Tropical spiny lobster (Panulirus ornatus) farming in Vietnam – bioeconomics and perceived constraints to development

This paper presents bioeconomic data on lobster farming in Vietnam, and perceived constraints to the development of the industry. The farms were found to be profitable, with an average benefit cost ratio of 1.44 and an average net revenue of 262 million VND year^?1 (or just under US$15 000 year^?1). Investment in the enterprise is high compared with other enterprises in the region. However, disease has the potential to devastate lobster crops and there is little information available to lobster farmers about disease prevention and management. Hence, the lobster enterprise is a high‐risk high‐return industry. The predominant perceived constraints to the development of lobster operations include water quality and temperature issues, insufficient access to credit, good‐quality affordable feed and accurate information about technology improvements in lobster farming. It seems that improving the livelihood of lobster farmers in Vietnam is dependent on reducing their dependence on wild stocks for seed and feed, improving access to credit and improving technical and market information flows. Such improvements are likely to lead to higher profitability, given high export demand and hence sustained high prices for their lobster product.     

Production economics of the emerging private fish farming industry in Bulgaria

The production economics of the emerging Bulgarian private carp and trout farming industry were assessed by surveying a representative sample of 20 private and state-controlled farms as well as visiting the National Fresh Water Fish Research Institute, the state-owned fish feed production plant and a fish processing plant.The major constraints for the development of profitable fish farming were found to be the lack of capital and the insecurity of tenure, which nonetheless, do not serve to discourage new entrants into the industry. The expected gross margin per tonne of carp produced in reservoirs or earth ponds is USD 487, while a tonne of trout farmed in concrete raceways shows a gross margin figure of USD 525. State-owned trout farms are only available for outright purchase at auctions, whereas carp farms may be rented, but only for a short term.Fish farmers could benefit from organizing themselves into producer groups in order to improve marketing and secure quality inputs. In particular, there is scope to source quality dry fish diets on both economic and environmental grounds.An extension advisory service is needed to support inexperienced new entrants and researchers should urgently evaluate what seem to be the most cost-effective methods of production.     

Economic Feasibility of Aquaculture of Spiny Lobsters Jasus edwardsii in Temperate Waters

Around the world there is strong interest in the aquaculture of spiny lobsters (family Palinuridae). However, there is little published information about the economic feasibility of spiny lobster aquaculture. For more than 20 yr there has been experimental grow out of the spiny lobster Jasus edwardsii in New Zealand in land-based systems using seed animals (puerulus) taken from the wild. These studies provide sufficient information on growth, mortality, food conversion, handling and capital costs to enable an assessment of the economic feasibility of the commercial culture of spiny lobsters in temperate waters. This assessment suggests that profitable spiny lobster aquaculture will rely on greatly reducing the infrastructure and operating costs of land-based farming operations, as well as lowering feed and labor costs. Financial simulations suggest that increasing productivity through faster growth rates and lowered culture mortalities will only have a minor effect on profitability unless infrastructure and operating costs can be reduced significantly. Seacage culture or sea ranching of spiny lobsters may offer a means of avoiding high infrastructure costs associated with land-based farming operations. The development of a cost-effective artificial feed would also appear to be a priority for improving the economic outlook for culturing spiny lobsters. The results of this study are relevant to the economics of spiny lobster culture developments in other temperate regions of the world.     

Evaluation of Reduced Fish Meal Diets for Second Year Growout of the Largemouth Bass,Micropterus salmoides

