Trophic Linkages in Marshes: Ontogenetic Changes in Diet for Young-of-the-Year Mummichog, Fundulus Heteroclitus

Abstract

Transfer of salt marsh production in the form of detritus to surrounding coastal and estuarine areas has been an area of interest for a number of years. The common mummichog, Fundulus heteroclitus has been proposed as an important link in trophic transfer, however little is known about the role of small young-of-the-year (YOY) in this process. To address this lack of information, YOY were collected from the flooded salt marsh surfaces at a lower Delaware Bay site over 2 summers in order to determine ontogenetic shifts in food habits. Young-of-the-year F. heteroclitus were abundant on the marsh surface, and during peak larval recruitment to the marsh, fish densities reached 15 to 30 fish M-2. Multiple cohorts were visible in 1997, indicating up to 4 separate spawning events. Stomach contents for YOY were dominated by detrital-sediment aggregates, harpacticoid copepods, and annelid worms. The food habits changed with size, with the stomach contents of the smallest individuals (6.6 mm < 20.4 mm SL) composed primarily of benthic fauna such as harpacticoid copepods and annelid worms. The stomach contents of larger YOY (20.5 -30.4 mrn SL) shifted to mostly Spartina detritus and sediment aggregate. Thus, YOY F. heteroclitus consume detritus both directly and indirectly (through consumption of detritivore benthic fauna). Prior research has indicated that the YOY are the dominant fish species and life history stage on the marsh surface in both abundance and biomass, with high measures of secondary production. Thus it is likely that the YOY make a substantial contribution to trophic transfer of production from the marsh surface to the surrounding estuary. NR - 56 PU - SPRINGER PI - DORDRECHT PA - PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS