The characteristics of Northern squawfish (Ptychocheilus oregonensis) and the feasibility of utilization of this species for human consumption were investigated. In the first experimental phase, the iced storage characteristics of squawfish were determined. Quality changes were monitored over 24 days of storage by chemical, physical, microbiological and sensorial methods of analysis. The Torrymeter readings, K value, descriptive sensory evaluation and taste panel tests demonstrated that squawfish kept well in ice for 15 days. The torsion test results showed that squawfish exhibited good gel forming ability and decreased only 15% of the original value after 24 days of iced storage. The K value might provide the basis of a raw material quality control system for processing. Production of deboned fish mince could be an effective method for utilization of bony squawfish. In the second experimental phase, quality of minced flesh from squawfish was investigated. Texture properties of minced gels as determined by torsional shear stress and strain, at fracture, showed that there was no significant difference in strain value between unwashed and washed mince. No significant differences were also found in strain values of minced gels due to different temperature settings. The addition of cryoprotectants was very effective in maintaining strain value for both unwashed and washed mince during three months of frozen storage. Thiobarbituric acid (TBA) analyses showed minced flesh maintained good quality with regard to oxidation. In the third experimental phase, the suitability of squawfish (Ptychocheilus oregonensis) as a potential species for surimi processing was investigated on the basis of post harvest freshness. The yield of surimi from whole fish ranged between 15.5-21.6%. Fish freshness had a positive correlation with initial surimi quality. The quality changes of surimi during frozen storage depended upon the freshness of material and were influenced by the duration of storage. One wash cycle improved the color of surimi gel significantly. However, there were no significant differences in strain values measured by torsion test due to different wash cycles. Results of the experiment indicated that it was feasible to produce surimi from squawfish stored on ice for up to 9 days. One wash-cycle was adequate for squawfish surimi production. / Graduation date: 1994

A long term study of fish populations on the Bonaparte Plateau, B.C., has revealed the possibility of 2-year cyclic recruitment variation in the pygmy pikeminnow (Ptychocheilus oregonensis). This thesis reviews possible causes of the cycle, and evaluates an inexpensive and non-destructive visual survey method to estimate juvenile population numbers over short summer periods while pikeminnow juveniles are recruiting to the lakes and dying rapidly, for use in future studies of the cyclic pattern. To provide an index of the abundance of juvenile pikeminnow, strip-transect surveys were conducted from shore. Each strip transect area was a full circumference of each of three study lakes, and extended from shore to a distance of up to 3 meters offshore. The visual surveys were shown to be accurate and repeatable when estimating the number of fish and the lengths of the fish in a shoal. The strip transects provide an index of abundance for juvenile northern pikeminnow and this index of abundance can be used to calculate daily summer and interannual mortality rates, providing estimates close to those predicted from the Lorenzen model for size-dependent mortality rates of fish in general. Stationary point surveys were also conducted to investigate juvenile pikeminnow behaviour, and these point surveys reveal a link between sunlight intensity and pikeminnow activity, and provide evidence of direct agonistic interactions between age 0 and age 1 juveniles, which could result in higher mortality rates of age 0 fish when age 1 fish are abundant. Analysis of survey data collected to date over five years from three lakes supports the possibility of a recruitment cycle with lakes out of phase with each other, suggesting that ecological interactions drive the cycles. These interactions are worthy of further investigation.

