I think, mostly, that he just has bad temper, and nothing more serious than that. For example, I get super grumpy in the morning before I've had breakfast, like a completely different person sometimes. Then I have some food and everything is nice again c: Like some people and their coffee I suppose. The squid might have just, you know... missed breakfast, lost progress on something important, or other mundane things. Or maybe he got dumped?
I think I'll raise the chances of rare catches right before the end of the event, in hopes that it'll make people get more of the stuff. Some of the things can be obtained through trading in fish items, don't forget that too! ^_^
Now, on to work again. Hopefully I can finish up today, before I get dead tired again. Oh yeah, another question for you real quick, what do you think of the tank for the hatchery? In general I mean, I'm quite happy with how it turned out and I'm not sure what to do with it after this. Maybe set up a hatchery during events? *Shrug*