http://hdl.handle.net/10023/178 Tue, 18 Jun 2013 06:24:45 GMT 2013-06-18T06:24:45Z http://research-repository.st-andrews.ac.uk:80/retrieve/285/Gatty.jpg http://hdl.handle.net/10023/178 http://hdl.handle.net/10023/2975 Abstract: 1. The anatomy and physiology of escape swimming behaviour in the squat lobster, Galathea strigosa, have been investigated and the results discussed in the context of comparative mechanisms of escape in rela~ed species. 2. In contrast to many other decapods, G. strigosa, does not possess a giant-fibre system which underlies escape. 3. In terms of the number, size and position of neuronal somata, the fast flexor motorneuron pools in Galathea and crayfish are homologous. 4. A neuron, homologous with the crayfish MeG, has been studied. Unlike the crayfish neuron, MoGH is a typical, unspecialized fast flexor motorneuron. 5. The anatomy of afferent and efferent neurons involved in abdominal extension has been investigated. The extensor motorneuron and accessory neuron pools in crayfish and Galathea are largely homologous. 6. A small degree of intersegmental and interspecific variation in abdominal flexor and extensor motorneuron pools is reported. 7. The anatomy and physiology of the abdominal MRO's has been examined. These are found to be homologous in structure and function with other decapod MRO's. 8. The considerable differences between the phasic and tonic MRO sensory dendrites may account for their different response characteristics. 9. The MRO's excite both extensor motorneurons and the flexor inhibitor motorneuron via an apparently monosynaptic pathway. Similar input properties have been described for the crayfish MHO's . 10. The MRO's, which are shown to fire in response to abdominal flexion, produce EPSP's in extensor motorneurons which both summate and facilitate. This feature has not been decribed previously and may be important in the reflex function of the MHO's during escape swimming behaviour. 11. The relative roles of proprioceptive and exteroceptive feedback on the generation of the swimming rhythm have been studied using a variety of preparations involving restraint and deafferenta- tion. 12. Sensory feedback both excites and inhibits swimming. It is deduced that proprioceptive feedback has excitatory effects and extero- ceptive feedback inhibits swimming behaviour. 13. It is suggested that the MHO's may playa role in exciting the neural circuits underlying swimming bewvbur via both direct connections with the thoracic nervous system and a restricted portion of the abdominal motorneuron pool. 14. A deafferented preparation has been used to analyse the motor programme underlying swimming behaviour. The ability to record swimming activity, identical with that recorded in the intact animal, in the absence of sensory feedback from the abdomen, suggests that swimming behaviour is controlled by a central pattern generator (CPG). 15. A method of inducing swimming activity by high frequency electrical- stimulation of abdominal sensori-motor roots is described. 16. The CPG for swimming behaviour is shown to be most likely to reside in the suboesophageal or thoracic ganglion. 17. The activity of flexor and extensor motorneurons in abdominal ganglia has been analysed at the cellular level using both extra- cellular and intracellular recording techniques. 18. Fast flexor motorneurons are driven by a combination of brief unitary synaptic potentials and a large underlying oscillatory slow wave depolarization. 19. Current injection into the somata of fast flexor motorneurons during swimming has dramatic effects on slow wave amplitude and suggests that motorneuron drive results from powerful periodic excitation via chemical synapses. 20. In contrast to the fast flexor motorneurons, fast extensor motorneurons are driven by only brief unitary synaptic potentials and not by an underlying slow wave depolarization. The contrasting mechanisms for excitation in antagonistic sets of motorneurons is documented and a possible explanation presented. 21. Among the fast extensor motorneurons there is an apparent gradation in spike thresholds which can be correlated with a gradation in soma diameter. The largest of the available pool of extensor motorneurons has the highest spike threshold. 22. The activity of the phasic inhibitors of the extensor and flexor muscles has been analysed. The extensor inhibitor, which fires in antiphase with other extensor motorneurons during the flexion phase of the swim cycle, appears to receive the same slow wave depolarization as fast flexor motorneurons. The extensor inibitor motorneuron burst is terminated by a high frequency barrage of IPSP's superimposed upon the membrane slow wave. The flexor inhibitor motorneuron receives complex excitation and inhibition during swimming, involving both unitary events and membrane waves. 23. The coordination of segmented limb structures during swimming has been investigated. The walking legs are physically protracted during flexion while the unmodified male swimmerets are flicked posteriorly. 24. Swimmeret retraction during swimming is controlled by the activity of a single swimmeret motorneuron which appears to be part of the swimming circuit and which may also be a primitive homologue of the Segmental Giant neuron in crayfish. 25. It is concluded that escape swimming behaviour is homologous with non-giant backwards swimming in crayfish and may also be homologous with swimming in certain sand crab species. The evolutionary relationships of a number of decapods is discussed on the basis of escape circuitry and it is suggested that Galathea may represent an ancestral type of swimming decapod. Sun, 01 Jan 1984 00:00:00 GMT http://hdl.handle.net/10023/2975 1984-01-01T00:00:00Z Sillar, Keith Thomas 1. The anatomy and physiology of escape swimming behaviour in the squat lobster, Galathea strigosa, have been investigated and the results discussed in the context of comparative mechanisms of escape in rela~ed species. 2. In contrast to many other decapods, G. strigosa, does not possess a giant-fibre system which underlies escape. 3. In terms of the number, size and position of neuronal somata, the fast flexor motorneuron pools in Galathea and crayfish are homologous. 4. A neuron, homologous with the crayfish MeG, has been studied. Unlike the crayfish neuron, MoGH is a typical, unspecialized fast flexor motorneuron. 5. The anatomy of afferent and efferent neurons involved in abdominal extension has been investigated. The extensor motorneuron and accessory neuron pools in crayfish and Galathea are largely homologous. 6. A small degree of intersegmental and interspecific variation in abdominal flexor and extensor motorneuron pools is reported. 7. The anatomy and physiology of the abdominal MRO's has been examined. These are found to be homologous in structure and function with other decapod MRO's. 8. The considerable differences between the phasic and tonic MRO sensory dendrites may account for their different response characteristics. 9. The MRO's excite both extensor motorneurons and the flexor inhibitor motorneuron via an apparently monosynaptic pathway. Similar input properties have been described for the crayfish MHO's . 10. The MRO's, which are shown to fire in response to abdominal flexion, produce EPSP's in extensor motorneurons which both summate and facilitate. This feature has not been decribed previously and may be important in the reflex function of the MHO's during escape swimming behaviour. 