THE SPINY LOBSTER OP SOUTHERN FLORIDA. 299 



and other forms offer protection. It is known from a limited local knowledge of the 

 bottom near these reefs and also from the charts that the character of the bottom outside 

 these reefs is less rocky and apparently does not afford good protection for spiny lobsters. 

 The inference, therefore, is that the limit of distribution is bounded by these reefs, 

 or it may extend a short distance beyond to detached coral reefs farther out. 



Fishing operations are thus practically limited to shallow water and to an area 

 not over 7 miles in width, including all places where all sorts of gear could be used. 

 The region actually covered by the regular fishermen is not more than half this width 

 and is confined to shallow banks not far from shore. The remaining strip is now, in 

 reality, a natural reservation where protection is enforced by the limitations of the 

 fishermen. This reservation, however, may be destroyed easily when the demand for 

 spiny lobsters will make it profitable to invest in more elaborate gear, and it may be 

 necessary then to establish definite reservations protected by law. The situation now 

 prevents the concentration of large numbers of fishermen on a limited area, and exter- 

 mination of the spiny lobster is not imminent. The dangers of overfishing, however, 

 are obvious, and the present laws should be enforced. 



The causes for migrations are numerous and rather obscure, but the three which 

 seem to be the most important are molting, mating, and changes in temperature which 

 probably affect both molting and mating. Local movements of relatively small num- 

 bers of spiny lobsters take place, which are probably caused by varying conditions of 

 the water and food supply. A migration, as here considered, is a movement of a large 

 number of spiny lobsters over a wide area, the movement being marked by more or 

 less definite conditions. 



The approach of the maximum molting season is marked by an increasing number 

 of spiny lobsters in shallow water which differ in color from those usually found there, 

 and many of which are about to molt. This condition does not exist merely locally 

 but is found to be general over an extensive area. Catches of spiny lobsters brought 

 into the market at Key West from widely separated places, such as Sugar Loaf Key 

 and Marquesas Keys, show that the spiny lobsters about to molt migrate into shallow 

 water at both places within the same month. Fewer spiny lobsters are taken at the 

 height of the molting season than at other times, probably because the animal is less 

 active at this time, and few spiny lobsters with soft shells are taken by the fishermen. 

 This has led to the belief that, although the old shell is cast in shallow water, the 

 spiny lobster soon retires to greater depths. Spiny lobsters with soft shells have been 

 caught in quite shallow water near Key West, and it may be that there is no extensive 

 movement of newly molted ones into deeper water unless the changes in temperature 

 of the shallow water become unfavorable to the animal in its delicate condition. 



The maximum breeding season varies somewhat in time from year to year and in 

 different places. The number of spiny lobsters is known to increase in certain places 

 during this time and also during the spawning season. Migrations of large numbers 

 of spiny lobsters must then occur, for large catches of spawn-bearing females are made 

 in certain places and not in others, and after the spawning season is over the catches of 

 females decrease in places where they were formerly plentiful. 



The following table (1) is a summary of the catches of spiny lobsters taken by means 

 of a group of three traps set in about the same location from March to August, 19 19, 

 inclusive, the purpose of which is to demonstrate the decrease in the number of large 



