Pacific oyster (Crassostrea gigas) farming in New Zealand has reached a point where the pressures on resources appear likely to constrain current, and future, development. To maintain industry growth, security of juvenile oyster (spat) supply and productivity gains within the existing farm leases, are becoming industry imperatives. The use of hatchery technology could achieve both of these requirements, but it is expensive to establish and maintain. The additional expense of a hatchery could be offset by the establishment of, for example, a selective breeding program to enhance oyster productivity and/or marketability. Consequently a pilot-scale oyster hatchery facility was constructed to investigate the potential for establishing hatchery production of Pacific oysters in New Zealand. This study showed that in the pilot-scale hatchery, oysters could be successfully spawned from in-season broodstock, the eggs fertilised and the resultant larvae reared through to settlement for on-growing to adult size. This process was successful for both oysters selected for morphological characteristics and those which were not. On-growing of the resultant stock indicated growth rate could be normal relative to wild caught oysters spat, although data was limited by the small scale of the experiment. However, an investigation of broodstock conditioning, to achieve out-of-season spawning, was less successful. Disease occurred and condition was lost in some broodstock, suggesting they were enduring stress within the conditioning system. The microalgal food supply was examined but the clearance rate of the microalgal species suggested they were an acceptable feed supply which agreed with previous reports of successful conditioning techniques. Comparing the pilot-scale facility in this study with descriptions of facilities which reported successful broodstock conditioning suggested that the use of a microfiltered recirculating water supply, as opposed to the more common flow-through, natural seawater systems containing a range of small size particles, limited necessary nutrient and/or maturation factors and may have had a significant impact on conditioning. The nanoplanktonic (< 10 μm), food resource, which includes key microalgal species such as Chaetoceros spp. and Isochrysis spp., is generally considered the primary food resource for suspension feeding bivalves, including C. gigas. However, the picoplanktonic fraction (< 3 μm) can provide the largest proportion of this food resource in the water column in terms of abundance and biomass. Consequently, an investigation of the in situ retention of picoplankton populations (picoeukaryotes, Synechococcus-type cyanobacteria and heterotrophic bacteria) by oysters was undertaken. Flow cytometry was used to quantify the picoplankton populations in water samples taken from the inhalant and exhalant feeding currents of individual oysters, allowing retention efficiency of the particles to be calculated. Five picoplankton populations were identifiable by flow cytometry (picoeukaryotes, heterotrophic bacteria and 3 populations tentatively identified as cyanobacteria) and accounted for a large proportion (up to 97 %) of the estimated available carbon (picoplankton + microalgae) in Kerikeri Inlet water. Generally the heterotrophic bacteria accounted for the largest proportion of the biomass with up to 564 ± 51 ng C ml-1. Retention of each picoplankton population was found to be variable and not directly related to particle concentration. Cyanobacteria (Cy2 population) were retained with the greatest efficiency (up to 42 ± 4.4 %), followed by heterotrophic bacteria (up to 38 ± 4.5 %) and picoeukaryotes (up to 12 ± 3.8 %). Overall more picoplankton biomass was retained during the summer months, of which the heterotrophic bacteria made the largest contribution in either cell number or estimated carbon retained. Tracking of the condition and constituent fractions (glycogen, lipid and protein) of the subject oysters showed that in the summer months, post-spawn, these levels were lowest, indicting a period of nutritional stress. This appeared to suggest that C. gigas was able to alter its retention efficiency to expand the range of particles captured, and consequently the available nutrient pool. The retention of greater quantities of heterotrophic bacteria may allow for the acquisition of essential nutrients required for growth and later gametogenesis (such as B vitamins). However, it is also possible that the heterotrophic bacteria mediate access to otherwise inaccessible, or inefficiently accessed, nutrient resources through their degradation of, for example, crystalline cellulose. Consequently, the microbial flora associated with the oyster gut was investigated. An initial investigation, cultivating bacteria from gut contents, showed considerable variability in the numbers of colonies present within and between samples, but was inconclusive for identifying differences in species diversity. Using culture independent histological and 16S rDNA PCR/RFLP techniques to investigate the oyster gut microflora a spirochaete flora, commonly associated with bivalve crystalline styles, was clearly present. Molecular analyses provided evidence of other bacterial in the gut. A signature RFLP band pattern was found in oysters at low tide and this generally reoccurred in oysters that had been immersed for varying lengths of time up to high tide. However, the signature RFLP pattern became more dilute as immersion time/potential feeding time extended. The isolation of culturable bacteria from the oyster gut allowed characterisation and identification of a subset of the oyster gut microflora. 16S rDNA sequence analysis from selected isolates showed a predominance of Vibrio spp. These bacteria had previously been associated with marine molluscs, including as symbionts. Characterisation of these and other isolates from oyster gut showed a diversity of attributes including the ability to degrade cellulose. This suggests the bacterial production of enzymes, such as cellulases, which have been reported by other researchers as being present in ineffectual or low native levels in oysters. Consequently the bacterial presence in the oyster gut may be essential to efficient nutrient acquisition. The results of these investigations have highlighted the potential importance of the heterotrophic bacteria to C. gigas. To date, bacteria have received relatively little attention in terms of their potential nutritive contribution to oysters, primarily due to observations that they are retained with low efficiency. However, even at low retention efficiencies the potential nutritive contribution is large due to the available abundances of heterotrophic bacteria. While the mechanisms and controls of bivalve suspension feeding have yet to be fully elucidated, the published literature indicates that selective mechanisms are available to bivalves including C. gigas and this current research suggests that even pico-sized particles, retained with apparently low efficiency, can be subject to selection. The importance of the heterotrophic bacteria to C. gigas requires further investigation as it will have implications for not only hatchery production, but also farm management, public health and environmental impact monitoring.

