In pursuit of cost-effective fisheries enhancement of New South Wales blacklip abalone, Haliotis rubra (leach) fishery.

ABSTRACT The diverse and often complex essential components of successful marine stock enhancement are briefly reviewed. Progress on a project to enhance the New South Wales blacklip abalone (Haliotis rubra) fishery is discussed to demonstrate that for sedentary reef invertebrates such as abalone, successful enhancement entails an understanding of recruitment and production limiting factors. These include age and size specific growth and mortality rates. These variables encompass the influence of other species within reef ecosystems, especially predators and species that compete directly with them for space, shelter and food. This discussion is also used to demonstrate that such difficult projects can be facilitated and refined using a simple bio-economic model centered on two interdependent tasks. The first is to minimize net costs per unit of additional sustainable production generated by enhancement. The second is to determine the minimum amount of additional sustainable production required to render a project cost-effective. This first task has, as expected, proven complex and its resolution protracted and expensive, requiring innovative biotechnology and a comprehensive knowledge of the natural biology of blacklip abalone. This discussion principally reflects the perspective of the direct potential beneficiaries of abalone fisheries enhancement, namely commercial and recreational fishers and does not deal extensively with wider views and interests of other stakeholders, namely relevant government agencies and NGOs and the general public.

KEY WORDS: fisheries enhancement, abalone, Haliotis rubra

INTRODUCTION

Generalized Theory and Practice of Marine Fisheries Enhancement

Blankenship and Leber (1997) identified 10 key components as essential for responsible marine stock enhancement. These included the need to: (1) prioritize and select target species for enhancement; (2) develop a species management plan that identifies harvest opportunity, stock rebuilding goals and genetic objectives; (3) define quantitative measures of success; (4) use genetic resource management to avoid deleterious genetic effects; (5) use disease and health management; (6) consider ecological, biological and life-history patterns when forming enhancement objectives and tactics; (7) identify released hatchery seed and assess stocking impacts; (8) use an empirical process for defining optimum release strategies; (9) identify economic and policy guidelines and (10) use adaptive management. Blankenship and Leber (1997) reviewed three finfish case studies to verify that this responsible approach to marine stock management is practical.

In a recent review of the 100 y history of fisheries stock enhancement projects, Molony et al. (2003) concluded that most have had little or no demonstrated success. They ascribe this to undue preoccupation with seed production technology and failure to identify and/or control underlying reasons why the targeted fisheries were underperforming or not meeting management objectives. They also concluded that stock enhancement has often been applied in isolation from other fisheries management tools and have ignored broader ecosystem perspectives. To address these shortcomings, the authors proposed a flow-chart implementation model comprising four sequential steps: (1) review all relevant ecological and stock status management fisheries information; (2) make a comparative evaluation of all relevant fisheries management tools with a potential to meet targeted objectives; (3) instigate a scientifically based pilot enhancement program with clear appropriately targeted objectives and (4) if warranted by outcomes of the pilot program, initiate a follow-up full scale commercial program.

What follows is a discussion of a research project that has attempted to achieve sustainable and cost-effective enhancement the blacklip abalone (Haliotis rubra, Leach) fishery in New South Wales (NSW), using hatchery-produced seed. This research, much of which is reported in more detail by Heasman et al. (2004) in a contract research report, has collectively addressed most of the important issues and elements identified by Blankenship and Leber (1997). Its implementation over a 3-y period generally conformed to the first three sequential steps prescribed by Molony et al. (2003). Towards the end of the third year of pilot seeding operations (step 3), an extensive reappraisal of the project was made. This comprised a repeat of steps 1 and 2 (review of all other relevant fisheries biology and management information) and incorporated a wealth of practical experience gained, together with findings of an extensive array of complementary laboratory and field-based larval and juvenile seeding experiments. It also culminated in the development of bioeconomic benefit and cost and risk assessment model.

Previous Attempts to Enhance Wild Stocks of Abalone With Hatchery-Produced Seed

The efficacy of enhancing wild stocks of abalone with hatchery-produced seed has been investigated internationally and within Australia. As stated by Shepherd et al. (2000), "Release of larvae and juveniles has often been proposed as a panacea for rehabilitating depleted or over exploited reef." Seeding of juveniles has been practiced in Japan for several decades with some success (Kojima 1995, Masuda & Tsukamoto 1998). Larval release has been practiced sporadically in Mexico since the 1960s (Ortiz-Quintanilla 1980). Prior to this study, research in NSW into the efficacy of previously developed techniques for the release of seed abalone was limited to larval releases in Twofold Bay by a company Abalone Shellfish Enterprises Pty Ltd. (Keesing et al. 1994). Although survival of the larvae was not monitored, a localized high density aggregation of sublegal size abalone was observed at one release site several years later (Ross Werner, pers. comm. 1998). This information, though anecdotal, encouraged collaborative involvement of total allowable commercial catch (TACC) quota holders in this project as mediated through the NSW abalone management and advisory committee (ABMAC).

