Assessment report of the Tasmanian Abalone Fishery

Environmental assessment under the EPBC Act
Department of the Environment and Heritage, December 2001
ISBN 0 6425 4858 7

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1. Overview of the fishery

1.1 Introduction
1.2 The basis of the fishery - temperate water abalone
1.3 Development of the commercial fishery
1.4 Fishing operations
1.5 Stock-structure - metapopulations and localised recruitment
1.6 Major current issues in ensuring the ecological sustainability of the Tasmanian abalone fishery

1.1 Introduction

The management arrangements for the Tasmanian abalone fishery are a set of statutory rules titled the Fisheries (Abalone) Rules 2000, which have been made under Part 3 of the Tasmanian Living Marine Resources Management Act 1995. The Rules, as amended from time to time, will run until December 2004, when they will be subject to a major review process, including public comment. The management arrangements are supported by the fishery policy document The Tasmanian Abalone Fishery Revised Policy Paper and policy revisions for 2001 - Summary of changes to the abalone fishery management plan for the 2001 fishing season. The most recent assessment of the fishery is contained in the Abalone Fishery Assessment 2000. In addition there are new arrangements for the delineation of closed areas, and some area-specific catch limits or caps and recent regulation developed to address concerns over unsustainable harvesting in some high-productivity areas.

1.2 The basis of the fishery - temperate water abalone

There are two commercially important species currently harvested in the Tasmanian fishery, blacklip abalone (Haliotis rubra) and greenlip abalone (H. laevigata). An exploratory fishery is under development for a third smaller species, H. scalaris, which is currently not covered under the management arrangements for the commercial abalone fishery. While there are differences in habitat preferences, distribution, diet, growth and other characteristics between the two commercial species, they are both sturdy herbivorous molluscs. They have a single large shell covering the body and large muscular foot, the flesh of which is the basis for this highly-valuable fishery, either live, canned or as dried or processed meat.

Sexes are separate, fertilisation is external and development and hatching of the large numbers of small eggs released by each female is relatively fast. Greenlip abalone tend to spawn in a short synchronous summer spawning period, with spawning aggregations marked. Blacklip abalone may spawn more than once in the year, with a less marked summer peak and later spawnings. The planktonic larval period, in which the larvae do not feed, is short, a period of a few days at most, with relatively localised settlement in preferred habitat where there are other abalone present. In suitable habitat, the period from settlement to sexual maturity is one in which the animals are largely cryptic, with smaller animals feeding in crevices or emerging to feed at night. Daytime emergence into more open areas coincides generally with onset of sexual maturity, which is age rather than size dependent. Growth rates vary considerably between sites and between individuals within local areas, related to food availability and other environmental factors. In Tasmania, blacklip abalone are significantly larger and faster growing to the south of the state than in the northern zone, with differences in the sizes at sexual maturity. The relationship does not seem to be as marked for greenlip, in which there is faster growth in females than males.

Both species are relatively long-lived, with a maximum age of well over 20 years in unfished populations. Blacklip abalone have been recorded at 220mm and 3.6 kg in wet weight (with a ratio of approximately 3:1 for wet weight: meat weight).

Greenlip abalone grow more rapidly and have a higher recorded maximum age and size. In Tasmanian waters they may reach sexual maturity in 3 years, with most animals mature by 4-5 years and reaching a maximum size of 150-200mm in 10-15 years.

1.3 Development of the commercial fishery

After sporadic catches in the late 1950s, commercial-scale exploitation of abalone began in Tasmania in the late 1960s. Its development can be characterised as a period of increasingly rapid development from 1963 to 1971, with a decline and subsequent recovery between 1972 and 1977. That was followed by a second period of rapid expansion and market development to a peak of 4,500 tonnes recorded catch in 1984.

There was a subsequent rapid decline in catch rates, with catches subject to a quota system implemented in 1985 of 3,500 tonnes state-wide for both species, following industry concerns over overfishing. Recorded catches remained under a combined quota for blacklip and greenlip of 2100 tonnes from 1989 to 1996, when the TAC was increased to 2520 tonnes, where it remained to 1999. The TAC was increased to 2730 tonnes in 2000 and was set at 2,800 tonnes wet weight for 2001, but was reduced later as a result of catch caps implemented in the South-east, where there were increasing concerns about the sustainability of the harvest level. The TAC for 2002 is again reduced, to 2537.5 tonnes. Recent catch limits and the introduction of zonal controls are summarised in Table 1.