Confronting Barriers to Ecological Information Transfer in New Zealand's Fisheries Management system: Towards Developing a Trajectory for Trans-disciplinary Inquiry This thesis confronts barriers to ecological information transfer in New Zealand's fisheries management system. The investigation reveals a wider problematic within the governmental institutions of the fisheries milieu. The thesis deploys Callon's (1991) concept of translation to ask new questions regarding the conduct of fisheries science and management, which since the introduction of the Quota Management System in 1986, has been defined through the practices of commercial stakeholder groups. These stakeholders enrol ecological information through a narrowly defined and non-reflexive discourse of sustainable utilisation to serve specific purposes that suit their own needs. The thesis uses imaginaries to illustrate how sustainable utilisation has marginalised those stakeholders with different views on how ecological information could be used in fisheries management decision making. Moreover, the thesis contends that the milieu's hegemonic ontological environment prevents translation by mitigating the potential for dialogue between stakeholder groups. The thesis engages with a wide range of literature and cuts through established modes of thinking, developing a trans-disciplinary discourse that re-conceptualises the fisheries management problematic in process terms. The thesis demonstrates how trans-disciplinary dialogue that might transcend the current impasses in the New Zealand fisheries milieu will only develop through a network of previously unconnected groups. The thesis proposes a series of policy and behavioural interventions aimed at shifting the existing hierarchies of power and realigning established networks to ensure such dialogue is possible. Keywords: trans-disciplinary research, translation, network alignment, New Zealand, ecological information transfer, fisheries management.

Orca (Orcinus orca), also known as killer whales, are more widely recognised than other marine mammals. Although they have been reported from all oceans of the world, including the seas around New Zealand, information above anecdotal notes exists for only a few places. Orca are an apex marine predator that exhibits cultural differences in diet, vocalisations, and behaviour, between and within populations. This study was established to determine baseline information on New Zealand orca and to provide recommendations for future management and conservation. The conservation status of orca worldwide is poorly known, although two populations of the Pacific North West Coast of North America have recently been classified as ‘Threatened’ and ‘Vulnerable’. Photo identification was used to determine the population size, distribution around New Zealand waters, as well as range use and association among individuals. The total New Zealand orca population is small (range 65-167 animals, with 115 calculated alive in 1997). Resighting rates were high, with 75 % (n = 88) of the animals seen on more than two occasions. The mean number of sightings for the 117 photo-identified animals was 5.4, the mode was one sighting, and the median 9 – 10 sightings. One orca was photographed over a 20 year period. Population structure, frequency of association with others, and other social behaviours were used to determine population demographics. The New Zealand orca population appears to be made up of at least three sub-populations based on geographic distribution (North-Island-only, South- Island-only and North+South-Island sub-populations). Preliminary mtDNA analysis supports the hypothesis that some New Zealand orca do not mix. The mean Association Indices within the North-Island-only and South-Island-only sub-populations are significantly greater than within the North+South-Island sub-population. Those animals sharing food had higher Association Indices than those who did not share food. Sex ratios appear similar within each sub-population and calves were present in each, suggesting all sub-populations are breeding. Feeding behaviour was observed to assess habitat use and differences between foraging strategies and prey preferences. Twenty four different species of prey have been recorded in the New Zealand orca diet. Of these, ten have not been recorded elsewhere. The prey consists of four types; rays (the most common food type), sharks, fin-fish and cetaceans (pinnipeds have not been identified as a prey source). Foraging strategies were different for each prey type, with benthic foraging for rays in shallow waters the most diverse strategy used in New Zealand. Food