The characterisation of the universal features of intertidal zonation on rocky coasts (Stephenson and Stephenson 1949; 1952; 1954; 1961) has stimulated many attempts t o explain the factors responsible for the observed patterns of distribution. Initial investigations which were essentially confined to the effects of a single factor upon different species suggested that ecological position was often correlated with physiological response. Recent studies have indicated that the subtidal distributions of algae show characteristic patterns (Kitching 1941 ; Bergquist 1960; Kain 1960; 1971; Morgans 1961 ; McLean 1962; Schwenke 1966; Neushul 1967; Clark and Neushul 1967; Larkum et al.1967; John 1971). However, there have been relatively few attempts to examine in detail and subsequently integrate the physiological response to environmental factors of major belt-demarcating algae of the sublittoral . The four New Zealand species of Carpophyllum are inhabitants of the uppermost sublittoral and the sublittoral fringe (Bergquist 1960; Dromgoole 1965). This particular study was undertaken in an attempt to elucidate the subtle differences in response which determine the distribution limits characteristic of each species. There is little information on the biology of Carpophyllum with the exception of some anatomical and embryological work (Delf 1939; Dawson 1940; Naylor 1954) and an earlier investigation of C. maschalocarpum (Dromgoole 1965). Thus to provide a basis for physiological experiments preliminary studies were directed to the following aspects: ( i ) a brief review of the morphology, anatomy and taxonomy of the genus, ( ii ) growth of sporelings in laboratory culture using various seawater media, ( iii ) definition of the geographical and vertical limits of the four species and a general study of their ecology with emphasis on population distributions, periodicitiy of reproduction and plant composition in relation to environment. The physiological response of algae to environmental factors has been examined by previous workers at the protoplasmic level using the criterion of resistance (e.g. Biebl 1956, 1962; Kanwisher 1957); at the metabolic level by measurement of photosynthesis and respiration (e.g. Chapman 1961n) ; and at the level of the whole plant by growth rates in laboratory cultures (e.g. Kain 1965) or of selected individuals in the field (e.g. Klugh and Martin, 1927). Attempts to culture Carpophyllum were not entirely successful. An earlier investigation indicated that the growth rates of Carpophyllum in situ are difficult to assess (Dromgoole 1965) and hence the metabolic approach, which does allow some integration of response to several factors by means of carbon balance calculations (e.g. Brown and Johnson 1964), has been used extensively in this study. The metabolic activity of large brown algae varies considerably with age and part of plant (Clendenning and Sargent 1957a, b; Chapman 1961a). To eliminate sampling problems in Carpophyllum a cuvette allowing continuous long-term monitoring of oxygen exchange of a single piece of material was developed. This laboratory apparatus has shown that the photosynthesis and respiration of the various organs is sensitive to environmental changes in pH, C02 supply, oxygen tension, light , water flow, dehydration and temperature. The nature and possible causes of the response t o each factor were examined in detail as this was considered essential to any interpretation of their ecological significance. Finally, the information obtained from these gas exchange measurements has been integrated by means of metabolic balance calculations and a descriptive synthesis of field and laboratory results has provided a general picture of the biology of these plants.

The scope of the present work is the systematic revision of the Demospongiae of the N.Z. region, here defined as including North and South Is. and all outlying islands as far north as Three Kings and South to Auckland and Cambell Is. The Kermadec Is. are not considered as part of the N.Z. region, but the sponges recorded from these islands are revised in the sytematic account. At present, 243 species of Demospongiae are recorded for this region, these belonging to 124 genera and 35 families. Of this total 49 species have been described as new and forty-six species are recorded as new to the fauna in this work.