Larvae of H. rubra and greenlip abalone (Haliotis laevigata, Donovan) were released at different densities in South Australia by Preece et al. (1997). Generally low and strongly density-dependent survival in the range 0.02% to 7.8%, occurred 6-7 d after settlement. Such strongly density-dependent rates of mortality of larvae and early postlarvae were also reported by McShane (1991) in relation to naturally recruited stocks of H. rubra in north eastern Victoria. On the basis of these reports, Shepherd et al. (2000) recommended against larval seeding, as did Schiel (1993), based on similar results with seeding of H. iris (Paua) larvae in New Zealand.

In a review of experimental releases of 7-mo-old (12 mm) hatchery-produced H. rubra in Tasmania, Shepherd et al. (2000) concluded that very high rates of mortality over the first few weeks were due mainly to handling stress. They also concluded that high mortality up to 1 y after release was caused by persistent density-dependent mortality factors and predator naivety.

Status of the NSW Abalone Fishery and Scope for Enhancement

The NSW abalone fishery is based entirely on H. rubra and is largely confined to the southern half of the state. Annual catch (Fig. 1) peaked at about 1200 t in 1971/1972, and remained above 600 t through to the early 1980s. Since 1973 a succession of fishery management initiatives (Fig. 1) have been implemented. These have included a reduction in effort through license regulation, limiting catch by quota allocation and introduction of size limitations. Regional fishing closures were also imposed between Port Stephens (32[degrees]42'S; 152[degrees]10'E) and Jervis Bay (35[degrees]03'S; 150[degrees]44'E) after a major depletion of stocks by the disease Perkinsus between 2000 and 2002. A TACC of 370 t was first introduced in 1989. Subsequently it has been progressively reduced to 333 t in 1996, to 305 t in 2000 and down to its current level of 281 t in 2003 (NSW Fisheries 2004). Subsequently, it was further reduced to 208 t in 2004 and to 1130 t in 2005.

A common anecdotal report of H. rubra fishers over this 30-y period is that many formerly productive areas of reef, typified by foliose algae (seaweed) and associated complex communities of fish and invertebrates including abalone, have undergone a transition to "barrens." These bare rock areas typically carry high densities of the black (=purple) sea urchin, Centrostephanus rodgersii, (J. Smythe, pers. comm.). Such observations are compatible with the findings of Andrew and Underwood (1992) that densities of H. rubra and C. rodgersii are negatively associated and by the finding of Shepherd (1973) that continuous grazing pressure, exerted by dense aggregations of C. rodgersii, can degrade complex community reefs. Andrew and O'Neill (2000) and Worthington and Blount (2003) estimate that barrens habitat constitute an average of 40% to 50% of near-shore reef areas in NSW.

Whereas the massive extent of barrens habitat in NSW appears to offer scope for rehabilitation of depleted H. rubra stocks, natural recolonization is probably limited by the combination of competitive exclusion by C. rodgersii and the very restricted dispersal of H. rubra larvae from their parents (Prince et al. 1988). Hamer (1982) and Andrew et al. (1998) demonstrated that habitat improvement by way of culling urchins from urchin dominated reef in Southern NSW resulted in rapid recovery to abalone densities typical of high producing reef within 3-4 y. The recovery process also included a dramatic increase in the coverage and biomass of foliose algae and an associated increase in biodiversity of floral and faunal assemblages. Nevertheless, urchin culling is very labor-intensive and colonization is limited to small localized areas. Accordingly, the task of culling C. rodgersii from up to 50% of coastal reefs commercially fished for abalone in NSW, that collectively comprise about 5000 ha, is daunting.

By contrast, mass hatchery production and release of seed H. rubra provides a potentially powerful means of rapidly enhancing depleted abalone subpopulations over extensive areas. Seeding also addresses other factors limiting recruitment and consequentially sustainable yields. Such factors include the combined effects of commercial, recreational and illegal fishing pressure and diseases such as Perkinsus that has devastated stocks north from of Jervis Bay to Port Stephens (Worthington 2002). Other recruitment limiting factors are pollution and competitive exclusion especially of settlement stage larvae and small postlarvae by a diverse array of large common surface grazers. These comprise other gastropods including several ubiquitous turban shell species and a comparable array of urchins additional to C. rodgersii. In a recent experiment (Heasman unpublished data) high densities of the common tent shell (Astralium tentoriformis) or of Turbo torquatus in high densities were found to reduce yields of 1-wk-old H. rubra postlarvae, seeded as larvae onto natural CCA (crustose coralline algae) rock settlement substrates, by 98% and 94% respectively. In the same experiment, the presence of either black urchins (C. rodgersii) or adult abalone reduced postlarval yields by similarly high margins of 90% and 78% respectively.

