Sustainable aquaculture and aquatic resources management

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Published on 4/4/2017

Economics of Sustainable Intensification of Aquaculture: Evidence from Shrimp Farms in Vietnam and Thailand

Published on 4/4/2017
There is growing interest in sustainable intensification of aquaculture production. Yet little economic analysis has been done on farm-level effects of the economic sustainability of production intensification. Data from 83 shrimp farms (43 in Vietnam and 40 in Thailand) were used to identify (through principal component and cluster analyses) 13 clusters of management practices that reflected various scales of production intensity that ranged from 0–1999 kg/ha/crop to 10,000 kg/ha/crop and above, for both Penaeus monodon and Litopenaeus vannamei in Vietnam and Thailand. The clusters identified reflected sets of management practices that resulted in differing yields despite similarities in stocking densities among some clusters. The enterprise budget analysis developed showed that the more intensively managed clusters outperformed the less intensively managed clusters in economic terms. More intensively managed farm clusters had lower costs per metric ton of shrimp produced and were more profitable. The greater yields of shrimp produced per hectare of land and water resources in more intensively managed shrimp farms spread annual fixed costs across a greater volume of shrimp produced and reduced the cost per metric ton of shrimp. Costs per metric ton of shrimp produced decreased from the lowest to the highest intensity level (from US$10,245 at lowest intensity to US$3484 at highest for P. monodon and from US$24,301 to US$5387 for L. vannamei in Vietnam and from US$8184 at the lowest intensity level to US$3817 at the highest intensity level per metric ton for L. vannamei in Thailand). Costs of pond amendments used in shrimp production were particularly high in Vietnam and largely unwarranted, whereas fixed costs associated with the value of land, production facilities, equipment, and labor were sufficiently high in Thailand so that net returns were negative in the long run. Nevertheless, economic losses in Thailand were less at greater levels of intensification. The study demonstrated a clear value proposition for shrimp farmers to use natural resources (such as land) and other inputs in an efficient manner and supports findings from corresponding research on farm-level natural resource use efficiency. Additional research that incorporates economic analysis into on-farm studies of sustainable intensification of aquaculture is needed to provide ongoing guidance related to sustainable management practices for aquaculture.

Global Aquaculture 2050

Published on 4/4/2017

Toxicity of Four Chemotherapeutic Agents to Rabbitfish Siganus rivulatus

Published on 30/3/2017
As aquaculture evolves from extensive pond culture to intensive tank and cage systems, chemical dips and baths are increasingly being used to treat a concomitant increase in ectoparasitic and bacterial infestations. Some of the main disease-causing agents are ectoparasites on the skin and gills of fish. Consequently, application of chemotherapeutics is increasing in aquaculture industries in order to control outbreaks of parasitic infestations. However, the toxic effect of commonly used chemotherapeutic agents on specific aquacultured fish species is often unknown. The present work was performed to test the effect of four commonly used chemical treatments on rabbitfish, Siganus rivulatus. The lethal concentrations for 50% of population (LC50) of formalin, copper sulfate, potassium permanganate, and hydrogen peroxide for S. rivulatus juveniles treated for 1 h were assessed. Formalin and potassium permanganate tolerance values were determined by calculating 72-h LC50 values through probit analysis. The 72-h LC50 values for the formalin toxicity tests were 551.0 and 1.68 mg/L, respectively. LC50 of copper sulfate and hydrogen peroxide could not be determined from the concentrations tested but were found to be >3 and >700 mg/L, respectively. Accordingly, treatment concentrations of formalin and potassium permanganate used for other fish species could be lethal to S. rivulatus, but the species appears to be quite tolerant to copper sulfate and hydrogen peroxide.

