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Comparative Studies of the Impacts of Freshwater, Cultivated and Preserved Tiger Shrimps on Consumers’ Health

Authors:
  • Igbinedion University Teaching Hospital, Nigeria, Okada
  • Covenant University Ota Ogun State

Abstract and Figures

Aim: The study was aimed at comparing the levels of heavy metals in Tiger shrimps- Penaeus monodon from different source categories, to ascertain the impacts of the selected heavy metals on the consumers’ health. Hypothesis: Heavy metals in blood serum of shrimp consumers were accumulated solely from the shrimps. Methodology: Tiger shrimps obtained from Ekpan Creek, Shrimp industry and shrimp farm were tested for metals (iron, manganese, nickel, and lead) concentrations using a Perkin Elmer 3110 model Atomic Absorption Spectrophotometer (AAS). Blood samples of respondents were analyzed for the levels of iron, manganese, nickel and lead using Inductively Coupled Plasma MassSpectrometer (ICP-MS). Analysis of Variance (ANOVA) was used to test for the significant differences in the heavy metals in the shrimps and consumers’ blood samples at probability level of 0.05. Duncan Multiple Range (DMR) test was used to identify the source of variance using SPSS version 19.1. Health Risk Indices of heavy metals were noted as significant from 1 and above and insignificant at below 1. Results: The shrimps exhibited different trends of heavy metals according to their sources. Results showed that the safety in consumption of the shrimps was is in the order of cultivate (pond) shrimps > freshwater shrimps > preserved shrimps. Shrimp consumption had corresponding impacts on the health of the consumers. Processed shrimps should be properly examined for fitness of consumption prior to marketing, while chemicals such as sodium bisulfate, tripolyphosphate should be discouraged. Conclusion: Metallic construction materials should be discouraged and stringent water quality monitoring is recommended in Tiger shrimp aquaculture while incorporating adoption of environment friendly agricultural practices. Perturbed aquatic environments such as Ekpan Creek require protection from anthropogenic activities and impactful remediation process with a view to protecting the Tiger shrimps and other aquatic biota.
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_____________________________________________________________________________________________________
*Corresponding author: E-mail: patrick.isibor@covenantuniversity.edu.ng, patrickisibor007@gmail.com;
Annual Research & Review in Biology
23(2): 1-13, 2018; Article no.ARRB.38069
ISSN: 2347-565X, NLM ID: 101632869
Comparative Studies of the Impacts of Freshwater,
Cultivated and Preserved Tiger Shrimps on
Consumers’ Health
Isibor Patrick Omoregie
1*
, Izegaegbe Joshua Idowu
2
,
Igbinovia Joan Osahenrunmwen
3
, Obafemi Dorcas Yemisi
1
and Oluowo Elohor Freeman
4
1
Department of Biological Sciences, College of Science and Technology, Covenant University, Ota,
Ogun State, Nigeria.
2
Department of Zoology, University of Zululand, Richards Bay, South Africa.
3
Department of Nursing, School of Basic Medical Sciences, Obafemi Awolowo University, Ife, Nigeria.
4
Department
of Animal and Environmental Biology, University of Benin, Benin City, Nigeria.
Authors’ contributions
This work was carried out in collaboration between all authors. Author IPO designed the study, wrote
the protocol and wrote the first draft of the manuscript. Author IJO carried out all medical related
procedures and analysis. Author IJI managed the analyses of the study. Authors IJI, ODY and OEF
managed the statistical analysis and the literature searches. All authors read and approved the final
manuscript.
Article Information
DOI: 10.9734/ARRB/2018/38069
Editor(s):
(1)
Nema Abdelhameed Mohamed, Department of Zoology, Alexandria University, Alexandria, Egypt.
(2)
George Perry, Dean and Professor of Biology, University of Texas at San Antonio, USA.
Reviewers:
(1)
María del Carmen Bermúdez Almada, Mexico.
(2)
Suneeta Kumari, Maulana Azad National Institute of Technology, India.
(3)
Edebi N. Vaikosen, Niger Delta University, Nigeria.
Complete Peer review History:
http://www.sciencedomain.org/review-history/22956
Received 29
th
October 2017
Accepted 10
th
January 2018
Published 31
st
January 2018
ABSTRACT
Aim:
The study was aimed at comparing the levels of heavy metals in Tiger shrimps- Penaeus
monodon from different source categories, to ascertain the impacts of the selected heavy metals on
the consumers’ health.
