Longline Culture Research Articles

The current situation and environmental conditions of green mussel farming in the gulf of Thailand

This study investigated the current situation and environmental conditions of green mussel Perna viridis farming in Surat Thani, Phetchaburi and Samut Prakan provinces where were located in the gulf of Thailand. Samples were collected during April, August and November in 2014. Based on the results of this study, there were three major types of mussel culture patterns in Thailand: bouchot culture, longline culture (rope culture), and raft culture. Mussel farmers encountered problems on decreasing of larvae mussel in the water column, water quality degradation, high production cost and farmer’s lack of negotiation power to control the price. The water quality of the mussel farms, such as dissolved oxygen (DO), pH, salinity, electrical conductivity (EC), fecal coliforms bacteria and the total coliforms bacteria met the standard for aquaculture. However, the nutrient, such as ammonium (NH4-N), nitri-nitrogen (NO2-N), nitrate-nitrogen (NO3-N) and soluble reactive phosphorus (PO4-P) were higher than the value of marine aquaculture standard. The results of the contamination of Salmonella spp. bacteria were not found in the mussel’s tissue, however Escherichia coli was found at very low level.

Ciclo reproductivo de la ascidia Pyura chilensis (Urochordata: Ascidiacea) procedente de líneas de cultivo de mitílidos

The solitary sea squirt Pyura chilensis , is considered a resource of economic importance in the artisanal fisheries sector. This organism has a great capability to colonize artificial substrates, taking part in the encrusting fauna in long-line culture systems of ostreid and mussel, affecting the growth efficiency of these resources. For this reason, is necessary to know biological - reproductive aspects of P. chilensis in order to generate new information for future implementation of management plan, conservation and cultivation of this resource in the Region de Los Lagos, Chile. The purpose of this study was to investigate the reproductive cycle and settlement patterns of P. chilensis, analyzing the condition index and gonadal histology of organisms which come from a mussel farming system in Estero Huito, Calbuco (41°43’S;73°09’W) during 12 months. In addition, the settlement substrate preference of P. chilensis larvae was examined, using two artificial surfaces. The condition index (wet mass-siphonal distance) showed an increase between June and September, coinciding with low temperatures period and the spawning season (organisms in stage IV). However, recruit presence between November and June shows possible spawning events in other seasons. It was observed between 40 and 100% to gonadal stages II and/or III in the sampled organisms during the study period, which suggest a continuous gametogenesis. In addition, the larval settlement was higher in rough-dark substrate ( raschel mesh) than in plastic surface. In conclusion, the study area may be recruiting throughout the year, but at different intensity levels. This information would allow planning the collectors location to attract the seasquirts recruits, generating a continuous production of P. chilensis and decreasing the infestation in others crops.

Growth and economic performance of diploid and triploid Pacific oysters Crassostrea gigas cultivated in three lagoons of the Gulf of California

Diploid and triploid Crassostrea gigas oysters were cultured at three farms (Guasave, Navolato and Ahome) in Sinaloa, Mexico, to evaluate their growth and economic performances. Growth rate and survival of oysters were compared in long-line culture and were mostly affected ( P < 0.05) by water parameters rather than ploidy or their interaction. The highest growth rates for shell length (8.01 mm month -1 ) and body weight (9.08 g month -1 ) were obtained for the Ahome/triploid group. Survival differed significantly from 98.6% for the Guasave/triploids to 76.69% for the Ahome/diploids. After the first production cycle, more than 80% of production costs represent the purchase of culture equipment and salaries contributed with around 9%. The Guasave farm produced the highest profits ($8,053.71 USD diploids, $8,182.19 USD triploids). Use of diploids starting the production cycle on October-November to avoid mortality and improve final profit is recommended. Normal 0 21 false false false ES-MX X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Tabla normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:Calibri,sans-serif; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-fareast-language:EN-US;}

수하식 패류 양식장이 저서동물군집에 미치는 영향

수하식 패류 양식장이 저서동물군집에 미치는 영향

Potential environmental drivers of a regional blue mussel mass mortality event (winter of 2014, Breton Sound, France)

