SPC/Fisheries 25/WP.99
14-18 March 1994
SOUTH PACIFIC COMMISSION
TWENTY-FIFTH REGIONAL TECHNICAL MEETING ON FISHERIES
(Noumea, New Caledonia, 14-18 March 1994)
On the introduction of exotic freshwater
fish species to the South Pacific
by
Hugh Dunnit & Hans Kneesun-Boompsadaisy
Goliath Consultants Inc,
Upper Choirboy, Hampshire
England
Introduction
The freshwater fish fauna of the South Pacific is relatively depauperate and in
many cases the complement of species in freshwaters is comprised mainly of secondarily
derived marine species. The African cichlid Oreochromis mossambicus was introduced
to many of the countries of the region to improve yields from freshwaters and to provide a
suitable species for aquaculture. Other introduced species include the carp (Cyprinus
carpio), rainbow trout (Onchorhynchus mykiss) and black bass (Micropterus
salmoides). Further introductions are being considered in Papua New Guinea for the
Sepik-Ramu river system to improve yields for the large indigenous population.
Not all fisheries introductions are for food, however. One example is the mosquito
fish, which was introduced to prey on mosquito larvae and hence reduce the biomass of
mosquitos and the incidence of malaria. Another is the grass carp, Ctenopharyngodon
idella, In this paper we consider other selective freshwater fish introductions for
the purpose of domestic security.
Urban crime in the South Pacific
As populations grow and societies in the region become more urbanised there is a
parallel growth in the incidence of crime, particularly housebreaking. Indeed most of the
developed world appears to be experiencing massive rise in opportunistic theft from houses
and cars. To combat this there has been an enormous growth in the security industry, with
the development of better alarms, motion sensors, video and audio equipment and the
creation of whole armies of security guards.
Such security is expensive and opportunistic thieves are no respecters of income and
will rob from whatever house they can. Clearly, the growth in personal incomes and wealth
in the South Pacific will be compromised by the threat of robbery. A regional initiative
is required and one that is appropriate to the conditions of the region and the lifestyle
of the inhabitants. Perhaps one solution is some form of biological security that is both
effective and affordable. The solution may be in the introduction of selected species of
freshwater fish from the Amazon River system in South America.
Species proposed for introduction to the South Pacific for domestic security
Several South American fishes have life history characteristics that recommend them
for use in domestic security.
The first of these is the Piranha (Serrasalmus rhombeus) (Figure
1). This inhabitant of the
Amazon is renowned for its extreme ferocity and Piranhas can be driven in to a feeding
frenzy within seconds through the scent of blood in the surrounding water. Although not
large (maximum size @ 35 cm) the Piranhas possess extraordinarily powerful and sharp
dentition and in schools can overwhelm and skeletonise a large animal in minutes.
The second is the electric eel (Electrophorus electricus) (Figure
1), which is a large (@
2.5 m) fish, capable of rendering a powerful electric shock that will stun or even kill a
large mammal. The electric shock is generated from specially modified muscle tissue, which
comprises about half the somatic tissue of the electric eel. The electric eel generates a
pulse of electricity lasting only about one second but may be as high as 1.0 Ampere and
500 volts, sufficient to severely shock a human being. Schools of electric eels can easily
render unconscious large mammals such as deer, horses, peccaries and capybara, following
which they can be consumed.
The third is a small (~ 2.5 cm) parasitic fish from the Amazon, the Candiru (Vandiella
cirrhosa) (Figure 1). This tiny catfish lives mainly on the blood of other fishes. They attach
themselves to the gills and will force their way into body apertures, such as the urethra,
where they bite into the tissue and consume blood from the lesion. They are sensitive to
urine and uric acid and will follow the trail of persons relieving themselves in rivers
and enter the urethra. When they swim into the urethra of humans, it can be difficult to
pull the fish out by the tail because the umbrella-like spines near the head may extend
and prevent its removal. Forced extraction may cause lacerations of the urethral mucus
membranes, which has caused death by haemorrhaging. Remedies have ranged from penile
amputation and suprapubic cystotomy to application of native herbs that softens the spines
of the Candiru so that it can be removed without trauma
Security procedures
To protect a house we suggest that homeowners construct a deep moat or pond around
their dwelling and stock it with the fishes mentioned above. A system of lockable
cantilever bridges can be used to gain access and isolate house when in residence or when
the property is vacated (Figure 2).
