Via the treatment of seawater and diets used in our recirculation aquaculture systems we have improved the growth, health and survival of lobsters during their vulnerable early lifestages.
The launch of our Lobster Cultivator project now gives us an opportunity to develop understanding of the effects of water chemistry, egg health and feed quality on the production of post-larval lobsters. We have built on early trials of juvenile lobster cultivation in submerged containers in the sea to pioneer a semi-intensive approach to mariculture on-growing, while also rigorously testing of the design of container rearing systems through our Lobster Grower projects. Through these complimentary research schemes we aim to stabilise and advance the production of juvenile lobsters, allowing us to increase the number and quality of released animals, and so improve our contribution to the sustainability of the lobster fishery
2010: Jake Scolding – ‘Determining the optimal use of chemicals in the disinfection of live feeds and the use of ozone in the culture of the European lobster, Homarus gammarus, at the National Lobster Hatchery.’
Developing disinfection protocols for larvae and juvenile lobsters. Research fed into the operating practices of the LobsterPlant, Norway, created to develop automated technology for large scale land based production of juveniles market sized lobsters. Independent research sub-contracted by University of Swansea, as part of Framework 7 project, incorporating eight other European partners.
Scolding JWS, Powell A, Boothroyd DP, Shields RJ. (2012). The effect of ozonation on the survival, growth and microbiology of the European lobster (Homarus gammarus). Aquaculture. 364; 217-223.
The fishery for the European lobster, Homarus gammarus has declined in recent years and has subsequently impacted on local socio-economics and ecology at wider scales. This has led to the formation of hatcheries (restocking wild populations with juveniles) and more recently, an interest in land based farms (ongrowing of juveniles to an edible size for direct consumption). To optimise the success of lobster rearing, ozone was investigated as a sustainable, scalable antibacterial treatment to assist water quality management and hence survival of captive lobsters at larval and post larval (PL) stages. Larval lobsters were exposed to constant ozone at a candidate concentration (400 mV, ca. 15 ppb) in a number of replicate upwelling hopper systems in five repeated experiments. At intermediate sampling points during larval rearing, ozone treatment resulted in significantly enhanced survival while Vibrio sp. bacterial load was significantly reduced in ozone treated larvae and culture water compared to controls. However, larval length and weight declined towards the end of the five repeated 18 day trials, potentially due to the effects of ozone on water chemistry and hence larval nutrition and physiology. To understand if ozonation had longer term effects on PL after metamorphosis, groups of ozonated and unozonated larval recruits were placed in separate control and constantly ozonated raceways to create four treatments. Ozone did not reduce growth rate in PL exposed to ozone at any life stage. With both “double” treatments, survival was similar and approximately average considering all four treatments, was elevated in lobsters ozonated as PL only and reduced in lobsters ozonated as larvae only.
Ozone (O3) is a powerful oxidant that has been used in both the aquaculture and water treatment industries to improve water quality and reduce pathogens during pre-treatment, treatment of effluent, as a continual treatment during RAS operations, and for bivalve depuration. As ozone can be toxic to aquatic organisms, the technology has also been investigated to destroy invasive or nuisance species, and other research has also highlighted negative effects of residual ozone on water courses. Ozone and ozone-produced oxidants used in aquaculture operations have therefore typically been removed from water prior to entry into tanks holding stock animals. However, a growing body of research has identified direct application of ozone, here defined as exposure of residual ozone and ozone-produced oxidants to cultured species of finfish, shellfish and live feeds across various life stages. This approach appears to be increasingly employed as a beneficial technology due to proven enhancement of hygiene and water quality, provided dosages or concentrations are appropriate to maintain animal health and welfare. This review paper concentrates on the observed benefits and drawbacks of direct ozonation, influencing factors and future considerations for standardisation and uptake of the technology.
2007: Nicola Wilson – Plymouth University, MSc thesis. ‘The effect of intermittent disinfectant (Chloramine-T) exposure on growth, oxygen uptake and gill morphology of larval lobsters, Homarus gammarus.’