In the context of global change, increasing mariculture production has raised particular concerns regarding its environmental impact and sustainability. Molluscs and particularly blue mussel account for a significant part of this total production. Although blue mussels are considered to be pretty resilient to environmental disturbances, we report in this study an unprecedented mussel mortality event that occurred during the winter of 2014 in the Breton Sound. 9000metrictonnes of mussels were lost and mortality rates up to 100% were recorded at some farming areas. Through a coupling approach, the present work aims to better understand the potential environmental drivers associated with those mortalities. Firstly, we analysed long-term in situ and satellite data from environmental monitoring networks (available since 1998) to characterize the variability of seawater masses of the sound during the winter of 2014. Secondly, we used modelling simulations to study the possible relationship between seawater hydrodynamics and observed spatio-temporal patterns of mussel mortalities. From January to April 2014 at the long-line culture site where mortalities started, seawater temperatures ranged from 8.3 to 13.3°C (10.2±0.8°C). Salinity and turbidity values showed successive and short drops (below 16; 29.3±2.3) and numerous peaks (above 70 NTU; 17.4±13.4 NTU) respectively. Winter conditions of 2014 were encountered along the entire French Atlantic coastline and linked to the sixth highest positive North Atlantic Oscillation (NAO+) index recorded since 1865. These particular environmental variations characterized the winter of 2014 but also others whereas no comparable mussel mortality rates were reported. Exact causes of the 2014 mortality event are still unknown but we showed these environmental variations could not alone be responsible. These have likely affected the sensitivity of the blue mussel populations that were already weakened by early spawning. Meanwhile, these may have facilitated the apparition of a pathogenic strain of Vibrio splendidus isolated on moribund mussels at that time. Our modelling simulations suggested that this pathogenic strain could spread through hydrodynamic patterns and drive the observed mussel mortalities. If this pathogenic strain recurs in future years, particularly with the added stress associated with climate change, mussel mass mortality events may exceed the resilience of this species.

Stress analysis of a submersible longline culture system through dynamic simulation

This study analyzed the stresses on a submersible longline culture system subjected to both parallel and perpendicular oceanographic conditions of 0.5 and 1 m s-1 current velocity with 2 to 5 m wave height, using a dynamic simulation model based on the finite element method. Results indicated that when the culture system is submerged, the stress on mooring lines, the main line and whip lines decreases until a 55%. Additionally, changing the direction of the current and waves results in differences ranging from -59% to 312%. It was established that in an environment involving high-energy events, it is structurally possible to submerge the longline culture system in a direction parallel to oceanographic parameters, which could have positive implications for reducing the loss of cultivated biomass and improving productive conditions.

Perkinsus beihaiensis infectando a ostra Crassostrea rhizophorae em cultivo e em estoque natural na Baía de Camamu, Bahia, Brasil

Foi investigada a infecção de Perkinsus beihaiensis (Perkinsozoa) na ostra Crassostrea rhizophorae em um sistema de cultivo do tipo espinhel e em um estoque natural de ostras no manguezal adjacente ambos localizados no estado da Bahia, Nordeste do Brasil. As colheitas foram realizadas em outubro e novembro de 2012 e em janeiro de 2013. As ostras (n = 300) foram medidas, examinadas macroscopicamente quanto a sinais da infecção e submetidas às técnicas laboratoriais: histologia, ensaio em meio de cultivo de tioglicolato de Ray (RFTM), reação em cadeia da polimerase (PCR) e sequenciamento, que confirmou a identificação do patógeno. As análises histológicas e o RFTM mostraram, respectivamente, prevalência média de 93,3% e de 69%. A infecção foi geralmente leve ou muito leve. Não houve diferença significativa (p &gt; 0,05) entre os ambientes em termos de prevalência ou severidade da infecção. Este é o primeiro registro de P. beihaiensis no estado da Bahia e o segundo em ostras do Brasil e América do Sul.

