9 results for Jeffs, AG

  • Elemental signatures in the shells of early juvenile green-lipped mussels (Perna canaliculus) and their potential use for larval tracking

    Dunphy, BJ; Millet, MA; Jeffs, AG (2011)

    Journal article
    The University of Auckland Library

    The seed for New Zealand's US$150 million green-lipped mussel (Perna canaliculus) aquaculture industry is almost entirely supplied by harvesting wild early juveniles (spat). The location of the broodstock populations producing these seed mussels is unknown because the larvae may have travelled N100 km before settling. Identifying these broodstock populations via larval tracking is critically important to assuring the sustainability of this mussel industry, yet larval tracking is not easily performed with currently available methods. However, deducing elemental signatures of juvenile shells via laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has the potential to identify the natal origins of P. canaliculus larvae, yet validation of the technique work must be performed for each species before this can be achieved. To this end, eleven elemental ratios were analysed for early juvenile P. canaliculus shells collected from six sites from the west coast of the Northland and Auckland regions of northern New Zealand. Of these 11 ratios, seven (Zn: Ca, Mn:Ca, B:Ca, Sr:Ca, Mg:Ca, Ba:Ca and Cu:Ca) exhibited sufficient spatial variation for discriminate function analyses (DFA) to assign the juvenile mussels back to their region and site of collection 63–100% of the time. However, among open coast sites DFA analyses were unable to distinguish between juvenile mussels taken from sites that were 11 km apart, revealing that there are limits in the resolving power of elemental signatures for P. canaliculus. Collections of early juveniles at one site (Maori Bay) at four different times over six months revealed temporal stability in elemental signatures, with early juveniles able to be correctly assigned to the collection location regardless of month of collection. Now that such information has been obtained we are better positioned to track dispersing P. canaliculus larvae via elemental signatures and ultimately locate the source wild broodstock populations currently supplying the majority of the spat for New Zealand's mussel industry.

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  • Revealing the natural diet of larvae of phyllosoma larvae of spiny lobster

    Jeffs, AG (2007)

    Journal article
    The University of Auckland Library

    An important bottleneck in the development of aquaculture of spiny lobsters is larval feeding and nutrition. Researchers have used a wide variety of natural foods and artificial food materials in attempts to improve the larval culture of these species. Unfortunately, very little is known about the natural feeding ecology and diet of spiny lobster larvae or phyllosomes. This paper reviews research undertaken in New Zealand over the past decade aimed at attempting to improve our understanding of the diet of spiny lobster phyllosomes.

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  • Identification of predators using a novel photographic tethering device

    Bassett, DK; Jeffs, AG; Montgomery, JC (2008)

    Journal article
    The University of Auckland Library

    Tethering prey is often used to help determine the impact of predators in aquatic communities. In this study, a novel photographic tethering device was used to make digital recordings of predation events on juveniles of the spiny lobster, Jasus edwardsii. Predation of lobsters was significantly higher during the day (76%) than at night (33.4%). This was consistent with a SCUBA survey that found greater numbers of diurnal predators than nocturnal predators at the study site. However, the abundance of predators was not consistent with the number of predation events for individual species as recorded by the photographic tethering device. The snapper, Pagrus auratus, was the most abundant species at the study site (45% of all diurnally active fishes), but was only responsible for 12% of predation events during the day. In contrast, wrasse species were responsible for the greatest number of predation events during the day (60%), yet made up only a small proportion of the diurnal fish population (25%). The results of this study indicate the importance of determining the identity of potential predators, through the use of a photographic tethering device, for increasing the value of results generated from tethering experiments.

