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Predictions of invasion risk for seven non-indigenous fish species, ecological impact scores for individual species, and lake conservation rankings were linked to develop Invasion Risk Impact ( IRI) and Lake Vulnerability ( LV) indices that help identify New Zealand lakes most at risk of loss of conservation value from potential multi-species invasions., Species-specific IRI scores (the product of predicted invasion risk and species impact) highlighted Eurasian perch ( Perca fluviatilis) and the brown bullhead ( Ameiurus nebulosus), as the species most likely to spread and cause ecological harm in lakes. For 3431 lakes >1 ha throughout New Zealand, total IRI tended to be highest for lowland riverine and dune lakes most of which are already colonized by multiple invasive fish species., The LV index indicated that lakes most at risk of loss of conservation value from invasive fish impacts were predominantly (i) in the northern half of the North Island where several uncommon lake types occur, and (ii) along the west coast of the South Island where conservation value is often greater, largely because of low catchment modification., The IRI and LV indices can be used to assist with setting priorities for surveillance monitoring, advocacy, and response planning targeted at preventing the establishment of invasive fish in moderate-to-high value lakes most susceptible to ecological impacts. Both indices can be adapted to accommodate alternative impact and conservation scoring systems, providing a flexible tool for local- and national-scale assessments of lake vulnerability to fish invasion impacts., Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

To investigate the carrying capacity and factors affecting growth of rainbow trout in Lake Rotoiti, we employed a bioenergetics model to assess the influence of stocking rates, timing of releases and prey abundance on growth and prey consumption. We hypothesised that stocking rates and prey abundance would affect growth and prey consumption by influencing per-capita prey availability, and that the environmental conditions encountered by fish at the time of stocking would affect growth and consumption., Prey consumption of stocked rainbow trout was calculated with the Wisconsin bioenergetics model. We calculated growth trajectories of released trout based on data from stocked trout that were released in spring and autumn from 1993 to 2009 and then re-captured by anglers. Diet, prey energy density, body mass lost during spawning and lake temperature were measured locally., Stocking timing had no effect on return rates to anglers or length or weight of caught fish. Although trout released in autumn were smaller than those released in spring, autumn-released trout grew at a faster rate and had similar lengths and weights to spring cohorts after 2 years of growth in the lake. Modelled consumption parameters were negatively correlated with trout population size, suggesting that stocking rates (347-809 fish ha−1 year−1) caused density-dependent effects on growth. Although common smelt ( Retropinna retropinna) accounted for 85% of total prey consumption, no significant relationship was found between prey consumption by individual trout and adult smelt abundance, possibly because trout are targeting smaller smelt that our abundance estimate did not account for., Releasing trout in autumn appears to be advantageous for growth, possibly because (i) temperature is more suitable for growth in autumn-winter than in spring-summer and (ii) prey for small trout is abundant in autumn. Mild winter conditions appear to enhance overwinter survival and growth of rainbow trout in warm-temperate lakes compared to higher latitudes. This implies that moderately productive warm-temperate lake ecosystems are highly suitable for trout growth in winter, but less so in summer, when lake stratification and high nutrient levels may create conditions suitable for algal blooms and hypolimnetic deoxygenation. High growth rates of trout in warm-temperate lakes can therefore be supported by timing releases to coincide with favourable winter conditions. [ABSTRACT FROM AUTHOR]

1. The dwarf inanga Galaxias gracilis is restricted to 13 dune lakesalong an 80 km length of coastline on the west coast of the North Island, New Zealand, and its abundance has declined in at least eight of these lakes. It is therefore a rare and endangered endemic species.2. A range of environmental variables were compared between lakes where it is still common and lakes where it is now rare to identify variables associated with its low abundance. 3. Lakes where dwarf inangawere rare all had a lower pH, lower concentrations of calcium, magnesium and silica, and higher concentrations of chloride than lakes where dwarf inanga were common. In addition, they contained different charophyte plant species, as well as stocked populations of eels and/orintroduced exotic fish species capable of preying on one or more of the life stages of dwarf inanga. 4. Factors not associated with the low abundance of dwarf inanga included lake size and depth, land use in the catchment, lake level fluctuations, the extent of emergent vegetation, littoral zone substrate composition, and water quality parameters including maximum water temperature, water transparency, and minimum oxygen levels in the hypolimnion. 5. The identification of factors associated with the low abundance of dwarf inanga has allowed testable hypotheses to be developed to account for its decline in certainlakes. However, biological data, particularly on the location of spawning grounds and on the feeding requirements of larvae, are requiredbefore all these hypotheses can be tested. 6. The results have formed the basis for a management plan for the conservation of this species, in which whole-lake experiments are being carried out to identify the effects of introduced plants and fish on its population size. [ABSTRACT FROM AUTHOR]