Category Archives: Aquaculture

 “A Study on the Growth of Juveniles of Tiger Prawn, Penaeus monodon (Fabricus), Under Different Photoperiods.” (Chatterji et al 2015)

Citation: Chatterji, A, Pati S, BP D (2015). ” A Study on the Growth of Juveniles of Tiger Prawn, Penaeus monodon (Fabricus), Under Different Photoperiods.” Aquaculture Research and Development, 6(12), doi:10.4172/2155-9546.1000385

Summary By: Alexandra Pounds

BIG PICTURE:

  • Many biological cues of P. monodon are from light (mating, spawning, burrowing). This study wanted to see the effect of light on growth in juveniles (50-150mm).
  • Methods:
    • Juveniles were collected from a commercial hatchery and acclimatised to lab conditions for 1 week before light testing began.
    • Weight, temperature, salinity, pH of 20L glass tanks were held constant, as was feed and water exchange. The only difference was that one tank was exposed to constant light while the other was kept in darkness. Length and weight was measured weekly for 11 weeks.
  • Results:
    • LENGTH: The increase in length was not significantly different between shrimp in the light and dark tanks. In the dark tanks, the increase in length was more rapid until the 6th week, then slowed down. At the end of the experiment there was no difference in average length.
    • WEIGHT: The shrimp in the dark tanks were significantly heavier than the shrimp in the light tanks due to increased weight gain between week 7 and 10.
  • Implications:
    • Other studies have found that using darkness for juveniles of other species has also increased weight. Using darkness also increased FCR. Other studies found no difference between growth rates for juvenile shrimp species exposed to light versus dark conditions.
      • While no significant difference in growth rate was found, studies hypothesize that since lobsters eat at night, having longer dark periods could increase feeding rates and hence, growth rates.
      • Another study also found that P. monodon juveniles grow faster under dark conditions.
    • In production, keeping juvenile ponds shaded could help maximize production.
  • Alexandra’s thoughts:
    • Is the same true for postlarvae? Have they’re been studies on PLs? The trouble with larvae is that we have to sustain algae within the tank, and the algae require lighting, which is why the industry standard is to keep continuous light on the tanks… But perhaps this is limiting growth?
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“A crustin isoform from black tiger shrimp, Penaeus monodon exhibits broad spectrum anti-bacterial activity” (Banerjee et al 2015)

Citation: Banerjee, D., Maiti B, Girishna S, Venugopal M, Karunusagar I. (2015) “A crustin isoform from black tiger shrimp, Penaeus monodon exhibits broad spectrum anti-bacterial activity”. Aquaculture Reports, 2, pp. 106-111.

Summary by: Alexandra Pounds

BIG PICTURE: P. monodon, like many other crustaceans, releases crustins, which are broad-range antimicrobial peptides in the blood that can be effective against a variety of both weak-celled bacteria and antibiotic-resistant bacteria. This study isolated the crustin of one particular P. monodon, and compared it with RNA from other studies to see the variability of the crustin formation (in terms of both amino acid composition and isoform). The study found that crustins have so many forms, which may be the reason they can address so many different types of bacterial infections. 

  • P. monodon, like other crustaceans, have a nonspecific immune response. They release general, rather than specific, Antimicrobial peptides (AMPs) among other substances, when Pattern Recognition Proteins (PRPs) identify a bacteria, fungus, etc. These PRPs are in the haemocytes (the invertebrate version of blood).
  • Crustins:
    • Crustins are a type of cationic (positively charged ion), cycteine-rich (type of amino acid) AMP that are released by haemocytes in crustaceans when haemocytes are exposed to microbes.
    • There are three types of Crustins (I, II, and III), although type II is the most abundant.
    • Many Crustin isotopes (different molecule shapes) have been identified throughout different crustacean species.
    • Crustins are more effective against gram-positive bacteria (bacteria with weaker cell walls, less resistant to antibiotics. Gram-negative bacteria has thin but strong cell walls that can become antibiotic resistant). But this study identified a crustin in P. monodon that worked against both gram-positive and gram-negative.
  • Methods:
    • 20g farmed-raised P. monodon from Southwest India was used.
    • V. harveyi was isolated from a dead shrimp, grown in culture, then injected into the muscles between the 3rd and 4th segment of a healthy shrimp.
    • 18h after injection, haemocytes were drawn for both the injected shrimp and a control shrimp. RNA was extracted from the haemocytes and cloned  (using PCR-type techniques), then sequenced and compared against GenBank Data.
    • In vitro: various gram-negative and gram-positive bacteria were grown on TSA (general agar) plates, and exposed to the crustins. They used various concentrations of crustins to determine the minimum inhibitory concentration (MIC) – what is the minimum amount of crustin needed to fight the bacteria?
  • Results:
    • The crustin sequence was compared to GenBank, and was similar to other P. monodon, but very different from crabs or other crustacean species.
  • Implications:
    • Crustins are the most diverse AMPs, varying by just 1-4 amino acids and having many different isotope forms. This high variability could explain how they can defend against so many types of bacteria (this broad range antimicrobial activity was statistically significant).
    • Understanding crustins’ antimicrobial activity against V. harveyi  is particularly important for the shrimp industry, as this bacteria causes much mortality.
  • Alexandra’s thoughts:
    • If we can find a way to stimulate crustin release in monodon, or even support crustin formation through amino acids int he diet, we could help fortify against vibrio.
    • Learning about crustin function could help develop broad-range antibiotics.
    • Maybe certain genetics favors crustin production and V. harveyi  resistance?

