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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Maternal Fitness Consequences of Different Causative Agents of Offspring Mortality in Early Life

Mogensen, Stephanie 09 December 2010 (has links)
Maternal effects can be key determinants of female fitness through their influence on early life survival. In salmonids, three main sources of mortality in early life can be attributed to redd superimposition, predation, and starvation (meditated by territory limitation). The influence of different agents of mortality will depend on maternal phenotype (e.g. body size) and within-season reproductive timing. An individual-based model, incorporating both stochastic and deterministic processes, was developed to assess how the relationships between maternal fitness, maternal phenotype (body size) and spawning timing were affected by these different sources of mortality. I found that maternal size influenced fitness under some, but not all circumstances. Larger size was beneficial when predation mortality was low, territories were limited, and/or spawner density was high. Spawning time also influenced maternal fitness; early spawned juveniles were favoured when territories were limited, whereas later spawned juveniles were favoured when predation mortality was high. Component Allee effects at low spawned densities were also detected in some simulations. These results suggest that the fitness consequences of maternal phenotype depend on the sources of mortality present. The fact that these context-dependent sources of offspring mortality in early life may vary between habitats or between years increases the difficulty in identifying the correlates of maternal fitness in salmonid fishes.
2

Fishways and freshwater fish migration on South-Eastern Australia.

