This section describes the preparation of seeds for release, site selection, transplantation, and monitoring and management strategies for introduced marine snails.
The 2-year-old green snails of about 5-cm diameter were collected from the rearing tanks in preparation for seed release in the wild. This size snail is recommended as it has better protection from predators. The shells were cleaned dry with a piece of cloth. A tag number was stuck to the outer shell near the base with super glue to prevent the tag number from being removed while in the field. After tagging, shell height and shell width were recorded; such information will be used later in the monitoring (Plate 32).
Before the transplantation is carried out, it is vital to do field surveys to check the quality of the area for transplantation. The area must have the following criteria (Kikutani, personal communication).
4.2.1 Algal cover
Algae, particularly the brown and red turf algae, are essential as food for the seeds. Rich algae cover is the first consideration of an area as a transplantation site.
4.2.2 Current, tides and wind direction
These physical parameters of the sea are very important later for the seeds. Current and wind direction will be responsible for the spread of the incoming generations the seeds. Incoming tides also transport the young ones to other areas, thus enhancing distribution.
4.2.3 Bottom topography
A good reef is necessary also for successful transplantation. It should be complex, with many crevices where the young can hide for protection from predators, and have a well-developed fore-reef slope for adults (Plate 33).
After the survey of the transplantation sites, the tagged shells will be placed into a container and transported to the site by boat. A group of divers will take the seeds to the reef bottom and place them individually in crevices and other structures where they can be protected from predators, strong waves and reef gleaners.
Transplantation of seeds is not enough if there is no data on their survival, dispersion rate and growth rate. It is recommended that monitoring should be standardized and the process to recover the shells requires that operators have good free diving and SCUBA skills to be able to collect sufficient data. The following table could be a useful guide in the monitoring and recovery process.
|0 month||Release seeds||No. of seeds released|
|1 month||Check survival and algae distribution||% Survival|
|12-month survey||1) Check survival, dispersion rate, and growth rate||% S, % DR and % GR|
|2) New tag and release|
|24-month survey||Check survival, dispersion rate, and growth rate||% S, % DRand% GR|
|36-month survey||Check survival, dispersion rate, and growth rate||% S, % DR and % GR|
Engaging local people in the process is vital to the success of introduced marine snail management. People should feel that these introduced shells are for their and their children's use. To this end, the public should be made fully aware of this farming process, and these activities should be community based.
4.5.1 Public Awareness
If local people fully understand the purpose of introducing marine snails to their reefs, they will be more likely to participate for the success of the management schemes, and poaching could be prevented. Information dissemination is essential, so prior to the transplantation, a series of public awareness programs should be conducted like seminars in different areas. Also, mass media like television, radio and newspapers should be used (Plate 34).
Plate 34. From MATANGI TONGA January–March 1997.
4.5.2 Community-Based Management After the public awareness programs are complete, the community where the shells will be introduced should be given intensive lectures and workshops on how to handle these shells. This process is aimed to promote better understanding and to let the people in the community do the releasing, protecting, and daily monitoring of the seeds. In this way, community members will assist in the management of the introduced species (Plate 35).
4.5.3 Genetic Diversity for Broodstock
Parent shells in different combinations ensure gene variety, and should be considered with great care. (Yamakawa, personal communication). Genetic diversity should be managed carefully by seeding many parent shells, selecting appropriate release locations, and managing the resources wisely.
Many parent shells should be seeded for the following reasons.
Changing both parent shells during the spawning process enhances gene variety: for example, three males and three females make nine possible combinations, therefore greater gene variety).
Wild parent shells are preferable to those made artificially.
Theoretically, the larger the genetic pool, the better the gene variety; practically though, in an artificial environment like a farm, having 300–500 varieties of genes is recommended for good gene diversity.
Each island should have its own variety of shells, so parent shells collected mixed with some local ones will enhance seeding variety.
Ideally, parent shells should be completely replaced each year. In practice, this is can be difficult, but it should be a long-term planning goal.
It is highly recommended that each hatchery keep 30 varieties per year, in order to maintain 300 varieties every ten years.