COASTAL FISH 

 BjJ.R. Pfaff 



Mud-skippers (Periophthalmus) are extremely common on m.uddy shores. 

 The Galathea had collected a number in West Africa, but I myself saw 

 them for the first time at the small port of Beira in Mozambique. 

 The tide was out when I crossed the bridge which leads from the harbour 

 to the town, and beneath me lay extensive mud-flats fringed with man- 

 grove. I was watching the ubiquitous tropical crabs, along with the peli- 

 cans that had settled down in the background, when suddenly my atten- 

 tion was caught by some lizard-like creatures which were hopping about 

 with great agility. Although they were on dry land, there could be no 

 doubt that they were fish — mud-skippers, in fact. Small circular holes 

 in the mud revealed their hiding-places. However, the spot was too in- 

 accessible to permit closer observation and so I walked on towards the 

 sweltering town. On returning an hour or two later I found the mud- 

 flats covered by the incoming tide. This is the typical habitat of mud- 

 skippers. I had better opportunities of studying these strange creatures 

 later on, especially in Galathea Bay on Great Nicobar. 



Walking along the shore of this bay I came to a small stream which 

 teemed with them. They normally inhabit salt water, and the water in 

 the lower reaches of this stream was sufficiently saline. They sat on 

 stones, fallen branches, and mangrove roots, watching me with large, 

 alert eyes closely set on top of the head like two peas. In order to moisten 

 them they were occasionally drawn right into the head, where they would 

 roll round in a most comical manner. Often the tip of the tail would be 

 in the water; some naturalists think that mud-skippers may breathe with 

 their tails, and at least they will get a certain amount of moisture by this 

 means. They would usually sit with the forepart of the body slightly raised, 

 holding on by the pectoral fins, which resemble small arms. This being a 

 collecting expedition, however, we had to set about catching a few of 

 them. It was easier said than done. No sooner was the net thrust out 

 than they skipped nimbly away, and sat watching me with apparent 

 amusement from a stone a couple of metres away. Strangely enough, 

 they do not seek refuge in the water, but are able to "skate" over the 

 surface with short, vigorous strokes of the tail fin. They are actually 

 more terrestrial than aquatic animals. The only result of my persistent 

 efforts was a few of the smallest individuals. 



