat electrofishing survey of the Ohau Channel, which flows from Lake Rotorua to Lake Rotoiti, on 11 December 2008. The purpose of this was to repeat a survey that took place on 13 December 2007 concerning the longitudinal pattern in densities of common smelt (Retropinna retropinna) and common bully (Gobiomorphus cotidianus). We caught 776 fish comprising three native species and three introduced species in 2.03km of fished distance at a total of 10 sites. Native species caught were common smelt, common bully and longfin eel (Anguilla dieffenbachii) and introduced species were rainbow trout (Oncorhynchus mykiss), goldfish (Carassius auratus) and mosquitofish (Gambusia affinis). The total area fished was 8,133 m² (0.813 ha) giving an estimated density of 9.5 fish 100 m⁻²

The use of boat electrofishing for koi carp (Cyprinus carpio) control in the Kauri Point catchment.

The koi carp is an ornamental strain of the common carp (Cyprinus carpio) which is believed to be one of the most ecologically detrimental of all freshwater invasive fish species. They are widespread in the Auckland and Waikato region and appear to be spreading both north and south of these areas. The presence of koi carp in 3 ornamental ponds at Kauri Point, Katikati which is located in the western Bay of Plenty region was confirmed in late 2006. Because koi carp is designated an unwanted organism under the Biosecurity Act it was decided by the Department of Conservation (DOC) that an attempt to eradicate them from this locality would occur. One possible option for eradication of koi carp in this catchment was the use of and electric fishing boat from the University of Waikato. This boat operates by putting a pulsed DC current into the water column where it attracts and then incapacitates fish, allowing operators to remove them from the water with hand nets. The Centre for Biodiversity and Ecology Research (CBER) at the University of Waikato was contracted to attempt to eradicate koi carp from the three ponds at Kauri Point by boat-electrofishing. The objectives were (1) to survey the fish abundance, (2) to remove as mand koi as possible in an attempt for eradication and (3) to estimate the proportion of koi carp removed from the system by boat-electrofishing. On 21 and 22 April 2008, a total of 327 fish comprising of 307 koi carp (137.5 kg of biomass), 1 goldfish(Carassius auratus) and 19 koi-goldfish hybrids were captured and removed from the 3 ponds located within the Kauri Point catchment by a combination of electric fishing (307 fish) and gill netting (20 fish). The majority of these fish (299 koi, 1 goldfish, 19 koi-goldfish hybrids) were removed from the largest pond (pond A). Boat-electrofishing caught a wide size range of koi (70 mm to 510 mm) and at least four distinct size classes of koi were apparent. The high proportion of juvenile (<200 mm) caught along with reasonable numbers of mature males and females in pond A strongly suggests that breeding is occurring within the Kauri Point aquatic ecosystem. Results from analysing scales of a small sub sample of koi (n=34) also shows that there was a wide range of ages of pond A (ages 1 to 8 years old). Pond A had a relatively high density of 4.6 koi carp 100 m⁻² compared to pond B and C which had low densities of 0.5 and 0.2 koi carp 100 m⁻² respectively. No juvenile carp were observed to be present in ponds B and C. Population and total biomass estimates for koi carp in pond A prior to removal of fish were calculated to be 358±66 koi carp and 145.14 ±44.27 kg (mean ±95% C. I) respectively. 299 koi carp or 122.30 kg of biomass (71-84% of the estimated population) were removed from pond A over two days of electric fishing, leaving a possible 125 koi carp or 67.11 kg of biomass remaining in the pond. Boat-electrofishing proved to be a successful too for removing a large proportion of the estimated biomass of koi carp in the Kauri Point ponds. Eradication of koi carp by boat-electrofishing from this system was not possible due to poor water visibility (difficult to spot narcotised carp), limited time allocated and successful koi carp breeding occurring in the ponds. Viable options of koi carp eradication in the Kauri Point catchment would involve the partial draining and poisoning of the three ponds and the associated tributaries where koi carp are found