Via a series of experiments, larval and juvenile lobsters have been fed natural and formulated diets to test which stimulate the highest growth rates and yield the best survival.
Through manipulating the content of these diets, and by incorporating supplemental biotics and pigments into their development, the hatchery has been able to improve the feeds we use in lobster culture, and even identify the biological mechanisms underpinning these results. This research is now due to be taken to a new level with an assessment of the feeding habits of juvenile lobsters on-grown in submerged containers at sea, which will give us the best indication yet as to what these animals feed on in the wild.
2014-2015 Karen Middlemiss – University of Exeter, MRes Thesis. Combined effects of UV irradiation, ozonation and the probiotic Bacillus spp. on growth, survival and general fitness of European lobster (Homarus gammarus).
Middlemiss KL, Daniels CL, Urbina MA, Wilson RW. (2015) Combined effects of UV irradiation, ozonation and the probiotic Bacillus spp. On growth, survival and general fitness of European lobster (Homarus gammarus). Aquaculture. 444; 99-107.
Bacterial pathogens are a leading cause of disease in hatchery aquaculture systems and preventative methods such as use of probiotics as feed supplements and water additives are well documented. However, comparisons between the effectiveness of using probiotic water additives over traditional biocontrol methods are less understood. This study assessed the combined effects of ultraviolet (UV) irradiation, O3 (ozone) and Bacillus spp. as a water additive (probiotic), in the culture of European lobster (Homarus gammarus) in a semi-closed recirculation system. Larvae were categorised as zoea stages I–III, megalopa (stage IV) and juvenile (stage V) onwards. Stage I larvae were assigned to one of six treatment groups consisting of 1) O3, 2) probiotic, 3) probiotic + O3, 4) probiotic+O3+UV, 5) O3+UV, or 6) probiotic+UV, for 18 days. During stages I–V, growth was measured on 1, 6, 11, 18, 24, and 31 dph (days post hatch), and survival was measured on 1, 18, 24 and 31 dph. Bacterial counts of pathogenic Vibrio spp. in culture water were measured at 1, 4, 9, 14, and 18 dph. Lobsters were also exposed to a physiological fitness test (low salinity challenge) at stage IV, 7 days post treatment. Results showed that O3 is comparatively more beneficial than probiotic with increased LWG (live weight gain) in the O3 treatment over probiotic between stage IV and V (N5 mg). Survival rates were ~10% higher in the O3 treatment group than probiotic treatment group on day 18, then ~5% and ~4% higher on days 24 and 31. Lobster biomass on day 18 was ~60% higher in the O3 treatment than probiotic treatment and 116% higher on day 31. Total Vibrio spp. present in the O3 treatment was 0.05% of the total in the probiotic treated culture water (day 18). Results between UV treatment groups showed significantly lower numbers of Vibrio spp. present in probiotic + O3 + UV culture water 4 dph than O3 + UV (~10 fold higher) or UV + probiotic (~15 fold higher) and by day 18 probiotic+O3+UVwas significantly higher thanO3+UV(~8 fold higher). Osmoregulatory challenge test resulted in no significant differences in physiological fitness between any treatment groups. The present study shows the effectiveness of O3 in aquaculture facilities for control of pathogens in the rearing of European lobster over either a probiotic water additive (at 3.75 × 107 CFUs L−1) or UV irradiation.
2014-2015: Grace Dugdale – Cardiff University, BSc industrial placement. ‘Incorporation of probiotics (Bacillus spp.) in formulated larval and juvenile Homarus gammarus feeds.’