Development of efficient cost‐effective diets is a critical component in the refinement of production technologies for the largemouth bass, Micropterus salmoides (LMB). One of the first steps in reducing feed costs can be to decrease the amount of fish meal in the diet. The objective of this study was to evaluate reduced levels of fish meal, and a least‐cost formulation diet, for second year growout of LMB under practical pond conditions. Twelve 0.04‐ha ponds were stocked with juvenile LMB (210.1 ± 3.3 g) at a stocking density of 8650 fish/ha (350 fish/pond). Each pond was randomly assigned one of the four dietary treatments with three replicate ponds per treatment. The three experimental diets contained varying levels of fish meal. Diets FM‐45, FM‐24, and FM‐8 contained 45, 23.5, and 8% fish meal, respectively. In diets FM‐24 and FM‐8, fish meal was replaced by varying levels of poultry by‐product meal, soybean meal, and blood meal. The fourth diet was a commercial salmonid diet widely used as a LMB growout feed (Nelson and Sons, Inc., Silvercup ^TM , Steelhead, Murray, UT, USA). This diet served as a commercial control (CC) and contained 46% crude protein. The experimental diets were formulated to be isonitrogenous and isocaloric with the CC diet and were fed once daily to apparent satiation for 180 d. At harvest, there were no significant differences between treatments ( P > 0.05 ) in terms of survival, which averaged 95% overall. Mean weights of fish fed the three experimental diets FM‐45, FM‐24 and FM‐8 were not significantly different ( P > 0.05 ) and averaged 518, 546, and 529 g, respectively, but were all significantly greater ( P≤ 0.05 ) than those fed the CC (488 g). Feed conversion ratio (FCR) of fish fed the FM‐45 and FM‐8 diets (1.43 and 1.46, respectively) was significantly greater ( P≤ 0.05 ) than those fed the FM‐24 diet (1.34). The FCR of fish fed the CC diet (1.39) was not significantly different ( P > 0.05 ) from fish fed other diets. Feed cost per unit of weight gain ($US/kg) was significantly lower ( P≤ 0.05 ) in fish fed the FM‐24 and FM‐8 diets ($0.73 and $0.72/kg, respectively) than in fish fed other diets. Feed cost per unit gain of fish fed the FM‐45 diet ($0.83/kg) was significantly lower ( P≤ 0.05 ) than those fed the CC diet ($1.04/kg). There were no significant differences ( P > 0.05 ) in dress‐out percentages or proximate composition among fish fed the four diets. This study indicates that fish meal levels in feeds used for the second year growout of LMB can be reduced to ≥ 8% of the formulation without reducing survival or growth and without negatively impacting body composition.     

Size Economies of a Pacific Threadfin Polydactylus sexfilis Hatchery in Hawaii

A spreadsheet model has been developed to determine the viable scale for a commercial Pacific threadfin Polydactylus sexfilis hatchery in Hawaii. The production scheme is modeled after current practices performed at the Oceanic Institute in Waimanalo, Hawaii. For a hatchery enterprise producing 1.2 million fry per year, the cost associated with raising one 40‐d‐old 1.00‐g fry is estimated at 22.01ø. The largest variable costs are in labor and supplies, which comprise 49% and 9% of the total production cost. The combined annualized fixed cost for development and equipment is approximately 12% of total production cost. At a sale price of 25ø per fry, the 20‐yr internal rate of return (IRR) is 30.63%. In comparison to the 22.01ø unit cost for 1.2 million fry production, analyses of smaller enterprises producing 900,000 and 600,000 fry per year reflected significant size diseconomies with unit costs of 27.41ø and 38.82ø, respectively. Demand to support a large scale Pacific threadfin commercial hatchery is uncertain. Since smaller scale commercial hatcheries may not be economically feasible, facilities may seek to outsource live feed production modules or pursue multiproduct and multiphase approaches to production. An analysis of the production period length, for example, indicates that the cost for producing a day‐25 0.05‐g fry is 17.25ø before tax and suggests the financial implications of transferring the responsibility of the nursery stage to grow‐out farmers. Evaluation of the benefits gained from changes in nursery length, however, must also consider changes in facility requirements, mortality, and shipping costs associated with transit, and the growout performance of and market demand for different size fry. Sensitivity analyses also indicate the potential cost savings associated with the elimination of rotifer, microalgae, and enriched artemia production. Managerial decisions, however, must also consider the quality and associated production efficiencies of substitutes.     

An evaluation of potential diets for the culture of postpueruli spiny lobsters Panulirus argus (Palinuridae)

Provision of a suitable feed is paramount for the ongoing success of spiny lobster culture. This study compared and evaluated the performance of seven diets for first instar juvenile spiny lobster Panulirus argus [5–6 mm carapace length (CL)] based on growth rates, survival, and feed conversion ratio. Results demonstrated that a seafood-based juvenile formulation produced the fastest growth rate (3.49% weight gain day⁻¹ and 0.90% CL increase day⁻¹ over a 28-day period). These growth rates were also reflected by a low feed conversion rate (3.04) for this formulated feed. Similar results were also obtained for juveniles fed a frozen seafood diet, however, frozen brine shrimp, Artemia salina (both enriched and un-enriched), frozen enriched mysis shrimp, a dry pellet, and a meal-based juvenile formulation did not produce consistent growth rates. Survival rates ranged between 38% and 85% and demonstrate that juvenile lobsters have better likelihoods of survival in captive culture environments compared to the wild. Although further nutritional refinement is recommended, the results from this research have significant implication for the possible expansion of juvenile spiny lobster growout to a larger scale.     