sharing was observed for all prey types. One of the three proposed New Zealand subpopulations appears to be generalist or opportunistic foragers, feeding on all four prey types, another sub-population slightly less so, feeding on three prey types, and the third sub-population appears to be a more specialist forager, only recorded taking one prey type (cetaceans). Potential threats to orca, in addition to small population size, such as bioaccumulation of toxic chemicals, oil spills, boat strikes and shootings are considered and recommendations for conservation and future management are offered. Whether the three sub-divisions within the New Zealand orca population are reproductively isolated and hence require separate management, and whether there is further sub-division within the proposed North+South-Island sub-population, requires further study including genetic analysis. Some level of ongoing monitoring is recommended to ensure that the population of New Zealand orca does not decline. In addition, records of stranding locations and details of strandings are appended. Twenty-four live strandings occurred, involving 63 killer whales, of which 17 animals were successfully refloated and two of these resighted. One was seen after three years (nine resightings) and the other after four months (10 resightings). Refloating stranded orca is recommended.

The biochemical pathways involved in nitrogen (N) utilisation by marine phytoplankton have received considerable attention over the last forty years, but our understanding of these processes, and how they are affected by environmental change is still far from complete. This study investigates N metabolism in marine phytoplankton in both a controlled laboratory environment (using the coastal marine diatom Phaeodactylum tricomutum), and in the open ocean (e.g. Jellicoe Channel and the Subtropical Convergence Zone, New Zealand). Although the characteristics of ammonium uptake have been extensively studied in marine phytoplankton, comparatively little information exists on rates of assimilation. In this study, a robust method for measuring the rate of ammonium assimilation after a transient addition of ammonium is described. The method relies on the measured ability of the protonophore carbonyl cyanide m-chlorophenylhydrazone (CCCP) to release unassimilated ammonium from the cell and prevent further assimilation. There was little or no correspondence between the rate of ammonium assimilation and rates of ammonium uptake or maximum glutamine synthetase (GS) activity in Phaeodactylum tricomutum. Moreover, in N-limited cells maximum GS activity was a poor measure of N incorporation under steady-state conditions. However, GS activity did provide reliable information on N status (e.g. increased GS activity with increased N-limitation). Comparisons of the effects of varying N-source suggest that nitrate-grown cells are not disadvantaged under conditions of N-limitation due to the extra costs associated with nitrate reductase (NR) and nitrite reductase (NiR) activity. The metabolic costs of growth on nitrate may be significantly increased under iron (Fe)-limitation, as both NR and NiR require Fe. Fe-limited chemostat cultures excreted nitrite and ammonium when grown on nitrate. This release is probably a response to insufficient photoreductant under Fe-limited conditions. However, under Fe-limitation cellular N and C was similar to that of Fe-replete cells, suggesting that the N-source used for growth (nitrate or ammonium) did not influence N-assimilation (i.e. that nitrate-grown cells were able to secure the extra reductant required to support growth) under Fe-limited, light saturating conditions. The Gln:Glu ratio (an index of the cellular N-status) was significantly reduced under N-limitation, but not under Fe-limitation. Measurement of several biochemical indicators of the physiological state of phytoplankton cells (e.g. Gln:Glu ratio, GS activity, and Fv/Fm ratio) permitted the nutrient status of phytoplankton populations to be investigated during the NIWA Ocean Fronts programme over the Subtropical Convergence Zone, New Zealand. Low Gln:Glu ratios suggested that phytoplankton in both Subtropical and Subantarctic waters were N-limited, with a marked increase in this ratio when Fe was added to Subantarctic phytoplankton. The temporal utilisation of N by neritic phytoplankton was also investigated in Jellicoe Channel, northeastern New Zealand. Again, several biochemical indicators (e.g. Gln:Glu ratio, GS activity, and Fv/Fm ratio) were used to identify the N-status of this neritic phytoplankton assemblage both during bloom and non-bloom periods.

