502 BULLETIN OF THE BUREAU OF FISHERIES. 
The introduction of diving came at a time when the older method of spong- 
ing had finally demonstrated its inadequacy to supply the demand for sponges, 
and by developing new beds it has deferred the time when the Florida sponge 
beds will no longer be able to sustain the demands of the markets. On the other 
hand, it will undoubtedly operate to retard the recuperation of beds already or 
about to become exhausted, and will, of itself, tend to depopulate the beds on 
which it is carried on and, indirectly, the hooking grounds adjacent to such beds. 
From the comparative facility with which it can be conducted, irrespective of 
the condition of the water, the thoroughness with which the bottom can be 
scoured and the reckless disregard of the future with which the divers gather 
small sponges, diving is undoubtedly more dangerous in the denudation of the 
beds than is hooking. The recent legal restriction of the fishery to the deeper 
waters and to the more boisterous season of the year, when many days are lost 
on account of stormy weather, will operate to curtail the catch and the profits 
and restrict the number of persons engaging in it, and to this extent the con- 
servation of the beds will be accomplished. What may be the ultimate result 
of the introduction of the diving machine will depend largely upon the area and 
productiveness of the beds outside of the 8-fathom curve. If they be four or 
five times as great as those of the beds within that limit, the Bay grounds can 
support a profitable fishery for some years to come, but if they are no greater 
than there is now reason to suppose, the effects of the fishery will become appar- 
ent within the next five years. 
DREDGING OR TRAWLING. 
The dredge or gangava is not used in Florida or the West Indies, but the 
testimony of European authorities and an appreciation of the effects of the 
dredge and beam trawl used by naturalists indicate that without regulation its 
effects must be disastrous. If used in profound depths to take sponges wholly 
beyond the reach of other methods of the fishery it has some justification, but 
even then it would probably retard the recuperation of the adjoining beds in 
more shallow water in the same manner as denudation by the scaphander would 
curtail the supply of young sponges on still shallower beds. 
There can be no doubt that the gangava is a destructive engine. With it 
there can be not even such imperfect selection as is exercised by the hooker and 
the diver, and the proportion of young sponges brought up is correspondingly 
greater. On the banks of Lampedusa, where the gangava and the scaphander 
work practically side by side, it is stated on the authority of Lucifero that the 
refuse sponges brought up by the former constitute 25 per cent of the total catch, 
while but 6 per cent of the diver’s catch is composed of refuse, small, and 
seconds. ' It is stated, also, by the same authority, that owing to the damage 
done to small sponges it requires five years for banks to recover from the effects 
of dredging, and even then the crop is limited, while two years suffices for the 