Hypothesis: Heavy metals in blood serum of shrimp consumers were accumulated solely from the
shrimps.
Original Research Article
Isibor et al.; ARRB, 23(2): 1-13, 2018; Article no.ARRB.38069
2
Methodology:
Tiger shrimps obtained from Ekpan Creek, Shrimp industry and shrimp farm were
tested for metals (iron, manganese, nickel, and lead) concentrations using a Perkin Elmer 3110
model Atomic Absorption Spectrophotometer (AAS). Blood samples of respondents were analyzed
for the levels of iron, manganese, nickel and lead using Inductively Coupled Plasma
MassSpectrometer (ICP-MS). Analysis of Variance (ANOVA) was used to test for the significant
differences in the heavy metals in the shrimps and consumers’ blood samples at probability level of
0.05. Duncan Multiple Range (DMR) test was used to identify the source of variance using SPSS
version 19.1. Health Risk Indices of heavy metals were noted as significant from 1 and above and
insignificant at below 1.
Results: The shrimps exhibited different trends of heavy metals according to their sources. Results
showed that the safety in consumption of the shrimps was is in the order of cultivate (pond) shrimps
> freshwater shrimps > preserved shrimps. Shrimp consumption had corresponding impacts on the
health of the consumers. Processed shrimps should be properly examined for fitness of
consumption prior to marketing, while chemicals such as sodium bisulfate, tripolyphosphate should
be discouraged.
Conclusion: Metallic construction materials should be discouraged and stringent water quality
monitoring is recommended in Tiger shrimp aquaculture while incorporating adoption of environment
friendly agricultural practices. Perturbed aquatic environments such as Ekpan Creek require
protection from anthropogenic activities and impactful remediation process with a view to protecting
the Tiger shrimps and other aquatic biota.
Keywords: Freshwater shrimp; cultivated shrimp; preserved shrimp; heavy metals; blood serum;
health risk index.
1. INTRODUCTION
Shrimps are highly demanded delicacy globally,
due to their nutritional values [1]. They contain
low fat, high protein, vitamin B
12
and are also
selenium-rich; thus enhances immunity, thyroid
function and reproductory system [2,3]. There
are two types of shrimp farms, namely coastal
and inland shrimp farms. The disadvantage of
coastal practices is due to the fact that they
exchange water directly with the ocean hence
the pond is prone to shrimp escape. Coastal
farms also cause destruction of mangrove
swamps hence impacting habitats of fish,
shellfish and aquatic birds. Although inland
ponds reduce the potentials for escape, both
practices face the challenge of water pollution
due to contaminations from feces and waste
foods from the ponds.
Shrimp farmers use ponds that become ever
more crowded and dirty as the animals grow.
The drive to maximize space for profit by
producing more shrimps in less space has
resulted in some farmers adding like commercial-
grade fungicides and pesticides to the water in
order to abate illness under such crowded
conditions. There have been reports of farmers
treating pond water with banned antibiotics.
After capture, shrimps are stored in freezers
with salt, water and an additive called sodium
bisulfite which is an industrial bleaching
agent. The essence of sodium bisulfite is that it
slows down decomposition and abates the
process of melanosis, a condition that makes the
harvested shrimp to blacken over a short time.
Another preservative is sodium tripolyphosphate
(STP), a dehydrating agent that gives the
shrimps the firmness to protect it during handling
throughout the stages from producers to
consumers.
Indiscriminate discharge of refuse, industrial
effluents, petroleum wastes and crude oil spills
replete with heavy metals into nearby aquatic
systems have impacts on the biota component
and may eventually impact the health of the
populace that consume the finfish and shellfish
harvested from such waterbodies. Contamination
of heavy metals in the aquatic environment has
attracted global attention owing to its abundance,
persistence and environmental toxicity. The
increasing pollution by heavy metals has a
significant adverse health effects for
invertebrates, fish, and humans. Farmed fishes
as well as aquacultures heavily rely on
formulated feed and few of the commercial feed
producers failed to meet up with standards for
the requirement of fish and the source of raw
material for the production of the feeds tends to
be contaminated with heavy metals and others
[4,5]. The metal pollution of aquatic ecosystems
is increasing due to the effects of urbanization
and industrialization [6]. Toxic heavy metals are
unrelenting environmental contaminants because
they cannot be despoiled or destroyed [7] and
Isibor et al.; ARRB, 23(2): 1-13, 2018; Article no.ARRB.38069
3
comprise a significant portion of the problem as
these metals known for their bioaccumulation
and bio-magnification, which cause various
health hazards to human [8]. Generally, culture
fish bio-accumulate chemicals as well as heavy
metals directly from polluted water by diffusion
through gill and skin or they ingest with food [9].
