Publication Date

7-2002

Series Number

138

Publisher

Department of Fisheries

City

Perth, Western Australia

ISBN

1 877098 04 3

ISSN

1035 - 4549

Abstract

The annual value of the pearl oyster fishery off the north coast of Western Australia is in the vicinity of 153 million dollars. Most pearl oyster fishing occurs in the Broome area. This area is managed on a quota system with a total allowable catch of 512,000 shells in 1996, during which 511,716 shells were taken. This required 12,775 hours of dive time at a catch rate of 40 shell per hour.

Drift diving practices in the Western Australian pearling industry over the last eighteen years are described and related to the number of medical incidents. The study provides a better understanding of diving schedules used by industry and related concerns for diver safety.

Historical drift diving data obtained from the Fisheries Department log books (1978 to 1990) and the Pearl Producers Association’s drift diving database (1991 to 1994) is analysed. The variation in dive practices over time is detailed. The incidence of medical disorders such as decompression sickness is too low (five or less cases per year) to apply statistical techniques; instead a descriptive approach is adopted.

Up to 36,561 dives and 24,127 hours of dive time in depths of up to 35 metres were performed each year with the greatest number of dives occurring in 1990. An increase in the number of deeper dives was observed for the years 1988 to 1993 after several years of dives predominantly below 14 metres.

Since the introduction of the Pearl Diving Industry Code of Practice in 1991, mean dive times and the total daily dive time increased and the mean interval between dives decreased for all depths. For all years approximately eight dives per day were performed, however, since 1991 there is less variation in the number of dives per day. Oxygen is now widely used during decompression stops on every second dive and the last dive for the day.

While the overall rate of non-compliance with the Code of Practice for bottom times is seven percent, there is reason for concern at certain depths, particularly 14.1-16.9 and 27.1-29 m, where the rate of non-compliance is much higher. Compliance with the ascent rates has improved over the last four years with the level of non-compliance in 1994 falling between one and two percent. Non-compliance with the total daily bottom times is negligible. The overall rate of non-compliance with the minimum surface intervals is 7.9 percent. All dives complied with the maximum number of dives allowed for the depth. There has been a reduction in the number of dive related medical incidents over the period 1991 to 1994.

Number of Pages

28

Keywords

Department of Primary Industries and Regional Development, Pinctada maxima, Broome, Shark Bay, pearl diving

Disciplines

Aquaculture and Fisheries | Marine Biology | Natural Resources Management and Policy

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