Demonstration that Feeds Containing <1% Fishmeal Can Support Grow-out of Large Juvenile Red Drum, Sciaenops ocellatus, and Reduce Nutrient Waste

Published on 30/3/2017
We conducted a 16-wk feeding trial with large juvenile red drum, Sciaenops ocellatus. Four diets were randomly assigned to six replicate tanks per treatment. Three isonitrogenous (ca. 44.5% protein) and isolipidic (ca. 14.1% lipid) extruded diets were formulated to compare a fishmeal-based diet with diets using alternative protein sources. Diet 1 contained 19.60% fishmeal and 21.42% poultry meals as primary protein sources. Two alternative diets were formulated reducing the fishmeal to 0.61% by substituting poultry meals (33.85%) and soybean protein concentrate (11.55% in Diet 2 and 11.70% in Diet 3). Diet 3 also included Allzyme Vegpro® and Allzyme® SSF at 0.04%. Diet 4, a natural diet consisting of chopped cigar minnows, squid, and shrimp, was used as a positive control to compare growth rates of formulated feeds to near maximum growth under these culture conditions. We found that reducing the amount of fishmeal to <1% by using alternative protein sources did not affect the growth rate, survival, or health of red drum but improved assimilation of phosphorus, reduced potential release of P to the environment, and significantly lowered the amount of feeder fish needed in feed. The control diet identified performance benchmarks for future feeds development work.

Effects of Season, Strain, and Body Weight on Testes Development and Quality in Three Strains of Blue Catfish, Ictalurus furcatus

Published on 30/3/2017
Production of channel catfish, Ictalurus punctatus, female × blue catfish, Ictalurus furcatus, male hybrids has increased dramatically in the USA. Hybrid production requires surgical removal and maceration of blue catfish testes. Farmers report individual and seasonal variation in blue catfish testes development, and understanding the factors influencing testes development could improve hybrid catfish production. Effects of season (mid-May vs. mid-June), strain (D&B, Missouri, and Texas), and body weight on testes development in 5-yr-old blue catfish were determined. Males were measured in mid-May and mid-June for length, body weight, testes weight, and gonadosomatic index (GSI). Total sperm/g of testes, percent motility, and motile sperm/g of testes were determined. D&B strain males weighed more and had larger testes with more sperm than Missouri or Texas strain males in both months. Mature Texas strain males were larger than immature Texas strain males in both months. Testes were larger and had more sperm in May than in June for all strains; however, there were males from each strain with good quality testes in June. GSI, sperm/g of testes, percent motility, and motile sperm/g of testes were positively correlated. Information from this study provides a better understanding of factors influencing testes development in blue catfish.

Dietary Protein and Lipid Requirements for Juvenile Largemouth Bass, Micropterus salmoides

Published on 23/3/2017
A feeding trial was conducted to evaluate dietary protein and lipid requirements for juvenile largemouth bass, Micropterus salmoides. A 4 × 2-factorial layout included four protein (420, 450, 480, and 510 g/kg) and two lipid (80 and 120 g/kg) levels. Fish (initial weight 8.7 g) were fed the test diets for 8 wk. Weight gain, feed intake, feed conversion ratio, hepatosomatic index, and body composition were dependent on dietary protein level. Nitrogen retention efficiency was independent of dietary protein level, lipid level, and their interaction. Weight gain was higher in fish fed the diet containing 480–510 g/kg crude protein than in fish fed the diet containing 420–450 g/kg crude protein at two dietary lipid levels. The feed intake and weight gain were higher in fish fed the diet containing 484 g/kg crude protein and 115 g/kg crude lipid than in fish fed the diet containing 478 g/kg crude protein and 77 g/kg crude lipid. This study indicated that the suitable dietary protein and lipid levels for largemouth bass are 480–510 g/kg and 120 g/kg, respectively.

