Redfin Perch (Perca fluviatilis)

Redfin perch or European perch as it is sometimes known is a predatory invasive species of perch. Native to Europe and Asia, it has been introduced to a wide variety of ecosystems in countries like New Zealand, South Africa and Australia (DPI, 2014). Where it has caused substantial damage to native fish species and has been classified as a class 1 noxious species in New South Wales (DPI, 2014).

A Redfin Perch (Perca fluviatilis).

Source: http://www.dpi.nsw.gov.au/fisheries/pests-diseases/freshwater-pests/species/redfin-perch, accessed on the 28th of May 2014.

Redfin perch can be distinguished by their greenish colour, vertical bars across their sides and bright red pelvic, anal and caudal fins (Freyhof & Kottelat, 2008). They can live up to 22 years and the largest recorded length of a European perch was 60cm (DPI, 2014). The Redfin perch spawns between April and May with the eggs being deposited on water plants, they have been observed to attach to wading birds who then transport them to different waters (Freyhof & Kottelat, 2008).

A recently caught Redfin Perch (Perca fluviatilis).

Source: http://www.dpi.nsw.gov.au/fisheries/pests-diseases/freshwater-pests/species/redfin-perch, accessed on the 28th of May 2014.

The Redfin perch was first introduced into Australia in the 1860's, for sport for homesick brits. They are now widespread throughout most of southern Australia (DPI, 2014). They are a voracious predator of other species of fish and invertebrates, they can devastate native fish population by infecting them with the epizootic haematopoitic necrosis virus (EHN) (DPI, 2014).

The Native and Invasive Distributions of Redfin Perch.

Source:http://upload.wikimedia.org/wikipedia/commons/6/64/Perca_fluviatilis_distribution_map.png, accessed on the 28th of May 2014.

An example of the ability of Redfin perch to devastate a native species fish populations, occurred when 20,000 newly released rainbow trouts were eliminated within 72 hours of there first release (DPI, 2014). Unfortunately due to there widespread dispersal throughout southern Australia it is nearly impossible to completely eradicate this species without causing harm to native species (DPI, 2014).

References:

Freyhof, J. & Kottelate, M. (2008). Perca fluviatilis. IUCN Red List of Threatened Species. International Union for Conservation of Nature.

Redfin Perch (Perca fluviatilis). Department of Primary Industry NSW. 2014 [Online]. http://www.dpi.gov.au/fisheries/pests-diseases/freshwater-pests/species/redfin-perch. Accessed on the 28th of May 2014.

Siam Weed (Chromolaena odorata)

Siam weed is a tropical species of flowering shrub that belongs in the same family as the sunflower (Asteraceae) (Gunasekera, 2009). It is native to North America, Mexico and the Caribbean, it is a rapidly growing perennial herb that can reach a height of 2.5m in open areas and within shady areas it acts like a creeper allowing it to reach around 10 metres in height (Gunasekera, 2009).

Siam weed contains carcinogenic pyrrolizidine alkaloids making it extremely toxic to cattle and other organisms, while causing severe allergic reactions in humans (DAFF, 2014).

Close up of the flowers of Siam weed.

Source:http://www.daff.gov.au/plants/weeds-pest-animals-ants/weeds/a-z-listing-of-weeds/photo-guide-to-weeds/siam-weed. Accessed on the 27th of May 2014.

Siam weed is a hairy and glandular plant that gives off a pungent aromatic odour when the leaves are crushed. Its leaves can be between 4-10cm long with flowers of either white or pale pink, the are slightly hairy also and are spread through wind dispersal, dingy to fur, clothes or machinery (Gunasekera, 2009). Seed production within individual weeds can be anywhere between 80000 to 90000 per plant. The seeds need light in order to germinate and under ideal conditions can grow up to 3cm a day (Gunasekera, 2009).

An area of land Siam weed has invaded.

Source: http://www.lrm.nt.gov.au/weeds2/find/siamweed#.U4Q5F9wVfwI, accessed on the 27th of May 2014.

In Indonesia Siam weed has medicinal uses, when the young leaves are crushed the resulting liquid is used as a treatment for wounds on the skin (Gunasekera, 2009). In other countries Siam weed has been used as an ornamental plant, allowing for it to potentially cause problems if it escapes into the wild.

