Green Mussel (farmed, New Zealand)

New Zealand Green Mussels/ Copyright © Charlotte Knox

Perna canaliculus

Sometimes known as New Zealand Mussel.

This species is farm-raised.

Summary

Like other mussels, New Zealand's Green Mussels filter plankton and nutrients from the surrounding water, thereby improving water quality. Green Mussels are native to New Zealand, where they are farmed. Management there is strong; New Zealand's rigorous permitting process prevents habitat degradation by ensuring that farms are excluded from sensitive habitat areas.

Criterion	Points
Inherent Operational Risks	3.50
Feed	3.75
Pollution	4.00
Risk to Other Species	3.00
Ecological Effects	3.00
Final Score (average of criteria)	3.45
Color

Final Score	Color
2.60 - 4.00
2.20 - 2.59
1.80 - 2.19
1.40 - 1.79
0.00 - 1.39

Last updated May 10, 2007.

Inherent Operational Risks

Core Points (only one selection allowed)

General System Design:

An aquaculture system's design is a good overall proxy measure for the likely effect of the operation on the environment. For example, open systems (e.g., net pens and net cages) are more likely to have pollution, disease, and escape issues than closed systems (e.g., recirculating tanks). With shellfish, which don’t require supplemental food input, the more important question is whether they are harvested on or off of the bottom.

1.00

This species is raised in a high risk system (e.g., net pens; net cages).

2.00

This species is raised in a moderate risk system (e.g., most ponds; raceways; bottom culture of mollusks).

3.00

This species is raised in a low risk system (e.g., re-circulating closed system; suspended culture of mollusks; zero-discharge ponds).

All green mussels in the U.S. market come from New Zealand. Green mussels have been stated to be the most commonly eaten mussel in the U.S. (Floyd 2003), but conflicting data make it hard to determine the precise quantity of green mussels in the U.S. market (FAO 2004; SEAFIC 2000-03; NMFS stats 2004).

The only mussels that may be exported from New Zealand are those with the “Greenshell” trademark, which are required to be grown on suspended ropes. Product shipped overseas is therefore guaranteed to be ropegrown (Floyd, pers. comm. 7/7/04). Sealord's Greenshell mussel's have recently been approved as organic by Bio Gro New Zealand and the UK Soil Association. This product will soon be available in the U.S. (Floyd, pers. comm. 2004).

A mussel farm consists of a series of buoys held together by long lines attached to each side of the buoy. The line is anchored to the seafloor at each end. A series of weighted ropes, on which the mussels are grown, hang down from these lines. Juvenile mussel spat are wrapped to these ropes using a stocking mesh. The mesh later disintegrates, by which time the spat have attached themselves to the rope. They are then left to grow. When they reach a desired size, the rope is lifted and the mussels stripped from it (SEAFIC 2004).

Points of Adjustment (multiple selections allowed)

-0.25	Species is raised at a high stocking density; OR there is a high density of sites in the geographic region, with evidence of environmental impact.
-0.25	Operations do not incorporate best-available, cost-effective technology to reduce environmental impact.
-0.25	There are no effective zoning or permitting practices for siting of facilities.
-0.25	Government programs encourage expansion of high-impact systems.

