The current trend towards marine spatial planning (MSP) worldwide impacts marine resource users, particularly in inshore fisheries. Understanding the spatial distribution of fishing activity and complex drivers of human behaviour may help elucidate and predict responses of fishers to changes in management. This thesis characterises fishers’ spatial behaviour and decision-making in the lobster (Homarus gammarus) fishery in Northumberland (UK). Information on the distribution of UK inshore fisheries activity is scarce, but arguably is critical to the success of future MSP and fisheries management. Chapter 2 develops a methodology using GIS to quantitatively compare the spatial coincidence of fishing effort distribution based on two different data sources. A statistically significant similarity is demonstrated between patterns of fishing activity indicated by observational and interview data. Spatial variability in lobster landings and inferred catch rates among fishing ports is examined in Chapter 3 using linear mixed effects models. A negative relationship was identified between measures of fishing intensity and landings at port level, yet this variability in landings is minimal compared to that among individual vessels, the causes of which are discussed. Based on quantitative and qualitative data collected through interviews with fishers, Chapters 4 and 5 investigate how the social context influences fishers’ decision-making and behaviour. Chapter 4 considers fishers’ perceptions in prioritising factors driving spatial decision-making. The findings are examined in light of evidence for territorial behaviour and discussed using theories of economic defendability and collective action. Social network analysis is applied in Chapter 5 to uncover information-sharing behaviour among fishers. Results highlight differences in network structure among ports, demonstrate a relationship between fishers’ position in information-sharing networks and their fishing success, and point towards the existence of social-spatial groups in fishing behaviour at sea. This thesis identifies inter-related factors driving decision-making, suggesting that an understanding of the social context shaping fishers’ spatial behaviour is important for developing appropriate management measures. Taking account of a fishery’s environmental and social characteristics is recommended for predicting fishers’ responses to changes in them.

Recent studies have demonstrated that marine bony fish (teleosts) precipitate inorganic calcium carbonate in their gut as a by-product of osmoregulation, subsequently excreting it into the open water column as loosely aggregated millimetre-scale pellet. These studies have primarily focused on physiological aspects of this process and the fate of resulting carbonates in pelagic settings, which is likely to be dissolution at depth. However, the implications of such carbonate production in shallow tropical and sub-tropical carbonate provinces has also begun to be considered, and it is thought that fish may contribute significant quantities of morphologically distinctive mud-grade high-Mg calcite in certain habitat settings. However, most studies of carbonate mud in modern subtropical settings do not report particles that are obviously fish-derived, and questions concerning fish-derived carbonate characteristics and post-excretion stability thus arise. The present work therefore provides more detailed characterisation of the carbonate products of an expanded range of Caribbean fish species and determines their short-term preservation potential in a sub-tropical carbonate province (the Bahamas). Following collection of carbonates from 22 fish species (all starved), precipitates were characterised using scanning electron microscopy and a suite of complimentary chemical analysis techniques. The form in which these carbonates are likely to be incorporated into surface sediments was investigated by disaggregating pellets and characterising the liberated particles by performing detailed image-based grain size analyses, with additional experiments demonstrating the likely rate and extent of pellet disaggregation by placing them in agitated seawater. Finally, short-term preservation potential was determined in a series of experiments whereby excreted precipitates were exposed to surface seawater and shallow subsurface porewater conditions for several months. Results indicate that, at the point of excretion, fish-derived carbonates are morphologically and mineralogically more varied than previously thought, although most morphotypes (e.g., ellipsoids, dumbbells, spheres, rhombohedra) are seemingly unique in shallow sub-tropical marine settings. ii High-Mg calcite, typically containing 20–35 mol% MgCO3, is the dominant product of about half the species investigated, but Mg calcite with lower MgCO3 contents (in the range 2–20 mol%) is also common, as is aragonite, which can represent up to 27 wt% of carbonates excreted by some species. In addition, amorphous magnesium carbonate (AMC) and magnesium-rich amorphous calcium carbonate (ACC), both of which are strongly hydrated, represent the dominant precipitation products of some species, with a hydrated crystalline phase (monohydrocalcite) occasionally accompanying the latter. A non-carbonate phase, brucite, is nearly ubiquitous as a volumetrically minor phase. Where analysed, all of these phases are further found to differ from other carbonate sediments in the Bahamas with regard to their stable carbon and oxygen isotope compositions; a consequence of the important role of metabolic HCO3 - in the precipitation process. Detailed grain size analyses indicate that most morphotypes are released from pellets upon disaggregation as individual mud-grade particles that retain their distinctive forms. However, extreme agitation can result in polycrystalline forms releasing their fibre-like components; these particles being less distinctive than their parent forms. In contrast, some particles are intergrown and do not disaggregate beyond particle clusters that are up to fine sand sized. Moreover, excreted pellets do not necessarily always disaggregate, with moderate agitation in seawater resulting in a significant proportion of carbonate being retained as intact pellets, albeit smaller (typically fine sand sized) and more well-rounded than initial pellets (typically fine to coarse sand sized). In quiescent settings pellet diminution is less extensive, and it is thus hypothesised that a significant proportion of fish-derived carbonates excreted in the Bahamas is preserved as sand-grade pellets. Despite the highly distinctive nature of fish-derived carbonates, particles that can be attributed to production by fish nevertheless remain elusive in studies of Bahamian surface sediments. It is thus necessary to invoke post-excretion processes of dissolution and/or recrystallisation to explain the apparent disparity between production rates and occurrence as sedimentary particles. Indeed, it is demonstrated here that AMC, brucite, and large quantities of ACC undergo complete dissolution in seawater within a few days of excretion, with the remaining ACC apparently crystallising to form fine sand-grade (50–200 μm diameter) polycrystalline calcite spheres over similar timescales. iii Monohydrocalcite, also undergoes complete dissolution or alteration (to calcite) during 3 month exposures to artificial seawater, and is predicted to alter in a similar manner in natural settings. Conversely, anhydrous crystalline phases remain largely unchanged after porewater and seawater exposures lasting several months, although two important post-excretion processes are observed. Firstly, high-Mg calcite ellipsoids appear to undergo partial dissolution (with preferential loss of MgCO3) and possible recrystallisation, and, based on these observations, it is predicted that longer exposure times will result in changes being pervasive, possibly obscuring the piscine origin of initial crystals. Secondly, carbonate pellets containing minor amounts of aragonite at the point of excretion appear, in some cases, to stimulate post-excretion growth of abundant aragonite needles that are morphologically similar to aragonite needles that dominate Bahamian carbonate muds. It is further apparent that these processes are inhibited in uncleaned samples, possibly due to surface adsorption of organic compounds, but the evidence after 3 month exposures indicates that inhibiting factors might eventually be overcome. Based on these results and modelling of carbonate excretion across shallow platform areas of the entire Bahamian archipelago, it is predicted that about 18 % of excreted carbonates will dissolve after excretion, while a further 53 % may alter beyond recognition within a very short period (perhaps on the order of years). Moreover, characterisation of carbonates produced by three species of normally feeding fish indicates they produce only amorphous carbonates, despite producing crystalline phases when starved. This difference, attributed to the inhibition of CaCO3 crystallisation by dietary phosphate, indicates that loss of fish-derived carbonate to dissolution might be considerably higher than 18 % under normal natural circumstances. The sedimentary significance of fish-derived carbonates thus remains enigmatic, but results presented herein indicate that they follow very different preservation pathways depending on their excreted form, and that they may make previously unrecognised contributions to: i) the carbonate sand fraction (as peloids); and ii) aragonite needle muds (as crystals grown post-excretion).