Up to 1993, the bulk of the blacklip catch was taken from the west coast. Since then the majority of catches have been from what is now the eastern zone, at times at levels higher than those that occurred before quota limits were introduced. While the west coast stocks are considered to be generally likely to be recovering, other than in the more accessible areas where catch rates are again declining, there are concerns that the level of effort in the eastern zone has not been sustainable. Zonal TACs introduced in 2000 have provided improved management of the spread of effort, as have the introduction of sub-block catch caps, with adjustment of minimum size limits as required to provide protection of maturing animals in areas with different patterns of growth.

The Tasmanian harvest is estimated to be more than 25% of world wild abalone production, and is increasingly important as other abalone fisheries continue to contract. There are (2001 figures) 125 licensed divers for mainland Tasmania and the Furneaux Group, currently allocated 28 abalone units each.

There are now three blacklip management zones established, with the overall TAC of 2800 tonnes for 2001 allocated as 1,260 tonnes for the northern zone, eastern zone 1,120 tonnes and 1,260 tonnes for the western zone. The greenlip TAC is currently 140 tonnes, with caps in place in the north-east and north-west and in the Furneaux group (Table 1). Up to the introduction of blacklip and greenlip zones in 2000, reporting was for both species where they were taken together, making separation of catch rates by species difficult.

In addition to the Total Allowable Catches, managed local fishing with a reduced size limit has been permitted in what is now the northern blacklip zone on local populations that do not reach the minimum size limits otherwise in place. In the period 1989-95 there was a total of 535 tonnes of small blacklip taken - 198 tonnes of 110-132mm blacklip in April 1989, and 110 tonnes of blacklip over 118mm in May 1991.

In 1995 there were two periods for eastern Bass Strait, 21 tonnes were taken from a TAC of 100 tonnes for animals over 110mm in April; and a second period in November, with a TAC of 140 tonnes. The operation was closed after 106 tonnes had been taken, as catch rates fell and there was a concern that a high proportion of the biomass had been removed.

Limited transferability of quota units was replaced in 1991 with two licences, one an abalone diver license, the other a quota holding licence, which could be held by non-divers. Since 1993 the licences have been transferable. In 1994, Abalone Deeds of Agreement were introduced, valid for ten years, with automatic right of renewal, with other units held under annual licenses.

Licensed and AQIS-registered Abalone processors in Tasmania handle the local catch. Some now have significant investment in holdings in quota units and diving licences, with a consequent change in the proportion of owner-divers. Numbers of registered fish processors handling abalone peaked in 1993 at 43, with fewer than 10 larger-scale processors now handling 70-90% of the abalone catch.

Table 1 - Summary of recent Total Allowable Catches and zonal arrangements in the Tasmanian Abalone fishery
Species & Zone	1998	1999	2000	2001	To be implemented for 2002
Backlip -	State wide TAC	State wide TAC	East and western zones established	New Northern zone
Eastern zone			1190	1,120 132mm size limit caps in Block 13, closed late in season	857.5 , Block 13 areas capped at 350 tonnes, increase in limit to 136mm
Western Zone			1400	1,260	1,260
Northern				280	280
Total blacklip	2372	2372	2590	2660	2397.5
Greenlip -	State wide TAC implemented	68 Eastern, 80 tonnes Western, allocated quarterly	Greenlip zone, with quota is part of abalone unit	NE and NW caps	Caps in place NE, NW
Furneaux area	42 tonnes, 3.5/month	42 tonnes, quarterly cap, closed in final quarter
	148	148	140	140	140
Total	2520 (9% increase over 1997)	2520	2730	2800 -	2537.5

1.4 Fishing operations

The abalone fishery in Tasmanian waters is conducted from fishing vessels operated by one or two crew and diver tenders or, in more isolated areas, by a mother ship serving several tenders. Divers operate using compressed air delivered through a hookah system, swimming areas of suitable habitat searching for abalone. Abalone are selected individually, those estimated to be above the minimum legal size limit for the area checked against a measure and are then removed from the substrate using an abalone iron. Collecting bags are now hauled from the seabed into the tender, which in general is piloted to maintain station over the searching diver. Based on photographic and other checks of abalone catch, the proportion of undersized abalone in retained catch appears to be low, much of it attributable to minor errors in measurement.

Abalone are not processed on board, but are delivered to processors in the shell. Once on board, abalone are subject to the requirements of the catch handling and docketing system, with separate diver logs and processor returns providing an independent check and capacity for reconciliation of catch reports.

