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Adaptive management requires the merger of management with science to provide robust knowledge about the effect of management actions. It can also be applied as a model of collaborative learning to support effective resource management. Using the example of adaptive management of native forests affected by introduced deer in New Zealand, we set out to identify some of the tensions that become apparent when adaptive management is applied in this way. We describe the process of adaptive management as it was applied in this case study. Drawing from project documentation and participant reflections on the learning process, we highlight three key lessons: (1) the need to create 'space' - i.e. a permissive environment that allows for an evolving process rather than a formalised and legalistic one; (2) that adaptive management cannot be expected to progress in a standardised way but instead, role clarity will emerge over time and this will contribute to an emerging vision of contribution that participants see for their project; and (3) the collaborative learning component of adaptive management poses a new challenge for science as rather than providing solutions to management issues, scientists contribute technical expertise and methods as part of the management

Context When environmental, economic and/or social effects of wildlife are considered undesirable and need to be reduced, managers require knowledge of the effectiveness of candidate control techniques, particularly the relationship between control effort and change in abundance. Aims We evaluated the effects of control on the abundances of introduced red deer (Cervus elaphus scoticus) and sika deer (Cervus nippon) at three New Zealand forest sites (two North Island, one South Island) in an 8-year adaptive-management experiment. Methods We identified paired areas of 3600 ha at each site that were as similar as possible in geology, physical environments and forest composition and applied deer control (helicopter- and/or ground-based hunting) to a randomly selected member of each pair. The abundances of deer were monitored in each treatment and non-treatment area for up to 7 years by using faecal pellet counts on 50 randomly located transects. Key results The difference between deer abundances in the treatment and non-treatment areas was significantly negative at one site, significantly positive at one site and indistinguishable at the other site. Faecal pellet abundances declined with increasing helicopter-based hunting effort but did not change with increasing ground-based hunting effort. There was evidence that aerially sown 1080 baits used for possum control in two treatment areas reduced deer abundances. Conclusions The substantial uncertainty surrounding the relationships between deer control effort and changes in deer abundance means that managers cannot assume that the environmental, economic and/or social problems caused by deer will be alleviated with the quantum of control effort applied in the present study. Implications Reducing the abundances of deer in forests may require substantially more control effort than is currently believed.

Recovery of threatened species is often necessarily a long-term process. The present paper details the progress towards the recovery of trout cod, Maccullochella macquariensis, an iconic, long-lived fish species first listed as threatened in the 1980s. The objectives, actions and progress over three successive national recovery plans (spanning 18 years) are assessed, documenting changes to population distribution and abundance and updating ecological knowledge. Increased knowledge (especially breeding biology and hatchery techniques, movements, habitats and genetics) has greatly influenced recovery actions and the use of a population model was developed to assist with management options and stocking regimes. Key recovery actions include stocking of hatchery-produced fish to establish new populations, regulations on angling (including closures), education (particularly identification from the closely related Murray cod, M. peelii) and habitat rehabilitation (especially re-instatement of structural woody habitats). In particular, the establishment of new populations using hatchery stocking has been a successful action. The importance of a coordinated long-term approach is emphasised and, although there is uncertainty in ongoing resourcing of the recovery program, much has been achieved and there is cautious optimism for the future of this species.

Internationally, re-introductions of endangered species into their former ranges have largely failed. Here we assess a successful reintroduction program of the endangered trout cod (Maccullochella macquariensis) and examine factors contributing to this success. Stocking of marked fish (all stocked fish were marked) occurred between 1997 and 2006 in the Ovens River, south-eastern Australia, where trout cod were historically abundant but locally extinct by the 1980s. We found no natural recruits (i.e. from spawnings of stocked fish in the wild) over the age of six, indicating that natural recruitment started at most five years after stocking began. Of the 83 fish we examined for sexual maturity, 12 were immature, 20 were male, and 51 were female. The body length at which 50% of the population can be considered mature was 325 and 250 mm for females and males, respectively. The length at which 90% of the population was mature was 394 and 318 mm for females and males, respectively. The smallest mature female was 245 mm. Average relative fertility was 9 eggs g–1 fish weight. The results we obtained provide valuable insights into the aspects contributing to the success of reintroduction programs for endangered freshwater species.

I agree with several of the points made by Regan and Colyvan (this issue), but they have made important errors in their reading of the proposal by me and my coauthor Burgman (Todd & Burgman 1998). Regan and Colyvan raise two issues. The first is that we obtain fuzzy membership functions from probabilities and that this is not correct ("demonstrably fallacious," in their language). The second is that this excursion is not necessary. I deal with the issues raised in order. Regan and Colyvan correctly highlight some of the differences between probabilities and fuzzy memberships. In fact, we did the same thing in our discussion. But there is nothing new in this criticism of probabilities being used for fuzzy membership functions (for a survey see Hisdal [1988]). Kandel and Byatt (1978) point out that there "is a view of probability that frankly admits a subjective component ... there is an element of human judgement even in the seemingly most objective procedures for determining quantitative probabilities." Many if not most data sets will have elements of subjectivity; this is particularly so in many areas of data collecting for conservation biology. Turksen (1988) states that a fuzzy measure interpreted as a subjective measure expresses the fuzzy membership function, that probabilities can equal fuzzy membership functions as stated in our proposal. Regan and Colyvan provide a contradictory view. They should have directed their critique at the method provided by Turksen (1988) and how that may or may not apply in Todd and Burgman (1998) and explored the consequences of their view for the whole field of study supported by Turksen's (1988) work. As a consequence of some admittedly poor wording by Todd and Burgman (especially regarding the reference to Bosserman and Ragade [1982]), their criticism misses the point. We assume that subjective probabilities will be used to describe fuzzy membership, in the sense that the probability distributions will be used as a model for constructing fuzzy membership functions. Our proposed approach is not necessarily wedded to the equality alluded to by Regan and Colyvan. I agree with Regan and Colyvan that the categories of Millsap et al. (1990) are (arbitrarily) sharp. The case would have been better made if we had omitted the words "believed to have a. ..," as in the original manuscript. Regan and Colyvan appear to have misread our proposal with regard to the point they make that the machinery of fuzzy set theory is unnecessary. The proposal accounts for information provided as expert opinion rather than as measured variation. It suggests a means by which information of this kind might be combined with information given as probability distributions, together with point data. Regan and Colyvan do not acknowledge this. The whole point of the proposal was to present a coherent method by which to deal with different types of information without changing the original criteria so that biologists and policymakers could use the method without having to come to terms with a new set of criteria. Regan and Colyvan state that a number of fuzzy settheoretic operators are available and that they need to be selected carefully. Their criticism of our proposal seems unjustified because we (1998) made the same point (pp. 971-972). We provided "[t]wo examples that have some intuitive appeal for risk assessment" (emphasis added). We did not claim that the algebraic product and sum have more appeal than the standard min and max operators. Rather, they were mentioned simply as examples worthy of investigation. Moreover, Regan and Colyvan are dismissive of the standard approach (the min and max operators) and concentrate on the algebraic product and sum (an example of other types of operators) as though this were the only one we proposed. The algebraic product was used simply to show that, depending on the operator used, different membership values may be achieved. In their criticism of the use of the algebraic product, Regan and Colyvan failed to acknowledge that it does not matter which operator is used; the rank order of fuzzy sets (largest degree of membership to smallest) remains the same. Paper submitted February 11, 2000; revised manuscript accepted March 15, 2000.