The Costs of Regulations on US Baitfish and Sportfish Producers

Published on 23/3/2017
The US regulatory environment has been characterized as complex due to the greater than 1300 laws promulgated at local, state, and federal levels. Recent declines in the growth rate of US aquaculture have been attributed, in part, to a complex, overlapping, and inefficient regulatory framework. This study is the first to examine this question by quantifying the farm-level regulatory burden and its economic effects in an aquaculture industry sector. A survey was conducted of baitfish and sportfish producers in the 13 major production states in the USA to identify the direct and indirect costs of regulation on producers. Survey responses captured 74% of the national volume of baitfish and sportfish production. The data revealed that only 1% of total regulatory costs are direct costs of regulation, such as license and permit fees, while 99% of the costs are due to manpower used for compliance, farm changes to remain in compliance, and sales lost without replacement. Costs due to regulations varied across states and farm sizes. Across all respondents, average total regulatory costs were found to be $148,554/farm, or $7383/ha. The farm-level cost to the US baitfish and sportfish industry was estimated to be in excess of $12 million. On 38% of the farms, the cost of regulations exceeded the value of profits on baitfish and sportfish farms. Our findings confirm previous reports of the complexity of the regulatory environment. Results show that the total regulatory burden has increased farm-level costs and restricted access to markets, thereby reducing profitability and contributing to reduced growth of the US baitfish and sportfish industry.

Estimation of Heritability for Growth-related Traits in Paralichthys olivaceus Using a Microsatellite-based Pedigree

Published on 22/3/2017
This study estimated the heritabilities of growth-related traits in Paralichthys olivaceus using a microsatellite-based pedigree. A set of 48 microsatellite markers located at different regions of each linkage group were selected from the published genetic map. The flounders used here originated from the Bohai Sea and the broodstock was mated to produce 10 full-sib families. The resulting fish were assayed to obtain the probabilities of exclusion (Excl 1 and Excl 2) for each marker. Sixteen markers showed low Excl 1 and Excl 2 values, eight had high probability values, and the remainder showed intermediate probability values. A marker-based pedigree of four full-factorial crosses (FFCs) was constructed using the eight markers with high Excl 1 and Excl 2 probabilities. Body measurements (such as body weight and total length) were determined in 752–943 individuals from the FFCs at 200, 400, and 500 d of age. An animal model was used for single-trait analyses and estimated moderate heritabilities, ranging from 0.23 to 0.48. These results demonstrate that markers with high exclusion probabilities provide an efficient tool for parentage assignments and genetic analyses in Japanese flounder. Marker-assisted estimation of heritability is an efficient approach to genetically improve growth traits in this species.

Quantitative Dietary Taurine Requirement for California Yellowtail, Seriola lalandi

Published on 17/3/2017
Although taurine has been identified as a required nutrient in several Seriola species, there are no available quantitative data on dietary taurine requirements for these commercially important species and recommendations are highly variable. Therefore, juvenile Seriola lalandi were fed one of eight practical diets supplemented with graded levels of taurine (0.11–1.08% of the dry diet, analyzed) to estimate their taurine requirement. Response in growth rate, feed efficiency, and nutrient deposition were evaluated using a broken-quadratic model and 4- and 5-parameter saturation kinetic models (4-SKM and 5-SKM) Blood serum composition was analyzed using linear models. Requirement estimates based on growth rates (thermal-unit growth coefficient) and protein deposition were similar at 0.26% (95% confidence interval [CI]: 0.23–0.28) and 0.29% (95% CI: 0.25–0.34) dietary taurine, respectively. Feed and protein deposition efficiencies were optimized at 0.26–1.02% and 0.26–1.00% dietary taurine, respectively. Taurine deposition in the animal was maximized at higher dietary levels (0.64%). Levels of serum taurine increased in response to dietary levels and peaked at around 0.80% dietary taurine. Concomitantly, serum urea and total amino acid levels decreased with increasing dietary taurine levels, suggesting a reduced amino acid catabolism relative to the aforementioned improvement in protein deposition efficiency.

