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Moon phase and largemouth bass.

Lunar connections--The relationships of largemouth bass swimming activity (average distance moved daily) and depth to lunar phases in 20-acre Warner Lake, Ontario, were studied using surgically implanted sonic transmitters and a lake-wide array of acoustic sensors. * Twenty-two bass averaging 16 inches and 2 pounds were monitored from mid-November 2004, through September 2005. Only data collected during relatively stable water temperatures were used in the analyses to eliminate periods when major changes in temperature might have altered fish activity and depth.


A lunar cycle included a complete waxing and waning of the moon from the dark moon to full moon and back. For each of the three complete lunar cycles during cold periods (November 16 to January 26), when water temperature averaged around 39[degrees]F, bass activity and depth were significantly related to moon phase, although response patterns were not consistent across lunar cycles. Largemouth bass were twice as deep and three times less active during cold periods than during lunar cycles coinciding with spring and summer periods (March 10 to September 22).

The three lunar cycles during warmer water also revealed significant differences of activity and depth in relation to moon phase. Bass occupied deeper water as the moon waxed toward full than when the moon waned toward the dark phase. The authors suggest that bass tended to be active deeper when bright light and clear water allowed feeding activity at slightly greater depths.

During the lunar cycle from March 10 to April 7, water temperature averaged 42[degrees]F and bass daily movement increased towards the latter half of the lunar cycle, possibly due to movements toward spawning areas or for prespawn feeding. In water averaging 70[degrees]F to 75[degrees]F after the spawn, daily movements were inconsistent relative to moon phases.

The authors conclude that temperature and many other factors drive fish behavior. Lunar periodicity may not influence the feeding activity of largemouth bass in the predictable manner suggested by solunar calendars. This observation matches the analysis of moon phases relative to big fish catches tabulated in In-Fisherman (April 1992 issue). This study did not assess differences in behavior during solunar major and minors.

In a study I conducted in the 1970s at Lake Travis in Texas, I found that black bass tended to be deeper when the moon was waxing than when waning. Apparently, feeding at night under dark skies forced bass shallower to better illuminate prey and surroundings.


* Hanson, K. C., and 6 co-authors. 2008 Effects of lunar cycles on the activity patterns and depth use of a temperate sport fish, the largemouth bass, Micropterus salmoides. Fish. Mgmt. Ecol. 15:357-364.

Blending Fishery Science with Everyday Fishing


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Title Annotation:Bits & Pieces
Author:Manns, Ralph
Date:Aug 1, 2010
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