Global demand for seafood has led to increased aquaculture over recent years, but issues such as disease control and efficiency of animal growth have emerged as production has moved to commercial scales. To test the performance of feeds for successful rearing of juvenile European lobsters (Homarus gammarus) in recirculation systems, we evaluated the use of probiotic-supplemented formulated diets at varying culture stages. Three larval diets (LC, LD1 and LD2) and three juvenile diets (JC, JD1, JD2) were trialedtrialled in a total of nine treatment combinations. Survival, growth (as weight, W, and carapace length, CL), and moult frequency were measured 1, 6, 11, 21 and 55 days post hatch (dph). Survival and growth were measured during juvenile stages on 21 and 55 dph. No significant differences were apparent between the survival or moult frequency of lobsters at either larval or juvenile stages. However, W and CL after the first moult were significantly greater among larvae fed on LD1 and LD2 compared to those fed LC, and lobsters fed LD2:JD2 showed significantly greater W and CL than both LD1:JC and LD1:JD1 fed lobsters. Overall, the concentration of dietary probiotics for optimum growth was much higher in juvenile diets than larval diets.
2014-15: Fiona Mallows – Cardiff University, BSc industrial placement. ‘The effect of a seawater-administered probiotic (Bacillus spp.) on growth and survival in cultured European lobster (Homarus gammarus) larvae.’
Probiotics have previously shown benefits to hatchery culture of lobsters when included as a direct nutritional supplement, by displacing potentially pathogenic microbes in the lobster’s digestive tract. We trialled the effects of probiotics (Bacillus spp.), on bacterial colonisation and the growth and survival of larval lobsters, when administered directly into culture waters. Larval survival (assessed 18 days post-hatch) was higher among clutches experiencing prolonged exposure to probiotics than those experiencing either brief probiotic or no probiotic exposure, although these differences were not found to be statistically significant. Neither growth nor the quantity of Vibrio sp. bacteria were different between treatments after 18 days, although probiotic exposure did show significant inverse correlation with Vibrio sp. loading after 9 days. Detrimental nitrite loadings in culture systems also correlated with probiotic dose, which may have inhibited the development of clearer differences in growth and survival between larval treatments. Probioitcs continue to show potential for use as an ethical alternative to antibiotics to prevent disease in semi-intensive hatchery culture systems, although direct application to seawater was arguably less successful than previous applications incorporating Bacillus spp. into larval diets.
2009-2011: Carly Daniels – PhD studentship, Plymouth University. ‘Optimisation of the rearing diets for early life stages of the European lobster, Homarus gammarus, to enhance growth, survival and health using biotic dietary supplements.’
Research funded by The Great Western Research Fund, The National Lobster Hatchery, The Worshipful Company of Fishmongers and Plymouth University in collaboration with the University of Exeter.
Video & Abstract
To satisfy global requirements for seafood there is a demand for the intensive culture of aquatic species which puts pressure on the industry to increase production. This intensive nature of aquaculture often results in problems including the spread of diseases, which leads to reductions in culture success. With environmental concerns over the development of disease resistance, the use of chemotherapeutic substances such as antibiotics employed to combat disease is under tight legislation. The industry must therefore find suitable alternatives to antibiotics in order to combat disease; prophylactic biotics are such an alternative. Probiotics and Prebiotics have shown potential to enhance disease resistance by immune stimulation and thus increase survival; they have also been shown to improve growth by augmenting changes in gastrointestinal (GI) morphology and microbiology. This review aims to describe the rationale behind the use of prophylactic biotic substances in aquaculture, outlining the research performed to date and the development of the products, focusing specifically on crustacea. Supplementation of biotics through either the culture environment or the diet has proven to enhance growth and survival in many crustacean species including shrimp (Rengpipat et al., 1998; Rengpipat et al., 2003; Vaseeharan and Ramasamy, 2003; Villamil et al., 2003; Wang et al., 2005; Wang, 2007; Liu et al., 2009; Zhou et al., 2009a), prawn (Decamp and Moriarty, 2007; Genc et al., 2007; Decamp et al., 2008) and lobster (Daniels et al., 2007). The incorporation of biotic supplements in European lobster Homarus gammarus culture is in its infancy. Though, there is increasing pressure to support the sustainability of this commercially valuable species through culture practices. Thus investigations of potential biotic application at all life stages of H. gammarus can provide insight into how morphological and biochemical changes may improve crustacean culture success.