As an invasive species, siam weed is known for its invasion of field crops and the natural landscape of the areas it has been introduced into (Struhsaker, et al. 2005). Reports suggest that it has invaded the protected rainforests of Africa where it prevents the regeneration of important tree species, its flammability also affects forest edges causing damage to rain forests effected (Struhsaker, et al. 2005).

A biological control initiative to eradicate it from Sri Lanka and Guam was conducted in the early 1970's, this initiative used a defoliating artiid (Gunaserkera, 2009). This proved unsuccessful and was later scraped. Within Australia it was first discovered in 1994 and a harsh herbicide regime was implemented quickly, this proved much more successful than the 1970's eradication program (DAFF, 2014).

Current and potential distribution of Siam weed in Australia.

Source: http://www.weeds.org.au/cgibin/weedident.cgitpl=plant.tpl&state=qld&s=&region=nnc&card=S20, accessed on the 27th of May 2014.

References:

Gunasekera, L. (2009). Invasive Plants: A guide to the identification of the most invasive plants in Sri Lanka. Colombo. 116-117.

Siam weed (Chromolaena odorata). 2014. [Online] Available at: http://www.daff.gov.au/plants/weeds-pest-animals-ants/weeds/a-z-listing-of-weeds/photo-guide-to-weeds/siam-weed. Accessed on the 27th of May 2014.

Struhsaker, T., Struhsaker, P. & Siex, K. (2005). Conserving Africa's rainforests: problems in protected areas and possible solutions. Biological Conservation 123. 45-54.

Brown Tree Snake (Boiga irregulars)

The Brown tree snake (Bioga irregularis) is a species of snake that is native to the northern coast of Australia, Eastern Indonesia and Papua New Guinea, it is a tree-dwelling rear-fanged colubrid (Pianka, E. et al. 2004). Colubrids are a family of snakes that encompasses 2/3's of all current snake species. Colubrids are found on ever continent except Antarctica (Mehrtens. 1987). Most colubrids are non-venomous or relatively harmless to humans, the exception being the Boomslang, twig snake and Rhabdophis - they have all caused human fatalities (Bauer, et al. 1998).

The range of the Brown tree snakes across Asutralia and Papua New Guinea.

Source: http://en.wikipedia.org/wiki/File:Boiga_irregularis_rangemap.jpg, accessed on the 20th of May 2014.

As an invasive species, the brown tree snake has had a devastating effect. Sometime before 1952, the brown tree snake was accidentally transported to Guam from somewhere in the South Pacific (NALUSDA, 2014). With a lack of predators and an abundance of food the brown tree snake quickly began to reproduce and grow. Soon large populations of the brown tree snake were inhabiting Guam with the snake growing up to a metre larger than normally seen in its natural habitats (Savidge, et al 2007). 

The introduction of the brown tree snake to Guam as seen thousands of power outages, wide spread loss of domestic animals, the loss of native fauna and the potential for envenomation of small children (the only humans that face potential harm from the snake) (Savidge, et al. 2007). Research undertaken to find a potential predator for the brown tree snake, showed that there is no 'good' fit with many of the suggested predators failing to meet guidelines for their potential introduction into Guam (Caudell & Conover. 2001). 

Instead the American government has come up with the idea to disperse dead mice that are laced with acetaminophen (the active ingredient in panadol). Because the brown tree snake is one of the few predators that will eat already deceased prey, combined with the fact that they cannot handle acetaminophen, they believe this will hopefully control snake population numbers (Savarie, P. & Shivik, J. 2001).

The video below outline the procedures in which the acetaminophen-leced mice will be released.

Air-dropping mice into Guam.

Source: https://www.youtube.com/watch?v=ZZfBqdaafjA, accessed on the 20th of May 2014.

References:

Bauer, A., Cogger, H. & Zweifel, R. (1998). Encyclopedia of Reptiles and Amphibians. San Diego: Academic Press. 188-195.

Caudell, J. & Conover, M. (2001). Predation of brown tree snakes in Australia. International Biodeterioration and biodegradation.

