THE SALMON 47 



to the sea, have been known to produce ripe ova 

 when little more than overgrown smolts. 



The Salmon has numerous enemies. Eels are 

 especially destructive to the eggs, and Pike, Perch, 

 Trout, and piscivorous birds prey upon the young 

 fish during their two years of life in fresh water. 

 Shoals of Coal-fish and other members of the 

 Cod family are said to keep a look out off the 

 mouths of the rivers for the descending smolts, 

 whilst flocks of Gulls, Cormorants, etc., prey upon 

 them in the estuaries. Seals account for large 

 numbers of Salmon and often accompany them 

 in their migration for considerable distances 

 inland. 



Fresh-run Salmon are usually characterized by 

 the presence of Sea-lice, little parasitic Crustaceans 

 of the order Copepoda, which differ from the free- 

 swimming shrimp-like members of the order in 

 the reduction in number of segments and limbs, and 

 in various modifications of structure which enable 

 them to adhere to their host and to suck its blood. 

 These Sea-lice (Lepeophtheirus salmonis) are usually 

 females, which measure about f of an inch in length, 

 the males being scarce and only about one-third as 

 long. The lice are very firmly attached to the Salmon, 

 their carapace acting as a sucking-disc and claws 

 being dug in to increase the strength of their hold. 

 They feed on the blood of their host, their lips 

 forming a tubular proboscis enclosing the mandibles, 

 which are modified into a pair of piercing spikes. 

 The eggs are biscuit-shaped, and as they emerge 

 from the openings of the oviducts they are cemented 

 together by a secretion, forming a pair of egg- 

 strings which resemble the jointed antennae of a 