Daniels CL, Merrifield DL, Boothroyd DP, Davies SJ, Factor JR, Arnold KE. (2010) Effect of dietary Bacillus spp. and mannan oligosaccharides (MOS) on European lobster (Homarus gammarus L.) larvae growth performance, gut morphology and gut microbiota. Aquaculture. 304 (1); 49-57.
The effect of dietary application of a commercial probiotic (Bacillus spp.) and mannan oligosaccharides (MOS), used singularly and combined, on the survival, growth performance and feed cost-benefit of larval Homarus gammarus was assessed. Un-supplemented Artemia (control) or Artemia enriched with probiotics (100 mg l−1Bacillus spp.), MOS (12 mg l−1) or probiotics + MOS (100 mg l−1Bacillus spp. + 12 mg l−1 MOS) was fed to four replicate groups of zoeal I lobsters for 30 days. Carapace length and weight of five H. gammarus from each replicate was recorded on 1, 3, 9, 13, 18 days post hatch (dph) and for post-larval condition at 18 dph. Additionally, moulting success was recorded from 14 to 30 dph with survival calculated at 30 dph. Morphological analysis of the posterior intestine was also conducted on larval and post-larval H. gammarus using light and electron microscopy. In a secondary experiment the effects on gut microbiota were assessed using both culture-dependent and culture-independent methods. After 18 dph, larval H. gammarus fed a diet containing Bacillus spp + MOS had significantly (P < 0.01) improved weight gain, carapace length, weight to carapace length ratio, specific growth rate (SGR), food conversion ratio (FCR) and post-larval condition, compared to all other groups. The individual supplementation of either Bacillus or MOS also significantly improved growth parameters, survival and post-larval condition compared to the control group, but to a lesser extent. Survival of all groups was significantly (P < 0.01) elevated after 30 days compared to the control group. Light microscopy demonstrated no significant increases in gut absorptive surface area in larvae or post-larvae receiving biotic supplemented diets. However, electron microscopy revealed significant increases in microvilli length and density in larval and post-larval H. gammarus fed biotic supplemented diets compared to the control group (P < 0.05). Culture-based analysis of gut microbiota demonstrated probiotic Bacillus spp. colonisation in Bacillus and Bacillus + MOS fed larvae. Denaturing gradient gel electrophoresis of PCR-amplified 16S rRNA revealed that microbial species richness and diversity was reduced in Bacillus + MOS fed post-larval lobsters. Subsequently the microbial profiles of Bacillus + MOS were the most dissimilar to the control group. Improvements seen in the present study appear to be an amalgamation of effects highlighted with the individual use of Bacillus and MOS, and so are probably additive rather than synergistic in nature.
Daniels CL, Merrifield DL, Ringø E, Davies SJ. (2013) Probiotic, prebiotic and synbiotic applications for the improvement of larval European lobster (Homarus gammarus) culture. Aquaculture. 416; 396-406.