Chloramine-T is used in lobster hatcheries to control epidemia in larval systems. Information on the toxicity of chloramine-T to the European Lobster (Homarus gammarus) is sparse. Most research has been conducted in fin fish aquaculture, specifically to control bacterial gill disease (BGD). This study investigated the toxicity and sub-lethal effects of chloramine-T on Homarus gammarus larvae. Growth rates were assessed as a proxy for metabolic activity and oxygen uptake to determine gill dysfunction using a closed bottle respirometer technique. The 96 h LC50 of a daily 60 min chloramine-T exposure is 170mg 1-1. Homarus gammarus appear to be less sensitive to chloramine-T toxicity than Rainbow Trout (Oncorhynchus mykiss) or Atlantic Salmon (Salmo salar). Intermittent chloramine-T exposure up to 60 mg 1-1 did not significantly affect oxygen uptake or growth rates up to stage III. Observation of gills under scanning electron microscope (SEM) showed reduced algae coverage with chloramine-T exposure but limited effectiveness on other pathogens colonising the gills. Unidentified black spots were observed on some gill filaments. These may be chloride cells coming to the surface at the epithelium either induced by chloramine-T or due to age. Further work needs to be conducted to fully identify these effects. From this study, commercially used chloramine-T at 20 mg 1-1 is considered beneficial in controlling epidemia in lobster hatcheries with little pathological significance.
Halswell P, Daniels CL, Johanning L. (2018) Framework for evaluating external and internal parameters associated with Sea Based Container Culture (SBCC): Towards understanding rearing success in European lobsters (Homarus gammarus). Aquaculture Engineering. In Press.
Sea Based Container Culture (SBCC) is a mariculture technique that relies on the natural maintenance of environmental conditions, such as Dissolved Oxygen (DO) concentration and feed availability. This paper discusses a framework to evaluate the rearing success of European Lobsters (Homarus gammarus) in SBCC based on temporal and spatial variations of external parameters, including current velocity, wave velocity, turbulent fluctuations and dissolved oxygen concentrations. The temporal variations considered annual changes to the environment and the effect of biofouling growth, and the spatial variations considered the geographical location (case study of Falmouth bay, Cornwall) and vertical position in the water column. The internal parameters of the containers were modelled using transfer functions derived from previous experimental data. The internal parameters were compared to rearing limitations selected from available literature, which included foraging and mobility behaviours, and DO consumption. The time that internal parameters exceeded the rearing limitations was quantified, allowing rearing success to be predicted.
This paper uses a case study of external parameters measured in Cornish waters, UK, to demonstrate the framework methodology. The framework showed that in situ measurements of current, wave and turbulence could be used to predict the internal parameters of SBCC containers, which can be used to predict theoretical rearing success based on rearing limitations. The framework indicated that DO concentrations within the containers should not affect rearing success; however, the foraging and mobility limits were exceeded by 0 to 30 % of the time (depending on vertical position in the water column and assessment method). The paper aims to demonstrate the generic framework methodology and understands its limitations in predicting rearing success. The framework provides a tool to optimise the SBCC design for spatial and temporal varying conditions related to a geographical location or (vice versa) identify suitable mariculture sites based on SBCC design and environmental conditions. Additionally, the framework can optimise the vertical position of the SBCC in the water column and identify, from parameters considered, those that are most likely to affect rearing success.
Halswell P, Daniels CL, Johanning L. (2016) Sea-based container culture (SBCC) hydrodynamic design assessment for European lobsters (Homarus gammarus). Aquacultural Engineering. 74; 157-173.
The presented work describes the hydrodynamic assessment studies of a much needed technical innovation of Sea Based Container Culture (SBCC) as part of a semi-intensive, passive aquaculture culture system for farming the European lobster (Homarus gammarus). Factors that are known to influence growth and survival rates were obtained from previous literature, including flow rate, wave energy and motion characteristics; these factors defined performance criteria for SBCC containers.
The internal flow velocities and external flow patterns for different SBCC container designs were measured and used to inform design decisions. Suitable graphical representations have been developed to assess SBCC containers on specific performance criteria. Oyster SBCC containers were found to provide stable motion characteristics but perform poorly against the lower velocity limit, indicating insufficient supply of Dissolved Oxygen (DO) to allow for optimal growth of European lobsters. Internal flow velocities were also measured on un-fouled and fouled SBCC containers; results showed SBCC 2 would not provide enough DO with 66% biofouling coverage (66% biofouling replicates one year deployment) and triggered a redesign. SBCC 1 at 90° yaw angle of attack demonstrated all round good performance against upper and lower velocity limits and motion characteristics; thus showed greatest promise for cultivation of European Lobster.
2016: Hannah Pihama – Aberystwyth University, BSc project. ‘Assessing optimum stages of deployment for hatchery-reared European lobsters (Homarus gammarus) in Sea Based Container Culture (SBCC).’
