Changes in distribution and decrease in numbers during migration of the bivalve Macoma balthica

Abstract

The population development of the 1998 year class of the bivalve Macoma balthica was studied by repeated sampling of a tidal flat area in the eastern Dutch Wadden Sea from May 1998 to August 2000. The juveniles migrated twice, once in mid-1998 from their primary settlement locations in the low sandy intertidal to the nursery in the high intertidal (spring migration, 25% of all juvenile M. balthica relocated from low to high intertidal) and once in late 1998/early 1999 from the nursery to the low intertidal and the subtidal (winter migration, between 8 and 15% of all 0-group (less than 1 yr old) M. balthica relocated from high to low intertidal). During winter, M. balthica migration was most intensive at the lowest temperatures. Relative to the abundance on the tidal flats, the 1+ group (older than 1 yr) M. balthica (i.e. from the second summer onwards) were rare in the tidal channels of the Wadden Sea and were only slightly more common in the North Sea adjacent to the tidal inlet. During both the spring and winter migration, many bivalves disappeared from the tidal flat population. This could partly be explained by normal mortality and by emigration to the subtidal channels and the North Sea. The remaining mortality was probably due to the risks inherent in migration: predation during pelagic floating or not reaching the right locations. The number of bivalves that disappeared was very high. In spring, slightly more disappeared than relocated. In winter, > 4 times more bivalves disappeared than relocated. Migration is obviously a very dangerous activity, therefore great advantages must be associated with the nursery use that makes such migrations necessary. An analysis of literature data on the density of M. balthica shows that in the eastern Dutch Wadden Sea, 90% of the population lives in the intertidal, about 10% in the adjacent North Sea, and a negligible fraction in the subtidal channels of the Wadden Sea.

Long-term and large-scale variability in productivity of the tellinid bivalve Macoma balthica on Wadden Sea tidal flats

“…The above relationships are shown for production after the first winter of life, because distribution patterns of Macoma balthica drastically change during their first winter (Beukema & De Vlas 1989, Beukema 1993, Hiddink & Wolff 2002 when substantial parts of the spat migrate from high to low areas and thus complete their production at different stations to those where they lived during their first summer. As Fig.…”

Secretion of a mucous cord for drifting by the clam Meretrix lusoria (Veneridae)

“…In another case, the clam Corbicula fluminea (Muller 1774) secretes a transparent mucous cord from its exhalent siphon and uses this as a sail for drifting (Prezant & Chalermwat 1984). A suggested ecological role of such drifting is to escape from unfavorable environments (Beukema & Vlas 1989, Hiddink & Wolff 2002.…”

“…Some bivalve species drift in the water column and expand their distribution during post-metamorphic stages (see, for example, Bayne 1964, Prezant & Chalermwat 1984, Beukema & Vlas 1989, Hiddink & Wolff 2002. In most cases, such drifts are facilitated by a long byssus thread secreted from the foot, which acts like a sail by increasing hydrodynamic drag (Sigurdsson et al 1976, Lane et al 1985, Sorlin 1988, Beukema & Vlas 1989.…”

Spatial variation in the abundance and condition of the bivalve Nuttallia olivacea in relation to environmental factors and sublethal predation

“…The spatial separation of juveniles and adults can be due to migration and/or mortality. The migration of juveniles to lower areas has been observed in Macoma balthica (Beukema & de Vlas 1989, Bouma et al 2001, Hiddink & Wolff 2002). This change is likely related to habitat suitability, e.g.…”