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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.
31

Aspects of the biology and ecology of six temperate reef fishes (families: Labridae and Monacanthidae).

Barrett, NS Unknown Date (has links) (PDF)
The currently most accepted population theory for reef fish was developed on tropical reefs and suggests that populations of most reef fish species are limited primarily by recruitment, with little post-recruitment resource limitation. I tested the validity of this theory for temperate reef fishes by examining growth rates in six common species from a number of isolated populations for evidence of resource limitation. If resources are limiting, spatial and temporal variation in recruitment and mortality should lead to isolated populations experiencing differing levels of resource availability, particularly food availability, which will be reflected in growth rates. I worked with six of the most common reef fishes found in Tasmanian waters so that any findings would form the basis of a broadly applicable model. These were Notolabrus tetricus, Notolabrus fucicola, Pictilabrus laticlavius, Pseudolabrus psittaculus, Penicipelta vittiger, and Meuschenia australis. Before examining growth rates it was first necessary to define the scale at which populations could be considered to be isolated. The short and long-term movement patterns of each species were studied using visual observations to interpret short-term patterns, and recaptures of tagged fish to interpret the long-term patterns. Methods of ageing each species were developed and validated, with growth rates of tagged fish being used to validate the use of otoliths for ageing. General growth curves are presented. For most of the species, there was some uncertainty in current texts about the sexual system used and the relationship between sex and dichromatism and dimorphism. To clarify this situation the reproductive biology of each species was examined. The relationship between sex and growth rate was also examined. For two species (N. tetricus and N. fucicola) annual growth data from tagged fish were obtained over a 3-4 year period, allowing inter-annual growth variability to be examined. As well as providing an insight into the variability of growth with time, these results also aid in the interpretation of growth curves determined from otolith ageing. In all species investigated, no significant differences in growth rates were detected between populations occupying similar habitats and subject to similar environmental conditions. These results suggest that post-recruitment resource limitation in the form of food limitation may not be an important factor influencing the post recruitment growth and survival of many temperate reef fishes with pelagic larval stages. This agrees with the assumptions made, but rarely tested, in current theories concerning the regulation of populations of reef fish, particularly those on temperate reefs.
32

Assessing the population dynamics and stock viability of striped trumpeter (Latris lineata) in a data limited situation

