And Thanks For All the Fish

lakemac

Lake Macquarie has a rich history of development and industry which has enabled the growth of a vibrant community. As it developed the Lake Macquarie catchment became synonyms with thriving agricultural, fishery and mining industries which surrounded the beautifully pristine lake. As it continued to grow love of the lake became central to the communities identity and was understandably a key factor in continued development and investment to create what is currently known as Lake Macquarie City. Unfortunately the expansion of industry and the desire to live around the lake began to have severe impacts and it became apparent in the mid 90’s that Lake Macquarie was suffering catastrophic damage.

In 1998 a community meeting was held to discuss the health of the lake and it became apparent that it was suffering from severe biodiversity degradation. The vast majority of larger predators had become absent from the lake, especially sharks, dolphins, seals, turtles and penguins. Fish populations had also dropped lake wide and large algal blooms where killing extensive portions of seagrass and producing mass fish deaths. This change was noticed by both commercial and recreational fishers and became a very significant worry for the community. As a result the health and biodiversity of the lake where made the top priority for the region, issues where identified and moves to fix the numerous issues where implemented.lmac_lg

Sediment and Eutrophication from Runoff

The primary issue for the lake was increased sediment load and nutrients in runoff. With rapid development around the lake the introduction of roads and estates produced excessive runoff which effected the vast majority of waterways. With development 75% of the shoreline plants that act as a crucial bio filter where removed from the lake while upstream many riparian zones suffered severe degradation from farming and industry. This produced two major issues:

  1. Excessive sediment load was being deposited in Lake Macquarie being carried from the surrounding suburbs and primarily from upstream. As the lake only has one small channel that connects it to the Pacific Ocean this quickly became clogged with sediment. Given the influence this had on accessibility dredging has long been implemented to allow continued access, what has more recently been identified is the isolation the excessive sediment produced for lake fauna. By blocking the channel it created an isolated population for many species in the lake, especially for the larger predators.
  2. With the local increase in garden fertilisers, domestic animal waste and removal of native vegetation along with poorly regulated fertiliser and pesticide use upstream eutrophication became one of the biggest issues for biodiversity. With the excess nutrients massive algal blooms dominated large portions of the lake with particular effects to seagrass and fish populations. With algal mats so thick much of the endemic sea grass died off from lack of photosynthesise resulting in the rapid spread of several extremely invasive species of sea weed. To compound effects reduced oxygen often lead to large scale fish deaths in affected areas (NSW Department of Environment, 2006).

map_lrg2To address the issues the Lake Macquarie Works Program was formed in 1999 and introduced a two prong solution (Economos-Shaw, 1999). The first part was dealing with the runoff directly by constructing artificial wetlands at every point a watercourse flowed into the lake or upstream of the major rivers. The wetlands are designed in stages to first filter larger debris and garbage before slowing water flow to deposit all sediment into the wetland. From here the water settles in a larger pond where plants are able to remove the nutrient load and the extremely fine grain sediment can be deposited before it finally flows into the lake or major river. The second part of this solution is the continued monitoring and quality control of these sites witch is predominantly done by schools. The lakes health was implemented as part of the local curriculum for schools to promote awareness and demonstrate the importance of individual impact, it also provides a means for annual quality testing at every site (FordComm Consulting, 2002).

Commercial Fishing

The other aspect that has produced devastating impacts to the biodiversity of Lake Macquarie is overfishing as a result from unregulated commercial fishing practices which have been developing since 1906. In the early 1900’s fishing consisted of small sailing or rowing boats with small nets and made for incredibly difficult work but with small catch sizes almost exclusively of fish. As the technological revolution progressed from World War 2 into the 50’s the addition of powered boats, powered winches and deep nets which went from the lake floor to the surface produced much higher yields, with these higher yields also came sharks, dolphins, seals, turtles and even penguins (Marine Rescue Lake Macquarie, 2009).

It was agreed that the overfishing of the lake had resulted in the almost complete loss of the larger predators and extreme losses to all fish species to the point where commercial fishing was becoming unviable. To resolve this problem commercial fishing was officially outlawed in Lake Macquarie in 2002 in an attempt to boost fish populations and strict catch sizes and permits put in place for recreational fishers (Obeid, 2003).

Current Biodiversity

Given the severe degradation of Lake Macquarie and the lack of any other rehabilitation on this scale it was feared that the lake would never return to its former state. It has been 15 years since the start of the rehabilitation and quality control processes and although they are still ongoing the biodiversity has recovered and improved beyond what was thought possible. Endemic seagrass populations have returned outcompeting the introduced and fish species have increased in population and in quantity with over 280 species present in the lake. More recently over the last 10 years the larger predators have also returned with four species of large sharks being cited, at least two separate pods of dolphins and turtle and seal sightings increasing rapidly (Piper, 2009). Lake Macquarie has become one of the largest and most successful aquatic rehabilitations in Australia reviving a severally degraded ecosystem to one of exceptional health showing other communities exactly how much is possible.

 

References

Economos-Shaw, R. (1999) Final report on the Lake Macquarie Biodiversity Project. Available at: http://trove.nla.gov.au/work/33335258?selectedversion=NBD22223927 (Accessed: 14 October 2016).

FordComm Consulting (2002) Teachers Resource Kit. Available at: http://www.livinglakemacquarie.org/files/dwnlds/Resource_Kit.pdf (Accessed: 14 October 2016).

Marine Rescue Lake Macquarie (2009) FISHING ON LAKE MACQUARIE. Available at: http://www.marinerescuelakemacquarie.com.au/images/pdfs/1260738399-wynn_s_fishing_on_lake_macquarie_opt.pdf (Accessed: 14 October 2016).

NSW Department of Environment (2006) Lake Macquarie and Tuggerah lakes,NSW Water Quality and River Flow Objectives. Available at: http://www.environment.nsw.gov.au/ieo/LakeMacquarie/report-01.htm (Accessed: 14 October 2016).

NSW Department of Environment and Conservation (2005) LAKE MACQUARIE STATE CONSERVATION AREA, PULBAH ISLAND NATURE RESERVE AND MOON ISLAND NATURE RESERVE PLAN OF MANAGEMENT. Available at: http://www.environment.nsw.gov.au/resources/parks/PoMLakeMacquarieSCAPulbahIslandNRMoonIslandNR.pdf (Accessed: 14 October 2016).

Obeid, E. (2003) Fisheries Management (General) Amendment (Commercial Fishing and Miscellaneous Matters) Regulation 2003.

Piper, G. (2009) Annual Report: AND FINAL REPORT OF THE LAKE MACQUARIE IMPROVEMENT PROJECT. Available at: http://www.livinglakemacquarie.org/files/dwnlds/Annual09_FinalRpt.pdf (Accessed: 14 October 2016).

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About Biodiversity Conservation Blog

I am an Associate Professor at The Australian National University and convene a (very awesome) course called Biodiversity Conservation. Myself and students in the course contribute to this blog.
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One Response to And Thanks For All the Fish

  1. A fascinating read. Many lessons here that could be applied elsewhere I presume. Phil

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