Diverse perspectives on the role of trout in Aotearoa New Zealand's biological heritage

Abstract

As part of Aotearoa New Zealand’s colonisation by Europeans, brown and rainbow trout were introduced about 150 years ago and are now near-ubiquitous across the country. Since their introduction, trout have had—and continue to have—both negative and positive effects on ecosystems, culture and society. Trout prey upon and compete with native fauna and have dramatically altered freshwater food webs. Often trout introductions occurred without the consent of iwi/hapū, in turn affecting Māori communities through impacts on customary native fisheries. Māori rights and interests in relation to trout have been a longstanding issue of concern in need of resolution. More recently, other members of the public have identified environmental concerns regarding the management of trout fisheries. However, trout also provide valued recreational fisheries and are economically and culturally important to pākehā and some Māori communities, while trout-based environmental rules currently protect many waterbodies across Aotearoa New Zealand. As such, trout are an introduced species with complex socio-ecological roles. This report was commissioned by the Biological Heritage National Science Challenge to better understand the range of perspectives on trout in Aotearoa New Zealand. We present qualitative data from interviews undertaken with 13 freshwater knowledge holders. Interviewees included Māori knowledge holders, salmonid fishery managers, indigenous freshwater biodiversity managers, and native fish and salmonid scientists. In semi-structured interviews, we invited interviewees to reflect on their personal connection with fresh water, what makes a freshwater ecosystem healthy’, and the positive and negative effects of trout. Interviewees were also asked to identify knowledge gaps with regards to trout, and to comment on the past, current and future management of trout in Aotearoa New Zealand. Transcripts were condensed for clarity by the project team and organised under broad themes that reflect interview questions. This report presents the condensed and thematically organised quotes with minimal interpretation, to allow the interviewees to largely speak for themselves. Diverse views were expressed by the interviewees. Some Māori interviewees recounted their experiences of the pain and injustice caused by the introduction of trout, the effects of trout on customary fisheries, and the actions of trout managers, while others talked about how trout have been incorporated into their culture as novel mahinga kai species. In some cases, reflections on the problematic aspects of trout and their management, as well as their positive values, were expressed by the same interviewee. This demonstrates the complex way trout have influenced ecosystems, communities and culture in Aotearoa New Zealand. Salmonid and native fish experts agreed on the negative impacts that trout have on rare, non-migratory native galaxiid fishes; all suggested that more needs to be done to protect these indigenous fish from trout. The degree to which trout negatively affect large river ecosystems and ocean-migratory native fish (such as whitebait) was more contentious. Perceptions that trout could potentially have positive effects on ecosystems depended on interviewees’ fundamental views of how to conceptualise healthy ecosystems—either in terms of naturalness, or by using concepts such as productivity and ecological function. For those interviewees that saw ecosystem health as not necessarily linked to naturalness, potential positive effects included trout being prey for native predators (such as tuna/eels or wetland birds) or trout suppressing the proliferation of other introduced aquatic species (e.g. gambusia/mosquito fish) through predation. Indigenous biodiversity managers and Fish & Game staff agreed that trout advocacy has been key to ensuring long-lasting protection of many freshwater habitats. The fact that many Water Conservation Orders have been the result of applications by Fish & Game was frequently commented upon. Visions of the role of trout in the future protection and enhancement of Aotearoa New Zealand’s biological heritage were more divergent. Some interviewees see trout as categorically not belonging within a healthy ecosystem. Other interviewees, including those that identify as native fish advocates, see a role for trout in regenerating Aotearoa New Zealand’s biological heritage, primarily by engendering connections between people and fresh water. Nevertheless, most see a need to better manage the negative effects that trout can have on native biodiversity, cultural values and consequently communities. Despite the diversity of views expressed, we identified recurring themes that point toward shared principles that could underpin conversations among trout advocates, conservationists, and Māori. The principles include: 1. decision making about freshwater fish should be shared with tangata whenua 2. salmonid managers should share responsibility for addressing the negative effects of trout 3. fish management agencies should coordinate to achieve shared outcomes. Across the interviews, we identified five areas for potential collaboration between trout and native fish advocates: 1. restore native fish habitat 2. remove trout where rare native species are threatened 3. designate and maintain trout-free sanctuaries 4. develop more effective trout control methods 5. develop riverscape approaches for managing trout fishery and biodiversity values.