It seems your bass is just an overanxious father, doing his best - in these parlous times - to protect his young from the dangers of the big, bad water world.

The timing was the tipoff for our fish experts. According to Eric McIntyre, a fisheries biologist with the Ministry of Natural Resources (MNR), in late spring, male bass (largemouth and smallmouth) use a tail-lashing technique to clear a nest area on the lake bottom. Once the eggs are laid and fertilized, it's the male that guards and defends them and the newly hatched fry until they disperse.

You may observe this defence activity as early as May if your lake warms early, or as late as July if it's a cooler, spring-fed lake. Normally the fish will fake an attack, veering off at the last moment - but occasionally one will actually connect. Mary Burridge, assistant curator for ichthyology at the Royal Ontario Museum in Toronto, remembers being nipped on the ankle while at her family's cottage on Kawagama Lake. "I was amazed at his aggression - he was so much smaller than I was," she recalls. A nip is as bad as it gets, though, because bass "teeth" are really just rows of bony points that can't do human skin any serious damage.

In your case, the nest must have been close to the dock - a typical spot for a bass to choose. Ichthyologist Brian Coad, at the Canadian Museum of Nature in Ottawa, says you can often spot a nest on the lake bottom. Look for a bare area, roughly circular and as large as 1.8 metres across.