The humpback whale was almost driven to extinction by commercial whaling in the Southern Ocean. Little is known about the degree of interchange among the remaining Southern Hemisphere populations. This thesis aimed to assess the connectivity among breeding grounds, feeding areas and migratory corridors of humpback whales using mitochondrial and nuclear DNA markers. The population structure of humpback whale populations in breeding grounds across the South Pacific and eastern Indian oceans was investigated, with an interest in the origins of whales in eastern Polynesia, using an extensive collection of mitochondrial DNA (mtDNA) sequences (n = 1,112; 470 base pairs in length). Samples were obtained from living whales at six breeding grounds: New Caledonia, Tonga, Cook Islands, French Polynesia (Society Islands), Colombia and western Australia. We found significant differentiation, at both the haplotype and nucleotide level, among the six breeding grounds (FST = 0.033; ΦST = 0.022) and for most pair-wise comparisons. The differentiation of the eastern Polynesia humpback whales is consistent with the hypothesis of a relic subpopulation, rather than vagrancy or colonization from known neighbouring breeding grounds. Regardless of their origin, it seems probable that islands of eastern Polynesia are now the primary breeding grounds for humpback whales feeding in the management Area VI (170°W – 120°W) of the Antarctic, as defined by the International Whaling Commission. A population of humpback whales migrates along the western South American coast, with breeding grounds mainly off Colombia and Ecuador and feeding areas off the western coast of the Antarctic Peninsula and in the channels and fjords ofsouthern Chile. We analysed the genetic relationship between humpback whales from these two summer feeding areas of the eastern South Pacific population to assess the potential heterogeneity in the migratory pattern of the population. We compared mitochondrial DNA control region sequences from 132 whales from the Antarctic Peninsula and 52 whales from the Magellan Strait areas. An AMOVA showed significant differences between the two feeding areas (FST = 0.180; ΦST = 0.169). A phylogenetic analysis showed both areas are represented in the AE clade that is only found in the Southern Hemisphere in the Colombian breeding ground. Genetic and previous demographic data (based on photo-identification) strongly suggest that both feeding areas are related to the same breeding ground but that heterogeneity exists among the feeding areas of this population, similar to that observed in the North Pacific and North Atlantic populations of humpback whales.Humpback whales migrating through eastern Australia and New Zealand have been linked with those breeding off northeastern Australia, New Caledonia, Fiji and Tonga, forming a single stock (Breeding Stock E). We investigated the relationship between the New Caledonian and Tongan breeding grounds, based on interchange of individual whales (genetically identified) and population genetic differentiation (mitochondrial DNA control region sequences and nuclear DNA microsatellites). We found significantly higher recapture probabilities within each breeding ground compared to the recapture probability between them using genetic identification, and significant differences at the population level in the FST and ΦST for mitochondrial and nuclear markers. These analyses suggest differentiation among the Breeding Stock E, supporting a proposed sub-stock division for New Caledonia (E2) and Tonga (E3). Historically, humpback whales off New Zealand coasts were caught during their migratory journeys between Antarctic feeding areas and tropical breeding grounds in the South Pacific. Here we investigated the genetic diversity of New Zealand humpback whales, comparing mitochondrial DNA control region sequence data with that from breeding grounds across the South Pacific (New Caledonia, Tonga, Cook Islands, French Polynesia and Colombia) and eastern Indian (western Australia) Oceans. We analyzed 30 samples collected around New Zealand, revealing 20 haplotypes. All haplotypes were found in New Caledonia and some were also found in other breeding grounds. New Zealand humpback whale haplotype diversity and nucleotide diversity were similar to those from the compared breeding grounds, but were significantly different at haplotype level from the Cook Islands, French Polynesia and Colombia breeding grounds. We found significant differences at haplotype level with the same three locations when a pair-wise AMOVA was performed. Three breeding grounds (western Australia, New Caledonia and Tonga) did not show significant differences at either nucleotide or haplotype levels. This genetic evidence and the available demographic data suggest a closer relationship of the New Zealand stock with New Caledonia and to a lesser extent with Tongan whales, supporting New Zealand as a primary migratory corridor for the humpback whales breeding in these western Pacific Islands.