SEED PRODUCTION AND DEPLOYMENT TECHNOLOGY

Improved Year-round Availability of Ripe Broodstock for Induced Spawning and Hatchery Production

Attempts to immediately produce viable eggs from wild-caught adults were unsuccessful, with a significant number of viable eggs (1.5 million) being produced on only 1 of 42 occasions. Over the same period seven successful inductions of spawning were achieved using broodstock acclimatized over longer periods in ambient flow-through seawater tanks. These yielded 26.8 million eggs (mean fecundity 1.12 million eggs/spawner) that in turn yielded 13.3 million competent larvae. However, these spawnings and subsequent hatchery operations occurred at irregular intervals and were largely limited to the spring to early summer natural breeding season of 14. rubra in NSW.

For the first time in Australia, greatly improved access to ripe, ready-to-spawn broodstock was achieved with captive stock conditioned in a recirculating seawater system operated at 15 [+ or -] 2[degrees]C. These stock were originally collected from seven localities between Port Stephens, 150 km north of Sydney, to Disaster Bay (37[degrees]15'; 149[degrees] 58'E) near the Victorian border. Half (17) of 34 spawning induction operations, spread throughout the year, were successful and yielded 59.3 million eggs. Mean spawning response rate using these conditioned broodstock was 11% (85 out of 785 females). Mean fecundity ([+ or -] s.e.) was 1.25 [+ or -] 0.49 million eggs/ spawner (range of 42,000-4.0 million). A total of 24.0 million competent larvae were produced and used for larval seeding experiments or for nursery production of juvenile seed and related experiments. Yields of 7-8-d-old competent larvae from eggs averaged 40% (range 8% to 71%), which was consistent with rates routinely reported by commercial hatcheries in Australia. Subsequent yields of 6-9 mo old juvenile seed from competent larvae averaged 5.7% and varied greatly from 8% to 75%.

Hatchery and Nursery Technology Development

The low and inconsistent yields of juveniles raised the need for better knowledge of and control over nursery production. A mean shell length of about 1.5 mm was identified as the minimum size needed to ensure trouble free weaning of postlarvae onto finely ground particulate diets (Adam and Amos P/L, South Australia). Postlarvae grew at an exponential rate regardless of season or seed density (Fig. 2). Plate residence time from settlement to 1,500 Dm ranged widely. Batches reared in summer/early autumn required only 30-35 d. At the other extreme, winter and early spring reared batches required 50-72 d. Growth rates thus appeared primarily dependent on seasonal temperature.

An important feature of growth on diatom plates is that it continues exponentially until either food runs out (plates grazed out), in which case it abruptly stops, or when postlarvae reach a mean shell length of 1-2 mm at which time they can be successfully transferred to raceways for weaning onto artificial diets. As illustrated in Figure 3, production batches that were inadvertently allowed to exhaust diatom films after having reached the minimum weaning size, stopped growing and starved before being harvested from nursery plates. Substantial and sometimes catastrophic losses of postlarvae occurred as a consequence of such episodes. This was probably caused by combined stresses of starvation, anesthesia and handling when harvested and transferred to shallow exposed raceway habitats for weaning. The size and age at which growth stopped and starvation began appeared inversely related to initial density of competent larvae seeded onto the plates.

[FIGURE 3 OMITTED]

Results of Experiments Conducted to Improve the Reliability and Cost Efficiency of Large-Scale Production of Juvenile H. Rubra Seed

Results of one experiment to investigate effects of variable larval density of 500-4,000 larvae per plate (0.15-1.2 [cm.sup.2]) on settlement, metamorphosis and subsequent growth on conventional nursery plates showed that yields of postlarvae (Fig. 4) peaked after 4-7 d. They also showed that yields increased from 26% to 71% with increasing seeding density. However, from day 7-28 after seeding, survival across all seeding densities progressively converged to a common rate of about 20% that persisted until the termination of the experiment at day 56. Growth (Fig. 5) remained independent of initial seeding density up to 14 d, averaging about 14 [micro]m per day. Subsequent growth became progressively more density dependent. By day 56, growth rates at residual densities of 10, 100 and 1,000 postlarvae per plate averaged about 40, 30 and 22 [micro]m/day respectively. Minimum mean shell lengths of about 1,400 [micro]m at day 56, attained at the highest initial density of 4,000 postlarvae per plate, were nevertheless found to be acceptable for the purpose of early weaning of postlarvae. These improved techniques provide scope to increase output per plate from one to at least four batches per year and to increase yield densities to a consistent range of up to 500-1,000/plate, thereby greatly raising annual yield/plate/year up from 30-80 up to a range of 2,000-4,000.

