354 research outputs found
Aspects of biology and control of exotic invasive Caulerpa spp. in Aotearoa - New Zealand
No full textExotic invasive species, such as some species of macroalgae in the genus Caulerpa, can pose a significant threat to marine biodiversity and ecosystem functioning. Invasive Caulerpa species typically exhibit physiological resilience, rapid growth, chemical defences, and the ability to propagate via fragmentation and sexual reproduction, enabling them to readily colonize new environments. Invasions by exotic Caulerpa spp. in many parts of the world have led to widespread ecological degradation, including biodiversity loss, alteration of endemic natural habitats, and the disruption of trophic links. In Aotearoa - New Zealand, C. brachypus and C. parvifolia were first detected in 2021 in highly localised areas in the northeast of the country. Their subsequent rapid spread across the Hauraki Gulf and Bay of Islands triggered intensive biosecurity responses. Several control methods have been tested, with varying success and ecological trade-offs. The current research begins to explore the potential of fragmentation to contribute to the spread of these Caulerpa species by assessing the viability and growth of excised fragments. The research also evaluates the potential of exposure of the Caulerpa to heated seawater (i.e., thermal shock) as a novel method for killing Caulerpa species. Small fragments (2 - 20 mm in length) of C. brachypus and C. parvifolia mostly remained viable (i.e., 72%) over four weeks, with most of these showing new growth of rhizoids, i.e., 93.4%. Fragments as small as 2 mm in length were found to be capable of growing new components that would provide them with the potential to establish on the seafloor. In the laboratory, exposure to thermal shock treatments of 45 °C for 30 seconds or longer, or 50 °C for 5 seconds or longer kills C. brachypus fragments. In the field, segments of C. brachypus exposed to thermal shock treatments of 50, 60, and 70 °C for 30 seconds resulted in a significant loss of C. brachypus cover (p < 0.05), but not complete elimination. Overall, this study provides valuable new insights into fragment viability and a potential new method for controlling invasive Caulerpa that can contribute toward managing and protecting Aotearoa - New Zealand’s unique marine ecosystems
Particle retention and selection by the spat of the green-lipped mussel, Perna canaliculus
No full textThe green-lipped mussel, Perna canaliculus, is endemic to New Zealand and forms the basis of a mussel aquaculture industry producing more than 100,000 t and over NZ$200 million of export earnings annually. However, until recently the mussel industry has remained entirely dependent on wild-caught spat, the supply of which is highly variable in quantity and quality from year-to-year. Hatchery production could provide an alternative reliable source of seed to underpin the continuing expansion of the mussel aquaculture industry. However, little is known about the feeding preferences of early stage mussel spat which is needed for developing a more cost-efficient method for rearing hatchery spat. Therefore, the aim of the research presented in this thesis was to investigate the particle feeding in mussel spat through examining the morphology and operation of the feeding apparatus of green-lipped mussels over a range of sizes. In addition, preliminary feeding experiments were conducted using live microalgal feeds and a commercially available formulated feed, MySpat. Microscopy revealed marked ontogenetic changes in the morphology and feeding capabilities from spat to adult mussels. These results suggested that contrary to the commercial practice of feeding spat small-sized (3-6 µm in diameter) microalgal feeds it may be more efficient to provide them with microalgae of a larger size given their morphological constraints on efficiently filtering smaller food particles, i.e., < 5 µm in diameter. A Coulter counter was used to assess the ability of spat of a range of sizes to capture a variety of different sizes and types of particles, including microalgae, polystyrene beads and MySpat. The results suggested the most effective method for increasing artificial diet utilization in hatchery production of mussel spat is to restrict diet particles to a size range of less than 15 µm diameter. In this regard the Coulter Counter assessments found a significant fraction of the particles of the formulated feed, MySpat, were larger than 15 µm in diameter, which appeared to cause some difficulties for consumption of this feed by spat. However, in small scale experiments it was possible to substitute up to 50-75% of the total dry weight of live microalgal feed with MySpat without compromising growth rate in spat of 260 µm in shell height and larger. However, contradictory findings among the research methods indicate that further research is required to improve the performance of formulated feds for P. canaliculus spat so as to achieve more efficient production of mussel seed for aquaculture
Solving the problem of poor spat retention on New Zealand's Greenshell mussel (Perna canaliculus) farms