The impact of no-take marine reserves on spiny lobster, Jasus edwardsii, populations and the adjacent lobster fishery was assessed in a study that determined: the response of lobster populations to protection, if lobsters within marine reserves moved out into the surrounding fishery, examined the behavioural characteristic of lobsters that contributed to their recovery and spillover, and contrasted catch characteristics around a north-east New Zealand marine reserve with 2 unprotected sites. Surveys of 4 no-take marine reserves of different ages and 4 unprotected control sites confirmed that J. edwardsii increase in mean size and abundance within protected areas. Total lobster density was estimated to increase by 6.1% per year of protection. The relationship between age of reserve and the density of lobsters above the legal size limit (>100 mm carapace length) was complicated by depth related interactions between reserves, due to seasonal changes in the depth distribution of lobsters and differences in the timing of surveys among locations. However, density increases in legal sized lobsters were greater than those of the overall population. Mean size of protected lobsters increased in a non-linear fashion, reflecting the asymptotic growth characteristics of the species. Mean carapace length of lobsters increased by 11.24 mm after 3 years of protection and only by 16.25 mm after 2l years of protection. Corresponding increases in biomass (kg.500 m-2) and egg production (eggs.500 m-2) were estimated to be 7.4% and 6.6% respectively per year of protection. A tag recapture program indicated that the limited scale of movements and relatively high site fidelity of mature J. edwardsii aided the recovery of lobster populations in protected areas. Of 737 lobsters tagged in and around the Leigh Marine Reserve,212 were subsequently resighted. Seventy percent of resighted lobsters were relocated less than 250 m along the shore from their initial site after a mean period of liberty of 146 (se = 13.42) days. However, seasonal offshore movements took lobsters beyond the seaward boundary of the reserve where they were susceptible to capture. Of the 521 lobsters tagged on inshore reefs within the Leigh Marine Reserve. l.9% were caught over the seaward boundary by commercial fishers, and 14.4% of the 181 lobsters tagged over the seaward boundary were resighted on inshore reefs within the reserve. Movements into or out of the reserve across the longshore boundaries were also recorded for 7 out of the 27 lobsters moving further than 250 m along the shore. Acoustic tracking confirmed that J. edwardsii have a high site fidelity, with tracked lobsters spending a median of 84% of their time at their home site. Twenty one percent of the 26 lobsters fitted with acoustic tags never left their tagging site and, of those that did leave 56% eventually returned. Lobsters moved up to 3.1km away from their home sites but managed to find their way back after periods of 1 to 103 days away. Five lobsters had strong associations with two separate sites and made repeated movements between these alternate home sites. The straight line distance between alternate home sites ranged from 200 m to 1.3 km, and the period between visits to their primary or secondary home sites ranged from 1 to 93 days. Movement activity varied throughout the year, and seasonal patterns differed between males and females. Females displayed one peak in movement activity per year, around the time of larval release in September-October. Males displayed a summer peak centred on January, and a winter peak centred on July. The onset of high movement activity was often accompanied by a shift to deeper water and l0 of the 14 lobsters tracked for over 6 months spent periods away from the inshore reef system. Exposed groups of lobsters were observed aggregating in offshore areas of sand and low lying patch reef during the day. Offshore aggregations were observed over 7 months of the year and lobsters within the aggregations displayed behaviour consistent with the use of mutual defence. The sexual composition of the aggregations reflected seasonal patterns in male and female movement rates. Male J. edwardsii dominated the aggregations in winter and summer; times when peak feeding rates of males held in captivity were also recorded. Females dominated the offshore aggregations in September-October when larvae are released. Seven of the 26 lobsters fitted with acoustic tags moved over the boundaries of the Leigh Marine Reserve and Tawharanui Marine Park during offshore movements. Despite the fact that there is no fishing access to inshore reefs within the Leigh Marine Reserve, no significant difference was detected between the catch per unit effort (kg.trap haul-1) of lobsters caught around the reserve, nearby coastal Leigh or Little Barrier Island. However, catches around the marine reserve contained fewer (P=0.0009) but larger lobsters than at Little Barrier Island. The catch characteristics of lobsters from coastal Leigh were intermediate between the other two sites. As access to inshore reefs around the Leigh Marine Reserve was limited to a small area at either end of the reserve, traps tended to be set in offshore locations and the sexual composition of the total catch around the Leigh Marine Reserve reflected the seasonal movements of males and females into, and out, offshore areas. At coastal Leigh and Little Barrier Island the location of traps was not restricted and greater use was made of coastal fringing reefs. As a result the sexual composition of the catch at these locations did not reflect the movement of various components of the lobster population into and out of specific habitats or locations. Overall, the results of this study suggest that relatively small (~ 5 km2) no-take marine reserves increase lobster biomass and egg production, without adversely affecting catch rates in the surrounding fishery. Marine reserves may therefore represent a viable management tool, which if used in conjunction with other management regimes, could provide a more precautionary approach to the management of the J. edwardsii fishery at minimal cost to the industry.