+0.25	Species is raised at a low stocking density OR there is a low density of sites in the geographic region, which results in minimal impact to the natural ecosystem. Green mussels grow at high densities in the wild, so while they are stocked at high densities in aquaculture operations, this is not unnatural or problematic. If too much spat is seeded on a rope, the spat will simply remove itself, thus acting as an inherent control in maintaining natural densities (Floyd, pers. comm. 7/7/04). Depending on the farm, there are generally about 100-170 mussels per meter of crop rope at harvest size (Searle, pers. comm. 7/8/04). Tenures for mussel farming have been granted over 3,920 hectares (11,720 acres) (NZ Ministry of Fisheries 2004). Density of farms is higher in some regions than in others. A high density of farms can be problematic to the farmer because the upstream farm can filter out so much of the plankton that not enough remains for the downstream mussels (Floyd, pers. comm 7/7/04). We neither add nor subtract points here, because while densitites are high, there is minimal impact to the natural ecosystem.
+0.25	Operations incorporate innovative culture methods that limit environmental impacts (e.g., polyculture).
+0.25	There are effective zoning or permitting practices for siting and operation of facilities (e.g., mandatory consideration of hydrographic characteristics; requirements for site rotation). From 1971 to 1991, marine farming tenures were issued by way of lease or license from the Crown, under the Marine Farming Act. In 1991, The Resource Management Act revoked the provisions in the Marine Farming Act relating to issuing new leases and licenses, but maintained all previous licenses and leases. New Zealand's Resource Management Act extended regional council planning areas to include the land and sea from high water mark out to 12 miles seawards, (the coastal marine area or CMA) (NZ Ministry of Fisheries 2004). There are 17 regional councils in New Zealand but not all have coastal space and not all those with coastal space have marine farms. The main regional councils for marine farming are the Marlborough District Council, Environment Waikato, The Auckland Regional Council, The Southland Regional Council, Environment Canterbury, The Northland Regional Council, The Tasman District Council, Environment Bay of Plenty, and Hawkes Bay Regional Council (Clarkson, pers. comm. 2004). The Resource Management Act requires councils to prepare a regional coastal plan relating to their CMA, and to provide for marine farming where considered appropriate. The plans regulate the activities that may take place in the CMA and take into account environmental and other effects marine farming may have. The Act also regulates the placement of structures and occupation of space in the CMA. To establish a marine farm now, the relevant regional council must first issue a resource consent (or a certificate of compliance). Depending on the provisions of the council coastal plan there are varying degrees of consultation required before a resource consent is given. In all instances the general public including local interest, recreational users and environmental groups have a say in whether a marine farm will be allowed to go ahead. An Environment Court process is set up for instances where agreement cannot be reached. In addition to ‘general approval’ the regional council will undertake an environmental effects assessment which will consider any undue adverse effects on fisheries resources and also navigation, and amenity issues (Clarkson, pers. comm. 2004). Once consent is granted, the Ministry of Fisheries must issue a marine farming permit (NZ Ministry of Fisheries 2004). Beginning in March, 2002, the MFE enacted a two-year moratorium of coastal permits for aquaculture activities. The amendment was extended, and the moratorium now expires on 31 December 2004 (MFE 2004). The Ministry of Fisheries and the Department of Conservation are currently working on The Resource Management (Aquaculture Reform) Bill, which will provide the framework for the management of New Zealand's marine farming industry. The bill is expected to be introduced into Parliament in late 2004 (MFE 2004). Farmers are subject to Maritime Safety Law, the Food Act the Animal Products Act, the New Zealand Fishing Industry Agreed Implementation Standards, the Local Government Act, The Resource Management (Marine Pollution) Regulations, the Health and Safety in Employment Act, the Marine Mammals Protection Act and the Marine Reserves Act (Clarkson, pers. comm. 2004).
+0.25	Government programs preferentially encourage the expansion of low-impact systems over high impact systems. Resource Management Act has strict zoning provisions in place, which encourage the expansion of low-impact systems (Floyd, personal communication, 2004).

3.50	Points for Inherent Operational Risks

Feed

Core Points (only one selection allowed)

Ecological Footprint of Feed:

"Trash" fish, frequently used in developing countries, is an industry term used to refer to whole fish or fish parts fed to farmed fish without being processed into fish meal and fish oil.

Twenty percent was selected as a cut-off because carnivorous species (e.g., salmon; eel; tuna; cobia; etc.) generally consume greater than twenty percent fish products (fishmeal, fish oil, or trash fish), while omnivorous or herbivorous species (e.g., catfish; tilapia; carps; etc.) consume less than twenty percent fish products.

1.00	Typical aquaculture feed includes high levels of fishmeal, fish oil, or "trash" fish (i.e., >20% of the feed; e.g., salmonid feeds).
2.00	Typical aquaculture feed includes moderate levels of fishmeal, fish oil, or "trash" fish (i.e., <20% of the feed; e.g., tilapia and catfish feeds).
3.00	No feed is used (e.g., mollusks and seaweeds) or typical aquaculture feed includes no fishmeal, fish oil, or "trash" fish (e.g., paddlefish; filter-feeding carps). As mussels are suspension feeders, no feed is used in the farming of New Zealand Green mussels. Unlike other mollusks, there is no hatchery phase, during which algae may be added to seawater as feed for larvae (Gosling 1992).

Points of Adjustment (multiple selections allowed)

-0.25	When fish products are used, the major sources score low on the Wild-Caught Fisheries Ranking System.
-0.25	Feed contains greater than 10% of fish products and public or private sectors are not working to reduce fish content in feed.
-0.25	Feed conversion ratio (FCR) is high (i.e., >2.0; e.g., eel).
-0.25	Government policy promotes research, development and commercialization of carnivorous or other highly fishmeal-dependent species.