The mechanism is by incorporation of heavy
metals from anthropogenic perturbations into the
aquatic food; thereby biomagnifying up the
pyramid of biomasses through alimentation [8].
Variability in water and sediment properties is a
function of a number of factors which have been
enormously reported in previous studies.
Generally, these factors can be categorized as
authoctonous and allothonous factors working in
tandem. Tukura et al. [10] attributed variation of
physico-chemical properties of water and
sediment of Mada River, Nasarawa State,
Nigeria to seasonal variation.
The water matrix of an aquatic ecosystem is the
first receptor of the contaminants released from
anthropogenic activities. The sediment then
serves as repository to the contaminants [11].
However, the rate of deposition of these
contaminants is a function of their sorption
capacities; which vary among contaminants.
Ogbeibu et al. [12] pointed out that manganese,
zinc, copper, cadmium, lead and total
hydrocarbons had very high sorption capacities
from water into the sediment of Ikpoba River.
Furthermore, the contaminants journey from
these environmental matrices into the tissues of
biota where they are stored indefinitely. Froese
et al. [13] reported bioaccumulation of
polychlorinated biphenyls from sediments to
aquatic insects in Saginaw Bay, Michigan, USA.
Davies et al. [14] reported accumulation of heavy
metals in tissues of Tympanotomus var radula
from sediment of Elechi Creek, Nigeria. Akan et
al. [15] attributed accumulation of metals in the
gills, liver, stomach, kidney, bones and flesh
tissues of Tilapia zilli, Clarias anguillaris,
Synodentis budgetti and Oreochronmis niloticus
from River Benue to the concentrations in the
ambience. Isibor et al. [11] attributed
impermissible levels of trace metals in Clarias
gariepinus of Osse River, Edo State, Nigeria to
high levels observed in the water and sediment.
The study aimed at comparing the levels of
heavy metals in Tiger shrimps- Penaeus
monodon (Fabricius, 1798) from different source
categories, with a view to ascertaining the
impacts on consumers’ health.
2. MATERIALS AND METHODS
2.1 Materials
The apparatuses used include Perkin Elmer
3110 model Atomic Absorption
Spectrophotometer (ASS), Thermo (Bremen,
Germany) X Series 2 Inductively Coupled
Plasma Mass Spectrometer (ICP-MS), concentric
glass nebulizer, peltier-cooled glass spray
chamber, Silica flasks, volumetric flasks,
Whatman filter paper 42, Bunsen burner, and
glass plate. The reagents include HNO
3
: HClO
4
(5:1) mixture, 2 M Analar HNO
3
, deionized water,
Analar grade metal salt, non-stabilized 30%
hydrogen peroxide (H
2
O
2
) solution and distilled
water. Shrimp samples captured from the Creek
using woven cylindrical non-return valve traps,
baskets and scoop nets, coconut, cassava and
earthworm baits.
2.2 Methods
2.2.1 Experimental design
The experiment was designed to analyze the
concentrations of Fe, Mn, Zn, Cu, Pb, Cd, and Ni
in 90 human blood samples from 3 groups (30
replicates per group) namely pond shrimp
consumers, freshwater shrimp consumers and
preserved shrimp consumers.
2.2.1.1 Research hypothesis
1. Each group of consumers depended solely
on the specific shrimp category for their
animal protein requirement.
2. The shrimps are solely the source of heavy
metals in the blood of the subjects.
3. All human subjects have fed on same
quantity of shrimp for at least 2 years.
4. Metal exposure of the shrimp groups is
basically dependent on the respective
operation techniques required for each
group.
Blood samples were collected early in the
morning (at 8:00 hrs) before breakfast so as to
minimize alterations as a result of exposure of
human subjects to metals through other routes
than oral and to ascertain proper digestion of
food consumed the previous day during night
rest. Sampling periodicity was at interval of 2
weeks and 5 times fortnightly in order to
minimize possible error due to alterations in diet
and health status [16,17].
