Thesis (M.S.)--University of North Texas, May, 2008. / Title from title page display. Includes bibliographical references.

Factors affecting catch, trap fishing power and reef fish trappability were investigated by experimental fishing with Antillean fish traps on west coast fringing reefs in Barbados. Commercial (small mesh) traps caught significantly more fish (by number and weight), caught significantly smaller fish, and caught a higher proportion of immature fish, than large mesh traps. Fishing power was significantly higher for commercial traps than for large mesh traps. These catch differences between trap types have serious implications for the management of the reef fish resource by the imposition of larger mesh sizes in the commercial fishery. / The squeezability hypothesis and the visual image hypothesis were investigated as explanations for the lower fishing power of large mesh traps. The lower fishing power of large mesh traps results primarily from lower catch rates of fish in the 5.5-6.0 cm body depth size class. This result is strong support for the squeezability hypothesis as an explanation for the lower fishing power of large mesh traps. Differences in the visual images of traps created by structural differences and biotic differences did not produce definitive differences in ingress rates to traps, suggesting that the visual image hypothesis is an inadequate explanation for the lower fishing power of large mesh traps. / The trappability of reef fish differed substantially between species, but trappability differences were not correlated with species mobility, activity of the species in traps, gregariousness, or capacity of the species to squeeze through meshes. Predator-prey effects on trappability were negligible, but trappability was negatively correlated with percent reef cover of the substratum and with substratum rugosity. This suggests that traps are more attractive to fishes in areas where natural structural complexity is lower. (Abstract shortened by UMI.)

No description available.

Thesis (M. M. S.), Memorial University of Newfoundland, 1999. / Bibliography: p. 75-79.

The focus of this study was to design and evaluate a trapping system that would reduce populations of common carp within water bodies in conjunction with establishment of native aquatic macrophytes founder colonies. A pond study and field study were conducted. A pond study was performed at the Lewisville Aquatic Ecosystem Research Facility, located in Lewisville, Texas, followed by a field study within a constructed wetland located in southern Dallas, Texas. For the pond study, twelve funnel traps were constructed (four reps of each type: control, dual-walled and ring cage). Two anti-escape devices were tested with funnels including steel fingers and hinged flaps. Ring cage and dual-walled treatments were planted using native pondweeds, while controls were left unplanted (additional bait and a drift fence scenarios were also tested). Common carp were introduced into the study pond. Chi-square statistical analyses were utilized and showed ring cage treatments using fingers as well as the use of a drift fence to be most effective. Following completion of the pond study, the two most effective treatments (controls and ring cages) were tested within the Dallas, Texas wetland; no carp were caught during the field test.

