Thesis (Ph. D.)--Ohio State University, 1974. / Includes vita. Includes bibliographical references (leaves 183-189). Available online via OhioLINK's ETD Center

The object of this study was to investigate character displacement (Brown and Wilson, 1956) and reduction of phenotypic variability with reduction in niche width (Van Valen, 1965). Dolly Varden from one sympatric (Loon Lake) and two allopatric (Dickson and Foley Lake) populations were compared. Field studies showed that the niche width of sympatric Dolly Varden was less than that of allopatric Dolly Varden owing to food and spatial segregation, confirming results of an earlier study (Andrusak and Northcote, 1971). Character displacement was evident in pyloric caeca numbers and in certain behavioural responses (spatial distribution and feeding) observed in the laboratory. These were accompanied by reduced variability, also apparent in length distributions within year classes, in the sympatric population compared with an allopatric population (Dickson Lake). However, character displacement and reduced variability could not be demonstrated for most morphometric characters, presumably because of the complexity of growth processes involved. Effects of overlapping adjacent year classes and of continuous growth of fish body parts (in contrast to comparable studies with birds) obscured interpretation of such characteristics. / Science, Faculty of / Zoology, Department of / Graduate

Simple algebraic relationships and yield equations that require the minimum of data are developed so as to enable quick and reliable assessments of relative rate of harvesting tropical freshwater fish populations. The age of a fish at the inflexion point is inversely related to the growth rate (K) and directly related to the natural logarithm of the weight length exponent (b). Algebraic relationships between the exponent of anabolism (m) and the weight length exponent are developed. Equations for estimating total mortality from age and length distributions in catch samples are given. Total mortality for both continuous and discrete recruitment are considered. The probability density function and the discrete probability function for a negative exponential are given. The effect of a number of variables on trawl catches is studied and some multiple regression equations which might be used to assess the relative degree of exploitation are presented. The parameters which have been recognized as vital to yield prediction are: the growth rate (K), the weight length exponent (b), the maximum length to which a fish grows (L∞) and the natural and total mortality rates. It is shown that one can replace age with a length expression in yield models and still have reliable yield predictions. It is also shown that a model with a few very relevant parameters, has almost the same predictive power as a model requiring more parameters. / Science, Faculty of / Zoology, Department of / Graduate

No description available.

The pike killifish, Belonesox belizanus Kner, is the largest member of the live-bearing family Poeciliidae. The species is native to Central America, and was introduced into Dade County, Florida in 1957. B. belizanus is primarily piscivorous, and has been identified as a potential ecological "problem" species for Florida due to its heavy predation on small native fishes, especially the mosquitofish (Gambusia affinis). The population structure and reproduction of the Florida population were investigated in this study from field samples and aquarium observations. The mean standard length (SL) of mature females was about 103 mm. Most females larger than 75 mm SL contained yolked developing ova, fertilized eggs, or embryos. Mature males averaged about 72 mm SL, and the majority of males larger than 55 mm SL were mature. The sex ratio of mature fish was significantly skewed in favor of females, while immature fish did not differ significantly from a 1:1 sex ratio. The average brood size of field-caught females was about 99, and there was a significant positive correlation of brood size with size of the parent female. The gross morphology of embryological development was described. Although mature unfertilized eggs, abnormal embryos, and degenerating embryos from a previous brood were found at a low frequency in broods of normal embryos, no evidence of superfetation was found. Sizes and weights of embryos and neonates were the largest reported for the family. There was a significant decrease in mean embryo weight as development proceeded, indicating that developing embryos received little or no nutrient input from the maternal system after fertilization. The average interbrood interval of aquarium-held females was 42 days, and females were capable of storing viable sperm. Field-caught females were capable of year-round reproduction. Laboratory-born neonates were immediately piscivorous, and exhibited distinctive behaviors associated with filling of the swim bladder and with avoiding detection by predators. Comparisons of the reproductive patterns of B. belizanus with other members of the family Peociliidae are discussed.

