Sea cucumber habitat differentiation and site retention as determined by intraspecific stable isotope variation

Stable carbon and nitrogen isotope ratios (δ¹³C/δ¹⁵N) were assessed as a means to ascertain the recent in situ feeding history of the common New Zealand sea cucumber Australostichopus mollis in relation to nutrient enrichment from a longline green‐lipped mussel (Perna canaliculus) farm in Northern New Zealand. δ¹³C and δ¹⁵N isotopic signatures and the ratios of sea cucumbers sampled from within the impact footprint of the mussel farm were compared with those of sea cucumbers residing on adjacent natural reefs. Sea cucumbers from beneath mussel farming longlines had significantly different δ¹³C stable isotope signatures in comparison with sea cucumbers collected from neighbouring natural reef habitats. This difference supports the hypothesis that sea cucumbers in the same bay maintain distinctly different feeding histories, with those residing beneath mussel farming longlines deriving tissue carbon from sediment impacted by farming activities. This hypothesis is further supported by the finding that the isotope signature of sediment collected from beneath the mussel farm is consistent with the expectation that sea cucumbers were feeding on and consuming sediment enriched with bivalve waste (faeces and pseudo‐faeces). In contrast, the nitrogen stable isotope signature (δ¹⁵N) was found to be similar between sites for both sea cucumbers and assumed food sources. Both findings lend support to the viability of future sea cucumber/green‐lipped mussel farm polyculture systems. Sea cucumbers in different locations (mussel farm, natural reef) possessed distinctly different isotope signatures, suggesting that mixing of sea ranched sea cucumbers with natural reef populations would be negligible or non‐existent. Similarities between the isotope signatures in low metabolic tissue of sea cucumbers residing at the mussel farm site to that of mussel farm‐impacted sediment suggest that cucumbers beneath mussel farms appear to have high rates of retention at the farm site.     

Feeding behaviour of green mussels,Perna viridis farmed in Marudu Bay,Malaysia

The green mussel, Perna viridis is known to have the ability to selectively ingest certain suspended particles from water. However, the preferential ingestion of specific phytoplankton taxa by P. viridis under different environmental conditions is not well understood. A study was undertaken to identify the phytoplankton taxa that are preferentially ingested and rejected by P. viridis in different environmental conditions at Marudu Bay, Malaysia. Phytoplankton abundance and composition in stomach and surrounding waters were determined microscopically. The gonad development stages of P. viridis and various environmental parameters of the bay including temperature, salinity, dissolved oxygen, current speed, pH, visibility, chlorophyll a, nutrients concentration and suspended particles were also determined. Results of current study demonstrated that selective ingestion in P. viridis was mainly influenced by seston concentration, phytoplankton abundance and composition. At high seston concentration with low phytoplankton abundance, P. viridis selectively ingested Coscinodiscus spp. In contrast, P. viridis was found to ingest wider range of phytoplankton at low seston concentration and high phytoplankton abundance. Interestingly, Chaetoceros spp. and Bacteriastrum spp. were selectively rejected by P. viridis in both high and low seston conditions. Nevertheless, no selective ingestion behaviour was evidenced in low seston with low phytoplankton conditions. Besides phytoplankton, zooplankton has also contributed significantly in the diet of P. viridis, where high numbers of copepod and bivalve larvae were found in the stomach. The findings of current study can be useful in determining potential farming sites for green mussel in future.     

国外贻贝养殖工程设施发展近况

近岸养殖渔业的发展受到环境污染的影响和养殖容量的限制,国外近年来积极推进离岸深海养殖技术.综述了国外贻贝离岸养殖模式及养成设施的文献资料,用图片形式介绍了几种养殖设施的设计理念和结构,其中包括平台吊养、浮筏吊养等上浮式养殖模式以及半潜筏式吊养、半潜管式吊养等新型养殖模式,并提出了离岸养殖需注意的一些实际问题.     