Isibor et al.; ARRB, 23(2): 1-13, 2018; Article no.ARRB.38069
4
2.2.2 Sample collection
2.2.2.1 Shrimps
Samples of Tiger shrimps- Penaeus monodon
were obtained from Ekpan Creek using local
fishing gears such as woven cylindrical non-
return valve traps, baskets and scoop nets; in
conjunction with coconut, cassava and
earthworm baits. Other categories were obtained
from a commercial pond, and a sea food store.
The shrimps in the pond were fed with a mixture
of natural food items such as coconuts, worms
and supplemented with commercial shrimp feed.
Shrimps (Penaeus monodon) were caught in the
local coastal waters and were kept alive in water
tanks on board. Immediately after arrival on
board the boat, they were sorted by size
(standard length: 12-15 cm and weight: 24- 32 g)
and kept alive in aerated tanks during the
transportation to the laboratory within half an
hour. The shrimps were then chilled to death by
crushed ice in the laboratory. Anthropogenic
activities such as oil exploration and exploitation
activities were observed around the Creek. Some
preservatives were used to conserve the shrimp
stock obtained from the frozen food store.
Shrimps obtained from the natural environment
(Ekpan Creek), a shrimp farm (pond), and
seafood store (preserved stock) were identified
using identification manual prepared by Chan
[18] and sorted according to size and weight.
Thirty (30) shrimp individuals within the range of
12-15 cm (standard length) and 24- 32 g (weight)
from each source were grouped into three
categories, preserved in ice coolers and labelled
as freshwater, cultivated and preserved shrimps.
They were transported immediately to the
laboratory for identification and further analysis.
2.2.2.2 Consumers’ blood samples
A total 90 human volunteers above 18 years
were recruited into the research with their
informed consents. All precautions provided by
World Medical Association [19] were duly
adopted in sampling the blood of respondents.
Only non-smokers and those who are medically
fit were recruited into the study. Their general
health status was also verified through routine
inquiries based on the fact that the health status
of respondents is a function of the concentrations
of metals and their blood [16,17]. 3 mL of whole
venous blood samples of 30 donors (15 males
and 15 females) from each group was collected
using sterilized syringes and placed in EDTA
containers with lid, preserved with lithium heparin
anti-coagulant. Each sterile syringe and needle
was properly disposed of after use on each
respondent.
2.2.3 Sample preparation
2.2.3.1 Shrimps
Wet weight shrimp tissue (10 g) was placed in
silica flasks covered with a glass plate, 20 mL of
HNO
3
: HClO
4
(5:1) digester was added.
Digestion process was carried out by heating the
mixture at 105°C for about 24 hours according
to Turkmen [20]. The extract was made up to 25
mL with 2 M Analar HNO
3
and diluted with
deionized water. For quality assurance, reagent
blanks were processed simultaneously in
triplicates. Each residue was filtered into
volumetric flasks with the aid of a Whatman filter
paper.
2.2.3.2 Consumers’ blood samples
Prior to digestion, all blood samples were
vortexed thoroughly to ascertain homogeneity.
Reagent blanks were prepared by adding
deionized water in place of the samples to
monitor background concentrations of all
analytes. 1 mL of 2M Analar grade HNO
3
was
added to each blood sample and was allowed to
react for 30 minutes. Thereafter, 750 μL of non-
stabilized 30% hydrogen peroxide (H
2
O
2
)
solution was added to each sample. After
addition of all reagents, the tubes were sealed
with lids and digested for 4 hours using a
microwave machine (CEM, Matthews, NC).
Samples were then removed from the microwave
and allowed to cool. Samples were then stored in
a refrigerator at 8°C until analysis.
2.2.4 Sample analysis
2.2.4.1 Shrimps
The solution prepared from shrimp sample was
tested for metals (iron, manganese, nickel, and
lead) concentrations using a Perkin Elmer 3110
model Atomic Absorption Spectrophotometer
(ASS) and recorded in Mg/Kg; wet weights [21].
To determine metal concentration, the ASS was
calibrated for each metal by dissolving 1 gram
Analar grade metal salt in 1 L of distilled water.
Standard and corresponding blanks were run
with each set of experimental digest. The
detection limits of iron (0.5 μg/g), manganese
(0.5 μg/g), nickel (0.05 μg/g), and lead (0.03
μg/g) were carefully observed.
