Biofouling is a substantial problem for the maritime industry. Organisms growing on underwater surfaces increase drag on ships’ hulls and damage coastal machinery. Billions of dollars are spent annually on mitigating fouling. The tropical barnacle (Balanus amphitrite) is a major fouling species. This thesis investigates the effects of some of the major environmental controls for this benthic species, (surface chemistry, temperature and food availability), on the adhesion and adhesives of two of its life cycle stages, the settlement-stage cypris larva (the final larval stage of barnacles) and the adult.

The salmon louse Lepeophtheirus salmonis (Krøyer, 1837) (Copepoda; Caligidae) is a serious pathogen of wild and farmed salmonids in the marine environment. A study has been carried out to investigate the biology and behaviour of the infective copepodid stage of this parasite. Copepodids showed a positive phototactic response to a wide spectrum of light wavelengths (300 - 700 nm) with a peak response at 550 nm. Light response was positively correlated to light intensity between 2.4 - 240 lux with immobilsation occurring at 20,000 lux. Copepodids demonstrated a negative geotactic response to increasing pressure. No positive chemotactic or rheotactic behaviour was demonstrated, although copepodids showed a rapid swimming and fast turning response to directed water flow that was considered to be the principal mechanism of host contact. Light and electron microscope studiesshowed copepodids to be equipped with a wide range of sensory organs including integumental organs, a lensed nauplius eye, an extra-optic photoreceptor (Organ of Gicklhorn), an Organ of Bellonci and antennular elements comprising mechanoreceptive and chemoreceptive components. A new receptor termed the "cauliflower organ" was also described and is suggested to function in host recognition. Primary attachment was shown to be accomplished through grappling of the host epidermis by the hooked antennae. The maxillpeds were used to further embed the antennae and anterior cephalothoracic shield. Secondary attachment was accomplished through the use of a frontal fiament. This was formed internally within the copepodid and may be renewed at each moult. Morphological and histochemical studies demonstrated the frontal filament to be a cuticular extension and showed it to comprise an adhesive "basal plate", a fibrous proteinaceous "stem" and an "external lamina" which was continuous with the cuticle of the anterior cephalothoracic shield. An "axial duct" ran through the stem and terminated at the basal plate. An external "filament duct" protruded from the copepodid rostrum and was continuous with the axial duct. Three major organs, A-, B- and C-glands, were described and their role in filament production discussed. A "ventral fiament organ" equating to the "frontal organ" of earlier studies was also present in the copepodid and subsequent stages. The copepodid alimentary canal comprised a cuticle-lined foregut, a midgut comprising anterior midgut caecum, anterior midgut and posterior midgut and a cuticle-lined hindgut terminating in a slit-like anus. The oral cone conformed to the normal caligid pattern although the labium and labrum were less tightly opposed than those of adults. The strigil was covered by a "labial bar". The midgut comprised three cell types corresponding to the B, RIF and E cells of earlier studies. The posterior midgut comprised only RIF cells. Faeces were enclosed in a peritrophic membrane. A number of glandular systems were present which were associated with the oral cone. These were termed "mucoid glands" "proximal gland complex" "labial gland" and "distal labral organ" respectively. No glands were observed to interface to the fore- mid- or hindgut. The free-living copepodid is believed to be lecithotrophic and was demonstrated to carry large vesicles within the epithelial cells of the midgut which are believed to comprise lipid reserves. The attached copepodid was seen to feed on mucus, epidermal I dermal material and other available host components. Host pathology was limited and comprised principally mechanical damage and tissue compression resulting from attachment and feeding. Host tissue response was limited to an increase in mucous cells and occasional influx of eosinophilic granular cells. Maximum survival of copepodids under optimal conditions in vitro was 23 days following moulting from the second nauplius stage. Survival was not increased by provision of fibrous substrates. Experimental host infections demonstrated that copepodids were host specific and failed to attach to non-salmonid species. Copepodids were demonstrated to infect both marine and freshwater host stages. In experimental infections, larvae were attached principally to the fins and gils. Farmed salmon showed attachment mainly to fins. Spatial distribution was suggested to be principally the consequence of local hydrodynamics. The negative correlation of relative density of infection with size in smolts and positive correlation in larger farmed fish was considered to result principally from differences in swimming-speed and surface area. Disadvantaged, mature and diseased hosts showed higher infection levels. Overdispersal of parasites was considered to be principally the result of host heterogeneity in experimental and farm infections. Attempts to determine the spatial and numerical distribution of copepodids in the wild were unsuccessful and this was suggested to result from the temporally discrete "waves" of infection seen on farmed fish. The results of this study were discussed with reference to studies of other parasitic and free-living copepod species and suggestions were made as to the implications of these findings for aquaculture.

