From: Rob Brumbaugh []
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Subject: The Clamor Special Edition: January 2009


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January 2009
Distributed by The Nature Conservancy's Global Marine Initiative

Towards a South American Network for Shellfish Conservation and Restoration

Since 2007, a team of scientists assembled by The Nature Conservancy, with funding support from The Kabcenell Foundation, has been developing a global-scale assessment of native bivalves that form reefs and beds: Global Shellfish Reefs at Risk.  In South America, we exchanged information with a number of active researchers working on oyster and mussel ecology and management, and received invaluable input to our analysis via expert surveys (translated into Spanish). Along with an extensive literature search, we were able to generate rough estimates on some shellfish populations within estuaries and overall condition at an ecoregion scale. To date, we are unaware of any studies that more directly measure the extent or rate of decline for South American shellfish populations. This may be due to a lack of interest in these systems, but is probably also limited by the amount of economic support this kind of research receives in South American countries.

Given the results of our initial surveys and literature reviews, we felt that there was an urgent need to raise awareness on shellfish issues on the continent and to focus our scientific colleagues on some of the most pressing data gaps. The collection of scientific data that describes the condition (degradation) of shellfish populations will surely have cascading effects, raising interest and promoting more conservation and restoration programs. Thus, we felt that early involvement of local scientists and managers as a next step in the Shellfish Reefs at Risk Project was a prerequisite to the development of continental-scale conservation network directed to improve shellfish condition in South America.

To this end, we convened a workshop during the VII Latin-American Malacological Congress (Valdivia, Chile, November 8-9;, inviting experts from Colombia, Venezuela, Brazil, Uruguay, Argentina, Chile and Perú. Participants were asked to: 1) present updates on the current situation of oyster and mussel conservation in their countries;  2) identify case studies focused on conservation action, including shellfish restoration projects; and 3) help to write a brief national report summarizing shellfish condition information from different locations, using a common reporting structure. 

Since most of the workshop participants are directly involved with shellfish stock assessment and management or are engaged in current conservation or restoration programs in their nations, they provided invaluable insights on these topics.  The most troubling finding from the workshop was that nearly half of the assessed shellfish populations were either moderately or highly threatened by over fishing and environmental degradation.

We are now preparing workshop proceedings for publication in an appropriate scientific journal.  Another primary outcome from the workshop was the creation of a participative South American Network on Shellfish Conservation and Restoration, involving scientists from around the continent. This network will serve to bolster conservation and/or restoration initiatives, link research teams and provide a framework to pursue additional financial support for new and/or ongoing conservation initiatives that benefit South American shellfish populations.

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Meeting Participants and Affiliations
Alvar Carranza, Dirección Nacional de Recursos Acuáticos, Uruguay; Unidad de
Ciencias del Mar, Facultad de Ciencias, Uruguay;

Omar Defeo, Dirección Nacional de Recursos Acuáticos, Uruguay; Unidad de Ciencias
del Mar, Facultad de Ciencias, Uruguay;

Adriana Gracia, Instituto de Investigaciones Marinas y Costeras, Colombia;

Alex Gamarra, Instituto del Mar del Perú;

Marcela Pascual, Instituto Alte. Storni, Argentina;

Marcelo Henriques, Instituto de Pesca, Sao Paulo, Brasil;

Luis Prado, Pontificia Universidad Católica de Chile;

Luis Leon, Universidad del Oriente, Venezuela;

César Lodeiros, Universidad del Oriente, Venezuela;

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Country Summaries

In northern Argentina, the yellow clam, Mesodema mactroides, and the coquina clam, Donax hanleyanus, have been heavily exploited. Other infaunal bivalves that support small-scale artisanal fisheries include the purple clam, Amiantis purpurata the geoduck, Panopea abbreviata, and the razor clam, Ensis macha. Crassostrea gigas was introduced in 1981 and now covers nearly 50% of rocky substrata in Anegada Bay (Buenos Aires). This population is expanding towards the South of the bay, invading the coast of the neighbouring province of Río Negro.Among mussels, the blue mussel Mytilus chilensis and the ribbed mussel Aulacomya ater covers rocky intertidal shores along the coasts of the provinces of Santa Cruz and Tierra del Fuego.

