Geoff Thomas: Fish come when moons line up

This 10kg 'old man snapper' was caught at night in moonlight. Photo / Geoff Thomas

To many ancient civilisations the moon and the sun were deities to be worshipped, and in some cases appeased with sacrifices. They also knew the influence of the moon on natural rhythms and planned the planting and harvesting of crops around such cycles.

These cycles are now published and in this country the best known is the Maori fishing calendar. One of the biggest internationally is the Solunar Tables created by an American, Richard Alden Knight, and used by hunters and fishermen in the United States. A local version is published every year by Oceanfun Publishing in Blenheim, which also produces the Tide Times Calendar which covers bite times and best/worst days for fishing.

The principles are the same everywhere - that the behaviour of animals and fish is influenced by the phase and the position of the moon.

The moon exerts gravitational pressures on the Earth, and to a lesser extent so does the sun, hence the tidal fluctuations. The oceans can be likened to a huge jelly which is sucked out on one side and conversely retreats on the other side, thus creating tidal flow. Then it wobbles back in the other direction and huge volumes of water again move, more so at each end of the planet than in the middle. So tides close to the equator have little variation while those closer to the poles rise and fall to great heights. While our tides in this country will vary by up to 4m, the world's largest documented tidal range is 16m, which occurs in the Bay of Fundy on the east coast of Canada. But what is of interest to fishermen is : When is the best time to go fishing?

For snapper it is all about tides, and on the east coast the best fishing occurs on the big tides, with the reverse on the big west coast harbours. This is because of the volume of water which flows in and out of the Manukau and Kaipara Harbours, and the ability to get terminal tackle to the bottom in the powerful currents.

The biggest tides of every month coincide with the full moon for half of the year, and the new moon for the other six months. This is determined by the distance from the Earth to the moon, as it moves towards and away from the equator.

The position of the moon also affects feeding patterns, and the lunar calendars all identify two main feeding periods in every 24-hour period.

These occur when the moon is directly overhead, with the major feeding period, and directly underfoot, for the minor period. Their duration varies but can last from 20 minutes to over an hour.

This is well demonstrated by the activity of sheep and cattle in fields. Sometimes the stock in paddocks by the road will all be up and feeding, while at other times they will be lying around under a tree. This could occur at any time of the day.

Some anglers swear by these "bite times" and plan their outings accordingly. If you do not have a bite times calendar you can calculate the feeding periods by simply checking the moon rise and moon set times, which can be found in the NZ Herald in the weather section. Figure out the halfway point between these two times and that will give you the prime period when the moon is directly overhead. The minor period will be 12 hours later when it is directly underfoot on the other side of the planet. These times will then advance by about one hour each day; so can be calculated in advance.

Unfortunately these "bite times" are not absolute. Local factors like the state of the tide and the weather also come into play. For example, fish feed actively before a storm and for some reason south-easterly winds put them right off their tucker. This applies to trout as well as fish in the salt.

Then there is the phase of the moon, which affects the good days/bad days on the lunar calendar. In general terms the best two weeks of each month fall around the new moon, while the slowest fishing will be in the two weeks bracketing the full moon. The original Maori calendar suggests fishing will start improving three days after - or before - each full moon. It is universally agreed the three or four days either side of the new moon are the best of the month.

But if the turn of the tide (always a good time) and the major bite time occur at dawn on one of the days just after the new moon, then everything is lined up for a successful outing.

Otherwise, try fishing at night on a bright moon. The fish have to feed some time.