Chilled Seawater Research Articles

Evaluation of Freshness of Farmed Two-Year-Old Acipenser persicus during Storage in Ice

Chilled fish is considered a fresh product and helps to ensure the development of world trade. So, the present study aimed to investigate the freshness of two-year-old farmed A. persicus by chemical, microbial, sensory, and physical experiments, and determine its shelf life during ice storage. 20 fish samples were maintained in chilled seawater tanks for 12 days. The ratio of ice powder to fish is of 2 : 1. The fish were separated by layers of ice with a thickness of about 5 cm. The temperature was maintained throughout the storage period at 0-1°C. The fish had an average weight and length of 3.50 kg and 70 cm, respectively. Total bacterial counts, Staphylococcus, and Enterobacteriaceae were acceptable (6.78, 2.96, and 3.99 log CFU·g−1, respectively) for 10 days. Coliform, Escherichia coli, Pseudomonas aeruginosa, Vibrio parahaemolyticus, and Aeromonas hydrophila were not detected during storage. pH (6.89), peroxide value (4.32 meq O2 kg oil−1), thiobarbituric acid (0.96 mg·kg−1), free fatty acids (10.86 g 100 g−1), and total volatile nitrogen bases (19.83 mg 100 g−1) were normal during 10 days. Texture (2.56), odor (2.50), the appearance of gills (2.59), eyes (2.67), belly cavity (2.58), skin (2.49), and outer surface (2.90) of A. persicus displayed a decrease throughout storage ( p < 0.05 ). Sensory characteristics were acceptable for 10 days. Ash was 1.88–2.13% during storage ( p > 0.05 ). Unlike moisture (79.05–81.06%), fat and protein showed a decrease of 1.16−2.33 and 15.65–16.74%, respectively, during storage ( p < 0.05 ). According to the results of the present study, to maintain the economic value of sturgeon and for the expansion of their business, and to preserve the freshness of sturgeon during handling and the effect of freshness on the consumer’s opinion, it is recommended that fisheries use ice for sturgeon transport for 10 days.

A mosaic of phytoplankton responses across Patagonia, the southeast Pacific and the southwest Atlantic to ash deposition and trace metal release from the Calbuco volcanic eruption in 2015

Abstract. Following the eruption of the Calbuco volcano in April 2015, an extensive ash plume spread across northern Patagonia and into the southeast Pacific and southwest Atlantic oceans. Here, we report on field surveys conducted in the coastal region receiving the highest ash load following the eruption (Reloncaví Fjord). The fortuitous location of a long-term monitoring station in Reloncaví Fjord provided data to evaluate inshore phytoplankton bloom dynamics and carbonate chemistry during April–May 2015. Satellite-derived chlorophyll a measurements over the ocean regions affected by the ash plume in May 2015 were obtained to determine the spatial–temporal gradients in the offshore phytoplankton response to ash. Additionally, leaching experiments were performed to quantify the release from ash into solution of total alkalinity, trace elements (dissolved Fe, Mn, Pb, Co, Cu, Ni and Cd) and major ions (F−, Cl−, SO42-, NO3-, Li+, Na+, NH4+, K+, Mg2+ and Ca2+). Within Reloncaví Fjord, integrated peak diatom abundances during the May 2015 austral bloom were approximately 2–4 times higher than usual (up to 1.4 × 1011 cells m−2, integrated to 15 m depth), with the bloom intensity perhaps moderated due to high ash loadings in the 2 weeks following the eruption. Any mechanistic link between ash deposition and the Reloncaví diatom bloom can, however, only be speculated on due to the lack of data immediately preceding and following the eruption. In the offshore southeast Pacific, a short-duration phytoplankton bloom corresponded closely in space and time to the maximum observed ash plume, potentially in response to Fe fertilisation of a region where phytoplankton growth is typically Fe limited at this time of year. Conversely, no clear fertilisation on the same timescale was found in the area subject to an ash plume over the southwest Atlantic where the availability of fixed nitrogen is thought to limit phytoplankton growth. This was consistent with no significant release of fixed nitrogen (NOx or NH4) from Calbuco ash. In addition to the release of nanomolar concentrations of dissolved Fe from ash suspended in seawater, it was observed that low loadings (< 5 mg L−1) of ash were an unusually prolific source of Fe(II) into chilled seawater (up to 1.0 µmol Fe g−1), producing a pulse of Fe(II) typically released mainly during the first minute after addition to seawater. This release would not be detected (as Fe(II) or dissolved Fe) following standard leaching protocols at room temperature. A pulse of Fe(II) release upon addition of Calbuco ash to seawater made it an unusually efficient dissolved Fe source. The fraction of dissolved Fe released as Fe(II) from Calbuco ash (∼ 18 %–38 %) was roughly comparable to literature values for Fe released into seawater from aerosols collected over the Pacific Ocean following long-range atmospheric transport.

