Error! No text of specified style in document. Winter 2007 Fish Death Events: Impact on stocked fish Report prepared for the Department of Primary Industries by Infofish Services Bill Sawynok, Wendi Parsons and John Platten Infofish Services PO Box 9793 Frenchville Qld 4701 Published August 2008 Cover: Cover design by All-Biz-Art Information in this publication is provided as general advice only. For application to specific circumstances, professional advice should be sought. Infofish Services have taken all steps to ensure the information contained in this publication is accurate at the time of publication. Readers should ensure that they make the appropriate enquiries to determine whether new information is available on a particular subject matter. Report No: STSG-2008-20 Infofish Services All rights reserved. No part of this publication may be reprinted, reproduced, stored in a retrieval system or transmitted, in any form or by any means, without prior permission from Infofish Services. page 2 Table of Contents Acknowledgements..........................................................................................................................................4 1. Summary.........................................................................................................................................................5 1. Introduction.................................................................................................................................................7 2. Aims.....................................................................................................................................................................7 3. Fish Death Events in Stocked Impoundments in Geographic Divisions......................................................................................................................................................................8 3. Weather Conditions in Winter 2007 .................................................................................10 2. Temperature Tolerance of Stocked Species .............................................................14 3. Impact of Fish Death Events on the Stocking Program................................15 4. Implications for Future Stocking.........................................................................................16 5. Gulf of Carpentaria Division......................................................................................................18 6. North Queensland Division........................................................................................................26 7. Central Queensland Division....................................................................................................33 8. Mary/Burnett Division....................................................................................................................48 9. South East Queensland Division...........................................................................................59 List of Figures Figure 1: Geographic divisions based on catchments where stocking has occurred 8 Figure 2: Locations where fish deaths occurred in winter 2007 9 Figure 3: Minimum air temperatures at Mount Isa in July and August 2007 10 Figure 4: Minimum air temperatures at Atherton in July and August 2007 11 Figure 5: Minimum air temperatures at Emerald in July and August 2007 11 Figure 6: Minimum air temperatures at Maryborough in July and August 2007 12 Figure 7: Minimum air temperatures at Amberley in July and August 2007 13 Figure 8: Comparison of long term average minimum temperatures with monthly minimums for July and August 2007 13 Figure 9: Part of the Barramundi that died in Lake Moondarra (Photograph courtesy of Mount Isa Fish Stocking Association) 21 Figure 10: Barramundi sizes in Moura Weir fish death event showing fish from different stockings 38 Figure 11: Dead fish (mostly Bony Bream) and floating scum in Moura Weir (photograph courtesy of SunWater Biloela) 38 Figure 12: Fish death event in Lake Callide (Photographs courtesy of John Barber SunWater Biloela) 45 Figure 13: Dead Barramundi at Lake Lenthall (Paul Dolan photographs) 53 Figure 14: Dead Barramundi in the Burnett River downstream from Gayndah (Photograph courtesy of EPA Marybough) 55 Figure 15: Close up of dead Barramundi in Burnett River (photograph courtesy of EPA Maryborough) 56 List of Tables Table 1: Estimate of total fish deaths in each geographic division ......................................... 16 Table 2: Summary of dead fish in impoundments in Gulf of Carpentaria Division .................... 18 Table 3: Summary of dead fish in impoundments in the North Queensland Division ................ 26 Table 4: Summary of dead fish in impoundments in Central Queensland division .................... 33 Table 5: Summary of dead fish in impoundments and waterways in the Mary/Burnett Division . 48 Table 6: Summary of fish deaths in impoundments and waterways of South East Queensland.. 59 page 3 Acknowledgements The compilation of this report required obtaining information from a wide range of sources. It is not possible to identify all the individuals that contributed to information in this report however the organisations and key individuals in some of those organisations need to be acknowledged. The Department of Primary Industries and Fisheries (DPI&F), in particular Terry Healy and Peter Kind were instrumental in recognising the importance of documenting the impacts of the fish death event in winter 2007 as this would provide useful information to the Department and to stocking groups that could be used in future management and stocking decisions. The contribution of other DPI&F officers that provided information on the fish death events and the stocking of impoundments is also acknowledged. This included Stephanie Chellan, Shaun Pobar and Chris Lupton. The Environmental Protection Agency is also acknowledged, particularly the Mount Isa regional office and the Maryborough regional office, and other offices that investigated the reports of fish death events and provided reports of their findings. SunWater is also acknowledged, particularly the Biloela regional office, and other offices that also investigated fish death events in impoundments which they manage and provided reports on their findings. Gladstone Area Water Board Hatchery is also acknowledged. Kurt Hutchby provided information on the fish deaths in Lake Awoonga and additional information on deaths in a number of other impoundments. Members of local stocking groups also provided important information on the fish death events including Mount Isa Fish Stocking Group, Fitzroy River Fish Stocking Association, Callide Fish Stocking Group, Clermont Fish Stocking Group, Fraser Coast Fish Stocking Group and Gary Sturdy of Lake Kurwongbah Fish Stocking Group. page 4 1. Summary Winter 2007, particularly July, was much colder than the long term average across much of the State, particularly away from the coast. Around the middle of the month the first reports started to emerge of fish death events, particularly from impoundments that had been stocked with fish over the past 20 years. The initial reports came from Lake Moondarra in the Mount Isa area but by the end of the month reports were received from many locations in central and southern parts of the State. It rapidly emerged that Barramundi were the most affected species in central and northern impoundments while Tilapia were the most affected species in southern impoundments. The widespread occurrence of fish death events from Lake Moondarra in the north to Lake Somerset in the south, with tropical species the most affected, and all deaths occurring roughly at the same time it was considered that low water temperatures were likely to be the primary cause of the fish death events. During July there was a period of almost 3 weeks where minimum air temperatures were mostly lower than the long term average by around 1oC in the north of the State to 2-2.5oC in the south. This is not a common occurrence as the last time this occurred was during the 1950s in the central and northern parts of the State. This resulted in significant drops in water temperatures to around 14oC in Lake Moondarra at Mount Isa and 10oC in Lake Callide at Biloela which was the lowest temperature recorded. Barramundi have been stocked in many impoundments in the north down to those in the Mary/Burnett in the south. Barramundi appear to become less active and reduce feeding when temperatures are below about 18oC but it is likely they can withstand temperatures as low as 14oC for short periods. However, if temperatures stay that low for extended periods (days or weeks), fish may die. Water temperatures as low as 14oC were recorded in many of the impoundments and this corresponded with fish deaths, involving primarily Barramundi, in many of these impoundments. This was also compounded by low water levels in many of the impoundments which would have contributed to low water temperatures. In many of these impoundments not all fish died however in Lake Callide, where the temperature fell to 10oC, all Barramundi appear to have died as no fish have been caught since that time. While a number of other species were involved in the deaths it was Barramundi that was affected the most. In all it is estimated that over 40,000 fish died. It is estimated that around 32,720 Barramundi died and based on the estimated average size of fish in each division that died it is estimated that this is equivalent to