Schooling in fish  (Page 5/10)

Another interesting cost is seen in only a few species. The herring (Clupea harengus) does not change its schooling patterns once it gets into adulthood, despite environmental change. Therefore, in certain environments it can become extremely costly to school if there are conditions that favor solitary individuals (Corten 2001), such as low predator densities.

Foraging

The positive effect of schooling on foraging efficiency has been well documented in both observational and experimental trials. Experiments with the three spined stickleback ( Gasterosreus aculeaius ) show individuals within a school find food quicker and consume more of it than they would if they foraged alone (Kaitala and Ranta 2006). This has also been seen in goldfish ( Carassius auratus ) and minnows ( Phoxinus phoxinus ), two species who do not always school, but when they do, are able to find food sooner (Magurran et al 1982). It is easier to feed in a school because individuals do not need to exert as much energy on anti-predatory activities and are more likely to spot food based upon overlapping sight lines. This increases the chances of eating, and therefore surviving to mate, which is ultimately fitness. The increased success of foraging often helps solitary individuals and other species, who search for schools, follow them to sites with food, and copy their feeding and anti-predatory behavior. The ability of others to eavesdrop on these behaviors indicates that these behaviors do greatly benefit the individuals in the school (Olla and Ryer 1990). An interesting aspect of foraging within schools was discovered in the juvenile roach ( Rutilus Rutilus ): the most nutritionally deprived fish in an experimental setup regularly led the school, and when nutritional deprivation was equal within a school, those at the front ate the most. These findings strongly indicate that schools are functionally preferred (Bumann et al 2004) and are evidence of selfish behavior: the most fit individual will be able to get to the front of the school when nutritional deprivation is equal, and will benefit the most (Hamilton 1970). It is important to understand that one reason more fit individuals will allow more nutritionally deprived individuals to eat first, or fish in the back will still school if they get food last, is often because of schooling within kin groups. Fish do have the ability to recognize others, as discovered through experiments across various species (Griffiths 2003). This recognition suggests a mechanism may exist for kin recognition and knowledge of one’s spatial position with a school. For female guppies ( Poecilia reticulate ), it takes 12 days to get to know one another. This ability to recognize, once established, determines schooling preferences, which are then maintained. (Griffiths and Magurran 1997). This previous knowledge is valuable in reciprocal relationships, such as joint foraging, where it is useful to remember who cooperated withother individuals in previous interactions. In terms of kin recognition, schooling with kin is always better for your own fitness than schooling with strangers, and the ability to remember individuals can assist in this type of behavior (Griffiths 2003). Schools often do exist between strangers or even different species, but these schools appear less stable than familial schools because of increased competition for safe positions and resources (Wolf 1985).