Paleo-ecological analyses to assess long-term environmental effects of pearl farming in Western Australia

Small environmental disturbances accumulating over a long period of time may cause a regime shift in marine ecosystems, particularly in sensitive oligotrophic waters. Pearl oyster aquaculture, which has a 50 yr history in Australia, has been regarded as an anthropogenic activity with low environmental risk. To assess the long-term environmental effects of pearl oyster farming, sediment cores taken in Cygnet Bay, Western Australia, were used to reconstruct environmental processes covering an approximately 90 yr period. Biogeochemical parameters in sediment cores from inside and outside a pearl farming area displayed contrasting characteristics over time. Total organic carbon, total nitrogen, biogenic silica (BSi), and fine-grained sediment at the farming site displayed significant increases with the expansion of oyster stocking. In contrast, only small variations in response to climatic signals (rainfall and temperature) occurred over time in the cores outside the farm. The variation in the C:N ratio, delta C-13 and delta N-15 ranges over time suggested that increased organic matter was mainly contributed by autochthonous sources rather than terrestrial input. The sequential t-test for a regime shift detected approximately 2-to 3-fold increases in organic matter, 1-to 5-fold increases in silt proportion and 2-to 5-fold increases in BSi concentrations after pearl oyster farming, in contrast to the control site. The rapid development of modern long-line culture since the late 1980s is presumed to have been the dominant driver of environmental changes in sediments. The results provide insight into the magnitude of environmental change which can occur over decades as a result of even minimal anthropogenic activity.

Growth and reproduction of early grow-out hardened juvenile Pacific oysters, Crassostrea gigas in Gamakman Bay, off the south coast of Korea

The southern coast of Korea comprises many small bays where the Pacific oyster, Crassostrea gigas, has been cultivated intensively employing a long-line hanging culture system. Naturally harvested oyster spats used in the long-line culture system are hardened in mid-intertidal area and transplanted to the center of the bay for grow-out usually in May. The May transferred oyster produced considerably smaller quantity of eggs during spawning in September. To enhance the reproductive effort and growth during grow-out, we transferred the hardened oyster juveniles to grow-out sites in January rather than May to allow them to accumulate energy reserves at the time of spring phytoplankton bloom that normally occurs during April and early May. The January transferred oyster juvenile (JTO) showed fast somatic and shell growth during grow-out, reaching a marketable size in August, while the juvenile oyster transplanted in May (MTO) did not reach a market size until November. JTO spawned from June to September, with a single spawning pulse in July, while most of the MTO spawned in September. Quantity of eggs produced by the JTO was 5.7 times higher than MTO, indicating that early grow-out enhanced egg production. The meat weight and levels of tissue carbohydrate and protein of JTO harvested in November were significantly higher than MTO harvested at the same time, suggesting that the meat quality of JTO is superior to the MTO. Overall, our results suggest that transplanted hardened juveniles to grow-out in January increase natural oyster seed harvest in the bay as well as improve quality of the oyster for marketing. Statement of relevanceOyster farming is one of the leading aquaculture industries in the world, producing over 4 million tons of oysters annually world-wide. In the oyster industry, Crassostrea gigas, the Pacific oyster, has been cultured extensively in Asia, and recently in Europe using different modes of culture. In Asia, the Pacific oysters are raised using subtidal hanging long-line system, while they are cultured in intertidal areas using net bags and rack system in Europe.In Korea and Japan, the oyster seeds are supplied mostly from wild, by harvesting oyster larvae during post-spawning season. The newly harvested oyster spats are stunted in intertidal before they are transplanted to the subtidal hanging long-lines, to maximize survival of the seed oysters. This stunting process is called hardening and the hardening of oyster has been practiced for several decades in Korea and Japan. In Korea, the hardening seed oysters are transplanted in May, and the May transplanted oysters are harvested in December as they grow up to 8cm in shell length. The May transplanted oysters produce relatively smaller quantity of eggs during their first spawning, although the small reproductive effort may increase their survival during post-spawning season. The natural oyster spats harvested in late summer or early fall for the oyster culture in Korea are mostly originated from the May transplanted oysters. Currently, the natural oyster spat harvest in Korea suffers from insufficient quantity. In part, this insufficiency is associated to the poor reproductive activity of the May transplanted oyster.Low reproductive effort of May transplanted oysters during their first spawning is, in part, associated to too late transplantation to the bay, and earlier transplantation of the stunted oysters from the hardening ground to the grow-out ground in the bay may enhance the reproductive effort, resulting in subsequent successful larval recruitment and settlement of the larvae. Accordingly, we experimentally transplanted the hardened oysters 4months earlier to the traditional transplanting period (January) and monitored their reproduction and growth. Although the hardening process has been practiced over 50years, no studies have compared growth and reproduction of differentially transplanted oysters in Korea. As the data demonstrated, January transplanted oyster demonstrated earlier gonad maturation and produced 5× more eggs during spawning, compared to May transplanted oysters. No severe mortality was observed from the early transplanted oysters during the course of study, although reproductive activity of January transplanted oysters was relatively intensive, compared to May transplanted oysters.The present study first attempted to evaluate effectiveness of transplantation timing of the hardened oysters, in terms of growth and reproduction. Also, quantity of the eggs produced from differentially transplanted female oysters was first measured and compared in this study using ELISA. As the data indicated, January transplanted oyster produced 5× more eggs, which may enhance the natural oyster spat harvest in the bay, as well as to evaluate the transplantation period and management of oyster farming on the south coast of Korea.