11. The relative roles of proprioceptive and exteroceptive feedback on the generation of the swimming rhythm have been studied using a variety of preparations involving restraint and deafferenta- tion. 12. Sensory feedback both excites and inhibits swimming. It is deduced that proprioceptive feedback has excitatory effects and extero- ceptive feedback inhibits swimming behaviour. 13. It is suggested that the MHO's may playa role in exciting the neural circuits underlying swimming bewvbur via both direct connections with the thoracic nervous system and a restricted portion of the abdominal motorneuron pool. 14. A deafferented preparation has been used to analyse the motor programme underlying swimming behaviour. The ability to record swimming activity, identical with that recorded in the intact animal, in the absence of sensory feedback from the abdomen, suggests that swimming behaviour is controlled by a central pattern generator (CPG). 15. A method of inducing swimming activity by high frequency electrical- stimulation of abdominal sensori-motor roots is described. 16. The CPG for swimming behaviour is shown to be most likely to reside in the suboesophageal or thoracic ganglion. 17. The activity of flexor and extensor motorneurons in abdominal ganglia has been analysed at the cellular level using both extra- cellular and intracellular recording techniques. 18. Fast flexor motorneurons are driven by a combination of brief unitary synaptic potentials and a large underlying oscillatory slow wave depolarization. 19. Current injection into the somata of fast flexor motorneurons during swimming has dramatic effects on slow wave amplitude and suggests that motorneuron drive results from powerful periodic excitation via chemical synapses. 20. In contrast to the fast flexor motorneurons, fast extensor motorneurons are driven by only brief unitary synaptic potentials and not by an underlying slow wave depolarization. The contrasting mechanisms for excitation in antagonistic sets of motorneurons is documented and a possible explanation presented. 21. Among the fast extensor motorneurons there is an apparent gradation in spike thresholds which can be correlated with a gradation in soma diameter. The largest of the available pool of extensor motorneurons has the highest spike threshold. 22. The activity of the phasic inhibitors of the extensor and flexor muscles has been analysed. The extensor inhibitor, which fires in antiphase with other extensor motorneurons during the flexion phase of the swim cycle, appears to receive the same slow wave depolarization as fast flexor motorneurons. The extensor inibitor motorneuron burst is terminated by a high frequency barrage of IPSP's superimposed upon the membrane slow wave. The flexor inhibitor motorneuron receives complex excitation and inhibition during swimming, involving both unitary events and membrane waves. 23. The coordination of segmented limb structures during swimming has been investigated. The walking legs are physically protracted during flexion while the unmodified male swimmerets are flicked posteriorly. 24. Swimmeret retraction during swimming is controlled by the activity of a single swimmeret motorneuron which appears to be part of the swimming circuit and which may also be a primitive homologue of the Segmental Giant neuron in crayfish. 25. It is concluded that escape swimming behaviour is homologous with non-giant backwards swimming in crayfish and may also be homologous with swimming in certain sand crab species. The evolutionary relationships of a number of decapods is discussed on the basis of escape circuitry and it is suggested that Galathea may represent an ancestral type of swimming decapod. http://hdl.handle.net/10023/2971 Abstract: A considerable corpus of information regarding the formation of terrestrial archaeological deposits exists which is not matched by studies of deposit formation in coastal waters. Similarly, there is a disjunction between strident calls for minimal disturbance investigation, with conservation in situ, and knowledge of how this might actually be achieved in the marine environment. The manner in which the investigation of deposit formation can complement the study of in situ conservation is considered An approach is proposed which combines selected elements of Schiffer's Transformation Theory with a method of studying changes to deposits outlined by Wildesen. It is suggested that, although sufficient regularities can be detected in the influence of formation processes to allow their influence to be recognised and inference refined accordingly, there are case specific limitations on the extent to which the precise influence of each process can be described and evaluated. A case study is presented which investigates casual depredation as a formation process. Commercial fishing activity and marine burrowing activity are the subject of detailed consideration. New insights into these processes result from this study and specific recommendations concerning in situ conservation of deposits subject to their influence are made. The need to consider fishing practice as well as the mechanical properties of fishing gear in the study of deposit formation and protection is emphasised. The excavation of a 16th century wreck in Studland Bay, Dorset, is used to demonstrate the pervasive influence of burrowing activity and the problems associated with mitigation of this process. Recommendations are made regarding future study of formation processes and the development of policy related to the management of the submerged archaeological resource. Sun, 01 Jan 1995 00:00:00 GMT http://hdl.handle.net/10023/2971 1995-01-01T00:00:00Z Ferrari, Ben A considerable corpus of information regarding the formation of terrestrial archaeological deposits exists which is not matched by studies of deposit formation in coastal waters. Similarly, there is a disjunction between strident calls for minimal disturbance investigation, with conservation in situ, and knowledge of how this might actually be achieved in the marine environment. The manner in which the investigation of deposit formation can complement the study of in situ conservation is considered An approach is proposed which combines selected elements of Schiffer's Transformation Theory with a method of studying changes to deposits outlined by Wildesen. It is suggested that, although sufficient regularities can be detected in the influence of formation processes to allow their influence to be recognised and inference refined accordingly, there are case specific limitations on the extent to which the precise influence of each process can be described and evaluated. A case study is presented which investigates casual depredation as a formation process. Commercial fishing activity and marine burrowing activity are the subject of detailed consideration. New insights into these processes result from this study and specific recommendations concerning in situ conservation of deposits subject to their influence are made. The need to consider fishing practice as well as the mechanical properties of fishing gear in the study of deposit formation and protection is emphasised. The excavation of a 16th century wreck in Studland Bay, Dorset, is used to demonstrate the pervasive influence of burrowing activity and the problems associated with mitigation of this process. Recommendations are made regarding future