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Lambooij E.,Wageningen UR Livestock Research | Grimsbo E.,University of Bergen | de Vis J.W.v.,Wageningen UR IMARES | Reimert H.G.M.,Wageningen UR Livestock Research | And 2 more authors.
Aquaculture | Year: 2010

The overall objective of the study was to evaluate a percussive and an electrical stunning method under laboratory conditions in Atlantic salmon. Evidence of unconsciousness and insensibility of the salmon was provided on the electroencephalogram (EEG) by the appearance of slow waves and spikes, followed by a strong depression in electrical activity. This phenomenon was observed in 17 salmon after percussive stunning using an air pressure of 8.1 to 10 bars, whilst 8 fish were considered conscious at pressures below 8.1 bars although some were seemingly unconscious on behaviour. Consequences were a haemorrhage in the brain cavity in 15 out of 17 fish, broken upper or lower jaws in 9 fish and eye burst in 8 fish. A general epileptiform insult (unconscious and insensible) was obtained by delivering a voltage, consisting of a direct current (DC) coupled with 100 Hz alternating current (AC) with a peak value of ≈112 volt (V), head to body, for ≈ 0.5 s. The total duration of the insult was 62 ± 44 s (mean ± SD; n = 25) which was followed by minimal brain activity in 19 fish. The heart rate was 20 ± 7 beats/min prior to stunning. After stunning the electrocardiogram (ECG) revealed fibrillation for 22 ± 15 s and became irregular and showed extra systolae (ventrical contraction) afterwards. Exposing the salmon for 5 s with electricity followed by a gill cut resulted that 1 out of 3 fish recovered temporary after 3 min. Haemorrhages were not observed in the fillets. Average current for head to body electrical dry stunning was 668 milliampere (mA) root mean square (RMS) with an average stunning voltage of 107.9 Vrms. Electrical head to body stunning can be recommended when using coupled AC and DC current of 668 mArms and ≈ 107 Vrms. The salmon can be stunned in ≈ 0.5 s. However, a correct bleeding procedure should be developed. For percussive stunning we conclude that if sufficient force is used the fish will be rendered unconscious insensible which result in damage of the carcass, whereas a combined AC and DC can be recommended source for dry electrical head to body stunning. © 2009 Elsevier B.V. All rights reserved. Source

Erikson U.,Sintef | Lambooij B.,Wageningen UR Livestock Research | Digre H.,Sintef | Reimert H.G.M.,Wageningen UR Livestock Research | And 2 more authors.
Aquaculture | Year: 2012

Electrical stunning of farmed Atlantic cod is a method used to render the fish unconscious before further processing. However, evaluations of the stunning method at plants have shown that the electrical parameters need to be optimized to achieve instant stunning and prolonged duration of unconsciousness. One aim of the present study was to establish suitable stunning conditions for cod to comply with future fish welfare regulations. AQUI-S™ is an anaesthetic capable of producing rested fish at slaughter. In the current study, we wanted to assess some welfare aspects of using this agent. In addition, the two stunning methods were compared in terms of the magnitude of the stress response, and the resulting effect on product quality. The data show it was possible to stun cod instantly (0.5s) at 107 V rms, 0.5+0.2 A rms. However, it was necessary to expose the fish for a longer period (e.g. 15s) to the same voltage to prolong the period of unconsciousness to facilitate killing without recovery. AQUI-S™ (68mgL -1) rendered the fish unconscious without recovery. No noticeable avoidance behaviour or distress was observed during stunning. Blood pH, lactate levels, and blood drainage, as determined after recovery, were similar for both stunning methods. The ability of the white muscle to twitch was not affected by treatment although electrical stunning caused a drop in initial white muscle pH. Hence, a tendency for a more rapid onset of rigor mortis was observed. No detrimental effects on product quality (Quality Index scores, tendency for gaping, ultimate pH, and fillet texture) were observed for either stunning method. Moreover, no blood spots and discolourations of fillets, or spinal fractures were observed. To comply with both good fish welfare protocols, and at the same time ensuring good product quality, we have fundamentally shown that this is indeed possible when cod are stunned with either of the methods described here. © 2011 Elsevier B.V. Source

