CHANNEL CATFISH AS POTENTIAL SEED DISPERSAL AGENTS FOR RED MULBERRY AND SWAMP 
PRIVET IN THE MISSISSIPPI RIVER.

John H. Chick, Robert J. Cosgriff, and Lori S. Gittinger.
Illinois Natural History Survey, Great Rivers Field Station, 8450 Montclair 
Ave.,  Brighton, IL 62012

Ecologists believe the interaction between water and land is a key process 
structuring the ecology and productivity of river-floodplain systems.  River 
biota display a variety of foraging and life history adaptations that capitalize 
on seasonal flood-pulse cycles.  For example, seed dispersal by fishes is well 
documented in tropical river-floodplain systems, though relatively few examples 
are known from temperate systems.  During the spring floods of 2001, we received 
reports from state researchers who had collected channel catfish (Ictalurus 
punctatus) in Pool 26 of the Mississippi River that had consumed great 
quantities of red mulberries (Morus rubra).  A pilot study was initiated to 
collect channel catfish and determine the viability of any mulberry seeds 
consumed.  We captured 24 channel catfish from an island backwater, 54% of which 
had consumed mulberries.  Over 350 red mulberry seeds were recovered from the 
lower digestive tract of these fish and planted in seed trays.  After a period 
of 14 days, 72% of these seeds successfully germinated.  We repeated this effort 
during the spring flood of 2002.  We captured 30 catfish, 40% of which had 
consumed mulberries and 30% of which consumed swamp privet (Forestiera 
acuminata) seeds.  For both red mulberries and swamp privets, we conducted 
common garden, randomized block experiments to compare germination success 
between seeds consumed by catfish with seeds harvested directly from plants.  
Significantly more mulberry and privet seeds germinated after being consumed by 
catfish compared to seeds harvested from plants.  For mulberries, 78% of seeds 
consumed by catfish germinated after 10 days compared to 62% from plants.  The 
difference was more pronounced for privets, 55% of which germinated after 10 
days when consumed by catfish compared to 17% from plants.  Our results suggest 
that catfish may play a role in dispersing red mulberry and swamp privet seeds 
in the Mississippi River.

Keywords:  channel catfish, seed dispersal, red mulberry, swamp privet, 
Mississippi River