Evaluation of Commercial Shrimp Grow-Out Pellets as Diets for Juvenile Southern Rock Lobster,Jasus edwardsii

Abstract

The growth, survival, and biochemical composition of juvenile southern rock lobster, Jasus edwardsii, were examined in response to a variety of diets, consisting of a natural food organism (blue mussel, Mytilus edulis) and/or commercial shrimp pellets. Blue mussel supported significantly better (a minimum of 25% higher) growth than a range of shrimp diets. Diet intake (0.83-1.26% wet body weight/day) and feed conversion ratio (1.34-2.48) with the formulated diets were generally similar to that with blue mussel (1.03% wet body weight/day; 1.55 feed conversion ratio). Changes in the chemical composition of southern rock lobsters due to treatments were more clearly observed in the digestive gland than in the whole body. Carapace color and tissue carotenoid level varied significantly with carotenoid content of the diets. A caro-tenoid level of 115 mg/kg is required in formulated diets to produce southern rock lobsters of similar color to wild-caught juveniles. In a separate experiment, a blue mussel diet was compared to mixed diets comprised of blue mussel and a shrimp, Penaeus monodon, diet. In the mixed diets, blue mussel was replaced with the formulated diet for either ×days/week or 6 days/week. Growth and survival did not differ significantly among treatments. The use of formulated diets in the culture of southern rock lobster appears feasible but will require increased knowledge of the nutritional requirements. Until specific diets are developed, this study has shown that similar growth can be obtained from a mixed diet, consisting primarily of a cheap formulated diet supplemented with blue mussel once per week. Such a scenario offers real possibilities for significantly reducing the cost of southern rock lobster production.     

BIOECONOMICS OF COBIA,RACHYCENTRON CANADUM,CULTURE IN VIETNAM

This article presents an analysis of the profitability and intensity of cobia culture by small-scale farmers in Vietnam, especially focusing on current feeding practices and perceptions regarding adoption of manufactured diets. Bioeconomic modelling is used so the interactions between biological and economic processes can be analyzed. Overall, it is found that cobia farming is moderately to highly profitable when compared to other aquaculture species in Vietnam. Culture practices and the level of intensity of cobia farming differ significantly across Vietnam. Initial stocking density, total number of fish stocked, number and size of cages, and quantity of feed used are all higher in southern Vietnam than the north. The higher level of intensification in the south leads to significantly higher total costs, productivity and profitability. The dominant cost source is feed, which is predominantly low-value fish. To capture the environmental and potential economic benefits of adopting pelleted diets, then negative farmer perceptions regarding relatively slow growth rates, and lack of availability compared with low-value fish need to be overcome.     

Cost–benefit analysis of two culture methods that influence pearl production from the black‐lip pearl oyster,Pinctada margaritifera

The black‐lip pearl oyster, Pinctada margaritifera, used for round pearl production in Polynesia, is generally cultured using “ear‐hanging” where they are attached to a rope to form “chaplets.” In other countries, pearl oysters are cultured using panel (pocket) nets that are more expensive than chaplets but afford more protection to cultured oysters. Prior research has shown panel nets produce pearls of higher quality and value, potentially generating higher profits. This study used cost–benefit analysis to compare pearl production using chaplet‐based and panel net‐based culture methods. Whole farm data, including gross revenues and annual production costs, fixed and variable, were analyzed. Average production cost per pearl using panel net‐based culture was USD 22.47 and for chaplet‐based culture was USD 21.55. However, use of panel nets saved around 3,430 hr (USD 6,860) of labor a year, offsetting the greater capital investment. A chaplet‐based pearl farm generated USD 65,738 in annual profits compared to USD 88,774 for a panel net‐based farm. Positive cash flow was achieved 1 year earlier (Year 7) for the panel net‐based farm. This is the first economic analysis of different pearl culture methods for P. margaritifera and evidence of profitability will support further development of the black‐lip pearl industry in the Indo‐Pacific region.     

