240 BRITISH FRESHWATER FISHES 



The Sticklebacks {Gastrosteidce) are the smallest 

 of the British freshwater fishes, but they are by no 

 means the least interesting. They are well worthy 

 of attention on account of their pugnacity and their 

 remarkable breeding habits, but still more for their 

 great variability, which has been the cause of very 

 divergent opinions as to the number of species which 

 should be recognized. 



The Sticklebacks form a well-marked group of 

 fishes, the Gastrosteoids, which resemble the 

 Scorpaenoids in that the second suborbital bone* is 

 produced across the cheek to the praeopercle, but 

 differ from them precisely as the Grey Mullets differ 

 from the Perches, in the loss of the attachment of 

 the pelvic bones to the clavicles. The development 

 on the chest of a pair of bony plates {ectocoracoids)^ 

 which in the adult fish are completely united with 

 the shoulder girdle, is highly characteristic. 



The Stickleback family {Gastrosteidce) comprises 

 five genera, each with one, or at most a few, species. 

 Two of these are North American, and a third, the 

 Fifteen-spined Stickleback {SpinacJiia spmachid), 

 although British, is exclusively marine. Our species 

 are the Three-spined Stickleback {Gastrosteus 

 aculeatus) and the Ten-spined Stickleback {Pygosteus 

 pungitius). 



The Three-spined Stickleback {Gastrosteus 

 aculeatus) is also known as Prickleback or Tittlebat, 

 and has a host of other local names, such as Jack- 

 sharp, Pricky, Stickling, etc. ; it is a little fish, 

 never attaining a greater length than 4 inches, 

 which is found on the coasts and in the rivers of 

 the arctic and temperate regions of the Northern 



