Sardines?

Mr Debs watched Horizon's fascinating programme on fasting last week and so embarked on it yesterday. Two days of - for men - 600 kcals. Really not a lot for a big fella so after a couple of boiled eggs for his breakfast/lunch we ate fresh grilled sardines for tea with a huge salad. Now, I like fresh grilled sardines but every now and again I hit a woolly one. Why is this? Why the woolly texture? Yuk

Debs