+0.25	When fish products are used, the major sources score high on the Wild-Caught Fisheries Ranking System; OR the source is innovative and ecologically sound (e.g., fisheries byproducts); OR no feed is used. No feed is used in the culture of New Zealand Green mussels (Floyd 2004).
+0.25	Feed contains less than 10% of fish products OR public and private sectors are working to reduce the fish content in feed; OR no feed is used. No feed is used in the culture of New Zealand Green mussels (Floyd 2004).
+0.25	Feed conversion ratio (FCR) is low (i.e., <1.3; e.g., salmon); OR no feed is used. No feed is used in the culture of New Zealand Green mussels (Floyd 2004).
+0.25	Government policy promotes research, development and commercialization of herbivorous species or other species not highly dependent on fishmeal.

3.75	Points for Feed

Pollution

Core Points (only one selection allowed)

Typical effluent treatment procedures:

1.00	Effluent is not treated before discharge (e.g., salmon net pens).
2.00	Effluent is partially treated before discharge (e.g., infrequently discharged effluent from catfish ponds).
3.00	Effluent is substantially treated before discharge (e.g., recirculating shrimp systems; settling ponds; reconstructed wetlands); OR treatment is not necessary because supplemental feed is not used (e.g., molluscs or seaweeds). Treatment is not necessary because supplemental feed is not used (Floyd 2004).

Points of Adjustment (multiple selections allowed)

-0.25	Operations have demonstrated negative impacts on water quality or sediment/benthic characteristics (e.g., elevated nutrient levels; algal blooms; altered benthic communities).
-0.25	Pollutants (e.g., pesticides; parasiticides; antibiotics; plastic; nets; dead fish) are frequently discharged into the environment or otherwise not appropriately discarded.
-0.25	Effluent regulations do not exist, are lax, or are poorly enforced, which allows for degradation of the aquatic environment.
-0.25	Available technologies and practices to reduce or recycle waste (e.g., feed sensors; low-pollution feeds) are not used.

+0.25	Operations generally improve water quality or sediment/benthic characteristics (e.g., oyster farms). Mussels themselves improve water quality by filtering out algae and other plankton, reducing chlorophyll, nutrient and suspended solid levels (Downey, pers. comm. 2004).
+0.25	Chemicals (e.g., pesticides; parasiticides; antibiotics) are rarely or never used. No chemicals are used to farm New Zealand Green mussels (Floyd 2004).
+0.25	Robust water quality regulations exist (e.g., permits required; discharge caps; strong enforcement), and regular monitoring occurs. There are strong water quality controls in effect. New Zealand is one of only five countries approved by the USFDA's National Shellfish Sanitation Program. The Green mussel industry has developed a voluntary Environmental Management Strategy and Code of Practice; and has a proven Algal Bloom Monitoring Programme (Floyd 2003). Sealord, the biggest producer of Green mussels, has been developing innovative seawater farm monitoring programs. For the last 5 years, they have tested samples of mussel meat and seawater twice a week for a wide range of nutrients, contaminants and residues (Sealord FAQ 2004).
+0.25	Innovative methods and practices to reduce or recycle wastes are used (e.g., integrated systems; effluent and solid wastes used as terrestrial fertilizer); OR innovative methods and practices are not needed because raising this species does not create waste. Innovative methods and practices are not needed because raising Green mussels does not create waste.

4.00	Points for Pollution

Risk to Other Species

Core Points (only one selection allowed)

Frequency and Impact of Escapes:

1.00	Farmed species regularly or intermittently escape into the wild AND escapes are non-native to the area or otherwise pose a risk to native populations or ecosystems (e.g., most non-native fish raised in outdoor facilities).
2.00	Escape frequency is not known OR farmed species is native to the area where it is raised and poses minimal risk to native populations or ecosystems (e.g., channel catfish in the US; most native mollusks). New Zealand Green mussels are being farmed in New Zealand where they are native, posing minimal risk to wild populations.
3.00	Farmed species never (or virtually never) escape to the wild (e.g., species is raised in bio-secure facilities).

