Part 2 : Having weighed up the smarts of marine mammals , Becky Hitchin asks if we have been underestimating the brain power of fish
BECKYHITCHIN
Intelligence in the sea
Part 2 : Having weighed up the smarts of marine mammals , Becky Hitchin asks if we have been underestimating the brain power of fish
Everyone of a certain age will remember coming home from a fair , a goldfish in a plastic bag held tight in a small sticky hand , and asking their frazzled parents whether the goldfish got bored swimming round and round . The answer was always that goldfish have a memory of three seconds , so every time they swam round the tank it would be a new and exciting experience . Unsurprisingly , that ’ s not true . Researchers are starting to believe that fish are actually quite clever .
Unlike their larger watery relatives , the marine mammals , fish don ’ t have large brains . However , some fish have brains that can undertake different tasks in both the left and right hemispheres , like dolphins and humans . In laboratory tests , fish have outperformed monkeys , chimpanzees , and orangutans on some complex foraging tasks , and sharks have been able to differentiate shapes like squares , triangles , and rhomboids .
Fish have also been shown to be able to keep track of time and quickly predict the timing of feeding events – faster even than rats have been shown to do . Longterm memory in fish also seems possible . Rock-dwelling gobies have been shown to remember how to get back to their home pools when they were moved nearly 100 feet to another location – even after a month . Sharks have also demonstrated memory retention of up to 50 weeks .
Goldfish , in absolute opposition to the three second belief , appear in experiments to be able to remember the colour of feeding tubes for up to a year . Catfish can even remember food calls from specific human beings up to five years after they last heard them .
Another way of suggesting intelligence is the use of tools . This would seem to be quite tricky for fish , with no fingers or thumbs to manipulate their environment . However , tuskfish use coral and rocks to break open shellfish to eat , while wrasse use rocks to crack open their sea urchin meals . There have even been experiments where certain species of cod learned to pull a string for food to be dispensed .
“ Mosquito fish can count up to five "
Fish can also do maths . Mosquito fish can count up to five and have also shown an understanding of mathematical ratios . Angelfish can also reliably count to five and use ratios to choose between larger groups , while cichlids and stingrays can perform basic addition and subtraction . Newborn guppies can count up to four , but seem to learn ratios later as they mature .
But there ’ s one type of fish I particularly want to namecheck , and that ’ s the cleaner wrasse . These remarkable little fish have not only shown intelligence , but , along with manta rays , have also passed the ‘ mirror ’ test , the standard test for self-awareness in animals . In a mirror test , an animal is sedated and something is changed on their body . When
Relationships forged by cleaner wrasse indicate intelligence and a sense of trust they wake up , researchers watch to see if they notice what has been changed .
When put through the mirror test , fish with an added coloured tag attached to their body attempted to scrape off this tag by scraping their bodies on the side of the mirror . Cleaner wrasse also have social interactions , both among cleaner fish in a population and between a cleaner fish and its clients . Cleaner fish approach the client fish in pairs , and face a social dilemma : they must balance helping their partner with sneaking around to consume the desired mucus themselves . Social pressure plays a role in ensuring good behaviour — when there is a third fish observing them , cleaner fish tend to behave more cooperatively .
Fish are just amazing , even the small ones . �
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