Implications of gain functions in fisheries management

The appealing concept of optimal harvesting is often used in fisheries to obtain new management strategies. However, optimality depends on the objective function, which often varies, reflecting the interests of different groups of people. The aim of maximum sustainable yield is to extract the greatest amount of food from replenishable resources in a sustainable way. Maximum sustainable yield may not be desirable from an economic point of view. Maximum economic yield that maximizes the profit of fishing fleets (harvesting sector) but ignores socio-economic benefits such as employment and other positive externalities. It may be more appropriate to use the maximum economic yield that which is based on the value chain of the overall fishing sector, to reflect better society's interests. How to make more efficient use of a fishery for society rather than fishing operators depends critically on the gain function parameters including multiplier effects and inclusion or exclusion of certain costs. In particular, the optimal effort level based on the overall value chain moves closer to the optimal effort for the maximum sustainable yield because of the multiplier effect. These issues are illustrated using the Australian Northern Prawn Fishery.

Queensland Arts Council road trip : an examination of in-schools touring productions (2005-2008)

This research project explores the nature of In-School Touring Productions that are presented in Queensland classrooms by Queensland Arts Council (QAC). The research emerged from my background as a drama teacher working on secondment at QAC in the Ontour inschools department. The research follows the development of a new production Power Trip: the Adventures of Watty and Volt. The research was guided by the key question: What are some of the production and pragmatic issues that relate to In-school Touring Productions and in what ways do QAC’s Ontour inschools productions offer learning experiences? This research involved the creation of three intersecting elements: (1) a 45 minute personal documentary film, 8 Times Around the Equator. The film follows my enthusiasms for this hybrid form of theatre which developed from my childhood, teaching practice and finally in my role at QAC; (2) a multimedia DVD, Queensland Arts Council 2008 inschools Season, which presents a series of short video clips promoting QAC’s Ontour inschools program; and finally (3) this exegetical paper, Queensland Arts Council Road Trip: an Examination of In-Schools Touring Productions (2005-2008). This exegesis supports the multimedia presentations and provides additional descriptions of QAC's Ontour inschools productions which are contextualised within the history of QAC and the field of Youth Theatre generally. During the project I observed 37 QAC productions and analysed them against set criteria and as a result four types of learning experiences were identified: • Category X: X-periencing the Art Form – providing students with exposure to traditional forms of main stage theatre; • Category L: Learning Through the Art Form – communicating information using an art form to educate. For example using comedy, clowning or slapstick to teach science; • Category U: Unpacking the Art Form – deconstructing art forms and providing students with increased awareness and appreciation; and • Category M: M-bodying the Art Form – workshops and artist residencies that allow students to create their own work. The creative works (documentary film and DVDs) combine to make up 65% of the project. This exegetical paper concludes the final 35% required for submission.

A revisit to Pope's cohort analysis

Gulland's [Gulland, J.A., 1965. Estimation of mortality rates. Annex to Arctic Fisheries Working Group Report (meeting in Hamburg, January 1965). ICES. C.M. 1965, Doc. No. 3 (mimeographed)] virtual population analysis (VPA) is commonly used for studying the dynamics of harvested fish populations. However, it necessitates the solving of a nonlinear equation for the instantaneous rate of fishing mortality of the fish in a population. Pope [Pope, J.G., 1972. An investigation of the accuracy of Virtual Population Analysis using cohort analysis. ICNAF Res. Bull. 9, 65-74. Also available in D.H. Cushing (ed.) (1983), Key Papers on Fish Populations, p. 291-301, IRL Press, Oxford, 405 p.] eliminated this necessity in his cohort analysis by approximating its underlying age- and time-dependent population model. His approximation has since become one of the most commonly used age- and time-dependent fish population models in fisheries science. However, some of its properties are not well understood. For example, many assert that it describes the dynamics of a fish population, from which the catch of fish is taken instantaneously in the middle of the year. Such an assertion has never been proven, nor has its implied instantaneous rate of fishing mortality of the fish of a particular age at a particular time been examined, nor has its implied catch equation been derived from a general catch equation. In this paper, we prove this assertion, examine its implied instantaneous rate of fishing mortality of the fish of a particular age at a particular time, derive its implied catch equation from a general catch equation, and comment on how to structure an age- and time-dependent population model to ensure its internal consistency. This work shows that Gulland's (1965) virtual population analysis and Pope's (1972) cohort analysis lie at the opposite end of a continuous spectrum as a general model for a seasonally occurring fishery; Pope's (1972) approximation implies an infinitely large instantaneous rate of fishing mortality of the fish of a particular age at a particular time in a fishing season of zero length; and its implied catch equation has an undefined instantaneous rate of fishing mortality of the fish in a population, but a well-defined cumulative instantaneous rate of fishing mortality of the fish in the population. This work also highlights a need for a more careful treatment of the times of start and end of a fishing season in fish population models.