No full textGreen-lipped, or Greenshell™ mussels (Perna canaliculus) are the single most important species for New Zealand’s aquaculture sector in terms of volume and value of production. High losses of recently settled seed mussels, or “spat” during the early stages of Greenshell™ aquaculture is a major problem for the industry due to the resulting inefficient production and the creation of a shortage of spat supply which constrains the growth of the industry. Despite the severity of the problem, few studies have documented the timing and magnitude of spat losses on Greenshell™ farms, and little is known about the causes. Therefore, the research presented in this thesis, aimed to quantify the timing and magnitude of spat losses on Greenshell™ farms in relation to a range of possible causes, and several possible solutions to the problem. The magnitude of spat losses were estimated across the Greenshell™ industry as a whole, and the resulting estimate was confirmed at the farm scale in a subsequent series of field experiments (i.e., losses of > 99%). The timing and magnitude of spat losses were compared among farm sites throughout the Coromandel mussel growing area at multiple times throughout the year using spat from two sources (i.e., Kaitaia spat and line-caught spat). The impact of seeding density (11,000, 17,000 and 59,000 spat-1 m-1) and the physical structure of grow ropes on spat losses were also examined, and co-seeding of Kaitaia spat with a red macroalga (Pterocladia lucida), and the nursery rearing of spat in floating upwelling systems (FLUPSYs) were investigated for their potential to improve spat retention. Most spat losses were found to occur early on in production, shortly after seeding out, and were consistent among farm sites and spat sources. Secondary settlement behaviour was identified as a likely predominant cause of spat losses, along with the process of seeding out with large quantities of macroalgae that comprises Kaitaia spat material, which appears to prevent spat from successfully migrating onto the structure of the grow rope. The use of high seeding densities resulted in avoidable spat losses. Modifying the structure of grow ropes had no effect on spat retention. The co-seeding of Kaitaia spat with the macroalgae Pterocladia lucida improved spat retention by 33% relative to controls, by encouraging a greater proportion of spat to migrate onto the grow rope, most likely through the production of natural chemical cues. Finally, the introduction of a FLUPSY-based nursery system into the Greenshell™ production cycle was shown to reduce spat losses compared to spat grown directly in adjacent coastal waters (i.e., 78% vs 99.8%). Overall, the results of this research increases the understanding of the timing and magnitude of spat losses on Greenshell™ farms, identifies some possible causes of the problem, and presents some practical solutions. These
results will facilitate further, more targeted research into the problem, and provide a starting point for further research into developing more effective solutions
Ambient underwater sound : understanding its origins, variations and biological role
No full textUnderwater sound may act as an orientation cue for guiding the long range movements of the
larvae of some fishes and crabs toward suitable settlement habitats on the coast. Experimental
evidence for this claim has been hard to secure due to the virtual impossibility of controlling
sound in experimental aquaria, and difficulties of conducting field experiments. However, a
number of different approaches, including the use of diver observation, have found behavioural
evidence in support of orientation to underwater sound. The present study examined the use of in
situ SCUBA observations as a research tool, and found it produced high intensity noise in the
frequency range to which fish and decapods are most sensitive. These findings raised questions
about the appropriateness of diver observation as a tool. Consequently, an in situ behavioural
binary choice chamber was used to demonstrate that crab post-larvae of five species showed an
orientation response toward a sound cue. These results add to earlier behavioural data indicating
that acoustic orientation could be of considerable ecological importance in influencing the
settlement success of coastal fish and crustaceans.
Evaluation of the importance of sound as an orientation cue also requires a better characterisation
of reef sound. A systematic investigation into the temporal and spatial (scales< 2 km) variation
of ambient underwater sound in a shallow coastal environment found there were remarkable
daily, lunar and seasonal variation in ambient underwater noise power levels. Dusk was the
loudest time of day, the new moon was significantly louder than the full moon, and summer was
the loudest season. Snapping shrimp are a ubiquitous source of ambient underwater noise
between 5 - 20 kHz, with the number of snaps produced having the same significant daily, lunar
and seasonal variations as the power levels. Snapping shrimp activity also varied between habitat
types. Additional to snapping shrimp sounds, there was a significant rise in intensity between
500 - 3000 Hz caused by an unknown source. Laboratory experiments provided conclusive
evidence that Evechinus chloroticus produce feeding noises in this frequency band, while field
recordings from different reefs indicated power level in this frequency band reflected the size
frequency and density of E. chloroticus populations. These results highlight the potential importance of sea urchins as a significant source of biological noise in temperate shallow coastal
waters.