Mallen-Cooper, Martin January 1996 (has links)
University of Technology, Sydney. Faculty of Science. / In the last 100 years there have been dramatic declines in the range and abundance of native freshwater fish in south-eastern Australia. These declines have been attributed to habitat loss and degradation (including river regulation, water quality, erosion/siltation, instream cover and riparian vegetation), alien fish species, overfishing, and the obstruction of fish passage. In south-eastern Australia there are 86 species of freshwater fish and 36 of these have some migratory component of their life history that requires free passage along streams. The migrations of these fish in this region have been inhibited or prevented by the existence of more than 1500 dams and weirs. To mitigate this impact there are only 69 fishways. Most of these fishways are based on designs suitable for the swimming ability and behaviour of salmonids from the Northern Hemisphere. There are, however, no native salmonids in Australia. I assessed one of these salmonid fishways, at Euston on the Murray River, for its suitability for passing native fish. Fish were trapped at the top and bottom of the fishway over eight paired days. Although this fishway has one of the lowest slopes of the older fishways, and therefore potentially one of the easiest to ascend, very few of the fish that entered the fishway could get to the top. For example, 777 +/- 238 [x +/- s.e.] golden perch (Macquaria ambigua) per day entered the fishway but only 4 +/- 2 per day were collected at the top of the fishway. This and other data highlighted two points: i) the ineffectiveness of the salmonid-type fishways for native fish; and ii) assessing fishways by counting fish at the top only, although widely used throughout the world, is insufficient to assess the performance of a fishway. Counts of fish from the top of a fishway can, however, be useful to monitor fish populations over time. An excellent example of this is provided by long-term monitoring of the Euston fishway, which shows massive declines in the upstream movements of silver perch (Bidyanus bidyanus), Murray cod (Maccullochella peelii peelii) and Macquarie perch (Macquaria australasica) between 1940-45 and 1987-90, indicating corresponding declines in the populations of these species. The failure of salmonid fishways for non-salmonid fishes has been a common experience throughout the world. It stems partly from a lack of knowledge of the migratory patterns of non-salmonid fish, and from a lack of quantitative experimental research into the swimming ability and behaviour of these fish in fishways. To redress this situation for south-eastern Australia, I tested fish in experimental fishways in a hydraulics laboratory. The fishway design tested was the vertical-slot fishway, which is a pool-type fishway where water flows between each pool via a vertical slot. The design was considered to potentially suit the hydrology of Australian rivers and the behaviour of native fish. For these experiments I selected fish species and life stages representative of the migratory fish fauna of the two major drainages of south-eastern Australia. For the south-eastern coastal rivers I chose juvenile Australian bass (Macquaria novemaculeata)[mean lengths of 40, 64 and 93 mm] and barramundi (Lates calcarifer) [43 mm]. These two species are catadromous, with the adults migrating downstream to the estuary to breed and the juveniles migrating upstream. For the large inland Murray-Darling river system I chose adult golden perch (Macquaria ambigua) [441 mm] and silver perch(Bidyanus bidyanus) [258 mm]. At the beginning of this study, adults of these two species were considered to be the main life stage migrating upstream. In the laboratory experiments fish were tested at different water velocities and probit analysis was applied to the proportion of fish that negotiated these velocities. I used this approach to produce values which I called the NV90 and the NV95, which are the maximum water velocities that 90% and 95% of the fish could negotiate in the fishway. For bass, barramundi and golden perch these values ranged from 0.7 to 1.8 m s-1. These values are well below the standard maximum water velocity for salmonid fishways of 2.4 m s-l. The silver perch results were too variable to analyse. The data obtained from the laboratory experiments were used by water resource agencies to build eight new vertical-slot fishways in coastal and inland rivers of southeastern Australia. One of the largest of these new fishways was at Torrumbarry Weir on the Murray River, which consists of 38 pools, each 3 m long, ascending a 6.5 m high weir. The fishway, if successful, would provide access to 350 km of habitat above the weir. To determine whether or not the fishway was successful in passing native migratory fish it was assessed for 2.5 years by: i) sampling monthly above and below the fishway with a standard set of independent, replicated nets; and ii) sampling within the fishway. The netting showed that there were major aggregations of migratory fish below the weir when the fishway was not operational. However, when the fishway was completed and operational, 13 months after the commencement of sampling, there were no further major aggregations of migratory fish below the weir. These data, combined with high numbers of fish successfully ascending the fishway, indicated the success of this vertical-slot fishway design. It was estimated that from February 1991 to June 1993 20,7 14 native fish and 16,595 alien fish (all carp [Cyprinus carpio]) had successfully ascended the fishway. Sampling at the top and bottom of the fishway showed that the fishway passed almost all the species and sizes classes of native migratory fish, except for Australian smelt (Retropinna semoni). The latter is a small species 15 to 40 mm long that only entered the lower few pools of the fishway. The widespread distribution of this species indicates the migration is facultative. Experiments within the fishway showed that the laboratory experiments had underestimated swimming ability. However, it was discovered that fish still needed over 1.5 hours to ascend the full length of the fishway. In addition, some species only migrated upstream during daylight and if their ascent of the fishway was not completed in daylight the fish moved back down the fishway. I concluded that the original water velocity criterion from the laboratory experiments was appropriate and that future fishways need to consider ascent time and fishway length as well as water velocity. I also concluded that it is more difficult to obtain realistic results from 'off-site' experiments, where fish are transported to a laboratory or other facility, than from in situ experiments where naturally migrating fish are used and are not handled until the end of the experiment. Sampling at Torrumbarry Weir provided detailed information on the biology of the migratory fish species, which is essential to designing effective fishways. Carp(Cyprinus carpio), an introduced or alien species, and bony herring were newly identified as migratory, and golden perch and silver perch were confirmed as migratory. A major finding was that 95% of golden perch and 87% of silver perch moving upstream were immature fish. Previously the upstream movement of immature fish in this river system was considered insignificant. Fortunately the conservative water velocities in the Torrumbarry fishway accommodated these smaller fish(approximately 100 to 300 mm in length). The reason for the large numbers of immature fish migrating upstream is not clear, but it may be to optimise feeding, enhance colonisation, or to compensate for the downstream drift of the pelagic eggs and larvae. Migration of all species was seasonal. Spring, summer and early autumn were the main periods of upstream movement for native fish, and carp moved upstream in spring and early summer. Migration of carp was stimulated by rising water temperature only, but golden perch and silver perch were stimulated to move upstream by small changes in river levels. This small scale variation in streamflow is frequently suppressed by river regulation, and this is likely to have contributed to the significant decrease in the numbers of migrating native fish. Upstream migration of all species often occurred during low flows, as well as higher flows. This also occurs in coastal rivers of southeastern Australia. For both the coastal and inland rivers of this region it will be important to design fishways and environmental flow releases to accommodate this aspect of fish migration and the often semi-arid hydrology of these streams. Golden perch and silver perch were aged using sagittal otoliths and validated using known-age fish. The data showed that the immature fish were all over one year old, suggesting that younger fish are not migrating upstream. More research is needed to determine the location and habitats of the less than one year old fish. Ageing and examination of gonads indicated the size and age at maturity for these fish. This suggested that minimum size limits currently used to regulate the recreational fishery are not allowing fish to reach maturity. Golden perch and silver perch were found to be long-lived fish, up to 26 and 27 years respectively. Interestingly, samples of these two species from other rivers within the Murray-Darling river system show that the maximum sizes of these fish can vary significantly between rivers, suggesting that the ecology of different rivers within this large river system varies considerably. The development of fishways for non-salmonid fishes throughout the world has frequently met with failure. From the work in the present study and from reviewing other work I suggest there are five steps for the development of effective fishways. 1. Determine which fish species are migratory: - it is important to identify the smallest and largest fish that are migratory, as this affects the initial choice of the size of the fishway to test. 2. Test fish in an experimental fishway: - in situ experiments are recommended; - avoid handling of fish before and during experiments. 3 Design the fishway: - first decide on the location of the fishway entrance; - extrapolate research results with caution; - do not reduce pool sizes from the experimental model; - avoid tunnels; - design the fishway to operate over the full range of flows during which fish migrate. 4. Link the fishway with the operation of the dam or weir: - maintain flow and temperature regimes that stimulate migration; - manage flow releases over the spillway to guide fish to the fishway entrance. 5. Assess the fishway: - use quantitative and relevant performance criteria to assess the fishway and not only counts of fish from the top of the fishway. The most common strategy in the past has been to design the fishway and ignore steps 1, 2, 4 and 5. With fishways being increasingly recognised as important tools in the rehabilitation of aquatic biota in temperate river systems, and as a potential tool in the development of water resources in tropical rivers, it is essential that they are appropriately designed, constructed, and assessed. Otherwise the mistakes of the past will very likely be repeated.
3

