The
use of plants for healing purpose is getting increasingly popular as they are
believed as being beneficial and free of side effect (Leonardo et al., 2000).  The use of plant materials as spices,
condiments and for medicinal purposes has therefore become more popular and as
such more wild plants are being exploited for medicinal purpose.  There is therefore no doubt that orthodox
medicine itself appears to be strongly anchored on traditional medicine (Nweze,
2005).  Plants are used for different
purposes because some plants contain compounds of various class that have
insectidal, piscicidal and molluscicidal properties (Cagauan, 1992).  However, the occurrences of these fish poison
plants are varied based on location. Different parts of plants which contain
toxic substances used in poisoning fish include the roots, seeds, fruits, barks
or leaves (Gabriel and Okey, 2009). 
According to Gabriel and Okey (2009), ichthyotoxic plants used for
baiting and stupefying of fish are often crushed and cast into stagnant, slow
moving water or spread on  mud flats to
poison fish.  Ichthyotoxic plants have
been used as fish poisons or narcosing chemicals by the artisanal fishermen for
decades in the harvesting of fish in slow flowing waters (Oribhabor et al., 2014).

          According
to Neuwinger (2004) and Fafioye et al. (2004), the use of fish poison plants
and other plant products is one of the methods in traditional methods of fish
capture.  Plant extracts used as
piscicides in capture fisheries and aquaculture are considered advantageous
when compared to the back drop of using persistent and synthetic chemicals
(Gabriel and Okey, 2009).  Phytochemical
evaluation indicates that such piscicidal or ichthyotoxic plants contain
different active ingredients known as alkaloids such as nicotine, pyrethrum,
ryania, rotenone, resin, akuammine, tannins, saponins and diosgenin (Wang and
Huffman, 1991). Ichthyotoxins present in these fish poison plants will stun
fish when it passes through the gills or in some cases when ingested, it makes
the fish to float on the water surface for easy capture (Kritzon, 2003).

          Aloe
vera (Aloe barbadensis), a member of
the family liliaceae, is a naturally occurring perennial succulent plant that
is cactus-like in its characteristics, originating from Northern Africa
(Akinyale and Odiyi, 2007).  Aloe’s
thick, tapered, spiny leaves grow from a short stalk near ground level.  Aloe’s relationship to the lily family is
evident from the tubular yellow flowers produced annually in the spring that
resemble those of the Easter lily (Amit and Shweta, 2016).

          Important
pharmaceutical properties that have recently been discovered for the aloe vera
gel and whole leaf extracts includes the ability to improve bioavailability of
co-administered vitamins on human subjects (Chandan et al., 2007).  The
biological activities include promotion of wound healing, antifungal activity,
hypoglycemic or anti-diabetic effects, anti-inflammatory, anti cancer,
immuno-modulatory and gastro-protective properties. Furthermore, an increase in
bile flow and bile solids as a result of treatment with the extract suggests
stimulation of the secretary activity of the liver cells.  The hepatoprotective action is also
attributed to preserving the metabolizing enzyme of the liver through an antioxidant
activity (Ambrose et al., 1994;
Zodape, 2010).  In Nigeria, there is a
very strong cultural belief in herbal medicare, most often due to the latter’s
economic advantage and easier reach compared to the high cost of orthodox
medicine.  This is more compounded by low
literacy levels and often epileptic and grossly inefficient orthodox healthcare
delivery system.  Since the sudden
introduction and widely acclaimed mega-therapeutic potentials of aloe vera and
its products in the mid 1990s, and the highly expensive “processed” Aloe vera
products, it is a common site to see homestead aloe vera “plantations” at every
corner in most towns and villages.  This
has led to unrecommended and uncontrolled consumption of raw Aloe vera leaves
by highly and mighty in the society.

          Reports
have been documented in the therapeutic potentials of Aloe vera (Schmidt and
Greenspoon, 1993), its toxicity, especially when used parenterally (Brusick and
Menge, 1997;  Balter, 1992).  Report have shown that consumption of Aqueous
extract of Raw Aloe vera leaves in the histopathological and biochemical
studies in Rat and Tilapia tends to be lethal to fish at as low as 50ppm in
water causing 100% mortality within 96 hours (Taiwo et al., 2005). Methanolic extract of Aloe vera’s toxicity have also
been tested on rats (Saritha et al.,
2010).  A study on analgesic efficacy and
adverse effects of aloe vera in wistar rats have also been carried out (Ghosh et al., 2011).  Aloe vera has also been used to study its
dietary effects on growth performance, skin and gastro-intestine morphology in
rainbow Trout (Oncorhynchus mykiss).

 The African
catfish (Clarias gariepinus)
belonging to the family clariidae is the most cultivated species in
Nigeria.  This is attributed to its
ability to tolerate a varying  range of
environmental conditions, high stocking densities  under culture condition, fast growth rate,
disease resistance, acceptability of artificial feed, high fecundity, good
taste and meat quality, ease of artificial breeding, high market value etc (Eyo
et al., 2014). African catfish (Clarias gariepinus) is one of the highly
priced food fish in Nigeria and most parts of the world.  An Omnivorous scavenger that eats everything
it finds, the African catfish is particularly amenable to the farming practices
of smallholders, who comprise the majority of farmers in developing countries
(Musa et al., 2012, Ajala and
Owoyemi, 2015).  African catfish is rated
the third most cultured fish in the world (Offem et al., 2010).

          Biologically,
the African catfish (Clarias gariepinus),
is undoubtedly an ideal aquaculture species. 
It is widely distributed, not only in African countries but also in the
Netherlands; it thrives in diverse environments, temperate to tropical (Hecht et al., 1996).  It is hardy and adaptable principally as a
consequence of its air breathing ability, feeds in a wide array of natural prey
under diverse conditions, is able to withstand adverse environmental
conditions, is highly resistant to diseases, and is highly fecund and easily
spawned under captive conditions.  It has
a wide tolerance of relatively poor water quality and possibly the most
exciting feature of the species is its potential for highly intensive culture
without prerequisite pond aeration or high water exchange rates and its
excellent meat quality (Hecht et al.,
1996)

          Although
this plant, Aloe vera (Aloe barbadensis)
have been used in several toxicological studies, little or no information have
been documented on its toxic effects in the African catfish (Clarias gariepinus).  Also, most of the documented works have been
carried out using only the leaves of the plant but in this research, I will be
comparing the toxic effect of both the plant’s leaves and roots against the
African catfish (Clarias gariepinus).

1.2     Objectives of the study