A trickle of water running over parched earth is all the encouragement the desert goby needs. The unassuming little fish, reckoned by researchers to be a poor to average swimmer, only needs a few centimetres of water to follow a rivulet from one isolated, muddy puddle to the next. In the desert rivers region on the southern edge of Lake Eyre in Australia’s red centre, a few centimetres of water may be all it gets.
But their ability to move quickly and opportunistically when floodwaters hit has caught the attention of researchers.
“What we think they are doing is very quickly taking advantage of very little amounts of rain,” Krystina Mossop, a PhD candidate from Monash University told Guardian Australia.
“Whenever there’s opportunity for flooding to run between those pools that are otherwise isolated, then the fish are using them and they are using them quite well.”
Mossop and her research partners have spent the past few years heading out to Lake Eyre in a four-wheel drive searching for goby-containing puddles to take a sample of their fin for genetic testing. The results of that research were published in the Journal of Biogeography this month.
The study tracked genetic markers and found the fish were travelling vast distances to reach new mates.
It found close family relations stretching across hundreds of kilometres of arid country and between apparently isolated pools.
The use of flood-driven dispersal despite their poor swimming ability, which Mossop notes is “quite average”, sets the desert goby apart from other species of Australian desert fish which often show more isolated population patterns.
In the dry times, these 6cm almost eel-like yellow and blue fish hang out in water holes that can be little more than small muddy puddles, which get hotter as the daytime temperature creeps up past 40 degrees. They are remarkably hardy and can survive in water three times saltier than seawater and much lower in oxygen.
“They can do pretty well with extremely shallow channels of water and can even hop over moist areas of land for short distances, just enough to get to the next puddle and the next one after that,” said Mossop.
The flooding also creates risk. While it helps the gobies move it also attracts birds, which are happy to make a snack out of an enterprising fish attempting to flip its way across damp sand. Still more will die when the water runs out before they reach the next pool.
“It’s a risky venture but enough fish will get through and reach new patches of water and, more importantly, will reach new potential mates and be able to reproduce,” Mossop said.
