Letteratura scientifica selezionata sul tema "Macruronus novaezelandiae"

The first record of the straptail fish, genus Macruronus, from South Africa was based on a single specimen captured off the Atlantic Cape coast and described as a new species, M. capensis Davies 1950. Davies did not examine specimens of the other extant nominal species in the genus, but based his conclusions solely on references to the original descriptions of M. novaezelandiae (Hector 1870) and M. magellanicus Lönnberg 1907. We show that all of the characters used by Davies (1950) to distinguish M. capensis from its congeners are in fact shared by the other nominal species of this genus. We also present molecular evidence from a Macruronus specimen recently caught off South Africa to support the conclusion that M. capensis is a junior synonym of M. novaezelandiae.

Otoliths from blue grenadier (Macruronus novaezelandiae), which had been aged previously by annuli analysis, were analysed for the naturally occurring radionuclides 210Pb and 226Ra in an attempt to independently verify their age. However, the radiometric technique could not be applied to determine age because the results showed that 226Ra was not incorporated at a constant rate throughout the life of M. novaezelandiae. Uptake of 226Ra was greater in juveniles than in adult fish. This was probably due to the juvenile phase inhabiting inshore/estuarine waters.

The diet and feeding ecology of the demersal merlucciid M. novaezelandiae from three areas of the upper continental slope (420-550 m) of south-eastern Australia are described. The food consists almost entirely of mesopelagic fauna. The major prey are myctophid fish Lampanyctodes hectoris, other fishes, natant decapods, euphausiids and squid. Energy values of major prey items were determined by bomb calorimetry. Although euphausiids occur frequently in the diet, fish make up 90% of the energy intake. There is little regional variation. M. novaezelandiae undertakes diel vertical migrations that are similar to those of its prey, bringing it within 50 m of the surface at night. There is a seasonal trend towards cannibalism by adults on juveniles.

Identification of volatile flavour compounds of hoki (Macruronus novaezelandiae) and orange roughy (Hoplostethus atlanticus) oils has been carried out. Flavour compounds were extracted by a purging system and collected using a porous polymer Tenax TA trap. The gas chromatography-mass spectrometry (GC-MS) was used to identify the volatile flavour compounds. The predominant compounds contributing to the volatile flavour of hoki oil were methyl ethyl benzoate, ethyl benzoate and 1,1-dimethylethyl-2-propionic acid. Meanwhile, the main volatile flavour components of orange roughy oil were toluene, cyclohexane, 1,1-dimethylethyl-2-methyl propionic acid and tetrachloroethane.