Optimising energy use in an existing commercial building: a case study of Australia\u2019s Reef HQ Aquarium

Reef HQ Aquarium is a major tourism attraction in tropical North Queensland, Australia. In 8 years, a 50% reduction in grid electricity was achieved through targeted infrastructure investment, whilst growing the business. Initially, grid energy consumption was 2438 MWh per annum, with 490-kW peak demand and energy intensity of 1625 MJ m−2 year−1 used on typical equipment such as HVAC (heating, ventilation and air conditioning), machinery, lighting and catering equipment. Savings of 13% were achieved in the first year by increasing indoor air temperature set-points by 1.5 °C with no significant costs or impacts on occupant thermal comfort or worker productivity. Peak demand was decreased by 46% by upgrading the computerised building management system (BMS), HVAC, machinery and lighting; and by installing a 206-kW photovoltaic (PV) solar power system. This case study illustrates that (a) significant energy use reductions are possible at low cost; (b) capital investment in energy-efficient infrastructure can have short payback times and high direct and indirect benefits, particularly where equipment is ending its life. This study is unique as it examines how a commercial building with integrated chilled water thermal energy storage (TES) and a 3.2-ML chilled seawater aquarium system can be controlled by a BMS to optimise solar power to manage peak energy demand and also increase the utilisation of generated PV power in the absence of electrical battery storage. An interesting building is used to demonstrate efficiency methods with elements such as HVAC and lighting which usually consume over half commercial buildings’ energy use.

Quantitative methods to measure pigmentation variation in farmed Giant Tiger Prawns, Penaeus monodon, and the effects of different harvest methods on cooked colour

Cooked prawn colour is known to be a driver of market price and a visual indicator of product quality for the consumer. Although there is a general understanding that colour variation exists in farmed prawns, there has been no attempt to quantify this variation or identify where this variation is most prevalent. The objectives of this study were threefold: firstly to compare three different quantitative methods to measure prawn colour or pigmentation, two different colorimeters and colour quantification from digital images. Secondly, to quantify the amount of pigmentation variation that exists in farmed prawns within ponds, across ponds and across farms. Lastly, to assess the effects of ice storage or freeze-thawing of raw product prior to cooking. Each method was able to detect quantitative differences in prawn colour, although conversion of image based quantification of prawn colour from RGB to Lab was unreliable. Considerable colour variation was observed between prawns from different ponds and different farms, and this variation potentially affects product value. Different post-harvest methods prior to cooking were also shown to have a profound detrimental effect on prawn colour. Both long periods of ice storage and freeze thawing of raw product were detrimental to prawn colour. However, ice storage immediately after cooking was shown to be beneficial to prawn colour. Results demonstrated that darker prawn colour was preserved by holding harvested prawns alive in chilled seawater, limiting the time between harvesting and cooking, and avoiding long periods of ice storage or freeze thawing of uncooked product.

