SKATES AND RAYS 129 



Fluctuations in the Catch 



Landings by first-class vessels on the east coast of England 

 have fluctuated as follows : 



6,129 5,382 4,191 3,729 4,247 4,320 



Minchm ' is of opinion that ' the trawls are gradually extir- 

 pating the rays, a slow growing and not very prolific tribe '. 

 He has therefore probably information which the writer has 

 been unable to find as to the wanderings, the spawning, and 

 the rate of growth of this interesting family. 



Life-History 



But the writer's information about the hfe-history of the 

 Raiidae is meagre in the extreme. We do not know apparently 

 the factors which make for or against the safe hatching of the 

 eggs in the egg cases, or against or for infant mortality among 

 the young fishes after hatching. 



According to Hjort,'^ about 68 per cent, of the catch comes 

 from waters between 10 and 30 fathoms, and 19 per cent, 

 from 30 to 50 fathoms. But this does not mean that skates 

 and rays do not inhabit great depths. The Arctic ray has 

 never been caught in water shallower than 350 fathoms, and 

 Holt obtained a species named hathypJiila at 893 fathoms off 

 Ireland. 



Minchin^ notes that they usually remain at the bottom, 

 ' except during the mating season in early summer, when 

 they rise to the surface to do their courting '. And at this 

 time all species seem to move into shallower from deeper 

 water. In the trade, he tells us, the large kind are generally 

 called ' skate ', and lesser ones ' rays ', but this rule is by no 

 means universal. Among the inshore varieties he mentions 

 the ' thornback ' {B. clavata), known sometimes to fishermen 

 and dealers as ' maids ', but more generally under the Dutch 

 name ' roker '. These run to 10 lb. in weight, and are ' very 

 common in the eastern part of the Channel, and in all the 

 deeper waters off the Kentish coast and the Thames estuary '. 

 This species is most common in the North Sea and the Kattegat, 

 Hjort has caught them at 60 fathoms on the Faeroe Bank ; 

 at 100 fathoms at the ' corner ' of the coastal bank south of 



^ Sea Fishing, p. 84. ^ Depths of Ocean, p. 457. * Sea Fishing, p. 83. 

 2497 J 