study of formation processes and the development of policy related to the management of the submerged archaeological resource. http://hdl.handle.net/10023/848 Abstract: Understanding what psycho-physiological and behavioural factors influence aversiveness of sound in marine mammals is important for conservation and practical applications. The aim of this study was to determine predictors for impact of anthropogenic noise and to develop a target-specific predator deterrence system for use on fish farms. Three classes of stimuli were tested: 1.) grey seal underwater communication calls expected to be used in territorial defence, 2.) high duty-cycle moderately loud artificial sounds (some of which were based on models of unpleasantness for humans), 3.) brief, intense pulses designed to elicit the acoustic startle reflex. Communication calls had no deterrence effect but instead caused attraction responses. Tests with high duty-cycle artificial sounds showed that food-motivated animals habituate quickly, although sound exposure caused subtle changes in diving patterns over a longer time. Field trials using the same stimuli were used to determine avoidance thresholds but also indicated that sound features like ‘roughness’ play a role. The startle eliciting stimuli, however, had the most dramatic effects. To this stimulus most seals exhibited rapid flight responses, hauled out, sensitised and showed signs of fear conditioning. Startle thresholds were found to be 80-85 dB above the assumed hearing threshold. The data showed that startle thresholds are a crucial predictor for the occurrence of strong avoidance behaviour and suggests that the startle response evolved to increase an animal’s propensity for flight. Finally, a prototype predator deterrence system based on the startle sounds was developed to repel seals whilst not affecting toothed whales. In fish farm trials, seals were deterred at close ranges but local abundance of cetaceans did not change showing that it is possible to cause differential responses between species based on differences in their audiograms. The results are used to develop noise exposure criteria and to elucidate acoustic parameters that can be used to predict responses to anthropogenic noise. Tue, 01 Jan 2008 00:00:00 GMT http://hdl.handle.net/10023/848 2008-01-01T00:00:00Z Götz, Thomas Understanding what psycho-physiological and behavioural factors influence aversiveness of sound in marine mammals is important for conservation and practical applications. The aim of this study was to determine predictors for impact of anthropogenic noise and to develop a target-specific predator deterrence system for use on fish farms. Three classes of stimuli were tested: 1.) grey seal underwater communication calls expected to be used in territorial defence, 2.) high duty-cycle moderately loud artificial sounds (some of which were based on models of unpleasantness for humans), 3.) brief, intense pulses designed to elicit the acoustic startle reflex. Communication calls had no deterrence effect but instead caused attraction responses. Tests with high duty-cycle artificial sounds showed that food-motivated animals habituate quickly, although sound exposure caused subtle changes in diving patterns over a longer time. Field trials using the same stimuli were used to determine avoidance thresholds but also indicated that sound features like ‘roughness’ play a role. The startle eliciting stimuli, however, had the most dramatic effects. To this stimulus most seals exhibited rapid flight responses, hauled out, sensitised and showed signs of fear conditioning. Startle thresholds were found to be 80-85 dB above the assumed hearing threshold. The data showed that startle thresholds are a crucial predictor for the occurrence of strong avoidance behaviour and suggests that the startle response evolved to increase an animal’s propensity for flight. Finally, a prototype predator deterrence system based on the startle sounds was developed to repel seals whilst not affecting toothed whales. In fish farm trials, seals were deterred at close ranges but local abundance of cetaceans did not change showing that it is possible to cause differential responses between species based on differences in their audiograms. The results are used to develop noise exposure criteria and to elucidate acoustic parameters that can be used to predict responses to anthropogenic noise. http://hdl.handle.net/10023/704 Abstract: Swimming speeds and prey selection of temporally captive, wild grey seals (Halichoerus grypus) were investigated in relation to prey characteristics in an experimental set-up at the Sea Mammal Research Unit (St Andrews, UK). For breath- hold divers, such as seals, the cost of swimming is a key variable in the management of oxygen stores. Thus it is likely that they modulate their swim speeds in order to maximise time spent feeding at a prey patch. We observed a strong relationship between swimming speed and stroke and glide pattern. Seals decreased their swim speeds by increasing their gliding period and as a result they decreased their oxygen consumption. Results indicated that mean swim speed decreased significantly with increasing distance to the patch, consistent with optimality model predictions. In addition, seals modified their swim speeds in response to changes in the speed and density of their prey. Seals decreased their swim speed as the speed of the prey increased. On the other hand, seals increased their swim speed as the density of the prey increased. Concurrently, bottom durations significantly increased suggesting that seals’ foraging strategies allowed them to most efficiently exploit their environment. Prey selection experiments investigated dietary preferences and the factors affecting their choice to select between different types of food. In the present study, seals maximised some aspects of their energy intake but also displayed some individual prey preferences. These findings indicate the importance of fine-scale observations of foraging behaviour and the value of experimental protocols in developing our understanding of marine mammal foraging behaviour. Tue, 01 Jan 2008 00:00:00 GMT http://hdl.handle.net/10023/704 2008-01-01T00:00:00Z Gallon, Susan Louise Swimming speeds and prey selection of temporally captive, wild grey seals (Halichoerus grypus) were investigated in relation to prey characteristics in an experimental set-up at the Sea Mammal Research Unit (St Andrews, UK). For breath- hold divers, such as seals, the cost of swimming is a key variable in the management of oxygen stores. Thus it is likely that they modulate their swim speeds in order to maximise time spent feeding at a prey patch. We observed a strong relationship between swimming speed and stroke and glide pattern. Seals decreased their swim speeds by increasing their gliding period and as a result they decreased their oxygen consumption. Results indicated that mean swim speed decreased significantly with increasing distance to the patch, consistent with optimality model predictions. In addition, seals modified their swim speeds in response to changes in the speed and density of their prey. Seals decreased their swim speed as the speed of the prey increased. On the other hand, seals increased their swim speed as the density of the prey increased. Concurrently, bottom durations significantly increased suggesting that seals’ foraging strategies allowed them