Lipases from two New Zealand commercial fish species, Chinook salmon (Oncorhynchus tshawytscha) and New Zealand hoki (Macruronus novaezelandiae) were investigated. The lipases were extracted from the pyloric ceca and purified by affinity chromatography and gel filtration. Calcium ions and sodium cholate were absolutely necessary both for lipase stability in a polyacrylamide gel and for optimum activity against p-nitrophenol esters. Both fish lipases had a pI value of 5.8 ± 0.1, were most active at 35°C, were thermally labile, had a pH optimum of 8-8.5, were more acid stable compared to other fish lipases studied to date, and showed good stability in several water-immiscible solvents. The salmon enzyme was an overall better catalyst for the hydrolysis of p-nitrophenyl caprate based on its higher turnover number and lower activation energy for the hydrolysis reaction. Based on their chemical and catalytic properties, the salmon and hoki enzymes were classified as carboxyl ester lipases. Chinook salmon and hoki lipases were then evaluated as flavour modifying agents in dairy products. Cream was either incubated with the fish lipases or two commercially available lipases used in dairy flavour development. The fish enzymes were more similar to calf pregastric esterase in terms of the total amount and types of fatty acids released (mainly short chain) over the course of the reaction. The highest specificity was towards the key dairy product flavour and odour compounds, butanoic and hexanoic acids. Immobilization of the salmon lipase was then carried out on two hydrophobic supports. Salmon lipase immobilized on octyl-Sepharose had 40- and 10-fold higher activity (on a dry weight basis) against a tributyrin emulsion than the same lipase immobilized on Lewatit VP OC 1600 and a microbial lipase immobilized on Lewatit (Novozym 435), respectively. Salmon lipase-octyl-Sepharose was highly active against both ghee and fish oil emulsions, but salmon lipase-Lewatit and Novozym 435 had very low activities against the fish oil emulsion.The potential for flavour enhancement in dairy products with both fish lipases was demonstrated based on the free fatty acid composition and sensory characteristics of lipase-treated creams. In addition, the immobilized salmon lipase showed potential for low temperature modifications of emulsified lipids.
Les lipases de deux espèces de poissons commerciaux en Nouvelle-Zélande, le saumon quinnat (Oncorhynchus tshawytscha) et le hoki de la Nouvelle-Zélande (Macruronus novaezelandiae) ont été étudiées. Les lipases ont été extraites des caeca pyloriques et purifiées par chromatographie d'affinité et gel filtration. Les ions de calcium et cholate de sodium étaient absolument nécessaires pour la stabilité de la lipase dans un gel de polyacrylamide et de l'activité optimale contre les esters p-nitrophénol. Les deux lipases de poissons avaient une valeur pI de 5.8 ± 0.1, ont été les plus actives à 35°C, ont été thermolabiles, a un pH optimum de 8 à 8.5, ont été plus stables en milieu acide par rapport à d'autres lipases de poissons étudiées à ce jour, et ont montré une bonne stabilité dans plusieurs solvants miscibles à l'eau. L'enzyme du saumon a été un catalyseur globalement meilleure pour l'hydrolyse de caprate p-nitrophényl en fonction de son nombre de rotation élevé et faible énergie d'activation pour la réaction d'hydrolyse. Sur la base de leurs propriétés chimiques et catalytiques, les enzymes de saumon et hoki ont été classées comme des lipases ester carboxylique. Les lipases du saumon quinnat et hoki ont été aussi évaluées comme agents de modification de la saveur dans les produits laitiers. La crème a été mise à incuber avec les lipases de poisson ou avec deux lipases disponibles dans le commerce utilisées dans le développement du goût des produits laitiers. Les enzymes de poissons avaient plus des similitude avec l'estérase prégastrique du veau en termes de montant total et les types d'acides gras libérés (principalement à chaîne courte) au cours de la réaction. La plus grande spécificité a été observée aux composés clés de la saveur et odeurs des produits laitiers: les acides butanoïque et hexanoïque. L'Immobilisation de la lipase de saumon a ensuite été effectuée sur deux supports hydrophobes. La lipase de saumon immobilisée sur octyl-Sépharose avait une activité 40- et 10-fois plus élevée (sur la base du poids sec) par rapport à une émulsion de tributyrine que la même lipase immobilisée sur Lewatit VP OC 1600 et une lipase microbienne immobilisée sur Lewatit (Novozym 435), respectivement. La lipase-octyl-Sépharose de saumon a été très active à la fois contre le ghee et les émulsions d'huile de poisson, mais la lipase-Lewatit et Novozym 435 de saumon avaient des activités très faible contre l'émulsion d'huile de poisson. Le potentiel d'amélioration de la saveur dans les produits laitiers avec les deux lipases de poisson a été démontré sur la base de la composition des acides gras libres et les caractéristiques sensorielles des crèmes traitées avec lipases. De plus, la lipase de saumon immobilisée a démontré un potentiel pour des modifications au niveau des lipides émulsionnés à basse température.