Fishways and freshwater fish migration on South-Eastern Australia.

Mallen-Cooper, Martin January 1996 (has links)
University of Technology, Sydney. Faculty of Science. / In the last 100 years there have been dramatic declines in the range and abundance of native freshwater fish in south-eastern Australia. These declines have been attributed to habitat loss and degradation (including river regulation, water quality, erosion/siltation, instream cover and riparian vegetation), alien fish species, overfishing, and the obstruction of fish passage. In south-eastern Australia there are 86 species of freshwater fish and 36 of these have some migratory component of their life history that requires free passage along streams. The migrations of these fish in this region have been inhibited or prevented by the existence of more than 1500 dams and weirs. To mitigate this impact there are only 69 fishways. Most of these fishways are based on designs suitable for the swimming ability and behaviour of salmonids from the Northern Hemisphere. There are, however, no native salmonids in Australia. I assessed one of these salmonid fishways, at Euston on the Murray River, for its suitability for passing native fish. Fish were trapped at the top and bottom of the fishway over eight paired days. Although this fishway has one of the lowest slopes of the older fishways, and therefore potentially one of the easiest to ascend, very few of the fish that entered the fishway could get to the top. For example, 777 +/- 238 [x +/- s.e.] golden perch (Macquaria ambigua) per day entered the fishway but only 4 +/- 2 per day were collected at the top of the fishway. This and other data highlighted two points: i) the ineffectiveness of the salmonid-type fishways for native fish; and ii) assessing fishways by counting fish at the top only, although widely used throughout the world, is insufficient to assess the performance of a fishway. Counts of fish from the top of a fishway can, however, be useful to monitor fish populations over time. An excellent example of this is provided by long-term monitoring of the Euston fishway, which shows massive declines in the upstream movements of silver perch (Bidyanus bidyanus), Murray cod (Maccullochella peelii peelii) and Macquarie perch (Macquaria australasica) between 1940-45 and 1987-90, indicating corresponding declines in the populations of these species. The failure of salmonid fishways for non-salmonid fishes has been a common experience throughout the world. It stems partly from a lack of knowledge of the migratory patterns of non-salmonid fish, and from a lack of quantitative experimental research into the swimming ability and behaviour of these fish in fishways. To redress this situation for south-eastern Australia, I tested fish in experimental fishways in a hydraulics laboratory. The fishway design tested was the vertical-slot fishway, which is a pool-type fishway where water flows between each pool via a vertical slot. The design was considered to potentially suit the hydrology of Australian rivers and the behaviour of native fish. For these experiments I selected fish species and life stages representative of the migratory fish fauna of the two major drainages of south-eastern Australia. For the south-eastern coastal rivers I chose juvenile Australian bass (Macquaria novemaculeata)[mean lengths of 40, 64 and 93 mm] and barramundi (Lates calcarifer) [43 mm]. These two species are catadromous, with the adults migrating downstream to the estuary to breed and the juveniles migrating upstream. For the large inland Murray-Darling river system I chose adult golden perch (Macquaria ambigua) [441 mm] and silver perch(Bidyanus bidyanus) [258 mm]. At the beginning of this study, adults of these two species were considered to be the main life stage migrating upstream. In the laboratory experiments fish were tested at different water velocities and probit analysis was applied to the proportion of fish that negotiated these velocities. I used this approach to produce values which I called the NV90 and the NV95, which are the maximum water velocities that 90% and 95% of the fish could negotiate in the fishway. For bass, barramundi and golden perch these values ranged from 0.7 to 1.8 m s-1. These values are well below the standard maximum water velocity for salmonid fishways of 2.4 m s-l. The silver perch results were too variable to analyse. The data obtained from the laboratory experiments were used by water resource agencies to build eight new vertical-slot fishways in coastal and inland rivers of southeastern Australia. One of the largest of these new fishways was at Torrumbarry Weir on the Murray River, which consists of 38 pools, each 3 m long, ascending a 6.5 m high weir. The fishway, if successful, would provide access to 350 km of habitat above the weir. To determine whether or not the fishway was successful in passing native migratory fish it was assessed for 2.5 years by: i) sampling monthly above and below the fishway with a standard set of independent, replicated nets; and ii) sampling within the fishway. The netting showed that there were major aggregations of migratory fish below the weir when the fishway was not operational. However, when the fishway was completed and operational, 13 months after the commencement of sampling, there were no further major aggregations of migratory fish below the weir. These data, combined with high numbers of fish successfully ascending the fishway, indicated the success of this vertical-slot fishway design. It was estimated that from February 1991 to June 1993 20,7 14 native fish and 16,595 alien fish (all carp [Cyprinus carpio]) had successfully