BASIC INFORMATION ABOUT CARP IN AUSTRALIA
Carp (Cyprinus carpio) originated in China and spread throughout Asia and Europe as an ornamental and aquaculture species.
Carp were released into the wild in Australia on a number of occasions in the 1800s and 1900s but did not become widespread until a release of ‘Boolara’ strain carp from a fish farm into the Murray River near Mildura in 1964. The spread of carp throughout the Murray-Darling Basin coincided with widespread flooding in the early 1970s, but carp were also introduced to new localities, possibly through their use as bait.
Introduced carp have made full use of the heavily altered and regulated waterways we created up to the point where they are now the most abundant large freshwater fish in the Murray-Darling Basin and other degraded waters in south-eastern Australia. It is also important to know that the changes we made to our rivers not only benefited carp but also played and continue to play a very significant role in the low numbers of native fish species and many other forms of life in these waters.
Habitat: Carp are usually found in still or slowly flowing waters at low altitudes, especially in areas where there is abundant aquatic vegetation. They are also found in brackish lower reaches of some rivers and coastal lakes.
They are capable of tolerating a range of environmental conditions. They have a greater tolerance of low oxygen levels, pollutants and turbidity than most native fish, and because of this are often associated with degraded habitats, including stagnant waters.
Changes to water flows, declining water quality and other changes to river habitats over the past few decades have negatively affected many native fish while favoring carp.
Reproduction: Under suitable conditions, carp are highly prolific. They mature early – as early as 1 year for males and 2 years for females – and the females produce large numbers of sticky eggs. Carp migrate to and from breeding grounds during the breeding season, sometimes travelling hundreds of kilometers.
Most eggs and larvae die before they reach adulthood, although more may survive if environmental conditions are suitable. Floods seem to provide especially favorable conditions for carp breeding as well as abundant food for juveniles. This may help explain why carp experienced such a population explosion during the large floods of the 1970s.
Feeding: Carp are omnivorous, and their diet varies depending on what is available. They consume a range of small food items such as mollusks, crustaceans, insect larvae and seeds. These food items are sucked up from the bottom and filtered out using the gill rakers.
They can also consume plant material and general organic matter, especially when other food sources are not available (during winter, for example).
Carp rarely eat fish, but may consume fish eggs and larvae and disturb breeding sites.
Large predatory native fish, such as Murray cod, golden perch and bass, prey on juvenile carp.
REASONS WHY CARP IS VIEWED AS A PEST:
An important part of this project is to be honest with the public and that means discussing both the good and not so good points of carp. We do not deny the potential negative effect of EXCESSIVE carp numbers and therefor work with various local and international groups on safe and sensible ways to reduce and control carp which obviously does not include the Koi herpes virus. The National Carp Control Plan list the following points as reasons why carp should be removed from our water ways. Our comments are those in red text.
“Carp impacts cost Australia about $500 million every year.”
I asked the NCCP how this amount was calculated and to confirm that Carp ALONE is responsible for the whole amount. I also asked by how much the Koi Herpes Virus ALONE will reduce this amount. The reason why I asked these questions is because there are many and possibly much more significant reasons for murky waters and low native fish biomass, especially those that some anglers would prefer to catch like Murray cod and Golden Perch. The reply I got did not answer my question but referred me to lookup a document with the heading: Ecosystem responses to carp population reduction in the Murray-Darling Basin”
The following is an extract from that document but does not have any substance or proof that carp and carp alone is responsible for the $500 million figure. The extract (answer to my question) actually comes from another document, “Koehn et al.2000” I tried my best to find this document and after failing to do so I asked the NCCP to provide me with it, needless to say, I’m still waiting. A number of factors have an effect on the points listed below and I would like to see how carp is separated from the other factors.
“Carp cause damage estimated to total $500 million per year, by lowering water
quality of domestic and irrigation water supplies, damaging wetlands and other aquatic
habitats, impacting upon agriculture, commercial and recreational fisheries, regional
tourism industries, and harming native fish populations and river health (Koehn et al.
We received the document from another source and guess what - A word search have no results for the mystical $500 million figure.
The NCCP list key impacts of carp as follow:
- Carp are ‘ecosystem engineers’ – modifying waterways as they suck up mud. They stir up silt and muddy the water, blocking sunlight to aquatic vegetation, and impacting plankton, aquatic invertebrates, water birds, and native fish.
The feeding habits of very large numbers of carp who live in waters with very high loads of silt and sediment can be one of the factors contributing to water discoloration. Other factors like currents and wind also cause discoloration of water. Carp did not put the excessive loads of silt and sediment in the rivers to start with and also did not build the dams and weirs that’s responsible for keeping back silt and sediment and therefor the build-up of it. The following links provide more information about this topic.
Carp are 'water wreckers' – their feeding activity lowers water quality and increases nutrient levels. They also impact zooplankton, which normally feed on microscopic planktonic algae. When combined, these factors can cause blue-green algal blooms that impact recreational use of waterways (i.e., swimming, skiing etc.).
