The removal of kelp farms before the summer and rigorous surveying prior to lease placement may help deter fouling by other invertebrates, but the small marine gastropod Lacuna vincta (family Littorinidae) has proved to be an unpredictable and continuous obstacle for kelp farmers on both U.S. coasts. Though the snails themselves are easy to brush or wash off kelp blades, their eggs become embedded in the blade’s surface, making removal post-harvest labor-intensive, time-consuming, and ultimately, impractical. Current management strategies, such as harvesting early, are costly for farmers who often get paid in dollars per pound.
Not much is known about the snails’ interactions with kelp farms as most research has been done on L. vincta grazing and settlement in wild kelp communities. We aim to pinpoint the timing of L. vincta settlement on kelp farms in Maine through frequent visual inspections of grow lines throughout the winter growing season. Additionally, using a novel L. vincta PCR primer, we are testing marine environmental DNA methodology as a possible tool for early detection of this species.
Snail distribution is patchy even within kelp farms that have large infestations. Work with industry partners has focused our research to include snail preference experiments to determine if the biology of the kelp itself is a factor in snail preference. In the first experiment, farmed sugar kelp (Saccharina latissima) was removed and kept in two treatments: one treatment where it was fed f/2 nutrient solution, and another treatment where kelp was deprived of nitrates. L. vincta snails were then exposed to identical squares of each. The second experiment exposed the snails to identical squares of sugar kelp and skinny kelp (Saccharina angustissima), two commonly farmed species in Maine. Snail herbivory and settlement preference over time were recorded for both experiments. Results suggest that there may be a sweet spot between peak health and stress in kelp at which snail preference changes. Preliminary results for the second experiment suggest that snails prefer skinny kelp, however more trials are needed.