http://waikato.researchgateway.ac.nz/ Research Commons at the University of Waikato Copyright Statement: The digital copy of this thesis is protected by the Copyright Act 1994 (New Zealand). The thesis may be consulted by you, provided you comply with the provisions of the Act and the following conditions of use: Any use you make of these documents or images must be for research or private study purposes only, and you may not make them available to any other person. Authors control the copyright of their thesis. You will recognise the author’s right to be identified as the author of the thesis, and due acknowledgement will be made to the author where appropriate. You will obtain the author’s permission before publishing any material from the thesis. Responses of wild freshwater fish to anthropogenic stressors in the Waikato River of New Zealand A thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy at The University of Waikato by David W. West Department of Biological Sciences The University of Waikato Hamilton, New Zealand 2007 Abstract To assess anthropogenic impacts of point-source and diffuse discharges on fish populations of the Waikato River, compare responses to different discharges and identify potential sentinel fish species, we sampled wild populations of brown bullhead catfish (Ameiurus nebulosus, (LeSueur, 1819)), shortfin eel (Anguilla australis Richardson, 1848), and common bully (Gobiomorphus cotidianus McDowall, 1975) in the Waikato River. Sites upstream and downstream of: geothermal; bleached kraft mill effluent (BKME); sewage and thermal point-source discharges were sampled. At each site, the population parameters, relative abundance, age structure and individual indices such as: condition factor; and organ (gonad, liver, and spleen) somatic weight ratios; and number and size of follicles per female were assessed. Indicators of fish residence and in some cases exposure to contaminants in discharges were analyzed. Bile chemistry of brown bullhead and shortfin eel was assayed, liver and muscle metal levels were analyzed for brown bullhead and shortfin eel respectively, and stable isotopes of C and N in common bully were measured. Bile, metal and isotopic signatures gave strong evidence that fish had been resident at sites for some time before sampling. Signatures of bile and metal contaminants showed contamination was localised to discharge areas. Gradients in stable isotopes in common bully showed evidence of changes in water sources and anthropogenic effects along the river. Biochemical variables, hepatic ethoxyresorufin-O-deethylase (EROD) and plasma steroids indicated exposure and response of brown bullhead and shortfin eel to pulp and paper contaminants at the BKME site. Physiological (blood) variables showed fish largely responded in a predictable way to elevated water temperatures at discharge sites at time of sampling, however total haemoglobin of brown bullhead and common bully blood failed to increase at the BKME site despite elevated temperatures and low dissolved oxygen. Growth rates, condition factor, age structure, and gonadosomatic index (GSI) suggest that discharges with significant heat or nutrients benefit brown bullhead despite physiological impairment at the BKME site. Shortfin eel individuals also benefited from heated water discharges. No consistent impacts on common bully health were obvious at individual discharge sites, or cumulatively along the river due to the gradual deterioration in water quality downstream. Common bully individuals also i benefited from heat in discharges but lack of juveniles at sites where numerous juvenile brown bullhead were found, suggest that unlike brown bullhead populations, common bully populations were not responding with significant recruitment. Although I found little evidence of toxic effects of discharges on shortfin eel, caution is required in assessing the potential of contaminants to impact eel populations due to the life history of shortfin eel, and exploited nature of populations. For example, reproductive damage suffered by adult eels may not immediately manifest itself in the effected population due to temporal delays in gonadal maturation, and recruitment, and single panmictic populations supplementing recruitment of impacted populations. Distinct changes in population parameters at each of the paired sites and changes in individual variables showed that fish responded to discharges. The range of responses in species suggests different sensitivity to contaminants and amount of benefit which each species receives from heat in discharges. In these terms shortfin eel would be the most resistant, then brown bullhead and lastly common bully. Interpretation of population-level impacts at the geothermal and