Restoration efforts are now focused on two species: the mussel Mytilus platensis and the flat oyster, Ostrea puelchana, both in North Patagonian Gulfs. M. platensis has been exploited by industrial dredging (1983-1992), artisanal dredging (2002-2007), and diving (2001-2008). The mussel populations declined in all the gulf grounds, reaching very low densities and poor recruitment. Dredging and absence of fishing regulations are identified as possible causes of population decline. A project is about to begin to restore the population of El Sótano, a traditional mussel bed located in an area characterized by strong recruitment.

The San Matías Gulf offered the rare opportunity of studying the structure of one of the few natural and untouched flat oyster populations in the world, the puelche oyster. The information gathered from extensive surveys performed in 1985 support a fishing closure in 1980. Unfortunately, the cultured stocks suffered heavy mortality in 1996, likely from a combination of clandestine small-scale fishing and other anthropogenic factors. This species is particularly vulnerable to exploitation because of its common cluster habit and also its peculiar reproductive biology with carriage of dwarf males, a feature that makes it a unique case among bivalves.

Restoration and conservation efforts are being developed to: 1) evaluate the condition of the three main grounds and compare them with prior surveys; 2) determine the age structure oyster populations; 3) assess biomass and demography of San José populations; and 4) initiate seeding experiments to evaluate hatchery seed for restoring the most severely depleted beds.

Several oyster and mussel species can be found in estuaries, mangroves and rocky outcrops along the Brazilian coast.  The brown mussel Perna perna is the most important species in Southern Brazil, both in terms of landings and economic value. The estuarine mussels M. Charruana and M.guyanensis and mangrove oysters Crassostrea spp. are also exploited, mainly for local consumption.  In subtropical areas of Brazil, the uncontrolled exploitation of natural beds of Mytella spp. has raised concerns about the sustainability of these fisheries. Up to a 50% decrease of stocks in Mundaú Lagoon, Alagoas, can be linked with shifts in local climate, since an extended rainy season is increasing freshwater inflow in the system. A 60% reduction in stocks of this species has also been reported for Espirito Santo state.  Decreases in stocks of P. perna in Sao Paulo are attributed to effects of global climate change and overexploitation. Some mangrove oyster populations are being exploited close to their maximum sustainable yields, and are also threatened by the reduction of mangrove habitats.

There are a number of ongoing initiatives linking poverty alleviation with sustainable extractive activities in Pernambuco, Rio Grande do Norte, Paraíba, Bahia, Sao Paulo and Santa Catarina states.  To this end, US$ 3,127 is being invested in Pernambuco, Rio Grande do Norte and Paraiba. The Brazilian model of co-management for natural resources known as “reservas extrativistas” (RESEX), developed with fishers, government agencies and partners in Sao Paulo and Santa Catarina are considered a promising tool to conserve native shellfish populations in the country.

Mangrove oyster harvesting in Mandira
Extrative Reserve, Sao Paulo State

Aquaculture facilities in Bertioga Channel, Sao Paulo State

Several bivalves are important habitat-forming species along the Chilean coast. The small, non-exploited mussel Perumytilus purpuratus is a dominant competitor in rocky intertidal environments.  Mytilus chilensis is the main cultured mussel in Chile; prior to 1983, about 10,000 tons of this species were landed from wild fisheries.  Aquaculture production of M. chilensis began in 1983 and by 1985 added an additional 10,000 tons to the annual landings.  Since then, aquaculture has grown exponentially; in 2007, 153,500 tons of M. chilensis were landed with aquaculture representing 98% of this figure.
Choromytilus chorus is distributed from Peru to Cape Horn, and it is a secondary target-species in mussel fisheries and aquaculture in Chile. Aulacomya atra is distributed from Peru to Cape Horn on the Pacific coast; and also extends along the Atlantic coast up to Argentina. It is also a secondary target-species in mussel fisheries and aquaculture. Ostrea chilensis is distributed from Ecuador to Cape Horn on the Pacific. This species was rapidly over-exploited since the fishery started in 1978.