No description available.

European lobsters form one of the most economically valuable portions of UK landings, yet they are little regulated, despite stocks being considered fully exploited. Biological and behavioural knowledge is lacking, managerial effort is low and understanding is often inferred from other species. To ensure continued productivity of this important fishery, improved data on fishing activity, population dynamics, catchability, recruitment, movement and distribution are urgently required. Through analysis of capture-mark-recapture data, fishery-independent catches, behavioural-interaction studies and acoustic telemetry tracking, this thesis aims to provide a basis for future research and management. Capture-mark-recapture (CMR) and fishery-independent catch data established estimates of density, proportionate distribution, movements and site-fidelity and catchability parameters. These revealed high site fidelity and catchability differences between sexes leading to female-skewed density estimates. If these findings are corroborated, the effect and causes of disproportionate sex ratios must be addressed. The mixed-species nature of UK shellfisheries led to studies recording the impact of inter-specific and intra-specific interactions on catchability and catch rates. Lobster presence significantly lowered catchability of crab species and occurrences of same-sex lobster pairings were lower than expected. Findings highlight both the inconsistency of using catch per unit effort (CPUE) as a direct index of abundance and the danger of analysing crab and lobster catch data in isolation from each other. The final study employed an acoustic telemetry array to quantify in situ lobster movement, providing unique information on short-term home-ranges and habitat-utilisation. There were both transient and resident portions of the population, not predictable by sex or size. Males had significantly larger home-ranges than females, which could explain their increased catchability estimated in the CMR study. In contrast to trap catch data, most lobsters were recorded using soft substrate outwith their home-range. Movement behaviour changed accordingly, from ‘searching’ behaviour on mixed and hard substrates to ‘exploratory’ behaviour on soft. This highlighted a potential connectivity between isolated rocky habitats. The present study reveals the importance of undertaking local lobster studies in order to elucidate behavioural traits and highlight sampling uncertainties that can have important impacts on methods of stock assessment. Findings provide an initial baseline for further data collection, allowing changes in the population to be monitored.

A multidisciplinary approach combining natural and social scientific data was used to provide a holistic view of the practice of discarding in the North Sea fisheries. The research comprised (a) a documentary analysis of discarding in the North Sea; and (b) a case study of one fishery, the English Nephrops fishery. The study aimed to identify the fundamental causes of discarding, the consequences of discarding, the factors that prevent discard reduction and the best means of effectively managing discarding.

No description available.

