Indirect effects of clam digging on the viability of soft-shell clams, Mya arenaria L.
Emerson, C.W.; Grant, J.; Rowell, T.W. (1990). Indirect effects of clam digging on the viability of soft-shell clams, Mya arenaria L. Neth. J. Sea Res. 27(1): 109-118
In: Netherlands Journal of Sea Research. Netherlands Institute for Sea Research (NIOZ): Groningen; Den Burg. ISSN 0077-7579; e-ISSN 1873-1406, meer
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| Auteurs | | Top |
- Emerson, C.W.
- Grant, J.
- Rowell, T.W.
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| Abstract |
A series of laboratory experiments was conducted to determine whether non-lethal burial or exposure on the sediment surface could alter the normal living depth of Mya arenaria in sand and mud. After 2 weeks, clams (~ 3 to 7 cm shell length) which were buried under 1 to 15 cm of medium-fine sand were found deeper than the controls, whereas clams (~ 1 to 7 cm length) which were exposed on sand (and had subsequently reburrowed) were able to re-establish their normal living depth. In contrast, clams (~ 1 to 7 cm length) buried under 1 to 15 cm of mud attained their normal living depth within two weeks, but exposed clams (~ 1 to 7 cm length) reburrowed to abnormally shallow depths. An increased likelihood of predation at shallow sediment depths was compounded by the 60% slower reburrowing speed of exposed clams in mud than in sand. An additional experiment determined the approximate depth of burial under which at least 50% of a laboratory clam population could survive (LD50). For small (< 3 cm in shell length), mid-size (3 to 5 cm) and large ( > 5 cm) clams in sand, LD50 values were > 75 cm, > 75 cm and between 50 and 75 cm, respectively. In mud, the LD50 of clams < 5 cm in length was < 25 cm, and between 25 and 50 cm for clams >=5 cm in length. It was concluded that the indirect mortality level associated with commercial and recreational harvesting will be much greater on intertidal mudflats than on sandflats. |
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