This thesis examined the relative importance of natural and human influences to the population and assemblage dynamics of reef fishes in northeastern New Zealand. In particular, how different reef fishes responded to the implementation of no-take and partial marine reserve protection, and physical factors responsible for spatial differences in fish abundance. Included were data from prior to the establishment of a no-take marine reserve, multiple fished reference locations, biannual sampling and the use of two independent methods to provide quantitative estimates of fish abundance and size. This combination of factors is rare in studies of marine reserves was an important strategy leading to an improved understanding of the mechanisms structuring fish communities. Responses of the reef fish assemblage to changes in fishing mortality were examined at the Poor Knights Islands Marine Reserve. Full no-take marine reserve protection was implemented on the 1st Oct 1998 but for the prior 17 years, the Poor Knights Reserve comprised only two small no-take zones and allowed recreational fishing in the rest of the reserve. Following implementation of no-take marine reserve status the reef fish community changed rapidly; there were no obvious changes at either reference location. Species targeted by fishers, such as Pagrus auratus (snapper) and Caprodon longimanus (pink maomao), responded most strongly to protection. An increase in the density of some non-targeted species can probably be attributed to climatic effects, rather than a reduction in fishing pressure. A decline in the abundance of several species at the Poor Knights may have been a result of natural mortality, or competitive or predatory interactions with snapper. Along with human influences (fishing), physical variables are important in determining the distribution and abundance of reef fish. Four locations (two mainland and two island) were surveyed in northeastern New Zealand to determine spatial patterns for seven labrid species, one of the most abundant and widespread taxa of reef fish in New Zealand. The underlying mechanisms were then explored through an examination of the relationship between swimming ability (as examined through pectoral fin morphology), exposure and depth. Each of the four locations consistently displayed distinct labrid assemblages, likely due to the influence of the East Auckland Current. Regardless of location, there was a consistent depthrelated trend for most labrids and a trend for some species to be associated with certain levels of wave exposure. By analogy with tropical labrid assemblages, it was expected that there would be a clear relationship between pectoral fin aspect ratio and depth and/or exposure. However, this relationship was not strongly evident suggesting that wave exposure may not be as important for labrids on northeastern New Zealand reefs as hypothesised for tropical coral reef systems. The response of snapper, an important recreational and commercial finfish, was investigated following the cessation of all fishing at the Poor Knights. The rate of response of snapper to protection was rapid, in areas that had previously been partially protected as well as in those that had been fully protected from fishing, with the overall density of legal sized fish increasing by 7.4 times over 4 years, likely a result of recolonisation rather than recruitment. The 818% increase in snapper biomass has the potential to enhance areas outside or within the reserve through the export of biomass (eggs and/or larvae and adults) - the daily batch fecundity was 11 to 18 times higher at the Poor Knights compared to the reference locations. The effects of partial protection on reef fish were further examined at the Mimiwhangata Marine Park, an area where recreational fishing is permitted but all commercial fishing has been prohibited for 18 years. Snapper showed no difference in abundance or size between the Mimiwhangata Marine Park and adjacent control areas, with the density of snapper most similar to fished reference locations. The lack of any recovery by snapper within the Marine Park, despite the exclusion of commercial fishers and restrictions on recreational fishing, and results from the Poor Knights, indicates that partial fishing regulations are ineffective as conservation tools for protecting targeted species or for fish communities in general (i.e. through reduction in by-catch). Results from this study provide evidence that recreational fishing has significant impacts on reef fishes.

