Trends of duck-capture at three duck-netting ponds, since 1929

Abstract

Numbers of all ducks caugth in the three duck hunting refuges of Shinhama, Koshigaya and Hama-Rikyu since 1929 were tabled here. The catch rates (number of catch for one species/number of total catch x 100), by year or by refuge show interesting alternation in the predominat species in the duck catches. After around 1965 the pintail Anas acuta has remarkably ascended in the catch rate, becoming predominant, at the both refuges of Shinhama and Koshigaya. On the contrary, the teal Anas crecca, which was formery predominant, has remarkably decreased at the said refuges. Also, the results of duck censuses at the Shinobazunoike show similar phenomenon, increase of pintails and decrease of teals in recent years. Besides the above, the recent increases of wigeons Anas penelope and pochards Aythya ferina in Shinhama, shoverllers Anas clypeata in Koshigaya and pochards in Shinobazunoike should be noted.