By Rob Nuemann
From the Lab—Individuals of certain species of fish have been shown to fall into lefty and righty categories. Caused by asymmetry of the left and right sides of the body, laterality has been found in cichlids, largemouth bass, bluegill, and others, where all individuals can be classified as either righty or lefty. In some species of African cichlids, for example, the mouth opening is positioned slightly to the left or right rather than centered. Asymmetry in muscle and bone development also leads to righty and lefty fish. Muscles are more developed on the left side of the body on a lefty individual, causing the body to take on a “C” shape with the left side of the head farther forward, whereas righties take on the opposite shape.
A recent study examined how being either lefty or righty affects feeding mechanics of largemouth bass.* Researchers expected that as a lefty bass struck and overtook a bait it would move to the right and get hooked on the left, while a righty would move left and get hooked on the right.
In one experiment, seven bass were held in tanks where a test angler lured bass with Yamamoto Kut Tail worms baited on 1/0 Gamakatsu 314 worm hooks. Cameras recorded strikes and hooking while bass and the angler could not see each other. Twelve hookups showed that hooks were set more often on the side opposite the head movement direction. Most bass were hooked on the right side of the mouth with a left move.
In a second experiment, largemouth bass were stocked in a pond and test anglers fished for them with lures. When a bass was caught, the position of the hook was recorded. After the 24-day experiment, all bass were classified as either righty or lefty based on skull laterality measurements. Individuals were hooked more often on the same side of their mouths as their laterality, indicating that fast start direction during taking a bait was affected by laterality. The researchers conclude that hooking location is a reliable indicator of whether a bass is a lefty or righty.
*Nakajimi, M., T. Yodo, and O. Katano. 2007. Righty fish are hooked on the right side of their mouths—observations from an angling experiment with largemouth bass Micropterus salmoides. Zoological Science 24:855-859.