Isibor et al.; ARRB, 23(2): 1-13, 2018; Article no.ARRB.38069
5
The actual concentration of metal was calculated
thus:
Actual concentration of metal (Mg/Kg wet weight)
= RD X Dilution factor [22].
Where RD = ASS reading of digest
  =   
ℎ  
2.2.4.2 Consumers’ blood samples
Blood samples were then analyzed for trace
metals using the Thermo (Bremen, Germany) X
Series 2 Inductively Coupled Plasma Mass
Spectrometer (ICP-MS) equipped with a
concentric glass nebulizer and peltier-cooled
glass spray chamber. Trace metal calibration
standards for ICP-MS analysis were
prepared using Fe, Mn, Zn, Cu, Pb, Cd, and
Ni standards. Two sets of calibration
standards were prepared for metals that were
anticipated to be in low concentrations
(such as Pb, Cd, Ni, and Mn) and high
concentrations (such as Fe, Zn, and Cu).
Samples were analyzed without dilution in the
original storage containers to minimize the
possibility of contamination. For the calibration,
standards back-calculated concentrations were
ensured to be within ±15% of the nominal
concentration (±25% of the nominal
concentration for the lowest concentration
standard). Quality control checks were done to
ascertain that concentrations for all metals were
found to be within ±15% of the nominal
concentration.
2.3 Statistical Analysis
Descriptive statistics such as the mean, range
and standard error were used in assessing the
significant differences in the heavy metals in
blood and shrimp samples using ANOVA (P <
0.05). Duncan Multiple Range (DMR) test was
used to identify the source of variance using
SPSS version 19.1. Mean of data generated
were compared with mean concentrations of
the heavy metals in the shrimps. Health risk
indices of the metals in the respondents were
assessed.
2.4 Health Risk Assessment
Health risk assessment is the knowledge of the
quantitative risk each contaminant poses to the
health of the consumers of the fishes. Health risk
indices (HRI) of the heavy metals above one (1)
was presented as significant while HRI below 1
was insignificant.
Health Risk Index was calculated thus;
Health Risk Index (HRI) =
While Daily intake of metals (DIM) =
Where M was the metal concentration in fish
tissue (Mg/Kg), CF is Conversion factor = 0.085.
60 kg was adopted as the average body weight
of the consumers of the fish. Daily intake of fish
was estimated as the fish consumption rate in
Nigeria= 48 g/person/day [23].
3. RESULTS AND DISCUSSION
All tested metals (Fe, Mn, Zn, Cu, Pb, Cd, and
Ni) were detected in all the analyzed categories
of shrimp samples. However, the different
categories of shrimps had distinguished metal
distributions.
3.1 Distribution of Metal Contaminants in
Shrimps
The trend of metal contaminants in freshwater,
cultivated and preserved shrimps were; Mn > Ni
> Zn > Fe > Pb > Cd, Fe > Zn > Mn > Ni > Pb >
Cd and Zn > Mn > Ni > Cd > Fe > Pb
respectively. The trend of metal contamination in
the cultivated Tiger shrimps of the current similar
was similar to the trend (Fe> Zn> Mn> As> Co)
observed in shrimps (Penaeus semisulcatus)
captured from Persian Gulf by Heidarieh et al.
[24]. The remaining part of the trend observed in
the cultivated Tiger shrimps was similar to the
trend observed by Das et al. [25] in Clarias
gariepinus which was: Cr> Cu> Ni> Pb> Cd in
cultivated Claria gariepinus. The similarities in
the accumulation trend might be due exposure of
the organisms to the observed heavy metals in
the different environments.
However, the trend of metals in the three
categories of Tiger shrimps in the current study is
at variance with the trend (Fe > Cu > TPH > V >
Cd > Pb> Mn) observed in Palaemonid shrimp:
Macrobrachion vollenhovenii of Osse River in
Nigeria by Isibor and Oluowo [24]. Differences
Daily Intake of Metal (DIM)
Reference Oral Dose (ROD)
M X CF X Daily intake of fish
Average body weight
Isibor et al.; ARRB, 23(2): 1-13, 2018; Article no.ARRB.38069
6
observed between the current study and the
previous can be attributed to variation in the
levels of exposure, species of the shrimps [15],
feeding habits etc. [27,28,29,30].
