AFTER waiting a couple of months for algal identification results from CSIRO, Dr Ben Diggles has finalised his report regarding the cause of the fish kill at Beachmere Lake, Queensland, in April, 2019.
The full report is available for download HERE.
This report has been developed for the local community as an aside to Dr Diggles’ role as an independent aquatic animal health professional. The near 100 hours required to conduct the investigation and develop the report has been undertaken gratis without any payment of any sort from anyone.
As noted in the report, the fish kill was due to a blockage in an inlet pipe that caused a loss of tidal flushing to the lake, reducing its ability to assimilate nutrients allowing an algal bloom to develop. The bloom reduced oxygen levels to critical levels which in turn resulted in the unfortunate loss of in excess of 54,000 fish including many valuable broodstock.
The main issue with the repeated major fish kills in this lake is a misunderstanding by Moreton Bay Regional Council (MBRC) of its role as a valuable upper tidal fish nursery/refuge habitat of regional importance for the fisheries of northern Moreton Bay. Their failure to recognise the ecological role of the lake is exacerbated by poor engineering design of the natural southern entrance (particularly works done since 2010), which has eliminated any natural flushing during high tides and prevents migration of fish from the nursery during rainfall events. With the natural entrance now blocked, the lake becomes a fish trap and the whole function of the lake relies on artificial flushing through a single man-made pipe. When this pipe network is not working properly due to lack of maintenance, the risk of a massive fish kill is extremely high.
The long term solution to help reduce the risk of future fish kill events and reduce the risk of flooding of nearby residents homes during high tides and heavy rainfall involves a redesign of the natural inlet/outlet of the lake to restore some natural tidal flushing and fish passage to Moreton Bay using automatic adjustable tidal floodgates. For this, MBRC should work together in partnership with Queensland Fisheries habitat section using advice from Australia’s foremost fish passage experts from Ozfish Unlimited and Catchment Solutions, the former who would also be able to bring corporate support from groups such as BCF to help defray costs. To date MBRC has not agreed to do this or support any of OzFish’s proposed funding applications for monies to help with a redesign of the lake outlet.
Instead, the alternative suggestions we have heard from MBRC in recent times have included “fill the lake in” or conducting “regular netting” of the lake to cull fish. Both these options would represent an abject failure by MBRC in both its management of the system and its responsibilities to the local community. The reality is that MBRC is responsible for not only proper management of the water quality of the lake but also, like it or not, the welfare of the fish that live in the lake. All we ask is that MBRC recognise and take action on the recommendations of this report that has been made freely available to them at no cost, in stark contrast to the $150,000+ MBRC spent on engineering reports after the last fish kill event in 2009, which misunderstood the problem and lead to the inappropriate redesign of the natural lake outlet – effectively making the situation worse.