Optimal feed pellet size for culturing juvenile spiny lobster Jasus edwardsii (Hutton, 1875) in New Zealand

There is intense international interest in the development of spiny lobster aquaculture and of particular interest is the development of artificial diets for spiny lobsters. However, there is little information on the feeding behaviour of spiny lobsters and their ability to handle and consume artificial feeds of different dimensions. Observations of the feeding behaviour of juveniles of the spiny lobster Jasus edwardsii in culture found that they waste significant amounts of food through externally fragmenting the feed pellets before sweeping particles into the mouth. The consumption efficiency of different sized pellets was found to change markedly with increasing size of the juvenile lobsters. Up to 50% of artificial food was wasted by the inefficient feeding behaviour of the lobsters. However, consumption of the feed could be reduced by as much as 19% by altering pellet size. These results indicate that the size of feed pellets, and their consistency and fragmentation characteristics, will be critical aspects of cost‐effective feeding of cultured spiny lobsters.     

Stability of Formulated Diets and Feeding Response of Stage I Western Spiny Lobster, Panulirus cygnus, Phyllosomata

This study is a preliminary assessment of suitable binders and formats of potential formulated diets for hatchery growout of early‐stage western spiny lobster, Panulirus cygnus, phyllosomata. Six dry meal (each bound with a different binder) and three gelatinous (all bound using gelatine) diets were tested for stability in water over increasing periods of time (4, 8, and 12 h), and the feeding response to each was observed by video analysis. The gelatinous krill diet appears most suited to the larval feeding biology of P. cygnus phyllosomata as it elicited a heightened feeding response immediately following immersion, was most stable in water up to 4 h, and did not foul the maxillae during ingestion. The dry meal diets were not as stable in water and contributed to excessive fouling of the maxillae during ingestion. Of the dry meal diets, the most suitable was bound with 5% k‐carrageenan, presumably because of high moisture content and softer texture.     

Betaine supplementation enhances the seawater adaptation of salmon, Salmo salar L.

Abstract. The growth of the Atlantic salmon, Salmo salar L., aquaculture industry has been tremendous; from a modest beginning, today's world production of salmon farming is close to 260 million tonnes in ten different countries. In particular the last 20–30 years have seen a dramatic increase in annual sales and production.
The methods vary. From exploiting the natural migrations of this anadromous fish, sea ranching has produced a viable industry. However, controlling the entire life cycle in closed systems has been more successful.
The growth of the farming industry is seriously hampered by such factors as diseases and parasites, algae blooms, environmental pollution, sabotage and rough seas. Several of these factors will not easily be eliminated, although methodical research and development could make the fish farming industry more efficient. Most of the fish farming is situated in remote regions, and the product has to be transported to heavy populated areas for sale, often across borders. The approximate average production costs per kilo differ according to the organization of the industry, average salary, the feed costs and the industrial hurdles, expressed as loss of fish, due to a variety of factors. Even though the market is growing, we must expect fierce competition. Farms producing fish of high quality at low cost will survive. The industry needs healthy fish in well-run farms, smart farmers and a government which helps the industry with reasonable regulations, guidance, applied and basic research, and insight into the future.     

Optimizing diets to decrease environmental impact of Nile tilapia (Oreochromis niloticus) production

Aquaculture is one of the most thriving animal production sectors, and Nile tilapia (Oreochromis niloticus) farming represents 8% of total finfish culture. However, the industry sustainability depends on the development of cost‐effective and environmental friendly feeds. This study aimed to reduce dietary protein levels in diets for juvenile tilapia and to minimize diet environmental impact while maximizing biological efficiency. A growth trial was performed using five isoenergetic plant protein‐based diets with decreasing levels of crude protein: 360, 340, 320, 300 and 280 g/kg diet (D360, D340, D320, D300 and D280, respectively). Dietary protein utilization was assessed by metabolic trials using a radiolabelled amino acid mixture. Tilapia in all treatments showed similar growth performance and feed intake. Feed conversion ratio was significantly higher in fish fed the D280 than the D360 diet, while no differences were found for other treatments. Protein retention was significantly higher in tilapia fed the D300 than the D360 diet. Amino acid catabolism increased in fish fed the D360 diet, though without significant differences in muscle amino acid retention. This study demonstrates that dietary protein levels can be reduced to 300 g/kg diet without hindering tilapia growth and feed conversion ratio, while reducing environmental nitrogen losses.     