This study focuses on an assessment of the health status of the yellowbelly flounder (Rhombosolea leporina) from two estuarine locations (site 1 – the mouth of the Henderson Creek; site 2 – the mouth of the Whau Creek) in the Waitemata Harbour. This harbour borders the highly urbanised and industrialised Auckland City metropolitan area. Whangaparaoa Peninsula, located approximately 30 km north of the other two collecting sites (away from the main urban area), was chosen as a reference site for comparative purposes. Physico-chemical analyses revealed differences in water quality at the sampling sites. A lower pH, oxygen deficiency and higher temperature were recorded in both the Waitemata Harbour locations in comparison with the reference site. Histopathological analyses revealed significantly higher prevalences and severity of pathological changes in the gills, blood, liver, kidney and gonads of the yellowbelly flounder from both harbour locations in comparison with fish from the reference site. ln addition, some types of lesions (eg. neoplasms) were observed in fish from the two harbour locations only. Abnormalities in the gill structure of fish from both harbour sites included: epithelial swelling (hyperplasia and hypertrophy), necrosis, and lifting with oedema; the fusion of secondary lamellae; aneurysms; filamental deformities; mucous cell proliferation, and infestation by Trichodina. The abnormalities found in the blood of these fish were manifested as: polycythaemia; erythrocytosis; erythroblastosis; leucocytosis (increased neutrophils); poikilocytosis; anisocytosis and an increased prevalence of erythrocytes undergoing necrosis. Vacuolar degeneration of the hepatocellular parenchyma due to lipid or glycogen accumulation was the most prominent liver change observed in fish from all sampling sites. The other liver abnormalities observed in flounder from the two harbour sites included: foci of cellular alterations (clear, basophilic and necrotic), congestion of the sinusoids, infestation by nematodes, and anaplastic growths (cholangiocellular carcinoma and teratoma). Pathological changes found in the kidneys of flounder collected at both harbour sites were classified as glomerular abnormalities (atrophy and dilatation of the glomerular tuft; enlargement of Bowman's space) and tubular vacuolar degeneration and necrosis. The presence of myxosporean parasites was also a common finding in the kidneys of harbour fish. Follicular atresia was the most prevalent change observed in the ovaries of flounder from the two harbour sites. Biochemical analysis of plasma proteins and electrolytes of flounder from the three sampling sites revealed hyperbilirubinaemia, hypoalbuminaemia and uraemia in those inhabiting both harbour sites. In addition, the concentration of total liver microsomal proteins was significantly depressed in flounder from harbour sites 1 and 2 when compared to that of fish from the reference site. Concentrations of heavy metals in the livers of flounder from different sampling localities were found to decrease in the order: site 2 > reference site > site 1, and did not correlate with the prevalences of liver abnormalities. Significantly more prominent pathological changes were thus observed in fish from both estuarine harbour sites in comparison with those from the reference open water site. The pathological changes noted are believed to occur in response to environmental changes. Contamination by different xenobiotics in the Whau and Henderson Creeks, which have been recorded in previous studies, suggest the possibility of direct toxic effects of the water contaminants on flounder from the estuarine parts of these creeks. In addition, the relatively high temperature, low pH and low oxygen levels recorded at the two sites in the Waitemata Harbour are believed to have induced oxygen deficiency-related tissue hypoxia which could then have led to the expression of a variety of diseases of which some have been detected in this study. However, the possibility that some unknown and unmeasured causal factors may have produced the observed pattern of flounder diseases cannot be eliminated.

