Publication Date

3-2001

Series Number

125

Publisher

Fisheries Western Australia

City

Perth

ISBN

0 7309 8453 2

ISSN

1035 - 4549

Abstract

The aim of this project was to collate all historical information regarding fishing activities relevant to the Northern Demersal Scalefish Fishery. Three primary sources of information were identified; foreign Taiwanese pair-trawl fishing activities; traditional Indonesian fishing activities; and fishery-independent (CSIRO) survey data.

The Taiwanese pair-trawl fishing catch and effort from 1980 to 1990 was concentrated into two main regions, the Broome area (120°-122°E) and the Holothuria Banks area (124°-126°E) in the north. The majority of trawls were undertaken in the mid-continental shelf region (60-100 m). The total catch of these vessels reached a peak of 4,394 tonnes in 1985. Effort levels also peaked in 1985 at 14,896 hours.

The total catch per unit effort (CPUE) of the Taiwanese pair-trawl fishery in the Kimberley showed a significant decline over the duration of the fishery from 1980 to 1990. The historical account of the catch and effort levels in this fishery indicates that total catches increased with increasing effort up to 1985, and then decreased to lower levels of catch with respect to effort from 1986 to 1990.

The Taiwanese catch rates of large lutjanids (red snappers) and haemulids (sweetlips) were greater in the eastern sector of the Kimberley region; while the catch rates of the small lutjanids (snappers), lethrinids (emperors), mullids (goatfish), nemipterids (threadfin breams), priacanthids (bigeyes) and serranids (cods) were higher in the western sector. The catch rates of Pristipomoides species (jobfish) were highest in the deep slope waters near the shelf break.

The composition of the Taiwanese catch changed markedly from 1984 to 1990 with large lutjanids, small lutjanids and Pristipomoides species comprising a substantially larger component of the catch in these latter years. The CPUE of nemipterids, priacanthids and haemulids declined significantly over the duration of the Taiwanese fishery. The CPUE of lethrinids and synodontids (lizard fish) also declined over the duration of the Taiwanese fishery.

The substantial decline in CPUE of the Taiwanese vessels by 1986 suggests that the declining catch may have resulted from a decreasing abundance of fishes in the region. Furthermore, the continued reduction (post-1986) in fishing effort by the Taiwanese fleet was likely to be a combination of low abundance of fishes and changing licensing arrangements, which made it more feasible for the Taiwanese to fish the more productive grounds of the Arafura Sea and North-west Shelf.

However, caution is recommended in interpreting assumptions regarding the status of the demersal resource based only on Taiwanese CPUE data. Comparison of the fisheryindependent survey data and the Taiwanese data indicates that considerable grading and discarding may have been taking place in the Taiwanese fishing operations. CPUE data from the Taiwanese commercial fishery can be misleading because of biases associated with variable targeting practices, changing discard and retention practices, and spatial shifts in fishing effort.

Indonesian vessels using traditional fishing methods in the Memorandum of Understanding (MOU) Box target fishes of the Lutjanidae, Lethrinidae, Serranidae and Labridae families. The species targeted by these vessels are lower-value reef-associated fish and are not commercially important to the current fleet of vessels fishing in the existing Northern Demersal Scalefish Fishery. However, large modernised Indonesian demersal longline vessels working in international waters along the edge of the Australian Fishing Zone (AFZ) adjacent to the waters of the Kimberley region, target the higher-value reef-associated species in the same families. These species are also the primary target species of vessels licensed to fish the Northern Demersal Scalefish Fishery. The degree of continuity between the demersal fish stocks in these adjacent regions is unknown.

Determination of the extent of demersal fish stocks in areas outside those currently fished is required in order to improve our knowledge of the potential exploitable demersal resource available to fishers east of 125°E in the Kimberley region and in depths greater than 150 m. This, together with improved catch and effort information, and knowledge of the biological attributes of the key species are needed in order to develop a model of the fishery that will facilitate the provision of robust stock assessment and management advice.

Number of Pages

84

Keywords

Kimberley, Fisheries, Indonesian fishers, trawling, North- West Australia, Demersal fish stocks

Disciplines

Aquaculture and Fisheries | Marine Biology | Natural Resource Economics | Natural Resources and Conservation | Natural Resources Management and Policy

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