2003 Seattle Annual Meeting (November 2–5, 2003)

Paper No. 12
Presentation Time: 4:35 PM


ARMITAGE, Ian A. and GINGRAS, Murray K., Earth and Atmospheric Sciences, Univ of Alberta, 1-26 Earth Sciences Building, Edmonton, AB T6G 2E3, iarmitage@mac.com

Feeding by the Atlantic sturgeon represents one of the chief erosional and depositional agents on intertidal mudflats within the Bay of Fundy. Each year during the months of May, June, and July, Atlantic sturgeon migrate from the Gulf of Maine into the upper reaches of the Bay of Fundy to spawn. Evidence of their journey is preserved on the mudflats as feeding traces comprising a crescent-shaped impression and a circular open excavation. The configuration of the feeding trace corresponds to the anatomical arrangement of the snout and protractile mouthparts of the Atlantic sturgeon. Four curvilinear runnels radiating from the open portion of the crescent toward the pit correspond to the impression of barbels located between the snout and tube-like mouthparts. Both impressions are produced as the sturgeon removes a cylindrical plug of relatively firm substrate during feeding. The excavated plug contains a variety of organisms that constitute the sturgeon diet including: mollusks, polychaete worms, and amphipods. Analysis of the distribution and orientation of the feeding traces across the mudflat shows that feeding is most intense within 500m of the mean high tide mark and coincides with the maximum concentration of the amphipod Corophium volutator. Within this zone, voluminous quantities of mud and silt are re-suspended by the feeding activity of sturgeon. Extensive development of soupy substrates resulting from the suspension re-deposition of silts and muds at slack tide, as well as the impoundment of seawater within the feeding excavations at low tide marginalize the distribution of firmground burrowers to intertidal channels. Analogies drawn between these feeding traces and similar occurrences in recent and ancient intertidal deposits lends valuable paleoenvironmental insight into the depositional history of mud-dominated sedimentary successions.