Meeting Abstract
116.2 Tuesday, Jan. 7 10:30 Range Extensions: Larval Dispersal, Assisted Migration or Both WOODIN, SA*; WETHEY, DS; DUBOIS, S; Univ. of South Carolina, Columbia; Univ. of South Carolina, Columbia; IFREMER, Brest, FR woodin@biol.sc.edu
The tube-building polychaete Diopatra biscayensis has a 400 km gap between populations in the Bay of Biscay and the English Channel. Alternative hypotheses for establishment of the English Channel population are: 1) larval transport by ocean currents and 2) human intervention. A second question is whether the population in the English Channel is self-sustaining and capable of expansion northward. Records of movement of shellfish culture materials between the Bay of Biscay and the English Channel support the hypothesis of assisted migration of juvenile Diopatra. Shellfish operators often work at both sites, moving materials between the two, collecting mussel juveniles on ropes and oyster juveniles on tiles in the Bay of Biscay in areas with large populations of Diopatra, and transporting them to the Bay of Mont-Saint-Michel. Size distributions of populations were used to estimate growth and natural recruitment over a three year period. Results of Lagrangian particle tracking do not support the hypothesis of transport solely by ocean currents over the gap in distribution. Lagrangian transport of larvae could account for no more than 40 km during the larval period (<6 d). Size distributions of populations in the Bay of Biscay in 2010 to 2013 reveal a range of size classes with recruitment evident in most years. In contrast in the English Channel, more than 850 individuals were measured in 2011-2013 but only one juvenile (tube ID < 5 mm) and very few small individuals were seen and only in one population. The populations within Mont-Saint-Michel Bay appear to have very limited expansion capability. The unanswered question is how often successful reproduction or transport by humans occurs since some of the populations are large but without evidence of recruitment. The data are consistent with human assisted migration.