Overall, the results have provided additional behavioural evidence for the orientation of
crustacean to reef sound, and significantly extended our understanding of reef noise
characteristics and origins. It is argued that the temporal, spatial and biological characteristics of
ambient underwater sound could play a significant role in structuring coastal communities
Hauraki Gulf SCHISM hindcast
No full text<p>A high-resolution 3D SCHISM numerical model of the Hauraki Gulf, New Zealand was run to produce hindcast results over the period 1994 - 2020.</p>
<p>This repository contains only sample results for one day (1 January 2019). The full dataset is available from: </p>
<p><span><a href="https://hauraki-gulf-schism-hindcast.cloud.edu.au/thredds/catalog/outputs/outputs/catalog.html">https://hauraki-gulf-schism-hindcast.cloud.edu.au/thredds/catalog/outputs/outputs/catalog.html</a> </span></p>
Defining and assessing mussel reef restoration success
No full textExtensive biogenic shellfish reefs were once a dominant feature of many coastal areas, however, unsustainable harvesting pressures combined with habitat degradation have resulted in the loss of numerous oyster and mussel reefs. Increasingly, ecological restoration is being applied as a conservation and management tool to reinstate lost mussel reefs and their associated ecosystem services. However, the ability to assess restoration progress for, and among, these projects is limited due to inconsistent monitoring plans. The research presented in this thesis aims to address two of the greatest limitations currently facing monitoring mussel reef restoration efforts; poorly defined restoration end-goals, and ineffective methods for assessing and reporting restoration progress. A theoretical reference system was developed in combination with exemplar restoration goals to aid in defining mussel reef restoration success. A monitoring framework was then developed to provide a means for assessing the ecological success of mussel restoration, using a three-tiered approach: 1) universal metrics, 2) goal-based metrics, and 3) environmental metrics. The ecological success of a mussel restoration project in Ōkahu Bay, Auckland, New Zealand, was assessed for the first 12 months post-deployment using the newly-developed mussel monitoring framework. Mussel restoration occurred here over two sediment types (i.e., soft, muddy sediment and a shell hash base), with universal and goal-based metrics for sediment structure and productivity assessed on each substrate type. While each substrate differed in sediment grain size, monitoring found no other differences in metrics between the two substrate types, suggesting that substrate type did not influence the survival or growth of mussels in Ōkahu Bay over the first 12 months. To aid in streamlining the collection, recording, and reporting of mussel restoration monitoring data, a digital Hub was developed using Google Sites. The Hub provides a centralised database for the recording of monitoring results and facilitates comparisons among mussel restoration projects to be made. Overall, the results of this research provide the first steps in improving the efficiency of monitoring mussel reef restoration by developing effective methods for defining and assessing restoration success. Effective means for determining restoration success are pivotal for improving and upscaling mussel reef restoration initiatives
Efficacy of adenosine, theanine and isobutanol to modulate metabolism in support of live transport of commercially important decapod crustaceans
No full textAquatic crustaceans contribute a significant proportion of the global seafood industry and are experiencing growing consumer demand. Live large crustaceans, such as lobsters, crabs and large shrimps, frequently attract premium prices in many seafood markets, particularly in Asia. However, achieving these premium prices requires the successful transport of live crustaceans from capture or aquaculture to market. Transportation typically occurs out of water to lower weight and overall costs, placing the crustaceans under significant metabolic stress as gas exchange becomes restricted due to gill collapse. Transport under these conditions can take 16- 24 hours leading to prolonged exposure to these stressors and increased morbidity and mortality upon arrival of 5 – 10 % or more resulting in a marked decrease in their market value. Reducing the metabolic stress associated with transport increases overall survival and maintains quality and value of the crustaceans. Current approaches, such as cooling and the use of chemical anaesthesia, are either ineffective, costly or inappropriate for use in food products; as such alternatives are needed. In an effort to decrease metabolic stress associated with transport, the effects of three compounds; adenosine, theanine and isobutanol, were variously tested in three commercially important crustacean species (Macrobrachium rosenbergii, Metanephrops challengeri and Panulirus ornatus). Heart rate (HR) and/or CO2 production were monitored non-invasively as a proxy for metabolic rate while tissue and haemolymph metabolites were measured to provide a more direct measure of metabolism. Adenosine injected into the giant freshwater prawn (M. rosenbergii) led to a significant decrease in HR during 3 hours of immersion. Administration of adenosine at a concentration of 2.5 mM led to a ~30 % decrease in HR from baseline that was sustained for 2 hours. Treatment with a concentration of 2.5 mM led to a decrease in tissue glycogen compared with untreated controls, while haemolymph lactate was unchanged across treatments. Treatment with adenosine and theanine in the New Zealand scampi (M. challengeri) caused a significant decrease in HR during 4 hours of air exposure. Adenosine and the adenosine/ theanine mixture had the greatest impact on HR with a sustained depression of 25 % compared to untreated controls. The effect on HR did not translate to widespread metabolic suppression as glycogen, glucose, lactate and ammonia concentrations were not significantly different across treatment. Isobutanol treatment prior to air exposure in juvenile ornate tropical rock lobster (P. ornatus) led to a decrease in CO2 production rate and a suppression of overall metabolism. Glycogen utilization was reduced while the accumulation of metabolic waste, including lactate and ammonia, was attenuated. Isobutanol showed effectiveness at increasing survival during 20 hours of simulated transport. Treatment with 25 and 50 ppm decreased glycogen utilization and lowered the accumulation of metabolic waste products.
