Thunderbird. Thanks for that. I had heard the term before but was confused when doing a collective noun quiz and finding 'pochard' among the 'Fish and Insects' section. As I hadn't heard of it as a fish or insect I was curious. Now you've said it's a type of duck I can hit myself on the forehead and say 'Duh'!
Not really ignorant Jan. There is a fish called a pilchard, related to the common sardine. If you curl the i and the l into a circle you get 'pochard' so your fish wasn't too far off :-)