The National Lobster Hatchery (NLH), Padstow, is carrying out a three year research project (Lobster Grower 2) observing the growth of lobsters in Sea Based Container Culture (SBCC), this study was executed as part of this project. The primary aim of this study is to determine the optimum stage to deploy postlarval lobsters into SBCC to achieve the highest survival. Additionally, this study aims to create a key to determine between postlarval stages 4-6 without need for expert determination. The juveniles were cultured in the NLH and two groups; a control (stage 4) and test group (stage 6) were deployed on three lines into two types of container, oyster basket and novel design. These containers were checked after 6 and 12 weeks to determine survival in the containers and the growth of individuals that persisted. Of the two groups, the test group had a larger survival than the control group. Of the two container types, the oyster baskets showed a larger survival than the novel design (though this was due to escape related issues and not necessarily container per se). To determine between three postlarval stages (4-6) for this study, three photos were taken of a random selection of individuals known to be between each desired stage. These were measured using Image J to determine if a ratio between carapace width and abdomen width differed between each stage. There was a significant difference between life stages and this study concludes that deployment was most effective at a specific life stage. Staging ratios have been determined but will need further work to determine whether they are accurate.
2012: Betheney Wills – The University of Exeter, MSc thesis. ‘On-growing Stage 5 European lobsters (Homarus gammarus) in sea containers (South Cornwall, UK).’
2011: Emily Miles – The University of Exeter, MSc thesis. ‘Cage culture development of post larval lobsters (Homarus gammarus L.) in the UK.’
Daniels CL, Wills B, Ruiz-Perez M, Miles E, Wilson RW, Boothroyd D. (2015) Development of sea based container culture for rearing European lobster (Homarus gammarus) around South West England. Aquaculture. 448; 186-195.
This three year field investigation consisted of three discrete experiments, examining six potential sites for rearing the European lobster (Homarus gammarus) around the Cornish coast (U.K.). Sea-based container culture (SBCC) systems were deployed, varying site, year, depth, shelter and pre-fouling, to test effects on growth and survival of juvenile H. gammarus. Site and depth were examined between May–August 2011 at two sites off the South coast. One estuarine (River Fal: RF) and one sea-based (St. Austell Bay: SA) site were assessed with containers suspended at either 2 or 8 m depth. Greatest survival was found at the SA site (56%) compared to RF (25%), with the greatest growth (specific growth rate: SGR 3%, live weight gain: LWG 0.4 g and carapace length gain: CLG 4.5 mm) also achieved at SA. Depth did not affect juvenile development. Between May and August 2012, one estuarine (Fowey: F) and two sea-based (SA and St. Mawes: SM) sites on the south coast were selected to assess the effect of site and shelter. SM showed the highest survival (93%). Growth and survival were not affected by the presence of a shelter. From August to December 2013, three sites off the north and south coasts were selected to assess the effect of site, depth, pre-fouling and feed availability. Sea-based (Port Quin Bay: PQ, Wave Hub: WH and SA) sites were assessed, with containers submerged at either 3 or 10 m above the sea bed (PQ 7–14 m, WH 42–49 m depth at chart datum). Survival did not significantly differ between sites (61–86%), but growth at the PQ site (LWG 0.7 g; carapace length gain: CLG 6.1 mm) was significantly greater than at all other sites (LWG 0.3–0.4 g; CLG 2.5–3.6 mm). Depth did not affect juvenile development. Pre-fouling reduced growth at all sites. Feed availability varied between sites with PQ showing the greatest taxonomical units. Variations between years were also shown between 2011 and 2013 at the SA site. SBCC systems show potential for culturing H. gammarus juveniles compared to hatchery controls (survival ≤ 46%), acting as a transition step between hatchery rearing and release for stocking purposes. The importance of site selection and between year variations is highlighted as important factors to consider for larger scale assessment of aquaculture potential.
2016-ongoing: Adam Bates – ‘Lobster Cultivator: the effects of seawater chemistry, egg health and feed quality on the production of post-larval lobsters.’
Funded by the Worshipful Company of Fishmongers and The Waterloo Foundation.
2016-ongoing: Corey Holt – CEFAS and University of Exeter PhD research, carried out in conjunction with the Lobster Grower 2 project. ‘Gut health in European lobsters: the gut microbiome as a health marker for offshore sea container culture.’
Funded by BBSRC and CEFAS.
2014-2015: Adam Bates – The University of Exeter postgraduate research. ‘Development rates of larval Homarus gammarus in light and in dark culture systems’
Funded by CEFAS and the University of Exeter.
AbstractEuropean lobsters Homarus gammarus develop as planktonic larvae after hatching. This study investigates whether rates of larval growth or development are enhanced in darkened conditions. To eliminate inter-brood competition, and provide additional experimental replication, three separate broods under two treatments, the analysis demonstrates a significant reduction in weight gain, growth in carapace-length and progression through zoeal-stages under dark conditions, however survival rates between light and dark conditions were not found to be significantly different.