118 American Fisheries Society. 



not obtainable, except that shrimp under 1 1/4 inches, which are plank- 

 ton larvae, are not included in the table. All shrimp approximately 

 six inches or over can be considered as adults, while all between the 

 sizes of one and a quarter and six inches while possessing the ultimate 

 fonn of adults, are immature sexually. 



Curve (a) (a) indicates the rate of growth of the minimum sized 

 individuals of the so-called spring crop, which is in reality the small 

 shrimp left over from the preceding fall, (a) (a) which grew very 

 little during the winter. Curve (b) (b) indicates the development of 

 the maximum sized individuals of the summer crop. 



After reaching maturity, this rapid rate of growth evidently 

 ceases, so that we find individuals varying somewhat in size, at all 

 seasons of the year. During the summer there is an increase in the 

 average size of the adults and the maximum sized specimens obtained 

 in the littoral zone of the gulf duri'ng the various months are rep- 

 resented by the curve (c) (c). The sizes of shrimp to the left of the 

 dotted curve (d) (d) represent average sizes of shrimp taken from 

 inside waters while sizes to the right of this curve are from average 

 measurements of shrimp from outside waters in the littoral zone of the 

 gulf, usually from near the beach to five miles or more off shore. Such 

 a strict line cannot in reality be drawn as shrimp varying about an 

 inch either way of the sizes represented by the curve can be found both 

 in inside and outside waters though usually near the coast and in the 

 passes. Besides, there are many minor variations to be considered, 

 caused by irregular natural causes. Although this curve (d) (d) is 

 arbitrary and variable, it represents the approximate age at which 

 immature shrimp migrate back towards the sea during the various sea- 

 sons, they being much smaller during the winter months when the cold 

 weather migration becomes somewhat confused with the permanent 

 seaward migration. 



period. The length of the period in which no shrimp are 

 found widens as we leave the coast line and in such lakes as 

 Ponchartrain and Salvador it is greater than the period 

 during which shrimp are found. In some lakes farther in- 

 land they may even appear only every few years and then 

 only for very short periods during the late summer. As 

 growing shrimp migrate with the tide, they can be consid- 

 ered an excellent index to the presence of sea water how- 

 ever small the amount." 



"Much has been learned of the sizes and quantities of 

 shrimp present in various localities under varying conditions 

 and the sum of this knowledge has been tabulated and in 

 condensed form is herewith graphically presented. 



"As shrimp under three inches are never taken in con- 

 siderable quantities by the fishermen because they are of 

 no commercial value, and as they are not usually associated 

 with the larger sizes, they hardly need be considered in the 

 formulation of a close season on shrimp. Protective meas- 

 ures should be devised more for the purpose of protecting 

 sizes between three and five inches and a study of the table 

 will clearly indicate during which months of the year a 

 close season should be recommended. 