Points of Adjustment (multiple selections allowed)

-0.25	This farmed species has been known to survive in the surrounding ecosystem if it escapes; OR would likely survive given its physiological requirements.
-0.25	This farmed species is known or is likely to compete with wild species for food or habitat if it escapes; OR this species is known or is likely to compromise the genetic integrity of the wild species (e.g., through spawning disruption, genetic introgression or establishment of feral stocks) if it escapes.
-0.25	This farmed species is known or is likely to amplify and transmit disease or parasites to wild populations (e.g., infectious salmon anemia or sea lice infestations) if it escapes.
-0.25	Regulatory authorities are not adequately addressing the risks of escape or spread of disease associated with farming this species.

+0.25	This farmed species has not been known to survive in the surrounding ecosystem if it escapes; OR would not likely survive given its physiological requirements; OR farmed species is a native mollusc. New Zealand Green mussels are native to the areas where they are farmed.
+0.25	Operations employ management protocols and techniques to limit the ecological impacts of escaped farmed fish (e.g., triploidy; sterilization); OR it’s unlikely that escaped individuals will either compete with wild species for resources, or compromise the genetic integrity of wild species. Because operations use naturally settling local spat, it is unlikely that escaped Green mussels would compromise the genetic integrity of wild species.
+0.25	Operations employ effective disease and parasite management protocols (e.g., fallowing of pens; retaining water when disease outbreak occurs); OR incidence of disease or risk of retransmitting disease is low. Incidence of disease is very low (Floyd, pers. comm. 7/7/04). There was an outbreak once of a disease that is believed to be a virus. The outbreak was contained to a small area, and was short-lived (Searle, pers. comm. 7/9/04).
+0.25	Regulatory authorities are addressing the risks of escape and spread of disease associated with farming this species. The Ministry for Agriculture and Forestry and the Ministry of Fisheries together have issued guidelines for Exotic Disease Response Plans for aquaculture industries in New Zealand. The New Zealand mussel industry is among the first of such industries to have developed its own Exotic Disease Response Plan in line with these guidelines. The Exotic Disease Control Plan has been established so that New Zealand mussel farms can meet the Ministry of Agriculture and Forestry Biosecurity Authority (MAF BA) requirements to control the potential spread of exotic diseases in the aquaculture industry. Also the industry has a number of regulatory authority-endorsed voluntary codes of practice that address biosecurity issues, including a comprehensive national mussel spat transfer program and a seed transfer code of practice. The industry’s Environmental Management System sets out best practice outcomes in relation to movement of material, biosecurity and disease transfer (Clarkson, pers. comm. 2004).

3.00	Points for Risk to Other Species

Ecological Effects

Core Points (only one selection allowed)

Ecological sensitivity of site used for operations:

1.00	Operations are generally located in areas of high ecological sensitivity (e.g., coastal wetlands; mangroves).
2.00	Operations are generally located in areas of moderate ecological sensitivity (e.g., coastal and nearshore waters; rocky intertidal or subtidal zones; river or stream shorelines). Farms are located in sheltered to semi-sheltered areas where there is sufficient depth of water at low tide to keep the drop lines off the bottom (NZ Ministry of Fisheries 2004). The first offshore license was recently granted (Sealord 2004). Offshore farms are likely to become more common as demand for Green mussels increases.
3.00	Operations are generally located in areas of low ecological sensitivity (e.g., land that is less susceptible to degradation such as land formerly used for agriculture or land previously developed).

Points of Adjustment (multiple selections allowed)

-0.25	Farming this species causes substantial damage to surrounding habitat, ecosystem or other resources (e.g., groundwater depletion; stream diversion; saltwater intrusion; soil salinization; loss of habitat for juvenile fish; loss of flood control; dredging hard bottoms; etc.).
-0.25	Harmful or lethal predator deterrents are used (e.g., bird/seal shootings; acoustic deterrent devices); OR operation otherwise harms wildlife (e.g., dolphin/seal entanglement; disrupting migration routes; bird/animal shooting).
-0.25	If seed is collected from wild sources, the intensity of collection is high enough to result in depletion of brood stock, wild juveniles, or associated non-target organisms (e.g., collection of postlarvae shrimp).
-0.25	Government policy encourages aquaculture operations to locate or expand in areas of high ecological sensitivity.

