10 



IV. particulars are given relating to male and female prawns found 

 in a soft condition or recovering from casting. It will be noted 

 that as many as 21*6 per cent, of the males examined in March were 

 recovering from casting. For February and April the percentages 

 were 4*5 and 10 5 respectively, differing little from those for the 

 same months of last y ear when the percentages were 3' 6 and 9*8. 



March is then the chief month for the casting of male prawns, 

 though many cast in April. 



Females recovering from casting were few in numbers, the 

 percentages being February 04, March 09, April 19. Last year 

 they were found to be 06 and 2 for February and April respectively. 



It was stated in last year's report that the female prawns cast 

 after the hatching season, and also that attempts were being made 

 to hatch out larvae in the tanks of the Laboratory. On the 3rd of 

 November, 1911, twenty-nine berried females, three of which after- 

 wards died, were placed in a large tank ; they were examined 

 periodically, and the changes in the eggs and the fact that the eggs 

 were few in number in April, 1912, have been previously recorded. 

 During May and June the water of the tank was frequently netted 

 but no larvae were obtained. On the 23rd of July the tank was 

 emptied, and it was then found that the prawns had, with the excep- 

 tion of one individual, all cast their shells. 



Of the 565 prawns which were marked and liberated in April, 

 1912, only two have been recaptured. On the 7th of May, 1912, 

 the skipper of the " Reaper " reported catching one to the east of 

 Blyth, but the cook accidentally threw it overboard. The other 

 was a male of 16 cm., and was caught 10 miles E.S.E. of the Tyne 

 in 40 fathoms on the 20th of June, 1912. The creature had cast its 

 shell, and although the wound made by the punch had healed, with 

 the exception of a small portion, yet the area punched out could 

 be distinctly traced. This prawn was liberated 12 to 14 miles east 

 of Newbiggin. The amount of migration was small, and had been 

 towards the southern portion of the prawn ground. 



It is evident that the method of marking by punching out a 

 piece of the telson is not satisfactory, the mark failing to attract 

 the attention of the fishermen and the buyers. If further experi- 

 ments of the same nature are to be undertaken on a future occasion, 

 some sort of label will have to be employed similar to that used for 

 marking crabs and lobsters. 



