Denise Costello of Mosgiel asks :-
Why are tropical fish brightly coloured but New Zealand fish are dull?
Stephen Scott, a marine zoologist at Otago University, responded.
Fishes use their colours and patterns to help them hide or to send signals to the animals around them. The bright colours of fishes, and the associated behaviours, can be used for species recognition ("Hi: I'm one of you"), to signal predators to beware ("Warning: I'm dangerous" or "I taste disgusting"), to defend territory ("Oy you: get out of my space"), and to indicate reproductive state ("Hi there: would you like a date").
The colours of fishes may also reflect the environment they inhabit. The tropical reef environment has clear waters and high sunlight levels all year which make it a bright place, especially with the colourful corals present. On the other hand, New Zealand's coastal marine environment tends to have murky waters, variable sunlight levels, and seaweeds that are less colourful.
For a fish to hide on its tropical reef, bright colours and unusual patterns are very effective. There is also an enormous number of fish species in the tropics, so a lot more signalling goes on among the fishes there. Tropical fishes may reproduce all year round, so tend to have breeding colours for longer than the fishes in New Zealand.
Overall, fishes of the tropical reefs tend to be more brightly coloured than fishes in New Zealand because of their environment, their diversity and their style of reproduction. However, there are many beautifully coloured New Zealand fish such as the goatfish, wrasses and small triplefins in their breeding colours, so look out for them.