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How many fish in the sea?

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RESEARCH NOTE Number 57, 25 June 1996 ISSN 1323-5664 How Many Fish in the Sea? Since 1950 growing world de-mand for fish has meant in-creased exploitation of wild stocks of fish, crustaceans and molluscs. Between 1950 and 1970 total reported marine cap-ture landings rose from 18.5 mil-lion tons to 59 million tons.1 Since the late 1980s marine cap-ture fisheries have remained at about 83 million tons, although the overall production figure dis-guises changes in the composi-tion of the catch and the fishing effort expended to maintain it. At the Twentieth Session of the FAO Committee on Fisheries in 1993, it was reported that 69 per-cent of the world's marine stocks for which data are available were either fully to heavily exploited (44 percent), overexploited (16 percent), depleted (6 percent) or

very slowly recovering from overfishing (3 percent), and therefore were in need of urgent corrective conservation and man-agement measures.2 The purpose of this Research Note is to pro-vide a brief overview of the cur-rent state of Australia's wild fish resources.

Australian Fish Catch Australia has the world's third largest fishing zone which, at 8.94 million square kilometres, is bigger than our land area and extends 200 nautical miles out to sea. However, it is only ranked fifty-fourth in world fishery pro-duction tonnage, as our waters are relatively nutrient poor and unable to sustain large fish popu-

lations.3 Fishing is Australia's fourth largest primary industry, with a gross production of

218273 tonnes in 1994-95 and a gross value of production (GVP) of $1744 million.4 (See also Re-search Note No. 55 On High Seas?-Australia's Fishing Indus-try). The GVP is high because a significant portion of the com-mercial catch is highly priced species such as prawns, rock lob-sters, scallops and abalone.

Fisheries Management Fisheries resources are usually managed in units termed ' a fish-ery'. A fishery may be variously defined by (i) the area (e.g., the South East Fishery, which ex-tends from New South Wales down to and around Tasmania to

South Australia) or (ii) a combination of the area with a spe-cies (e.g., Northern Prawn Fishery or East Coast Tuna Fishery) or (iii) a combination of the area and the

fishing gear/methods used (e.g., Western Deepwater Trawl

Fishery). By 1991

Commonwealth and State legislation had defined about seventy fisheries.

Concerns over exploi-tation levels of Aus-tralia's fisheries re-sources have existed for over a century. A variety of fisheries management tools has been used to conserve fish stocks. These

Table 1. Status of Commercial Fisheries Resources under Commonwealth or Joint Jurisdiction

Fishery Status Catch trend

Northern Prawn Fully exploited Variable

Torres Strait Prawn Fully exploited Variable

Torres Strait Lobster Underexploited Variable

Northern Fish Trawl Underexploited by domestic fishers Unavailable

Northern Shark Underexploited by domestic fishers Stable

East Coast Tuna (Yellowfin) Uncertain Variable

East Coast Tuna (Skipjack) Uncertain, probably underexploited Declining

Southern Bluefin Tuna Overexploited Limited by quotas

Southern Shark School overexploited

Gummy fully exploited

School declining

Gummy stable

South East Fishery, 14 quota species 7 fully exploited, 1 underexploited 6 uncertain

Limited by quotas

South East Fishery, Eastern Gemfish Overexploited Limited by quotas

South East Fishery, Orange Roughy At or near full exploitation Declining, limited by quo-tas

Great Australian Bight, Shelf and Slopes Uncertain Shelf stable, slopes declin-


Jack Mackerel Uncertain Variable

Squid Probably underexploited Stable

North West Slope Trawl Fully exploited Declining

Western Deepwater Trawl Underexploited Variable

Source: Bureau of Resource Sciences, Fishery Status Reports 1994

Table 2

include area closures during spawning, minimum legal sizes, season closures, limited entry (only licence holders with spe-cific endorsement) and catch quo-tas. The Commonwealth is cur-rently emphasising 'output con-trols' such as 'total allowable catch' (TAC) to restrict the catch to sustainable levels. An annual TAC is applied to some species. The TAC is divided into 'individ-ual transferable quotas' (ITQs) within the fishery.

Georgina McGill Science, Technology, Environment & Resources Group Parliamentary Research Service

Phone: 06 277 2424 Fax: 06 277 2407

Views expressed in this Research Note are those of the author and do not necessarily reflect those of the Parliamentary Research Ser-vice and are not to be attributed to the Department of the Parlia-mentary Library. Research Notes provide concise analytical brief-ings on issues of interest to Sena-tors and Members. As such they may not canvass all of the key issues.

© Commonwealth of Australia

Status of Fish Stocks Despite these efforts, nine of our species have been assessed as overexploited.5 About twenty-two of the one hundred-odd

commercially fished species are 'considered heavily or fully ex-ploited to the extent that any higher average catches could start to affect the stock replacement (recruitment) potential of their populations.'6 The Bureau of Re-source Sciences says that al-though nine species have been assessed as underexploited, there is probably not much room for expansion of the total landed catch.7

For at least half of the commer-cially fished species there is in-sufficient knowledge to deter-mine the effects of fishing on stock levels. Table 1 illustrates the status of fisheries under some form of Commonwealth man-agement.

Sustainable fishing Substantial knowledge is required to predict sustainable fishing lev-els of our fisheries resources. The life history of each species is unique and a great deal of bio-logical information is required on factors such as growth, reproduc-tion, recruitment and mortality. Other factors such as interactions with other species; the effects of changing oceanic conditions; the effects of trawling (dragging a net across the sea floor) and pol-lution on habitats and nurseries; the effects of fishing, not only on a target species but also on its predators or prey; and patterns of behaviour, should also be under-stood.

Orange Roughy The orange roughy is an example of a species which was inten-sively fished before key knowl-edge of its breeding cycle (it doesn't become sexually mature until it is over 27 years old) and longevity (it can live to over 100 years) became widely available. Commercial fishing began in earnest for this high value species in 1986 with a recorded landed

catch of 4200 tonnes (see above). The catch peaked in 1990 at

45000 tonnes. The first TAC for the Eastern area of this fishery of 24000 tonnes was introduced in May 1990. Improved knowledge of the population dynamics of the orange roughy have seen the TACs dramatically reduced. The most recent TAC (for 1996) was for 6500 tonnes. A recent esti-mate of the long-term sustainable yield for orange roughy was around 3000 tonnes for the whole South East Fishery.8

1986 1988 1990 1992 1994








S E F O r a n g e R o u g h y C a t c h

TAC Actual

Uncertainty Many of our fisheries resources are still not well known as most of the research has been directed to the more valuable species (such as prawns and southern bluefin tuna). Hence the large number of species (fifty-nine out of one hundred) whose status is categorised as 'uncertain' or 'un-known'.

1 FAO, The State of World Fisher-ies and Aquaculture, Rome 1995, p.47

2 FAO, ibid. p.8 3 FAO, ibid. p.52 4 ABARE, Australian Fisheries Statistics 1995, Canberra 1995

5 Kailola, Patricia J. et al, Austra-lian Fisheries Resources, Can-berra 1993, pp.404-7

6 Kailola, P. et al., ibid. p.2 7 Kailola, P. et al., ibid. p.2 8 Tilzey, R. (ed), The South East Fishery, Canberra 1994, p.113