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International Journal of Aquaculture, 2014, Vol.4, No.20 118
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concentration at low levels (Ploetz et al., 2007; Akan,
et al., 2009). Fish is a valuable and cheap food item and
source of protein to man. Concern about heavy-metal
contamination of fish has been motivated largely by
adverse effects on humans, given that fish consumption
primary route of heavy metal exposure (Nsikak et al.,
2007).
Since there is no formal control of effluents discharged
into the Nile, it is important to monitor the levels of
metals contaminants in the Nile fish and assess the
suitability for domestic uses. In order to effectively
control and manage water pollution due to heavy
metals, it is important to have a clear understanding of
the distribution and profiles of heavy metals in the
biota (Sabo et al., 2008).
Therefore, the present work aimed to determine the
profile of some heavy metals (Beryllium, Be,
Molybdenum, Mo, Barium, Ba, Silica, Si, Manganese,
Mn and Boron, B) in muscle tissues and head of seven
common Nile fish (
Barbus bynni, Labeo niloticus,
Mormyrops anguilloides, Marcusenius,
and to
evaluate the hazards and toxicity to fish population
and consumers in general. The heavy metals are not
destroyed by humans (Castro-Gonzeza and Méndez-
Armentab, 2008). Instead, tend to accumulate in the
body and can be stored in soft and hard tissues such as
liver, muscles and bone and threaten the health of
humans (Adham et al., 1999; Olaifa et al., 2004;
Ploetz et al., 2007; Paulami and Banerjee, 2012). Due
to toxicity and accumulation in the biota,
determinating the levels of these heavy metals in fish
species have received considerable attention in
different countries (Mohamed and Gad, 2008; Klavins
et al., 2009; Ozturk et al., 2009; Olowu et al., 2010;
Ambedkar and Muniyan, 2011; Wariaghli et al., 2013).
1 Material and Methods
1.1 Samples collection
Ten fresh and mature specimens (250-330 mm/length
and 500-850g weight) of each of seven commercial
fish from the Nile namely:
Barbus bynni, Labeo
niloticus, Marcusenius cyprinoides, Mormyrus niloticus,
Clarias lazera Mormyrops anguilloides
and
Protopterus
annectens
were purchased from the local fish market
in Khartoum. All specimens were previously collected
from Jabel Aulia area on the White Nile water and
broughtin ice container to thelabratory. Each fish was
skinned, gutted, washed and the whole head of each
specimen was carefully separated. The edible portion
of the muscles was also removed. Samples were taken
separately from muscles and head because most of
Sudanese people along the Nile eat fish heads. Both
muscles and heads were freeze dried to constant
weight using Freeze Dryer model 230 to -40°C. The
dried samples were ground to a fine powder and used
for analysis.
1.2 Chemical analysis
The concentration of heavy metals was determined in
the dried samples after acid digestion by Atomic
Absorption Spectrophotometer (APHA, 1998). About
4g of the each sample were kept in muffle furnace on
a hot plate at 550ºC for 3 hours to obtain the ash. Ash
was dissolved in 10 ml of 20% HCl then filtered in a
100ml volumetric flask and the volume was
completed with distilled water to 50ml. All
determinations in muscles and heads of each species
were done in triplicates and calculated as mean
content in (μg/100g dry weight). Data analysis was
conducted using the Statistical Package for Social
Science (SPSS, version 16, 2011). The result is
considered significantly different when p < 0.05.
2 Results and Discussion
The result of accumulation of heavy metals in muscles
and heads of the seven species of the Nile fish are
presented in (Figure 1 & 2). Both muscles and heads
of the analyzed fish contained almost same levels of
being with a range of 14.3 to 14.7 µg/100g. The range
of Mo in the muscles was 3.5 to 16.25 µg/100g, high in
M. anguilloides
and low in
P. annectens
(Figure 1),
while the head of
C. lazera
contained an average level
of 53.55 µg/100g, (Figure 2). Ba level in the muscles
was high in
L. niloticus
and
C. lazera
with average
value of 22 µg/100g. An average maximum level of
67.3 µg/100g was also detected in the head of
C. lazera
.
Mormyrus niloticus
contained minimum average level
of 18.8 µg/100g of Silica in the muscles, and
maximum average level of 23.5 µg/100g in the head,
while
B. bynni
contained 26.75 µg/100g in the muscles.
A range of Mn 16.8 to 38.5 µg/100g was detected in
muscles, high in
L. niloticus
, and of 41.5 to 89.85 µg/
100g in was detected in head, high in
C. lazera
and
M.
niloticus
, while low average level of Mn, 16.8 µg/
100g, was found in muscles and 41.5 µg/100g in head
of
P. annectens
. The range of B in muscles was 62.25