To catch these I would recommend a Lu Shang Rod and a minnow. If you get a "!!!" sign and a "positive you don't have enough skill" or "terrible feeling" then it will always be a squid. Sometimes it will be if it says "Fairly sure you don't have enough skill" but it is not always 100% when you get this message.
So, following Wiegraf's comment, I went out to the specified spot and gave it a whirl at 35 fishing with a composite rod. I actually managed to hook and /reel in/ 9 Gigant squids out of 2 stacks of sliced cod and one minnow, but only one of those did not result in a line break.
Conclusion; composite isn't good enough to pull up Gigant Squids. You really need a Lu.
