Feeding behavior of the mussel Mytilus galloprovincialis (L.) in a Mediterranean estuary: A field study

Abstract

The feeding behavior of the mussel Mytilus galloprovincialis was investigated in the field on top of a mussel raft in Alfacs Bay, NW Mediterranean Sea. The experiments were performed in November 2006 and February, April and July 2007 using a flow-through filter feeding device. Total particulate matter (TPM), particulate organic matter (POM) and particulate inorganic matter (PIM) were calculated for the bay water, as well as the feces and pseudofeces of the mussels. These were used with the biodeposition method to estimate several feeding-physiological parameters, such as the clearance rate (CR), rejection rate through pseudofeces production (RP), organic ingestion rate (OIR), absorption rate (AR) and absorption efficiency (AE). The results showed that the characteristics of available suspended matter for mussels in terms of particle concentration (TPM: mg/l) and organic content ( f defined as POM/TPM) ranged 1.03–2.30 mg/l, and 0.48 to 0.73 respectively throughout the study period. This indicates a rather stable feeding environment of low concentrations of high organic content particles despite the wide range of temperatures recorded (from 10 to 26 °C). However, a characteristic of such a variation pattern of particle suspension (TPM and f) was that short-term variations (in the course of days) covered the whole range of annual variation. Accordingly, physiological parameters characterizing both food acquisition and absorption in mussels were found to respond to short-term variations in food regime. Pseudofeces production in mussels was low (less than 5% in most cases) and they tended to reduce their clearance rate instead of increasing their pseudofeces production in response to rising particle concentration. The absorption efficiency was positively related to the organic content of the seston particles. There was also a positive correlation between clearance rate and absorption efficiency. The reduction of clearance, ingestion and absorption rates obtained in July highlights a negative influence of high water temperatures upon feeding and digestive processes of mussels.