[FIGURES 4-5 OMITTED]

In another experiment, effects of temperature on settlement, metamorphosis and early postsettlement growth and survival were investigated. Settlement rates on natural CCA coated rock settlement substrates ranged from 20% to 40%. Peak settlement and yields of postlarvae occurred at about 17[degrees]C (Fig. 6). During the first week after settlement growth rates of postlarvae (Fig. 7) increased progressively from zero at 10[degrees]C to a peak of ~30 [micro]m/day at 23[degrees]C, but then fell dramatically back to zero with a further rise in temperature to 27[degrees]C. Effects of temperature on growth of four juvenile age/size classes of H. rubra (Fig. 8 a to d) showed that further downward shift in optimum temperature from about 17[degrees]C to 15[degrees]C occurs with progressive age and size in juvenile H. rubra. Results also demonstrated that moderate to high rates of settlement and subsequent growth and survival could be achieved year-round on the central coast of NSW at mean monthly sea temperatures in the range 16[degrees]C to 22[degrees]C but that successful year-round hatchery-ambient temperature nursery production would be limited at more southern sites subject to sea temperatures below about 14[degrees]C.

[FIGURES 6-8 OMITTED]

Transportation and Storage of Juvenile H. Rubra

The need to transport and deploy batches of up to several hundred thousand 6-9-mo-old (5-15 mm)juvenile H. rubra up to 500 km from the hatchery prompted the development of suitable storage and transportation methods. Key issues addressed were whether stock should be stored and transported wet or damp, optimum temperatures for storage and transportation and the maximum duration over which they can be safely stored and/or transported without compromising the postrelease vigor and survival. Juvenile H. rubra (mean SL, 14 mm) previously held at ambient temperatures of 18[degrees]C to 22[degrees]C survived at acceptable rates (i.e., above 80%) for up to 48 h when stored damp in pure oxygen between 13[degrees]C and 16[degrees]C. The best 48 h survival rate of 95% was achieved with damp storage at 14[degrees]C. Generally poorer rates achieved with wet transportation were ascribed to declining physiochemical conditions, especially dissolved oxygen that rapidly fell below an acceptable threshold of 95% saturation.

Field Deployment and Postrelease Growth and Survival

Improved methods of seeding hatchery-produced H. rubra larvae and juveniles onto natural reefs were developed, and the effectiveness of these methods to deliver competent larvae and juveniles to reefs tested. Several alternative methods of monitoring the settlement and early survival of larvae, postlarvae and juveniles within their respective release areas were developed. Field experiments were used to demonstrate the ability of juveniles to rapidly disperse from points of release and provided greater insight into factors that must be considered when attempting to estimate long-term survival of seeded stock.

In excess of 24 million larvae and nearly 900,000 juvenile H. rubra, most falling within the "button" mean size range of 6-18 mm SL, were seeded to 57 sites within six locations along the NSW coast. The survival and growth of larvae and juveniles were monitored for periods up to 30 mo. Short-term (<2 mo) sampling was used to investigate movement of juveniles and to compare alternative sampling techniques. The best survival for seeded larvae a year or more after release was 125 out of 1.1 million (1 in 8,800) recorded 553 days after release. As in earlier abalone seeding studies (Preece et al. 1997) seeding of ready-to-settle larvae was shown here to be fraught with practical difficulties and with very low rates of survival projected to yield less than 1 in 20,000 to a legal shell length of 115 mm.