Replacement of Fishmeal with a Blend of Poultry Byproduct Meal and Soybean Meal in Diets for Largemouth Bass, Micropterus salmoides

Published on 14/3/2017
A feeding trial was conducted to evaluate the potential of replacing fishmeal with poultry byproduct meal (PBM) and soybean meal in diets for largemouth bass, Micropterus salmoides. A reference diet (C) contained 400 g/kg fishmeal, and 40 or 60% of the fishmeal was replaced with a blend of pet-food-grade PBM and soybean meal (diets PP1 and PP2) or a blend of feed-grade PBM and soybean meal (diets PF1 and PF2). No significant differences were found in weight gain, nitrogen retention efficiency (NRE), condition factor, and body composition among fish fed diets PP1, PP2, PF1, and PF2. Feed intake and feed conversion ratio (FCR) were higher in fish fed diet PF1 than in fish fed diet PP1. No significant differences were found in weight gain, NRE, condition factor, and body composition between fish fed diet C and diets PP1, PP2, PF1, and PF2. The feed intake and FCR were lower in fish fed diet C than in fish fed diets PP2, PF1, and PF2. This study reveals that dietary fishmeal level for largemouth bass could be reduced to 160 g/kg by inclusion of PBM and soybean meal in combination.

Effects of Dietary Geniposide on Growth, Flesh Quality, and Lipid Metabolism of Grass Carp, Ctenopharyngodon idella

Published on 8/3/2017
The aim of this study was to investigate effects of dietary geniposide (GP) on growth performance, flesh quality, and lipid metabolism of grass carp, Ctenopharyngodon idella (95.2 ± 0.6 g), fed seven different diets, including a control diet; Eucommia ulmoides (EU)–supplemented diet (20 g/kg); and GP-supplemented diets containing 100, 200, 400, 600, and 800 mg/kg GP, respectively. Weight gain rate was significantly improved (P < 0.05) and feed conversation ratio was significantly decreased (P < 0.05) by supplementation of EU. Grass carp fed 100–800 mg/kg GP-supplemented diets showed significantly higher total collagen and alkaline-insoluble collagen content in muscle than control (P < 0.05). Contents of total collagen and the alkaline-insoluble collagen content in the skin of grass carp were significantly increased by dietary 600–800 mg/kg GP and EU (P < 0.05). Fish fed diets containing 600–800 mg/kg GP showed significantly lower muscle crude lipid content than the EU, control, and 100–400 mg/kg GP groups (P < 0.05). Fish fed 400–800 mg/kg GP diets had significantly higher muscle fiber density and lower muscle fiber diameter and serum triglyceride level than the control (P < 0.05). In conclusion, supplementation of GP could improve flesh quality, but not growth of grass carp. The supplemental level of GP for improving flesh quality was estimated to be a 400–600 mg/kg diet.

Optimum Dietary Protein and Lipid Levels in Juvenile Filefish, Stephanolepis cirrhifer, Feed

Published on 6/3/2017
A feeding trial was designed to assess the effects of dietary protein and lipid content on growth, feed utilization efficiency, body composition, and hematological indices of juvenile filefish, Stephanolepis cirrhifer. Eight experimental diets were formulated with a combination of four protein (35, 40, 45, and 50%) and two dietary lipid levels (7 and 14%). Each diet was fed to triplicate groups of fish (3.2 ± 0.06 g) to apparent satiation for 8 wk. Fish growth performance and feed utilization were significantly affected by increasing dietary protein and lipid levels, with no significant interactions between factors. The highest growth performance value, in terms of weight gain, was observed in groups fed the diets with 50% protein (399%). However, fish fed the diet containing 45% protein had comparable growth (357%) while achieving relatively higher protein efficiency ratio. Hepatosomatic index was significantly affected by interaction of dietary lipid and protein with the highest values observed in those fish fed the highest protein (45–50%) and lipid (14%) diets. There was a significant increase in body lipid content (5.1 to 6.6%) and a decrease in body protein (15.8 to 14.8%) and ash (2.47 to 2.16%) with increasing dietary lipid levels from 7 to 14%. Muscle lipid content was significantly affected by both dietary protein and lipid levels and tended to increase with increasing dietary protein and lipid levels, ranging from 0.13 to 1.20%. Liver lipid content (65.9 to 68.7%) was significantly increased with the increase in dietary lipid levels while liver moisture content (28.9 to 25.9%) showed a clear decreasing trend. Hematological values were also altered with the increase in either dietary protein or lipid levels. These findings may suggest that a diet containing 45% protein and 7% lipid, with a protein to energy ratio of 23.8 mg/kJ, could deliver sufficient nutrient and energy to support acceptable growth and feed utilization and avoid excessive fat deposition in juvenile filefish.