Growth variations within a farm of mussel (Mytilus galloprovincialis) held near fish cages: importance for the implementation of integrated aquaculture

Fish farming releases extensive amounts of particulate organic waste that can be exploited by bivalves in integrated culture. We tested if mussels Mytilus galloprovincialis cultured at two depths (1 and 6 m) in a raft, moored 170 m from a fish farm had greater growth than bivalves held 550 m from the fish cages. Mussel growth was monitored monthly, covering the second phase of the culture, from thinning‐out to harvest (March to November 2011). We also studied if fish solid and dissolved nutrients increased the organic content of the seston and chlorophyll‐a levels near the fish cages through weekly samples. Results showed no differences in seston, chlorophyll and physiochemical characteristics of the water among rafts. Maximum growth and Condition Index (CI) occurred during spring–summer (April–August), when mussels had access to greater food quality and quantity. Mussels cultivated close to the cages showed similar shell length, weight and CI compared with mussels distant from the fish farm. Average shell length, meat dry weight and CI at harvest were 76.31 mm, 2.51 g and 23%. Bivalves cultured distant from the fish cages displayed 26% higher biomass than the other raft at the end of the experiment. Differences in biomass were explained by the significantly higher recruitment of mussel seed observed at the raft distant from the fish cages from June to November. The lack of a significant enhancement in growth of the bivalves cultured next to finfish is discussed.     

褐菖鲉幼鱼对贻贝养殖生境的利用规律初探

嵊泗海域规模庞大的贻贝养殖生境发挥着养护幼鱼的海洋牧场功能,而探查当地趋礁鱼类在幼体阶段对该生境的利用规律可为当地海洋牧场的设计提供重要参考,为此2018年5—7月对舟山北部枸杞岛贻贝场的褐菖鲉幼鱼、附着生物进行了逐月调查,使用自制网具采集目标生物样品,应用相对密度指数和相关分析法分析了褐菖鲉幼鱼在该生境中的栖息密度、栖息方式和空间分布特征,采用胃含物分析法确定其食性特征,并结合耳石轮纹探究其利用该生境的生长周期。结果显示,褐菖鲉幼鱼的栖息密度时空特征上,5—7月在养殖区贻贝串上的栖息密度分别为(10±6)、(7±5)和(5±5)个/串,时间上呈现逐月递减趋势,随时间的推移养殖区外侧幼体逐渐迁移至内侧近岸区直至消失。栖息方式选择上,褐菖鲉幼鱼栖息数量与贻贝串孔隙大小和附着海藻生物量之间皆呈正相关,但并不显著。饵料利用上,养殖区褐菖鲉幼鱼总体维持较高的摄食强度,各月份平均摄食强度皆高于对照区,主要摄食对象为麦秆虫和钩虾,重量百分比为70.9%和28.3%。栖息周期上,养殖区内褐菖鲉幼鱼耳石平均轮纹数为(57±12)个,其利用养殖贻贝串的周期一般约为2～3月,且该生境中幼鱼耳石纹路间距均匀性和条纹清晰度均明显优于岩礁生境。研究表明,枸杞岛的贻贝养殖生境成为褐菖鲉幼鱼额外的栖息环境,在增殖养护褐菖鲉资源方面发挥了积极作用,因此嵊泗海域在建设海洋牧场时可依据贻贝养殖生境的资源养护原理,通过设置浮体结构强化海洋牧场的饵料场和庇护功能,以提高褐菖鲉种群的补充量,为当地休闲海钓的持续发展提供部分保障。     

EXTERNALITIES,INSTITUTIONS AND THE LOCATION CHOICES OF SHELLFISH PRODUCERS: THE CASE OF BLUE MUSSEL FARMING IN THE MONT-SAINT-MICHEL BAY (FRANCE)

ABSTRACT

Most marine aquaculture activities remain strongly dependent on coastal ecosystems. In the case of shellfish farming, this dependency is related mainly to water quality and to the various ecological interactions resulting from the dynamics of coastal food webs. Such ecological constraints have influenced the overall evolution of blue mussel farming in the Mont-Saint-Michel Bay, leading producers to negotiate collective arrangements regarding production capacity and techniques and to develop production strategies at the farm level. This article presents an analysis of the location choices of mussel farmers in the Mont-Saint-Michel Bay based on an empirical investigation conducted in 2002. A typology of farms with respect to their land structure is developed in which some farms choose to concentrate their activity in a single part of the bay while others distribute their activity more widely. Determinants of the location choices of each farm category, including distance to port, natural productivity differentials, and predation of mussel stocks, are analyzed. The role of the institutional arrangements allowing mussel farmers to develop these location strategies is also discussed.     