3.2 Concentrations of Metals in Different
Categories of Shrimps
Concentrations of iron (Fig. 1), and manganese
(Fig. 2) among the compared shrimp samples
were in the order of preserved shrimp >
freshwater shrimp > FAO > pond shrimp. The
concentrations of iron and manganese in the
preserved shrimp and freshwater shrimp were
significantly higher than the limits set by the Food
and Agricultural Organization (FAO). High
concentration of these metals observed in the
preserved shrimp can be attributed to the
chemicals used in the process of preservation.
The unacceptable limits observed in the
freshwater shrimps may be due to the
complimentary impact of anthropogenic activities
on Ekpan Creek, coupled with resultant effects of
the intrinsic and extrinsic factors influencing the
ingestion, metabolism and depuration of the
metal in the shrimps. Bioaccumulation of iron and
manganese from the wild, prior to capture,
coupled with preservation techniques might have
concertedly contributed to the outstandingly high
concentration detected in the preserved shrimps.
Although the level of iron observed in the
cultivated shrimp was fairly lower than the
regulatory limit, the concentration might rise
above the recommended limit over time if the
source of the contamination is not prevented.
Iron contamination of ponds may ensue from the
materials used in the pond construction. Metal
tanks for examples, are prone to corrosion which
could be enhanced by the water in the tank.
Impermissible dietary levels of iron observed in
the preserved and freshwater shrimps may elicit
many implications in the consumers such as
multi-system organ failures, coma, convulsion
and ultimately death in shrimp and human
[31,32].
Only the concentration of manganese in the
tissues of the pond shrimp was lower than the
standard regulatory limit. Although manganese is
an essential element in enzymes such as
arginase, pyruvate carboxylase, and
manganese-superoxide dismutase. Despite the
vital biological roles manganese plays, excess
concentration may cause serious health
implications such as permanent neurological
damage, insomnia, poor cognitive performances
etc. [33].
The concentrations of zinc detected in all the
shrimp categories were higher than the
established FAO regulatory limit i.e. preserved
shrimp > freshwater shrimp > pond shrimp (Fig.
3). Zinc is ubiquitous within cells in contrast to
iron, which is contained in defined cellular
components and has defined physiological roles.
The biological role of zinc can be categorized
into three functional classes namely, catalytic,
structural and regulatory functions [34]. Although
zinc is essential for the epidermal,
gastrointestinal, central nervous, immune,
skeletal and reproductive systems of vertebrates.
Exposure of humans to high concentration of
zinc over a long period of time may result in
health challenges such as stomach cramps,
Fig. 1. Concentrations of iron in different shrimp categories
N= 30, FAO limit= 100 Mg/Kg wt. weight [22]
0
20
40
60
80
100
120
140
160
180
POND FRESH PRESERVED FAO
Iron concentration (mg/kg wt. weight)
Isibor et al.; ARRB, 23(2): 1-13, 2018; Article no.ARRB.38069
7
Fig. 2. Concentrations of manganese in different shrimp categories
N= 30, FAO limit= 1 Mg/Kg wt. weight [22]
nausea, vomiting, and in extreme cases more
devastating consequences such as anemia,
damage to the pancreas, and decreased levels
of high density lipoproteins (HDL) cholesterol
may occur [35]. Toxicity of zinc has also been
demonstrated in rats, rabbits and shrimps. High
concentrations of zinc observed in the tissues of
the cultivated shrimp can be attributed to the
components of the shrimp feed. This is based on
the fact that research findings have
demonstrated a commensurate response of
vertebrates to manipulation of dietary zinc [36].
Homeostasis of zinc is therefore essential for
animals and humans. Homeostasis is mediated
in vertebrates by adjustments in total zinc
absorption and endogenous intestinal excretion
[37]. Entire zinc burden in vertebrates is lost
through gastrointestinal tract and losses through
skin, hair and sweat [36,38]. Findings have
shown that iron and zinc exhibit antagonistic
interaction i.e. the higher the accumulation of one
the less the accumulation of the other i.e. high
doses of inorganic iron decreased zinc uptake as
measured by changes in plasma zinc after an
oral dose [38]. This might be a contributing factor
to the relatively lower iron concentration
accompanied by high zinc concentration in the
cultivated (pond) shrimps. Although the order of
lead accumulation was preserved shrimp > pond
shrimp > freshwater shrimps, the concentrations
in all the shrimp categories were lower than the
established limit set by FAO (Fig. 3).
