In the entire planet, bivalves like the oyster, mussels, and clams are the most significant cultivable creatures. Among these, mussels like P. viridis and P. indica make up the majority of cultivable species. Environmentally friendly methods for mussel production have been developed by the Central Marine Fisheries Research Institute (CMFRI). CMFRI has recently started to promote mussel culture in all of Kerala's coastal districts.
Growth of mussel
A green mussel grows at a pace of 8mm to 13.5mm every month. Brown mussels and green mussel reach lengths of 65mm and 36.5–40g in 5 months and 80–88mm and 36.5–40g in 5 months, respectively, under typical cultivation conditions. Compared to mussels from the natural bed, mussels raised in captivity produce more meat. The average weight of meat production that is edible ranges from 27.2% to 33.3% of the overall weight. The two most crucial metrics for determining if the culture system is successful are likely growth in length and weight. Numerous environmental parameters, including water quality, food availability, settling density, water velocity, and tidal exposure, have an impact on mussel development.
Reproduction of Mussel
Each of the green mussel's sexes releases two streams of gametes into the water to start the spawning process. Additionally, the presence of other spawning individuals nearby and a decrease in salinity have both been shown to trigger spawning. The average female releases 5 lakh eggs. After fertilization, the zygote changes into movable, trochophore larvae, which takes seven to eight hours. The veliger larval stage is achieved after 16 to 19 hours, at which point the internal body components are covered by the larval shell, which is growing a robust ciliated velum. The D-shaped larvae with a straight hinge transform into pediveligers, which have a pedal organ and a working foot before sinking to the bottom.
In eight to twelve days, the larvae change into their adult form. The larva attaches itself and secretes the first byssal threads in 10 to 12 days. Organ system changes occur, and spat, a post-larval having features of an adult mussel, is generated. Of the mussels examined to date, Perna viridis has the fastest rate of growth. Because of the enhanced productivity of the water at that level and a condensed region of temperature and salinity variation, the green mussel grows at its maximum 2 meters below the surface.
P. viridis feeds on suspensions. This species consumes tiny phytoplankton, zooplankton, and other suspended fine organic material, making it an effective filter feeder. The high salinity and a profusion of phytoplankton are factors in the green mussel's rapid development. The green mussel can survive in murky water and has a strong tolerance for low salinities. It also fared better when exposed to the atmosphere.
Mussel Culture Techniques
Choice of Location
It is possible to farm in estuaries and open seas that are not subject to heavy wave action. Mussels thrive best in clear saltwater with high plankton production (17–40 g chlorophyll/l). The necessary planktonic food will be brought by moderate water current (0.17-0.25m/s at flood tide and 0.25- 0.35m/s at ebb tide), which will also remove the excessive build-up of pseudofaeces and silt in the culture region. The water should be between 26°C and 32°C, with a salinity of 27–35 ppt. The area should be free of sewage, industrial, and residential contamination.
Open sea farming
In open sea farming, the site's depth should be greater than 5 meters, with little turbulence, vigorous wave action, and high primary production. Techniques for long line and raft cultivation are excellent for open sea farming. Long-lined mussels are covered by immature mussels that naturally settle and other fouling creatures. For the construction of long lines and rafts, readily accessible materials can be used effectively. This farming has drawbacks like poaching and unanticipated climate change. The best places for mussel farming are protected bays.
Techniques For Mussel Farming
Rack method
Estuaries and shallow bays are suited for this technique. The racks are constructed by aligning vertically and horizontally bamboo or casurina poles, attaching and lashing with nylon or coir ropes.
Raft method
For situations on the wide sea, this approach is excellent. Strong bamboo or casuarina poles are used to construct square or rectangular rafts. The raft's buoyancy is created by securing five 200-liter barrels, one at each of the four corners and one in the center (metal oil barrel painted with anticorrosive paint or synthetic material).
Long-Line Method
In open ocean circumstances without protection, this approach is thought to be optimum. Concrete blocks and nylon ropes are used to secure the long lines and barrels in place at each end. The long line is hung by seeded ropes.
Horizontal Culture
This approach works well in shallow waters with a low water column. However, both ends will be extended and attached in vertical poles placed on opposing sides of the farm construction. Originally, the seeded rope was suspended by tying upward by ropes to horizontal poles. The majority of farmers use this technique in Malabar's estuaries.
Bouchot Culture
Farmers participated in the Bouchot (stake cultivation) method, which was used in the shallow Ashtamudi Lake near Dalawapuram, Kollam. Mussels (20–25mm in size) were harvested from the estuary and sown on bamboo splits of one meter in length and 1.5 kilograms per pole. Within three months, a bamboo split weighing 12 kg per pole was produced.
Provision of seed
Farmers and mussel fishermen frequently clash over the seeds needed for cultivation, which are currently obtained from traditional fishing grounds. More disputes took place this year than in previous years. Therefore, it is imperative that more spat collectors be installed along the shore to guarantee seed availability to the farmers.
Marketing
The main cultured mussel harvesting season is between April and May, and farmers are compelled to sell it before the monsoon arrives to prevent widespread mussel death brought on by freshwater intrusion into the backwater system. Only a few processing factories now buy cultured mussels from farmers, thus the local market is saturated with them during these months, causing prices to drop and negatively harming the operation's profitability.