Overall, the results show that adenosine and theanine may have limited commercial applicability for live crustacean transport due to their rapid clearance, inconvenient administration and low efficacy. In contrast, initial results indicate that isobutanol is a promising metabolic suppressant and anaesthetic for crustaceans that is easily administered and that warrants further investigation into its use in transporting live crustaceans
Recycling the nutrients from pāua aquaculture effluent into a fresh seaweed feed
No full textThis is the first study to test the potential of macroalgae to grow and remove nutrients from New Zealand pāua farm effluent. Three different macroalgae culture systems were compared for the treatment of aquaculture effluent and macroalgae production: a suspended macroalgal culture system – representing a high rate algal pond, and two algal turf scrubber (ATS) culture systems with attached macroalgae (i.e., a typical land-based system and a novel floating system). A series of consecutive experiments were conducted for batch, semi-continuous, and nutrient spiked semi-continuous culture using these three culture systems. The suitability of the Ulva spp. cultured in the effluent was then tested as a feed supplement for pāua. Four different feeding treatments were tested, with replacement of formulated abalone feed with different amounts of fresh effluent-grown Ulva spp.In the batch culture experiment, macroalgae grew well and removed ammoniacal-N (from ~1.5 to 0 mg NH3-N L-1) from the pāua aquaculture effluent during 0 – 3 days in both ATS culture systems and 1 – 6 days in the suspended culture system. However, the nitrate concentration (~2.4 mg NO3--N L-1) was not reduced below 1 mg NO3--N L-1 in any of the culture systems and dissolved reactive phosphorus (DRP) was too low to measure. The highest growth rates measured in each culture system were 12.5 g m-2 d-1 (suspended), 8.3 g m-2 d-1 (floating ATS), and 1.6 g m-2 d-1 (land-based ATS), but these growth rates were highly influenced by the amount of biomass initially present. In the semi-continuous culture experiment, the macroalgae also grew well and removed ammoniacal-N (from 1.23 to ~0.06 mg NH3-N L-1) from the pāua aquaculture effluent (with 94, 98, and 99% removal achieved by the suspended culture system, floating ATS culture system, and land-based ATS culture system, respectively) even at a 1-day HRT (hydraulic retention time). However, the ~2.4 mg NO3--N L-1 inflow nitrate concentration was not reduced below 1 mg NO3--N L-1 in any of the culture systems. The inflow DRP concentration was still below detection. The highest growth rate measured in each culture system when operated at a 1-day HRT was 6.3 g m-2 d-1 (suspended culture system), 7.7 g m-2 d-1 (floating ATS culture system), and 16.2 g m-2 d-1 (land-based ATS culture system). In the spiked semi-continuous culture experiment, the pāua aquaculture effluent nutrient concentration was increased to ~30 mg NH3-N L-1 and ~3 mg DRP L-1. The land-based ATS culture system showed the most potential for phycoremediation of aquaculture effluent and production of macroalgal biomass. The land-based ATS had the highest ammoniacal-N removal and macroalgal growth rate (16.2 g m-2 d-1) but became contaminated by nitrifying bacteria, which led to an accumulation of nitrate-N (up to 13 mg NO3--N L-1). Also, the land- based ATS culture system may be susceptible to contamination by colonial cyanobacteria which may outcompete the macroalgae. In contrast, the suspended culture system consistently showed lower (and less consistent) ammoniacal-N removal and had the lowest macroalgal growth rate (6.3 g m-2 d-1), although it was not contaminated by nitrifiers it was often contaminated by phytoplankton at the high inflow nutrient concentrations. Therefore, the land- based ATS culture system and to a lesser extent, the suspended culture system warrants further evaluation at both mesocosm scale and commercial large scale. Complete removal of ammoniacal-N (0 mg L-1) and near-complete nitrate-N removal (~1 mg L-1) from the drum filter backwash effluent produced by Moana Ltd’s pāua aquaculture facility could be achieved in all three macroalgal culture systems with a surface area of 1,280 m2 (100 × 12.8 m). The land-based ATS culture