MODELING CARRYING CAPACITIES FOR BIVALVE MOLLUSCS IN OPEN,SUSPENDED-CULTURE SYSTEMS

Standard accounting procedures in ecological energetics would approach the carrying capacity problem by attempting to quantify gross energy needs of a cultivated population and comparing these with “available” energy (seston) flow through the culture area. Inability to distinguish between “available” and “utilizable” particles is only one of several difficulties encountered in formulating energy budgets for large-scale cultivation in natural waters, however. A model based on maintaining critical levels of particle flow through culture areas is offered as an alternative. This approach reduces the problem to terms which are easier to obtain than those involved in equations of energy flow. Application of the model depends on a priori knowledge that seasonal patterns in seston composition and other environmental conditions are conducive to growth of the cultivated species.     

Green Mussel,Perna viridis,Farming in Kerala,India – Technology Diffusion Process and Socioeconomic Impacts

The technology diffusion process of green mussel, Perna viridis, farming in Kerala, India, was studied by analyzing the adoption pattern, socioeconomic profile of mussel farmers, differences in farming methods, profit variations, development of trade and downstream industries, and the social factors responsible for the growth of this new industry. The farming practice has been adopted by villagers from 1996, and because of its rapid growth, India has risen to one among the top 10 farmed mussel producing nations in Asia, with an annual production of 10,060 tonnes, worth $US1.79 million at farm‐gate level. Three types of farm ownerships were observed: individual ownership (IND), family ownership (FAM), and ownerships by self‐help groups (SHG). The adoption curves are such that there were only a few adopters initially followed by an increasing rate of adoption in the subsequent years because of the demonstration effect. The study indicated the deep‐rooted “risk aversion” attitude widely prevalent among technology adopters. Age could not be significantly related to technology adoption, while education and occupation of the respondents significantly (P < 0.05) influenced the technology adoption process. The biggest outcome of mussel farming in Kerala was the empowerment of women with 87% of the SHG farms owned by women. The successful diffusion of mussel farming is the result of a combination of factors, chiefly, the availability of suitable water bodies; high rate of education; proximity of mussel markets and high degree of mussel consumption in the area; and a unique synergy between technology developers, promoters, and credit advancers. This development scenario can work as a role model for developing nations.     

Ecological footprint for assessment of resource use and development limitations in shrimp and tilapia aquaculture

We review estimates of the spatial ecosystem support required to run a typical semi-intensive shrimp farm in a coastal mangrove area in Carribean Colombia, and to produce food inputs and process wastes for large-scale industrially managed tilapia cage culture and small-scale, semi-intensive tilapia pond farming in Lake Kariba, Zimbabwe. The tilapia farming is discussed in relation to the pelagic kapenta, Limnothrissa miodon (Boulenger), fishery and to inshore fisheries in the Lake. The results show that a semi-intensive shrimp farm needs a spatial ecosystem support—the ecological footprint—35 to 190 times the surface area of the pond, mainly mangrove area. Based on the analysis, we conclude that shrimp farming in Colombia is already utilizing close to the full support capacity of its coastal environment. In intensive tilapia cage farming, the ecological footprint for feed production is 10 000 times larger than the area of the cages. In contrast, a tilapia pond farm maintained on offals from fisheries, agriculture and households depends very little on external ecosystem areas. As long as there is a direct market for human consumption of all kapenta caught in the Lake, fish cage farming based on fish meal from kapenta would be doubtful from ethical, ecological as well as resource management points of view, even if it was economically feasible.     

Commercial marine fish farming in Singapore

Commercial marine fish farming in Singapore is mainly the culture of economically important foodfish species in floating cage nets. There are 84 licensed fish farms occupying 46.5 hectares (ha) of coastal waters. Production from these farms accounts for the bulk of aquaculture production in Singapore, being 3554 tonnes (‘metric tons’, t) in 1995, or 98% of total production of 3625t. The commonly cultured species are the green mussels, Perna viridis L., which form the bulk of production (70.4%), finfish like the groupers, Epinephelus tauvina Forsskal and E. malabaricus Schneider, Asian sea bass, Lates cakarifer Bloch, and snappers, Lutjanus johni Bloch and L. argentimaculatus Forsskal, and crustaceans like the mangrove crab, Scylla serrata Forsskal and spiny lobster, Panilurus polyphagus Herbst. The basic farm structure for fish and mussel culture is the floating wooden raft. In finfish farming, polyethylene cage nets are attached to the raft in which popular foodfishes are cultured. The mussel raft is a structure to which polyethylene ropes are attached to collect and grow out green mussels from natural spatfall. Fish seeds for farming are mostly wild-caught. Only the Asian sea bass and the banana shrimp (Penaeus merguiensis de Mann) are produced by commercial hatcheries in Singapore and the region. The fry of pompano (Trachinotus blochii Lacepede, and T. falcatus Klausewitz & Nielsen) are imported from Taiwan. Trash fish is still the main feed used for the farming of finfish and crustaceans like the mangrove crab and lobster because it is cheap and readily available. This paper also reviews the economics of commercial finfish and mussel farming in Singapore today.     