+0.25	Operations enhance habitat structure or function (e.g., constructed wetlands). Mussel farms tend to act as man made reefs, thereby attracting large numbers of small fish (SEAFIC 2004).
+0.25	Predator deterrents are not used OR predator deterrents are used but are not harmful or lethal (e.g., predator exclusion nets), AND operation does not otherwise harm wildlife. There are virtually no predators that effect Green mussels when they are grown on ropes. Starfish are a problem only where mussels are too close to the sea bottom. There is some stripping of young mussels off the ropes by juvenile fish, especially snapper (Floyd 2003). Predator deterrents are not used (Floyd, pers. comm. 7/7/2004)
+0.25	Seed comes predominantly from hatcheries or on-farm sites (e.g., seed for trout); OR if seed is collected from the wild, it does not deplete brood stock, wild juveniles, or associated non-target organisms (e.g., collection of oyster or mussel spat). Spat is collected from the wild, either from direct settlement onto fibrous collecting ropes (~20% of all spat for farms throughout New Zealand), or on macroalgae that wash up on Ninety Mile Beach (~80% of spat) (MFE 2000). The Ministry of Fisheries has recognized that there are no sustainability issues regarding this collection. Spat collectors take a small proportion of the spat/weed that washes up on the beach. That which is not collected dies on the beach, and would not have contributed to wild stock anyway (Clarkson, pers. comm. 2004). There is no evidence that wild populations or non-target organisms are being harmed by the collection of seed for aquaculture. The Department of Conservation have not expressed any concerns in relation to shore birds and other non-target organisms on the beach (Clarkson, pers. comm. 2004).
+0.25	Government policy encourages the growth of aquaculture operations in areas of low ecological sensitivity; OR protects sensitive habitats from aquaculture operations (e.g., prohibitions on cutting mangroves). There is a rigorous approval process for aquaculture operations. The project must first be approved in accordance with the Resource Management Act. The Ministry of Fisheries then puts an additional two-test requirement. The two tests are a) whether there are any undue adverse effects on fisheries resources (ie any living organism that contribute to the make-up of the ecosystem) and b) whether there are any undue adverse effects on fishing (ie on the ability for recreational, customary or commercial users to access fish). Test a) (undue adverse effects on fisheries resources) is tested twice, once during the RMA process and once again during the Ministry of Fisheries process. There is a clear mandate from both central and local government to ensure that aquaculture does not occur in high sensitivity areas. General policy has been to site farms over muddy bottoms only in order to ensure this (Clarkson, pers. comm. 2004).

3.00	Points for Ecological Effects

References

Clarkson, Rebecca. Executive Officer. New Zealand Mussel Industry Council. Personal Communication. 24 August 2004.

Downey, R., Executive Director, Pacific Coast Shellfish Growers Association. Personal Communication. May 18, 2004.

FAO (2004). FAO Fisheries Department, Fishery Information, Data and Statistics Unit. FISHSTAT Plus: Universal software for fishery statistical time series. Version 2.3.

Floyd, Bill. Director, Floyd Marketing Ltd., New Zealand. Contract Manager, Sealord Shellfish New Business Unit. Personal Communication. 7 July 2004.

Floyd, Bill. 2003. Greening The Mussel: A Presentation to the Institute for Social Economic and Ecological Sustainability Aquaculture Workshop, University of Minnesota, July 2003.

Gosling, Elizabeth (editor). 1992. Developments in Aquaculture and Fisheries Science – 25. Elsevier Science. Amsterdam, The Netherlands.

Ministry for the Environment (MFE). 2004. Aquaculture Reform. Available online at: http://www.mfe.govt.nz/issues/resource/aquaculture/overview/. Accessed 7 July 2004.

New Zealand Ministry of Fisheries. 2004. Aquaculture in New Zealand. Available online at: http://www.fish.govt.nz/commercial/aquaculture/about_index.html.Accessed July 7, 2004.

NMFS Trade Statistics. http://www.st.nmfs.gov/. Accessed July 7, 2004.

New Zealand Seafood Industry (SeaFIC). Green Mussels. Available online at: http://www.seafood.co.nz/business/fishaqua/species/mussels.asp. Accessed 29 June 2004

New Zealand Seafood Industry (SeaFIC). New Zealand's Principal Seafood Exports: 2000-2003. Available online at: http://www.seafood.co.nz/doclibrary/exportstats/PrincipalFishEXPORTS00-03.pdf. Accessed 29 June 2004.

Sealord. 2004. Growing and Harvesting Greenshell Mussels. Available online at: http://www.sealord.co.nz/xml/default.asp?globalSubPage=seafood2. Accessed 7 July 2004.

Sealord Organically Certified Mussels FAQ Sheet. 2004.

Searle, Lance. Science & Research Manager. Sealord Group Ltd. Personal Communication. 8 July 2004.