Maybe its not catch and release but that they're getting smarter.......

Nine-spined stickleback share the human ability to copy each other's behaviour if it's to their advantage.

They're small in size but big in mind: sticklebacks display a remarkably human-like intelligence when it comes to searching for food, according to scientists in the UK. By comparing their own experiences with the behaviour of their fellow fish, the sticklebacks are able to improve their success rate.

The discovery of this sophisticated type of social learning in sticklebacks, known as a "hill-climbing" strategy, suggests that such cognitive tricks might be more common among non-human animals than previously thought.

The study also shows that big brains like humans' might not be the only way to produce a cumulative culture within a species.

"Small fish may have small brains but they still have some surprising cognitive abilities," said Jeremy Kendal from Durham University's anthropology department. "Hill-climbing strategies are widely seen in human society whereby advances in technology are down to people choosing the best technique through social learning and improving on it, resulting in cumulative culture. But our results suggest brain size isn't everything when it comes to the capacity for social learning."

Kevin Laland of St Andrews University, who also took part in the study, said: "Nine-spined sticklebacks may be the geniuses of the fish world. It's remarkable that a form of learning found to be optimal in humans is exactly what these fish do."

In the experiment, reported in tomorrow's issue of the journal Behavioral Ecology, scientists caught 270 nine-spined sticklebacks from the Melton Brook in Leicestershire. The fish were placed in a tank with two feeders, one of which supplied a lot more food than the other, known as the "rich feeder".

The fish that learned to prefer the rich feeder were then allowed to watch their fellow fish feeding in a separate test but, this time, the two feeders had been swapped. After watching for a while, the observers were allowed to choose a feeder for themselves and around 75% were able to work out from their observations that the feeders had been switched.

Lots of animals learn from their more experienced peers to gain skills such as hunting, foraging or evading predators.

"But it is not always a recipe for success to simply copy someone," said Kendal. "Animals are often better off being selective about when and who they copy. These fish are obviously not at all closely related to humans, yet they have this human ability to only copy when the pay-off is better than their own. You might expect this ability in animals who are closely related to humans. In the case of the nine-spined stickleback, they have most likely adapted to their local ecology."