BALISTIDAE 



{Trigger fish) 



The trigger fish is another common fish in the coral waters of 

 the Red Sea. Among the species we encountered, the Balistes 

 aculeatus and the Balistes undulatus were the most frequent. 

 They are all more or less alike in shape. The first dorsal fin 

 consists of one or two spines which, in moments of danger, 

 are erected immediately behind the head and become locked 

 with the shorter dorsal fin. The first fin cannot be lowered by 

 any outside force until the second fin unlocks itself by 

 lowering. The second dorsal fin and the anal fin, which is 

 rather large and lies well back, are the principal means of 

 propulsion. They work with an alternating movement. The 

 speed of the trigger fish is, in consequence, rather limited 

 while at the same time its actions are indescribably comic. 



They live exclusively around the barriers. When intimi- 

 dated they take to the cavities and erect their dorsal fins 

 and ventral fins in such a way that it is impossible to draw 

 them out of their hiding-place by hand. This defence habit of 

 theirs has led to their being called 'lock-fish', to which one 

 might add 'with a secret combination'. 



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