Linkages and Trust in the Value Chain for Small-scale Aquaculture in Asia

Published on 6/3/2017
The small-scale aquaculture (SSA) sector is recognized as making an important contribution to food security, poverty alleviation, and socioeconomic development. A value chain analysis can uncover insights into the linkages and trust within a value chain and constraints and challenges that face the sector. This paper examines the linkages and trust between SSA producers and traders in Asia in order to better understand the constraints and opportunities faced by small-scale producers. The perspective revealed by the value chain analysis provides response strategies that can enhance the sustainability and competitiveness of the entire value chain and the actors that comprise it.

Methionine Requirement for Juvenile White Seabass, Atractoscion nobilis, Using Nonlinear Models

Published on 2/3/2017
Two trials were conducted to estimate the methionine (Met) requirement of juvenile white seabass, Atractoscion nobilis. Diets were formulated to contain 40% crude protein, 10% lipids, and 0.51% cysteine. Graded levels of dl-Met were added to create seven diets with dietary Met levels ranging from 0.72 to 0.98%, and nine diets ranging from 0.64 to 1.28% Met in Trials A and B, respectively. Thermal-unit growth coefficient was fitted to dietary Met levels to estimate the Met requirement using the saturation kinetic model (SKM), the quadratic model (QM), or the broken quadratic model (BQM). The 95% confidence interval (CI) was estimated through the iterative fitting process for the BQM and using a bootstrapping approach for the QM and SKM. In Trial A, the three models estimated the requirement between 0.88 and 1.08%, with wide CI. In Trial B, precisions of the requirement estimates by the SKM and BQM were significantly improved compared with Trial A, though BQM evidently overestimated the requirement. SKM provided the best fit; hence, we conclude that the Met requirement for juvenile white seabass is 0.88% (95% CI: 0.80–1.08%) in the presence of 0.51% cysteine. This estimate provides valuable basis for the formulation of practical diets for juvenile white seabass.

Comparison of Protective Efficacy between Formalin-killed and aroA Gene-knockout Vibrio anguillarum Vaccines in Olive Flounder, Paralichthys olivaceus

Published on 2/3/2017
The aro genes in bacteria encode enzymes needed for the biosynthesis of aromatic amino acids, and mutant bacteria that are defective in the enzymes can replicate only a limited number in vertebrates owing to the lack or scarceness of chorismate, through which the mutant bacteria of the aro genes become attenuated. In the present study, the 5-enolpyruvylshikimate-3-phosphate synthase (aroA) gene-knockout Vibrio anguillarum (ΔaroA V. anguillarum) were generated by the allelic exchange method, and its vaccine potential was evaluated in the olive flounder, Paralichthys olivaceus, by comparing the protective efficacy of a formalin-inactivated V. anguillarum. The LD50 (50% lethal dose) value of ΔaroA V. anguillarum was 1000 times higher than that of wild-type V. anguillarum in olive flounder fingerlings, and the growth of ΔaroA V. anguillarum was significantly suppressed by coincubation with nonimmune olive flounder serum compared with that of wild-type V. anguillarum. The survival rates and serum agglutination titers of fish immunized with ΔaroA V. anguillarum were significantly higher than those of fish immunized with the same amount of formalin-inactivated V. anguillarum, suggesting that although the inactivated V. anguillarum vaccine can provide a high protection in olive flounder, the protective efficacy can be enhanced by immunization with an auxotrophic mutant ΔaroA V. anguillarum.