Bottlenose dolphins (Tursiops truncatus) are frequently brought into contact with humans, due to their coastal habitat use. Over the last decade there has been considerable growth in the commercial dolphin-based tourism industry. This growth exposes coastal populations to boats and swimmers. New Zealand has allowed commercial operations offering swimming with wild dolphins since 1989. Little is known about the effects of boats and swimmers on dolphin behaviour. The present study examines a population of bottlenose dolphins that utilise the Bay of Islands as part of their range along the northeastern coast of New Zealand, and their behavioural response to commercial swim-with-dolphin operations. Data were collected from an independent research boat and the commercial dolphinwatching boats from December 1996 to February 2000. Photo-identification showed a closed population of 446 (95% C.I. 418-487) dolphins, with an 81% resight rate of the 378 catalogued individuals. Group size ranged from 2 – 50 dolphins, with 80% of groups (n = 160) containing 2 - 20 dolphins. The number of groups with calves present increased from 32% (n = 17) in 1997, to 63% (n = 47) in 1999. This could be explained by the increased number of neonates born; from four in 1997, to nine in 1999. Photo-identification in areas outside the Bay of Islands showed that individuals ranged minimum distances of 82 km north, and 388 km south of the Bay of Islands. All photographs taken outside the Bay of Islands were matched to known animals, suggesting that the majority of the northeastern coastal population is seen in the Bay. With the next nearest population of bottlenose dolphins approximately 1,000 km south, these dolphins probably form an isolated population ranging along the east coast of the northeastern North Island. Habitat use by the dolphins was examined using Geographic Positioning System (GPS) points simultaneously linked to behavioural states. In total, 31 groups were followed, and 847 GPS points were recorded. Position of initial encounter was recorded for 138 groups of dolphins. There was a significant correlation between water depth and sea-surface temperature, with dolphins found in deeper waters in summer when water temperature was highest, and in shallow waters in winter when the water temperature was lowest. Only one behavioural state, slow travel, was significantly different by season. Although all behaviours were observed in all zones, dolphins had preferential habitat use throughout the four zones within the Bay. To determine the level of impact on dolphin behaviour due to boat traffic, focal-group follows using a scan sample methodology were conducted from an independent research boat. A CATMOD analysis was used to determine dolphin behaviour by season, number of boats, and group size. Dolphin behaviour differed by boat number; in particular, resting behaviour decreased as boat number increased and milling behaviour increased as boat number increased. Behaviour differed when the research boat was the only boat present. Closer examination of boat type, i.e., permitted dolphin watching boats, non-permitted tour boats, and recreational boats, found a difference in dolphin behaviour in the presence of the permitted boats when compared to the other types. Dolphins rested less and engaged in more milling behaviour when the permitted boats were present. Responses to swim attempts from the commercial boats were compared from 1994 - 1995 to 1997 - 1998. In total, 255 groups were encountered of which 36% (n = 93) were exposed to at least one swim attempt. Successful swims (i.e., where at least one dolphin remained within 5 m of at least one swimmer) decreased from 48% in 1994 - 1995 to 34% in 1997 - 1998 and avoidance responses increased from 22% to 31%. Dolphin response varied according to swimmer placement from the boats. The ‘in path’ placement had the highest level of avoidance. Only ‘line abreast’ placement resulted in a decrease in avoidance. Based on the photo-identification sighting records, it was estimated that an average dolphin was exposed to 31 swim attempts per year. This suggests that individual dolphins have, with cumulative experience, become sensitised to swim attempts. If a swim attempt was successful, on average, it involved 19% of the group. Juveniles were more likely to interact with swimmers than adults. The present study suggests that the wide-ranging population of bottlenose dolphins that frequents the Bay of Islands is exposed to levels of tourism which can affect the dolphins behaviour. In particular, the permitted boats’ presence results in decreased resting behaviour by the dolphins. The apparent sensitisation of this population to swim attempts, and the relatively small number of individual dolphins that interact with swimmers, are grounds for concern about the long-term impact of interactions. Ongoing monitoring of this populations’ response to swimmers and boats, combined with a precautionary approach to management of boats and swimmers, are recommended.

