Group Presentation (Video)

Our main topic for this video is about pros and cons of aquaculture. So please enjoy and watch our video. Thank you :)

TOPIC 3: Green-lipped mussel - Life Cycle and System

The green mussel also called green lipped mussel, Perna viridis belongs to the family Mytilidae (GSFMC 2005). Perna viridis is native and widely distributed in the coastal areas of the Indo-Pacific region. It has been introduced around the world through ship ballast, hull fouling and experimental farming. Other members of the genus Perna are found in New Zealand (Perna canaliculus) and in coastal South America and Africa (Perna perna).

• Culture of the green mussels, Perna viridis, holds considerable potential in Malaysian coastal waters (Marzuki 1998).
• The production increased to 7702 mt in 2003 from 5785 mt in 2002 (FAO 2005).
• Most of the production is in the western part of Peninsular Malaysia in the states of Johore, Melaka, Perak, Selangor, Negeri Sembilan and Penang and a little in the state of Sabah in East Malaysia (DOF 1996).
• In the state of Sarawak, there is no production record of green mussel.
• The brackish water aquaculture in Sarawak is black tiger shrimp culture in ponds, marine fish culture in floating net cages and crab culture in pens.
• However, it is reported that shellfish such as giant clams, razor clams and white clams are found naturally and are becoming important for commercial, recreational and subsistence activities in Sarawak (Oakley 2000).
• Green mussel appears to be already consumed in Sarawak and the import of this product increased from 1 mt in 1996 to 7 mt in 2000 (Pada Bijo, personal communication).
• On the other hand, Malaysia was importing 491 mt of mussel in 2003 even though the green mussel production in that year reached 7700 mt (FAO 2005).
• Thus, the introduction of green mussel farming in state of Sarawak could meet local demand as well as contribute to the balance of trade or export earnings of the nation.

Life cycle of green-lipped mussel

Site selection for green-lipped mussel culture

Figure 1: Factors that need consideration when selecting sites for mussel culture

Culture methods 

Aypa (1990) describes three main categories of culture methods for mussel cultivation, bottom culture growing mussels directly on the bottom, intertidal and shallow water culture in the intertidal zone, and deep water culture. These are then divided into a variety of culture methods as practiced in many countries, based on the prevailing hydrographical, social and economic conditions. The RAS (1991) describes the three culture methods currently in use for the culture, Perna viridis; raft, stake and rack methods. All the methods in the cultivation of mussels can be assigned to one of two categories; they are either on bottom cultivation or off-bottom cultivation.

On-bottom culture

On-bottom culture or seabed culture is largely practiced in Europe especially in the Netherlands, Germany, Ireland and the United Kingdom (Spencer 2002). Bottom culture is based on transferring wild mussels to a sheltered culture plot where the density is reduced to improve growth and fattening. Aypa (1990) mentioned in this culture system a firm bottom is required with adequate tidal flow to prevent silt deposition, removal of excreta, and to provide sufficient oxygen for the cultured animals. In the Netherlands, a bottom method is extensively practiced and completely depends on natural seeds. When the natural seeds are unsatisfactory for growing, the seedlings are often transferred by the farmers to richer ground until the marketable size is attained. Farmers in a certain locality of the Philippines practice a bottom method, which is used in shallow areas from 0.6 m at low tide and 3.6 m at high tide. The mussel seeds are collected from the bay using bamboo poles and after one or two months, the mussels are removed from the bamboo poles and laid at the bottom of estuary near the farmers‟residences.

Off-bottom culture

The culture methods under this category are practiced in intertidal zones and/or mussels are grown above the seabed and can be used to describe all other types of mussel farming, encompassing the whole spectrum from cultivation on stakes or poles, through to methods of utilising ropes or lines suspended from the sea surfaces. Spencer (2002) describes three principle methods of off-bottom culture, namely pole, raft and long line and, (Aypa 1990) categorised the farming into another three subcategories of methods namely fixed suspended cultivation, floating suspended cultivation and deep water cultivation based on local needs as explained below:

a. Fixed suspended cultivation

There are five culture methods under this subcategory namely rack culture, tray culture, wig-wam culture, rope-web culture and pole cultivation. All these methods are practiced in the Philippines except pole culture, which is practiced in France. All the methods are described by (Aypa 1990). Basically, these methods of cultivation require a fixed platform or structures for settlement and growth of the mussels. Furthermore, the cultivation occurs in soft and muddy seabeds, narrow tidal range, and water depths of 2-3 m. The collected spats grow to marketable size, 5 –10 cm in 6 –10 months.

The pole cultivation or „Bouchot‟culture method is the most significant culture practiced under fixed suspended cultivation (Figure 6). It was considered to be the original method for farming mussels (Gosling 1992) and produces more than 40,000 tonnes annually of France‟s farmed mussels (FAO 2005).

