I have been wondering the same thing for years and have not come up with any concrete answer. I do believe any kind of bait in shallow (grunion, smelt, anchovies, etc.) draws the fish in which is always a good thing. If the fish aren't there you're never going to catch them - whether they're hungry or not.
My catches seem to be slightly better around a grunion run but not enough to provide any solid evidence that the grunion run was the reason. It could just be because I fished more around that time.
#5801, "RE: Question for Leapin Bass or..." In response to Reply # 0
I've never really experienced any dramatic change in halibut or white seabass fishing during grunion runs. You'd think it would improve the fishing, but I've never noticed a dramatic change, like that of say the moon phase or weather. Maybe grunion just don't taste good... ;-) -Brian
#5802, "RE: Question for Leapin Bass or..." In response to Reply # 0
I have been in the middle of several runs and did not get bit. I think there was too much bait there. I have heard of guys who do well the last day or day after that right at gray light in the AM. The grunion are scarcer and the fish still show up to feed--hopefully on your swimabit or on grunion you caught and froze from a few nights earlier.