  We study the vortex-dynamics of a BaFe{1.82}Ni_{0.18}As_2 crystal with Tc = 8
K, by measuring flux-creep over the second magnetisation (or fish-tail) peak
for both H//c-axis and H//ab planes. Magnetic relaxation data show an
anomalously long initial stage of relaxation, lasting approximately10 minutes
for H//c-axis and 2-3 min for H//ab, resembling a transient effect with a lower
relaxation rate, which is followed by the usual log(time) relaxation.
Interestingly, study of the relaxation rate R vs H for both stages of
relaxation and for both field directions, are featureless over the field range
associated with the fish-tail. The same trend was confirmed by plotting R vs T
obtained from flux-creep data measured as a function of temperature for a fixed
field (H//$c-axis). A plot of the activation energy U(M,T) calculated from the
time relaxation of the magnetisation at a fixed field also shows a smooth
behavior further supporting the view that the fish-tail peak is not associated
with a crossover in vortex pinning regime within the collective pinning
scenario.