We’re not saying that Carp have zero effect but let’s put things in perspective and see who the “water wreckers” are. The following document from the Department of Agriculture and Water explain Algal blooms in more detail and Carp does not get mentioned once. The following are some extracts from the document: “Blue-green algae can reproduce quickly in favorable conditions where there is still or slow-flowing water, abundant sunlight and sufficient levels of nutrients, especially nitrogen and phosphorus. In still conditions, surface water may form a separate warm top layer (‘stratification’) in which blue-green algae is able to access sunlight and nutrients. If these combined factors are present for several days, algae multiply and form large ‘blooms’. The process of excess nutrients causing rapid growth of aquatic plant and bacterial life in a water body is known as ‘eutrophication’. Nutrients are either naturally present in sediments or are washed into water systems. In particular, phosphorus may be stored in significant amounts in sediments and released by normal bacterial activity. External sources of nitrogen and phosphorus are agricultural fertilisers, household products, sewage effluent and stormwater runoff, all of which can enter receiving waters either directly or during rainfall events. The availability of varying levels of nitrogen and phosphorus can affect which species of blue-green algae dominate and form blooms.
Blooms can form in response to increased temperatures and phosphorus levels even if nitrogen in water remains low, as some blue-green algae species can obtain nitrogen from the atmosphere. Source: http://www.agriculture.gov.au/water/quality/blue-green-algae
The following article also makes for interesting reading: http://theconversation.com/are-toxic-algal-blooms-the-new-normal-for-australias-major-rivers-59526
- Carp are 'resource hogs' – they take valuable food away from native fish. This particularly impacts smaller native fish species, but also larger species higher up the food chain. Some native species, like Murray cod, eat small carp, but this is not their natural food source.
The last time I checked they were not made out of plastic so of course they are a natural food source. Murray Cod have been feasting on them for decades. Maybe if the Concerned groups looked at the real reasons affecting predatory native fish instead for blaming everything on carp we would have had millions more carp consumed by now. Other reasons like damming, Coldwater pollution etc. are discussed in more detail in the section dealing with “Other threats”
- Carp are 'trash fish' – getting in the way of natives. People go fishing to spend time with friends, get outdoors and maybe catch a few fish. Catching carp can be fun, but most anglers want to catch natives. Carp currently undermine the recreational fishing industry, worth billions of dollars.
Yes, as Sport fishermen we also love native fish and want to see substantially bigger numbers of them in our water. Remember, the 80% carp is not responsible for the 20% natives. And also, let’s not forget that Brown and Rainbow trout are also invasive non-native species preying on native fish and crustaceans, yet at a great cost get stocked by the millions into our waterways. “Trash fish” is a term used by people with an extremely limited knowledge of carp. Carp is one of if not the most fished for sport fish in the world, millions of anglers spend ridiculous amounts of money on the massive variety of tackle and equipment associated with the various styles of carp fishing. It is also the world’s no. 1 or 2 most consumed farmed freshwater species, 4 159 000 tonnes were farmed in 2014…….yes, that sounds like a trash fish? Saying most want to catch natives does not mean there are not many who would like to fish for carp if allowed to do so as a sport (as is the case in many countries around the world including millions of immigrants and hundreds of thousands of tourist who visit Australia every year). Carp has been in our waters for many decades and in that time we grew recreational fishing to an industry worth Billions of dollars, how can it now all of a sudden destroy it? Plus we would love to see the calculation of the “Billions of dollars” recreational fishing industry carp can have an effect on. A billions of dollars freshwater (carp is a freshwater fish) recreational fishing industry does not sound like a struggling industry (considering it was built in the presence of carp).
- Carp are 'pump blockers' – they get into irrigation infrastructure and block pumps. This causes significant expense, through downtime and maintenance costs, for agricultural businesses.
Is it “Carp” or “fish” that block the pumps and because carp makes up the biggest mass it also represent the biggest proportion in the pump? Won’t the same happen if carp gets replaced with another species or will the other species know not to swim where the pumps are??
Carp have been identified as a priority pest species, both in Australia and internationally. The International Union for Conservation of Nature has named carp one of the world’s most invasive fish species.
What the NCCP, other “Concerned” Environmentalists, Matt Barwick (Coordinator of the Koi Herpes Virus Plan) and State Departments who support, promote and stock both Brown and Rainbow Trout NOT tell you is that Brown and Rainbow Trout are also listed as two of the eight fish species on the International Union for Conservation of Nature’s list of 100 most invasive species. If being on the list is a reason to be removed from our waterways then maybe Brown and Rainbow trout should also be packing their bags. I personally do not mind having trout in Australia and discuss the topic separately in more detail. Source: https://portals.iucn.org/library/sites/library/files/documents/2000-126.pdf
- A recent national survey reported that the public perceive carp as the fourth most significant vertebrate pest in Australia (after cane toads, feral cats and rabbits).
Well I guess that is to be the expected considering it has always been blamed for everything wrong in our waters and people were hardly ever (if ever) told about the other more devastating factors as well as the multibillion dollar industries build on carp and it’s growing international importance as food source and sportfish including in countries where it is listed as an invasive species.
- The image below shows the benefits of removing carp from an area. This wetland dried out, carp were prevented from returning using a screen and the system filled again naturally. The improved water clarity is clear to see. The good old "before and after photo". Come-on people, really. I guess desperate times call for desperate measures. This photo is part of the NCCP's ongoing attempt to remind people just how bad carp are? Comparing the two photos it now looks like carp have gained some magical powers and are now so bad that they can make everything look dull including the trees, riverbank and believe it or not .......even the blue sky wasn't spared. Is this what the NCCP promise the public, that all our waters will look like this after the release of the Koi Herpes virus? I think it will take a very brave Koi Herpes Virus advocate to make a statement like that. We all know that the virus will not eradicate Carp and that the image of clear waters are just another example of clever (untruthful) marketing to get the public on board.