A Review of Historic Western Victorian Lake Conditions in Relation to Fish Deaths
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A REVIEW OF HISTORIC WESTERN VICTORIAN LAKE CONDITIONS IN RELATION TO FISH DEATHS Publication 1108 March 2007 EXECUTIVE SUMMARY Eel deaths occurred in waterways across Victoria from 2004 to 2006. EPA Victoria worked with responsible agencies to investigate the cause of the deaths. An information gap was identified regarding changes throughout the catchments over time. Much of this knowledge had not been documented formally and was difficult to assess. It is important to note that this report is based on a number of published accounts of the historical timeline as well as utilising personal accounts of history. Therefore there may be small discrepancies in exact dates. Anecdotal evidence and unpublished reports of the history of lakes Modewarre, Bolac and Colac indicate that, over the past 150 years, all lakes in the Western District have shown a distinct pattern of drying out during periods of extended drought. As early as 1846 the lakes showed signs of drying, which would indicate that any fish within those lakes also died due to lack of good quality water. The three lakes examined have been stocked by landholders, recreational anglers or commercial eel fishermen to hold the current stock of fish and eels. The catchments in which each lake sits have undergone changes, including culverts being developed to reduce flooding, the size of water storage reservoirs being increased and changes in agricultural practices. ACKNOWLEDGEMENTS EPA would like to formally acknowledge the contribution of all those who assisted with the research into the Western District lakes. Much information was held in the minds of those who visit the lakes regularly for recreation, farming and lifestyle, and it is this that has provided such broad insight into one of Victoria’s precious resources. We thank the following for their contributions: Community members and groups from towns surrounding the lakes, local landowners, professional eel fishermen, Colac Historical Society, Geelong Historical Society, Lake Bolac Historical Society and Information Centre, Winchelsea Historical Society, Corangamite Catchment Management Authority, Glenelg Hopkins Catchment Management Authority, Department of Sustainability and Environment, Department of Primary Industry, Barwon Water, Surf Coast Shire, Colac Otway Shire and Ararat Shire Council. 1 A REVIEW OF HISTORIC WESTERN VICTORIAN LAKE CONDITIONS IN RELATION TO FISH DEATHS INTRODUCTION summer period of 2005—06, a hot north wind blew for one or two days, followed by a southerly change that EPA has been investigating a number of eel and fish caused great turbidity in the water due to wave action. deaths across Victoria in the past two years. While This occurred three times, and after each occasion scientific research has been undertaken and continues, eels washed up dead. social and historical knowledge relating to the lakes Other lakes in the Western District have also across the Western District is often the type of experienced incidents of eel and/or fish deaths. In the knowledge that may assist in finding common links 1970s Lake Gnarpurt reportedly suffered a large eel relating to the eel deaths. death event, locally thought to be due to a blue-green EPA has gathered social and technical information algal bloom. In 1980 another eel death was attributed relating to the response of Western District waterways to ‘Red Tide’, and around the year 2000 both ‘Red to dry periods with respect to eel and fish deaths, Tide’ and low water levels were considered to have changes in catchment conditions that may have resulted in large numbers of eel deaths. impacted on water quality and quantity in waterways, ‘Red Tide’ is an estuarine or marine algal bloom. It and the management of the waterways with respect to often appears in such high concentration that it water quality and quantity. Three lakes which have appears to change the water red or brown. been involved in recent fish and eel deaths have been the focus: lakes Modewarre, Bolac and Colac. Around 1983 locals report that Lake Murdeduke had a large fish and eel death event caused by a ‘Red Tide’ EPA has also produced a report (Publication 1109) and low water levels. In 2001 another fish kill event highlighting findings and future directions for research occurred although no dead eels were reported. into the fish and eel deaths. These two reports support each other. During 1974 noxious blooms of blue-green algae occurred in Lake Burrumbeet. The deaths of numerous livestock and several fish kills have been attributed to REPORTED INCIDENTS OF EEL AND FISH the bloom (EPA 1976b). Anecdotal evidence suggests DEATHS IN WESTERN VICTORIAN LAKES that