Invasive Species: Animals - Brown Tree Snake. National Agricultural Library, United States Department of Agriculture. Accessed on the 20th of May 2014.

Mehrtens, J. (1987). Living snakes of the world in colour. New York: Sterling ISBN 0-8069-6461-8.

Pianka, E., King, D. &  King, R. (2004). Varanoid Lizards of the world. Indiana University Press, 588.

Savidge, J., Qualls, F. & Rodda, G. (2007). Reproductive biology of the Brown Tree Snake, Bioga irregulars. During Colonization of Guam and Comparison with that in their Native Range. Pacific Science. 191-199.

Savaire, P. & Shivik, J. (2001). Use of Acetaminophen for large-scale control of the brown tree snake. Journal of Wildlife Management. 356-365.

The Warty Comb Jelly Mnemiopsis leidyi.

The Warty comb jelly (Mnemiopsis leidyi) or sea walnut as it is sometimes known, is a species of ctenophore (commonly known as comb jellies) that originated in the western Atlantic waters (Encyclopaedia of life, 2014). For a time there was believed to be up to 3 species in this genus of comb jelly but that has since been revised down to a single species with differing ecological forms (Hansson, 2006).

The Mnemiopsis leidyi under stress glowing a blue-green colour.

Source: http://news.bbc.co.uk/2/hi/science/nature/6719965.stm, accessed on the 13th of May 2014.

The Warty comb jelly has a lobed oval-shaped, transparent body (Encyclopedia of life, 2014). They have 4 rows of ciliated combs, that will glow a blue-green colour when disturbed, they have many feeding tentacles - but unlike jellyfish do not have stinging nematacytes. There body is 97% water, with a body length of around 8-12 cm and a diameter of 2cm (Hansson, 2006).

Diagrams of the size and subumbrellar cavity of M. leidyi. 

Source: http://people.bu.edu/jrf3/BI547/BI547_IMAGES.html, accessed on the 13th of May 2014.

M. leidyi is a carnivorous organism that mainly eats zooplankton, other comb jellies, eggs and larvae. Its main predators are larger fish and birds (Kube, et al. 2007). M. leidyi have the ability to self-fertilise (they are hermaphroditic), the comb jelly can carry up to 150 at any one time and release both eggs and sperm into the water column during spawning. As many as 10,000 eggs can be fertilised in one spawning event (Hansson, 2006).

Sampling the M. leidyi found within the Black Sea.

Source: http://www.cefas.defra.gov.uk/our-science/ecosystems-and-biodiversity/non-native-species/invasive-comb-jellyfish-(m-leidyi).aspx, accessed on the 13th of May 2014.

In the 1980's M. leidyi was released into the Black Sea through the ballst water of passing cargo ships, 1989 the population had exploded to well over a million individuals (Tucker, 2012). This number suffered a small decline due to overconsumption of food stocks. The population of M. leidyi within the Black Sea mainly subsist on eggs and pelagic fish, this has had a damaging effect on fish numbers including the very lucrative anchovy species Engraulis encrasicholous (Zaika, et al 1990). Beroe ovate, a larger species of comb jelly was introduced as a form of biological control and had some success. Recent reports show that it appears that a stable predator-prey dynamic has occurred between M. leidyi and the other species within the Balck Sea (Hansson, 2006). The Warty comb jelly has now also spread to the Caspian Sea and the Baltic Sea, each time destroying the fish and zooplankton numbers with the introduction of Beroe ovate having no effect in these locations (Zaika, Tucker, 2012).

The spread of M. leidyi through the Caspian Sea.

Source: http://www.grida.no/graphicslib/detail/comb-jelly-mnemiopsis-leidyi-spreading-through-the-caspian-sea-invasive-species_11bd#, accessed on the 13th of May 2014.

References:

Hansson, H. G. (2006). Ctenophores of the Baltic and adjacent Seas - the invader Mnemiopsis or here. Aquatic Invasions 1(4): 295-298.

Kube, S., Postel, L., Honnef, C., Honnef, A. (2007). Mnemiopsis leidyi in the Baltic Sea - distribution and overwintering between autumn 2006 and spring 2007. Aquatic Invasions. 2 (2): 137-145.