This thesis uses molecular genetics as a tool to uncover information about the population structure and genetic variation in Hector’s dolphin (Cephalorhynchus hectori), to track population declines and to assess the evolutionary origins and taxonomic status of this species. A high-resolution genetic analysis of population structure was considered important for the determination of population boundaries and delimitation of conservation management units due to potentially unsustainable fisheries-related mortality. Population structure and dispersal rates were assessed using 281 samples collected from individual Hector’s dolphins of ten population groups representing the known geographic range of this species. Variation among mitochondrial DNA sequences (ΦST = 0.545) and microsatellite allele frequencies at six loci (RST = 0.252) indicated the presence of four genetically isolated regional populations, North Island (n = 29), East Coast South Island (n = 110), West Coast South Island (n = 122) and South Coast South Island (n = 19). Significant levels of genetic differentiation were not detected within local sub-populations of the East Coast and West Coast regional populations. However, the estimated geneflow between these sub-populations fitted a one-dimensional stepping-stone model (r2 = 0.6225) suggesting a vulnerability of local populations to fragmentation. A measure of expected mtDNA diversity (Tajima’s D statistic) suggested decline in eight of the ten populations. Microsatellite heterozygosity was also lower than expected in the East Coast and North Island regions, suggesting either further regional sub-structuring (Wahlund effect), loss of diversity due to population decline or the presence of null alleles. Examination of all Hector’s dolphin museum specimens of known origin (n = 55) enabled comparison of historic (1870 - 1987) genetic diversity to contemporary (1988 – 1999) diversity in two regional populations to assess the possibility that these populations have undergone recent declines. Over the last 20 years the North Island population has been reduced from at least three lineages (h = 0.41) to a single lineage (h = 0, p < 0.05). The diversity of the East Coast, South Island population has declined significantly from h = 0.65 to h = 0.35 (p < 0.05). These results suggest that the low abundance currently observed is due to recent population declines and that the North Island population is threatened with extinction in the near future. Based on a trend analysis of the mtDNA, it can be predicted that the East Coast South Island population may lose all mtDNA diversity within the next 20 years. Alternatively, detection of a one dimensional dispersal pattern may indicate that some populations are at risk of extirpation while others may not be in decline. If this is the case then the East Coast regional population is at risk of fragmentation. On a wider evolutionary scale, Hector’s dolphin is one of four species of the genus Cephalorhynchus, all of which suffer fisheries–related mortality. To describe the origin and radiation of these species, 485 bp of the mitochondrial DNA control region was sequenced from 320 individuals (including previously sequenced 200 Hector’s dolphins) representing nine of the ten species in the sub-family Lissodelphininae. The hypotheses that either Cephalorhynchus is a monophyletic genus or that the four species have arisen separately from pelagic Lissodelphine species and have converged morphologically were tested. The mtDNA phylogeny supported the monophyly of the genus and suggested that the genus Cephalorhynchus originated in the waters of South Africa and, following the West Wind Drift, colonised New Zealand and then South America. Secondary radiations resulting in two genetically isolated populations were found for the Kerguelen Island Commerson’s dolphin and the North Island Hector’s dolphin. A comparison of the genetic differentiation between the Commerson’s dolphins of the Kerguelen Islands (n = 11) and the coast of South America (n = 35), and between the North Island (n = 14) and South Island (n = 185) Hector’s dolphins, was conducted in order to assess the conservation and taxonomic status of these populations. A single fixed substitution in the mtDNA control region was diagnostic for the Kerguelen Island compared to South America (FST = 0.306, ΦST = 0.602) and the North Island compared to the South Island (FST = 0.442, ΦST = 0.495). Population differentiation of four microsatellite alleles (including unique alleles in each of the four populations) between the Kerguelen Island and South American Commerson’s dolphin (FST = 0.036, RST = 0.0493) and between the North and South Island Hector’s dolphins (FST = 0.391, RST = 0.3197) indicated restricted nuclear as well as maternal geneflow. These data, combined with additional evidence of morphological and geographic isolation, indicated that the Kerguelen Island Commerson’s dolphin and the North Island Hector’s dolphin are likely to be reproductively isolated from their alternate con-specific populations. Examination of various species concepts and definitions of conservation units leads to the conclusion that these four populations should each be considered unique at the subspecies level for the purposes of management, protection and evolutionary potential. These results lead to the conclusion that the Hector’s dolphin consists of highly subdivided populations. As a result of this and a low reproductive potential, Hector’s dolphin populations are vulnerable to extirpation through even low levels of human induced mortality. To manage such populations, it is appropriate to consider each of the two islands as separate sub-species. Within the South Island, the populations may be further subdivided into three demographically independent Management Units – the East, West and South Coasts. The South Coast management unit is vulnerable due to its low abundance and isolation and requires further investigation. Population modelling will need to reflect the fact that the local populations within the East and West coast regions share only limited dispersal with immediately adjacent populations and are thus susceptible to fragmentation. These results also show that the population declines of the East Coast South Island and the North Island populations are of recent origin thus implicating fisheries-related mortality as the principal threat to Hector’s dolphin. To prevent further decline or fragmentation of South Island populations more stringent control of inshore gillnet fisheries is required. By contrast, current decline of the North Island population may be a result of inbreeding depression. Given the low abundance and rapid decline of the North Island population, it is imperative to evaluate the potential for inbreeding depression while continuing to mitigate all human-related threats.