Review: Weird Sea Creatures, by Erich Hoyt

This volume’s slimness is deceiving: the 64 pages of Weird Sea Creatures are rich in content and appeal. Erich Hoyt is a conservationist and cetacean researcher who has authored both adult and children’s books on cetaceans, whale watching, social insects, and deep-sea life; his extensive knowledge and interest in the life of the oceans is evident throughout the book. Intended for readers 10 and up, Weird Sea Creatures begins with a written introduction to the deep sea, followed by photographs of 50 deep-sea organisms, including blackdevil angler fish, piglet squid, deep-sea opossum shrimp, dragonish, sea urchins, brittle stars, and many more.Hoyt’s knowledge of and affection for his subject matter is evident throughout, starting with the author’s note in which he states that “I have come to know and sympathize with, even to love, all of the creatures in this book. Apologies are due for calling them ‘weird.’” The well-written introduction is a clear and concise description of deep-sea habitats and animal adaptations, followed by a description of how the photographs in the book were created: a challenge involving collecting the organism using nets or ROVs and photographing them against black backgrounds in chilled seawater aquaria below decks on the research vessel. The introduction is deceptively short. Only four pages, it provides brief but excellent descriptions of deep-sea conditions, currents, and animal adaptations such as echolocation, photophores, chromatophores, deep-sea predators, and the use of light in deep-sea animal communication. The photograph of each of the 50 animals that follow is accompanied by a paragraph of discussion. Adaptations to deep-sea existence are emphasized and explained, such as the huge eyes of the hatchet fish (that use any light available), “Dumbo” the octopod’s reddish coloring (which makes it invisible in the deep sea), and the bioluminescent escape mechanism of the mesopelagic copepods, among many others. The photographers – David Shale, Solvin Zankl, and Jeff Rotman – should be commended, as each image is exquisite, demanding that the reader slow to examine and savor the amazing adaptive details of each organism.Overall, Owls of the World is a very fine introduction to the wonders of deep-sea adaptations. Younger readers will find it a very useful overall reference or a wonderful nonfiction exploration of the dark world far below the waves. Even older readers will enjoy this slim text for the beauty of the photographs and the biological wonders of the animals presented.

Electrical stunning of farmed Atlantic codGadus morhuaL.: a comparison of an industrial and experimental method

An industrial and experimental electrical method for stunning farmed Atlantic cod in air and seawater (SW), respectively, were compared. The impacts of sedation with AQUI-S™ and exercise to exhaustion before electrical stunning were also assessed to monitor the possible depletion of rested muscle energy levels by electrical stunning. Stress (blood glucose, haematocrit, muscle pH, muscle excitability, high-energy phosphates and rigor mortis) and flesh quality (fillet texture, colour, liquid leakage (LL), gaping, residual blood and K-value) were assessed. For the industrial stunning method, an average of 41 V, 0.2 A dc was applied to individual cod for 18–27 s. For the SW method, a bipolar square wave current (170 Hz, 33% duty cycle) was applied for 5 s. After stunning, recovery was prevented by exsanguination in chilled SW. There were no differences (P>0.05) between the two stunning methods except for a higher ultimate fillet pH for cod stunned in air 8 days postmortem. Exercise before stunning depleted muscle energy levels at slaughter, increased LL and fillets had redder and darker flesh after storage on ice for 8 days. Electrical stunning (in air) of AQUI-S™-treated fish partly depleted muscle energy levels (pH 7.3, ATP 18.7 μmol g−1, PCr 70.1 μmol g−1). However, flesh quality was not affected. Unless pre-rigor filleting is the chosen processing strategy, electrical stunning of cod seems to be a promising stunning method.

Live chilling of turbot and subsequent effect on behaviour, muscle stiffness, muscle quality, blood gases and chemistry