The present study investigated spatial and temporal relationships between fluctuations in the abundance of Atlantic salmon (Salmo salar L.) and plankton records from the Continuous Plankton Recorder (CPR) in the North Atlantic Ocean. Analyses that examined co-variation in time series of salmon pre-fishery abundance (PFA) from fishing nations on both sides of the North Atlantic revealed a high degree of common variation between neighbouring nations for abundance of one sea winter salmon (1SW) and a common decline in the long-term abundance trends for multi-sea winter salmon (MSW). An appraisal of the data attributes for a selection of plankton taxa sampled by the CPR, corresponding to seasonal abundance in specific regions, indicated that these data capture useful spatial and temporal information on the abundance of the sampled taxa. Spatial interpolations were carried out using Data-Interpolating Variational Analysis (DIVA) for planktonic taxa that have been proven to relate to Atlantic salmon in previous studies, namely Calanus finmarchicus, Euphausiacea and Hyperiidae. Geographical boundaries were established for distinct populations of Calanus finmarchicus and for distinct aggregations of species in the cases of the Euphausiacea and the Hyperiidae. This knowledge was enhanced with information on the likelihood of persistence of these populations obtained by analysing the coherency of their seasonal cycles of abundance. This study detected strong relationships, in the form of long-term correlations, between the three selected plankton taxa (Calanus finmarchicus, Euphausiacea, Hyperiidae) and the diatom component of phytoplankton. These results indicated that the population dynamics of plankton species assemblages in these regions are influenced by common biotic and abiotic factors. Significant relationships were found between pre-fishery abundance PFA estimates for post-smolt salmon and Hyperiid amphipods. The relationships detected were particularly strong for 1SWsalmon of British and Icelandic origin at a lag of 1 year, i.e. corresponding to effects on the early phase of migration at sea. Relationships detected corresponding to the Euphausiacea and Calanus finmarchicus were more prevalent at lag-0 after the first winter at sea i.e. they relate to effects on the adult salmon. The results corresponding to MSW salmon also provided some indication of carry-over effects from the early phase of migration on adult survival. This work provided support for the hypothesis that early marine mortality is critical to the overall dynamics of salmon populations. Such information on ecosystem interactions is needed to improve the current knowledge on factors relating to salmon survival at sea. This information can be used to fine-tune important parameters of predictive models for stock management or conservation of salmon, especially in the face of the pressures of climate change.