to most efficiently exploit their environment. Prey selection experiments investigated dietary preferences and the factors affecting their choice to select between different types of food. In the present study, seals maximised some aspects of their energy intake but also displayed some individual prey preferences. These findings indicate the importance of fine-scale observations of foraging behaviour and the value of experimental protocols in developing our understanding of marine mammal foraging behaviour. http://hdl.handle.net/10023/541 Abstract: Integrated Coastal Zone Management (ICZM) is a dynamic process in which a coordinated strategy is developed and implemented for the allocation of environmental, socio-cultural, and institutional resources to achieve the conservation and sustainable multiple use of the coastal zone. The present study titled “Coastal Zone Management in Dubai with reference to ecological characterization” is an effort to consider critical water quality and ecological issues in the current and future coastal zone of Dubai Creek. The work included water quality, ecology and numerical modeling for predicting future conditions. This study is utmost significant due to management of critical coastal environmental issues (fish mortality, bad odour, unaesthetic view, algal bloom etc.) in Dubai Creek besides protection of internationally recognized bird sanctuary (Ras Al Khor Wildlife Sanctuary) and sustainable multibillion dollar of property developments as an extension of Dubai Creek. Comprehensive attempt made to collect primary data on water quality and ecology during 2005 and 2006 from specific monitoring stations spreading along Dubai Creek. The pragmatic results in Dubai Creek are alarming; the upper region is susceptible to high organic pollution which exhibits 3-122 folds high nutrients levels while biodiversity in the same region at the seabed is almost died and non-existing. The current assessment suggests a policy for the ICZM and an “Immediate Action Plan” for the beneficial and sustainable development of Dubai Creek. The study recommends the following mitigation as a tool for the management strategies of Dubai Creek lagoon: Dredging in the lagoon of Dubai Creek. -- Tertiary treatment of wastewater from Awir STP prior to discharge into the Creek or divert the discharge from the lagoon of Dubai Creek. -- A new Government Decree for the water quality thresholds in Dubai Creek. Tue, 01 Jan 2008 00:00:00 GMT http://hdl.handle.net/10023/541 2008-01-01T00:00:00Z Al Zahed, Khalid Integrated Coastal Zone Management (ICZM) is a dynamic process in which a coordinated strategy is developed and implemented for the allocation of environmental, socio-cultural, and institutional resources to achieve the conservation and sustainable multiple use of the coastal zone. The present study titled “Coastal Zone Management in Dubai with reference to ecological characterization” is an effort to consider critical water quality and ecological issues in the current and future coastal zone of Dubai Creek. The work included water quality, ecology and numerical modeling for predicting future conditions. This study is utmost significant due to management of critical coastal environmental issues (fish mortality, bad odour, unaesthetic view, algal bloom etc.) in Dubai Creek besides protection of internationally recognized bird sanctuary (Ras Al Khor Wildlife Sanctuary) and sustainable multibillion dollar of property developments as an extension of Dubai Creek. Comprehensive attempt made to collect primary data on water quality and ecology during 2005 and 2006 from specific monitoring stations spreading along Dubai Creek. The pragmatic results in Dubai Creek are alarming; the upper region is susceptible to high organic pollution which exhibits 3-122 folds high nutrients levels while biodiversity in the same region at the seabed is almost died and non-existing. The current assessment suggests a policy for the ICZM and an “Immediate Action Plan” for the beneficial and sustainable development of Dubai Creek. The study recommends the following mitigation as a tool for the management strategies of Dubai Creek lagoon: Dredging in the lagoon of Dubai Creek. -- Tertiary treatment of wastewater from Awir STP prior to discharge into the Creek or divert the discharge from the lagoon of Dubai Creek. -- A new Government Decree for the water quality thresholds in Dubai Creek. http://hdl.handle.net/10023/512 Abstract: This thesis describes elements of the assessment and application of Bayesian Maximum Entropy (MaxEnt) image reconstruction techniques for the analysis of fisheries acoustic survey data. The objective is to investigate the utility of this approach in mapping density distributions and estimating biomass. The MaxEnt image reconstruction method derives originally from the field of astrophysics, and this thesis represents an attempt to apply the principles of MaxEnt to the field of ocean ecology. Essentially, what is required is to generate maps of the density distribution of pelagic species (species living in the water column) from extremely limited and sometimes skewed line-transect acoustic survey data. Techniques used presently are largely unsatisfactory for a variety of reasons, and are often inapplicable for data from surveys that do not follow a particular design strategy. This thesis investigates the usefulness of the MaxEnt technique in overcoming some of the difficulties of acoustic survey analysis. A study is made into the possibility of objectively testing whether these techniques offer improvements in accuracy over existing techniques, by attempting to reconstruct simulated data from a virtual survey. I find that plausible reconstructions are possible, and that statistical comparisons indicate these reconstructions are accurate. The technique is also applied quantitatively to real-world survey data, offering new insights into the abundance of Antarctic krill (Euphausia superba) in the Scotia Sea - raising abundance estimates from 109 million tonnes to 208 million tonnes - and into the relative abundance of fish and jellyfish in the Namibian Benguela, where it is shown that the biomass of jellyfish (12.2 million tonnes) now exceeds that of fish (3.6 million tonnes). Sun, 01 Jun 2008 00:00:00 GMT http://hdl.handle.net/10023/512 2008-06-01T00:00:00Z Heywood, Ben G. This thesis describes elements of the assessment and application of Bayesian Maximum Entropy (MaxEnt) image reconstruction techniques for the analysis of fisheries acoustic survey data. The objective is to investigate the utility of this approach in mapping density distributions and estimating biomass. The MaxEnt image reconstruction method derives originally from the field of astrophysics, and this thesis represents an attempt to apply the principles of MaxEnt to the field of ocean ecology. Essentially, what is required is to generate maps of the density distribution of pelagic species (species living in the water column) from extremely limited and sometimes skewed line-transect acoustic survey data. Techniques used presently are largely unsatisfactory for a variety of reasons, and are often inapplicable for data from surveys that do not follow a particular design strategy. This thesis investigates the usefulness of the MaxEnt technique in overcoming some of the difficulties of acoustic survey analysis. A study is made into the possibility of objectively testing whether these