system alone or the integration of both the land-based ATS and suspended culture systems could provide the highest nutrient removal and macroalgal production. Effluent-grown Ulva spp. was found to be an excellent feed supplement for pāua with no difference in the survival or growth of juvenile pāua when up to 20% of a formulated diet (Abfeed®) was replaced with fresh Ulva spp. in a 38-day feeding trial. A 20% substitution of Abfeed® is economically beneficial given that this feed costs NZ$3.60 kg-1. It was estimated that sufficient Ulva spp. could be produced to supply 20% of the feed requirements for Moana Ltd’s entire pāua farm from a macroalgal culture system covering an area of 7,230 m2 (100 × 72.3 m) and using 100% of the drum filter backwash effluent (259,200 L d-1) and 10% of the drum filtered effluent (1,290,087 L d-1). The present preliminary study has demonstrated the potential of land-based macroalgae culture systems to remove nutrients from New Zealand pāua farm effluent whilst also producing Ulva spp. as a suitable feed for cultured pāua
Factors influencing the retention of early juvenile green-lipped mussels, Perna canaliculus (Gmelin, 1791), in aquaculture production
No full textThe global mussel aquaculture industry relies heavily on the regular supply of wild seed
mussels, known as spat, to initiate aquaculture production. Supplies of wild mussel spat have a
lower cost than spat produced in a shellfish hatchery, but wild spat are often highly variable in
quantity, size and nutritional condition, which greatly affects their performance after being
seeded out onto coastal mussel farms. For example, high losses of more than 80% of spat
consistently occur within the first few weeks after seeding out in New Zealand’s green-lipped
mussel (Perna canaliculus) industry. These losses have often been associated with variability
of the size and nutritional condition of wild spat prior to seeding. This current study has
confirmed that variability of size of green-lipped mussel spat prior to seeding affects their
subsequent retention, where spat of larger than 1 mm in shell length have a higher propensity
to remain attached to aquaculture longlines when compared to spat of less than 1 mm. Wild
spat collected and transported for ~40 h from their collection site show reduced nutritional
condition, as indicated by their low glycogen reserves. When exposed to periods of
experimental starvation of up to two weeks, spat were found to utilise glycogen reserves as their
primary source of energy. Observations during this current study indicated that sufficient
supplies of high quality food appear to be important for spat retention both in the laboratory
and field situations. Spat that were experimentally starved for up to two weeks, to emulate
conditions experienced during spat transportation from the collection sites to the seeding sites,
showed a lower retention in the laboratory than spat that were well fed. However, once spat
were seeded out, the local environmental conditions at the seeding site at coastal mussel farms
appeared to play an important role in determining the subsequent retention of mussel spat. The
unfavourable environmental conditions at the mussel farm used for experimentation, may have
included low water velocities and insufficient food supply, the presence of which was thought
to reduce the retention of spat on the mussel farm, despite them being well fed prior to seeding.
The potential use of commercially available concentrated microalgal products were
experimentally evaluated as complete and partially substitutes for feeding live microalgae to
mussel spat. Concentrated microalgal products can be used to replace up to 50% of live
microalgae for feeding spat without compromising their survival and nutritional condition.
Overall, the research presented in this study improves our understanding of the effects of size
and nutritional condition of spat at the time of seeding out onto coastal mussel farms on their
subsequent retention, and the nutritional requirements of spat and how these may be met
through feeding live microalgae and substitute products
Determination of structural dimensioning loads of a fast catamaran using rigid-backbone segmented model testing techniques
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