  Using HIPASS data, we have searched for HI in a ~25x25 sq.deg. region centred
on the Fornax cluster. Within a velocity search range of 300 - 3700 km/s and a
lower flux limit of ~40 mJy, 110 galaxies with HI emission were detected, one
of which is previously uncatalogued. None of the detections has early-type
morphology. Previously unknown velocities for 14 galaxies have been determined,
with a further 4 velocity measurements being significantly dissimilar to
published values. Identification of an optical counterpart is relatively
unambiguous for more than ~90% of our HI galaxies. The galaxies appear to be
embedded in a sheet at the cluster velocity which extends for more than 30 deg
across the search area. At the nominal cluster distance of ~20 Mpc, this
corresponds to an elongated structure more than 10 Mpc in extent. A velocity
gradient across the structure is detected, with radial velocities increasing by
\~500 km/s from SE to NW. The clustering of galaxies evident in optical surveys
is only weakly suggested in the spatial distribution of our HI detections. Our
results suggest a considerable deficit of HI-rich galaxies in the centre of the
cluster. However, relative to the field, there is a 3(+/-1)-fold excess of
HI-rich galaxies in the outer parts of the cluster where galaxies may be
infalling towards the cluster for the first time.