Tropical seaweeds for human food, their cultivation and its effect on biodiversity enrichment

article i nfo As a response to growing land and freshwater shortages and climate change, the use of seaweeds as food, their cultivation at sea and its effect on biodiversity are being researched on both the Caribbean and Pacifi cc oasts of Costa Rica. Native species, more plentiful on the Caribbean coast, were collected and pre-selected based on existing information and on criteria including ubiquity, abundance, growth and palatability. These species were then evaluated as food and subjected to floating long-line cultivation using vegetative propagules. After establishing postharvestprocedures, useasfood involvedmanypreparationstobe eatenfresh orafterdrying,in- cluding a dry-ground meal. Ten of these species, which had nutrient contents within expected values including 9.8% crude protein on a dry weight (dw) basis and high iron, were considered adequate as food, both directly and as part of recipes in quantities not exceeding 20% dw of a given dish. Higher concentrations either 'overwhelmed' traditional recipes or their taste was rejected by tested consumers. Near-coast cultivation was in general a simple matter, easily transferred to artisanal fishers. To a great extent due to herbivory and theft of ropes, yield (ranging from 51.7 to 153.2 t ha −1 yr −1 on a fresh weight basis) was quantified for only five spe- cies with a mean of 9.3 t ha −1 yr −1 dw, equivalent to 0.91 t ha −1 yr

Climate Change Influences Carrying Capacity in a Coastal Embayment Dedicated to Shellfish Aquaculture

A spatially explicit coupled hydrodynamic-biogeochemical model was developed to study a coastal ecosystem under the combined effects of mussel aquaculture, nutrient loading and climate change. The model was applied to St Peter’s Bay (SPB), Prince Edward Island, Eastern Canada. Approximately 40 % of the SPB area is dedicated to mussel (Mytilus edulis) longline culture. Results indicate that the two main food sources for mussels, phytoplankton and organic detritus, are most depleted in the central part of the embayment. Results also suggest that the system is near its ultimate capacity, a state where the energy cycle is restricted to nitrogen-phytoplankton-detritus-mussels with few resources left to be transferred to higher trophic levels. Annually, mussel meat harvesting extracts nitrogen (N) resources equivalent to 42 % of river inputs or 46.5 % of the net phytoplankton primary production. Under such extractive pressure, the phytoplankton biomass is being curtailed to 1980’s levels when aquaculture was not yet developed and N loading was half the present level. Current mussel stocks also decrease bay-scale sedimentation rates by 14 %. Finally, a climate change scenario (year 2050) predicted a 30 % increase in mussel production, largely driven by more efficient utilization of the phytoplankton spring bloom. However, the predicted elevated summer temperatures (>25 °C) may also have deleterious physiological effects on mussels and possibly increase summer mortality levels. In conclusion, cultivated bivalves may play an important role in remediating the negative impacts of land-derived nutrient loading. Climate change may lead to increases in production and ecological carrying capacity as long as the cultivated species can tolerate warmer summer conditions.