AbstractDuring the commercial slaughter of farmed turbot(Scophthalmus maximus), a total of 67 fish were, on six occasions, removed from their rearing conditions at 14°C and put, as is standard commercial practice, into chilled seawater (-1.5 to -0.8°C) to monitor behavioural, muscular, osmoregulatory and respiratory responses during chilling time (90 min). Results show that a thermal insult alters the iso-osmotic balance, leading not only to an Na+influx and an intracellular release of Ca2+and K+, but also to a disturbance of respiratory function, leading to acidosis as a result of H+ and CO2accumulation, increased pCO2and reduced HCO3−in the blood. Once the internal temperature dropped below 1°C, the muscles contracted (cold shortening) and, although the fish were still alive, they reverted to a state of rigor, leading to a complete breakdown in their ability to move or ventilate and resembling an unconscious condition or death. Remarkably, the fish were able to prevent themselves undergoing hypoxia as pO2remained within acceptable limits. No changes in muscle pH were observed and, thus, no noted effects on textural properties. We conclude that live chilling from 14°C to approximately -1°C is a highly questionable practice. It causes physical and physiological changes that are generally associated with stress and, in the case of observed forced muscle contractions, could lead to severe pain. Furthermore, we conclude that cold shortening associated with chilling can be easily mistaken forrigor mortisand, as such, should be subject to further attention in future research on quality.

Timing and Duration of Larval Hatching for Blue King Crab Paralithodes Platypus Brandt, 1850 Held in the Laboratory

Abstract Female blue king crab, Paralithodes platypus, were captured from the Pribilof Islands, Alaska, in July and October 2003 and shipped to the Kodiak Fisheries Research Center. Crabs were held in chilled seawater at 2, 3.5, or 4°C until hatching, and final counts were 4, 6, and 10 crabs in each treatment, respectively. Mean size of all crabs was 123.9 mm CL and did not differ significantly between treatments. Individual crabs required an average of 29 days for complete hatching, regardless of holding temperature. Earliest hatching began on or before 20 February 2004. Crabs captured in July and held at 4°C hatched significantly earlier, with a mean hatch date of 13 March 2004, than crabs captured in October and held at 2°C or 3.5°C, both of which groups hatched on a mean date of 18 April 2004. Crabs released an average of 416 ml of larvae, and 110,033 first stage zoeae. Excluding two crabs for which complete volumes were not obtained, there were no differences in volume or number of larvae released by...

Texture, gaping and colour of fresh and frozen Atlantic salmon flesh as affected by pre-slaughter iso-eugenol or CO 2 anaesthesia

Farmed Atlantic salmon ( Salmo salar L.) were slaughtered at an average weight of 5.5 kg in May 2001 under either traditional CO 2 anaesthesia (denoted high stress) or a two-step iso-eugenol anaesthesia (denoted low stress) before being bled to death in chilled seawater. Product quality analyses were performed on fillets after 5 days on ice and on cutlets after 12 months of frozen storage (−25 °C). In ice-stored fillets, no differences in gaping were observed between the two anaesthetic protocols, but instrumental analyses revealed that the flesh of the salmon exposed to CO 2 sedation was softer and slightly redder (higher a*-value, 27.1±0.1, S.E. versus 26.4±0.1, p<0.0004) and more yellowish (higher b*-value, 22.6±0.1 versus 22.0±0.1, p<0.0001) than the salmon anaesthetised using iso-eugenol. Analyses of frozen–thawed cutlets confirmed the fresh fillet results in that salmon anaesthetised using iso-eugenol were firmer and paler (RocheSalmoFan™ score, 23.5±0.4 versus 24.4±0.3, p<0.05) than the salmon anaesthetised using CO 2. Furthermore, the frozen and thawed cutlets of iso-eugenol-anaesthetised salmon had a higher muscle pH (6.15±0.01 versus 5.98±0.03, p<0.05) and lower liquid loss (5.1±0.3 versus 7.1±0.3, p<0.05). Individual growth rate, final body weight (BW), final body length, condition factor (CF), sex, gonadosomatic index (GI) were also registered. No significant correlations ( p>0.15) between these growth and body conformation variables and gaping or fillet softness were detected. In conclusion, no differences were observed in fillet gaping between the two anaesthetic protocols, but the salmon anaesthetised using iso-eugenol were firmer, paler and had a higher water-holding capacity than salmon exposed to CO 2 anaesthesia.