Mnemiopsis leidyi. Encyclopedia of life. Accessed on the 13th of May 2014.

Tucker, A. (2012). How can a jellyfish this slow be so deadly? It's invisible. Smithsonian Magazine.

Zaika, V. and Sergeyeva, N. (1990). Morphology and development of Mnemiopsis leidyi in the Black Sea. Zoological Journal. 69 (2): 5-11.

Water Hyacinth (Eichhornia crassipes)

The water hyacinth (Eichhornia crassipes) is a native Brazilian aquatic pant and was introduced into Australia in the early 1900s as an aquatic ornamental  feature plant. Valued for its floral presentation, water hyacinth was released into ponds and lagoons in public parks throughout Queensland, water hyacinth has since become a major pest of creeks, rivers and dams (DAFF, 2014). Water hyacinth has thick, broad, glossy leaves that can rise up to 1m above the surface of the water. It's leaves are 10-20cm across and float on the surface of the water. It has attractive flowers (mostly pink and lavender in colour) that stick on an erect stalk, that can support a single spike of 8-15 flowers (fig.1) (Sullivan and Wood, 2012).

Figure 1: A close up picture of the water hyacinths flowers in bloom. 

Source:http://www.weeds.org.au/cgi-bin/weedident.cgi?tpl=plant.tpl&state=vic&s=&region=vm&card=W05, accessed on the 6th of May 2014.

Water hyacinths are one of the fastest growing plants, it reproduces primarily by way of runners or stolons (DAFF, 2014). Each plant can produce thousands of seeds each year, and these seeds can remain viable for more than 28 years (Sullivan and Wood, 2012). Water hyacinth has the ability to double its numbers in as little as 2 weeks (fig. 2).

Figure 2: A waterway that has been clogged with water hyacinth.

Source:http://www.coffscoastadvocate.com.au/news/plan-flush-out-killer/1367891/, accessed on the 6th of May 2014.

Water hyacinths environmental and social impacts include:

• The destruction of native wetlands and waterways, killing native flora and fauna.
• Depletion of water and loss of oxygen.
• Breeding ground for mosquitoes.
• Large infestation will clog waterways making it impossible to move aquatic vehicles through.
• Degradation of waterway quality.
• Damages infrastructure.

Ways in which this invasive weed species can be managed and controlled are:

• Removal by hand or machines such as harvesters.
• Spraying herbicides in heavily infected areas. Making to use herbicides that will not affect the water quality in the waterways affected.

Source: DAFF, 2014.

Figure 3: On the left, a woman using dried water hyacinth to make woven baskets, and on the right water hyacinth choking a waterway.

Source:http://blog.templeandwebster.com.au/kelly-upton-interior-trading-company/, accessed on the 6th of May 2014.

Water hyacinth can be used as a form of tonic for horses with skin conditions, it can also be used to make furniture (fig 3) and in some countries it is used as a cooking vegetable with the green leaves and inflorescence used (Perry, 1980).

References:

Perry, L.M. (1980) Medicinal plants of east and southeast Asia. Handbook of Energy Crops. MIT Press Cambridge.

Sullivan, P. R. and Wood, R. (2012). Water hyacinth, Eichhornia crassipes. Solms, seed longevity and the implications for management. 18th Australasian Weeds Conference. Melbourne.

Water hyacinth (Eichhornia crassipes). (2014). [ONLINE] available at: http://www.daff.qld.gov.au/plants/weeds-pest-animals-ants/weeds/a-z-listng-ofweeds/photo-guide-to-weeds/water-hyacinth. Accessed 6th of May 2014.

Banana Bunchy-Top Virus (BBTV)

Just what is the Banana Bunchy-Top Virus?