The effects of dietary applications of a commercial probiotic (Bacillus spp.) and prebiotic (mannan oligosaccharides [MOS]), used singularly and combined (i.e. synbiotic), on larval survival, growth, intestinal microbial communities and stress resistance of larval European lobster, Homarus gammarus, were assessed. Larvae were reared in green water culture for 12 days from hatch until metamorphosis to zoea III. Un-supplemented Artemia nauplii (control) or Artemia nauplii enriched with probiotics (Bacillus spp. 100 mg l− 1), prebiotic (MOS 12 mg l− 1) or synbiotics (100 mg l− 1Bacillus spp. + MOS 12 mg l− 1) were each fed to 3 replicate groups of zoea I lobsters for 12 days. The effects on gut microbiota were assessed using culture-dependent methods at 1, 7 and 12 days post-hatch (dph) and PCR-DGGE at 1 and 12 dph. PCR-DGGE was also used to assess microbial communities of the live feeds. Carapace length and weight of five H. gammarus from each replicate was recorded on 1, 7, and 12 dph and survival to zoea III was recorded. A low salinity stress test was used as a measure of organism fitness at day 12. After 12 dph, H. gammarus larvae fed experimental treatments had significantly (P < 0.02) improved weight, carapace length and weight gain, compared to larvae fed control treatments. Survival to 12 dph was elevated by all treatments and was significantly (P < 0.001) increased for the Bacillus and MOS fed larvae. Salinity stress tolerance was greatest in larvae fed Bacillus although all experimental treatments produced enhanced tolerance to salinity stress in comparison to larvae fed control treatment. Culture-dependent analysis of the gut microbiota of larval lobsters demonstrated the colonisation of Bacillus spp. in larvae fed probiotic or synbiotic enriched live feeds. There was also a reduction in Vibrio levels in certain biotic fed larvae and live feed treatments. PCR-DGGE revealed that the number of observed taxonomical units (OTUs), species richness and species diversity increased in zoea III lobsters fed probiotic, prebiotic and synbiotic. Subsequently, the microbial profiles were dissimilar to the control group with the synbiotic group showing the greatest dissimilarity to the control (36.54 ± 2.54%). The similarity between bacterial communities associated with Artemia and zoea III larvae was highest in the Bacillus treatments (53.86%). The present study demonstrates the benefit of applying dietary supplementation of Bacillus, MOS and Bacillus + MOS on the GI microbiota of lobster larvae which subsequently improved growth performance and stress tolerance.
2008: Benjamin Bourdon – Année Universitaire, MSc thesis. ‘Use of prebiotics and probiotics in culturing larval European lobsters (Homarus gammarus).’
The effects of dietary Bio-Mos® and/or Sanolife® on growth performances, survival rate and quality of postlarvae after metamorphosis, of Homarus gammarus were investigated for the larval period. Different diets of probiotic (Sanolife®) and/or prebiotic (Bio-Mos®) were tested in four replicates. Control, Diet 1 (including Sanolife®), Diet 2 (including Bio-Mos®), Diet 3 (including Sanolife® + Bio-Mos®).Lobster larvae showed 1.85 ± 0.18, 2.21 ± 0.11, 2.29 ± 0.09, 2.86 ± 0.11% specific growth rate, 1.36 ± 0.72, 5.69 ± 1.26, 5.84 ± 1.54, 7.99 ± 1.01% survival and 90.00 ± 5.77, 70.00 ± 5.77, 60.00 ± 0.00, 20.00 ± 8.16% abnormality, respectively. At the end of the study, generally enhanced growth performances and feed conversion ratio were observed in larvae fed on Diet 3 (Bio-Mos® + Sanolife®) with the highest final live weight (0.033 ± 0.001g) and survival rate (7.99 ± 1.01%) after 18 days of feeding. The benefit-cost analysis showed similar patterns of cost-effectiveness between Diet 2 and Diet 3. In conclusion, synergestic positive effects have been observed on growth performances, survival rate and quality of postlarvae using prebiotic and probiotic together. Synbiotic, despite is slightly higher price, should be used as a healthy growth promoter in lobster larvae diets.
2006-2007: Carly Daniels. ‘Developing the use of Bio-Mos® in larval lobster culture’, and ‘Understanding the use of Bio-Mos® in larval lobster culture.’
Independent research projects funded by the Cornwall Research Fund through European Social Fund (ESF), supported by the National Lobster Hatchery and backed by Plymouth University and Alltech.
2004: Carly Daniels – Plymouth University, BSc dissertation. ‘Preliminary use of Bio-Mos® in larval lobster culture’.
2017: Jessica Haigh – The University of Plymouth, MSc Dissertation “Optimising a dry diet and feeding regime for European lobster (Homarus gammarus, L.) larvae.”
