this size are being steadily removed, 

 insufficient larvae are being produced 

 to bring about an increase in the 

 sponge population. As a result the 

 concentration of sponges will remain 

 at an almost constant level. 



Potential Larval Production Related 

 to Volume 



The average size of the mature sponges in 

 an area is also an important factor in bring- 

 ing about an increase in sponge population as 

 well as the concentration of sponges of mature 

 size. On a volumetric basis the ratio of the 

 volume of a 6-inch diameter sponge to sponges 

 of 7 to 11 inches in diameter is revealing. 



It is the total volume of reproducing sponge 

 material present in an area and not the number 

 of sponges alone which must be considered. It 

 may be seen from table 3, for example, that 

 an 11-inch sponge may produce more larvae 

 than six 6-inch sponges. 



Optimum Temperatures for Larval 

 Production 



Larval production cycle throughout the year 

 and the relationship of temperature to this 

 cycle were determined by monthly collections 

 of wool sponges made during most of the 2- 

 year study period. Diving boat crews collected 

 and preserved the sponges for later examina- 

 tion at the Marine Laboratory of the University 

 of Miami. During each of the field trips, large 

 numbers of sponges were also examined for 



larval production and size of the sponges at 

 maturation. Well over 700 sponges were ex- 

 amined during the study. 



Probably the longest and most complete 

 records of sponge larval production were ob- 

 tained by F. G. Walton Smith (personal com- 

 munication). These records are for the breed- 

 ing cycles off Tumeffe, British Honduras. 

 Information regarding the larval production 

 cycle in the Bahamas was also available. The 

 combination of three cycles plus parallel 

 records of monthly mean water temperatures 

 from the corresponding areas are presented 

 in figure 4. 



The temperature data were obtained from 

 U.S. Department of Commerce Special Publi- 

 cation No. 278 (1955), which gives the surface 

 water temperatures at tide stations along the 

 Atlantic and Gulf of Mexico coasts. Accuracy 

 to within 3°F. is claimed, depending on the 

 location of the tide station on the shore. 



Data on larval production are given as the 

 percentage of sponges producing larvae of the 

 total number examined each month. Cedar 

 Keys data are for the area from Tampa Bay 

 to St. Marks. Data from the Bahamas and 

 British Honduras were obtained from F.G. 

 Walton Smith. 



The two critical temperatures in the larval 

 production cycles appear to be 73° F. and 84° F. 

 In the Cedar Keys area, larval production 

 begins as soon as the mean monthly tempera- 

 ture rises to about 73° F. and increases 



Table 3. — Potential larval production related to volume 



■"■ With the observed number of larvae in a 6 inch sponge being taken as unity. 



^ Based on length of larval production season and length of time for maturation of 



one larva (4 weeks) 



12 