“Phage preparation FBL1 prevents Bacillus licheniformis biofilm, bacterium responsible for the mortality of the Pacific White Shrimp Litopenaeus vannamei” (Prada-Penaranda et al 2018)

Citation: Prada-Penaranda, C., Salazar, M., Guiza, L., Perez, M., Leidy, C., Vivez-Flores, M. (2018) “Phage preparation FBL1 prevents Bacillus licheniformis biofilm, bacterium responsible for the mortality of the Pacific White Shrimp Litopenaeus vannamei”. Aquaculture, 484, pp. 160-167.

Summary By: Alexandra Pounds

  • BIG PICTURE:Bacterial infections in L. vannamei that cause mass mortalities may become recurrent with biofilm development. Phage therapy reduced biofilm development of B. licheniformis in laboratory settings. Further testing in actual shrimp tanks is recommended. 
  • Importance: The shrimp industry is growing, but bacterial infections can wipe out hatcheries. Vibrio and AHPND are particularly aggressive. This researched looked at a case study in Colombia with Bacillus licheniformis, which wiped out over 70% of L. vannamei at the case study site. While Bacillus ssp. strains are usually found in probiotics, Bacillus licheniformis is an exception as it creates exotoxins. Furthermore, Bacillus licheniformis can form biofilms, which are colonies of bacteria stuck to surfaces using exopolysacharides excreted by the bacteria. Phage (types of viruses that attack bacteria) therapy has been shown to work as bacterialcides, and this study tested it’s effect for this site.
  • Methods:
    • B. licheniformis strain were isolated from L. vannamei, and compared against 5 other B. licheniformis strains and 5 other Bacillus ssp. strains. The strains were grown on agar plates. Biofilm was created using a lab-based system imitating a flow-through system.
    • Phages were isolated from freshwater and shrimp settlement pond samples, then grown in nutrient baths and agar plates to increase concentrations. They used TEM (a microscope that can make 3D images at microscopic detail) to determine the structure of the phages.
    • Phages were exposed to the biofilm at 0hr, 24hr, and 48hrs after bacterial inoculation. They also tried injecting phages over time instead of just one-off applications. After 68hrs, the biofilm was removed, dried, then weighed.
  • Results:
    • Significant differences were only found in the samples where biofilm was exposed to phages at 48 hours. This is probably because the phages killed dispersed cells, interrupting the reproductive stage. Before this, the biofilm may not have reached the reproductive stage yet.
    • Biofilms with injected phage over time had significantly slowed growth compared to the control.
  • Implications:
    • This study showed that biofilms of B. licheniformis strains can indeed form, which may be the cause of recurrent outbreaks and repeatedly high mortalities in L. vannamei tanks.
    • The phage developed in this study delayed and hindered biofilm formation.