The effect of different dry feeds, particle sizes and feeding regimes on growth, survival and gut histology of European lobster (Homarus gammarus) larvae was assessed. Frozen pre-packaged plankton were used as a control and dry diets were formulated and used as experimental feeds. The first trial tested three diet formulations, differing in protein and lipid content, against the control with each group fed ca. 10% of body weight in feed twice a day. There was a significant difference in larvae weight on day 7 between the experimental and control diets, whereby larvae from all experimental diet groups had a significantly higher weight than those in the control group. However, there were no other significant differences in larvae weight or carapace length (CL) for any other day in the feeding trial. The second trial used three different particle sizes and the frozen control diet. Significant differences were found in larvae weight and CL on days 5 to 11 whereby larvae in the control diet group consistently had a lower weight or smaller CL than those in the experimental groups. The third trial used the best diet but varied feeding frequency between each group with all groups fed a total of ca. 10% body weight each day. Differences in weight and/or CL were detected on days 3 to 14, with larvae in the highest feeding frequency group having the significantly lowest larval performance in terms of growth, on almost all sample days. Overall, larvae in the formulated diet groups were very comparable to those in the control group and on some sample days exhibited increased growth. Survival was increased in trial 1 by the formulated diets, however there was no significant difference for trial 2, suggesting other variables may impact survival rates. With lower costs, better storage practicalities and quality consistency associated with dry feeds and the positive outcome of the feeding trials, this study highlights the potential to switch from live or frozen feeds to dry, artificial diets when rearing H. gammarus larvae.
2014-2015: Grace McNicholas – The University of Exeter, BSc dissertation. ‘Comparative analysis of formulated pellets with various levels of binder inclusions on growth and colouration of post-larval juvenile European lobsters, Homarus gammarus.’
As global dependence on aquaculture as an alternative source of protein increases, optimising the production of farmed animals is essential. However, reduced growth and potential losses of natural colouration are associated with high levels of nutrient leaching in artificial feed pellets. Although, binders can be added to reduce pellet breakdown, optimal inclusion rates may differ between species. The effect of three diets containing different percentages of binder on post-larval juvenile Homarus gammarus growth and colouration was investigated. Diet was found to have no effect on carapace length, weight to carapace length ratio, or red and blue hue colour change; however, diet did affect weight and green hue colour change. Future studies should consider conducting stability trials to determine if differences could be attributed to nutrient leaching.
2014: Sophie Franks – Cardiff University, BSc industrial placement. ‘Assessing diets for use in larval European lobster (Homarus gammarus) culture.’
The National Lobster Hatchery (NLH), Padstow, Cornwall was set up to rear larval lobsters under hatchery conditions and release them around the Cornish coast as a method of stock enhancement. It is important that cultured lobster juveniles are as large and healthy as possible to increase their chances of survival once released. Diet is highly influential upon the growth rate and survival of lobster larvae during their first planktonic life-stages, therefore it is important to provide them with a feed that supplies essential nutrients. This study trialled the use of preserved feeds and formulated feeds as an alternative to the expensive and time consuming live Artemia sp. that have been previously widely used for larval lobster culture. Various preserved copepods and formulated diets were tested for their effect upon growth rate and survival of lobster larvae until stage IV. Combinations of these diets were also investigated to determine whether a mixture could have greater positive influences. In a separate trial the use of green water (algal) conditioner was also considered in terms of reducing the amount of cannibalism within communal larval systems. Formulated feeds were successful, although larval survival was markedly improved when used in combination with preserved feeds. No significant differences in growth were observed between treatments. Green water conditioner had no effect upon growth or survival of larvae. Further research is required to develop suitable formulated feeds that could be based on specific dietary requirements of larval lobsters.
2014: Anna Davies – The University of Exeter, BSc thesis. ‘Assessing the dietary use of algae derived carotenoids in the European lobster (Homarus gammarus) during post larval development.’
Historic overfishing of coastal lobster populations has led to a decline of lobster numbers in coastal areas across the globe. This thesis examines if incorporating a higher level of Astaxanthin-containing algae into the diet of captively reared Homarus gammarus improves their chance of survival. Lobster (n=54) were equally and randomly distributed among three dietary treatment groups with various algal inclusion. The lobster were then weighed and measured at a number of intervals over a 4-month period. Lobsters fed the lowest algal inclusion diet gained the most weight and grow the largest compared to both the higher algal inclusion groups. However, mortality rates were higher within the lowest inclusion group compared to the other higher groups, though this pattern was not significant.
