State of Menidia jordani (Pisces: Atherinopside) in la goleta reservoir, Estado de México

This research analyzes the state of the silverside Menidia jordani (Pisces, Atherinopsidae) in La Goleta reservoir, Estado de Mexico, and its population changes since 1998 when it was first recorded in the reservoir. To do this, visits were made in 1998, 2007 and 2008 during the dry and rainy seasons. Fish were caught with a 30.0-m-long dragnet, with a 1.5-m-drop and 8.0-mm mesh. They were then fixed with 10% formalin, taken to the laboratory and identified. The results show that the greatest abundance of M. jordani was recorded in 1998 (3,000 fish 1000 m(-2)), while the lowest abundance occurred in 2008 (5 fish.1000(m-2)). It is concluded that these variations are due to the presence of exotic species like the common carp (Cyprinus carpio) and the golden carp (Carassius auratus), which compete with the silverside. In addition, the presence of a carnivorous species (Micropterus salmoides) and the tapeworm (Bothriocephalus acheilognathi) influenced the decline in this fish, as did the dumping of raw sewage into the reservoir system.