Life cycle assessment of macroalgae cultivation and processing for biofuel production

There has been a recent resurgence in research investigating bioenergy production from algal biomass due to the potential environmental benefits in comparison to conventional bioenergy crops and conventional fossil fuels. This life cycle assessment (LCA) considered the energy return and environmental impacts of the cultivation and processing of macroalgae (seaweed) to bioethanol and biogas with a particular focus on specific species (Gracilaria chilensis and Macrocystis pyrifera) and cultivation methods (bottom planting and long-line cultivation). The study was based mainly upon data obtained from research conducted in Chile but the results can be applied to other locations where similar cultivation is feasible. Speculative data were also included to test promising data obtained from research. The results suggested that using base case conditions the production of both bioethanol and biogas from bottom planted Gracilaria chilensis was the most sustainable option due to the low input method of cultivation. Using new advances in cultivation and processing methods of long-line cultivated Macrocystis pyrifera however resulted in a much more sustainable source of bioenergy. If these methods can be proven on a large scale, the generation of bioenergy from macroalgae could be highly competitive in terms of its sustainability compared to alternative feedstocks. Future research should bear in mind that the results of this study should however be considered highly optimistic given the early stage of research.

Modelling of interactions between inshore and offshore aquaculture

Abstract Offshore aquaculture is the subject of intense debate, focusing on feasibility, sustainability, and the potential for effective expansion in the context of competing uses of the coastal zone, and a world requirement for an additional thirty million tonnes of aquatic products by 2050. A modelling framework that integrates the SWAT model for the watershed, Delft3D for ocean circulation, and the EcoWin model for long-term (10 year) ecological simulations, was developed for integrated analysis of catchment, inshore waters, and offshore aquaculture, providing an approach that addresses production, environmental effects, and disease interactions. This framework was tested using a case study in SE Portugal, for a system-scale modelling domain with an ocean area of 470 km2 and a coastal watershed area of 627 km2. This domain contains an inshore area of 184 km2 (Ria Formosa) subject to multiple (often conflicting) uses, including aquaculture of the high value (farmgate price > 10 € kg− 1) clam Tapes decussatus, and one of the first offshore aquaculture parks in the world, located at distance of 3.6 nm from the coast, at a water depth of 30–60 m, with an area of 15 km2. The park contains 60 leases, of which at most 70% are for finfish cage culture, and at least 30% for bivalve longline culture. A substantial part of the dissolved nutrients required to drive primary production that constitutes the food source for clams originates from the coastal catchment. Although stakeholder perception is that nutrients are mainly linked to point-source discharges from wastewater treatment plants, watershed modelling indicates that 55% of the nitrogen and 70% of the phosphorus loads are from diffuse sources. The residence time of waters in the inshore area is low (1–2 days), and consequently pelagic primary production takes place offshore, and drives inshore clam production. The longline culture of Mediterranean mussels (Mytilus galloprovincialis) in the offshore park reduces inshore food availability for clams: simulations suggest that a 3% decrease in clam yields will occur due to offshore mussel cultivation, at a cost of 1.2 million €. This is offset by revenue from offshore culture, but is a source of stakeholder conflict. Potential disease spread between the offshore and inshore systems was analysed using a particle tracking model, and allowed the development of a risk exposure map. This illustrates the challenges posed by hydrodynamic connectivity with respect to biosecurity of aquaculture and fisheries, both inshore and offshore. The model framework was also used for optimisation of stocking density, and analysis of combined culture of finfish and shellfish, both in terms of production and environmental effects. In the offshore aquaculture park, the models suggest that integrated multi-trophic aquaculture (IMTA) of gilthead bream (Sparus aurata) and Mediterranean mussels allows for an increased harvestable biomass of mussels, particularly at higher stocking densities, and offsets some of the negative externalities of finfish culture. By quantifying issues such as reduced yields for inshore stakeholders due to offshore activity, and illustrating the need for strong governance to offset disease risks, dynamic models make a valuable contribution in assessing the feasibility of offshore aquaculture, and the general principles that should underpin licensing and regulation of this sector. We stress the need to go beyond the conventional spatial planning toolset in order to ensure an ecosystem approach to aquaculture, and the opportunities that exist for applying a systems framework in an information economy, where the capital costs of software and data have been sharply reduced.