All the exploited species present several conservation problems. A. atra is heavily affected by environmental phenomena, particularly El Niño events which contribute to decreases in the population.  The recent introduction of Mytilus galloprovincialis has yet to be fully evaluated as a threat for native mussels in the Chilean coast, but in the future this species could represent a serious threat as dominant competitor, displacing native species of mussels.

Several management policies have been adopted to help ensure long-term sustainability of native habitat-forming bivalves.  First, all exploited species have minimum legal size limits for extraction.  Second, the Fishery Subsecretary has created two genetic reserves aiming to protect the stocks of C. chorus and O. chilensis. The implementation of Coastal Marine Protected Areas (CMPA) opened new avenues for conservation of bivalves in Chile, and the recovery of natural banks of Choromytilus chorus in Lafken CMPA has been reported. Third, re-seeding is being attempted with A. atra and C. chorus, but there are no reported results for these experiences. For Choromytilus chorus, it has been shown that the area must be large enough to ensure the presence of several patches with asynchronic recruitment and the presence of certain species of algae to promote successful recruitment.

Beds of ‘Choro’ mussel Choromytilus chorus

Colombia is the only South American country with coastlines on both the Pacific Ocean and Caribbean Sea.  Two oyster species Saccostrea prismatica (=Ostrea iridecens) and Crassostrea colombiensis (=C. corteziensis) and the mud mussel Mytella guyanensis occur on the Pacific coast but are not of high socio-economic importance.

On the Caribbean coast, mangrove oysters Crassostrea rhizophorae, have been important for fisheries production but have been affected by alterations in river flow.  The population in the largest coastal lagoon Cienaga Grande de Santa Marta (CGSM) had nearly vanished by 1996, although recent monitoring data suggests that a remnant population exists.  Full recovery of this population is hindered by unauthorized harvest and although C. rhizophorae is included on Colombia’s Red List of threatened species there are no near-term management plans for conservation.  Ideally, future management plans should include restoration of oyster beds combined with development of aquaculture to reduce pressure on remaining wild stocks.

Suspended culture of mangrove oysters

Peruvian marine ecosystem are strongly influenced by the Humboldt Current, which extends from central Chile (~40ºS) to northern Perú (~4-5ºS), where a transition zone between the Peruvian and Panamic biogeographic province is located. The Humboldt Current exhibits high interannual variability from large oceanographic processes (ENSO), which in turn affects biological communities on the Peruvian coast.

Warm El Niňo events can both positively (e.g., the scallop Argopecten purpuratus) or negatively (e.g., the mussel Aulacomya atra) affect shallow subtidal bivalve populations. Both species are heavily exploited, particularly A. atra.  In the transition zone located between 3°24’ and 6° S, the oyster Ostrea iridescens and the mangrove clam Anadara
spp. sustain small-scale, unregulated fisheries. The fishery of Ostrea is expanding but is still poorly managed due to limited biological information and limitations in management budgets. Other exploited species include the razor clam Ensis macha and the yellow clam Mesodesma donacium, which is affected by the combined effects of overexploitation and range shifts associated with ENSO events. In addition, the mussels Choromitilus chorus and Mytella guayanensis, and the clams Chione subrugosa Prothothaca thaca, Semele spp., Gary solida, Donax spp. Glycimeris ovata and Tagelus dombeii, are targeted by small-scale artisanal fisheries.

Conservation efforts directed to commercially important bivalves are recent, and mainly
focused on A. purpuratus. There are some ongoing restoration and aquaculture efforts in
the north of the country, however. Similarly, there are artisanal fishermen communities (in Arequipa, Moquegua and Tacna) involved in restoration of the Bellow clam M. donacium, and experimental suspended culture techniques for A. atra are being developed by Instituto del Mar del Peru and the Spanish Cooperation Agency. There are 4500 ha of protected mangroves (National Mangrove Sanctuary) where there are community-based efforts targeting the sustainable exploitation of Anadara spp, based on traditional ecological knowledge.

