Biased estimation toward larger size and more males in apple snail populations by trap collection in comparison with collection by quadrat.

概要

論文の詳細を見る
Two methods for collecting snails, by hand in square quadrats of 2.25 m<SUP>2</SUP> and by baited traps, were employed to detect any differences in estimation of snail populations by these methods. Snails were collection at five fixed sites in each of six rice fields from June to August. Collected snails were grouped into three classes : immatures with shell heights < 20 mm and female and male adults with heights ≥ 20 mm. Trap collection gave a lower proportion of immatures and a higher proportion of adults than the quadrat method in any month, and snails of any class collected in the trap-were significantly larger than those collected by quadrat in any month. Collection of larger snails by the trap suggests that larger snails could outcompete smaller ones for bait or could reach the trap from a further distance. The proportion of males collected by trap was not different from that collected by quadrat in June and August, but was significantly higher in July. The male-biased collection may be caused by higher reproductive activity of females emitting sexual pheromones. Thus, the trap and quadrat methods estimate snail populations differently.
九州病害虫研究会の論文