Kaituna River fish inventory NIWA Client Report: HAM2005-047 April 2005 NIWA Project: BOP04223 Kaituna River fish inventory Jacques Boubée Cindy Baker Prepared for Environment Bay of Plenty NIWA Client Report: HAM2005-047 April 2005 NIWA Project: BOP04223 National Institute of Water & Atmospheric Research Ltd Gate 10, Silverdale Road, Hamilton P O Box 11115, Hamilton, New Zealand Phone +64-7-856 7026, Fax +64-7-856 0151 www.niwa.co.nz All rights reserved. This publication may not be reproduced or copied in any form without the permission of the client. Such permission is to be given only in accordance with the terms of the client's contract with NIWA. This copyright extends to all forms of copying and any storage of material in any kind of information retrieval system. Contents 1. Introduction 1 2. Inventory 1 2.1 Existing data 1 2.2 Field surveys 1 2.3 Fish found in the upper Kaituna River 2 2.4 Fish found in the lower Kaituna River 3 Reviewed & approved for release by: D.S. Roper Formatting checked 1. Introduction This report provides an inventory of fish from the Kaituna River and its tributaries. Information has been drawn from NIWA’s Freshwater Fish Database, unpublished reports, Department of Conservation records, Mighty River Power records and recent field surveys undertaken by NIWA. The Kaituna River has two distinct sections, each representing very different habitats for fish. The upper section has high flow velocities and runs for over 27 km from Okere Falls through a deep gorge. Access into the upper section is limited and dangerous. The lower section is broader and slower flowing and meanders through flat country until reaching the sea at Maketu. The fish populations in the two river sections are quite distinct and are presented separately in this report. 2. Inventory 2.1 Existing data Information on existing fish species in the Kaituna River was extracted from the New Zealand Freshwater Fish Database (NZFFD). The NZFFD is a national, site-specific database of fish species presence/absence, and is the preferred repository for fish survey data for the majority of people undertaking freshwater fish studies in New Zealand. Unpublished results of fish surveys undertaken by the Department of Conservation and Mighty River Power were also obtained for our assessment. The information collated indicates that relatively few fish distribution studies have been undertaken within the upper section of the river and only 22 records for this river section were held in the NZFFD on 31 August 2004. 2.2 Field surveys To supplement existing records additional sampling was undertaken in 2004 and the information entered into the NZFFD. Two sites were sampled in the upper river section and three in lower section. As well as sampling in the main stem of the river surveying was also carried out in an unnamed tributary downstream of Stottle Rapids and in the Mangorewa River. Kaituna River fish inventory 1 Difficulty in accessing the upper section of the river, and the high flows encountered at survey sites, limited sampling options. As a result, sampling could only be carried out using electric fishing, minnow trapping and fyke nets. In the lower river a wider range of nets and sampling techniques could be used including electric fishing, gill nets, various fyke nets, seine nets, minnow traps. 2.3 Fish found in the upper Kaituna River Based on the review of existing information and NIWA’s field surveys, a total of ten species of fish have been found in the upper section of the Kaituna River (Table 1). Longfin eels are the most abundant fish species, penetrating well inland. The scarcity of shortfin eels may reflect a lack of habitat rather than a lack of migratory ability. No banded kokopu are present in Lakes Rotoiti or Rotorua, but sparse populations of koaro are present in some Lake Rotoiti tributaries. Banded kokopu found in this river section must therefore have migrated from the sea, but koaro could be recruits from either the lakes or the sea. No indigenous fish were found in a survey of eight tributary streams located between the upstream limit of the gorge and Okere Falls (K. Young, Department of Conservation, Rotorua, pers. comm.). Kaituna River fish inventory 2 Table 1. List of indigenous and introduced fish species present in the upper Kaituna River catchment and % occurrence in all available records (N=24 records). * = Diadromous species, although landlocked populations of koaro, common bully and smelt are also present in the headwater lakes. Scientific name Common name Percent occurrence Indigenous species Anguilla australis* Shortfin eel 8.3 Anguilla dieffenbachii* Longfin eel 45.8 Cheimarrichthys fosteri* Torrentfish 4.1 Galaxias brevipinnis* Koaro 4.2 Galaxias fasciatus* Banded kokopu 4.2 Gobiomorphus cotidianus* Common bully 30.3 Retropinna retropinna* Common smelt 8.3 Introduced species Carassius auratus Goldfish 4.2 Oncorhynchus mykiss Rainbow trout 20.8 Salmo trutta Brown trout 4.2 2.4 Fish found in the lower Kaituna River The lower Kaituna River has a wider range of habitats and supports 19 fish species; 15 indigenous and four introduced (Table 2). This diversity is equivalent to that found in neighbouring Bay of Plenty rivers. All indigenous fish are diadromous, with seven of the 15 species only present in the lower section of the river. Common bully and smelt form significant diadromous populations in the lower river, with the upper river populations comprised mainly of downstream migrants from lacustrine stocks. Longfin and shortfin eels are the most frequently recorded fish species, found at 86 % of all sampled sites within the lower river. Field surveys did not locate any new fish species, but have expanded the distribution of inanga, which were found in the mainstem as far up as The Rapids. Kaituna River fish inventory 3 Table 3.17. List of indigenous and introduced fish species present in the lower Kaituna River catchment and % occurrence in all available records (N=80 records). * = diadromous species. Scientific name Common name Percent occurrence Indigenous species Anguilla australis* Shortfin eel 41.3 Anguilla dieffenbachii* Longfin eel 45.0 Arripis trutta Kahawai 1.3 Cheimarrichthys fosteri* Torrentfish 3.4 Galaxias argenteus* Giant kokopu 5.0 Galaxias brevipinnis* Koaro 3.4 Galaxias fasciatus* Banded kokopu 6.3 Galaxias maculatus* Inanga 23.8 Geotria australis* Lamprey 3.4 Gobiomorphus cotidianus* Common bully 26.3 Gobiomorphus gobioides* Giant bully 10.0 Gobiomorphus huttoni* Redfin bully 17.5 Rhombosolea retiaria* Black flounder 1.3 Retropinna retropinna* Common smelt 27.5 Mugilidae Mullet 6.3 Introduced species Carassius auratus Goldfish 2.5 Gambusia affinis Gambusia/mosquitofish 15.0 Oncorhynchus mykiss Rainbow trout 13.8 Salmo trutta Brown trout 3.8 Kaituna River fish inventory 4 .