From 1978 to 1982, only water bodies in the central
area of the park were sampled. These samples revealed
that no crayfish were present in the sandy areas or at the
marsh’s edge. Procambarus clarkii was first detected
in 1983–1984, in two semi-permanent water bodies at
the marsh’s edge. In subsequent years, crayfish were
also found in six additional ponds bordering the marsh
and were first observed to occupy ponds within the
sandy area in 1988, a very rainy year (Fig. 1A).