News and Science
Fish Are Capable of Human-Like Logic
This is a copy of an article that was published in the Aquarium Fish International. I submitted it for publication in the Aquabits section of their magazine. It is the first article that I ever had published, and is based on an article/news item written by Robin Lloyd. Even though it’s a low sodium article (freshwater) I found it fascinating that fish are able to use a type of logic called Transitive Inference. The original article is below:
Researchers at Stanford University have shown that African cichlids are capable of using logical reasoning at level similar to 4- or 5-year old humans to determine social pecking orders. As many aquarists already know, cichlids often spar to establish hierarchical dominance and delineate territories. Stanford researchers allowed five fish to establish a hierarchy (labeled A, B, C, D, E). The A fish defeated B, B defeated C, C defeated D and D defeated E. “Bystander” fish were allowed to watch the selected interactions from the center of the tank, in a transparent, protected enclosure. “Bystander” fish were then forced to make a decision about which fish they would share tank space with. Despite the fact that two fish to choose from may have never directly fought (example Fish A and Fish E) the bystander fish typically chose the weaker fish (D or E) as companions. It is thought that these experiments demonstrate the cichlids’ ability to use transitive inference (TI) to determine that a D or E fish is a more suitable companion than an A or B. TI reasoning is commonly used as a developmental benchmark in 4- and 5-year old children and has also been demonstrated in monkeys, rats and birds.
Works Cited
Lloyd, Robin. “Fish capable of human-like logic: Freshwater cichlids have reasoning capacity of 4- or 5-year old child”.
http://www.msnbc.msn.com/id/16796139/
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Fish Have the Ability to Count….to 4
This is the second submission that was published in Aquarium Fish International. The article highlights the research findings of a study in Italy where scientists determined that mosquito fish are able to count up to four. That just still seems so awesome to me.
Scientists in Italy published evidence that fish are capable of counting. Researchers at the University of Paudua demonstrated that female mosquito fish, when pursued by a male, fled his attentions and joined the largest nearby shoal. These data suggested the fish could differentiate between a large shoal and a smaller shoal, but the first experiment did not determine how precisely the fish could count. In a follow-up set of experiments, the team determined that the mosquito fish would consistently pick a group of four fish over a group of three fish and a group of three fish over a group of two fish, and a group of two fish over a single fish, demonstrating the fish’s ability to clearly differentiate between one and four fish. The fish, however, were not able to distinguish between larger groups of fish unless the larger shoal was at least two times the size of the alternate. (For example, the mosquito fish would preferentially choose a shoal of sixteen fish over a shoal of eight fish, but could not consistently distinguish between shoals of twelve and eight). The researchers state that the mosquito fish’s ability to count puts them on par with human infants six to twelve months of age, and is similar to the abilities of monkeys and dolphins.
Published in Aquarium Fish International, September 2008: page 18
Summary based on an original article published here:
Clover, Charles. Editor. “Fish Can Count to Four-but No Higher”. Telegraph. Retrieved April 1, 2008. http://www.telegraph.co.uk/core/Content/displayPrintable.jhtml;jsessionid=pb3lg1cbiej
Cleaner Fish Reduce Aggression in Captive Aquaria
Aggression among fish is a natural behavior. This behavior tends to get exacerbated in the confines of a community tank, where aquarists mix specimens in a confined space. Researchers from the University of Queensland may have found a solution to the problem. Their research demonstrates that the presence of cleaner fish, specifically lambroides dimidiatus, in a captive aquarium, reduces the amount of aggression in that aquarium. Cleaner fish typically set up ‘cleaning stations’, where ‘client’ fish have parasites removed which are then eaten by the cleaner fish.
The Australian researchers measured how frequently predator fish chased prey fish. They observed that predators chased prey approximately two thirds less frequently in aquaria with cleaner fish than in aquaria without. The decrease in aggression appears to be tied to the cleaner fish’s behavior of touching the ‘client’ fish with their fins. Cleaner wrasse touched predator fish at least three times more than non-predator fish. Also, the more often they touched their ‘clients’ with their fins, the more peaceful the tank was.
The research does not claim to be a cure-all for aggression, or to be a solution for mixing incompatible species. It does, however, suggest that cleaner fish have a calming effect on the tank’s inhabitants.
Published in Aquarium Fish International: January 2009, page 18
Based on the following article
http://environment.newscientist.com/article.ns?id=dn14260&print=true
Clownfish Can Find Their Way Back to Their Reef Using Sense of Smell
This article was originally published in Aquarium Fish International, February 2009: page 18
After clownfish hatch from their eggs, they spend about 10-12 days floating freely in the ocean, as pelagic larvae. After that time, they often return to the reefs close to shore, where they were born. The mechanism through which the fish find their way back home has long been a mystery to scientists. Researchers studying the percula clownfish, Amphiprion percula, have recently found that the clownfish may be attracted to smells in the seawater. In the waters off New Guinea, percula clownfish inhabit shallow water reefs under the canopy of the New Guinea rainforest. In a study published by the Royal Society B, scientists showed that clownfish were preferentially attracted to water samples treated with anemones or leaf litter over control water samples—suggesting that ‘scent’, or other chemical markers are what allow clownfish to find their way home, after undergoing metamorphisis at sea. While olfactor sensation (sense of smell) has been an acceptable theory of how migratory fish find their way home, terrestrial causes of scent, like rainforest leaf litter have only recently been considered. The scientists also demonstrated that even laboratory raised clownfish shared the preference of swimming towards the scented water.
Based on an articles written by:
Choi, Charles, B. “Scientists Learn How Nemo Finds His Way Home”. August 26, 2008.
http://www.livescience.com/animals/080826-nemo-home.html
Dixon, et al. “Coral reef fish smell leaves to find island homes”. Proceedings of the Royal Society B. Published online: July 2008. http://journals.royalsociety.org/content/b0081qj3k3268j34/fulltext.pdf?page=1
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