“Production and economic assessment of giant kelp Macrocystis pyrifera cultivation for abalone feed in the south of Chile” (Correa et al 2016)

Citation: Correa, T., Gutierrez, A., Flores, R., Buschmann, A., Cornejo, P., and Bucarey, C. (2016). “Production and economic assessment of giant kelp Macrocystis pyrifera cultivation for abalone feed in the south of Chile“. Aquaculture Research, 47, pp. 698-707. DOI: 10.1111/are.12529

Summary By: Alexandra Pounds

Image Credit: Flickr

  • Big Picture: Farmed kelp for abalone feed in Chile has higher levels of protein. With 30 hectares of production at $78/tonne, the farm would be profitable and return investment within the first year.
  • Abalone farmers in Chile feed kelp to their stock, because other studies have show that it is a better food source for abalone growth. Unfortunately, wild kelp is only available seasonally. Kelp farming is a potential solution to the demand for kelp and prevent overharvesting wild kelp populations. This paper examines whether or not kelp farming in Chile is profitable.
  • Methods:
    • The researchers designed and installed a kelp farm off the coast of southern Chile. They started with 2.4 hectares for 2 years to establish whether the crop would survive the winter season. Afterwards, it was increased to 4 hectares.
    • The researchers used 2 trial units (one in summer, one in winter) to extrapolate annual expenses and yields for a bigger farm.
    • The farm relied on manual labor for picking and planting crop.
  • Results:
    • If the market price for kelp is $78/tonne, a return on investment can be made in the first year by harvesting 30 hectares. The farm would be profitable within one year.
    • Best profitability would be at 50 hectares per year.
    • Protein content of harvested kelp was 9%, which was significantly higher than wild kelp in the area.
    • The summer crop produced significantly greater biomass than the winter crop. Both crops together could produce about 41kg per meter of rope per year.
    • Production costs for 2 harvests (one year), of 10 hectares was $109,396.
      • Fixed costs = 13%
      • Variable costs = 87%
  • Implications
    • Kelp farming in southern Chile could be a profitable way to feed farmed abalone.
    • Placing kelp farms around Chilean salmon farms could increase yield due to higher nitrogen levels in the water. This would have the additional benefit of reducing environmental impacts of the salmon farms.
    • Current kelp prices are not high enough to support farms that produce less than 30 hectares.

“National Assessment Sheds Light on Educational Needs for Aquaculture in the United States” (Jensen et al 2016)

Citation: Jensen, G., Schwarz, M., Shumway, S., Trushenski, J., Curry Woods, L., Broyles, T., and Mayeaux, M. (2016). “National Assessment Sheds Light on Educational Needs for Aquaculture in the United States”. Fisheries, 41(8), pp. 467-469, DOI: 10.1080/03632415.2016.1199830.

Summary By: Alexandra Pounds

Image Credit: USDA.gov

  • Big Picture: Although demand for highly educated aquaculture workers in the US is increasing and student interest in higher education aquaculture programs is stable, higher education institutions are having trouble recruiting students and are not increasing the number of available programmes.
  • Aquaculture higher education in the US began in the 1970’s in response to the rise in aquaculture. Despite that the industry is growing, high education opportunities are decreasing, with programs shutting down. This study looked at the current aquaculture workforce and examined whether students were interested in pursuing a career in aquaculture to forecast the aquaculture workforce.
  • Methods: conducted a national survey to compile a list of aquaculture high education in the US.
  • Results:
    • 79 respondents,
      • 14 did not offer any courses related to aquaculture (others offered a combination of AA, BSc, MSc, PhD, and/or certificate)
      • 10 of which offered online aquaculture courses
    • Enrolment:
      • Enrolment increased from 2000-2010. Enrolment from 2010 – 2015 was stable.
      • Fewer international students are entering BSc programs. International and national PhD enrolments were equal.
      • Institutions reported challenges with recruiting students for aquaculture.
    • Course offerings:
      • A considerable number of institutions offer programs in aquaculture, many of which are smaller institutions. There have been no new programmes initiated since 2010.
      • Student interest in pursuing a degree in aquaculture seems stable.
      • Online course offerings are growing.
    • Respondents believe that there is a growing demand for employees with advance training in aquaculture.
    • Over the past 10-15 years, job listings in US aquaculture have decreased (especially in academia and government)
  • Implications:
    • The US may not have enough higher education programmes to supply the projected workforce requirements for US aquaculture.
    • The US aquaculture industry growth rate might be held back by the lack of a competent workforce (not enough educated workers).