techniques offer improvements in accuracy over existing techniques, by attempting to reconstruct simulated data from a virtual survey. I find that plausible reconstructions are possible, and that statistical comparisons indicate these reconstructions are accurate. The technique is also applied quantitatively to real-world survey data, offering new insights into the abundance of Antarctic krill (Euphausia superba) in the Scotia Sea - raising abundance estimates from 109 million tonnes to 208 million tonnes - and into the relative abundance of fish and jellyfish in the Namibian Benguela, where it is shown that the biomass of jellyfish (12.2 million tonnes) now exceeds that of fish (3.6 million tonnes). http://hdl.handle.net/10023/490 Abstract: The aim of this study was to investigate the composition of an acoustic scattering layer in the North Sea that is particularly strong at 38 kHz. A full definition of the biological composition of the layer, along with its acoustic properties, would allow for it to be confidently removed from data collected during acoustic fish surveys, where it presents a potential source of bias. The layer, traditionally and informally referred to as consisting of zooplankton, appears similar to others observed internationally. The methodology utilised in this study consisted of biological and acoustic sampling, followed by application of forward and inverse acoustic modelling techniques. Acoustic data was collected at 38, 120 and 200 kHz in July 2003, with the addition of 18 kHz in July 2004. Net samples were collected in layers of relatively strong 38 kHz acoustic scattering using a U-tow vehicle (2003) and a MIKT net (2004). Acoustic data were scrutinised to determine actual backscattering, expressed as mean volume backscattering strength (MVBS) (dB). This observed MVBS (MVBSobs) was compared with backscattering predicted by applying the forward problem solution (MVBSpred) to sampled animal densities in order to determine whether those animals were responsible for the enhanced 38 kHz scattering. In most instances, MVBSobs > MVBSpred, more pronounced at 38 kHz. It was found that MVBSpred approached MVBSobs more closely with MIKT than with U-tow samples, but that the 38 kHz mismatch was present in both. Inversion of candidate acoustic models predicted gas-bearing scatterers, which are strong at 38 kHz, as most likely to be responsible for this. Potential sources of inconsistencies between MVBSpred and MVBSobs were identified. The presented forward and inverse solutions infer that although the layer often contains large numbers of common zooplankton types, such as copepods and euphausiids, these are not the dominant acoustic scatterer at 38 kHz. Rather, there remains an unidentified, probably gas-bearing scatterer that contributes significantly to observed scattering levels at this frequency. This study identifies and considerably narrows the list of candidates that are most likely to be responsible for enhanced 38 kHz scattering in the North Sea layer, and recommendations are made for potential future studies. Tue, 01 Jul 2008 00:00:00 GMT http://hdl.handle.net/10023/490 2008-07-01T00:00:00Z Mair, Angus MacDonald The aim of this study was to investigate the composition of an acoustic scattering layer in the North Sea that is particularly strong at 38 kHz. A full definition of the biological composition of the layer, along with its acoustic properties, would allow for it to be confidently removed from data collected during acoustic fish surveys, where it presents a potential source of bias. The layer, traditionally and informally referred to as consisting of zooplankton, appears similar to others observed internationally. The methodology utilised in this study consisted of biological and acoustic sampling, followed by application of forward and inverse acoustic modelling techniques. Acoustic data was collected at 38, 120 and 200 kHz in July 2003, with the addition of 18 kHz in July 2004. Net samples were collected in layers of relatively strong 38 kHz acoustic scattering using a U-tow vehicle (2003) and a MIKT net (2004). Acoustic data were scrutinised to determine actual backscattering, expressed as mean volume backscattering strength (MVBS) (dB). This observed MVBS (MVBSobs) was compared with backscattering predicted by applying the forward problem solution (MVBSpred) to sampled animal densities in order to determine whether those animals were responsible for the enhanced 38 kHz scattering. In most instances, MVBSobs > MVBSpred, more pronounced at 38 kHz. It was found that MVBSpred approached MVBSobs more closely with MIKT than with U-tow samples, but that the 38 kHz mismatch was present in both. Inversion of candidate acoustic models predicted gas-bearing scatterers, which are strong at 38 kHz, as most likely to be responsible for this. Potential sources of inconsistencies between MVBSpred and MVBSobs were identified. The presented forward and inverse solutions infer that although the layer often contains large numbers of common zooplankton types, such as copepods and euphausiids, these are not the dominant acoustic scatterer at 38 kHz. Rather, there remains an unidentified, probably gas-bearing scatterer that contributes significantly to observed scattering levels at this frequency. This study identifies and considerably narrows the list of candidates that are most likely to be responsible for enhanced 38 kHz scattering in the North Sea layer, and recommendations are made for potential future studies. http://hdl.handle.net/10023/466 Abstract: As the biomass of jellyfish (medusae of the Scyphozoa and Hydrozoa) has risen in numerous locations worldwide, awareness of their potential to exert a controlling influence on marine ecosystems and hinder the recruitment of fish stocks has increased. Medusae are capable of intensive, size–selective, predation on zooplankton, which may alter the composition of the plankton community. Jellyfish are often found in dense layers, up to hundreds of metres thick, which can extend horizontally for hundreds of kilometres. Such aggregations may benefit specialist feeders, such as turtles, that rely upon jellyfish for food and those fish that are able to find refuge under the jellyfish umbrellas. Nonetheless, the predominance of jellyfish in pelagic ecosystems is not generally viewed as desirable; in fact, this situation has been portrayed as the result of pollution and overexploitation of otherwise productive seas. However, jellyfish are sensitive indicators of environmental change, and their populations appear to respond to climatic fluctuations, so jellyfish warrant study for their intrinsic ecosystem role particularly given present concerns over climate change. With growing acceptance that fishery management should take an holistic ‘ecosystem approach’, knowledge of the interactions between jellyfish, fisheries and climate may be vital in progression towards the goal of ecosystem–based sustainable management of fisheries. Unfortunately, due to their gelatinous nature, medusae are difficult to sample using conventional netting techniques and data on changes in distribution and abundance are consequently sparse. Recent studies have demonstrated that medusae can be detected acoustically and that this technique could provide a rapid and cost–effective estimate of their biomass and distribution. This thesis reports my endeavour to demonstrate the ecosystem role of medusae and to develop