ascended the fishway. Sampling at the top and bottom of the fishway showed that the fishway passed almost all the species and sizes classes of native migratory fish, except for Australian smelt (Retropinna semoni). The latter is a small species 15 to 40 mm long that only entered the lower few pools of the fishway. The widespread distribution of this species indicates the migration is facultative. Experiments within the fishway showed that the laboratory experiments had underestimated swimming ability. However, it was discovered that fish still needed over 1.5 hours to ascend the full length of the fishway. In addition, some species only migrated upstream during daylight and if their ascent of the fishway was not completed in daylight the fish moved back down the fishway. I concluded that the original water velocity criterion from the laboratory experiments was appropriate and that future fishways need to consider ascent time and fishway length as well as water velocity. I also concluded that it is more difficult to obtain realistic results from 'off-site' experiments, where fish are transported to a laboratory or other facility, than from in situ experiments where naturally migrating fish are used and are not handled until the end of the experiment. Sampling at Torrumbarry Weir provided detailed information on the biology of the migratory fish species, which is essential to designing effective fishways. Carp(Cyprinus carpio), an introduced or alien species, and bony herring were newly identified as migratory, and golden perch and silver perch were confirmed as migratory. A major finding was that 95% of golden perch and 87% of silver perch moving upstream were immature fish. Previously the upstream movement of immature fish in this river system was considered insignificant. Fortunately the conservative water velocities in the Torrumbarry fishway accommodated these smaller fish(approximately 100 to 300 mm in length). The reason for the large numbers of immature fish migrating upstream is not clear, but it may be to optimise feeding, enhance colonisation, or to compensate for the downstream drift of the pelagic eggs and larvae. Migration of all species was seasonal. Spring, summer and early autumn were the main periods of upstream movement for native fish, and carp moved upstream in spring and early summer. Migration of carp was stimulated by rising water temperature only, but golden perch and silver perch were stimulated to move upstream by small changes in river levels. This small scale variation in streamflow is frequently suppressed by river regulation, and this is likely to have contributed to the significant decrease in the numbers of migrating native fish. Upstream migration of all species often occurred during low flows, as well as higher flows. This also occurs in coastal rivers of southeastern Australia. For both the coastal and inland rivers of this region it will be important to design fishways and environmental flow releases to accommodate this aspect of fish migration and the often semi-arid hydrology of these streams. Golden perch and silver perch were aged using sagittal otoliths and validated using known-age fish. The data showed that the immature fish were all over one year old, suggesting that younger fish are not migrating upstream. More research is needed to determine the location and habitats of the less than one year old fish. Ageing and examination of gonads indicated the size and age at maturity for these fish. This suggested that minimum size limits currently used to regulate the recreational fishery are not allowing fish to reach maturity. Golden perch and silver perch were found to be long-lived fish, up to 26 and 27 years respectively. Interestingly, samples of these two species from other rivers within the Murray-Darling river system show that the maximum sizes of these fish can vary significantly between rivers, suggesting that the ecology of different rivers within this large river system varies considerably. The development of fishways for non-salmonid fishes throughout the world has frequently met with failure. From the work in the present study and from reviewing other work I suggest there are five steps for the development of effective fishways. 1. Determine which fish species are migratory: - it is important to identify the smallest and largest fish that are migratory, as this affects the initial choice of the size of the fishway to test. 2. Test fish in an experimental fishway: - in situ experiments are recommended; - avoid handling of fish before and during experiments. 3 Design the fishway: - first decide on the location of the fishway entrance; - extrapolate research results with caution; - do not reduce pool sizes from the experimental model; - avoid tunnels; - design the fishway to operate over the full range of flows during which fish migrate. 4. Link the fishway with the operation of the dam or weir: - maintain flow and temperature regimes that stimulate migration; - manage flow releases over the spillway to guide fish to the fishway entrance. 5. Assess the fishway: - use quantitative and relevant performance criteria to assess the fishway and not only counts of fish from the top of the fishway. The most common strategy in the past has been to design the fishway and ignore steps 1, 2, 4 and 5. With fishways being increasingly recognised as important tools in the rehabilitation of aquatic biota in temperate river systems, and as a potential tool in the development of water resources in tropical rivers, it is essential that they are appropriately designed, constructed, and assessed. Otherwise the mistakes of the past will very likely be repeated.
4

