Kevin Heasman

Detection of tetrodotoxin from the grey side-gilled sea slug - Pleurobranchaea maculata, and associated dog neurotoxicosis on beaches adjacent to the Hauraki Gulf, Auckland, New Zealand

Investigations into a series of dog poisonings on beaches in Auckland, North Island, New Zealand, resulted in the identification of tetrodotoxin (TTX) in the grey side-gilled sea slug, Pleurobranchaea maculata. The levels of TTX in P. maculata, assayed by liquid chromatography-mass spectrometry (LC-MS) ranged from 91 to 850 mg kg(-1) with a median level of 365 mg kg(-1) (n = 12). In two of the dog poisoning cases, vomit and gastrointestinal contents were found to contain TTX. Adult P. maculata were maintained in aquaria for several weeks. Levels of TTX decreased only slightly with time. While in the aquaria, P. maculata spawned, with each individual producing 2-4 egg masses. The egg masses and 2-week old larvae also contained TTX. Tests for other marine toxins were negative and no other organisms from the area contained TTX. This is the first time TTX has been identified in New Zealand and the first detection of TTX in an opisthobranch.

Long-term coexistence of non-indigenous species in aquaculture facilities.

Non-indigenous species (NIS) are a growing problem globally and, in the sea, aquaculture activities are critical vectors for their introduction. Aquaculture introduces NIS, intentionally or unintentionally, and can provide substratum for the establishment of other NIS. Little is known about the co-occurrence of NIS over long periods and we document the coexistence over decades of a farmed NIS (a mussel) with an accidently introduced species (an ascidian). Both are widespread and cause serious fouling problems worldwide. We found partial habitat segregation across depth and the position of rafts within the studied farm, which suggests competitive exclusion of the mussel in dark, sheltered areas and physiological exclusion of the ascidian elsewhere. Both species exhibit massive self-recruitment, with negative effects on the industry, but critically the introduction of NIS through aquaculture facilities also has strong detrimental effects on the natural environment.

Preventing ascidian fouling in aquaculture: screening selected allelochemicals for anti-metamorphic properties in ascidian larvae.

Fouling by ascidians causes major stock losses and disrupts production in marine aquaculture, especially bivalve aquaculture. Currently, no cost effective solution exists despite the testing of many prospective control techniques. This study examined a range of allelochemicals suspected to inhibit metamorphosis in marine larvae. Five allelochemicals were screened in a larval metamorphosis bioassay using Ciona savignyi Herdman to determine their potential as a remedy for ascidian fouling in bivalve aquaculture. Three of the compounds tested inhibited ascidian larval metamorphosis and increased mortality at low concentrations. These were radicicol (99% inhibition of metamorphosis [IC99], 0.8 μg ml−1; 99% lethal concentration [LC99], 2.5 μg ml−1; 99% lethal time [LT99], 7.0 days), polygodial (IC99, 0.003 μg ml−1; LC99, 0.9 μg ml−1; LT99, 6.4 days), and ubiquinone-10 (IC99, 3.2 μg cm−2; LC99, 14.5 μg cm−2; LT99, 5.6 days; expressed as μg cm−2 due to insolubility in water and ethanol). While spermidine significantly affected metamorphosis and mortality of C. savignyi, the effect was insufficient to achieve inhibition in 99% of larvae over the 7-day timeframe of the assay. Muscimol did not affect metamorphosis or mortality at the concentrations tested. The present study demonstrates that radicicol, polygodial and ubiquinone-10 have potential for future development in antifoulant formulations targeted towards the inhibition of metamorphosis in ascidian larvae, while spermidine and muscimol appear unsuitable.