 

“Strengthening the contribution of aquaculture to food and nutrition security: The potential of a vitamin A-rich, small fish in Bangladesh” (Fiedler et al 2016)

Citation: Fiedler, J., Lividini, K., Drummond, E., and Thilsted, S. (2016). “Strengthening the contribution of aquaculture to food and nutrition security: The potential of a vitamin A-rich, small fish in Bangladesh” Aquaculture, 452, pp. 291-303. DOI: 10.1016/j.aquaculture.2015.11.004

Summary By: Alexandra Pounds

Image Credit: Wikimedia Commons

  • Big Picture: The Mola Production Programme is the most cost-efficient way to address vitamin A deficiencies in Bangladesh.
  • Many small-scale farmers in Bangladesh culture fish, for both commercial and sustenance. Polyculture of rice and fish is an important part of food security in Bangladesh. Many Bangladeshis have small ponds available for aquaculture.
  • It is estimated that 60% of Bangladeshis are vit A deficient, despite the oil and wheat flour fortification programmes.
  • Mola carplet contains more vit A than other commonly eaten fish species in Bangladesh. Producing more mola carplet could help solve the vit a deficiency. The Mola Production Programme is currently behind these efforts. The aim of this paper was to do a cost-benefit analysis of increasing mola carplet production in Bangladesh to help solve the chronic vit A deficiency.
  • Methods:
    • Used national health statistics to establish the usual vit A intake, prevalence of deficiency, and years lost to deficiency-caused disability.
    • They then added how much vit A the Mola Production Programme would provide over the next 11 years to estimate future levels of vit A intake, prevelance of deficiency, and years lost to deficiency-caused disability. They assumed that the Mola Production Programme would have a 30% adoption rate
    • The change in these numbers was compared to the total cost of the Mola Production Programme.
    • They used two different scenarios for comparison.
  • Results:
    • Over 11 years the program would cost $23 million and
      • raise vit A levels by 7 micrograms
      • lower prevelance of deficiency by 1.1%
      • This equates to 3000 lives saved, and prevent 100,000 years lost to deficiency-caused disability.
  • Implications:
    • If continued for 20 years, the Mola Production Programme would have lower costs and greater health benefits than the Vitamin A wheat flour fortification programme.
    • Other nutritional components can be improved through the programme indirectly, via increased income with mola production.

“Increasing fish farm profitability through aquaculture best management practice training in Egypt” (Dickson et al 2016)

Citation: Dickson, M., Nasr-Allah, A., Kenawy, D., and Kruijssen, F. “Increasing fish farm profitability through aquaculture best management practice training in Egypt”. Aquaculture, 465, pp. 172-178. DOI: 10.1016/j.aquaculture.2016.09.015

Summary by: Alexandra Pounds

Image Credit: Wikimedia Commons

  • Big Picture: Fish farms in Egypt that adopt BMP are more profitable than those that don’t. Having BMP can increase the farm’s profitability, mostly due to better feed management practices.
  • Egyptian aquaculture is growing, but farmers had little training or education resources. Best Management Practices (BMP) training programmes were introduced to help. This survey examined whether or not implementing the BMP had resulted in greater profits and productivity.
  • While BMP are usually precursors to many certifications, farmers may see them as a burden rather than a help.
  • Aquaculture represents 77% of Egyptian fish production (mostly tilapia and mullet)
    • 85% = pond-based
    • 15% = cages, rice fields, and intensive farms
  • Key messages from BMP training:
    • reduce overall stocking rates to harvest more fish at larger sizes
    • fertilize the pond to stimulate plankton growth (an additional food source for fish)
    • reduce feed waste and use high-quality feed
  • Methods:
    • Farms that had implemented BMP were compared with farms that had not implemented BMP.
    • Data from 3715 farms were used, 70% of which were considered “high adopters” of BMP
    • An online questionnaire was distributed, and some farmers were interviewed.
  • Results:
    • BMP farms were more likely to practice mullet & tilapia polyculture rather than tilapia monoculture.
    • BMP training resulted in increased profitability, but had no effect on productivity. Average annual net profits were $15,000 greater in BMP farms than non-BMP farms.
    • BMP mostly improved feed and fertilizer management, which improved FCRs. BMP farms used less feed.
    • Operating costs were lower in BMP Farms.
    • There was no difference in total sales between BMP and non-BMP farms
    • BMP did not make a difference to total yield; however, farms with BMPs had larger average fish sizes.
    • BMP farmers were younger and had smaller families than non-BMP farmers (although this was not statistically significant). Statistically, the BMP farmer and non-BMP farmer demographics had no differences.
  • Limitations
    • There may have been some selection bias, as farmer interviews were selected based on connection with certain BMP trainers.