Broadcast spawning marine invertebrates have been widely used as model organisms to study processes of evolution. One of these is the study of various life history stages associated with reproduction. Fertilization ecology in broadcast spawning marine organisms, i.e. the process by which sperm and egg fusion occurs once released into the ocean, has been the subject of intensive study for roughly the last 20 years, and represents thus a recent field in ecological sciences. This growth in interest was sparked by studies that showed spawning events may take place predominantly under sperm limiting conditions. More recent findings however, suggest that the occurrence of sperm competition, and the risk of polyspermy (multiple sperm entry in to the egg, which is lethal in echinoderms) can also occur during reproductive events in marine invertebrates. This has also been predicted on theoretical grounds. Even though polyspermy has been observed previously, particularly during aquaculture studies, evidence to assess the occurrence of polyspermy in situ, and the conditions under which it occurs is lacking. Simulated field studies in Evechinus chloroticus as well as laboratory studies in E. chloroticus and Coscinasterias muricata found high levels of polyspermy, even under the sperm limiting conditions that are naturally found in the field in other marine broadcast spawners. Furthermore, laboratory results in both Evechinus and Coscinasterias showed that polyspermy is most likely to increase when sperm concentrations are increased. In addition, even though increasing sperm concentrations increases monospermy to a certain extent, an increase in gamete contact times generates similar levels of monospermy. Results from these studies confirmed the mathematical model predicting some of these events. The timing of gamete release to achieve maximum fertilization success (monospermy) in a broadcast spawner is thought to be under strong selective pressures, because reproductive success is directly related to fitness. The spawning patterns in the sea urchin E. chloroticus observed in this study demonstrated that E. chloroticus spawns under varying environmental and ecological conditions. Interestingly, it appeared that highly synchronous and widespread spawning was found to occur when highly turbulent conditions existed. This may reduce the potential for polyspermy that may exist during mass spawnings under shallow and calm conditions. The demonstration of polyspermy and the confirmation of the mathematical model, suggest that polyspermy is a common and frequent occurrence during broadcast spawning events. Thus polyspermy represents an evolutionary force that may shape the evolution of reproductive phenomena at levels ranging from the gamete to the population.

Various aspects of metabolism and physiology were investigated during the ontogeny of yellowtail kingfish (Seriola lalandi), a fish of growing aquaculture importance in both New Zealand and other countries. Incubation experiments between 18-24°C showed that developing eggs and larvae were heavily influenced by temperature. It appeared that at warmer temperatures larvae hatched smaller but grew on the yolk sac, whereas at cooler temperatures larvae grew inside the chorion. Oxygen consumption data supported this, with a negative correlation found between total embryonic oxygen consumption and temperature. A mechanism was proposed to explain the differential effect of temperature on ontogeny and growth. Like other marine fish with pelagic eggs, yellowtail kingfish were found to be heavily reliant on free amino acids as a source of energy. At 23°C the pattern of substrate utilisation in eggs was considerably different from that at 17-21°C, indicating that 23°C exceeded the tolerance for normal development. Inter-individual aggression by large individuals was associated with the development of size heterogeneity in juveniles. Although this aggression also affected the survival of smaller juveniles, it was not the primary agent of much of the mortality that occurs during this phase, as many of these individuals were on a degenerate developmental trajectory. Yellowtail kingfish fingerlings used for ongrowing were robust to the stressors imposed by live transport. The ontogenetic development of metabolic rate from 0.6 mg-2.2 kg did not follow the same scaling exponent as that observed for mammalian models of allometry, and has implications for interspecific studies of mass-dependent metabolism.