Tracey, SR Unknown Date (has links) (PDF)
Research into small-scale fisheries is often insufficient, resulting in limited data, because this type of fishery is inevitably constrained by financial considerations. This creates a challenge to provide adequate information to support sustainable management, particularly given the shift from single species management to more integrated spatial and multi-species management and, ultimately, to ecosystem based fisheries management (EBFM). Striped trumpeter (Latris lineata) is widely distributed around the temperate latitudes of the southern hemisphere. The species is iconic to Tasmania where it supports a small commercial fishery, and it is increasingly targeted by recreational fishers. This fish is common on most rocky reefs between 50 – 250 m around Tasmania. However, the historical data for striped trumpeter from Tasmania is patchy in time and space, reflecting opportunistic sampling over many years. Using striped trumpeter as an example of a small-scale data-limited fishery, this study applies a variety of techniques to describe key biological and ecological processes required for sustainable fisheries management. The study was divided into three themes. First, standard and novel analytical techniques were applied to evaluate data to provide key biological parameters required for single-species assessment. Second, stock structure was investigated on both local and global scales using molecular techniques and otolith morphometrics. Finally, recruitment processes were investigated based on otolith microchemistry and modelling of larval dispersal. Seasonal growth variability was observed over the first five years, with growth rates peaking approximately one month after the observed peak in sea surface temperature. The oldest fish in this study was 43 years. Lifetime growth was modelled using a modified twophase von Bertalanffy growth function, with the transition between growth phases linked to changes in physiological and life history traits, including offshore movement as fish approach maturity. Total mortality was estimated using catch curve analysis based on the standard and two-phase von Bertalanffy growth functions, and estimates of natural mortality were calculated using two empirical models, one based on longevity and the other based on the parameters L1 and k from both growth functions. The spawning season around Tasmania occurs in the austral spring, with peak spawning activity in September and October. Size at 50% maturity was estimated at 543 mm fork length (FL) for females (estimated age = 6.8 years) and 529 mm FL for males (estimated age = 6.2 years). Striped trumpeter is a multiple spawner with batch fecundity estimates ranging from 205,054 for a 2 kg fish (540 mm FL) to 2,351,029 for a 9.5 kg fish (800 mm FL). At the current minimum legal size limit of 450 mm total length (equivalent to approximately 425 mm FL), yield-per-recruit was estimated to be close to maximum, and spawning biomass-per-recruit (SPR) ranged from 35 – 52% of virgin stock, depending on the mortality estimates used. Otolith morphometrics, in particular elliptical Fourier analysis of otolith shape, indicated little to no connectivity between the striped trumpeter population of Tasmania and the St. Paul/ Amsterdam Island populations. A molecular assessment of mtDNA confirmed this finding. In addition, the DNA sequence analysis indicated that the New Zealand striped trumpeter population was genetically distinct from the Tasmanian and St. Paul/ Amsterdam Island populations. DNA sequence analysis also indicated that the population around Tasmania is a single population. The affinity of juvenile striped trumpeter to inshore reefs has been suggested from anecdotal fishing observations. Using otolith microchemistry the comparative contribution of juvenile striped trumpeter from shallow inshore habitats to the adult population was estimated. Juvenile striped trumpeter from a strong recruitment pulse (1993 cohort) were collected at age two from inshore reefs and as adults at age six from deeper offshore reefs around the coast of Tasmania. Natural variations were identified in the concentrations of lithium and strontium within the incremental structure of the observed otoliths. Discriminant analysis suggested that 70% of adults sampled originated from an inshore juvenile habitat, 13% were from deeper reefs and 17% could not be statistically allocated with confidence. An integrated bio-physical larval dispersal model was developed in an attempt to explain the high degree of inter-annual recruitment variability displayed by this species. The model utilised information developed through the course of this study on reproductive biology, ontogenic habitat preferences and stock structuring as well as additional information on striped trumpeter larval biology from aquaculture trials to generate realistic scenarios. While the model was unable to accurately predict observed interannual recruitment variability, it did provide insights to important source and settlement regions as well as the importance of the addition of biological components, such as: timing of spawning, growth and mortality. Through efficient data-mining, novel methods and technological advancements this study has provided robust scientific advice to support the management of the striped trumpeter fishery. Information has been collated to support traditional single-species management and also for developing spatial fisheries measures, leading to a more ecosystem based approach to fisheries management. Otoliths proved to be valuable in several areas, and small-scale fisheries would be advised to initiate otolith collections even though analysis may not be planned for some time. This study demonstrates how targeted research could be used in other small-scale data limited fisheries in a cost effective manner to provide information for sustainable management.
33

Trophic structure and the importance of terrestrial wetland producers for aquatic food webs in tropical Australian estuaries /

Abrantes, Kátya Gisela dos Santos. January 2008 (has links)
Thesis (Ph.D.) - James Cook University, 2008. / Typescript (photocopy) Bibliography: leaves 198-218.
34

Benthic macroinvertebrate diversity in a shallow estuary : controls on nutrient and algal dynamics /

McLenaghan, Natalie Ann. January 2009 (has links)
Thesis (M.S.)--Rochester Institute of Technology, 2009. / Typescript. Includes bibliographical references (leaves 113-123).
35

The state of the protection of freshwater inflow to the bays and estuaries of Texas, 2003

Wassenich, Tom, January 1900 (has links)
Thesis (M.A.G.)--Texas State University-San Marcos, 2004. / Vita. Appendices: leaves 269-302. Includes bibliographical references (leaves 303-318).
36

Life histories of juvenile chinook salmon in the Columbia River estuary : 1916 to the present /

Burke, Jennifer L. January 1900 (has links)
Thesis (M.S.)--Oregon State University, 2005. / Printout. Includes bibliographical references (leaves 79-88). Also available online.
37

The state of the protection of freshwater inflow to the bays and estuaries of Texas, 2003 /

Wassenich, Tom, January 1900 (has links)
Thesis (M.A.G.)--Texas State University-San Marcos, 2004. / Vita. Appendices: leaves 269-302. Includes bibliographical references (leaves 303-318).
38

Numerical modeling of estuarine geochemistry /

Wood, Tamara Michelle. January 1993 (has links)
Thesis (Ph. D.), Oregon Graduate Institute of Science & Technology, 1993.
39

Biodiversity and ecosystem processes in heterogeneous environments /

Dyson, Kirstie Elizabeth. January 2008 (has links)
Thesis (Ph.D.) - University of St Andrews, May 2008.
40

The population structure of two estuarine fish species, atherina breviceps (Pisces: Atherinidae) and gilchristella aestuaria (Pisces: Clupeidae), along the Southern African coastline /

Norton, Olivia Bridget. January 2005 (has links)
Thesis (M. Sc. (Zoology and Entomology))--Rhodes University, 2006.

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