  We report on magnetic measurements carried out in a textured
YBa$_2$Cu$_3$O$_{7-\delta}$ and YBa$_2$(Cu$_{1-x}$Ag$_x$)$_3$O$_{7-\delta}$ (at
$x \approx$ 0.02) crystals. The so-called fishtail-effect (FE) or second
magnetization peak has been observed in a wide temperature range
0.4~$<T/T_c<$~0.8 for $\textbf{H}\parallel c$. The origin of the FE arises for
the competition between surface barrier and bulk pinning. This is confirmed in
a non-monotonically behavior of the relaxation rate $R$. The value $H_{max}$
for Ag-doped crystals is larger than for the pure one due to the presence of
additional pinning centers, above all on silver atoms.