Evaluation of restoration efforts in Dalälven - conditions for survival rate of Salmo trutta and Salmo salar

Svärd, Ville January 2023 (has links)
Rivers are among the most anthropogenically affected ecosystems in the world by irrigation, transportation, channelizing, and hydropower. Habitat restorations have become a popular method to restore the heterogeneity and complexity of rivers aiming for improvement of biodiversity. In this master thesis, I studied the effects of restoration in a regulated and channelized river in the middle of Sweden. Differences in fish abundance and diversity together with hatching success and survival rate from egg to smolt of Seatrout (Salmo trutta) and Atlantic salmon (Salmo salar) were tested between restored and unrestored reaches. In addition, differences in abundance, biomass, diversity, and composition of benthic species between restored and unrestored areas were studied.  The study design consisted of three restored and three unrestored locations where artificial spawning grounds (redds) were placed, electrofishing was conducted, and an inventory of abundance, biomass and diversity metrics of benthic fauna was performed. Whitlock-Vibert boxes were used in the artificial redds and were used to calculate hatching success. The inventory of benthic fauna consisted of kick-sampling and sampling of stones followed by identification and measuring of length in the lab.  The findings in this study suggest that the survival of salmonids is not limited by the hatching success but that the lack of migration possibilities and the low survival rate from egg to smolt makes it unlikely with a successful reintroduction of Atlantic salmon and seatrout in Dalälven. Furthermore, one could argue that the habitat restorations have not increased the diversity of benthic fauna. However, it is possible that there is an ongoing shift in the benthic fauna towards a more diverse community in the restored areas and it is possible it will be more visible in a few years which supports maintaining long-term monitoring. Lastly, this study enlightens consequences with anthropogenically affected rivers and leaves opportunities for further studies.
5

Foraging efficiencies on drifting and benthic prey in juvenile salmonids - effect of light / Födosökseffektivitet på driftande och bentiska byten hos juvenila laxfiskar - effekt av ljus

Larsson, Pia L. M. January 2016 (has links)
Stream living salmonids are generally regarded as drift feeders that rely upon their vision when foraging. It has been shown that salmonids become nocturnal at low water temperatures, but have a low foraging efficiency as light intensity is low, due to their dependence upon vision. Shifting from drift feeding to benthic feeding, has been suggested, and analyses of gut contents during winter have shown that the diet of salmonids mainly consists of benthic invertebrates. Most experimental studies of salmonid foraging have only offered the fish drifting prey or only given the fish access to benthic prey in total darkness. Such conditions rarely occur in nature and the importance of benthic foraging to salmonids may therefore have been underestimated. In this study I conducted a stream laboratory experiment to test if low light intensity caused juvenile Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) (age 0+) to forage more on benthic than drifting prey. The salmon foraged on both drifting and benthic prey during high light but consumed only benthic prey during low light (by one of six fish). Trout foraged on both drifting and benthic prey during both high and low light, but foraging efficiency was lower during low than high light and foraging efficiency was lower for benthic prey than for drifting prey. These results indicate that both species forage more opportunistically than previously thought. / Strömlevande laxfiskar anses generellt vara driftätare som förlitar sig på synen när de födosöker. Det har visats att laxfiskar blir nattaktiva vid låga vattentemperaturer, men har en låg födosökseffektivitet då ljusintensiteten är låg, på grund av sitt beroende av synen. Skifte från driftätande till att äta bentiska byten, har föreslagits, och analyser av maginnehåll under vintern har visat att laxfiskars diet huvudsakligen består av bentiska evertebrater. De flesta experimentella studier av laxfiskars födosök har endast erbjudit fisken driftande byten eller endast gett fisken tillgång till bentiska byten vid totalt mörker. Sådana förhållanden förekommer sällan i naturen och betydelsen av bentiskt födosök för laxfiskar kan därför ha underskattats. I den här studien utförde jag ett experiment i en laboratorieström för att testa om låg ljusintensitet fick juvenil Atlantlax (Salmo salar) och öring (Salmo trutta) (ålder 0+) att födosöka mer på bentiska än driftande byten. Laxen födosökte på både driftande och bentiska byten vid högt ljus men bara bentiska byten åts vid lågt ljus (av en av sex fiskar). Öringen födosökte på både driftande och bentiska byten vid både hög och låg ljusintensitet, men födosökseffektiviteten var lägre vid låg än hög ljusintensitet och födosökseffektiviteten var lägre för bentiska än förbiflytande byten. Dessa resultat indikerar att båda arterna födosöker mer opportunistiskt än vad man tidigare ansett.
6

