As you can see the avatar has been changed. The new image is of a salmon leaping so that it grasps its own tail.
The salmon was a symbol of wisdom and knowledge in Irish myth. The Fiannaidheacht (Fenian cycle of stories) include a tale where Fionn mac Cumhaill (anglicised to Finn McCool) was set by his master, the druid Finnegas to catch the salmon of knowledge who lived in a pool on the Boyne. Whoever ate the salmon would gain all the world’s knowledge. Finn caught the fish and was set to cook it for his master. However Finn burned his thumb on the fish and instinctively put the thumb into his mouth, swallowing a tiny piece of fish, and gaining the knowledge.
The image is based on a drawing in a manuscript (Royal MS 13 B VIII, c. 1196-1223) in the British Library. The manuscript is a copy of Gerald of Wales’ Topography of Ireland (pdf), with other works of his, dedicated to King Henry II. There is a blog post here, including the original image of a salmon leaping.