The population biology and ecology of scallops in Greater Omaha Bay (a semi-oceanic bay) and Kawau Bay (a estuarine bay) was quantified by observation and experiment. Information was collected to extend the knowledge base on northern New Zealand scallop population dynamics, and for application to potential scallop enhancement in the region. Contagious scallop population organisation was found at all spatial scales examined, ranging from bay wide through to individual bed patchiness, down to the scale of inter-animal distances. Such clumping has strong implications for a range of population processes, including fishing susceptibility and fertilisation success. Monitoring of adults found two main spawning events to occur; in late October and in mid January. Changes in the gonado-somatic index (GSI) were well synchronised between individuals within populations. Subsequent monitoring of spat-fall in artificial collectors documented two main recruitment events, probably the outcomes of the two local spawning events. These spat-fall events occurred on collectors separated by 1Os of km. However, substantial density variations occurred between sites, indicating that local hydrodynamics may have played a significant role in modifying local spat-fall intensities. Smaller spat-fall events were also present between the two major events. The number of spat collected at a number of combinations of site and time were sufficient to support commercial spat catching operations, although problems were encountered with spat detaching at sizes too small to be retained by the collectors. In the 1993/94 summer a large algal bloom event completely eliminated scallop recruitment to collectors for the first three months of that season. Mass mortality events were a major contributor to overall benthic scallop population mortality. Probable causes included intensive scallop harvesting (commercial and recreational), a major storm episode, and a large algal bloom. These effectively eliminated scallop populations from Greater Omaha Bay. The adjacent Kawau Bay was not affected by any of these particular events, but populations there did not survive long after reaching adult sizes. Estimates of M (natural mortality) were higher for all scallop populations than have been previously documented in New Zealand studies. Growth trajectories were reasonably consistent in waters shallower than 19 m, but a progressive decline occurred in both maximal size reached and average growth rates with increasing depth after this point. Food limitation may have been the mechanism involved, which is likely to vary significantly for other locations depending on local environmental conditions. Average time to recruitment to the fishery (100 mm shell width) was three years for the shallower populations. A slight reduction in average size of adults at higher densities was found for some populations, indicating a possible density-dependent effect. Examination of a high density scallop bed found animals to display distinctive substratum preferences over small spatial scales, with higher abundances occurring on coarser materials such as shell gravel, marl and grit. Mud was not favoured as a habitat type. Movements of tagged animals at this location were spatially limited to within the particular habitat patch in which an individual was tagged and released, i.e. at a scale of 1s to 1Os of metres. No animals moved between adjacent patches of similar habitat (100 m scale). A B.A.C.I type experiment was undertaken to assess incidental mortality effects of commercial scallop dredging on undersize scallops, at the spatial scale of beds. Significant negative effects were quantified, with the number of undersize animals killed per legal animal harvested estimated at 1.7 and 2.8 : 1, depending on the size frequency structure of the fished bed. Modelling of likely improvements in the number of animals surviving at the end of fishing, given a reduction in the minimum legal size from 100 to 90 mm, indicated improvements of 20 to 41% of the original population remaining after fishing, depending on animal size and assumed dredge efficiencies, A 90 mm MLS has subsequently been adopted by the Coromandel Scallop Fishery. The results from this work provide detailed population based estimates of parameters required for successful management and optimal harvesting strategies of Hauraki Gulf scallop populations. The large variability in parameters such as mortality, and strong abundance correlations with habitat type, has strong implications for such activities. This work also provides essential information for the undertaking of locally based enhancement operations, such as the spatial and temporal magnitude and variability of spat-fall events, and growth rates with respect to habitat features (i.e. depth).

The research presented in this thesis was undertaken in order to develop an understanding of the biology of Perna canaliculus sufficient to allow for commercial hatchery based production of Greenshell™ mussel spat. Hatchery production is an alternative to unreliable and inconsistent wild spat collection. In a Perna canaliculus population followed for one year spawning occurred in early spring and late summer. Three quantitative histological measures of gonad maturity utilising image analysis technology and a qualitative classification system were compared. Measuring the relative surface area comprised of gametes on histological sections was found to be the most reliable method. A practical gonad visual index to determine the reproductive condition of adults for the selection of broodstock was developed and found to be highly effective as a means of predicting induced spawning success. Serotonin was not effective for inducing spawning of Perna canaliculus. Temperature shock and the use of stripped gametes was however found to be a reliable spawning induction method. Relative gamete concentration, gamete age, temperature, sperm half life and gamete contact times were all found to have effects on fertilisation success for Perna canaliculus. Sperm concentration and the conditions of sperm aging were particularly important. Fertilisation kinetics of Perna canaliculus gametes modelled using the Vogel-Czihak-Chang-Wolf method suggested that 5% of sperm-egg contacts lead to successful fertilisation. Broodstock management protocols that could be used to condition the adult of Perna canaliculus were investigated in order to enhance and prolong the natural reproductive season. Research suggested that for successful broodstock conditioning animals should already have begun gametogenesis at the time conditioning is commenced. Successful conditioning of Perna canaliculus was achieved at temperatures between l0 and 16°C over a period of about 50 days. A diet ration above 2-3% of the dry meat mass per day is suggested. A trial examining non-algal diet supplements suggest a mixture of yeast and lipid emulsion may have some potential value. Photoperiod manipulation did not effect the reproductive condition of Perna canaliculus. The yield of veliger larvae was significantly enhanced if embryo culture water was treated with 1.0 mg/l EDTA. Veliger yield was not significantly affected at densities below 50 embryos/ml. Perna canaliculus larvae grew most rapidly and survived well at the salinity of 35 ppt. Larvae grew most rapidly when cultured at low densities. Experiments suggest that early larvae can be cultured at 5-10/ml, however late stage larvae grew most rapidly when cultured at l/ml. Perna canaliculus larvae displayed best growth and good survival if fed a mixed flagellate-diatom diet comprising Isochrysis galbana (T-Iso) and Chaetoceros calcitrans. The optimal diet ration, as a function of larval size, increased from about 20 cells/μl Isochrysis galbana (T-Iso) to around 150 cells/μl through the larval development period. Thyroxine between the concentrations of l0-5 and l0-8 M did not have an observable effect on larval developmental rate or eye spot development. Down welling settlement systems were found to be generally successful for Perna canaliculus lanrae. L-DOPA was also demonstrated to enhance the settlement and metamorphosis of Perna canaliculus pediveligers.

