# Metal Bioaccumulation by Carp and Catfish Cultured in Lake Chapala, and Weekly Intake Assessment
## 4 Discussion  
The between-tissue and between-species analyses of the metal bioaccumulation patterns showed a higher concentrating capacity of the liver for Zn, Cu, Cd, and Pb compared to the muscle tissue. In contrast, the liver showed similar or lower concentrations of Hg and As than the muscle. These findings of the liver's higher capacity for concentrating Zn, Cu, and Cd agree with previous reports on the sequestrating-detoxifying function of the liver, which involves the action of the protein (Cd, Zn)-metallothioneein [16; 17; 18]. The liver's high capacity for metal accumulation has been documented extensively in cypririids for these three metals [17; 19] and in several families of catfish [20; 21; 22; 23]. The comparison of the liver's accumulation capacity for Cu and Zn between the two species analyzed showed that for the carp, it was 10 times greater than that of the catfish. The findings were observed in both the experimental and the control groups, and the results disagree with previous reports, since a higher capacity in catfish liver compared to _Cypriidae_ species has been reported in wild fish in natural environments [24; 25]. The explanation of the higher concentration obtained in the carp in our study could be attributable to two factors. Studies of fish in the same aquatic environment have reported feeding behavior and trophic position as the main sources of metals [26; 27]. In our work, however, \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Metal**} & \multirow{2}{*}{**Fish**} & \multicolumn{3}{c}{**Control Group**} & \multicolumn{3}{c}{**Experimental Group**} & \multirow{2}{*}{**Reference**} \\ \cline{3-3} \cline{5-8}  & & **Conc.** & & & **EWI \({}^{*}\)** & \% PTWI & **Conc.** & **EWI \({}^{*}\)** & **\% PTWI** & **PTWI \({}^{\ddagger}\)** \\ \hline Cu & Carp & 1.45 \(\pm\) 0.21 & 0.004 & 0.12 & 2.28 \(\pm\) 0.18 & 0.007 & 0.19 & \\ \cline{2-8} (mg/kg) & Catfish & 0.63 \(\pm\) 0.42 & 0.002 & 0.05 & 1.09 \(\pm\) 0.80 & 0.003 & 0.09 & \\ \hline Zn & Carp & 10.08 \(\pm\) 3.07 & 0.029 & 0.41 & 12.16 \(\pm\) 3.64 & 0.035 & 0.50 & \\ \cline{2-8} (mg/kg) & Catfish & 6.93 \(\pm\) 1.11 & 0.020 & 0.28 & 6.78 \(\pm\) 1.02 & 0.019 & 0.28 & \\ \hline Cd & Carp & 3.86 \(\pm\) 1.88 & 0.011 & 0.18 & 2.23 \(\pm\) 1.36 & 0.006 & 0.11 & \\ \cline{2-8} (mg/kg) & Catfish & 1.40 \(\pm\) 0.56 & 0.004 & 0.07 & 1.23 \(\pm\) 0.37 & 0.004 & 0.06 & \\ \hline Pb & Carp & 18.85 \(\pm\) 2.85 & 0.054 & 0.22 & 11.97 \(\pm\) 4.98 & 0.034 & 0.14 & \\ \cline{2-8} (mg/kg) & Catfish & 8.97 \(\pm\) 3.02 & 0.026 & 0.10 & 13.03 \(\pm\) 1.93 & 0.037 & 0.15 & \\ \hline As & Carp & 98.05 \(\pm\) 45.76 & 0.280 & 1.87 & 57.01 \(\pm\) 13.55 & 0.163 & 1.09 & \\ \cline{2-8} (mg/kg) & Catfish & 30.54 \(\pm\) 8.74 & 0.087 & 0.58 & 32.39 \(\pm\) 14.74 & 0.093 & 0.62 & \\ \hline Hg & Carp & 0.98 \(\pm\) 0.91 & 0.003 & 0.18 & 3.44 \(\pm\) 0.93 & 0.010 & 0.61 & \\ \cline{2-8} (mg/kg) & Catfish & 19.78 \(\pm\) 0.82 & 0.057 & 3.53 & 27.46 \(\pm\) 10.04 & 0.078 & 4.90 & \\ \hline \hline \end{tabular} \({}^{*}\) Estimated weekly intake for a 70 kg person (ug/kg bw per week). \({}^{\ddagger}\) Provisional Tolerable Weekly Intake (ug/kg bw per week) [8].  
\end{table} 
Table 5: Mean concentration (ww) of metals in fish muscle at consumption size in experimental and control groups. Estimated weekly intake (EWI) and contribution to Provisional Tolerable Weekly Intake (%PTWI) through consumption of cultured fish. both species cultured in Lake Chapala were fed the same commercial food in the same cage, so they had only limited access to food from the environment. As is observed in the results section, metal concentrations in the commercial food were low, so under conditions in which the diet of the fish is controlled, their natural feeding habits and their effect on metal accumulation will not be reflected. On the other hand, diverse studies have reported that the age of the fish correlates positively with metal accumulation [24; 28].