Meeting Abstract
Fishing down sedentary broadcast spawners challenges their reproductive success by depleting natural aggregations that are thought to promote high rates of fertilization. Here I present the first field experiments on fertilization success in the giant sea scallop, Placopecten magellanicus, a commercially valuable sedentary broadcast spawner in the Northwest Atlantic. Building on previous laboratory studies we (1) developed and tested a Nitex mesh chamber to measure relative rates of fertilization success in situ, and (2) assessed fertilization over a range of population densities using 24-h time integrated fertilization assays progressing from dockside field manipulations to natural population in a coastal estuary. Notwithstanding fertilization chamber artifacts, dockside results suggested that density effects might be detectable in more natural populations on the seabed. However, in both manipulated and natural populations spanning 10-fold differences or less, we could not detect a significant effect of density or nearest-neighbor distance on fertilization. We suspect that scallops in the field populations were not spawning synchronously on any given 24-h fertilization trial. If true, differences in fertilization may only be detectable across population density gradients in the event of mass, synchronous, spawning, or across more dramatic differences in population density that we could only produce in dockside manipulations.