BBTV is a virus that affects the banana plants ability to produce leaves and petioles, this causes the plants 'bunched' look. Not only does it cause the plant to have a bunched look it also can distort the fruit, making it unsellable and cause the sterilisation of the plant, before eventually killing it (ISSG, BBTV. 2005). BBTV was first recognised in Fiji in 1889,since then it has spread worldwide and effects banana production. The virus can be spread from plant to plant by banana aphids, there are no resistant banana plant species. Controlling the spread of the virus is done through the destruction of affected plants, cessation of transportation of organic material from the affected area and pesticide use to eliminate the aphid species (Thomas and Dietzgen. 1991). Banana aphid can retain the virus for many weeks and because of this have this has the ability to cover large distances (DAAF, 2014). Scientists have cultured banana plant material from affected plants and have managed to produce material that does not contain the Bunchy-Top Virus (DAFF, 2014).

A healthy group of Banana plants.

Source:http://kccbigcountry.hubpages.com/hub/Banana-Tree, Accessed on the 29th of April 2014.

Within Australia BBTV is currently present in SE Queensland and Northern New South Wales. Do to strict quarantine measures within Australia concerning the transportation of possible infected organic materials it has not spread to other areas on Australia yet (DAFF, 2014).

The Affects of BBTV. 

Source: en.wikipedia.com, accessed on the 29th of April 2014. 

Because of it's ability to spread rather easily and the lack of progress in finding a 'cure' for this virus, the Banana Bunchy-Top Virus has become one of the world's most devastating plant viruses. In Australia BBTV is the focus of a 3 year project funded by the Australia Banana Growers Council, the Banana Industry Advisory Committee and Horticulture Australia Limited to work towards its eradication (DAFF, 2014). But in other parts of the world there has been little effort made to help find a permanent solution to this virus.

Banana Virus quarantine sign in Hawaii.

Source: http://great-hikes.com/blog/banana-virus/, accessed on the 29th of April 2014.

References:

Bunchy Top. (2014). Available at: http://www.daff.qld.gov.au/plants/health-pests-diseases/a-z-significant/bunchy-top. (Accessed 29th of April 2014).

Ecology of Banana Bunchy-Top Virus (BBTV) (2005). Available at: http://www.issg.org/database/species/ecology.asp?si=141. (Accessed 29th April 2014.)

Thomas, J, E,. and Dietzgen, R.G. (1991). Purification, characterisation and serological detection of virus-like particles associated with banana bunchy-top disease in Australia. Journal of General Virology 72: 217-224. University of Hawaii at Manoa.

Feral Cats (Felis catus) in Australia

The domestic cat (Felis catus) was first introduced into Australia in 1806 and by 1820 there were already significant numbers of feral cats surrounding Sydney, by 1890 90% of Australia had a feral population (Abbott, 2008). Cats are small carnivorous mammals that feed on small vertebrate and invertebrate animals. The introduction of cats to Australia had a profound effect on the small native wildlife. In the early part of the 20th century large populations of cats were released into gold mining sites in Western Australia, and as a form of population control for the rabbit and native rat (Dickman, 1996). This attempt at bio control caused for the populations of feral cats to increase tenfold and further affect the dwindling numbers of native birds and mammals within these areas.

Distribution of Feral Cats in Australia. Source: Feral.org.au, Assessed on the 13th of April 2014.

A major case study on the effect of feral cats on a species is the decline of the eastern barred bandicoot (Perameles gunnii) in Victoria, this population first started to decline in 1840 following settlement by Europeans who cleared land for grazing and introduced carnivorous species like the cat. By 1982 there was only a population of 1750 and as little as 150 by 1990. Scientists’’ believe that the introduction of feral cat species into the home range of the barred bandicoot increasing the mortality rate of the juveniles of the species thus causing the collapse of the population as a whole (Dickman, 1996).

 Feral Cat in the Northern Territory. Source: Tim Doherty ECU. Assessed on the 13th of April 2014.

Feral cats within Australia have no known natural predator except for the Wedge-tailed eagle and the dingo, without these two species managing the population numbers, feral cats are the apex predators. Cats have become one of the greatest threats for native wildlife survival in Australia and are now one of the worst invasive species to be introduced to this country.

References:

• Abbott, I. (2008). Origin and spread of the cat, Felis catis on mainland Australia. Conservation Science Western Australia Journal. Vol. 7, 1 – 17.
• Dickman, C. (1996). Overview of the Impacts of Feral Cats on Australian Native Fauna. Australian Nature Conservation Agency – Institute of Wildlife Research. Pg, 1 – 97.