If you haven't already, check out my post on Growing Baby Oysters. This is part two, what kills the mollusk?
So, it all starts when 5 moms and 5 dads are placed in a tank to release their sperm and eggs. Since this is a controlled environment and not the vast ocean, there is a high risk that these mollusks will immediately eat the sperm and eggs. How? Well, they are filter feeders, constantly sucking water in and out of their gills and dieting the nutrients in the water. So, when 72 million eggs and sperm are released in a tank, there is a major chance these small gametes will be sucked right back into the adults. So, the moms and dads are smartly removed from the tanks an hour after they spawn.
Now, at this young age survival rate is incredibly high but the numbers start to dwindle. One thing to consider is that a hatchery producing mollusks for the cultured pearl industry is extremely discriminatory. Probably more so than a hatchery producing food. Why? The health of the mollusk will have a great bearing on the quality of the pearls and the resiliency to survive. These are incredibly important factors when producing pearls.
The mollusks are kept, fed and maintained for a year and a half before they are turned over to the cultured pearl farm for nucleation. They are constantly monitored for a steady growth rate. So, the heartier/larger mollusks are always separated from the smaller mollusks. The mollusks must show a strong growth rate to be considered for nucleation.
Now, there is a big culprit that kills the mollusk and that is water pollution. Fresh seawater is used in the breeding and growing tanks so if the seawater is contaminated with pollution, the mollusk will experience significant trouble. Remember how I love to say pearls ensure a high water quality? That is because the mollusks cannot survive or thrive involuted water. So, what happens to the youngsters in these tanks?
When the seawater is contaminated you see a high number of the mollusks simply die. They also start to swim erratically and they cilia is very short, shorter than usual.
Ocean water in the Philippines is best in the summertime so hatcheries like to work in the summer. During the rainy season, there can be a high amount of bacillus in the water and this bacteria can be fatal to the young mollusks. Many people living on the islands of The Philippines are still learning about the importance of sanitation in the ocean. Poor sanitary habits and detrimental practices like cyanide fishing can be detrimental to the lives of mollusks.
If all goes well, though the hatchery only needs to breed the mollusks twice a year and they can grow many thriving young mollusks for the cultured pearl farm!