72 MARINE PRODUCTS OF COMMERCE 



1945. Much greater quantities of G. confervoides were present in 1943 and 1944 

 than during the next 5 years. 



Methods of Collection. In Cahfornia virtually all commercially collected 

 Gelidium is obtained by divers wearing a complete suit and working in a depth of 

 10 to 30 feet. Gelidium cartilagineum is always quite firmly attached to rocks from 

 the lowest tide line to a depth of 50 feet or more. It is most luxuriant where the 

 water is turbulent. The diver pulls the seaweed from the rocks by hand and 

 places it in a rope-net basket that holds 60 to 70 pounds when full. Most diving 

 is done between May and November and only on relatively calm days. During 

 an average year there are 100 to 120 days when suitable weather conditions pre- 

 vail. In a day a diver may make two or three descents of 1 to 2 hours each, with 

 rest periods in between. A veteran diver may gather one and a half tons of 

 Gelidium a day under ideal working conditions. The usual day's harvest for one 

 diver is about 1500 pounds (Tseng, 1947). Although Gelidium cartilagineum, 

 occurs from San Francisco southward to Puerto San Bartholome, its commercial 

 abundance is restricted to the area from Point Conception, California to Magda- 

 lena Bay, Baja California (Mexico). The plant grows to a height of 4 feet, but is 

 considered harvestable when it reaches 12 to 18 inches (Tseng, 1944). Most of 

 the Gelidium, processed in California during and following the war came from 

 Baja California (Mexico), where production of agar raw material is about 10 

 times as great as in California (Anon., 1947). About 225 tons of dry Gelidium. 

 were imported from Mexico in 1948 for processing in California. 



In North Carolina and Florida seaweed collecting is much simpler. All com- 

 mercial species occur in great loose masses on shallow flats where the bottom is 

 muddy or sandy and where the depth is from 1 to 3 feet at low tide. Collection 

 is a matter of raking the seaweed into a skiff while the collector stands less than 

 waist deep in water, the temperature of which is above 75° F (23.9° C), or even 

 above 80 (26.7° C). In North Carolina some seaweed is obtained by placing 

 nets across channels or narrows through which tidal currents How. Just before 

 the current changes direction, the net is lifted and the seaweed removed. In the 

 fall, when the north winds begin along the North Carolina coast, large quantities 

 of seaweed often wash ashore, especially on the bay beaches facing south. The 

 winds cause a movement of water across the surface of the bay and a counter- 

 current is set up along the bottom. Since all economically valuable species, when 

 loose, tend to rest on the bottom, the countercurrent moves them in a direction 

 opposite that of the wind, with sufficient force to drive them up the slope of a 

 beach, especially with a rising tide. 



Life Histories. From an economic viewpoint Gelidium cartilagineum has a 

 simple life history. It is essentially the same as that described for Irish moss 

 (page 54). Spores produced by the three types of plants germinate and pro- 

 duce new plants if they happen to lodge on a favorably located rock. Mature 

 plants are torn loose during storms and sometimes constitute a source of raw 

 material; however, growth will not occur, as with Gracilaria, after dislodgment. 



Gracilaria confervoides has a relatively complex life history in North Carolina, 

 where it exists in two phases, one of which does not give rise annually to the 

 other (Humm, 1950). One phase is typical of red algae in general and is the same 

 as that described for Irish moss and Gelidium: Plants attached to stones or shells 

 produce spores which in turn produce new plants if they lodge upon a favorable 



