Farms.
With the free Fishing, which I assume everyone got, it also reduces the cost of Pottery.
But the real blessing is in increased growth rate.
Here's a better question. Why Hunting?
See my previous post for "why hunting".
While pottery becomes cheaper once you've research agriculture the reduction in cost is LESS THAN the cost of agriculture. If we needed agriculture anyway then maybe but putting down a few cottages first and thus boosting our science rate will make the time to research agriculture fairly minimal and we can research it just before we need to start building farms on our second or third city.