The Chilean oyster, Tiostrea chilensis, is a commercially important species that is native to New Zealand and the Pacific Coast of South America. The description of the variability in life history characteristics among populations of the Chilean oyster is fundamental to understanding its biology and may help in solving some of the problems encountered in culturing this species. Research presented in this thesis describes some aspects of the reproductive biology of the Chilean oyster from four populations, mainly in northern New Zealand, and compares the results with previous studies from elsewhere. Similar patterns of gametogenesis were found among three study populations at Manukau Harbour, Hauraki Gulf and Foveaux Strait. Oysters were protandrous, maturing firstly as males and later also producing ova. In all three populations the majority of the contents of all the gonads were male reproductive products. There was no evidence that the sexuality of oysters alternated rhythmically as has been reported in other species of larviparous oysters. For spawning females, the often concurrent release of ripe sperm indicated the possible presence of self fertilisation. In samples of oysters examined from Foveaux strait the sexuality of oysters was found to change markedly with size. This suggested that the infection of oysters by the parasite Bonamia may not be related to their sexuality as was previously thought. At two northern populations (Hauraki Gulf and Manukau Harbour) larvae were produced from young, small oysters, and a much larger proportion of the population was brooding larvae each year than has been reported elsewhere. In both populations, larvae were being brooded, released and were settling at all times of the year, unlike other populations. The mean fertility of the Manukau Harbour oysters was the highest so far reported for any population of this species. The size of larvae in all three northern populations were smaller than has been reported for all other locations in New Zealand and chile and is thought to be related to differences in water temperatures. Overall, the results highlight the importance of investigations into populations of molluscs across their geographical range for revealing variation in life history characteristics which may be of benefit for aquaculture. / Whole document restricted, but available by request, use the feedback form to request access.

The tellinid bivalve, Macomona liliana, is important to the structure and organisation of intertidal sandflat communities in Manukau Harbour. This thesis reports on features of the reproductive, larval supply and recruitment biology of Macomona liliana in relation to environmental factors in the harbour. Macomona liliana is gonochoric. In a mid-tide population sexual maturity occurred in animals ≥ 22 mm (shell length). Spawning is asynchronous and protracted from late November to March throughout the harbour and timing of the reproductive cycle is associated with seasonal changes in environmental variables: temperature, salinity and seasonal production of phytoplankton and benthic microalgae. A visual gonad index was useful for establishing the main periods of spawning activity. Favourable habitats are at mid-tide on the large exposed sandflats characterised by well sorted fine sands. Less favourable habitats are in sheltered bays characterised by moderate-poorly sorted sands. A delay in the onset of gametogenesis in small compared to large adults (July-August of. May-June) indicates size and/or age dependent resource allocation to growth and reproduction. Adult size classes are evenly represented in favourable habitats whereas in less favourable habitats size classes are dominated by small adults. Favourable habitats have an equal sex ratio or are biased towards females whereas in less favourable habitats the converse is true. Early life-history stages are described and techniques employed to facilitate their identification in plankton and sediment samples. A spatial Taylor's Power Plot (slope, b = 1.31) demonstrates thorough mixing of larvae in the main channels. Spatial autocorrelation models confirm that densities of larvae are higher to the south of Karore Bank than to the north. The recruitment period is December to early March but varies between successive years. Physical transport processes, post-settlement migration and high levels of mortality in Boccardia syrtis tube-mats dominate recruitment patterns in the high energy environments. Larval supply and active habitat selection by settling larvae may, however, be significant determinants of population structure in sheltered bays. Generalisations are made on the effect of habitat quality on the reproduction and recruitment biology of the Manukau Harbour metapopulation.