It may be useful to set the size higher if, by allowing the fish 

 to live longer^ a greater return can be had from the same number of 

 fisho If a group of fishes is left longer without fishing they will 

 increase individually in weight© A few will die^ howeverj and the 

 weight of these fishes will have to be subtracted from the increaseo 

 Moreoverj as the fish live longer they will take a larger amount of 

 food from the limited amount of available food stock for metabolism 

 and their rate of growth will decline o 



Enlarging the minimum size above the minimum necessary for egg 

 production is only necessary if the increase in weighty regardless 

 of the dec?line of the growth rate, exceeds the loss by natural 

 mortality and destruction of undersized fish by the fisheryo 



Finallyp it needs to be taken into account if the weight 

 increase also represents an increase in financial returns o This 

 will be true for the majority of fish species as the price per 

 kilogram increases progressively with the length of the fisho In 

 this case protection will already be profitable when the total 

 weight of the fish catch is not necessarily greater but when only 

 the average length increases o Sometimes, howeverj, it happens that 

 the larger fish are somewhat less valuable per kilogram than the 

 smaller oneso 



Since the reasons for the determination of the lower limit of 

 the minimym size and those for the determination of the upper limit 

 are differentj, there is theoretically a possibility that the lower 

 limit advocated for retaining an adequate egg production will be 

 above the upper limit desired for economic reasons o However^ this 

 possibility is not very greato 



Now we can determine the best size for each species andj in 

 agreement therewith, the best mesh widtho Since we may expect 

 •various species in the same region, it will be necessary to make 

 one mesh width for all these specieso This will have to be a 

 ^5*Mnpromise between those which will be best for each species© In 

 many cases it will be desirable to connect the definite itinimum 

 siaeej,='-iitilising the selection curves==with the mesh widths that is, 

 to set them so that as few fish as possible will have to be thrown 

 backj without tempting the fisherman to evade the regulations for 

 mesh widths o We believe, thereforeg that the minimum size must be set 

 at the length group whereby 75 percent of the fish caught remains in the net© 



Deviations from the size, found by the above rules, may be 

 considered if that size is designed to make fishing unprofitable in 

 certain areas which one does not want to be fishedo AlsOj, deviations 

 from the size may be considered if that size is designed to prevent 

 a fishery from becoming unprofitable in certain areas o 



