Date of Award

2001

Document Type

Thesis

Publisher

Edith Cowan University

Degree Name

Bachelor of Science Honours

Faculty

Faculty of Communications, Health and Science

First Supervisor

Dr Nicolavito Caputi

Abstract

Two of the major commercial prawn fisheries in Western Australia arc located in Exmouth Gulf and Shark Bay. Prawn fishing is the third most valuable fishing industry in WA, producing an annual income of $62 million. These two fishing regions are considered fully exploited (Fisheries WA Home Page) and careful management is needed to produce and maintain them as sustainable fisheries. The Western Australian Marine Research Laboratories have developed detailed computer models which estimate the stock abundance of the prawn fisheries. This provides information on what sort of restrictions should be made to maintain a stainable fishery. The impact of environmental factors on the daily catch rate of prawns plays a large part in the development of these models. Research conducted in this Thesis on the impact, if any, of the lunar phase on daily catch rates will help update these models. It will also provide more accurate information for fisheries management to maintain the sustainability of the prawn fishery in order that it can be fished for years to come. The data used for this Thesis consists of daily mean catch rates for the Endeavour, King and Tiger prawns for the combined regions within Shark Bay and Exmouth Gulf, obtained from the WA Marine Research Laboratories. Cloud cover data for two locations close in proximity to the fisheries, obtained from the Bureau of Meteorology, was also collected to investigate the effect of the level of moonlight. Moon phase dates and times from the Perth Observatory were also collected. All Three categories of data covered six non-consecutive years from 1972 to 1987. Time Series methods were used to remove the trend from the daily catch rate of the prawns and any cyclic component was examined. Results have been compared to the phase of the moon, to investigate the effect of the lunar cycle, and different methods are used to model the data and are compared for the best fit. Results from this investigation show that the lunar cycle has a significant impact on the daily catch rates of the King prawn in both fisheries and the Endeavour prawn in Exmouth Gulf, resulting in drops in daily catch rates corresponding to the full moon and increases at the new moon. These results can be incorporated into the refinement of the catch rate models at the Fisheries Department in Western Australia.

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