Service as a Peer Reviewer: Professional Responsibility, Recognition, and Benefits

Published on 1/3/2017

Quantifying Aquaculture-derived Dissolved Organic Matter in the Mesocosms of Sanggou Bay Using Excitation-emission Matrix Spectra and Parallel Factor Analysis

Published on 28/2/2017
The cycling and fate of dissolved organic matter (DOM) in aquaculture systems are unique. Sanggou Bay, an aquaculture-dominated system in China, was chosen to characterize the composition of DOM based on optical properties. Field incubation experiments of eight mesocosms containing various aquaculture organisms were conducted in July 2013 to explore the impact of aquaculture organisms on the DOM composition. Dissolved organic carbon (DOC) showed an increasing trend, especially in integrated mesocosms, suggesting the accumulation of DOM in the aquaculture ecosystem. The DOC concentration was positively correlated with a280 (P < 0.01) rather than a355, demonstrating that a280 should be applied in the quantitative prediction of DOC in aquaculture systems. Parallel factor analysis was applied to identify the components of the excitation-emission matrix spectra. Two humic-like components and two protein-like components were identified. The significant correlation between the wet weights of the organisms and the humic-like component contents (P < 0.01) indicated that seaweeds and bivalves play important roles in the production of humic-like matter. The variation of protein-like materials was caused by the growth of aquaculture organisms and the decay of phytoplankton. The amount of bioavailable DOC (BDOC) derived from phytoplankton and organisms was estimated; bivalve organisms excreted more BDOC than did seaweeds. BDOC was significantly correlated with the protein-like components (P < 0.05) in the microbial incubation experiment.

Design Characteristics of Spiral Aerator

Published on 23/2/2017
In this study, the performance of a spiral aerator, a modified design of the paddlewheel aerator, was evaluated to determine its applicability in aquaculture ponds. The aeration characteristics of the spiral aerator were determined by conducting aeration experiments in a cement concrete tank of dimension 5 × 5 × 1.5 m. Nondimensional numbers related to oxygen transfer (E) and power consumption (Ne) were proposed and expressed as functions of geometric (number of handles per shaft, n) and dynamic (Froude and Reynolds number) parameters. Simulation equations for oxygen transfer and power consumption based on the Froude criterion were developed. The maximum brake power standard aeration efficiency was achieved at n = 13. Finally, an economic analysis was performed assuming a typical Indian major carp culture pond to determine the optimum rotational speed of the aerator at different pond volumes and dissolved oxygen concentration present in the pond at which the aeration cost is minimized. The results showed that the least aeration cost is achievable when rotational speed of the spiral aerator is only 70 rpm for pond volumes up to 700 m3 and from 120 to 220 rpm for pond volumes exceeding 700 m3.

Likely Effects of the Increasing Alkalinity of Inland Waters on Aquaculture

Published on 8/2/2017
The rising atmospheric carbon dioxide (CO2) concentration is increasing the solubility of limestone, calcium silicate, and feldspars, resulting in greater total alkalinity concentration in inland waters. This phenomenon will result in inland waters having slightly greater alkalinity concentration (and buffering capacity), higher pH when at equilibrium with atmospheric CO2, and more available carbon for photosynthesis. However, the changes in water quality will be small. Fluctuations in CO2 concentration resulting from CO2 use in photosynthesis by aquatic plants and release of CO2 by respiration, acidity resulting from nitrification of ammonia nitrogen from feeding waste and fertilizer, and application of liming materials to ponds will continue to be the dominant factors affecting pH and alkalinity in waters of inland aquaculture systems.

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