Dictionary of Ichthyology  

carp streamer = a carp-shaped wind sock flown in Japan on a national holiday called "Children's Day" (5 May). They are flown in the breeze to honour sons and to hope they grow up strong and healthy. The wind socks are made by drawing carp patterns on paper or  cloth and are a few centimeters to meters long, the longest having been 100 metres. The Japanese name is koinobori.

Wikimedia Commons: http://commons.wikimedia.org/wiki/File:Carp_streamer.jpg

Canadian Museum of Nature