Use of Microbial Flocs Generated from Tilapia Effluent as a Nutritional Supplement for Shrimp, Litopenaeus vannamei, in Recirculating Aquaculture Systems

Recovering nutrients in a fish effluent to be used as a supplemental feed for shrimp culture could ease constraints (e.g., environmental issues and high production cost) that have limited the US shrimp farming industry in the past. In this study under laboratory scale conditions, fish effluent was collected from a commercial tilapia farm and nutrients from the waste stream were offered as supplemental feed as either (1) untreated solids from tilapia effluent or (2) microbial flocs generated from the biological treatment of the effluent by reducing soluble chemical oxygen demand >80%. The first feeding trial demonstrated that microbial flocs contributed significantly (P < 0.05) to overall growth while untreated solids did not. Moreover, microbial flocs were larger and contained higher levels (P < 0.05) of protein. The second feeding trial investigated different feeding rates of commercial diets with and without microbial floc supplementation. Weekly measurements of mass and specific growth rates demonstrated that microbial flocs significantly (P < 0.05) contributed to shrimp performance. Weekly food conversion ratios were also reported. Water quality in shrimp systems during both studies was within safe levels, and no differences (P > 0.05) between treatments were observed for dissolved oxygen, nitrate‐nitrogen, nitrite‐nitrogen, pH, salinity, total ammonia nitrogen, and temperature.     

A cost‐effectiveness analysis of live feeds in juvenile turbot Scophthalmus maximus (Linnaeus, 1758) farming: copepods versus Artemia

The biological benefits of copepods as live feed for marine finfish larvae have already been well established in the literature. Copepods have better biochemical compositions that improve growth, reduce malpigmentations and allow successful farming of ‘new’ marine finfish species. However, their current usage is quite limited. One of the reasons has been lack of economic knowledge concerning the cost‐effectiveness of copepod application compared to other commonly used feed items such as the brine shrimp Artemia. In this study, a cost‐effectiveness analysis is made on two alternative live feed items (copepods and Artemia) in juvenile turbot farming. Unit cost of production and profit are compared between the two feeding regimes using a unique data set from an existing turbot fry production facility in Denmark. The result reveals that copepods are not only biochemically superior but they are also economically a cost‐effective alternative. Thus, a commercial use of copepods will significantly reduce the production costs for turbot. Furthermore, the unexploited economic potential can be utilized for the successful farming of other high‐valued marine finfish species such as tuna, flounders, cod, sole and halibut. Generally, the biochemical superiority coupled with economic benefits can lead to the commercial utilization of copepods as complementary live feed in the short run and in some situations as a substitute in the long run.     

新加坡观赏鱼产业发展的机遇与挑战

新加坡是一个小岛国,农业用地及用于养鱼的海域面积均很有限。但新加坡观赏鱼产业相当独特和成功,是世界第一观赏鱼出口国,向80多个国家出售超过1 000种鱼类,2016年的年收入达到4 300万美元。该产业的成功主要源于其在许可证颁发,生物安全控制,养殖,包装,运输和疾病控制等各方面所具有的独特特征。新加坡正在努力驯养和培育许多高价值的海洋物种和新的淡水物种,并开发新型的循环水养殖系统。上游研究侧重于开发和使用基因组工具来培育新品种并维持野外种类的遗传多样性。但由于养殖鱼类的空间有限,邻国竞争激烈,该行业面临诸多挑战,其市场份额正在减少。在这篇综述中,我们将总结新加坡观赏鱼产业的现状和发展,讨论其面临的挑战,并提出保持该产业领先地位的建议。     

Growth performance,feed utilization and body composition of advanced nursing Nile tilapia (Oreochromis niloticus) fed diets containing Black Soldier Fly (Hermetia illucens) larvae meal