Fig. 3. Concentrations of zinc in different shrimp categories
N= 30, FAO limit= 75 Mg/Kg wt. weight [22]
0
0.5
1
1.5
2
2.5
3
POND FRESH PRESERVED FAO
Manganese concentration (mg/kg wt.
weight)
0
10
20
30
40
50
60
70
80
90
100
POND FRESH PRESERVED FAO
Zinc concentration (mg/kg wt. weight)
Isibor et al.; ARRB, 23(2): 1-13, 2018; Article no.ARRB.38069
8
Fig. 4. Concentrations of lead in different shrimp categories
N= 30, FAO limit= 2 Mg/Kg wt. weight [22]
The concentrations of cadmium in all the shrimp
categories were lower than the FAO regulatory
limit. Cadmium like any other substance could be
absorbed via the gills and has been known to
cause damage to shrimp gills. Cd poisoning
could lead to anemia, renal damage, bone
disorder and cancer of the lungs. The highest
concentration of cadmium was 0.4 mg/kg in the
freshwater shrimp and the lowest concentration
(0.09 Mg/Kg) was observed in pond (cultivated)
shrimp (Fig. 5).
Nickel concentration detected in the tissues of all
shrimp categories were lower than the regulatory
limit established by FAO (Fig. 6). Low
concentrations of nickel accompanied by high
concentrations of iron were earlier observed in
Clarias gariepinus and Tilapia mariae of Osse
River, Nigeria by Isibor and Imoobe [8]. This is
can be attributed to the high essentiality of iron
as a constituent of haemoglobin and non-
essentiality of nickel.
Heavy metals with concentrations which were
observed to be higher than their recommended
values were further subjected to health risk
assessments. The preserved shrimps
followed by the freshwater shrimps had health
risk indices of iron (Fig. 7), manganese (Fig. 8),
and zinc (Fig. 9), while the health risk of
Fig. 5. Concentrations of cadmium in different shrimp categories
N= 30, FAO limit= 2 Mg/Kg wt. weight [21]
0
0.5
1
1.5
2
2.5
POND FRESH PRESERVED FAO
Lead concentration (Mg/ Kg wt. weight)
0
0.5
1
1.5
2
2.5
POND FRESH PRESERVED FAO
Cadmium conc. (mg/kg wt. weight)
Isibor et al.; ARRB, 23(2): 1-13, 2018; Article no.ARRB.38069
9
Fig. 6. Concentrations of nickel in different shrimp categories
N= 30, FAO limit= 0.5 Mg/Kg wt. weight [22]
zinc recorded in the pond shrimp was exactly on
the margin line of significance (Fig. 9). This
implies that preserved shrimps posed the
highest risks to the consumers. This can be
attributed to the chemicals used in preserving the
shrimps. The significant health risk index of iron
observed in the freshwater shrimps can be
attributed to the oil exploration activities around
Ekpan Creek.
Generally, the contaminants in the observed
shrimps were mainly essential metals. This is
partly due to their high thresholds of essentiality.
The orders of health risks among the metals
detected in the preserved shrimps was Zn > Fe >
Mn, Mn > Zn > Fe, and Mn > Fe > Zn in the
preserved shrimps, freshwater shrimps and pond
shrimps respectively. Manganese was the major
contaminant in the freshwater and preserved
shrimp samples. It is therefore paramount to
ensure the shrimps from the ponds and the
shrimp industries are carefully screened for
manganese concentrations in order to prevent
health implications such as poor cognitive
performance in school children and neurological
disorders similar to Parkinson’s disease [35].
The level of manganese, zinc, and nickel
detected in the blood of the individuals who
consumed preserved shrimps were quite higher
Fig 7. Health risk indices of iron in different categories of tiger shrimps. The red line indicates
significant health risks at value 1
0
0.1
0.2
0.3
0.4
0.5
0.6
POND FRESH PRESERVED FAO
Nickel concentratiion (mg/kg wt . weight)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
POND
FRESH
PRESERVED
Health Risk Index of Fe
Shrimp Category
Isibor et al.; ARRB, 23(2): 1-13, 2018; Article no.ARRB.38069
10
Fig. 8. Health risk indices of manganese in different categories of tiger shrimps. The red line
indicates significant health risks at value 1
than the recommended limits (Table 1). The
concentration of zinc in the blood of the
individuals who consume freshwater shrimps
were also higher than the recommended limit.