Investigations on the gut microbiota of salmonids and the applications of probiotics-based feed additives

Abid, Ali Atia January 2014 (has links)
A series of investigations were conducted in order to characterise the GIT microbiota of salmonids and to determine the effect of microbial modulating feed additives on the intestinal microbiota, immunity and growth of salmonids. The first experiment, Chapter three, used PCR-DGGE and 16S rRNA gene sequence analysis of cultivable bacteria were used to investigate the GIT microbiota of brown trout. 16S rRNA gene sequence analysis demonstrated that Citrobacter freundii and Carnobacterium maltaromaticum were the predominant culturable viable bacteria and lactic acid bacteria, respectively in all regions of the GIT. DGGE revealed complex communities with a diverse range of microbes from the Firmicutes and Proteobacteria phyla. The latter chapters focused not only identifying the gut microbiota of salmonids, but also on the ability of probiotics and prebiotics to modulate these communities. In Chapter four, rainbow trout were fed a commercial diet supplemented with P. acidilactici for four weeks. P. acidilactici was detected in the GIT of the probiotic group by multiple methods and P. acidilactici was able to persist for at least 24h at the cessation of probiotic feeding. Histological appraisal on the intestine revealed significantly higher microvilli density in the posterior mucosa and a higher density of goblet cells in the anterior mucosa of the probiotic fed fish. RT-PCR results demonstrated that IL-1β, IL-8 and IgT gene expression were up-regulated in the P. acidilactici fed fish at the end of the study. Whilst mRNA of PCNA, HSP70 and casp-3 were down-regulated in the probiotic group at both sampling points. In Chapter five, the efficacy of dietary administration of P. acidilactici and short chain fructooligosaccharide (scFOS) on Atlantic salmon (Salmo salar L.) was evaluated at 63 and 132 days. Compared to the control group, total bacterial cell counts in all regions of the intestine with exception of the anterior digesta were significantly lower in the synbiotic group at the mid sampling point. PCR-DGGE revealed that species richness, diversity and the number of OTUs were significantly higher in the synbiotic group in the anterior digesta at the mid sampling point. Intestinal microvilli and villi length were increased in the anterior intestine of the synbiotic fed group at the end sampling point. IEL levels were increased in the synbiotic group in the posterior intestine at both sampling points. The expression of immunological genes were significantly up-regulated in the synbiotic fed salmon. In Chapter six, rainbow trout were fed three diets fishmeal (FM), soybean meal (SBM) and PlantMix diets supplemented with or without P. acidilactici for 12 weeks. At both sampling points, with exception of fish fed FM, LAB levels were significantly higher in all probiotic groups compared to the control groups. Serum lysozyme activity was significantly higher in fish fed FM and SBM diets containing P. acidilactici than that of fish fed the control diets. This body of research demonstrates that P. acidilactici can modulate immune response via up-regulation of immune genes as well as modulate IEL and goblet cell levels. Despite these benefits, P. acidilactici had no detrimental effects on growth performance.
7

Population level variation of Atlantic salmon in the chalk streams of southern England and neighbouring regions