A 32‐day experiment was conducted to evaluate the effects on the performance, feed utilization efficiency and body composition of a strategic inclusion of Black Soldier Fly larvae meal (MM) in a commercially formulated diet for advance nursing Nile tilapia (Oreochromis niloticus). Four isonitrogenous and isoenergetic diets were commercially formulated and manufactured as a control and three test diets with strategic inclusions of MM inclusions (0, 30, 50 and 80 g/kg) and poultry by‐product meal substituting gradually three conventional expensive feedstuffs: fish meal, fish oil and soybean meal. Fish (5.7 ± 0.5 g/fish) were nursed in a cage‐in‐lake system (Volta Lake, Ghana), under conditions similar to commercial farming practices. Control and experimental diets were fed to triplicate cages by hand to visual satiety, six times per day. Growth performance (final weight; weight gain and SGR), feed utilization efficiency indices (FCR and PER) and feed intake were not significantly different (p ≥ .05) between treatments. Survival was significantly different (p < .05) but more likely explained by the stress related to frequent handling on the smaller fish. Fish whole body composition (dry matter, crude protein, lipid, ash and fibre) was unaffected by the treatment (p ≥ .05), except for the fatty acid compositions which mirrored that of the diets.     

中国鲟鱼产业技术研发现状与展望

2016年中国鲟鱼养殖产量89 773吨。鲟鱼种苗、饲料、养殖、加工及销售等环节的一些实用技术基本能满足鲟鱼产业的现实需要,但仍然存在不少问题,如种质退化问题、鱼子酱及鱼肉的品质问题、养殖过程中的氮磷排放问题。本文就中国已经形成的鲟鱼产业技术进行梳理、评述和展望。     

Effects of Reduced Levels of Dietary Protein and Menhaden Fish Meal on Production,Dressout, and Biochemical Composition of Phase III Sunshine Bass Morone chrysops ♀× M. saxatilis ♂ Cultured in Earthen Ponds1

The responses of phase III sunshine bass Morone chrysops ♀× M. saxatilis ♂ to diets containing reduced levels of menhaden fish meal (30–10%, dry weight) and crude protein (40–36%, dry weight) were evaluated in two separate experiments. Reductions in fish meal were compensated by increase in dietary soybean meal, a meat and blood meal product, and additional amounts of a 1:1 catfish oil:menhaden oil mixture sprayed on as a top dressing. Fish were cultured in earthen ponds and fed commercially manufactured, extruded diets to apparent satiation. In Experiment 1, dietary crude protein was reduced from 40 to 36% and the menhaden fish meal ingredient was reduced from 30 to 15% (dry weight). The mean weight of fish stocked into each pond ranged from 144 to 188 g, the stocking density was 8641/ha, and the duration of the growout was 172 d. In Experiment 2, both dietary treatments contained 40% crude protein (dry weight) and either 30% or 10% menhaden fish meal. The mean weight of fish stocked into each pond ranged from 42 and 77 g, the stocking density was 8,500/ha, and the duration of the growout was 175 d. Simultaneous reductions in dietary menhaden fish meal and crude protein resulted in significant decreases in all production indices except survival and percent weight increase. Weights of filet, carcass, liver and intraperitoneal fat, expressed as a percent of total body weight, were not significantly different. A 66% reduction in dietary menhaden fish meal while the crude protein level was maintained at 40% did not significantly affect growth, production, and weights of filet, carcass, liver and intraperitoneal fat, expressed as a percent of total body weight, and represents a 6% decrease in the cost of feed. In both experiments, levels of protein, lipid, moisture, and ash of the whole body and the filet were not significantly different. Fatty acid composition of the filet and livers from fish fed the control and experimental diets in Experiment 2 were highly comparable. The comparable level of performance of fish fed diets believed to be deficient in HUFA suggests that the dietary levels reported to be required may not be totally applicable to diets formulated for pond culture.     

Prolonged Culture Period on Production Cost and Factor Input: A Case from the Pacific Oyster,Crassostrea gigas,Farming Industry in Yunlin County,Taiwan

The Yunlin coastal area is the largest oyster culture in Taiwan; however, the oyster farmers reported the negative impact of a prolonged oyster culture period and an increased operating cost in 2010. This study uses the translog cost function to consider the possibility of an oyster culture period extension to estimate oyster cost elasticity, own‐price elasticities, and cross‐price (substitution) elasticities, to evaluate whether the oyster farming industry in Yunlin County has economies of scale, and to assess the relationship with a substitution of inputs. We found that the Yunlin oyster culture has economies of scale, and that the oyster farmers can expand production scale to reduce costs. The own‐price elasticities of demand for inputs are less than 1, indicating fairly inelastic factor demands in oyster production. The oyster farming industry displays strong substitutability between the prolonged culture period and capital input, suggesting that the oyster farming industry is more responsive to a higher prolonged culture period cost, in terms of capital input.