Το πρόβλημα της αυξημένης σύλληψης υπομεγεθών ατόμων τσιπούρας (Sparus aurata, Linnaeus 1758) στις ιχθυοσυλληπτικές εγκαταστάσεις της λιμνοθάλασσας Μεσολογγίου-Αιτωλικού τις τελευταίες δεκαετίες έχει αποκτήσει σοβαρές διαστάσεις. Το φαινόμενο αυτό εκτός του ότι συνιστά περιβαλλοντική απειλή έχει επιφέρει σημαντική μείωση της εμπορικής αξίας του αλιεύματος με αποτέλεσμα τη συρρίκνωση του εισοδήματος των αλιέων. Η παρούσα εργασία μελετά την επιλεκτικότητα νέων τροποποιημένων ιχθυοπαγίδων που έχουν εγκατασταθεί στη λιμνοθάλασσα στο πλαίσιο μιας πρωτοβουλίας για την αντιμετώπιση του συγκεκριμένου προβλήματος. Η παρακολούθηση αυτής της πρωτοβουλίας έδειξε ότι οι νέες ιχθυοπαγίδες συμβάλλουν στη διαφυγή των υπομεγεθών ψαριών, οπότε και στη μείωση των ποσοτήτων των απορριπτόμενων ψαριών διασφαλίζοντας έτσι τη βιωσιμότητα του ιχθυοπληθυσμού. Επίσης, αυξάνονται τα έσοδα της αλιευτικής εκμετάλλευσης και βελτιώνεται η καθημερινότητα των αλιέων δεδομένου ότι δε μεσολαβεί το στάδιο του διαχωρισμού των μη εμπορεύσιμων από τα εμπορεύσιμα ψάρια. Οι διαφυγές των ψαριών από τις ιχθυοπαγίδες φάνηκε να επηρεάζονται από την αφθονία του αλιεύματος και πιο συγκεκριμένα σε περιπτώσεις μεγάλης αφθονίας παρατηρήθηκε να δυσχεραίνεται η διαφυγή των υπομεγεθών ψαριών από τις ιχθυοπαγίδες. Ενδεχομένως, αυτό να δημιουργεί την ανάγκη επέκτασης της τροποποιημένης επιφάνειας των ιχθυοπαγίδων. Η παρούσα εργασία αποτελεί πηγή σημαντικών πληροφοριών στη λήψη μέτρων με στόχο τη βελτίωση του προτύπου της αλιευτικής εκμετάλλευσης της λιμνοθάλασσας. / The problem of increased capture of undersized individuals of gilthead seabream (Sparus aurata, Linnaeus, 1758) at the Messolonghi - Etoliko lagoon fish traps, the last decades has become serious. This phenomenon apart from the ecological threat has decreased the commercial value of the catch thus leading to a reduction of the fishermen income. The present study investigates the selectivity of new fish traps installed in the lagoon in order to deal with this problem. It was found that modified traps contribute to the escapement of undersized individuals thus decreasing the discards as well as ensuring the sustainability of fish population. Furthermore, new traps exploitation leads to an increase of the income. Also, there is no need to sort undersized fish from the catch thus improving the daily lives of the fishermen. Fish escapement was found to be affected by the abundance of fish catch. In more details, high abundance was observed to make fish escapement difficult. Perhaps, this highlights the need of modified area extension. The present study reflects a source of useful information to take into consideration for the improvement of the lagoon fishery exploitation.

The reason for this story was to investigate a narrative that is important to the identity of North America’s Pacific Northwest Coast – a narrative that revolves around wild salmon, a narrative that always seemed too simple to me, a narrative that gives salmon a mythical status, and yet what does the average person know about this fish other than it floods grocery stores in fall and tastes good. How do we know this fish that supposedly defines the natural world of this place? I began my research as a science writer, inspired by John Steinbeck’s The Log from the Sea of Cortez, in which he writes that the best way to achieve reality is by combining narrative with scientific data. So I went looking for a different story from the one most people read about in popular media, a story that’s overwhelmingly about conflict: I searched for a narrative that combines the science of what we know about salmon and a story of the scientists who study the fish, either directly or indirectly. I tried to follow Steinbeck’s example and include the narrative journeys we take in understanding the world around us, the journeys that rarely make it into scientific journals. I went on about eight field trips with biology, ecology, and archaeology lab teams from the University of British Columbia and Simon Fraser University in Vancouver, with the Department of Fisheries and Oceans onboard the Canadian Coast Guard Ship the W.E. Ricker, and an archaeological crew from the Laich-Kwil-Tach Treaty Society in Campbell River, B.C. At the same time, I was reading a number of things, including a 1938 dissertation by anthropologist Homer Barnett from the University of Oregon titled The Nature and Function of the Potlatch, a 2011 book by economist Ronald Trosper at the University of Arizona, Resilience, Reciprocity and Ecological Economics, and works by psychologist Douglas Medin at Northwestern University and anthropologist Scott Atran at the University of Michigan, written over the past two decades, particular paying attention to their writings on taxonomy and folkbiology. My conclusions surprised me, a little. / Graduate / 0329 / 0324 / 0391