Ikediashi, Charles Isioma January 2015 (has links)
In this thesis, population level variation is elucidated for Atlantic salmon living in the chalk streams of southern England – a unique and unusual habitat – as well as in immediately surrounding regions. Salmon in these chalk streams have yet to be robustly investigated, despite individual populations standing out from neighbouring populations in several previous studies. This thesis attempts to identify how different they are and the reasons for it. Then, this thesis also investigates the effect of this distinction on their internal population structure, as well as the current and future trajectory. A panel of microsatellite markers from the SALSEA-merge project were used to complete four studies of population structure in Atlantic salmon. In the first study, which served primarily, as a training exercise, a multi-national baseline was used to identify the origins of salmon recolonising the river Mersey in northwest England. Fish entering the Mersey originated from multiple sources, with the greatest proportion (45–60%) assigning to rivers in the geographical region just north of the Mersey, including Northwest England and the Solway Firth. The number of fish originating from proximal rivers to the west of the Mersey was lower than expected. The results suggested that the recolonisers were straying in accordance with the predominantly clockwise gyre present in the eastern Irish Sea. In the second study, the relationship of salmon in the chalk streams of southern England to salmon outside this region was elucidated. Salmon from all five chalk streams in southern England with major salmon populations were found to all be genetically distinct from these neighbours and statistically less genetically diverse than salmon in southwest England and France. The reasons for this were relatively low immigration and a history of low effective population size. In the third study, the extent of population structure of salmon between the chalk streams and within one chalk stream, the river Frome, was explored. The results suggested these salmon were divided into three groups, i.e. 1) the Frome & Piddle, 2) the Avon and 3) the Test & Itchen. A significant pattern of isolation by distance between salmon in these five rivers was also identified. Historic samples from the Avon were assigned to the contemporary three groups. Surprisingly, most of these fish assigned to the Frome and Piddle group. Within the river Frome, further sub-structure was identified over two separate years of sampling. Salmon from 2009 comprised three genetic groups, and salmon in 2011 comprised just two. In the fourth study, historic scale samples were used to assess the current trajectory of genetic diversity and effective population size of salmon populations across Scotland, England, Wales and France. The majority of samples greater than 30 years old proved ineffective using the SALSEA panel. However, data was compiled from samples from eight rivers ranging from the Tweed in Scotland to the Scorff in France and from 1972 to 2012. Contrary to our hypothesis, most populations showed increases in allelic richness. Populations from one chalk stream show the steepest temporal decline in genetic diversity, which we speculate is partly due to the low immigration into the region. Effective population size proved difficult to determine using a number of methods and no robust pattern was identified. Together these studies indicate that low immigration of salmon into the chalk streams appears to be key to their low genetic diversity and genetic distinction. Low immigration may also have enabled marked within-river population structure and the current negative trajectory of genetic diversity. The implications for general understanding of Atlantic salmon population structure across their range, and for the conservation of this species are discussed.
8

Reproduction by Adfluvial Salmonids in Spawn Creek, Cache County, Utah

Bernard, David R. 01 May 1976 (has links)
The migration and production of indigenous populations of brown, brook, and cutthroat trouts in Spawn Creek, Cache County, Utah, were studied in 1973 and 1974 to elucidate the role of this stream vis- a - vis the rest of the watershed . Spawn Creek and its watershed were described climatically, hydrologically , geologically , vegetatively, recreationally, and chemically. The prevalent, aquatic taxa of fauna and flora were also listed. The equipment and techniques used in the study t o collec t data, including a two-way fish trap and electro- fishing gear, were delineated . The collected data consisted of periodic estimates of mean weight and density stratified by year classes . These year classes were separated by length-frequency histograms, the length of individuals of known age , and the determination of age via counts of annuli on scales. This last method of aging was adjusted for the failure of cutthroat trout to form an annulus in their first year of life . The estimates of density were obtained through a modified form of the two-catch removal estimator. This estimator was designed to correct the estimates for emigration from the sampled area between the two sampling efforts . The biases in several unmodified multi-catch removal e , · imators vis- a-vis the populations of trout in Spawn Creek were discussed relative to the different , individual sizes of several year classes. Mathematical models to describe t he time-dependent growth and density were constructed from the von Bertalanffy equation and the equation of depensatory mortality, respectively, by adding trigonometric components to each. The added constraints imposed by these components were discussed for models of both growth and dens ity . These models were fitted to the appropriate , periodic estimates of growth and density to provide functions of these states vis-a-vis time. The calculation of production for each year class consisted of differentiating the appropriate model of growth, multiplying the resultant differential equation by the appropriate model of density , and integrating the product for various interval s of time. A numerical routine for integration was used when the solution of the integral of the aforementioned product was unattainable in closed form . The basic alogarithm of this routine was discussed. The periodic estimates f rom the data showed that several year classes such as the 1971 year class of cutthroat trout and the 1970 and 1971 year classes of brook trout, were numerically dominant in 1973 but not in 1974. When most of t he individuals in the last two year classes died via senescence in 1974 , the density and productive capacity of the brook trout population declined. This decline was a result of the failure of this taxa to produce new dominant year classes in 1973 and 1974. The periodic estimates from the data also showed that growth was similar in 1973 and 1974 except for the 0+ age group. The brown and cutthroat trout s of this age grew less in 1974 while the brook trout grew more. Immigration occurred seasonally with the adult cutthroat trout migrating in the spring, and the juvenile cutthroat and brown trout ~ ~oving in the fall. No precedent for the fall emmigration of cutthroat juveniles was found in the literature. Emigration was a random affair save for the 0+ age group of cutthroat trout. Migration of brook trout was ~ot significant. Production was greater in the growing season of 1973 than in 1974 for all species . During the year of trap operation only the 1974 year class of cutthroat trout and the 1970 year class of brown trout showed an increase in produced biomass. The failure of the brook trout to produce new dominant year classes was discussed and was attributed to the evacuation of beaver in Spawn Creek and the subsequent dilapidation of their ponds. The underestimation of the production of the 1974 year class of cutthroat trout and the probable causes for said error were discussed. The net emigration of juvenile cutthroat trout and the loss of produced biomass were tied together as a partial cause and effect. The failure of the net immigration of cutthroat trout adults to enhance the productive capacity of these year classes in this stream was attribut ed to reproductive activity and subsequent mortality of these individuals. This relationship along with the predominant emigration of cut throat juveniles showed Spawn Creek vis - a-vis this species to be primarily a vehicle to enhance the reproduction of migrants exclusive to any other activity by this species. The relationship among migration , production, and reproduction of brown trout appeared as described above for t he cutthroat trout , however, the small density of the population of this t rout prevented any firm illation.
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Evaluation of Macroinvertebrates as a Food Resource in the Assessment of Lotic Salmonid Habitat