Screening for negative effects of candidate ascidian antifoulant compounds on a target aquaculture species, Perna canaliculus Gmelin

The natural chemical compounds radicicol, polygodial and ubiquinone-10 (Q10) have previously been identified as inhibitors of metamorphosis in ascidian larvae. Accordingly, they have potential as a specific remedy for the costly problem of fouling ascidians in bivalve aquaculture. In this study, these compounds were screened for their effects on the physiological health of an aquaculture species, the green-lipped mussel, Perna canaliculus Gmelin, at or above the 99% effective dose (IC99) in ascidians. Three physiological biomarkers of mussel health were screened: growth (increases in shell height and wet weight), condition (condition index) and mitochondrial respirational function (Complex I-mediated respiration, Complex II-mediated respiration, maximum uncoupled respiration, leak respiration, respiratory control ratios and phosphorylation system control ratios). While polygodial and Q10 had no effect on mussel growth or the condition index, radicicol retarded growth and decreased the condition index. Mitochondrial respirational function was unaffected by radicicol and polygodial. Conversely, Q10 enhanced Complex I-mediated respiration, highlighting the fundamental role of this compound in the electron transport system. The present study suggests that polygodial and Q10 do not negatively affect the physiological health of P. canaliculus at the IC99 in ascidians, while radicicol is toxic. Moreover, Q10 is of benefit in biomedical settings as a cellular antioxidant and therefore may also benefit P. canaliculus. Accordingly, polygodial and Q10 should be progressed to the next stage of testing where possible negative effects on bivalves will be further explored, followed by development of application techniques and testing in a laboratory and aquaculture setting.

Laboratory assessment of the antifouling potential of a soluble-matrix paint laced with the natural compound polygodial

Polygodial is a potent and selective inhibitor of ascidian metamorphosis that shows promise for controlling fouling by ascidians in bivalve aquaculture. The current study examined the potency of, and associated effects of seawater exposure on, a rosin-based soluble-matrix paint laced with 0.08–160 ng polygodial g−1 wet paint matrix. Paint-coated surfaces were soaked in seawater for 0, 2, 4 or 12 weeks prior to screening for antifouling activity using a bioassay based on the nuisance ascidian Ciona savignyi Herdman. Mortality was greater (mean 50% lethal concentration: 5 ± 2 ng g−1; mean 75% lethal concentration: 17 ± 4 ng g−1) and metamorphosis was inhibited (mean 50% anti-metamorphic concentration: 2 ± 0.4 ng g−1; mean 75% anti-metamorphic concentration: 15 ± 10 ng g−1) in C. savignyi larvae exposed to polygodial-laced soluble-matrix paints, relative to control paints without polygodial. Soaking in seawater prior to testing reduced the efficacy of the formulation up to nearly 12-fold, but even after soaking for 12 weeks paints laced with polygodial at 160 ng g−1 wet paint matrix prevented ⩾90% of the larvae of C. savignyi from completing metamorphosis. The outcome of this experiment provides a positive first step in evaluating the suitability of polygodial-laced soluble-matrix paints for use in aquaculture.

Screening for antioxidant and detoxification responses in Perna canaliculus Gmelin exposed to an antifouling bioactive intended for use in aquaculture

Polygodial is a drimane sesquiterpene dialdehyde derived from certain terrestrial plant species that potently inhibits ascidian metamorphosis, and thus has potential for controlling fouling ascidians in bivalve aquaculture. The current study examined the effects of polygodial on a range of biochemical biomarkers of oxidative stress and detoxification effort in the gills of adult Perna canaliculus Gmelin. Despite high statistical power and the success of positive controls, the antioxidant enzymes glutathione reductase (GR), glutathione peroxidase (GPOX), catalase (CAT), and superoxide dismutase (SOD); thiol status, as measured by total glutathione (GSH-t), glutathione disulphide (GSSG), and GSH-t/GSSG ratio; end products of oxidative damage, lipid hydroperoxides (LHPO) and protein carbonyls; and detoxification pathways, represented by GSH-t and glutathione S-transferase (GST), were unaffected in the gills of adult P. canaliculus exposed to polygodial at 0.1 or 1 × the 99% effective dose in fouling ascidians (IC₉₉). Similarly, GR levels, thiol status, and detoxification activities were unaffected in mussels exposed to polygodial at 10 × the IC₉₉, although GPOX, CAT, and SOD activities increased. However, the increases were small relative to positive controls, no corresponding oxidative damage was detected, and this concentration greatly exceeds effective doses required to inhibit fouling ascidians in aquaculture. These findings compliment a previous study that established the insensitivity to polygodial of P. canaliculus growth, condition, and mitochondrial functioning, providing additional support for the suitability of polygodial for use as an antifouling agent in bivalve aquaculture.