Physiological Effects of Tricaine on the Supramedullary/Dorsal Neurons of the Cunner, Tautogolabrus adspersus

Ethyl-m-aminobenzoate, known as tricaine, metacaine, or MS222, is a commonly used general anesthetic for fish and amphibia. This anesthetic depresses neuronal activity in both the peripheral (1) and central nervous systems (2) of fish, but its effects on the basic physiological properties of individual neurons are unknown. Clearly, the action of tricaine must be determined, if neurophysiological data obtained during its use are to be correctly interpreted. We have therefore studied the effect of tricaine on the level of current necessary to elicit an action potential and spike height of supramedullary/dorsal neurons of the cunner Tautogolabrus adspersus (3, 4). Responses of supramedullary/dorsal cells to depolarizing current pulses were recorded from cunner, 8–13.9 cm in body length; the fish were either under general or local anesthesia. In the first condition (general anesthesia), eight fish were initially anesthetized in tricaine (300 mg/l, Sigma) in seawater with sodium bicarbonate (450 mg/l) added. When respiration ceased, the fish were transferred to an operating chamber where tricaine (100 mg/l) in chilled seawater with sodium bicarbonate (450 mg/l; pH 7.2) was recirculated through the mouth and over the gills for the duration of the experiment. In the second condition (local anesthesia), 10 fish were injected with pancuronium bromide (0.1 mg/kg; Sigma) to block neuromuscular transmission and were then placed in an operating chamber, where a respiratory current of chilled seawater was applied through the mouth and over the gills. Local anesthetic (20% benzocaine gel, Ultradent) was applied to the skin overlying the rostral spinal cord. After 5 min, the skin was removed and local anesthetic was applied to the underlying muscle. After 5 min, the rostral spinal cord was exposed. Single microelectrode recordings (3 M KCl filled, 5–15 M ) were then made from supramedullary/dorsal cell somata. Under general anesthesia, action potentials 77 8 mV (mean SD, n 12) in amplitude could be evoked by 7 2 nA of current. Under local anesthesia, spike height (91 6 mV, n 12) was significantly higher (P 0.001; unpaired t test) and the current needed to evoke the spike was significantly lower (3 2 nA; P 0.001; unpaired t test) than values obtained under general anesthesia. These changes occurred without significant shifts in resting membrane potential (general anesthesia 68 5 mV; local anesthesia 66 5 mV). Recordings were made in the supramedullary/dorsal cell soma, a location that is believed to be distant from the spike initiating zone (5). If the position of the microelectrode varied in its proximity to the spike initiating zone between experiments, then one might expect anesthetic-independent variation in spike height and current needed to elicit the spike. We controlled for this possibility in three experiments by continuously monitoring supramedullary/ dorsal cells without moving the microelectode while the levels of tricaine were changed. The spike height decreased and current needed to elicit the spike increased upon the addition of tricaine (100 mg/l) to the water (Fig. 1). When the tricaine was removed by running anesthetic-free seawater over the gills, the current needed returned close to pre-anesthetic levels, and the spike height began to recover. Supramedullary/dorsal cells are known to respond to touch (3, 6). Displacement of the tail usually resulted in the generation of

Particle retention and flow in the pharynx of the enteropneust worm Harrimania planktophilus: the filter-feeding pharynx may have evolved before the chordates.

An investigation of the feeding behavior of the acorn worm Harrimania planktophilus suggests a novel form of enteropneust feeding with significant phylogenetic implications. H. planktophilus is a holoinfaunal worm that feeds on deposited sediments, and filter feeds on suspended particles in interstitial pore water. To visualize the particle retention behavior involved in filter feeding, adult animals were held in chilled seawater under low light and fed food coloring and fluorescent particles. The behavior was recorded by videography. Most particles ingested were drawn into the mouth by an incurrent flow created by cilia on the pharyngeal bars and without the aid of mucus. Particles that passed freely through the gill pores averaged 3.04 microm, whereas particles retained in the gut and defecated in the feces averaged 13.9 microm. Food coloring entered the mouth and was pumped through the pharynx at a rate of 0.5-2.0 mm/s. There is no evidence of an endostyle or mucus-net capture mechanism in H. planktophilus, but instead particles are filtered and manipulated by a dense covering of cilia on the pharyngeal gill bars. This study suggests that the filter-feeding pharynx is not an innovation of the chordates, but evolved prior to the evolutionary divergence of the hemichordate-echinoderm clade from the chordates.

