Physical and chemical attributes affecting survival and collection of freshwater mahinga kai species

Abstract

Mahinga kai is one of a number of significant Māori values identified within the National Objectives Framework (NOF) for freshwater management. The Ngā Tohu o Te Taiao (NToTT) project aimed to develop knowledge, tools and processes for setting freshwater limits for mahinga kai within the NOF. Māori have raised issues and concerns about mahinga kai species due to: (i) declines in abundance, size and quality; and (ii) potential contamination from anthropogenic activities. This review provides information about the contaminants and environmental stressors likely to be affecting some important freshwater mahinga kai, with a focus on tuna (eel), īnanga (whitebait), kākahi (freshwater mussel), kōura (freshwater crayfish) and wātakirihi (watercress). In this report, we provide guidance on how to relate existing guidelines and regulations to freshwater invertebrate and fish species traditionally used for food gathering. The guidance covered includes: (i) the ANZECC (2000) water quality guidelines for physical and chemical attributes of aquatic life, which are in the process of being updated; (ii) selected international water quality guidelines (e.g., USEPA, Environment Canada, OECD) which can be used to support and supplement ANZECC water quality guidelines; (iii) human health information for collection and consumption of aquatic foods; and (iv) the National Policy Statement for Freshwater Management (NPS-FM) and the NOF (which is also under further development). It is envisaged this report will support discussion on food abundance and safety of mahinga kai, and promote steps to ensure appropriate standards are set for clean waterways and customary resources under the NPS-FM and ANZECC (2000). We highlight the complexity of issues affecting abundance and suitability of five commonly-used mahinga kai species: tuna, īnanga, kōura, kākahi and wātakirihi. Information from this report should also be of use in future freshwater habitat and species restoration projects, especially where mahinga kai species are at risk and the goal is to maintain or enhance customary resource use, and species state and condition.