Thesis (MScAgric)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: DNA micro satellite loci express extensive allelic variation making them convenient markers for research in many fields employing population genetic tools, including aquaculture and conservation genetics. Twelve Oreochromis mossambicus populations from wild, captive and introduced sources in Southern Africa were screened for genetic variation at ten CA repeat micro satellite loci. Three of the loci - UNHI04, UNHlll, and UNH123 - were sufficiently well resolved to screen extensively and were interpreted according to a model of Mendelian inheritance. Data was analyzed in terms of genetic structure and levels of genetic variation, the effect of management regime in captivity through successive generations on genetic diversity, and the nature of phylogenetic relationships present between populations. Exact tests, carried out using Monte Carlo type multiple resampling techniques, and F-Statistics were used to detect and quantify genetic structure among the twelve populations. The Exact test X2 (P < 0.001), a FST of 0.27 (P < 0.001), eST of 0.26, RsT of 0.28, and a <l>ST of 0.17 all indicated significant structuring among the populations. The evident genetic structuring endorsed the practice of maintaining the populations as separate genetic stocks, in separate tanks, in order to preserve unique genetic material for aquaculture strain development. Populations also exhibited some significant deviations from Hardy Weinberg equilibrium characterised by an overall reduced heterozygosity across the loci. In microsatellite studies, null alleles are often suggested as major contributors to heterozygote deficits. To test for null alleles, two controlled crosses of 0. mossambicus were made. The progeny from each cross were examined for expected parental allelic ratios at the UNHI04, UNHlll and UNH123 loci. All three loci presented evidence of possible null alleles. Accelerated inbreeding and genetic drift through successive generations in captivity can reduce heterozygosity and gene diversity. To investigate loss of diversity a sample taken from the Bushmans population in 1999 (N = 25) was compared with a Bushmans 2000 sample (N = 36). The comparison highlighted altered allele frequencies, a significant increase in average observed heterozygosity and a non-significant change in average expected heterozygosity using the UNHI04 and UNH123 loci. Calculation of genetic distances and phylogenetic comparisons between the populations provided insight into the degree of management required in conserving genetic diversity in natural populations of Mozambique tilapia. UPGMA and Neighbour-Joining techniques were used to construct phylogenetic trees using Dm and ({)~)2 distance matrices. Clustering of populations appeared to reflect geographic locality of the source populations, however certain populations were not congruent with geography. Mantel tests were used to expose a possible association between genetic distance matrices generated from each individual locus. An association would support a geographic background to population genetic structure. The Mantel tests did not provide conclusive evidence. Mantel tests for association between the combined locus Dm and (81l)2 genetic distance matrices and a geographic distance matrix were similarly non-significant. Multi-dimensional scaling (MDS) plots of Euclidean distance values for Dm and (81l)2 matrices presented a two-dimensional view of the genetic distance data. The degree of similarity with the UPGMA and Neighbour-Joining tree-clustering pattern was higher for the (81l)2 than for the Dm MDS plots. Scatter plots indicated a reliable non-linear correlation between Euclidean distance and genetic distance for the two-dimensional MDS. The micro satellite markers employed in this research provided molecular information needed for complimenting a co-study on quantitative genetic evaluation of the twelve populations. The quantitative co-study provided measures of average length and weight gain indices for the populations based on progeny growth trials. No significant correlation of average heterozygosity (gene diversity) with either average weight or length gain was found. The significant genetic diversity and structure present between the twelve populations provided rationale for implementing strategies to conserve natural 0. mossambicus populations as genetic resources, and manage captive populations for long term maintenance of genetic diversity. / AFRIKAANSE OPSOMMING: Die verstaffing van groot alleliese variasie deur DNA mikrosateliete maak van hulle gerieflike merkers vir navorsing in 'n verskeidenheid van velde wat gebruik maak van populasie genetiese gereedskap, ingesluit akwakultuur en bewarings genetika. Twaalf 0. mossambicus populasies wat verkry was vanuit die natuur, in gevangeneskap en ingevoerdes, van Suidelike Afrika was getoets vir genetiese variasie by tien verskillende CA-herhalende mikrosateliet loci. Drie van die loci - UNHI04, UNHlll en UNH123 - is op grootskaal getoets en volgens In model van Mendeliese oorerwing geinterpreteer. Die data was ontleed volgens genetiese struktuur en vlakke van genetiese variasie, die effek wat bestuur strategie in gevangeneskap op genetiese diversiteit in opeenvolgende generasies uitgeoefen het, so wel as die aard van die filogenetiese verhoudings wat teenwoordig is tussen die populasies. "Exact" toetse is uitgevoer deur gebruik te maak van Monte Carlo tipe veelvuldige hermonsterinsamelings tegnieke en F-statistieke is gebruik vir die deteksie en kwantifisering van die genetiese struktuur tussen die twaalfpopulasies. Die Exact toets X2 (P < 0.001), 'n FST van 0.27 (P < 0.001), SST van 0.26, RsT van 0.28, en 'n <DST van 0.17 gee almal 'n indikasie van betekenisvolle strukturering tussen die populasies. Die genetiese struktuur bevestig die beleid dat die populasies behou moet word as aparte genetiese voorraad, in aparte tenke, om te verseker dat die unieke genetiese materiaal behoue bly om akwakultuur variante te ontwikkel. Populasies het ook betekenisvolle verskuiwings van die Hardy Weinberg ekwilibrium getoon, wat gekarakteriseer word deur 'n algemene verlaging van heterosigositeit oor die loci. Nul allele word dikwels aanbeveel om in mikrosateliet studies groot bydraes te maak tot hetersigotiese defekte. Om vir nul allele te toets was twee gekontroleerde kruisings van 0. mossambicus gemaak. Die nageslag van elke kruising was getoets vir verwagte ouer alleliese verhoudings by die UNHI04, UNHlll en UNH123 loci. Al drie loci het getoon dat dit moontlike nul allele kan wees. Versnelde inteling en genetiese drywing deur opeenvolgende generasies in gevangeneskap kan die heterosigositeit en diversiteit verminder. Om die vermindering van diversiteit te toets was 'n monster van die Busmans 1999 (N=25) populasie vergelyk met 'n monster van die Bushmans 2000 (N=36) populasie. Die vergelyking het veranderde alleel frekwensies, 'n betekenisvolle vermeerding in gemiddelde waargeneemde heterosigositeit en 'n onbetekenisvolle verandering in gemiddelde verwagte heterosigositeit getoon deur gebruik te maak van die UNHI04 en UNH123 loci. Berekening van genetiese afstande en filogenetiese vergelykings tussen die populasies het nuwe insig gegee oor die graad van bestuur wat nodig is om genetiese diversiteit in die natuurlike populasies van 0. mossambicus tilapia te behou.UPGMA en Neighbour-Joining tegnieke was gebruik om filogenetiese bome op te stel deur gebruik te maak van Dm en (OIl)2 afstand matrikse. Populasie bondeling het geblyk om geografiese lokaliteit van die bron populasies te toon, alhoewel van die populasies nie met die geografiese lokaliteit ooreengestem het nie. Mantel toetse is gebruik om 'n moontlike assosiasie tussen genetiese afstand matrikse wat verkry is van elke loci bloot te stel. 'n Assosiasie sou 'n geografiese agtergrond tot populasie genetiese struktuur steun. Oortuigende bewys is nie deur die Mantel toetse verskaf nie. Mantel toetse vir assosiasie tussen die gekombineerde loci Dm en (OJ..l)2 genetiese afstand matrikse en In geografiese afstand matriks was ook onbetekenisvol. 'n Tweedimensionele beskouing van die genetiese afstand data is voorgestel deur multidimensionele skaal (MDS) grafieke van Euclidean afstand waardes van die Dm en (OJ..l)2 matrikse te teken. Die graad van ooreenstemming met die UPGMA en Neighbour-Joining boom samevoeging patroon was hoër vir die (OJ..l)2 as vir die DmMDS grafieke. Verspreiding grafieke het 'n vertroubare nie-liniêre korrelasie tussen Euclidean afstande en genetiese afstande vir die twee-dimensionele MDS grafieke getoon. Die mikrosateliet merkers wat in die studie gebruik was het molekulêre informasie verskaf wat nodig is vir 'n komplimentêre studie oor die kwantitatiewe genetiese evalueering van dié twaalf populasies. Die kwantitatiewe studie het afmetings van gemiddelde lengte en gewig vermeerdering van die populasies verskaf gebaseer op nageslag proewe. Geen betekenisvolle korrelasie van gemiddelde hetersigositeit (geen diversiteit) was getoon met óf gemiddelde gewig óf lengte vermeerdering. Die betekenisvolle genetiese diversiteit en struktuur teenwoordig tussen die twaalf populasies het rede gegee om strategieë te implimenteer om natuurlike 0. mossambicus populasies te konserveer as genetiese bronne en om populasies in gevangeneskap te bestuur vir langtermyn instandhouding van genetiese diversiteit.