Whole document restricted, see Access Instructions file below for details of how to access the print copy. / In 1986 the New Zealand system of fisheries management was reformed. The Quota Management System (QMS) augmented the existing input control regulatory instruments with a system of output controls: individual transferable quota (ITQ). This thesis examines a number of aspects of the QMS in the context of a case study of the SNA1 snapper fishery. The QMS model is contrasted with a dynamic optimization model of rights based fishing which shows the effectiveness of ITQ systems in resolving the open access problem and that proportional share ITQ prices potentially contain information about the biological and economic state of a fishery. Departures of the QMS from the theoretical model are noted, particularly the allocation mechanism, the continued application of open access input control apparatus, and the basis of total allowable catch definition. Input control is considered in a bioeconomic model of the Hauraki Gulf sub-stock of the SNA1 fishery that features a sea surface temperature recruitment sub-model. Changes to the minimum legal size regulation (MLS) and the effect of differing inter-temporal recruitment structures on rent generation are evaluated. The biological and economic inefficiency of size regulation and the unequal distribution of risk between sectors in this fishery under the current management regime are demonstrated. The potential role for discount rates as performance indicators is shown. An intra-cohort stock externality due to growth overfishing is evident. The productive capacity of the SNA1 fishery system is presently not fully utilized. Output control is examined through time series analyses of prices in SNA1 ITQ markets. To date government has relied on the results of stock assessment research when setting the allowable harvest and monitoring the performance of fisheries policy. Excessive reliance on biological data, in particular modelling outputs, has attracted criticism. An alternative, a minimum information system uses information contained in quota prices as indicators of the biological and economic health of a fishery. SNA1 quota ownership and lease markets are found to exhibit the characteristics of weak form efficiency. Prices reflect expected rents in the fishery. However, at this stage of their development prices also reflect firms' uncertainty over expectations of fishery management agency behavior. Concern has been expressed that ITQ systems may be compromised by market failure through the exercise of market power. Evidence of market power is found in the SNA1 market for ITQ lease title. Explicit non-commercial quota, a review of the effectiveness of remnant pre-QMS regulatory instruments, and a substantial role for economic information in the total allowable catch setting process and as performance indicators form the basis of recommendations for policy.