Priority actions for the conservation of peruvian shellfish include: (1) increasing stakeholder involvement in the management of sustainable populations of shellfish (2)
strengthening the organization of fishermen associations to establish measures of
participatory management, (3) for oysters, research to help establish rules for seasonal closures and legal sizes based on reproductive activity, (4) for Mesodesma donacium, investigate recruitment processes for increasing sustainability, and (5) for Aulacomya ater, Ensis macha, Transennella pannosa and Anadara spp., implementation of pilot-scale restoration initiatives.

Related links:

Choro in a local market

Uruguay is located in a South Atlantic transition zone between temperate and subantarctic biotas. The Uruguayan shelf lies within the Uruguay-Buenos Aires shelf eco-region, which has been recognized as one of the highest ranked ecoregion of conservation importance in Latin America and the Caribbean. The western region is characterized by the invasive mussel Limnoperna fortunei. Brachidontes darwinianus and Mytella charruana overlap with Brachidontes rodriguezii from the eastern half of the central region and being replaced by this species in the eastern region. Mytilus edulis, in turn, is distributed from the eastern half of the central region, being the dominant mussel species in this zone. The commercially exploited mussel beds located at Isla Gorriti and Isla de Lobos are structured by M. edulis platensis, B. rodriguezi and B. darwinianus in decreasing order of abundance. Recent populations of the brown mussel Perna perna are distributed along the Atlantic coast of South America from Rio de la Plata, to Recife, Brazil, where they present a large gap north to the Caribbean shores of Venezuela. In contrast to other temperate systems, oysters does not display a significant ecological role.

The condition of native mussel beds, overall, is thought to be fair.  Despite the lack of quantitative information, and with the exception of the commercially exploited beds of M. edulis, there is no evidence supporting significant declines of mussel beds in Uruguay.  However, there are severe gaps in the biological knowledge needed for the sustainable management of wild fisheries, and critical deficiencies in monitoring and management capabilities.

The main recommendations for sustainable use and long-term conservation of Uruguayan mussel beds are 1) adoption of an ecosystem level approach for fisheries management; 2) implementation of conservation measures directed to preserve "pristine" beds; and 3) development of experimental co-management practices, in particular for small-scale benthic shellfisheries, to link economic issues for artisanal fishermen and conservation.

Related links:

Harvesting brown mussels Perna perna in Punta del Diablo, Uruguay

The coast of Venezuela contains a high diversity of coastal ecosystems including rocky shores, sandy beaches, mangroves, coral reefs and mussel and seagrass beds, leading to a diversity of mollusc populations. This diversity, coupled with high primary production, supports important bivalve beds, including oysters, mussels, pearly oysters and clams. In Venezuela there are four native oyster species, including two that form beds and are of commercial importance: Crassostrea rhizophorae and C. virginica. The main beds of C. rhizophorae are located in mangrove lagoons, and C. virginica occurs in Caños de Guariquén (Sucre State) and in the mouth of Maracaibo lake (Zulia State). Extraction of both species has declined since 1998 and currently only the La Restinga population can be considered as healthy, the rest are degraded or depleted due to overexploitation.

The brown mussel Perna perna and the exotic green mussel Perna viridis are commercially exploited. Some research suggests that P. viridis is displacing P. perna. Mussel extraction is also declining, from 360 to 200-250 tons since 2000. There are some government initiatives promoting aquaculture, and some coastal communities are involved in small scale production.

In order to improve the conservation status of oyster beds in Venezuela, there are proposals to restore beds in the Mochima National Park, using a community-based approach. Additionally, it will be necessary to improve conservation measures for beds in good shape (e.g. La Restinga lagoon, Margarita Island). The native brown mussel P. perna is in urgent need of conservation attention with a focus on improving fishery management approaches to restore the depleted beds.

Mangrove oysters in Rhizophora mangle roots

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