This observation is backed up by the results of
the sequence and health risks of both metals,
except in the case of nickel which had no
significant health risk. The unexpectedly high
concentration of nickel in the blood of the
consumers of the preserved shrimp might be due
to a high octanol-water partition coefficient of
nickel in the consumers. It is important for
shrimpers to have substantial knowledge about
the environmental conditions the shrimps were
exposed to in the wild prior to capture, so as to
incorporate the information in decision making in
terms of preservation options.
The levels of metals detected in the blood of the
consumers of the respective shrimps quite
conform to the observations of the
concentrations in the tissues of the shrimps. This
implies that shrimp consumption had
corresponding impacts on the health of the
consumers. Results suggest careful screening of
shrimps (particularly processed ones) for
concentrations of heavy metals before approval
by authorities. Use of chemicals such as sodium
bisulfate, tripolyphosphate etc. is therefore
discouraged.
Fig. 9. Health risk indices of zinc in different categories of tiger shrimps. The red line indicates
significant health risks at value 1
0
0.5
1
1.5
2
2.5
3
POND
FRESH
PRESERVED
Health Risk Indiex of Mn
Shrimp Category
0.9
0.95
1
1.05
1.1
1.15
1.2
1.25
POND FRESH PRESERVED
Health Risk Index
Shrimp Categories
Isibor et al.; ARRB, 23(2): 1-13, 2018; Article no.ARRB.38069
11
Table 1. Comparison of heavy metals (µg/L) in consumers of Pond, River, and Frozen Shrimp
with a Reference standard
Blood category Fe Mn Zn Pb Cd Ni
Pond shrimp 311.5 ± 12 11.42 ± 0.04 2864.68±122.72 6.31 ± 0.001 0.9 ± 0.08 0.12± 0.26
Freshwater shrimp 511.2 ± 4 15.2 ± 0.02 9064.8±12.2
*
10.8 ± 0.01 4.5 ± 0.2 0.1± 0.63
Preserved shrimp 452.2 ± 16 24.2 ± 2
*
8864.68±98.72* 14.2± 0.01 3.8± 0.01 0.3± 0.01
*
Certified Range
[39]
309-521 8-18.7 4400-8600 8-18.7 0.3-7 0.2
Note: Values were expressed in μg/L and sample size = 30. Emboldened and asterisked values signify significant values;
higher than certified range
4. CONCLUSION
The shrimps exhibited different trends of heavy
metals according to their sources. Results
showed that the safety in consumption of the
shrimps was in the order of cultivate (pond)
shrimps > freshwater shrimps > preserved
shrimps. Choice of construction materials for
shrimp pond should be well informed and
stringent water quality monitoring is
recommended in Tiger shrimp aquaculture while
incorporating adoption of environment friendly
agricultural practices. Perturbed aquatic
environments such as Ekpan Creek require
protection from anthropogenic activities and
impactful remediation process so as to protect
native Tiger shrimps and other aquatic biota.
ACKNOWLEDGEMENT
Without reservations, we profoundly appreciate
the unparalleled financial support rendered by
the Covenant University Centre for Research and
Innovation and Discovery (CUCRID).
COMPETING INTERESTS
Authors have declared that no competing
interests exist.
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Aims: This study is aimed to determine the levels of some heavy metals in different species of fish and to compare the results with other standard values. Study Design: The gills, liver, stomach, kidney, bones and flesh of four common fish species (Tilapia zilli, Clarias anguillaris, Synodentis budgetti and Oreochronmis niloticus) were collected for analysis of heavy metals. Place and Duration of Study: This study was carried out in River Benue, Vinikilang, Adamawa State, Nigeria between the periods of 312 value of 12.65 µg/g was significantly observed in the Gills of Synodentis budgetti (p <0.05), the liver of Tilapia zilli was second while the flesh of Heterotis niloticus shows the least value. From the result of this study, the tissues accumulation was observed in the order of gills>liver>stomach>kidney>bones>flesh. The gills of all the fish tend to accumulate significant high levels of heavy metal than other tissues. Accumulation of metal in different species is the function of their respective membrane permeability and enzyme system, which is highly species specific and because of this fact metals accumulated differently in the tissues of fishes as observed in the study. Conclusion: Based on the above results, it can therefore be concluded that metals bioaccumulation in the entire fish species study did not exceeds the permissible limits set for heavy metals by FAO, FEPA and WHO. Therefore these fishes are fit for consumption.