A long term study of fish populations on the Bonaparte Plateau, B.C., has revealed the possibility of 2-year cyclic recruitment variation in the pygmy pikeminnow (Ptychocheilus oregonensis). This thesis reviews possible causes of the cycle, and evaluates an inexpensive and non-destructive visual survey method to estimate juvenile population numbers over short summer periods while pikeminnow juveniles are recruiting to the lakes and dying rapidly, for use in future studies of the cyclic pattern. To provide an index of the abundance of juvenile pikeminnow, strip-transect surveys were conducted from shore. Each strip transect area was a full circumference of each of three study lakes, and extended from shore to a distance of up to 3 meters offshore. The visual surveys were shown to be accurate and repeatable when estimating the number of fish and the lengths of the fish in a shoal. The strip transects provide an index of abundance for juvenile northern pikeminnow and this index of abundance can be used to calculate daily summer and interannual mortality rates, providing estimates close to those predicted from the Lorenzen model for size-dependent mortality rates of fish in general. Stationary point surveys were also conducted to investigate juvenile pikeminnow behaviour, and these point surveys reveal a link between sunlight intensity and pikeminnow activity, and provide evidence of direct agonistic interactions between age 0 and age 1 juveniles, which could result in higher mortality rates of age 0 fish when age 1 fish are abundant. Analysis of survey data collected to date over five years from three lakes supports the possibility of a recruitment cycle with lakes out of phase with each other, suggesting that ecological interactions drive the cycles. These interactions are worthy of further investigation.

A long term study of fish populations on the Bonaparte Plateau, B.C., has revealed the possibility of 2-year cyclic recruitment variation in the pygmy pikeminnow (Ptychocheilus oregonensis). This thesis reviews possible causes of the cycle, and evaluates an inexpensive and non-destructive visual survey method to estimate juvenile population numbers over short summer periods while pikeminnow juveniles are recruiting to the lakes and dying rapidly, for use in future studies of the cyclic pattern. To provide an index of the abundance of juvenile pikeminnow, strip-transect surveys were conducted from shore. Each strip transect area was a full circumference of each of three study lakes, and extended from shore to a distance of up to 3 meters offshore. The visual surveys were shown to be accurate and repeatable when estimating the number of fish and the lengths of the fish in a shoal. The strip transects provide an index of abundance for juvenile northern pikeminnow and this index of abundance can be used to calculate daily summer and interannual mortality rates, providing estimates close to those predicted from the Lorenzen model for size-dependent mortality rates of fish in general. Stationary point surveys were also conducted to investigate juvenile pikeminnow behaviour, and these point surveys reveal a link between sunlight intensity and pikeminnow activity, and provide evidence of direct agonistic interactions between age 0 and age 1 juveniles, which could result in higher mortality rates of age 0 fish when age 1 fish are abundant. Analysis of survey data collected to date over five years from three lakes supports the possibility of a recruitment cycle with lakes out of phase with each other, suggesting that ecological interactions drive the cycles. These interactions are worthy of further investigation. / Science, Faculty of / Zoology, Department of / Graduate

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal. / Une plante tropicale de la famille des Fabaceae, Sesbania pachycarpa, a fait l'objet d'une évaluation insecticide et/ou insectifuge sur le charançon de la carotte, Listronotus oregonensis (Lec.), et sur le doryphore de la pomme de terre, Leptinotarsa decanlineata (Say). Dans une première phase des travaux, le plus polaire de deux extraits obtenus par séparation chimique de la poudre de la plante a démontré, sur le charançon de la carotte, une activité 3 à 4 fois supérieure à celle de l'huile de neem, ou Azadirachta indica, plante tropicale de référence pour ses propriétés insecticides. Le second extrait, faiblement polaire, n'a démontré aucun effet après 72 heures, à une concentration de 4 %. L'action répulsive d'une concentration de 1 % de l'extrait polaire assure une protection foliaire significative contre la larve LT et l'adulte du doryphore de la pomme de terre ; il faut doubler la quantité d'extrait moins polaire pour assurer une protection équivalente à celle obtenue avec l'extrait de neem. Dans une seconde phase de l'étude, les 17 fractions qui sont obtenues par chromatographie "flash" des deux extraits sont testées sur la larve L^ du doryphore de la pomme de terre. La mortalité après 72 h donne l'ordre d'activité décroissante suivant : 84, B5, AI i, Ag et 85. Les extraits Ag, A^, 84 et 85 ont une activité antiappétante équivalente. Les autres fractions sont peu actives ou en proportion insuffisante pour entreprendre des tests biologiques. L'étude des fractions plus actives 84 et 85, sans le synergiste piperonyl butoxide (PBO), a permis de démontrer qu'une concentration de 0,3125 % assure une protection foliaire significative après 24 h et qu'une augmentation atteignant 8 fois cette concentration n'améliore pas cette protection. Après 24 et 48 h, la mortalité n'est pas significative ; mais elle le devient après 72 h, à la concentration de 2,5 %. En présence du PBO (1 % de la fraction), les 2 fractions, à une concentration de 0,3125 %, assurent une protection foliaire de la plante et une mortalité des insectes significatives. Les résultats indiquent que la fraction 84, après 24 heures, possède une action précoce plus marquée que la fraction B5. Après 72 heures, les deux fractions ont une activité semblable. L'étude chimique a permis de déterminer qu'une monoamine tertiaire, l'hydrochlorure de méthylamine, était le composé le plus abondant de la fraction 84. Dans les conditions expérimentales, cette molécule pourrait plutôt provenir des solvants utilisés que d'une origine végétale ; néanmoins, une petite ouverture sur cette dernière est envisageable, en référence aux études antérieures qui montrent une diversité des monoamines aliphatiques chez diverses espèces végétales.