Westland petrels Procellaria westlandica breed only near Punakaiki on the West Coast of New Zealand. About 80 km offshore from their breeding colony, New Zealand's largest commercial fishery (for hoki Macruronus novaezelandiae) operates from mid June to early September, coinciding with the Westland petrel's breeding season. It has been assumed that Westland petrels feed extensively on fisheries waste and that this habit has been at least partly responsible for the increase in the Westland petrel population. Some seabird biologists have expressed concern that if a species comes to depend on scavenging at fishing vessels, such a species could experience a food crisis if fishing operations changed in a way that reduced the quantity of waste discharged. The aim of this research was to assess how dependent Westland petrels have become on fisheries waste for food. Diet studies showed that during the hoki fishing season, waste accounts for more than half by weight of the solid food Westland petrels bring back to the colony to feed their chicks. After the hoki season, waste contributes only about a quarter of their diet as birds switch to more natural prey and scavenge a wider variety of fish species presumably from smaller, inshore fishing vessels. Much of the fisheries waste eaten by Westland petrels was flesh which could not be identified using traditional techniques. The electrophoretic technique iso-electric focusing increased the number of fish samples that could be identified and consequently the diet was interpreted differently than it would have been had only traditional diet analysis been used. The survey of Westland petrel distribution off the west coast of the South Island, found that although hoki fishing vessels influence the distribution of Westland petrels, only a small proportion of the Westland petrel population appears to utilise this food resource at any one time. Westland petrels were tracked at sea by VHF radio telemetry and then by satellite tracking. Satellite tracking showed that there is considerable variation in the amount of time Westland petrels spend in the vicinity of fishing vessels. On average, satellite tracked birds spent one third of their time near vessels, but they foraged over much larger areas than that occupied by the West Coast South Island hoki fishing fleet. Although fisheries waste is an important component of the Westland petrel diet, it appears that the situation is one of opportunistic use of a readily available resource, rather than one of dependence. Several features of the Westland petrel's breeding biology and foraging ecology suggest that Westland petrels could compensate for a reduction in waste from the hoki fishery by switching to other sources of waste and increasing their consumption of natural prey. Nevertheless, much remains unanswered concerning the role of fisheries waste in the Westland petrel's diet. In particular, quantifying the waste available to seabirds, and the success of Westland petrels in acquiring that waste compared to other scavenging species, is needed in order to better predict the effect of a reduction in fisheries waste on Westland petrel population size.

Westland petrels Procellaria westlandica breed only near Punakaiki on the West Coast of New Zealand. About 80 km offshore from their breeding colony, New Zealand's largest commercial fishery (for hoki Macruronus novaezelandiae) operates from mid June to early September, coinciding with the Westland petrel's breeding season. It has been assumed that Westland petrels feed extensively on fisheries waste and that this habit has been at least partly responsible for the increase in the Westland petrel population. Some seabird biologists have expressed concern that if a species comes to depend on scavenging at fishing vessels, such a species could experience a food crisis if fishing operations changed in a way that reduced the quantity of waste discharged. The aim of this research was to assess how dependent Westland petrels have become on fisheries waste for food. Diet studies showed that during the hoki fishing season, waste accounts for more than half by weight of the solid food Westland petrels bring back to the colony to feed their chicks. After the hoki season, waste contributes only about a quarter of their diet as birds switch to more natural prey and scavenge a wider variety of fish species presumably from smaller, inshore fishing vessels. Much of the fisheries waste eaten by Westland petrels was flesh which could not be identified using traditional techniques. The electrophoretic technique iso-electric focusing increased the number of fish samples that could be identified and consequently the diet was interpreted differently than it would have been had only traditional diet analysis been used. The survey of Westland petrel distribution off the west coast of the South Island, found that although hoki fishing vessels influence the distribution of Westland petrels, only a small proportion of the Westland petrel population appears to utilise this food resource at any one time. Westland petrels were tracked at sea by VHF radio telemetry and then by satellite tracking. Satellite tracking showed that there is considerable variation in the amount of time Westland petrels spend in the vicinity of fishing vessels. On average, satellite tracked birds spent one third of their time near vessels, but they foraged over much larger areas than that occupied by the West Coast South Island hoki fishing fleet. Although fisheries waste is an important component of the Westland petrel diet, it appears that the situation is one of opportunistic use of a readily available resource, rather than one of dependence. Several features of the Westland petrel's breeding biology and foraging ecology suggest that Westland petrels could compensate for a reduction in waste from the hoki fishery by switching to other sources of waste and increasing their consumption of natural prey. Nevertheless, much remains unanswered concerning the role of fisheries waste in the Westland petrel's diet. In particular, quantifying the waste available to seabirds, and the success of Westland petrels in acquiring that waste compared to other scavenging species, is needed in order to better predict the effect of a reduction in fisheries waste on Westland petrel population size.