around 2002—03, following November rains an algal bloom developed and carp died in the lake. Later, Little documentation of fish and eel deaths within the when water levels dropped, eels also died. Deaths of Western District lakes exists. While there are eels caused by the effects of eutrophication, or numerous references to periods of drought, little nutrient pollution, in Lake Colongulac were also reference has been made to the death of the aquatic documented, but no reference to the date was made. species that inhabit the waters. (Bookaar 1983, Ballarat University 2005) During the summer of 2004—05 fish and eels died en In 1841 George Robinson reported in his journal, ‘The masse in Lake Modewarre. A local resident recalls that water in the lake (lake Bolac) was nearly dried up. The on 22 December 2004 carp died en masse, although shore resembled the shore on the sea. Dead eels were no dead or ill trout or minnow were observed. On 31 strewed along the beach. Counted 100 dead and large. January 2005 the resident recalls seeing dead eels From 2 to 3 feet and a half long and 3 inches thick… between the north rocks and the boat harbour. At this the dead eels lay in heaps: dead eels lay in mounds; time it was estimated that there were 50 dead eels for thousands of dead eels and very large ones too, every 100 metres of shoreline. The eels were described strewed the ground around the lake’. as all being large eels with blood flush around the jaw. During mid-February 2006 a larger eel death incident LAKE MODEWARRE occurred, with numerous sizes of eels observed to be dead or dying. A resident recalls that the eels Lake Modewarre is a shallow crater lake located 27 km appeared as if they were trying to escape from the south-west of Geelong on the Princes Highway near water, travelling about a metre up the shoreline then Moriac. The lake is situated in a 533-hectare Crown returning to the water’s edge. Many of the eels were reserve established in 1965 for public recreation. The observed to be bleeding from the gills and had large lake area averages 414 hectares, with a capacity of white lesions on their bodies. 13,100 megalitres and an average depth of between 3.5 and 4.5 m. The small catchment (less than 250 km2) Significant eel deaths were also reported in lakes extends in an elongated shape from the northern Bolac and Colac during the 2005—06 summer. Over slopes of Mt Moriac in the north-east to the south of 5000 eels were reported in the Lake Bolac incidents Wurdiboluc Reservoir in the south-west (see figure 3.1). and approximately 200 in Lake Colac. Both lakes are in The two main drainage lines feed from these periods of drought and have been affected in the past extremities (Winstanley 2002). by changing regimes and altered environmental flows. One Lake Bolac resident recalled a conversation he had with a keen fisherman in the area. During the 2 A REVIEW OF HISTORIC WESTERN VICTORIAN LAKE CONDITIONS IN RELATION TO FISH DEATHS construction of the now known Wurdee Buloc Reservoir commenced in 1927 using horses, scoops and manpower. It is cited in a report by Kinhill Stearns (1986) that the Cape Otway Road had to be diverted to the south to accommodate the development of the swamp to a reservoir. Around 1945 the lake was reported to be very low and some farmers had been able to wade across to the other side. In 1947—48 Lake Modewarre was totally dry and farmers would go rabbiting and graze sheep on the middle of the lakebed. At this time, two man-made dams were evident (due to the lake being dry) on the western side of the lake. It is thought that these dams may have been constructed during a long period of Figure 3.1 Lake Modewarre catchment area drought in the past for stock-watering purposes. It is History also believed that, at this time, the lake had been reduced to two big swamps with Lewis Road running Prior to European settlement the Wathaurong people through the middle (Anecdotal). occupied a large region that included the Lake By 1955 the second enlargement of the Wurdee Buloc Modewarre catchment. Between 1803 and 1832 William Reservoir was well under way. The banks were Buckley had described the lake as being perfectly extended, and increased in height by about 1.8 m, and fresh and abundant in eels, with the lake surrounds Cape Otway Road was relocated again (Kinhill Stearns being well established, with red gums and other trees 1986). providing excellent shelter. In 1846 the lake was recorded as being dry; an extract from a journal by Dr During the 1960s the Council was proclaimed the Thomson stated this was the first time he had seen the authority in control of navigation of the lake. Water lake dry (Wynd 1992). levels of the lake could still not be controlled, resulting in Council buying land around the lake (Wynd 1992).