Weber, Nicholas P. 01 May 2009 (has links)
Criteria used to characterize lotic salmonid habitat are often based on observed correlations between physical habitat characteristics and salmonid abundances. A focus on physical habitat features ignores other habitat components, such as an adequate supply of food that set the physiological limitations on salmonid growth and survival. This study outlines the development of a habitat assessment approach that focuses on how invertebrate food availability interacts with stream temperatures to determine salmonid growth potentials. Abundances of benthic and drifting invertebrate communities, stream temperatures, and juvenile steelhead trout (Onchorhynchus mykiss gairdneri) summer growth rates and abundances were measured within 10 distinct stream segments in central Oregon. Stream temperatures and growth rates were used as inputs for bioenergetics model simulations to produce estimates of O. mykiss summer consumption rates. Measures of invertebrates providing the best description of food availability were chosen based on their ability to explain observed variation in salmonid consumption. Much of the variation in O. mykiss consumption estimates was explained by measurements of total drift biomass along a type II predator response curve. A random effects analysis of variance (ANOVA) was used to partition variation in invertebrate abundances across spatial and temporal scales. Quantification of variation at multiple scales allowed identification of a relevant spatial scale at which to assess macroinvertebrates relevant to salmonid populations, and compare the precision associated with measures of benthic and drifting invertebrate abundances. Results suggested that spatial variation in drifting and benthic invertebrate abundances are greatest at the scale of streams. Total drift biomass and total benthic biomass were more precise at the stream and stream reach scale than drift and benthic density. The information provided by this study will be used to guide the development of sampling approaches that describe invertebrates in a manner more directly related to salmonid production.
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Vliv teplotních a hyperoxických podmínek na růst, příjem krmiva a fyziologii hybrida sivena arktického (Salvelinus alpinus Linnaeus, 1758) a sivena amerického (Salvelinus fontinalis Mitchill, 1815)

ČEJKA, Jakub January 2018 (has links)
This diploma thesis should have tested growth abilities during different temperature and oxygen regime in hybrid between brook trout (Salvelinus fontinalis) and arctic charr (Salvelinus alpinus) culture. There were survival, growth, feed conversion, weight heterogeneity of fish and somatic indexes as followed indicators. The hypothesis was discovery of differences in growth and mentioned indicators during rearing in water with different temperature and oxygen regime. This thesis consists of two done experiments. There were tested five temperature regimes (7, 10, 13, 16 and 19 °C) in the first experiment. Each of tested groups was repeated four times. The experiment took place 84 days and biometric data were measured always after 21 days period. Results showed that the highest weight growth was achieved in fish reared at 13 °C as specific growth rate achieved 4,12 ? 0,21 % × day-1. Higher temperature regimes (16, 19 °C) are not suitable for rearing of Salvelinus hybrid. Survival of tested group reared at 19 °C were only 41,4 ? 27,3 % after the end of the first experiment. At lower temperatures efficient feed conversion were not managed and specific growth rate were lower than at mentioned temperature 13 °C. There were four tested groups permanent hyperoxia (120 130 %), hyperoxia only during a light part of a day, oscillating hyperoxia/normoxia and permanent normoxia (85 95 %) in the second experiment. Each of tested groups was repeated three times. The experiment took place 63 days and biometric data were measured always after 21 days. There were no difference in survival among tested groups and after the end of the second experiment survival was 86,0 ? 1,4 %. The highest specific growth rate were achieved at the normoxia group 1,48 ? 0,05 % × day-1 and at the group where fish were reared under hyperoxia only during a light part of a day - 1,38 ? 0,10 % × day-1. The most efficient feed conversion was mentioned at the fish reared in permanent normoxia and permanent hyperoxia.

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