Figure 2: Diagrammatic representation of various culture methods (Gunnarsson et al. 2005)

b. Floating suspended cultivation
The development of floating suspended systems allows the mussel culture deeper coastal waters and more effectively exploits the high primary productivity of these areas. There are two main methods under this category, namely the raft culture method and the long line culture method (Figure 2). With this method of culture, the mussels are grown attached to suspended ropes, which are tied to a raft. The raft is made of various types of structures. An old wooden boat with a system of outriggers built around it could be the raft. The other types could be a catamaran-type boat carrying some 1000 rope hangings, or an ordinary plain wooden raft with floats and anchors.

Figure 2: Production trend about green-lipped mussel in Malaysia 1986-2003 (FAO 2005)

Domestic market for mussels 

Malaysia‟s green mussel market is very large. In 2003, around 8000 mt of mussel were supplied to the market (FAO 2005). In addition Malaysia also imported fresh and frozen mussel to fulfil local demand. FAO (2005) reported that the import quantity of mussel increased from 311 mt in 2001 to 491 mt in 2002.

Source of supply	2000	2001	2002	2003
Cultured	11069	6880	5785	7702
Import	273	377	491	n.a

Table 1: The production and import quantity of mussel (mt) in Malaysia (FAO 2005)

Regional trade

There is a significant demand for mussels in Malaysia‟s neighbouring countries, which gives a great market opportunity. The import quantity of these countries shows an increasing trend as shown in Table (FAO 2005). 

Country	Mussel	2000	2001	2002
Singapore	Mussel meat frozen	241	201	339
Singapore	Mussels fresh or chilled	326	274	253
Brunei Darussalam	Mussel meat frozen	53	32	148
Brunei Darussalam	Mussels fresh or chilled	3	-	28
Thailand	Mussel meat frozen	16	59	110
Thailand	Mussels fresh or chilled	4	11	12

Table 3: The import quantity of mussels (mt) in Malaysia‟s neighbouring countries (FAO 2005)

 

Examples of products from green-lipped mussel

TOPIC 2: Future, Research, or Problems in Aquaculture

Future of Aquaculture

Aquaculture – protein provider for the world

During the 1970s aquaculture was a relatively insignificant industry, but today it is almost as productive as the ocean fishing sector. About 600 aquatic species are now raised in captivity, with different species being preferred for different regions. Experts predict that the importance of fish farming will increase even more in the future, because it has clear advantages over beef and pork production.

Towards more eco-friendly aquaculture

Aquaculture is expected to satisfy the growing world population’s demand for fish – and at the same time protect ocean fish stocks. Hopes are pinned on farming as an alternative to over-fishing. But the use of copious amounts of feed derived from wild fish, the destruction of mangrove forests and the use of antibiotics have given fish farming a bad name. Current research and development projects, however, show that environmentally-sound aquaculture systems are possible.

Aquaculture sector predicted to be increasing in year 2030 and provide majority of the world’s seafood

Problems / Issues of Aquaculture

Aquaculture, like any other industry, has its costs and benefits, as well as its proponents and opponents. As a result, there are impediments to aquaculture development in the world. Some of the concerns expressed about aquaculture are valid, while others are steeped in misconceptions and misunderstandings about the nature of aquaculture.

1)      Fish feed requirements

Farmed carnivorous fish, such as salmon, require a food source which is high in fish-derived proteins. This generally comes from wild capture fish at the bottom of the food chain, which are not usually marketed for human consumption.  There are two key challenges to developing a sustainable aquaculture industry. The first is to find a source of food for the farms which does not depend exclusively on wild fish being caught. The second is to ensure that any wild fish used as feed is caught in a sustainable manner. This is because removal of these species low in the food chain can have serious implications for fish stocks, the food web and other wildlife including sea mammals and seabirds.

2)      Sites in vulnerable habitats

There are a number of problems which stem from fish farms being located in inappropriate areas. These include vulnerable habitats (both terrestrial and marine), essential fish habitats or areas with high concentrations of wild fish. Some of the problems can include organic waste accumulation on the seabed under sea pens – resulting in localised degraded water quality sea lice and other disease transfer; and altered food webs from escaped individuals as described below.

3)      Escapees

When fish escape from a farm open to the sea, this can lead to problems for the wider ecosystem. This is because escaped farmed fish can interbreed with wild fish of the same species, resulting in genetic dilution (domestic farmed fish can have low genetic variation); they can spread disease; they can displace eggs of wild fish and they can put pressure on natural resources through competition with wild fish.

4)      Pollution

A range of chemicals can be used in marine aquaculture operations such as disinfectants, anti-foul ants and medicines (including vaccines). These marine pollutants can be toxic to wildlife and can cause significant damage to the wider ecosystem, especially anti-foul ants containing copper.

5)      Animal welfare

Fish welfare can suffer in an intensely farmed environment where the stock density (the weight of fish kept in a given volume of water) is too high. Fish welfare concerns apply to the farming, transport, and harvesting and slaughter process. The RSPCA has useful information on issues affecting fish welfare. Sea fish farms need to be better located in appropriate sites to avoid natural predators becoming a problem in the first place. The aquaculture industry would benefit from technological developments that prevent fish loss from predators without affecting the predator populations or their roles in ecosystem health.