2012: Lewis Cocks (Awarded the Lord Harris Scholarship) – Plymouth University, MSc thesis. ‘Developing a formulated pellet diet for juvenile European lobster (Homarus gammarus): Effects of variable cod liver oil concentrations on survival development and fatty acid status.’
The trial took place within the National lobster hatchery, Cornwall, UK, where Juvenile Homarus gammarus lobsters (450) were separated into three different raceways containing three replicas, with each replica containing 50 individuals. Lobsters were fed diets with variable concentration of cod liver oil (CLO). Diet A with low inclusion CLO, diet B with medium inclusion CLO and diet c with high inclusion CLO. Diet B provided higher weight gain, carapace length gain, weight to carapace length ratio, survival and moult frequency. Diet B also had the least deaths through failure of ecydsis (stuck in moult). Statistical analysis proved the results as significant (significance was accepted at P ≥ 0.05). Results also showed that diet C with the highest dietary lipid level and the highest inclusion of CLO, supressed the growth of the lobsters and had the lowest survival (61.48%), as well as the higher moult death syndrome percentage (12.16%). But this was only expressed in the latter half of the trial (>36 days). Results suggest that higher dietary lipid levels and/or high amounts of CLO can cause suppression in growth and survival.
2011: Tom Bunce (Awarded the Lord Harris Scholarship) – The University of Exeter, BSc thesis. ‘Effects of dietary astaxanthin on survival, growth and oxidative stress of the European lobster (Homarus gammarus) during postlarval development: a life history perspective’
Many biological processes compete for finite resources, often resulting in trade-offs between damage accumulation and repair. Growth is modulated by a balance between harmful reactive oxygen, normal by-products of oxidative metabolism, and antioxidant defence. Dietary-derived antioxidants play an important role in antioxidant systems, and can reduce oxidative damage incurred during periods of rapid growth and complex physiological development. Early nutrition may therefore have both short-term and long-term consequences for antioxidant defences. To investigate this Juvenile lobsters (Homarus gammarus) were fed with formulated diets supplemented with astaxanthin at two concentrations. Survival, growth and oxidative damage in postlarval lobsters were measured. Lobsters fed a high astaxanthin diet were able to invest a higher amount of resources to enhance survival and growth, whilst incurring no additional oxidative cost. These results suggest that oxidative stress is a key mediator in the trade-off between growth and self-maintenance during early stages of development, and that antioxidant systems may be limited by the availability of antioxidants within the environment. This study demonstrates that carotenoid provisioning can increase survival and growth by alleviating oxidative stress in a crustacean.
2011: Ben Jennings – Plymouth University, BSc dissertation. ‘Bio-energetics and nutrition for the European lobster.’
The dietary and energetic demands of the European juvenile lobster, Homarus gammarus were determined through a 54 day bio- energetic growth trial. Feeding frequency was varied between four groups to determine whether feeding rate effected growth and basal metabolism. Oxygen consumptions were measured periodically using a closed respirometry technique. Feeding rations were varied and the highest feeding rate and quantities produced significantly higher growth rates than the lowest rations.
2010: Emma Watkinson (Awarded the Lord Harris Scholarship) – Plymouth University, MSc thesis. ‘Development of marine based formulated diets for juvenile lobster Homarus gammarus – focus on protein inclusion.’
The effect of four diets with varying protein sources and percentages on the survival and growth performance of juvenile Homarus gammarus was assessed. Carapace length and weight were measured every two weeks. Survival was recorded everyday throughout the experiment. All diets were readily accepted and consumed. The lobsters fed diets containing protein sources from polychaete worms had a lower survival and growth rate, suggesting a negative impact through the intake of heavy metals and in particular arsenic. This has implications on the formation of a complete commercial lobster diet using alternative sources of protein.