A new behavioural study of Unicorn tangs has shown how the fish is linked to its habitat and could be used to help set the boundaries of marine reserves.
Carl Meyer and Kim Holland of the Hawaii Institute of Marine Biology studied the Unicorn tang, Naso unicornis, in a small Hawaiian marine reserve and have just reported their findings in the latest issue of the journal Environmental Biology of Fishes.
They found that Unicorn tangs fell into two distinct behavioural groups, which they dubbed "commuters" and "forayers".
The commuting fish spent the night in refuge holes on the reef, travelled to feeding sites several hundred metres away in the morning and then returned to the hidey hole as night fell.
In contrast, the foraying fish didn't undertake any crepuscular movements and lived and fed around their refuge holes in the reefs, and also returned to them during the day.
A couple of the Unicorn tangs observed were also active during the night, something we've not heard much about in acanthurids before.
The tangs also seemed to remain within the reserve and Meyer and Holland say that this knowledge of the fish could help set the boundaries of marine reserves:
"There was little direct evidence of dispersal from the reserve, but differences in Bluespine unicornfish abundance and size among reef habitat zones were consistent with ontogenetic habitat shifts.
"The gross habitat characteristics could be used to predict reef fish movements. This could provide a simple method for setting marine reserve boundaries at sites for which empirical fish movements are unavailable.
For more details see: Meyer, CG and KN Holland (2005) - Movement patterns, home range size and habitat utilization of the bluespine unicornfish, Naso unicornis (Acanthuridae) in a Hawaiian marine reserve. Environmental Biology of Fishes, Vol. 73. No. 2, 201-210.