acoustic techniques to monitor their biomass. Through regession analyses, I link the abundance of medusae (Aurelia aurita, Cyanea lamarckii, and Cyanea capillata) in regions of the North Sea to climatic fluctuations, as quantified by the North Atlantic Oscillation Index, and show that medusae may be important indicators of regional ecosystem change. The mechanisms linking climatic fluctuations to ecosystem changes are explored via a correlative modelling approach using General Additive Models; I show that the mechanisms are location dependent and explainable in terms of direct, rapidly responding (intra–annual) influences (surface warming, river run–off, and wind–driven mixing and advection) and longer–term (interannual) oceanographic responses (changes in circulation currents i.e. the northward extent of the gulf stream and relative strength of inflow into the North Sea of the North Atlantic current, Continental Shelf Jet and Arctic waters). I present correlative evidence for a detrimental impact by Aurelia aurita on herring 0–group recruitment, once the influence of interannual change in herring spewing stock biomass on recruitment is factored out through modelling with a Ricker stock–recruitment relationship. Similarly, a commensal relationship between whiting and Cyanea spp. medusae is shown to improve North Sea whiting survival to the 1–group. In progress towards the automated acoustic identification of species, I have developed an in situ discrimination tool that can distinguish between echoes from: Aequorea aequorea; Chrysaora hysoscella; clupeid fish (sardine, anchovy and round herring); and horse mackerel/Cape hake. The technique relies upon characteristic differences in echo strength between frequencies, which are determined for each jellyfish species and finfish group using combined multifrequency acoustic and pelagic trawl samples. This method has facilitated the world’s first acoustic–based estimate of jellyfish biomass in the Namibian Benguela Sea. The 12.2 million tonnes of biomass of medusae (Aequorea aequorea and Chrysaora hysoscella) in the Namibian Benguela Sea was found to be greater than the combined biomass, 3.6 million tonnes, of commercially important fish (horse mackerel, Cape hake, sardines, anchovy, and round herring) in the same area. These results suggest that medusae may have an important role in the Benguela ecosystem that has previously been overlooked and that their biomass should be monitored. Sat, 01 Apr 2006 00:00:00 GMT http://hdl.handle.net/10023/466 2006-04-01T00:00:00Z Lynam, Christopher Philip As the biomass of jellyfish (medusae of the Scyphozoa and Hydrozoa) has risen in numerous locations worldwide, awareness of their potential to exert a controlling influence on marine ecosystems and hinder the recruitment of fish stocks has increased. Medusae are capable of intensive, size–selective, predation on zooplankton, which may alter the composition of the plankton community. Jellyfish are often found in dense layers, up to hundreds of metres thick, which can extend horizontally for hundreds of kilometres. Such aggregations may benefit specialist feeders, such as turtles, that rely upon jellyfish for food and those fish that are able to find refuge under the jellyfish umbrellas. Nonetheless, the predominance of jellyfish in pelagic ecosystems is not generally viewed as desirable; in fact, this situation has been portrayed as the result of pollution and overexploitation of otherwise productive seas. However, jellyfish are sensitive indicators of environmental change, and their populations appear to respond to climatic fluctuations, so jellyfish warrant study for their intrinsic ecosystem role particularly given present concerns over climate change. With growing acceptance that fishery management should take an holistic ‘ecosystem approach’, knowledge of the interactions between jellyfish, fisheries and climate may be vital in progression towards the goal of ecosystem–based sustainable management of fisheries. Unfortunately, due to their gelatinous nature, medusae are difficult to sample using conventional netting techniques and data on changes in distribution and abundance are consequently sparse. Recent studies have demonstrated that medusae can be detected acoustically and that this technique could provide a rapid and cost–effective estimate of their biomass and distribution. This thesis reports my endeavour to demonstrate the ecosystem role of medusae and to develop acoustic techniques to monitor their biomass. Through regession analyses, I link the abundance of medusae (Aurelia aurita, Cyanea lamarckii, and Cyanea capillata) in regions of the North Sea to climatic fluctuations, as quantified by the North Atlantic Oscillation Index, and show that medusae may be important indicators of regional ecosystem change. The mechanisms linking climatic fluctuations to ecosystem changes are explored via a correlative modelling approach using General Additive Models; I show that the mechanisms are location dependent and explainable in terms of direct, rapidly responding (intra–annual) influences (surface warming, river run–off, and wind–driven mixing and advection) and longer–term (interannual) oceanographic responses (changes in circulation currents i.e. the northward extent of the gulf stream and relative strength of inflow into the North Sea of the North Atlantic current, Continental Shelf Jet and Arctic waters). I present correlative evidence for a detrimental impact by Aurelia aurita on herring 0–group recruitment, once the influence of interannual change in herring spewing stock biomass on recruitment is factored out through modelling with a Ricker stock–recruitment relationship. Similarly, a commensal relationship between whiting and Cyanea spp. medusae is shown to improve North Sea whiting survival to the 1–group. In progress towards the automated acoustic identification of species, I have developed an in situ discrimination tool that can distinguish between echoes from: Aequorea aequorea; Chrysaora hysoscella; clupeid fish (sardine, anchovy and round herring); and horse mackerel/Cape hake. The technique relies upon characteristic differences in echo strength between frequencies, which are determined for each jellyfish species and finfish group using combined multifrequency acoustic and pelagic trawl samples. This method has facilitated the world’s first acoustic–based estimate of jellyfish biomass in the Namibian Benguela Sea. The 12.2 million tonnes of biomass of medusae (Aequorea aequorea and Chrysaora hysoscella) in the Namibian Benguela Sea was found to be greater than the combined biomass, 3.6 million tonnes, of commercially important fish (horse mackerel, Cape hake, sardines, anchovy, and round herring) in the same area. These results suggest that medusae may have an important role in the Benguela ecosystem that has previously been overlooked and that their biomass should be monitored. http://hdl.handle.net/10023/347 Abstract: 1. Euphausiids are an important component of high latitude pelagic ecosystems, but there is a paucity of information on their distribution, abundance and population processes on within-year time scales. This thesis encompasses new research into the euphausiid-ocean component of two important high latitude ecosystems (South Georgia and the Irminger Sea) on sub-annual time scales. 