Over recent years, the availability of satellite telemetry has offered unparalleled opportunities to better understand the behavioural ecology of marine predators. One such predator for which little is known despite the high levels of bycatch in various fishing activities, is the ocean sunfish Mola mola. The work presented here tracked sunfish with three different types of satellite transmitter, revealing unknown spatial dynamics and selected habitats for this species in the north-east Atlantic. Tracked fish displayed seasonal movements that were primarily driven by water temperature, while exhibiting pronounced site fidelity to productive frontal regions. Moreover, there was an apparent size-related variation in dispersal, with larger fish moving farther and positively rheotacting in relation to major oceanographic currents. Furthermore, diving behaviour varied both within and between tracked fish, and both reverse and normal DVM were detected. However, as these different diving patterns did not correlate with geographic region or water column stratification, the observed variability is likely driven by prey distribution oscillations. To investigate this further, DNA barcoding of sunfish stomach contents revealed that while the diet of larger fish included cnidarian species, smaller individuals had a more generalist diet. Thus, although no adult sunfish were sampled, these data support the previously reported ontogenetic shift in diet. Additionally, sunfish foraging success was estimated in relation to simulated planktonic prey-fields (e.g. teleost and invertebrate larvae, gelatinous zooplankton). Tracked sunfish performed better than random null tracks in simulated prey-poor areas, whereas they performed equally in more productive regions. Fine-scale GPS tracking of sunfish behaviour also revealed that area restricted search, a proxy for foraging activity, was associated with areas of likely higher productivity. Lastly, coupling the sunfish behavioural and movement patterns, we explored for the first time the extent of sunfish and pelagic longliners co-occurrence. This revealed that 56% of the observed sunfish habitat was concomitantly used by longliners, representing an average of 2 days-at-risk per month – data that can be further used to inform potential management options. Overall, it is presented here the results of an exceptional opportunity to characterise the behavioural ecology, including interactions with prey and fisheries, of the world’s heaviest teleost, the vulnerable sunfish.

The natural flow paradigm is based on the assumption that aquatic organisms have adapted to a range of flows. However, flow variability is currently not represented in water resource management in England and Wales. This thesis addresses the need to incorporate seasonal and inter annual flow variability in managing rivers for migratory salmonids. This study explores the degree of inter- and intra-annual flow variability at different spatial and temporal scales across the UK, using a novel approach to analysing natural variations in flow regimes. Principle components analysis and cluster analysis, were combined with the Indicators of Hydrologic Alteration approach to analyse 850 years of station flow data from 17 rivers within 3 regions. The analyses focussed on functional flows of know/suspected influence on salmonid populations. Atlantic salmon (Salmo salar) is in decline throughout most of its range, yet as a protected species legally requires measures to improve populations. This thesis assembled multi-decadal datasets in the form of rod catch data, as a proxy to represent salmon populations. However, analyses provided limited meaningful insight into the relationship with flow. It is suggested that the multiple pressures impacting salmon populations, within freshwater, intertidal and marine stages of the lifecycle, made it challenging to isolate the impact of flow. In light of the uncertainties and with the pressure on water resources set only to increase, it is essential that natural flow variability is understood and incorporated into river management. This will provide protection by increasing heterogeneity and possible refugia from extreme events making the Atlantic salmon populations more resilient and able to adapt to anthropogenic and environmental pressures going forward. This study questions if other management actions, such as juvenile habitat enhancement, could also be influential.

A push for a more evidence based approach to management has resulted in the need for robust evidence of fisheries impacts (or lack thereof), including further research into fine-scale impacts of potting for which little evidence is available. The present work focusses on the inshore pot fishery in Northumberland, UK. Potting effort distribution maps - a combination of fishing vessel sightings recorded during routine patrols and fishing effort by the Northumberland Inshore Fisheries and Conservation Authority (NIFCA) – showed changes in potting effort across large sections of the study area between years (2004 – 2014). Temporal changes in fishers’ habitat selection were investigated using recently collected habitat data. Space-time clustering suggested fishers were actively targeting habitats of interest. Compositional analysis of habitat, showed that fishers preferred rocky habitats over sediment habitats when using both EUNIS level 3 and 6 habitat maps. Information on habitat use and fishing pressure provided the basis for investigation of long-term impacts of parlour potting on epibenthos and habitat within the Berwickshire & North Northumberland Coast European Marine Site (BNNC EMS) through analysis of historical videographic monitoring data between 2002 – 2011. Analysis of biotope change between years (a method recommended for monitoring purposes) showed that at the scales investigated here, change had not occurred. Weaknesses of this analysis for the use in robust ecological research are discussed. A more detailed analysis of community composition and diversity change between years showed that there was little evidence of change. However, changes in species composition and richness of ‘Faunal and algal crusts on exposed to moderately wave-exposed circalittoral rock’ were observed between years, in most models and between fishing pressures. Finally, quantification of direct impacts through in-situ experimental fishing was investigated using a BACI design. The high experimental fishing intensity, in small experimental areas, coupled with high levels of sampling and replication, provided iii robust evidence that current levels of potting are unlikely to have a direct physical impact on epibenthos in Faunal and algal crust, and Laminaria spp dominated habitats in Northumberland.

No description available.