BKME discharge sites is made difficult due to benefits of additional heat. There is also the possibility that detection of sub-lethal or chronic effects on sensitive juvenile life-stages may be being hidden by compensatory density population responses. Responses and life history of common bully made them the preferred indicator species of the three species sampled, and supported overseas examples using small-bodied fish species as sentinels. ii Acknowledgements This project would not have been possible without the supervision of Drs Brendan Hicks, Nicholas Ling and Michael van den Heuvel. The timely advice and encouragement of Drs Louis Tremblay and Kelly Munkittrick was also much appreciated. Dr Nick Kim from the Waikato regional Council provided advice and funding for the analysis of metal levels in brown bullhead livers and shortfin eel muscle and metal dynamics in the Waikato River. Ultimately it was Dr Michael van den Heuvel who inspired me to return to academia, work all night when needed and endeavour to be a real scientist. I was privileged to have such a range of skills to call upon. Thanks to Dudley Bell, Gavin Reynolds, Alex Ring, Lee Laborie and fellow CBER students from the University of Waikato for help with catching and processing fish. A special thanks to Matt Osborne, Alton Perrie and Grant Tempero whose enthusiastic help during night seining and fish processing was invaluable. I appreciated my fellow PhD student’s empathy in the final weeks of write up. Dr Barry O’Brien helped make me make the most of the University of Waikato’s world class imaging suite, without which much of the blood and fecundity analysis would not have been possible. Megan Finley, Sean Taylor and Murray Smith from Scion helped catch fish and carried out analyses. Dr Cara Lowe helped prepare isotope samples and provided an objective aging of Lake Taupo common bully. Thank you to my ex-colleagues at the National Institute of Water and Atmospheric Research (NIWA) and Department of Conservation who gave me salient advice at the start of this project and lent support and equipment during its progress. Shortfin eel otoliths were expertly aged by Dr Don Jellyman and Greg Kelly of NIWA Christchurch. Thanks to staff of Waikato Raupatu Lands Trust (especially Tim Manukau, Julian Williams and Norm Hill). Ideas and support of Environment Waikato (EW) staff especially David Speirs and Paul Smith was much appreciated. Dr Kevin Collier provided insightful comments on drafts of the brown bullhead and shortfin eel manuscripts. Funding from EW, Carter Holt Harvey Kinleith Mill, the Ministry for the iii Environment’s Sustainable Management Fund, the Foundation for Research Science and Technology and Scion (formerly Forest Research) made fulltime study possible. Food, lodgings and support of my parents and parents in law made field and lab work especially in and around Rotorua possible. Lastly I thank my wife Frances and daughters Hannah and Rebecca whose unqualified love and support have allowed me to pursue a passion that has not always made their lives easier. iv Table of Contents Abstract i Acknowledgements iii Table of Contents v List of Figures vii List of Tables viii List of Plates x Chapter One: General Introduction 1 1.0 Introduction and study design 1 1.0.1 Selection of species 2 1.0.2 Reference sites 3 1.0.3 Timing of sampling 3 1.0.4 Sample size 4 1.0.5 Sampling level 4 1.1 History of fish health assessment in New Zealand 9 1.2 Study site 11 1.2.1 Sampling sites 14 Chapter Two: Methods 18 2.0 Site selection 18 2.1 Environmental variables 18 2.2 Capture 19 2.2.1 Brown bullhead 19 2.2.2 Shortfin eel 19 2.2.3 Common bully 19 2.3 Fish processing 20 2.3.1 Necropsy 20 2.3.2 Reproductive endpoints 21 2.3.3 Aging 21 2.4 Tissue contaminant analysis 23 2.5 Biochemical and blood measurements 24 2.6 Statistical analysis 25 Chapter Three: Cumulative impacts assessment along the Waikato River, using brown bullhead catfish (Ameiurus nebulosus) populations 29 3.0 Abstract 29 3.1 Introduction 30 3.2 Results 32 3.2.1 Site physicochemical characteristics 32 3.2.2 Chemical and biochemical indicators of exposure to contaminants 32 3.2.3 Blood variables 35 3.2.4 Catch rates 37 3.2.5 Length frequency, age and growth 37 3.2.6 Condition factor, liver somatic index (LSI) and spleen somatic index (SSI) 41 3.2.7 Gonadosomatic index (GSI), fecundity and follicle size and plasma sex steroids 41 v 3.2.8 Summary of population parameters 45 3.3 Discussion 46 Chapter Four: Impact assessment along a large river, using shortfin eel (Anguilla australis) populations 52 4.0 Abstract 52 4.1 Introduction 53 4.2 Results 55 4.2.1 Site physicochemical characteristics 55 4.2.2 Chemical and biochemical indicators of exposure to contaminants 55 4.2.3 Blood