FISHERY BULLETIN: VOL. 87, NO. 3, 1989 



Figure 4. — Corrugated PVC sheet "temporary shelter" used to corral juvenile abalone in 

 the hatchery, act as containment structure in transport, and serve as a stocking module and 

 protective habitat for abalone planted in the marine environment. Over 200 juveniles (1-2 

 cm) may be contained in a single unit 20 x 20 x 30 cm. Abalone planted in these modules 

 move to surrounding natural habitat within 24-48 hours without the high handling and 

 predation mortality experienced with other methods (Leighton 1985). The layered plastic 

 material is manufactured by B. F. Goodrich Company as "Bio-trickling Filter Medium" for 

 use as a high surface to volume bacterial substrate applicable to sewage treatment process- 

 es. [Reference to trade name does not imply endorsement by the National Marine 

 Fisheries Service, NOAA.] 



in the private sector in the period 1970-75; 

 highly effective methods were found to allow 

 rearing of young red and green abalones through 

 larval and early postlarval stages (ca. days 1-15) 

 with minimal losses (Leighton 1987). These pro- 

 cedures have understandably been closely 

 guarded by the pioneering U.S. abalone cultur- 

 ists. Recently, reports have appeared of new and 

 grand technological advances in abalone culture 

 through research in government (e.g., Ebert 

 and Houk 1984) and academic laboratories (e.g., 

 Hooker and Morse 1985). However, with the 

 exception of the highly useful hydrogen peroxide 

 method for induction of spawning in abalones 

 (see Hatchery Methods), these studies have not, 

 to date, added significantly to the technology for 

 culture of larvae, postlarvae, and juveniles de- 

 veloped by the industry. Certainly, however, 

 the research has contributed valuably to our 

 understanding of basic biological processes (see 

 below). 



Interest has focused recently on the facilita- 

 tion of settlement and prompting of metamor- 



phosis by the addition of bioactive chemicals 

 such as the neurotransmitter, gamma-aminobu- 

 tyric acid (GABA) and related compounds 

 (Morse et al. 1979). GABA does indeed cause a 

 change in swimming behavior, possibly by 

 affecting the bioelectric potential of cell mem- 

 branes associated with the velar cilia (Kosh- 

 toyants 1960; Baloun and Morse 1984), with 

 active settlement in mature and "competent" 

 larval abalone. Behavior of larvae exposed to 

 GABA, however, differs from that of larvae in 

 the presence of "natural" inducers (see below). 

 Exposure of larvae to GABA at concentrations 

 in excess of 10"^ M is in fact lethal (Akashige 

 et al. 1981; Slattery 1987), perhaps a conse- 

 quence of excessive activation and/or blocking of 

 receptor and transduction sites involving other 

 vital functions. The role of GABA as a neuro- 

 transmitter is now well recognized in vertebrate 

 and invertebrate systems. However, induction 

 of settling and onset of metamorphosis in aba- 

 lone larvae may be more complex than initially 

 proposed (see Trapido-Rosenthal and Morse 



698 