2. A new method for measuring abundance of Antarctic krill (Euphausia superba) continuously at South Georgia (Southern Ocean) was devised using upward-looking acoustic devices deployed on moorings. These novel platforms provide a new window of observations onto marine systems not open from conventional research vessels. At South Georgia, the moorings provided data at a high temporal resolution giving completely new insight to the function of the coupled biological-physical marine ecosystem. The use of moorings may aid ecosystem-based management at South Georgia and elsewhere. 3. Analysis of mooring data collected between October 2002 and December 2005 indicated a regular annual cycle in krill density: high in summer and low in winter. Mooring estimates of krill density were not statistically different from estimates derived from standard ship-based surveys in adjacent time periods suggesting that the mooring point estimates had relevance in a wider spatial context (c. 100 x 100 km). The results indicated that because of the sharp peaks in the biomass cycle, the exact timing of repeated ship-based acoustic surveys might be critical. Surveys that differ in their timing by only a few weeks might exhibit quite different estimates of biomass because they fall at different points of the cycle. Additionally, within this intra-annual framework, annual ship-based surveys may be able to detect differences between high and low krill years only if they differ by densities of c. 35 g per square m. in summer and c. 20 g per square m. in winter. 4. The mechanisms driving intra-annual variability in Antarctic krill density at South Georgia are likely to be complex. Analysis of mooring data revealed a possible association between high krill density and low water temperatures (at 200 m) at South Georgia. There was evidence that seasonal variation in krill density off-shelf was linked to seasonal variation in current velocity: marked increases in velocity at the end of summer coincided with marked decreases in krill density and abrupt changes in water temperature characteristic of the Sub-Antarctic Current Front (SACCF). Oceanographic data indicated that the SACCF might have impinged in proximity to the moorings during the winter season. However, krill densities were low during these periods and analyses suggest that seasonal variations in krill density were not driven by seasonal oscillations in the position of the SACCF. The data are not consistent with a pattern of seasonal growth, production and mortality of a resident krill population at South Georgia, but are consistent with the notion of large influxes of krill in early summer, and of a predator-driven reduction at between mid- and late-summer. 5. The seasonal distribution, abundance and growth of key euphauiids in the Irminger Sea, North Atlantic was quantified using the first net haul data from the region since the 1930s. Results show a high degree of spatial heterogeneity in the seasonal distribution of euphausiid abundance/biomass during 2001-2002. There was evidence to suggest regional variation in growth and population processes of Meganyctiphanes norvegica and Thysanoessa longicaudata, and this corresponded broadly to distinct physical zones in the Irminger Sea. There were, however, no significant links between growth and temperature and chlorophyll a concentration. This was attributed to high spatial and temporal variability in biological and physical sampling. These data are a prerequisite for understanding ecosystems dynamics in the North Atlantic, and are important for robust ecosystem-based management strategies. 6. Controls on euphausiid spatial heterogeneity at high latitudes are likely to be complex. Important factors include horizontal advection, temperature, resource availability and behavioural mechanisms. Short-term (intra-annual), small-scale (basin-scale) data are fundamental to understanding variability in euphausiid abundance and distribution on broader spatial and temporal scales in these ecosystems. Fri, 22 Jun 2007 00:00:00 GMT http://hdl.handle.net/10023/347 2007-06-22T00:00:00Z Saunders, Ryan Alexander 1. Euphausiids are an important component of high latitude pelagic ecosystems, but there is a paucity of information on their distribution, abundance and population processes on within-year time scales. This thesis encompasses new research into the euphausiid-ocean component of two important high latitude ecosystems (South Georgia and the Irminger Sea) on sub-annual time scales. 2. A new method for measuring abundance of Antarctic krill (Euphausia superba) continuously at South Georgia (Southern Ocean) was devised using upward-looking acoustic devices deployed on moorings. These novel platforms provide a new window of observations onto marine systems not open from conventional research vessels. At South Georgia, the moorings provided data at a high temporal resolution giving completely new insight to the function of the coupled biological-physical marine ecosystem. The use of moorings may aid ecosystem-based management at South Georgia and elsewhere. 3. Analysis of mooring data collected between October 2002 and December 2005 indicated a regular annual cycle in krill density: high in summer and low in winter. Mooring estimates of krill density were not statistically different from estimates derived from standard ship-based surveys in adjacent time periods suggesting that the mooring point estimates had relevance in a wider spatial context (c. 100 x 100 km). The results indicated that because of the sharp peaks in the biomass cycle, the exact timing of repeated ship-based acoustic surveys might be critical. Surveys that differ in their timing by only a few weeks might exhibit quite different estimates of biomass because they fall at different points of the cycle. Additionally, within this intra-annual framework, annual ship-based surveys may be able to detect differences between high and low krill years only if they differ by densities of c. 35 g per square m. in summer and c. 20 g per square m. in winter. 4. The mechanisms driving intra-annual variability in Antarctic krill density at South Georgia are likely to be complex. Analysis of mooring data revealed a possible association between high krill density and low water temperatures (at 200 m) at South Georgia. There was evidence that seasonal variation in krill density off-shelf was linked to seasonal variation in current velocity: marked increases in velocity at the end of summer coincided with marked decreases in krill density and abrupt changes in water temperature characteristic of the Sub-Antarctic Current Front (SACCF). Oceanographic data indicated that the SACCF might have impinged in proximity to the moorings during the winter season. However, krill densities were low during these periods and analyses suggest that seasonal variations in krill density were not driven by seasonal oscillations in the position of the SACCF. The data are not consistent with a pattern of seasonal growth, production and mortality of a resident krill population at South Georgia, but are consistent with the notion of large influxes of krill in early summer, and of a predator-driven reduction at between mid- and late-summer. 