US EPA

7232137 

Journal Article 

Post-settlement alteration of spatial patterns of soft shell clam (Mya arenaria) recruits 

Hunt, HL; Mclean, DA; Mullineaux, LS; , 

2003 

Yes 

Estuaries
ISSN: 0160-8347 

ESTUARINE RES FEDERATION 

LAWRENCE 

72-81 

WOS:000181576900008 

To examine the roles of settlement and early post-settlement processes in patterns of recruitment of the soft shell clam Mya arenaria, abundance of juvenile Mya at three intertidal sites in Barnstable Harbor, Massachusetts, was monitored over two settlement seasons. Two peaks of settlement occurred in 1998 (July and September) and one peak was recorded in June 1999, indicating that a late season settlement event is not a consistent feature at this site. Abundance of recent settlers (i.e., early recruits, < 1 week past settlement) varied significantly among the tidal flats (sites) that were separated by hundreds of meters to kilometers, but not among plots meters apart. Differences in abundance of settlers likely resulted in these differences in early-recruit abundance among sites. Settlement was greatest at the site with the greatest variability in flow speed. Sites also differed to some extent in their sediment characteristics and macrofaunal assemblages, which may influence larval substrate choice. Between-site differences in abundance of Mya decreased after settlement. The rate of decline of abundance varied among cohorts and sites. Comparison of abundance of recent settlers (up to 145,000 m(-2)) to that of juveniles > 3-mm shell length at the end of the settlement season (up to 60 m(-2)) indicated large losses of individuals during the early post-settlement period. This study demonstrates that spatial patterns in Mya abundance can change substantially during the early post-settlement period, and that high mortality rates can result in cohorts contributing little to the population size even when rates of settlement are high.