Because of the age and physical condition of 

 the divers at the present time, most of the 

 sponging work is done in water less than 40 

 feet deep. If this situation continues the only 

 useful extension of the sponging area will be 

 that from Rock Island to Carrabelle in the 

 northern part of the sponging grounds. Since 

 the concentration of sponges in commercial 

 quantities in the deeper water to 120 feet can- 

 not be expected for another 15 to 20 years, 

 this does not entail serious consideration by 

 the industry at the present time. Concentra- 

 tion of sponges in quantity in 60 to 70 feet can 

 be expected in the next 5 or 10 years. 



Within 5 years (after 1957), the total sponge 

 producing area should increase by 50 percent, 

 of which only 7 percent will lie within the 40- 

 foot depth, the present range of most of the 

 diving boats. Assuming sponge concentration 

 equal to that in the present grounds, the added 

 area will increase production by only 7 per- 

 cent. A further extension of 40 percent of the 

 then existing area in the next 5-year period 

 will add very little if any available sponging 

 ground, provided divers are still limited to 

 less than 40 feet of water. As the sponges ex- 

 tend into deeper and deeper water, dispersion 

 may progress more quickly as currents of up 

 to 11.5 miles per day are recorded for the 

 area. 



A much more important factor to the spong- 

 ing industry than extension of the beds would 

 be a sizeable increase in the concentration of 

 sponges on the bottom. After careful examina- 

 tion of all the biological data gathered, I 

 believe that an increase from 40 percent to 

 60 percent in biological production within a 4- 

 to 5-year period may be expected through in- 

 creased sponge concentration, if more diving 

 boats are not put into operation and no disease 

 or adverse ecological condition occurs. 



In the region of the circular eddy just south- 

 east of Cedar Keys, an accurate picture of 

 sponge concentration has been difficult to ob- 

 tain. Exploration of this area on the field trips 

 did not disclose any large concentration of 

 sponges, but, according to reports by some 

 spongers, there are parts of this area where 

 sponges are to be found in some quantity. One 

 take of 3,000 sponges in 40 to 55 feet from 



this area had 32 percent larger than 10 inches 

 in diameter. 



Within the limits of the present sponge pro- 

 ducing area (fig. 11) large sections are not now 

 producing sponges in quantities great 

 enough for economical harvesting. Certainly 

 much of the expected increase in the immediate 

 future must come from increased concentration 

 and filling in of those spots where the sponges 

 are thinly distributed. 



The above predictions are based on the 

 assumption that there are uniform currents 

 and uniform survival rates of the sponge larvae 

 from year to year. Temperature patterns, 

 which control egg production, will vary from 

 year to year, as will wind pressure and the 

 resulting changes both in the rate and direction 

 of the currents. It is quite conceivable that 

 conditions one year would result in very un- 

 expected distribution of the sponge larvae in 

 large quantities, while during another year 

 the production of larvae would be small or large 

 numbers would be killed by adverse weather 

 conditions. In the area north of Cedar Keys, 

 the large numbers of sponges less than 2 inches 

 in diameter and the heavy production of larvae 

 by the mature sponges indicate that in 1955 

 large numbers of sponge larvae settled on the 

 bottom. Also, larval production in 1956 and 

 1957 was high and should have resulted in the 

 starting of large numbers of sponges. Few 

 small sponges were observed during the field 

 trips on the bars immediately north of St. 

 Martin's Reef Light and in water of less than 

 40 feet. Few mature sponges in this same 

 area were seen to be producing larvae. 



DISCUSSION AND RECOMMENDA- 

 TIONS 



History of Decline in Sales from 

 1938 



During the past 15 to 20 years, synthetic 

 sponges have appeared on the market as a seri- 

 ous competitor for natural sponges. Present 

 retail sales of synthetic sponges are 10 to 15 

 times that of the trade in natural sponges, and 

 more than $20 million of synthetic sponges are 



65 