There is effectively no bycatch in the fishery, other than organisms attached to the harvested abalone. There is little other direct impact on the system, other than removal of a significant proportion of an important grazer. There has been some concern that the direct impact may be most marked where there is intensive short-term pulse fishing under special arrangements on components of the blacklip stock that do not otherwise reach the minimum size limit.

Tasmanian divers do not in general use the self-propelled shark cages used in some parts of the abalone industry. There is minimal direct impact on the habitat from which the abalone are collected. Current diving safety practices and equipment limit the effective depth of collection, but there are some indications that where they occur, deeper aggregations may be targeted where abundance is reduced in shallow water.

Fishing practices, gear and diving and boat equipment have all developed as the fishery has matured. There was, for example, an estimate of an increase in relative diver power from 0.5 to 2 in the period from 1966 to 1981 (cited in Nash 1996), with more recent developments likely to have contributed to a steady increase in efficiency (TAFI 2001). An improved understanding of the factors that may contribute to the hyperstability in catch per unit effort (CPUE) and its utility as an indicator of stock abundance will be important in the continued use of catch and effort data in stock assessments.

1.5 Stock-structure - metapopulations and localised recruitment

Greenlip and blacklip abalone fisheries in Australia's temperate waters operate on stocks that are spatially highly structured. Local population units at scales of a few km or less are linked in a complex of metapopulations, at scales of hundreds of km, within the exploited stocks under Tasmanian jurisdiction. The degree of linkage to abalone stocks in adjacent jurisdictions is not yet well understood, although it is likely to be closer for those in the islands of the eastern and western strait than further to the south.

Larval abalone may travel considerable distances even in the limited time in which they remain viable and active in the water column, but the bulk of recruitment appears to be quite local. While there are areas in which recruitment may be largely from elsewhere, with the potential for localised source-sink relationships, recruitment from out-of-area is likely to be very limited or sporadic. At the larger scale, it is in general unlikely to be sufficient to compensate for high levels of fishing mortality or to provide short-term recovery of local populations where exploitation levels have resulted in recruitment failure.

Understanding of genetic indicators of fine scale population structure in blacklip abalone in Tasmania is currently under review as part of a broader national forensic program. It is likely that with the current input and output controls the exploited stocks overall are not under direct threat. There is, however, clearly a present risk of serial depletion and recruitment failure at the scale of sub-blocks or finer in some of the 49 blocks currently used for data collection and monitoring. An improved understanding of the spatial scale of population structure has important implications for the scale at which management measures are implemented.

1.6 Major current issues in ensuring the ecological sustainability of the Tasmanian abalone fishery

Recent development in fisheries management have highlighted the particular challenges that face management for species in which there is a high level of persistent spatial structure and fine scale differentiation in growth, fecundity and other population parameters. While there is limited movement of sub-adults and mature individuals associated with breeding aggregations, there is no large-scale migration or seasonal movement. Ranges are typically extremely limited. Most individuals will spend their entire lives within a relatively short distance of their recruitment site, which is likely to be within a short distance of the larval source. Homogenous application of management controls at a scale significantly larger than the underlying population units carries with it a risk of localised and serial depletion, a pattern which has been repeated in several abalone fisheries worldwide.

Responses to fishing pressure include initial compensatory growth, with increased productivity as populations are reduced. Reduced density and selective reduction of aggregations may result in depensatory effects, including (non-linear) reduction in fertilisation of gametes, reduced settlement of larvae and possibly reduced initial juvenile survival. There is emerging information on increased variability in larval recruitment and increased likelihood of local recruitment failure, with smaller local populations requiring protection of a relatively higher proportion of egg production.

While it is one of the key issues in determining appropriate levels of harvest and the form of protection, as in other fisheries, the stock-recruitment relationship is poorly understood. A highly precautionary approach is essential where there is a risk that local populations have been, or are likely to be, subject to harvest levels that could result in result in growth- or recruitment-overfishing.

There was an increase in overall TAC levels in the period up to 1999, followed by a decrease in 2001, proposed again for 2002, reflecting reduced catch limits in the south-east. The most recent assessment of the Tasmanian blacklip and greenlip fisheries under Tasmanian jurisdiction is for the 2000 fishing season (TAFI 2001). It indicates that, while the development of zonal catch limits from the 2000 fishing season has improved the distribution of effort between zones, there have been declines in abundance of abalone in some blocks in the Eastern Zone.

The recent management measures are more conservative and are likely to be sufficiently responsive to handle any overall decline. It will be some time before the effects of these controls over shifts in effort and other measures are fully reflected in the status of the harvestable component of the populations and there are continuing concerns for some sub-block components.