The marine pulmonate limpet Siphonaria Zelandica is commonly found in the mid-eulittoral zone in shallow pans or rock pools with dense algal growth. Though it resembles a true limpet externally, it is active when emersed during the ebbing of the tide browsing on small succulent algae, rather than grazing the surface film. The structure and function of the digestive and respiratory systems of Siphonaria were studied, particularly in relation to its adaptations to the intertidal mode of life. The digestive system is relatively simple consisting of a large buccal mass with paired salivary glands, a spacious esophageal crop, a slightly muscular stomach with two digestive diverticula and a simple intestine-rectum. The arrangement of the 28 muscles of the buccal mass and the odontophore is typical of patelliform pulmonates. The radula is a broad sheet with 144 ± 31 rows of teeth, each row having a tooth formula of (18±4) + (18±3) + (1) + (18±3) + (18±4). The radular teeth are continuously produced at a rate of 4.9 rows per day similar to those of active feeding herbivorous gastropods. The characteristics of the teeth and the movement of the mouth and the feeding traces showed that the feeding processes do not involve rasping of a hard substratum but browsing and scooping of soft lush algal growth. The whole alimentary tract is lined by ciliated columnar cells of a basic form but with slight structural variations in different region. Those in the oesophagus and stomach contain apical vesicles and lysosome-like bodies indicating involvement in intracellular digestion, while those in the intestine contain various amounts of lipid and glycogen, functioning in active absorption and storage. The ciliated cells of the post-intestine, having a much folded basal plasma membrane are apparently involved in osmoregulation. The proteinaceous secretory cells in the crop and mid-intestine and the glycoprotein cells in the pro-intestine are either producing enzymes for extracellular digestion or secreting the faecal-binding sheath. Mucous cells interspersed among the ciliated cells of the oesophagus intestine and rectum produce mucoid material for lubrication and transport of food particles. The cuticular strip in the anterior chamber of the stomach, probably a vestigial gastric shield consists of tall non-ciliated cells with thick microvilli embedded in a dense fibrous matrix. The salivary gland contains six cell types: grain cells, duct mucocytes, mucocytes I and mucocytes II, duct ciliated cells and undifferentiated cells. The first four are secretory, the grain cell being serous secretory and the other three muciparous, with varying amounts of mucopolysaccharides. The tubules of the digestive gland are made up of five cell types, acinous digestive cells, neck digestive cells, crypt cells, vacuolated cells and undifferentiated cells. Both types of digestive cells participate in absorption and digestion. The high lipofuscin content in the neck digestive cell suggests its possible role in lipid digestion. The crypt cell with elaborate GER whorls and proteinaceous globules is apparently secretory, producing enzymes for extracellular digestion. Apocrinal secretion of the globules from the crypt cells was observed for the first time. The vacuolated cells appear to be degenerated crypt cells with an excretory function. The digestive gland tubule was found to undergo cyclic changes, correlated with the feeding activity which is related with the tides. Enzyme assays showed the presence of various carbohydrases, proteolytic and lipolytic enzymes in the different region of the digestive system. The digestive gland is the main site of enzyme production. The pH optima of amylase, laminarinase and sucrase from various regions of the digestive tract were found to be within the pH range of the alimentary tract. The activities of various enzymes in the salivary gland and the oesophagus but not digestive gland were synchronous and correlated with feeding. When emersed, Siphonaria respires atmospherically with the pneumostome wide open, and the mantle cavity functioning as a lung without any active ventilatory movements. When submerged, the mantle cavity is filled with water, a strong water current through the gill being created by the ciliated dorsal and ventral raphe behind the gill. The available respiratory surfaces include the sides of the foot, the anterior mantle roof and the single plicate gill. All these are lined by a thin epidermis with large blood spaces beneath it the non-ciliated epidermal cells in different regions carry different lengths of microvilli, apparently related to the degree of their protective role. The respiratory physiology of Siphonaria was also studied. No tidal or diurnal rhythm in oxygen consumption was revealed. In unagitated conditions the aerial respiratory rate was much higher than the aquatic rate but with agitation, the aquatic rate increased to near the aerial rate. Cutaneous respiration constituted about 25% of the total. The respiratory rate varied with body weight, the coefficient b being temperature-independent (0.791 ± 0.122). Both aerial and aquatic respiratory rates increased with temperature. The highest temperature-sensitive range was 10-25°C in winter and 15-30°C in summer which coincided with the normal environmental temperature. No seasonal temperature acclimation was found within the normal thermal range. Respiratory pigments haemocyanin and myoglobin were detected in the blood and buccal mass respectively. Their characteristics were studied and their role in oxygen transfer system was postulated. The reverse Bohr shift of the haemocyanin may facilitate oxygen uptake in the lung during burses of activity at low tide. A high oxygen-combining capacity of the buccal mass myoglobin (21.2 vol%) indicated a role of oxygen storage during bursts of feeding activity. The distribution of carbonic anhydrase in various tissues was consistent with a transfer system facilitating the release of metabolic CO2 from the buccal mass. Finally the phylogenetic relationships of Siphonariidae with other groups of marine pulmonates were discussed. The unspecialised digestive system, the advanced form of nervous system and the possession of a secondary gill suggest that Siphonariidae, as a family, may not be an advanced derivative of any of the more primitive living basommatophoran groups, but could represent, along with the Gadiniidae, a specialized group which has originated directly from a primitive pulmonate stock and are adapted to life on exposed rock shores.