Optimization of aquaculture systems in Spain

An analysis of present heat production systems, using fossil fuel combustion, employed for sea water heating in Spanish hatcheries is given in this paper and compared to a technical solution based on the employment of a heat pump. Price per unit of produced energy is calculated for each system using liquid and gaseous fuels, and then these prices are compared to the price obtained for a heat pump. The heat pump system is also compared, from the point of view of its precision in maintaining temperatures, to the systems used at the present. A project prototype for thermal conditioning and temperature control in aquaculture rearing tanks is described. The waste heat of the return water is recovered: first, by a static recoverer and second, by a recoverer connected to the evaporator of a refrigeration unit. The system should be used in such a way that economic benefits are obtained from its two heat sources of the frigorific system in simultaneous production of warm and chilled sea water.

UNFLUENCE OF ANCHOVY QUALITY ON YIELD AND PRODUCTIVITY IN SALTING PLANTS

ABSTRACTSamples of whole anchovies (Engraulis anchoita) were stored immediately after capture under three different conditions: unrefrigerated in bulk, in boxes with ice or in containers with chilled sea water (CSW). The quality of the raw material and the differences resulting from the treatments were evaluated by sensory, chemical and bacteriological analysis. CSW gave the best results. The data showed the correlations existing between belly burst and other quality parameters which can be useful in the extablishment of quality indexes. Belly hurst was negatively correlated with productivity (R2= 0.876) and process yield (R2= 0.881) for anchovy salting plants. Variations in fish quality may lead to variations as great as 30% in production costs for fish salting plants.

PINK SALMON (ONCORHYNCHUS GORBUSCHA) QUALITY DURING ICE AND CHILLED SEAWATER STORAGE

ABSTRACTPink salmon were stored up to ten days in ice, chilled seawater (CSW), transferred from ice to CSW and from CSW to ice, and evaluated by chemical, physical, microbiological, and sensory methods. The sensory quality of CSW‐held fish declined at a faster rate than for iced fish. CSW‐held fish had higher weight gain, higher salt and hypoxanthine levels and had softer texture than iced fish. Microbial counts were highest for iced fish and a two‐log increase occurred during storage. Moraxella species were predominant in the microbial flora of iced fish whereas Pseudomonas species were predominant in the microbial flora of CSW‐held fish. Ice was superior to CSW for maintaining salmon quality.

Biochemical Characteristics of Tropical Fish Spoilage Bacteria Isolated from Indian Oil Sardine (Sardinella longiceps)

Biochemical characteristics of fish spoilage bacteria isolated from Indian oil sardine (Sardinella longiceps V alenciennes) stored in chilled sea water were studied to understand their role in spoilage of fish. Cultures of Vibrio spp. and Aeromonas spp. were biochemically very active, followed by Pseudomonas spp., Acinetobacter spp., Moraxella spp. and Flavabacterium spp. There was no significant change in the biochemical activities of cultures compared to the activity of the bacteria under aerobic conditions as in iced fish. However, under semianaerobic or microaerophillic conditions, these spoilage bacteria use trimethylamine oxide (TMAO) as an electron acceptor or as an oxidizing agent.

The prediction of mineral solubilities in natural waters: A chemical equilibrium model for the NaKCaMgClSO 4H 2O system at temperatures below 25°C