Effects of fish farming on microbial planktonic communities in the middle Adriatic sea

The effects of farming on planktonic microbial communities were investigated at the coastal sea bass/sea bream farm in the oligotrophic middle Adriatic Sea. Analyses of nutrients, chlorophyll a, cyanobacteria (Prochlorococcus), heterotrophic bacteria and nanoflagellates (both pigmented and heterotrophic) were carried out on samples taken during six seasonal cruises at different water depths. Farming activity increased the natural concentrations of some nutrients (ammonium, nitrite, phosphate, dissolved inorganic nitrogen) and changed their seasonal pattern. The values still remained typical for oligotrophic environ‐ments demonstrating no risk for eutrophication. Enhanced nutrient supply provoked an immediate increase in abundances of both autotrophic and heterotrophic microbial groups (except pigmented nanoflagellates) and chlorophyll a. The effect of farming was more visible for the heterotrophic microbial component. Results from this study reveal a potential common pattern of microbial response to farming in the oligotrophic environments. It also suggests the importance of heterotrophic microbial web in transferring the matter and energy released from the fish farms in nutrient poor environments.     

枸杞岛贻贝养殖水域碳氮磷分布格局

于2013年贻贝成熟期和幼苗期对枸杞岛贻贝筏式养殖水域营养分布和碳分布格局开展相关实验。结果表明:从生态健康角度,夏季成熟期的贻贝养殖造成养殖海域氮、磷营养盐浓度升高,尤其是无机氮浓度显著高于非养殖区(P<0.05),养殖区处于受磷限制性的重富营养化,对其水体健康产生一定压力;秋季幼苗期贻贝养殖使养殖海域氮、磷浓度均降低,尤其是无机氮浓度显著低于非养殖区(P<0.05),与夏季分布格局相反,对水体有净化作用。从生态效应看,贻贝养殖使表层水体中溶解无机碳浓度显著低于非养殖区(P<0.05),产生碳汇效应;同时,贻贝养殖使水体中溶解有机碳浓度显著高于非养殖区(P<0.05),由于丰富的氮营养盐,溶解有机碳处于不稳定态,为碳源。因此,成熟期与幼苗期贻贝养殖对其水域健康产生不同作用,养殖的碳汇、碳源还有待进一步的系统研究。     

Hydrodynamic method for estimating production carrying capacity of coastal finfish cage aquaculture in Southeast Asia

This paper presents the development of a simple and generally applicable hydrodynamic method for the estimation of production carrying capacity (PCC) of coastal finfish cage aquaculture. Dimensional analysis was used to find significant and general interdependencies between the hydrodynamics at fish farm locations and particulate wastes deposited on the seafloor by fish farms. Modeled ratios of deposition to emission of particulate wastes underneath fish farms were found to be primarily a function of the flow Reynolds numbers at the farming locations and the non-dimensional settling velocity of emitted wastes. In the non-dimensional model, farming conditions include daily feed rate, proportion of unconsumed feed, and carbon content in feed and fish feces. The relationship can be used to estimate the PCC of floating net cages imposing a threshold value for deposition. Results of in-situ assessments of the benthic impacts of several fish farms in an aquaculture site in the northwest of Bali, Indonesia were used to validate and demonstrate the effectiveness of the method. Predicted results were able to clearly identify fish farms operating beyond ecologically sustainable carrying capacity. The proposed method has broad applicability and could help make decisions regarding the estimation of production potential of individual farms in pristine areas, for providing first estimates in sites that have scarce data, and for assessment, expansion, and optimization of the currently operating aquaculture sites in Southeast Asia, China and potentially other data-poor island nations. As the method relies on dynamic models, it enables straightforward assessments over the entire aquaculture region.     