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  • Specific dynamic action as an indicator of carbohydrate digestion in juvenile spiny lobsters, Jasus edwardsii

    Radford, Craig; Marsden, ID; Jeffs, AG (2008)

    Journal article
    The University of Auckland Library

    Commercial aquaculture of crustaceans depends on the development of artificial diets, the effectiveness of which is usually determined from captive growth experiments. As an alternative, this research examines the use of a physiological measure of energy expenditure, the specific dynamic action (SDA) using closed box respirometry to determine the potential of different carbohydrates for artificial diets for the spiny lobster Jasus edwardsii. Juvenile lobsters were provided with meals composed of glycogen, maltose, sucrose, glucose, or fructose in a gelatine base, or with gels of the algal carbohydrates, agar, alginate and carrageenan. Lobsters feeding on most of the general carbohydrate diets elicited a typical SDA response with an immediate rise in oxygen consumption, which was not exhibited in unfed controls. Lobsters fed algal carbohydrates did not show a SDA response but did show an increase in ammonia excretion. It is concluded that spiny lobsters are able to use carbohydrates as part of their diet and the SDA provides a useful means of rapidly determining which carbohydrates may be best used in formulated diets. It is suggested that the SDA would be a quick and effective way to determine food digestibility of components or ingredients used in crustacean aquaculture.

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  • Chemical cues promote settlement in larvae of the green-lipped mussel, Perna canaliculus

    Alfaro, AC; Copp, Brent; Appleton, DR; Kelly, S; Jeffs, AG (2006-08)

    Journal article
    The University of Auckland Library

    The large (70,000 tonnes) mussel aquaculture industry for the endemic New Zealand green-lipped mussel, Perna canaliculus Gmelin, currently relies almost entirely (80%) on wild caught seed that is often harvested attached to great quantities of floating algae. Natural vagaries in catches of wild mussel seed frequently result in shortages of mussel seed that, at times, have severely affected commercial aquaculture production. Both field and laboratory experiments were used to establish that chemical cues derived from algae significantly increase settlement of mussel larvae on artificial substrates. This is the first time an algal chemical cue has been implicated in the settlement behavior of P. canaliculus larvae. These results have potential commercial implications for improving mussel seed supply through inducing higher or more reliable levels of mussel settlement for aquaculture seed collection.

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  • Small-scale mussel settlement patterns within morphologically distinct substrata at Ninety Mile Beach, northern New Zealand

    Alfaro, AC; Jeffs, AG (2002)

    Journal article
    The University of Auckland Library

    Microscale settlement patterns of juveniles of the mussel Perna canaliculus were investigated within drift material at Ninety Mile Beach, northern New Zealand. Size- and site-specific selectivity on various morphologically distinct algal and hydroid species were identified within drift material and corroborated in laboratory experiments with similar artificial substrata. Mussel spat densities were greater within fine-branching natural (similar to28-57%) and artificial materials (similar to13-20%) compared to medium- and coarse-branching natural (similar to7-8%) and artificial (similar to2-3%) materials. Size-frequency distributions of mussel spat within natural and artificial materials suggested a relationship of increasing mussel size with decreased branching of substrata. Field and laboratory investigations indicated higher settlement of 1.5-2.0 mm mussel size classes in coarse-branching substrata, whereas fine-branching substrata had greater settlement of mussels within the 70 tonnes/year of this material is collected and supplied to the New Zealand aquaculture industry to seed mussel farms.

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  • Localised coastal habitats have distinct underwater sound signatures

    Radford, Craig; Stanley, Jenni; Tindle, CT; Montgomery, JC; Jeffs, AG (2010)