No description available.

Fish populations from four borrow pit lakes were evaluated for growth, condition, and composition. Information obtained from this study was used to formulate management possibilities to improve the sport fishery in these lakes. This study was conducted on four borrow pit lakes in Delaware and Grant Counties along Interstate 69 in eastcentral Indiana from April, 1976 to October, 1976.Growth data revealed that largemouth bass from Cardinal, Dumpert's, and Walter's Lakes did not reach harvestable size (12 in.) until they were 4 or 5 years old. Bass from all three lakes averaged approximately 62 mm for the yearly increment of growth. Bluegill from Cardinal and Walter's Lakes reached harvestable size (5 in.) by age four while bluegill from Dumpert's Lake were 3 years old when they reached harvestable size. Bluegill averaged 26 mm and 28 mm respectively for Cardinal and Walter's Lakes while Dumpert's Lake averaged 42 mm for the yearly increment.Condition data revealed that only the age five bluegill from Dumpert's Lake were classified in good condition. There were no largemouth bass classified in good condition whereas only age five through seven bass in Walter's Lake were classified in average condition.Growth rates for bass and bluegill were less than most values given in the literature with Dumpert's Lake having the fastest growing bass and bluegill. Bluegill was the dominant species captured from all lakes except Cardinal Lake where gizzard shad was the dominant species. Bluegill and largemouth bass averaged 65% and 12% of the population respectively when young-of-the-year fish were included. This study revealed that these lakes should be able to support a warm-water sport fishery with proper management techniques.

No description available.