Interesting to know about the Maori fishing calendar.
As Chinese, we have the similiar theory/calendar for fishing, and over the past few months, I observed that there are some truths to it.
Our theory is:
There are difference between a "living tide" and a "dying tide". "Living tide" is 3 days before and after the first day of the Chinese month (Day when it's a new moon), and again, 3 days before and after the 15th day of the Chinese month (Day when it's a full moon).
Therefore there are 2 weeks of 'good fishing', they are the 'living tides' weeks. The 'dying tide' weeks are the two weeks in between, this make up the 2 week of good fishing and 2 week of bad fishing in a month.
These Chinese fishing calendar, Maori calender are inline with the Western solunar theory, that when there is a new or full moon, tides move quicker than therefore the water gets more oxygenated and thus fishes are more wanting to eat.
Having tried it myself, there are some truths to it. When I tried walking out to fish on a 'bad week' I generally don't get much fish, e.g. 1 or 2 small ones max. In the 'good week' I generally do get at least 2~3 fish more, although some 'good days' can be bad too due to the wrong wind direction, wrong tides, or, simply my bait isn't appealing enough. Having said that, small bait fishes take about anything I offer to them, while I find that bigger fish tend to be much more picky...
At the end, just go and drop that line into the water...