I recently came across a book entitled “High Percentage Fishing: A Statistical Approach to Improving Catch Rates” by Josh Alwine. The author is an engineer and statistician who evaluates data putting popular fishing theories to the test.

One of the subjects he covered was the moon’s affect on fishing. Now this book is specifically focused on bass fishing and doesn’t take into account how other freshwater species are affected by the moon. He also discounts how the moon affects tidal waters. So the study is primarily focused on land-locked largemouth bass. Three different hypotheses were formed that we’ve all heard at one time or another, and I thought you would all be interested to hear the results of these hypotheses put to the test.

Hypothesis number 1: The moon’s gravity affects fishing.

In the sample size of fish caught throughout the year, 7.3% of all fish were caught when the moon hit its peak gravitational impact. When the moon was at its weakest gravitational impact point, 9.0% of the fish were caught. Given the sample size the hypothesis was rejected. In this case a slightly higher number of fish were caught during the weakest gravitational point than at the strongest gravitational point.

Hypothesis number 2: The moon’s light level affects fishing.

17% of fish caught at night were during a full moon period. 14% of fish caught at night were during a new moon period. Once again, the hypothesis is rejected. If the moon’s light had a significant impact on fishing then we’d expect the catch rates to change significantly during the two different types of moon phases.

Hypothesis number 3: Moonrise and Moonset affect fishing.

Based on the sample size with all the fish caught on any given day, 20% of fish were caught during moonrise/moonset regardless of the moon phase. However, moonrise and moonset can often go hand in hand with sunrise and sunset. In the book, the author determines that sunrise and sunset indeed DO have a significant impact on fishing. Therefore, in order to test the moonrise/moonset affects on fishing they had to test catch rates during moonrises/moonsets that occurred during the middle of the day when the sun was neither rising nor setting. When removing the sunrise/sunset factor the 20% figure mentioned earlier dropped to 13%. The catch rate of 13% mirrors the catch rate for any randomly selected hour during the day. Based on the data the hypothesis is once again rejected.

The author concludes that the moon does not significantly affect our fishing. Instead, he believes that fisherman wrongly assign meaning to moonrise/moonset when the truly impactful variable is the low light conditions that happens to coincide with these time periods.

Personally, the author’s theory is hard for me to believe. Perhaps it’s because from my earliest days of bass fishing I was taught to pay attention to moon phases. However, maybe I’ve been biased since day one and I need to approach my fishing with more of an open mind. What do you think of the author’s results?