    Journal article
    The University of Auckland Library

    There is evidence that ambient underwater sound is used by some pelagic larval reef fishes and decapods as a guide to direct them toward coastal areas. It would be advantageous to these organisms if they were also able to use sound to remotely identify suitable settlement habitats. However, it is unknown whether different coastal habitats produce different sounds that would be capable of providing distinctive cues for larvae. This study identified marked differences in the characteristics of ambient underwater sound at 3 distinct types of coastal habitat: a macroalgal-dominated reef, a sea urchin-dominated reef, and a sandy beach, The sea urchin-dominated reef habitat produced sound that was significantly more intense overall in a biologically important frequency band (800 to 2500 Hz), compared with that from macroalgal-dominated reefs and beach habitats. The sound produced by snapping shrimp also exhibited marked differences among habitat types, with the sea urchin-dominated reef having significantly more snaps than the macroalgal-dominated reef or beach habitat. Many of the differences in the sound produced by the 2 reef habitats became more apparent at dusk compared with noon. This study provides evidence that there are significant differences in the spectral and temporal composition of ambient sound associated with different coastal habitat types over relatively short spatial scales. An acoustic cue that conveys both directional and habitat quality information that is transmitted considerable distances offshore would have the potential to be of immense value to the pelagic larval stage of a coastal organism attempting to remotely locate a suitable habitat in which to settle.

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  • Sound as an orientation cue for the pelagic larvae of reef fishes and decapod crustaceans

    Montgomery, JC; Jeffs, AG; Simpson, SD; Meekan, M; Tindle, CT (2006)

    Journal article
    The University of Auckland Library

    The pelagic life history phase of reef fishes and decapod crustaceans is complex, and the evolutionary drivers and ecological consequences of this life history strategy remain largely speculative. There is no doubt, however, that this life history phase is very significant in the demographics of reef populations. Here, we initially discuss the ecology and evolution of the pelagic life histories as a context to our review of the role of acoustics in the latter part of the pelagic phase as the larvae transit back onto a reef. Evidence is reviewed showing that larvae are actively involved in this transition. They are capable swimmers and can locate reefs from hundreds of metres if not kilometres away. Evidence also shows that sound is available as an orientation cue, and that fishes and crustaceans hear sound and orient to sound in a manner that is consistent with their use of sound to guide settlement onto reefs. Comparing particle motion sound strengths in the field (8 ?? 10???11 m at 5 km from a reef) with the measured behavioural and electrophysiological threshold of fishes of (3 ?? 10???11 m and 10 ?? 10???11, respectively) provides evidence that sound may be a useful orientation cue at a range of kilometres rather than hundreds of metres. These threshold levels are for adult fishes and we conclude that better data are needed for larval fishes and crustaceans at the time of settlement. Measurements of field strengths in the region of reefs and threshold levels are suitable for showing that sound could be used; however, field experiments are the only effective tool to demonstrate the actual use of underwater sound for orientation purposes. A diverse series of field experiments including light???trap catches enhanced by replayed reef sound, in situ observations of behaviour and sound???enhanced settlement rate on patch reefs collectively provide a compelling case that sound is used as an orientation and settlement cue for these late larval stages.

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  • Oxygen consumption and enzyme activity of the subtidal flat oyster (Ostrea chilensis) and intertidal Pacific oyster (Crassostrea gigas): responses to temperature and starvation

    Dunphy, Brendon; Wells, RMG; Jeffs, AG (2006-03)

    Journal article
    The University of Auckland Library

    Intertidal Pacific oysters (Crassostrea gigas) and subtidal flat oysters (Ostrea chilensis) were held at 10, 15, or 20 degrees C without food for 16 weeks. Rates of oxygen consumption in the subtidal oyster were more sensitive to temperature than those of the intertidal oyster, but temperature sensitivity decreased in starved Pacific oysters. Metabolic fuel reserves of glycogen in the adductor muscle were markedly higher in C. gigas, and decreased with starvation. Higher activities of the key metabolic enzymes, strombine dehydrogenase, alanopine dehydrogenase, and citrate synthase were found in C. gigas than in O. chilensis, indicating greater scope for energy production. These observations were consistent with the greater aerobic scope and glycolytic potential of C. gigas in the thermally variable intertidal environment, and in the face of severe nutritional challenge. Ostrea chilensis was metabolically challenged by warm temperatures and food deprivation, factors that need to be considered in the development of aquaculture methods or this species.

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