Commercially-cultured oysters (Crassostrea gigas) exert top-down control on intertidal pelagic resources in Willapa Bay, Washington, USA

The capacity of filter feeders to reduce seston and phytoplankton concentrations in the water column has important implications for restoration and management of coastal ecosystems. We directly measured changes in chlorophyll a concentration on commercially stocked intertidal oyster beds (Crassostrea gigas) in Willapa Bay, Washington, USA by recording water properties near small drifters as they tracked parcels of water across tide flats. Chlorophyll declined 9.6% per half hour in water passing on-bottom adult oysters and 41% for longline adult oysters, whereas chlorophyll concentrations increased as water flowed across tide flats without adult oysters. Field filtration rates, which were fit to exponential declines in chlorophyll and accounted for oyster density and water depth, averaged 0.35Lg−1h−1 (shucked dry weight) for on-bottom aquaculture and 0.73Lg−1h−1 for longline culture, compared to values of 2.5–12Lg−1h−1 reported from laboratory studies of C. gigas. Field filtration rates may be lower than laboratory rates due to unfavorable field conditions (e.g., low initial chlorophyll concentrations) or masked by resuspension of benthic microalgae. In addition to distinctions among on-bottom, longline, and no-oyster habitats, Akaike's Information Criterion analysis showed temperature, initial chlorophyll concentration, and depth related to chlorophyll decline. This research corroborates mathematical models suggesting that benthic suspension feeders are exerting top-down control of pelagic production in this estuary, with strong patterns in chlorophyll emerging across extensive tideflats populated by C. gigas despite low field filtration rates.

亚热带养殖海湾皱瘤海鞘生物沉积的现场研究

A worldwide increase in farming of filter feeding bivalves and a growing awareness of the likely environmental impacts stem from biodeposition lead to extensive and well recognized studies.Whereas the suspended longline culture with massive and intensive facilities built(e.g.,buoys,anchors and ropes) and bivalve shells in the farming area supply the footstone for the fouling organisms such as the ascidians and large number of breeding depended on them,which can be extremely abundant in areas of large-scale bivalve culture.Therefore,the fouling organisms may also influence the environment by remarkably increasing their amounts.There is an urgent need to examine the possible effects of biodeposition from the fouling organisms.The ascidian Styela plicata is one of the most predominant fouling species in tropical and subtropical bays.S.plicata is a filter feeding species like the bivalves.However,untill recently,the biodeposition of S.plicata was unknown.In order to evaluate the influence of S.plicata on the coastal environment,the biodeposition rate of ascidian S.plicata was investigated in Dapeng Cove,located in the southwest of the Daya Bay,a subtropical bay in southern China.Intensive oyster Crassostrea gigas longline culture activities were conducted there.The ascidians were sampled from the culture facilities and shells of the oyster Crassostrea gigas.The biodeposition rate was measured in situ in suspended culture areas by sediment traps from January to July,2012.The contents of organic matters(OM),total carbon(TC),total nitrogen(TN),organic carbon(OC) and organic nitrogen(ON) in biodeposits and in natural sediments were analyzed and compared. Results showed that the biodeposition rate of S.plicata ranged from 145.5 to 1011.8 mg·ind-1·d-1,with an average of 516.0 mg·ind-1·d-1.The mean contents of OM,TC,OC,TN and ON in the biodeposits was 14.38%,10.80%,2.87%,3.06% and 0.86%,respectively,and were higher than those of 13.39%,7.36%,2.32%,2.29% and 0.67% respectively,in natural sediments.In particular,the contents of TC and ON in the biodeposits were significantly higher than those in the natural sediments(P0.05).The biodeposition rate of OM,TC,OC,TN and ON by S.plicata were 74.20,55.73,14.80,15.79 and 4.43 mg·ind-1·d-1,respectively.The density of S.plicata in the longline culture area ranged from 54.9 to 222.1 ind/m2,with an average of 147.5 ind/m2.The OM,TC,OC,TN and ON deposited by S.plicata was 10.94,8.21,2.18,2.32 and 0.65 g·m-2·d-1,respectively.The average biodeposition rate of ascidian S.plicata in the farming area was 76.1 g·m-2·d-1,1.21 times higher than the natural sedimentation rate(62.7 g·m-2·d-1) in the longline culture area.An estimated amount of 29000 t of biodeposits,4100 t of OM,3100 t of TC,820t of OC,870 t of TN and 240 t of ON can be produced by all the ascidians in suspend culture area in Dapeng Cove in one year. The results indicated that S.plicata has a high biodeposition rate and the species can be an important contributor to aggregating mineral and organic matter from water column to surface sediment,which may impact the physical,chemical and biological conditions of benthic environment.Therefore,when assessing the effects of suspended longline culture of bivalves on the coastal ecosystem,not only the farming bivalves,but also the fouling organisms especially the ascidians should be considered.