Le charançon de la carotte (Listronotus oregonensis) s’avère un ravageur important des cultures d’apiacées en Amérique du Nord. Une recrudescence des dommages a été observée ces dernières années, et ce, malgré toutes les mesures de contrôle mises en place. Cette étude visait à déterminer la structure génétique des populations du charançon de la carotte en Amérique du Nord et d’évaluer le rôle de la distance géographique et de la plante hôte sur leur niveau de différenciation génétique. La préférence olfactive envers la plante hôte sur laquelle les charançons d’une même population s’y sont développés a aussi été analysée. La caractérisation de la structure génétique de L. oregonensis s’appuyait sur la discrimination des haplotypes (ADNmt COI) et des nucléotides (SNPs) par génotypage-par-séquençage (GBS). Dix-huit populations incluant 220 individus ont été échantillonnées au Québec, en Ontario, en Nouvelle-Écosse (Canada) et en Ohio (États-Unis). L’olfactométrie examinait la réponse olfactive de trois populations du Québec (195 femelles) en fonction de quatre plantes hôtes (carotte, céleri, céleri-rave et persil). Nos résultats ont montré que la distance géographique s’avère un facteur important de différenciation génétique entre les régions échantillonnées. Les analyses de GBS identifient la Nouvelle-Écosse comme étant la région la plus différenciée de toutes les populations analysées contrairement aux analyses de l’ADNmt COI qui suggèrent une différenciation récente. La plante hôte n’entraîne pas de signature génétique distincte chez le ravageur au Québec, et les trois populations testées n’ont pas présenté de préférence marquée pour une plante hôte, hormis la population issue du champ de carotte. Ces résultats suggèrent une capacité de dispersion limitée du charançon de la carotte à travers l’Amérique du Nord. / The carrot weevil (Listronotus oregonensis) is a major pest of apiaceae crops in North America. An upsurge in damage has been observed in recent years, despite all the control measures deployed. This study aimed to determine the genetic structure of carrot weevil populations in North America and to assess the role of geographic distance and host plants on their level of genetic differentiation. The olfactory preference of carrot weevils for the host plant on which the populations were collected was also analyzed. The characterization of the genetic structure of L. oregonensis was based on the discrimination of haplotypes (COI mtDNA) and nucleotides (SNPs) by genotyping-by-sequencing (GBS). Eighteen populations including 220 individuals were sampled in Quebec, Ontario, Nova Scotia (Canada) and Ohio (United States). Olfactometry examined the olfactory response of three populations in Quebec (195 females) according to four host plants (carrot, celery, celeriac and parsley). Our results showed that geographic distance was an important factor in genetic differentiation between the regions sampled. GBS analyzes identify Nova Scotia as the most differentiated region of all populations, unlike COI mtDNA analyzes, which suggest recent differentiation. The host plant did not demonstrate a distinct genetic signature in Quebec, and the three populations tested did not show a marked preference for a host plant, apart from the carrot field population. Finally, these results suggest limited dispersal of the carrot weevil across North America.