Lambooij E.,Wageningen UR Livestock Research | Digre H.,Sintef | Reimert H.G.M.,Wageningen UR Livestock Research | Aursand I.G.,Sintef | And 2 more authors.
Fisheries Research | Year: 2012

Cod and haddock captured with commercial trawling gear were taken immediately after landing on deck to on-board storage in dry bins for measuring brain and heart activity, and behaviour. Other groups were first stored in holding tanks and then electrically stunned with a prototype " dry stunner" For stunning 52V rms was applied on individual fish for 1s. As a result, the cod and haddock received an electrical current of 0.34±0.09 and 0.36±0.12A rms, respectively. Electrical activity in the brain and heart was measured before and after electrical stunning. The fish remained conscious for at least 2h after landing and during on-board storage as indicated by the electrical activity measured in brain and heart. Behavioural responsiveness to administered stimuli was absent in both species. After electrical stunning, both species showed a general epileptiform insult which was characterised by a tonic phase followed by a clonic phase and terminating with an exhaustion phase.Since the fish remained conscious after landing and storage, electrical stunning and subsequent killing with a throat cut, may provide an option for improving fish welfare on-board commercial fishing vessels. In particular, we recommend to stun and kill wild cod and haddock as soon as possible after landing on deck using a dry stunner applying 52V rms (coupled AC/DC current) for more than 3s. © 2012 Elsevier B.V. Source

Vermeulen T.,Wageningen UR Greenhouse Horticulture | Kamstra A.,Wageningen UR IMARES
Acta Horticulturae | Year: 2013

Aquaponics - the co-production of fish and plant products - is gaining interest both by entrepreneurs and researchers. This article evaluates both the technical setup as well as the economic potential of aquaponic systems and is aimed at identifying relevant knowledge questions for further improvements. Using system requirements for hydroponic systems and aquaculture, the aquaponic system was compared to a typical Dutch rockwool system. Aquaponics was found to be an improvement on current practices when using Deep Flow Technique (cultivation in a flowing thick water layer), resulting in better nutrient availability for the plants and re-use of nitrate. However, the technical challenges of the direct linkage between the two production systems in terms of needed technology and disease management was found to make the total system suboptimal when compared to conventional practices. The technological advantages of efficiency in use of land and energy and re-use of nutrients were found to be a marginal cost reduction of 1.2%. The article concludes that the added value of aquaponics can be found in the total business concept of producing in an urban environment with direct relationship with consumers. Further improvement of aquaponics can be found in improved disease management of the system - through management or improved design. Source

Slijkerman D.M.E.,Wageningen UR IMARES | Leon R.D.,Stinapa Bonaire | Vries P.D.,Wageningen UR IMARES
Marine Pollution Bulletin | Year: 2014

Bonaire is considered to harbor some of the best remaining coral reefs of the Caribbean, but faces multiple pressures including eutrophication. We measured multiple water quality indicators twice annually, from November 2011 to May 2013, at 11 locations at the west coast of Bonaire. This study resulted in 834 data points. DIN concentrations ranged from below quantification to 2.69. μmol/l, phosphate from below quantification to 0.16. μmol/l, and chlorophyll-a from 0.02 to 0.42. μg/l. Several indicators showed signs of eutrophication, with spatial and temporal effects. At southern and urban locations threshold levels of nitrogen were exceeded. This can be a result of brine leaching into sea from salt works and outflow of sewage water. Chlorophyll-a showed an increase in time, and phosphorus seemed to show a similar trend. These eutrophication indicators are likely to exceed threshold levels in near future if the observed trend continues. This is a cause for concern and action. © 2014 Elsevier Ltd. Source

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