5. The seasonal distribution, abundance and growth of key euphauiids in the Irminger Sea, North Atlantic was quantified using the first net haul data from the region since the 1930s. Results show a high degree of spatial heterogeneity in the seasonal distribution of euphausiid abundance/biomass during 2001-2002. There was evidence to suggest regional variation in growth and population processes of Meganyctiphanes norvegica and Thysanoessa longicaudata, and this corresponded broadly to distinct physical zones in the Irminger Sea. There were, however, no significant links between growth and temperature and chlorophyll a concentration. This was attributed to high spatial and temporal variability in biological and physical sampling. These data are a prerequisite for understanding ecosystems dynamics in the North Atlantic, and are important for robust ecosystem-based management strategies. 6. Controls on euphausiid spatial heterogeneity at high latitudes are likely to be complex. Important factors include horizontal advection, temperature, resource availability and behavioural mechanisms. Short-term (intra-annual), small-scale (basin-scale) data are fundamental to understanding variability in euphausiid abundance and distribution on broader spatial and temporal scales in these ecosystems. http://hdl.handle.net/10023/333 Abstract: This thesis describes the results of a three year study which collected larvae of the acorn barnacles Semibalanus balanoides on a rocky coastline in Fife, East Scotland. The nauplii larvae of S. balanoides are released from their parent in springtime in the United Kingdom and develop in the plankton for approximately one to two months. During this period they are transported some distance from the parent population and eventually return to the intertidal shoreline as a cyprid larval stage. The ‘decision’ to settle is a crucial point in the life history of the organism as most sessile organisms cannot move once this has occurred. The supply of larvae to intertidal shorelines was historically neglected until the 1980s. Patterns of settlement were largely considered irrelevant to distribution patterns of adults relative to postsettlement processes such as predation and competition. Despite the resurgence in “supply-side ecology” in the past 20 years there has been little development towards the measurement of larval supply. Consequently there has been very little description of fine scale or large spatio-temporal studies involving larval supply. This study demonstrates the first study directly addressing larval supply independently from larval settlement at mesoscales (metres to kilometres; days to years). Improvements were made to the passive larval trap described by Todd (2003). A conical opening was combined with the spiral trap design and a number of inlet areas were trialled (0.25cm², 0.5cm², 1cm² and 2cm²). These were tested across typical wave regimes measured with a new autonomous pressure sensing wave transducer and the 1cm² inlet was selected as the most appropriate trap design due to a balance between an increased per unit inlet larval capture and sufficient absolute larval capture so as to identify daily variation in larval supply to a site. Larval settlement has been studied extensively and is often used as a direct measure of rates of larval supply. It is widely assumed therefore that rates of settlement are a direct reflection of rates of supply, as long as settlement substrates and adult conspecific responses remain uniform. This thesis provides a means of accurately characterising the supply-settlement relationship for S. balanoides independent of substrate based responses and demonstrates that this is not the case. The relationship was found to be asymptotic, even at sites where there was low larval supply. It was concluded that density-dependent larva-larva interactions were present during the settlement of larvae and were relevant at daily temporal scales, limiting the rates of larval settlement proportional to larval density. There was no obvious effect on this relationship due to wave action however differences were observed between sites and years. Saturation of preferential environments within the tiles was observed resulting in a settlement preference cascade, with larvae being forced to settle in increasingly less preferable areas of the tiles with increasing larval density. Larva-larva interactions are demonstrated as having a considerable effect on the rates of settlement of S. balanoides. Mon, 01 Jan 2007 00:00:00 GMT http://hdl.handle.net/10023/333 2007-01-01T00:00:00Z Phelan, Patrick J. C. This thesis describes the results of a three year study which collected larvae of the acorn barnacles Semibalanus balanoides on a rocky coastline in Fife, East Scotland. The nauplii larvae of S. balanoides are released from their parent in springtime in the United Kingdom and develop in the plankton for approximately one to two months. During this period they are transported some distance from the parent population and eventually return to the intertidal shoreline as a cyprid larval stage. The ‘decision’ to settle is a crucial point in the life history of the organism as most sessile organisms cannot move once this has occurred. The supply of larvae to intertidal shorelines was historically neglected until the 1980s. Patterns of settlement were largely considered irrelevant to distribution patterns of adults relative to postsettlement processes such as predation and competition. Despite the resurgence in “supply-side ecology” in the past 20 years there has been little development towards the measurement of larval supply. Consequently there has been very little description of fine scale or large spatio-temporal studies involving larval supply. This study demonstrates the first study directly addressing larval supply independently from larval settlement at mesoscales (metres to kilometres; days to years). Improvements were made to the passive larval trap described by Todd (2003). A conical opening was combined with the spiral trap design and a number of inlet areas were trialled (0.25cm², 0.5cm², 1cm² and 2cm²). These were tested across typical wave regimes measured with a new autonomous pressure sensing wave transducer and the 1cm² inlet was selected as the most appropriate trap design due to a balance between an increased per unit inlet larval capture and sufficient absolute larval capture so as to identify daily variation in larval supply to a site. Larval settlement has been studied extensively and is often used as a direct measure of rates of larval supply. It is widely assumed therefore that rates of settlement are a direct reflection of rates of supply, as long as settlement substrates and adult conspecific responses remain uniform. This thesis provides a means of accurately characterising the supply-settlement relationship for S. balanoides independent of substrate based responses and demonstrates that this is not the case. The relationship was found to be asymptotic, even at sites where there was low larval supply. It was concluded that density-dependent larva-larva interactions were present during the settlement of larvae and were relevant at daily temporal scales, limiting the rates of larval settlement proportional to larval density. There was no obvious effect on this relationship due to wave action however differences were observed between sites and years. Saturation of preferential environments within the tiles was observed resulting in a settlement preference cascade, with larvae being forced to settle in increasingly less preferable areas of the tiles with increasing larval density. Larva-larva interactions are demonstrated as having a considerable effect on the rates of settlement of S. balanoides.