Growth and Condition of the Pacific OysterCrassostrea gigasat Three Environmentally Distinct South African Oyster Farms

The Pacific oyster Crassostrea gigas is cultured at 8 commercial farms in South Africa. Worldwide, environmental-specific intensive selection on the species optimizes commercially beneficial traits, but its performance has not been studied in South Africa. From May 2010 to March 2011, we compared 2-mo measurements of growth rate, condition, and survival of 3 cohorts of different origin in longline culture at 3 different South African environments: 2 sea-based farms located in Saldanha Bay (Western Cape) and Algoa Bay (Eastern Cape) and a land-based farm at Kleinzee (Northern Cape). Overall, Saldanha Bay was cooler (mean sea surface temperature of 16.0°C; CV, 16.2%) than the other 2 localities, which did not differ significantly from one another (Kleinzee: 18.6°C; CV, 20.4%; Algoa Bay: 17.8°C; CV, 8.9%). The high variability at Kleinzee reflected stronger summer warming than at the other 2 farms. Saldanha Bay had higher phytoplankton biomass (mean, 14.3 mg chlorophyll a/m3; CV, 54.2%; May 2010 to March 2011) than did Algoa Bay (mean, 5.3 mg chlorophyll a/m3; CV, 81.0%; September 2010 to March 2011). The 3 cohorts showed similar trends in growth and condition. Growth rates, expressed as live or dry mass gains, were 2–10 times those reported elsewhere in the world, and dry weight condition indices were also high. High live mass growth rates in Algoa Bay, despite its relatively low phytoplankton biomass, seem to reflect a similar phenomenon to that reported in other relatively phytoplankton-poor grow-out environments, such as the Mediterranean Thau Lagoon in France. Dry meat mass gain and condition were highest for oysters in Saldanha Bay, with high food availability offsetting the thermal advantages of the warmer Algoa Bay site. Oysters in the bottom layers of the cages grew significantly faster than those in the top layers, particularly in Saldanha Bay, possibly reflecting fine-scale vertical differences in phytoplankton biomass. Saldanha Bay is the best of the 3 locations to produce market-ready oysters. Algoa Bay yields faster growth but leaner oysters and is a good nursery location, as is Kleinzee, which yields overall slow growth but good shell quality in winter and early spring.

Analysis of water quality of abalone suspended long-line mariculture area of Sungo Bay

Abalone long-line culture is a commercially important mariculture method in China.With the development of scale,it is very important and necessary to understand its influence on the environment.In this paper the effects of abalone long-line culture on the water quality were studied,in order to provide basic information for the setup of sustainable mariculture mode.Dissolved nutrients were investigated in abalone long-line mariculture area of Sungo Bay in April,June,August,October and December of 2009.Water quality was assessed by organic pollution indices(A) and eutrophication assessment indices(E).Nutrient factors limiting the growth of phytoplankton were assessed by the method of theoretical half-saturation constant(Ks)and stoichiometric ratios.By comparison of nutrients in abalone,kelp and no mariculture areas and the historic data,the environmental influence of abalone long-line mariculture was analyzed.Results showed that the concentration of dissolved inorganic nitrogen(DIN),PO3-4,and SiO2-3 were at the range of 2.73-9.25 μmol/L,0.086-0.42 μmol/L,0.91-18.35 μmol/L,respectively.In April,June and December,A values were lower than 0,water conditions were in good level,in August and October,A values ranged between 0 and 1,water conditions were at preferable level.E values ranged in 0-0.5,which showed that the nutrient concentration was in the poor nutrient condition.This result suggested that the influence of abalone long-line culture on the water quality was limited.However,there were some extent variations between different areas in the nutrients concentration,nutrients structure and seasonal changing trend.P might be the key limitation in the monitoring area.From the historic changing trend,ammonium and DIN enrichment in abalone area in August should be paid more attention to.