Effectively each homeowner would live on a small island surrounded by an aquatic
barrier or moat containing the electric eel, Piranha and Candiru. A stout fence should be
erected around the edge of the island to prevent persons falling in to the water
accidentally. To gain access to the house, a criminal would have to wade or swim through
the moat.
The bottom of the moat should be lined with broken glass so as to cut the feet of any
malefactor wishing to swim or wade across and gain entry to the house. The liberation of
blood in the water will drive the Piranha in to a feeding frenzy and they will school and
attack the criminal as he bleeds in the water. No doubt too the electric eels will join in
and incapacitate the villain where he can be readily consumed by the fish in the moat.
The householders can then inform the police who may wish to recover the bones and teeth
for identification purposes. The beauty of this system is that it will relieve pressure on
the police force and judicial system as the criminal makes a more beneficial contribution
to society as fish food.
Should the housebreaker fortuitously not be attacked by the electric eels or the
Piranha then there is a good chance that he will suffer the invasive penetration of the
Candiru in to the urethra. Studies have shown that the tension and stress of burglaries
results in loss of sphincter and bladder muscle control. The spontaneous emission of urine
in the water will act as a guide to the Candiru and the burglar, if wearing normal
relatively loose fitting clothing will be invaded by the fish.
Naturally the malefactor may not realise this and indeed make away with some property.
However, the subsequent blockage in the urethra and inability to urinate will force the
criminal to report to hospital where, once the penile obstruction has been identified as a
fish, this can be reported to the police, and an arrest made, leading hopefully, to the
recovery of property.
It might be argued that thieves could cross the moat in a small boat. A metal fence set
in the middle of the moat will prevent this although it is unlikely that opportunistic
thieves will be carrying a canoe or dinghy with them.
Maintenance of the guard-fish stocks
The Piranha and electric eel can be fed daily on household refuse, whilst the
Candiru will live by parasitising both these larger fish. The moat water should be kept
clean and changed from time to time and it is recommended that every care and attention is
given to ensuring that these fishes do not establish themselves in the natural freshwater
systems.
Establishing a domestic fish-based security system
The main requirement for this security method is a pond or moat surrounding a
house. This can be easily dug with a small excavator or by a gang of workmen at a cost of
a few hundred dollars. Small grants for this are currently available under the SPRADP
regional aquaculture support funds currently being administered by SPC's Fisheries
Programme. It may be possible to hire prisoners from the local corrective institution for
a nominal sum. For example prison labour has been used in Fiji to construct fish ponds for
aquaculture.
The three exotic species can be obtained from a recently established company, Piscurity
Inc, based in Manaus, Brasil, with branches in Suva, Port Moresby Auckland and Guam. A
detailed review of fish-security systems is given by Dr Vas de Ferens of FAO in his report
'Ancillary uses of cultured fish populations in the tropics' (FAO Fisheries Paper 99,
1992).
Future developments
The optimum use of a domestic fish security system as described here would include
some form of harvestable recovery for food besides protecting buildings and possessions.
Such multi-purpose aquaculture has been employed in Asia, where fish are cultivated in
rice paddy fields to reduce pest infestation and for food (see Rice-fish research and
development in Asia, ICLARM Conference Proceedings 24, 1992).
The Piranhas are an edible species, however, the electric eel is unlikely to appeal as
a source of food and the Candiru is far too small to be harvested and eaten. Current
research is aimed at finding dangerous fish species from South America and elsewhere that
could be used both for security and food.
References
- Breault, J. L. (1991) Candirú: Amazonian parasitic catfish. Journal of
Wilderness Medicine, 2: 304-312.
- dela Cruz, C. R., Lightfoot, C., Costa-Pierce, B. A., Carangal, B. R.,
& Bimbao, M. P. (1992) Rice-fish research and development in Asia.
ICLARM Conference Proceedings 24. 457pp.
- Marshall, N. B. (1965) The life of fishes. Wiedenfeld &
Nicholson, London. 402pp.
- Sterba, G. (1963) Freshwater fishes of the world. Viking Press. New
York. 877pp.
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