The bottom grown mussel sector has been the most successful component of the aquaculture industry on the island of Ireland in terms of output since. The output from Irish mussel fisheries is however limited and in many areas the on-growing of seed mussels on bottom growing plots is inefficient with harvest to seed ratios falling below 1 :1. If zero mortality of seed occurred during the cultivation process however it has been calculated that a harvest to seed ratio of 8: 1 could be achieved. There is, therefore, a need to investigate aquaculture practices to ensure maximum returns at harvest are achieved from what is a limited natural resource. This thesis investigated how current aquaculture practices affect the survival rate of mussels with the aim to identify practices that ensure maximum yields are achieved from limited seed resources. As such this work investigated whether the process of mussels being transported from wild seed beds to ongrowing plots had a negative effect on the physiological health and resultant behaviour of mussels by simulating transportation conditions in a controlled experiment. Further to this I examined how stress, as induced be periods of extended aerial exposure, may alter the predator-prey relationships between both Carcinus maenas, Asterias rubens and M. edulis. Regardless of the effects of mussel condition and stress on subsequent predation rates C. maenas and, A. rubens have the potential to consume and thus remove a large number of mussels from the benthic cultivation process. The effectiveness of the use of crab pots and starfish mops at removing predators from mussel beds was therefore investigated

No description available.

The European lobster (Homarus gammarus) is an ecologically important benthic decapod which supports fisheries that are critical to the economic prosperity of coastal communities. However, populations across its range are pressured by rising exploitation, from which management has failed to prevent stock collapses in the recent past. Fisheries management of the species is significantly hindered by deficiencies in our knowledge of fundamental characteristics of population biology, including the connectivity and genetic diversity of stocks. As a result, the effectiveness of strategies designed to conserve recruitment and ensure harvests are sustainable is poorly understood. This thesis focuses on elucidating aspects of reproductive and molecular ecology in H. gammarus which can be used to inform and appraise conservation management initiatives, currently applied via both the regulation of capture and the wild release of hatchery-reared juveniles. The size-specific fecundity of reproducing females was defined around southwestern UK, and spatial variation in clutch size between populations was linked to a longitudinal gradient in oceanic temperature range across Northern Europe. The reconstruction of paternal genotypes show that single males fertilise individual clutches, which hints at demographic stability within a productive Atlantic fishery. Population genetic structure, investigated at a fine spatial scale in the same region, evidenced high connectivity and suggests that the localised interventions of an active hatchery do not lead to juveniles being released beyond areas they might naturally recruit via planktonic dispersal. However, genetic differentiation and isolation-by-distance at a broad geographic scale indicate that direct gene flow between remote populations is limited, so that (i) a failure to maintain spawning stock biomass may negatively affect local recruitment, (ii) the utilisation of non-resident broodstock for hatchery stocking may cause a loss of adaptive potential, and (iii) the recovery of depleted stocks is likely to be problematic. Finally, simulations indicated that genetic parentage assignment will prove accurate in distinguishing cultured individuals from natural stock among admixed populations in the wild, an important development that should facilitate the optimisation of hatchery stocking and lead to rigorous assessments of the conservation value of releasing lobsters reared in captivity.

Seaweed represents a valuable, underused sustainable resource. Current investment in seaweed farming will provide large quantities of biomaterial for a range of applications. The major focus of this thesis is on a class of polyphenols known as phlorotannin, of interest for their antioxidant and biomedical applications. Seaweed polyphenols have strong radical scavenging properties. Whilst there are many reported extraction methods for phlorotannin, it was not clear how different solvent systems affect the antioxidant capacity of the phlorotannin extracted. This work represents the first comparable study of its kind in which phlorotannin was isolated from seaweed using several extraction solvents and the antioxidant capacity evaluated using the DPPH radical scavenging assay. The structural profile and radical scavenging capacity of the phlorotannin did not change between the extracts. Water and ethanol-water mixtures were found to be the most suitable solvents for large-scale extraction of phlorotannin. The first study on the seasonal variation in phenolic content of industrially farmed seaweed grown on ropes was performed. The phenolic content of the two species studied, Fucus vesiculosus and Ascophyllum nodosum varied between 4-9 % dry mass and showed variation that could be attributed to the growth cycle of the seaweed. This demonstrates that the phenolic content is high enough all year round to allow viable extraction of phlorotannin. The radical scavenging capacity of Fucus vesiculosus was found to be 12% greater than Ascophyllum Nodosum. Given that the majority of farmed seaweed is destined for biofuel production, it was of interest to consider whether phlorotannin could be extracted during biofuel processing. A potential pre-treatment method proposed for processing seaweed for biofuel is the use of superheated water extraction. Phlorotannin was then extracted from superheated water, without impacting the radical scavenging capacity, demonstrating the potential for it to be integrated into future processing techniques.

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