A low temperature thermochemical model for the system NaKCaMgClSO 4H 2O is presented. Aqueous species and standard chemical potentials of solid-solution reactions are modeled from published data for binary and ternary solutions. The temperature range below 25°C (to near −60°C) is emphasized, although the model parameters are fitted to merge smoothly with those of higher temperature models at temperatures between 25 and 100°C. Binary and ternary specific ion interaction terms vary independently with temperature and are modeled using freezing point depression and mineral solubility measurements. The standard chemical potential of the ice-water reaction is fitted independent of the model (from vapor pressure and free energy data). Remaining standard chemical potentials of solidsolution reactions are fitted along with the specific ion interaction terms. Model predictions are tested against published data for minerals formed and brine compositions obtained by chilling seawater to the eutectic (about −54°C). The model predicts the sequence of solid phases observed to precipitate from chilled seawater (mice-mirabilite-hydrohalite-sylvite-MgCl 2 · 12H 2Oantarcticite). For all but mirabilite model temperatures are within the uncertainty of the measured temperature. The compositions of brines predicted by the model also closely follow the observed compositions. The model allows accurate predictions of the freezing points of simple and complex solutions in the system. Low temperature phase equilibria and mineral solubilities may also be predicted. The model may be used to determine the composition of brines in fluid inclusions in the multicomponent system based on low temperature phase equilibria.

Refrigeration Energy Prediction for Flooded Tanks on Fishing Vessels

Calculations combined with documented experience predict and compare direct energy consumption for the two onboard flooded-tank refrigeration systems in current use. These are RSW (refrigerated seawater) which uses mechanical refrigeration, and CSW (chilled seawater) which uses ice brought from shore. RSW is found to consume energy at roughly half the rate predicted for CSW; seawater temperature has a major influence on results.

On‐board handling and quality changes during storage of fish predominant in Mexican shrimp by‐catch

SummaryAn important factor in the realization of the potential of shrimp by‐catch relates to how it can be easily and economically retrieved. This study deals with this problem and proposes a system of handling and storage of by‐catch fish at sea. Some fish representative of by‐catch from the Gulf of California were investigated for their storage qualities when held in crushed ice and chilled seawater (CSW). It was determined, using various chemical and physical parameters, that high quality was retained for fish held in ice and CSW for up to 14 and 10 days, respectively. Such storage periods are compatible with the average duration of shrimper voyages. Use of CSW appears a more appropriate method since storage and off‐loading would be less labour intensive than with iced storage and ice usage would be reduced. Incorporation of CSW tanks, taking into account existing shrimp boat designs, is proposed which would not affect present iced/frozen storage capacities.

Icelandic experience in storing fish in chilled seawater

Several species of eviscerated or ungutted fish have been the subject of storage trials in containers filled with chilled sea water (CSW), container capacities ranging from 600 to 40 000 l. A study was made of onboard conditions in a fishing vessel, in order to test the reaction of fishermen to this new technique. The internal temperatures of containers were recorded and the storage duration was assessed in terms of organoleptical, chemical (trimethylamine) and bacteriological parameters. In most of the experiments, the control samples were fish held in ice in 70 to 90 l plastic boxes; the results of experiments on storage durations have confirmed earlier results. Storage durations for fish held in CSW compare with those of ice storage, but in the case of onboard handling operations, container storage is easier and involves less labour. The relationship ice-water-fish comes out at 15-15-70. Ice can be stored onboard in insulated containers which can also be used to store fish on land prior to transformation. It will be necessary to convince fishermen of the technical advantages of this technique but, in any event, major alterations will have to be made to unloading constructions and installations before CSW container-storage can be generally accepted.

Treatments Affecting the Degradation of Lipids in Frozen Pacific Herring, Clupea harengus pallasi

Effects of various treatments on the development of peroxides and free fatty acids in frozen Pacific herring, Clupea harengus pallasi, are described. Fluctuating the frozen storage temperature from −28°C to −18°C (10% of total storage time) showed no significant effect. Temperature fluctuations from −28°C to −10°C produced a significant increase in peroxide value and free fatty acids following a prolonged storage period. Filleting of thawed herring and refreezing of fillets increased to a large degree the oxidative changes during the subsequent frozen storage. Dipping of fillets in 1.0% sodium erythorbate before refreezing was effective in controlling the development of peroxides. No difference was noted in the peroxide value of whole herring stored before freezing in chilled sea water agitated either by air or nitrogen. The use of carbon dioxide for extending the storage time of whole herring in chilled sea water has the potential danger of accelerating the oxidative changes during frozen storage.