International Journal of Marine Science, 2016, Vol.6, No.10, 1-8
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tissue is next in terms of metals tissue accumulation after gills (Akan et al., 2012).
In many studies (Noreña et al., 2012; Akan et al., 2012; Hosseini et al., 2015) gills and liver are also chosen as
target organs for assessing metal accumulation. Abdolahpur Monikh et al., (2013) indicated that the metal
concentrations in gills reflect the concentrations of metals in waters where the fish species live, whereas the liver
is the main tissues of accumulation, biotransformation and excretion of metals in fish. Recently, Bat (2014)
pointed out that in previous studies on metal levels in fish from the Black Sea coasts show that bioaccumulation of
metals was more in the liver than those in other tissues.
Benthic fishes are nearby sediment and receive more sediment-associated metals than pelagic fishes (Abdolahpur
Monikh et al., 2013; Hosseini et al., 2015).
M. merlangus
is benthopelagic fish and occurs on sand, mud and
gravel sea beds at depths down to about 100 m (Fishbase, 2016). Bat et al. (2015) demonstrated the distribution
of heavy metals in sediments of Sinop coast in the Black Sea shows a variable pattern. Although high metal levels
were found in some regions of the Black Sea coast, the level of most often of the heavy metals were not extremely
enriched in these surface sediments of Sinop coast and did not present a serious threat to the local fauna and flora
(Bat et al., 2015). Moreover pelagic fish are very high metabolic rates, and consequently high food intake rates, a
property that accentuates the exposure to heavy metals (Kojadinovic et al., 2007). Topping (1973) suggested that
mainly plankton feeding fish contain much higher concentrations of some heavy metals than bottom feeding fish.
Abdolahpur Monikh et al., (2013) were surprised that
Euryglossa orientalis
, which are flatfish, bottom feeders
and are associated with sediment species, did not show the highest metals concentrations. Accumulations of heavy
metals were generally found to be species specific and may be related to their feeding habits and the
bioconcentration capacity of each species (Bustamante et al., 2003; Bat et al., 2013b; Abdolahpur Monikh et al.,
2013; Bat, 2014). Bat et al. (2013b) found that whiting feed on anchovy as well. In the present study it may be
suggested that metals might have been taken up from prey in the pelagic zone and on sea bed and upper layer of
the water. Abdolahpur Monikh et al. (2013) found no significant correlation between metal concentrations in
sediment and fish tissues and argued that demersal species,
Johnius belangerii
and
Euryglossa orientalis
were not
suitable biomonitors for heavy metal contamination in the Persian Gulf.
M. merlangus
is of great commercial importance because they are more consumed fish in Turkey and one of the
most dominates species in the Black Sea. However, the eggs of
M. merlangus
are the parts of fish that are
consumed by human; it has not been studied in previous works in this region. The present study indicated that Cu,
Mn and Co concentrations were higher (p<0.05) in eggs samples than in the muscle samples, whereas the others
were no significant differences (p>0.05). Fish eggs of
M. merlangius
are hardly consumed by people, this tissue is
very important for transferring contamination to the next fish generations, resulting in diseases (Terra et al., 2007).
The results of this study are also in agreement with the many studies which have indicated that gonads have a
higher tendency to accumulate heavy metals than those in muscles. Yilmaz (2003) found that gonads showed
higher metal concentrations than muscle for
Mugil cephalus
and
Trachurus meditterraneus
from Iskenderun Bay,
Turkey. Similarly Wong et al. (2001) found the highest metal concentrations in liver and gonads compared with
edible muscle tissues tended to accumulate less heavy metal. Terra et al. (2007) also found the highest Zn values
in gonads for three fish species, suggested that it might be also associated to reproductive processes. Jezierska et
al. (2009) pointed out that waterborne metals might be accumulated in the gonads and adversely affected gamete
production and viability. The egg shell does not provide full protection the embryo against heavy metal influence,
especially during the swelling phase so; metals may accumulate in the egg (Jezierska et al., 2009).
With regard to health risk, the tolerable weekly intakes were estimated by means of references for edible tissues of
fishes consumed by people. The annual quantity of fish consumed is 6.3 kg/person in 2013 (TUIK, 2014), which
is equivalent to 17.3 g/day for Turkey. The EWI (Estimated Weekly Intake) and EDI (Estimated Daily Intake)
values presented in Table 1 were estimated by assuming that a 70-kg person will consume 17.3 g fish/day which is
equal to 121.1 g fish/week. The tolerable weekly intake of heavy metals as PTWI (Provisional Tolerable Weekly
Intake), are set by the Food and Agriculture Organization/World Health Organization (FAO/WHO) Joint Expert