Mātauranga Māori driving innovation in the New Zealand scampi fishery

ABSTRACT Motivation to improve commercial fishing technology is changing from ‘how can we catch more fish’ to ‘how can we reduce the impact of fishing on the environment’. To implement new fisheries technologies and innovations, it is important to have sources of innovative ideas for improvement, and processes to allow the uptake and transition from old to new technologies. One fishery that is undergoing a technology transition is the New Zealand scampi (Metanephrops challengeri) fishery. Here we report on a research programme aimed at improving the cultural and environmental performance of scampi fishing practices, initiated by the Māori-owned Waikawa Fishing Company, and underpinned by Mātauranga Māori and values inherent in kaitiakitanga. This paper provides a case study for how Mātauranga Māori and western science can engage in a fisheries technology transition through a transdisciplinary research programme.

Technological Approaches to Longline- and Cage-Based Aquaculture in Open Ocean Environments

As the worldwide exploitation rate of capture fisheries continues, the development of sustainable aquaculture practices is increasing to meet the seafood needs of the growing world population. The demand for aquatic products was historically satisfied firstly by an effort to expand wild catch and secondly by increasing land-based and near-shore aquaculture. However, stagnation in wild catch as well as environmental and societal challenges of land-based and near-shore aquaculture have greatly promoted efforts to development farming offshore technologies for harsh, high energetic environments. This contribution thus highlights recent technological approaches based on three sample sites which reach out from sheltered near-shore aquaculture sites to sites with harsh wave/current conditions. It compares and evaluates existing technological approaches based on a broad literature review; on this basis, we then strongly advocate for presently available aquaculture technologies to merge with future offshore structures and platforms and to unveil its added value through synergetic multi-use concepts. The first example describes the recent development of longline farming in offshore waters of New Zealand. New Zealand has designated over 10,000 ha of permitted open ocean water space for shellfish farming. The farms range from 8 to 20 km out to sea and a depth of 35–80 m of water. Research has been ongoing for the last 10 years and the first commercial efforts are now developing in the Bay of Plenty. New methods are being developed which should increase efficiency and reduce maintenance with a particular focus on Greenshell mussel (Perna canaliculus) and the Pacific Oyster (Crassostrea gigas), Flat Oyster (Tiostrea chilensis) and various seaweeds. The second case study involves a long-term, open ocean aquaculture (OOA) research project conducted by the University of New Hampshire. During the course of approximately 10 years, the technological aspects of OOA farming were conducted with submersible cages and longlines, surface feeding systems and real time environmental telemetry. The grow-out potential of multiple marine species such as cod (Gadus morhua), haddock (Melanogrammus aeglefinus), halibut (Hippoglossus hippoglossus), blue mussel (Mytilus edulis), sea scallop (Placopecten magellanicus) and steelhead trout (Oncorhynchus mykiss) were investigated at a site 12 km from shore. The last study presents a multi-use aspect of aquaculture for an open ocean site with fish cages attached to existing offshore wind energy foundations. Technological components such as mounting forces and scour tendencies of two different cage structures (cylindrical and spherical) were investigated by means of hydraulic scale modeling. The cages were pre-designed on the basis of linear theory and existing standards and subsequently exposed to some realistic offshore wave conditions. The wind farm “Veja Mate” in German waters with 80 planned 5 MW turbines anchored to the ground by tripiles is taken as the basis for the tested wave conditions. Based on findings stemming from the three example approaches conclusions are drawn and future research demand is reported.