Self-organization and mechanical properties of mussel culture suspensions: A critical review

Published information on the spatial organization of mussel culture suspensions (collectors, socks, droppers and poles) is reviewed. Despite the several hundred studies on mussel culture this type of information is very scarce but suggests that mussels self-organize into phyllotatic patterns similar to those widely studied in cylindrical/tubular biological structures and mineral crystals. I demonstrate that space regulated self-thinning (SST) models developed for plane substrates are not applicable to mussel suspensions and propose a new SST model based on the packing geometry of mussel shells around a rope. The robustness of this model is assessed by its application to a wide range of cultured populations. This comparison suggests that the carrying capacity of individual suspensions for commercial-sized mussels is equivalent to a single layer of tightly packed mussels around the rope, independently of the species, type of suspension, presence/absence of pegs, site (growth rate) and stocking density and size. The emergent mechanical properties of these porous, extremely rough and heterogeneous bodies are reviewed. The proposed SST model provides insights into the biomechanical processes of self-thinning and sloughing.     

The use of shellfish for eutrophication control

Effects of excess loading of nutrients to the marine environment can be mitigated by mussel cultures, basically through nutrient removal from the marine environment when shellfish are harvested. Shellfish farming also provide other goods and services to the marine environment primarily through the impact on water transparency caused by shellfish filtration. There is an increasing awareness of the mitigation potential in mussel culture in relation to eutrophication, but so far practical examples of culture on full scale devoted to mitigation are few. Further, impact of mussel farming on nutrient cycling, e.g. in the sediments below the culture units, has raised concerns. In this review, we clarify concepts in relation to nutrient mitigation and discuss goods and services delivered by mussel mitigation cultures and their impact on an ecosystem scale based primarily on results from studies in heavily eutrofied estuaries. A multi-criteria approach for site selection is presented based on experiences from Danish waters, and economic aspects of mitigation cultures are analysed in relation to use of the produced mitigation mussels. Future perspectives for extractive cultures are discussed in relation to source of excess nutrients.     

Evaluation of limb autotomy as a promising strategy to improve production performances of mud crab (Scylla olivacea) in the soft‐shell farming system

Soft‐shell crab, a newly moulted crab having non‐calcified and hydrated soft exoskeleton, farming has been increasing tremendously in recent years throughout the world due to its high market price and consumer preferences. However, high aggressiveness and cannibalistic behaviour of mud crab limit its culture to an individual chamber system which ultimately makes the soft‐shell mud crab farming space and labour‐intensive. Therefore, the aim of this study was to improve the efficiency of soft‐shell crab production by autotomy of the claw and/or walking legs to reduce the moulting duration and intensify the culture system through double stocking in the existing individual chamber culture system. To achieve our objectives, a series of experiment were conducted at both indoor and on‐farm levels by removing the claw and/or walking legs of Scylla olivacea for two consecutive moulting cycles. Results showed that both claw ablation significantly (p < .01) shortened the moulting duration and increased the carapace width, weight gain, specific growth rate, feeding efficiency and yield parameter compared to the non‐ablated crabs more prominently at 1st moulting than the 2nd moulting in both indoor and on‐farm trials. Ablation of all walking legs while keeping the claw intact did not significantly influence (p > .05) the moulting duration and carapace width, but significantly (p < .01) improved the specific growth rate, weight gain, feeding efficiency and yield parameters at 1st moulting compared to the non‐ablation and unilateral three walking leg ablation groups. However, ablation of all appendages (both claw and walking legs) showed significant (p < .01) improvements of carapace width, weight gain, specific growth rate, feeding efficiency and yield parameters, and shortened the moulting duration up to 23 days from 34 days during 1st moulting and up to 27 days from 40 days at 2nd moulting. The survivals of different autotomized mud crabs were statistically non‐significant (p > .05) to the non‐autotomized crabs in various indoor and on‐farm trials. Besides improving the production performances, ablation of bilateral claw and all appendages allowed to double the stocking density in the existing individual chamber‐based soft‐shell crab farming that enhanced the production about threefold higher than the existing individual chamber‐based culture system. Finally, our results suggest that autotomy could be a promising technology for the commercial farming of soft‐shell mud crab in near future.     

Preliminary Assessment of Biofouling on Offshore Mussel Farms

Biofouling is a significant operational problem for the aquaculture industry globally; however, options for on‐farm management are limited. In New Zealand, the green‐lipped mussel, Perna canaliculus, has historically been cultivated at inshore locations, but increased competition for space has led the industry to develop offshore farming sites several kilometers from the coast. We hypothesize that the distance to these farm sites from coastal locations, and their placement over extensive soft‐sediment habitats, may provide a barrier to colonization by biofouling species with limited natural dispersal abilities. A study of two offshore mussel farms revealed that they supported relatively impoverished biofouling communities by comparison with inshore mussel farms and other artificial structures. Offshore sites had a relatively low number of taxa and a low prevalence of short‐dispersing organisms such as ascidians, which are a problematic group of fouling organisms in aquaculture. We suggest that newly established offshore marine farms have the potential to be kept free of a range of problematic fouling organisms, provided the introduction of such species via human transport pathways can be mitigated.     