The reason for this story was to investigate a narrative that is important to the identity of North America’s Pacific Northwest Coast – a narrative that revolves around wild salmon, a narrative that always seemed too simple to me, a narrative that gives salmon a mythical status, and yet what does the average person know about this fish other than it floods grocery stores in fall and tastes good. How do we know this fish that supposedly defines the natural world of this place? I began my research as a science writer, inspired by John Steinbeck’s The Log from the Sea of Cortez, in which he writes that the best way to achieve reality is by combining narrative with scientific data. So I went looking for a different story from the one most people read about in popular media, a story that’s overwhelmingly about conflict: I searched for a narrative that combines the science of what we know about salmon and a story of the scientists who study the fish, either directly or indirectly. I tried to follow Steinbeck’s example and include the narrative journeys we take in understanding the world around us, the journeys that rarely make it into scientific journals. I went on about eight field trips with biology, ecology, and archaeology lab teams from the University of British Columbia and Simon Fraser University in Vancouver, with the Department of Fisheries and Oceans onboard the Canadian Coast Guard Ship the W.E. Ricker, and an archaeological crew from the Laich-Kwil-Tach Treaty Society in Campbell River, B.C. At the same time, I was reading a number of things, including a 1938 dissertation by anthropologist Homer Barnett from the University of Oregon titled The Nature and Function of the Potlatch, a 2011 book by economist Ronald Trosper at the University of Arizona, Resilience, Reciprocity and Ecological Economics, and works by psychologist Douglas Medin at Northwestern University and anthropologist Scott Atran at the University of Michigan, written over the past two decades, particular paying attention to their writings on taxonomy and folkbiology. My conclusions surprised me, a little. / Graduate / 0329 / 0324 / 0391

Les recherches en halieutique ont pour objectif d’améliorer les connaissances sur le fonctionnement des populations de poissons afin de transférer celle-ci vers des outils de gestion. Ce travail de thèse repose sur un ensemble d’expériences et de modélisations destinées à approfondir notre compréhension générale du comportement associatif de poissons grands pélagiques avec des objets flottants à la surface de l’océan. Notre objectif est de tester si les milliers d’objets flottants artificiels déployés par les pêcheurs (DCP - Dispositifs de Concentration de Poissons) constituent des pièges écologiques pour les thons tropicaux. <p><p>Pour mener à bien ce travail, nous avons dans le premier chapitre caractérisé le comportement individuel de thons dans un réseau de DCP ancrés. L’analyse de données de marquage acoustique de 96 thons albacores (Thunnus albacares) (30-96 cm) à Hawaii montre que les thons présentent une plasticité comportementale forte face aux DCP qu’ils rencontrent mais également que le temps de résidence sous les DCP diminue avec la taille des individus. Afin de quantifier l’impact de l’augmentation de la densité de DCP il est essentiel de comprendre les mécanismes et les facteurs qui influencent les temps de résidences sous les DCP. Dans le second chapitre, des expériences de choix binaires suggèrent un rôle de la biomasse agrégée dans la formation, la maintenance et la dispersion des agrégations que forment les thons sous les objets flottants. La quantification de la dynamique des arrivées et des départs des poissons aux DCP permettra de valider les hypothèses que nous proposons concernant les mécanismes sociaux sous-jacents d’une part et d’autre part de tester l’influence de la qualité de l’environnement et de la densité de DCP sur les temps de résidences individuels et la distribution spatiale des populations. Dans le troisième chapitre, la comparaison de facteurs de condition de listaos (Katsuwonus pelamis) matures capturés en bancs libres et sous objets flottants dans une zone naturellement riche en objets flottants, et relativement peu impactée par le déploiement de DCP (Le Canal du Mozambique), nous a permis d’établir un point de référence essentiel pour estimer les effets des perturbations actuelles. Plus généralement, les résultats obtenus dans les différents chapitres tendent à conforter l’hypothèse d’un rôle social et non trophique des objets flottants dans l’écologie de thonidés. Les résultats obtenus durant cette thèse amènent à poser un regard nouveau sur l’hypothèse du piège écologique. <p><p>Notre travail s’est principalement intéressé à un modèle biologique de choix, les thons tropicaux. Cependant le cadre théorique des questions abordées, les outils d’observations et les méthodes d’analyses développées sont assez génériques pour être appliqués aux autres espèces rencontrées sous les objets flottants. Cette recherche s’intègre plus généralement dans les problématiques visant à mieux comprendre les stratégies comportementales et la distribution des populations dans des environnements multi-sites.<p> / Doctorat en Sciences agronomiques et ingénierie biologique / info:eu-repo/semantics/nonPublished