possible~ap&rt from econoiiiic obstacles— to keep the stock at least 

 stationary or to lead it up to the attainment of a biological opti- 

 mum. I could estimate that in the Dutch lobster districts about 

 80 per cent of the males and 60 to 70 per cent of the females of 

 23 om» and more v/ere caught yearly. These figures do not hov/ever 

 prevent the lobster population from increasinpj annually still 

 around about 6 per cento Principally there are two methods for 

 the maintenance of the stock: First, one can require so far as 

 possible, thi'ough legal size regulations, the natural course of 

 fecundation, birth and growth^ and second, one can iiaprove the 

 nat\xral progress through artificial rearinge The last method is, 

 at the present time, not yet practically worked out satisfactorily, 

 to give a" positive result. The first however suffices to regulate 

 the fishery at a desired elevation. This happy condition is a 

 sequence of the fact that first, the lobster is a' very stationary 

 animal; second, aside from humans, neither foes nor parasites in 

 'considerable numbers endanger it; third., sexual }naturity occvirs at 

 a size that renders possible,, on economic grounds, the- protection 

 until the attaimnent of this size; fovirthj, the' fishery does not 

 coincide with the spawning time. In regard to this matter, the - 

 following protective measures should exist as far as possible: 

 first, a minimum size that protects the lobsters as long as they 

 have at least once contributed to propagation; this size will in 

 the various districts alternate between aboiit 23 and 26 cms o or 

 what is better and more easily determined, 11-12 cm. from t^e 

 frontal process to the posterior margin of the' carapace} 2/ 



\J ■ k maximum regulation and a naximum entrance opening of the 

 fishing cpparatUE also has become proposed, in order to 

 spare ;the large individuals and, especially the large 

 females v/hich, with increasing age, alvmys produce j:iore 

 eggs. Economic difficulties will however mostly''prevent 

 the installation of this regulation. 



second, sparing of the egg-bearing females; the, police control on 

 this is not so, difficult as is often claimed since it is quite 

 laborious to remove the eggs dov^'li to the last' one, because accord- 

 ingly the presence also of r single egg can be placed under 

 ■penalty this measure becomes supplied or' substituted through a 

 closed time for the females; third, r. closed time in summer, since 

 the eggs are then ripe and easily great numbers are lost by the 

 catching and releasing of the females; also' the 'stock in this tiiTie 

 can becoiae reduced because of :iore females than' otherYJ'ise--whon 

 the egg bearers are protected because, for many, the eggs already 

 have slipped tiff and the new oviposition has not yet followed. 

 There is thus a time in which few feinales carry eggs and so lack 

 protection. During this summer closed time also most of the 

 lobsters shed and would form because of it r.n inferior product 

 for the inarket. The length of this closed time or of closed 



149 



