on the subject of best fishing times and tides"
To start off with, an acronym to rival those emanating from the Computer industry.
If you were to sit down at Cape Point and watch the moon from when it rises till it sets, it would approximately half-way through this process pass at right angles over the longitude you find yourself on. It is not exactly half way due to the earth's rotation, but it can be shown that the error is small - less than 5 minutes. If you had a line in the water when the moon traversed your latitude it has been said that your chances of a catch would be enhanced. If the weather and sea conditions, tide, phase of the moon and Neptunes mood would also conspire to be right, you could be in for a big treat.
It is not for me to elucidate here on what makes the position of the moon an important factor in determining a good or even the "best fishing time" - that is dealt with very well in the angling forums by people in the know. Suffice to say that the times of the moons traversal of the local and opposing meridians are indicated on these images and are utilised in conjunction with the tidal data in determining the "best fishing times". These times are also referred to as "moon up" and "moon down" by rock and surf fishing people.
The two Free Floating Downward Pointing Arrows on the upper bar, respectively indicate the times when the moon will be above the local meridian of the location, and when the moon will be above the meridian on the opposite side of the world. Remember that longitude equals meridian. So if you are looking at a tidal image for Durban for example, the white arrow will indicate what time the moon will be right overhead the same longitude on which Durban lies, whilst the blue arrow will show the time of the moon above whatever latitude is on the other side of the world from Durban. With Durban lying around 31 degrees east, the other side of the world from Durban is at 31 + 180 degrees = 211 degrees east. The blue arrow will thus indicate when the moon will be above the meridian shared by the French Polynesian Island of Papeete and Achorage on the Gulf of Alaska. Fish are jumping!
Clearly with the moon above the local meridian, one obtains most light from the moon on that day and least light contribution from the moon when it is on exactly the other side of the world. Obviously local meteorological conditions will determine how much - it could be overcast.
To recap - the white arrow points at the time the moon will be overhead the local maridean. The moon needs to have risen first to be overhead - it follows that the white arrow is always after the moonrise.
In the same way that some days only have a moonrise (no moonset) and visa versa, it does occasionally occur that there is only one Free Floating DP Arrow on the image. Normally in the run-up to a spring tide.
The accuracy of the event is calculated to within 5 minutes and given the scale of the image, the aforementioned fact becomes entirely irrelevant. Nonetheless, although it is close to being 100% correct, you should have your line in the water before the time indicated by either arrow when plotting to go after the big prize.
This is perhaps an opportune moment to remark again on the orange and blue dots on the image. The orange dots indicate the high and low tides still to come later in the year, whilst the blue dots indicate the tides which have already passed. This allows you to pick the tide you want in combination with the time of the moon's traversal. Naturally, a full moon will occur during a night when the moon rises as the sun sets and a new moon will occur when the moon sets with the sun.
And finally, if I were to be squeezed for an opinion, I would personally shy away from attempting to explain this "best fishing time" factor in terms of gravity. That would almost be like trying to explain tides in terms of centrifugal forces - which I would strongly discourage. Important thing is that it works for you.