A bait ball, or baitball, occurs when small fish swarm in a tightly packed spherical formation about a common centre. It is a last-ditch defensive measure adopted by small schooling fish when they are threatened by predators. Small schooling fish are eaten by many types of predators, and for this reason they are called bait fish or forage fish.

For example, sardines group together when they are threatened. This instinctual behaviour is a defense mechanism, as lone individuals are more likely to be eaten than large groups. Sardine bait balls can be 10–20 metres in diameter and extend to a depth of 10 metres. The bait balls are short lived and seldom last longer than 10 minutes.

However, bait balls are also conspicuous, and when schooling fish form a bait ball they can draw the attention of many other predators. As a response to the defensive capabilities of schooling fish, some predators have developed sophisticated countermeasures. These countermeasures can be spectacularly successful, and can seriously undermine the defensive value of forming bait balls.

Bait may refer to:

A ball is a round, usually spherical but sometimes ovoid, object with various uses. It is used in ball games, where the play of the game follows the state of the ball as it is hit, kicked or thrown by players. Balls can also be used for simpler activities, such as catch, marbles and juggling. Balls made from hard-wearing materials are used in engineering applications to provide very low friction bearings, known as ball bearings. Black powder weapons use stone and metal balls as projectiles.

Although many types of balls are today made from rubber, this form was unknown outside the Americas until after the voyages of Columbus. The Spanish were the first Europeans to see bouncing rubber balls (albeit solid and not inflated) which were employed most notably in the Mesoamerican ballgame. Balls used in various sports in other parts of the world prior to Columbus were made from other materials such as animal bladders or skins, stuffed with various materials.

As balls are one of the most familiar spherical objects to humans, the word "ball" is used to refer to, or to describe, anything spherical or near-spherical.

Casey Martin (born June 2, 1972) is a former American professional golfer and the current college golf coach of the University of Oregon.

Martin was born in Eugene, Oregon and still resides there. He was educated at Stanford University, where he was initiated into the Sigma Chi fraternity and was briefly a teammate of Tiger Woods. He was a three-time all Pac-10 and was a member of the University's NCAA Championship team in 1994. He won the 1993 Sahalee Players Championship. He turned professional in 1995.

Martin suffers from a birth defect in his right leg known as Klippel Trenaunay Weber syndrome. Martin successfully sued the PGA Tour in 2001 for the right to use a golf cart during competition under the Americans with Disabilities Act. Among the attorneys representing him was Martha Lee Walters, a 2006 appointee to the Oregon Supreme Court. During the years that the suit wound through the courts, he enjoyed limited success on the golf course, and throughout, was permitted to use a golf cart. In 1998, he won a Nike Tour event, the Lakeland Classic, in a playoff, thus assuring himself of remaining on the tour the following year and securing a five-year exemption from the first round of Qualifying School (Q-School), the competition whereby golfers seek to secure places on both the PGA Tour and the Nike Tour (later the Buy.com Tour, and now the Nationwide Tour), the second-level competition. Also in 1998, he attained a career highlight by finishing tied for 23rd at the U.S. Open, and briefly contending for the lead before falling back.

Dave Mercer is a Canadian professional angler, one of the best known anglers in Canada. He is the host of the Dave Mercer's Facts of Fishing Television Series and Dave Mercer's Facts of Fishing Tip Series. He is also the emcee of the Bassmaster Classic and the Elite Series. Some of his main sponsors include Bass Pro Shops and Subway (restaurant).

At the age of 21, Dave Mercer approached a small yet growing TV station with a new concept in mind. Mercer didn't want to make a season of half hour shows. He wanted to make sixty second short clips giving various fishing techniques. His popularity boomed, which eventually led him to making a regular length TV show titled Facts of Fishing.

Beginning in 2011, Dave Mercer has been the emcee for the B.A.S.S. Bassmaster Elite Series, which has been called the "Superbowl" of the angling world. Following his debut at the 2011 Bassmaster Classic, he emceed eight regular-season Bassmaster Elite Series events and hosted the final two postseason events. Dave Mercer signed a two-year deal to extend his role as Bassmaster Elite Series emcee through 2013.