Modelo dinámico de crecimiento de la biomasa para Mytilus chilensis en sistemas de cultivo en líneas

A dynamic biomass growth model for the mussel Mytilus chilensis in longline culture systems in proposed. This model determines the biomass by estimating the ...

A REVIEW OF PEARL OYSTER (Pinctada maxima) CULTUREIN GENERAL

ABSTRACT Pearl oyster culture is unique because the product is gem not flesh and one of the species that produce pearl is Pinctada maxima (Silver or Gold lip pearl oyster). Stock for pearl oyster production can be collected from the wild or hatchery. However, hatchery production is a better solution to supply P.maxima for pearl production rather than just depend on wild stocks. Spat from the wild or hatchery will be grown-out for pearl production by longline or raft culture system method in ocean. Raft culture provide a work platform to repair, clean and store culture tools, while, longline culture has better design to deal with wave or wind exposure. There are identified different culture systems according different species (for example between P.maxima and P.fucata) and locations. Several constraints on P. maxima culture also identify such as biofouling organisms, predations and diseases that can reduce productivity and pearl quality. For example, mass mortalities of P.maxima occurred in Western Australia due to viral infection and it disrupted the pearl oyster industry. Therefore, several strategies are needed to mitigate those problems to achieve maximal productivity by using good management culture practice. Key word: pearl oyster, P. maxima, management, culture

Site selection for shellfish aquaculture by means of GIS and farm-scale models, with an emphasis on data-poor environments

An integrative methodology for site selection of shellfish aquaculture that combines geographical information systems and dynamic farm-scale carrying capacity modeling was developed. The methodology determines suitable aquaculture areas through 3 stages of analysis: (i) analysis of regulatory and social spatial restrictions using GIS to generate a constraints map; (ii) a Multi-Criteria Evaluation that considers the criteria (sediment, water and ecological quality data) and constituent factors (physical, growth and survival, product quality and environmental sensitivity) to generate a final map showing the most appropriate areas using GIS tools; and (iii) detailed analysis of production, socio-economic outputs and environmental effects of suitable areas using the FARM model. The methodology emphasizes the application in data-poor environments, where there are a combination of social difficulties, data scarcity, and aquaculture expansion pressure. The methodology was tested for Pacific oyster ( Crassostrea gigas) suspended longline culture in the Valdivia estuary (south central Chile), in order to explore the approach and make management recommendations for potential application. The identification of 3 km 2 (7.6%) of suitable sites in the study area using a GIS approach was made considering regulatory and social constraints; growth and survival factors, physical factors, product quality factors, environmental sensitivity zones, water, sediment and ecological quality criteria, factor suitability ranges, and a final Multi-Criteria Evaluation. The final assessment of production carrying capacity at four potentially suitable sites (Niebla, Valdivia, Isla del Rey and Tornagaleones) indicates that Tornagaleones is the most promising area for shellfish aquaculture and Valdivia is satisfactory; the Niebla and Isla del Rey sites are of marginal interest. Tornagaleones shows a total potential harvest of 139.6 t over a 395 day cultivation period for the test farm, and an average physical product of 11.64. Mass balance estimation was carried out to determine the potential positive impact of the suitable sites for nutrient credit trading. Biodeposition of organic material from the longline leases was also simulated, and found to have a low negative impact on sediment quality. Eutrophication assessment results indicate that positive impacts on water quality in Valdivia and Tornagaleones sites were obtained due to high phytoplankton removal. This methodology illustrates how GIS-based models may be used in conjunction with tools such as a farm-scale carrying capacity model to assist decision-makers in developing an ecosystem approach to aquaculture. The application of this approach provides an integrative methodology for site selection for shellfish aquaculture, despite limitations in the data available, taking into account production, socio-economic and environmental aspects.