The status of host fish populations and fish species richness in European freshwater pearl mussel (Margaritifera margaritifera) streams

• 1. The status of host fish populations and fish species richness was investigated at 36 sites of 20 extant freshwater pearl mussel populations, including the drainages of the Elbe, Danube, Rhine, Weser, Aulne, Kemijoki and Tuuloma in Germany, the Czech Republic, France and Finland, by carrying out comparative electrofishings.
• 2. Brown trout (Salmo trutta f. fario) were found to be the available host fish for pearl mussels in all except one of the streams investigated with mean densities of 2861 ha^?1 (range 0–8710 ha^?1) and a mean biomass of 119 kg ha^?1 (range 0–478 kg ha^?1). Streams that had been frequently stocked with brown trout had higher trout biomass and densities of host fish than natural populations, but trout stocking had no positive effect in two of the streams investigated.
• 3. Fish species richness ranged from 2 to 16 species per stream and showed a negative correlation with host fish biomass and host fish densities. Undisturbed oligotrophic pearl mussel headwater streams usually only yielded a low number of fish species. Habitat degradation can reduce competitiveness of specialized trout and result in an increased abundance of ubiquitous or atypical species.
• 4. A link between the lack of juvenile pearl mussels and a lack of suitable host fish was only rarely observed. Functional pearl mussel populations with relatively high numbers of juveniles had significantly lower densities and biomass of host fish than pearl mussel populations without recent recruitment.
• 5. This study suggests that 0+ host fish are not necessarily required to sustain functional pearl mussel populations. Low densities of host fish can be compensated by the higher glochidia carrying capacity of older host fish with limited previous contact with pearl mussel glochidia, by the long reproductive period of mussels, and by low mortality rates of juvenile mussels during their post‐parasitic phase.

Copyright © 2005 John Wiley & Sons, Ltd.     

Depth matters for bivalve culture in integrated multitrophic aquaculture (IMTA) and other polyculture strategies under non-eutrophic conditions

Bivalve cultivation, in single cultivation or in polyculture (including integrated multitrophic aquaculture; IMTA), is generally limited to eutrophic waters. We carried out a modeling study to test if, under meso- and oligotrophic conditions, depth could be a key factor for bivalve productivity associated to IMTA and other polyculture strategies. We applied the model Farm Aquaculture Resource Management (FARM) at three strata of the water column in two coastal fish farm areas in the Mediterranean Sea, using water column variables sampled seasonally to estimate the potential mussel production. According to FARM, mussel production was high in both areas and, in some cases, almost doubled when mussels were cultured below 25-m depth compared to shallower levels. Phytoplankton abundance is expected to notably influence mussel production compared to particulate organic matter. Thus, in meso- and oligotrophic stratified waters, where chlorophyll maximum is relatively deep, depth can be a key factor for the productivity of mussel cultivation. The obtained results could help to maximize the production of suspension-feeding bivalve cultivation and, therefore, the expansion and development of sustainable aquaculture in non-eutrophic marine waters.     

Participation of women in oyster and mussel farming in Western Visayas, Philippines

This paper provides baseline information on the involvement of women in small-scale coastal aquaculture such as the farming of slipper oyster, Crassostrea iredalei (Faustino 1933), and green mussel, Perna viridis (Linnaeus 1758). Data were gathered during a socio-economic survey of oyster and mussel farming in Western Visayas, Philippines conducted from July to December 1991.There were 175 respondents interviewed; 18.5% and 2.4% of oyster and mussel farmers were females. Fishing and related activities were the major source of livelihood for the majority of oyster and mussel farmers. In 1990, 79.4% and 69.8% of oyster and mussel farmers earned an annual income of less than P30 000 (1 USS P23). Based on the 1988 (latest data available) poverty threshold of P2654 (monthly) for Western Visayas, 80.4% and 71.7% of oyster and mussel farmers lived below poverty level in 1990. of 175 respondents. 79.3% and 48.2% of oyster and mussel farmers indicated that their household members participated in farming activities. More female household members were involved in oyster farming compared with mussel farming. Harvesting in mussel farming and both harvesting and marketing in oyster farming generated the widest participation among female household members.