Juveniles were mainly deployed as clusters of 700-2,500 in predator protective release devices initially comprising CCA coated rocks within wire mesh cylinders. These were superseded by rectangular boxes comprising sections of PVC down-pipe. Mean survival rates 1-2 y after release ranged from 0% to 4%. Average growth rates were similar among and between sites with juveniles expected to reach maturity (>90 mm SL) after 2.5-3.5 y, and projected to reach legal SL of 115 mm after 4 y. These low survival rates prompted a compilation and analysis of published age and size-specific mortality data for H. rubra (Table 1, Fig. 9) that were used to estimate yield per recruit and related parameters for a wide range of age/size classes of seed from competent larvae to 6-y-old adults (Table 2). A review of published ecological information on H. rubra revealed that, although 1-4-wk-old wild postlarvae occur at natural densities of up to several 1000/[m.sup.2], and 6-mo-old juveniles at up to 30/[m.sup.2], survivors of these groups converged to a common narrow density range of 1-3/[m.sup.2] as 15-30 mm, 1+ year olds (Prince et al. 1988, McShane 1991, Shepherd et al. 2000). It was then postulated that if natural survival rates of 6-9-mo-old button size (7-15 mm) juveniles, through to the minimum legal size, of 1 in 20-30 are to be achieved with hatchery-produced seed, then such seed should be sparsely deployed at densities matched to the food based carrying capacity of CCA rock habitats of this size/age class of juveniles, rather than in large dense clusters as previously practiced.

[FIGURE 9 OMITTED]

Evaluation of Postlarvae as an Alternative to Competent Larvae for Seeding

Major practical advantages of using week old postlarvae rather than settlement stage larvae for seeding operations were also identified in three laboratory experiments. Results (Fig. 10) showed that postlarvae can be readily seeded at very high densities onto small CCA coated pebbles (vector rocks) and retained for up to 8 d without significant restriction of growth or ability to rapidly disperse into simulated small boulder habitats after release. Carrying capacity of CCA rock habitat declines reciprocally with exponential increases in the biomass of individual H. rubra, falling to densities levels of 1,000-2,000/[m.sup.2] for 2-mo-old (1.5 mm) postlarvae (Fig. 11), and by extrapolation, to levels of around [less than or equal to] 30/[m.sup.2] for 6-mo-old (7 mm) juveniles. The latter was consistent with above cited peak densities reported for equivalent wild H. rubra. Surface grazing on CCA thallus and associated epibiota remains the primary food source of juveniles up to at least 10 mm SL and is only then progressively supplanted by drift seaweed over the following 1-2 y in individuals up to at least 35 mm SL (Shepherd & Daume 1996). An important aspect of these findings is that they were consistent with the earlier-cited convergence of l+-y-old wild juveniles to densities of 1-3/[m.sup.2]. These observed carrying capacity limitations of CCA rock habitats occurred in the absence of other important density and survival limiting factors, namely competition from other surface grazers such as urchins and other gastropods and predation especially by finfish especially wrasses (Shepherd & Turner 1985, Shepherd 1998), wirra cod (Acanthistius ocellatus) and morwong (Cheilodactylus fuscus) (Heasman, unpublished observations) and large invertebrates including starfish, rock lobsters, large crabs and octopus (Shepherd & Breen 1992, Shepherd 1998). Accordingly, the carrying capacity of CCA rock habitats can be largely ascribed to nutritional factors in juveniles up to 10-mm SL and an important but diminishing factor in larger juveniles to 35-mm SL and around 18 mo of age.

[FIGURE 10 OMITTED]

On the strength of these findings, a final reef seeding experiment was conducted at Disaster Bay near the NSW/Victorian border. Two deployment treatments; the first consisting of 10 evenly spread clusters of 100 juveniles, averaging 15-mm SL, and the second a central cluster of 1,000 juveniles of the same size, were each deployed over three replicate 113 [m.sup.2] sites. This represented a targeted seeding density of less than 10 juveniles/[m.sup.2], typical for this size/age class of juveniles on healthy productive reef (Prince et al. 1988, McShane 1991, Shepherd et al. 2000). A year later, mean survival across sites seeded with 10 x 100 juveniles was within the expected range for equivalent wild stock, namely 12.5% (range 5% to 23%), whereas that of the alternative clustered treatment was only 3.8% (range 0% to 9%).

DEVELOPMENT OF A BIO-ECONOMIC MODEL FOR ENHANCING THE NSW ABALONE FISHERY

Many of the earlier mentioned findings were used to develop a comparative bio-economic model for H. rubra fisheries enhancement using alternative age/size classes of seed. The model is based on the most fundamental of economic equations:

Profit = Revenue - Total costs

where:

Revenue = long-term average beach price for abalone x additional sustainable catch generated by seeding

Total costs = costs of all elements of production and deployment of seed but not including those of monitoring the wider environmental consequences of seeding, especially impacts on plant and animal communities and on the genetics of extant wild H. rubra populations. Key inputs, assumptions and rationale thereof associated with this model as follows:

* Additional sustainable annual catch targeted is 300 t([congruent to] 1 million, 120 mm abalone @ 300 g). This is valued at AU$15M based on an assumed average beach price of AU$45/kg (AU$15 ea.) (ABARE 2003). The rationale for nominating an enhancement target of an additional 300 t/year, is that it would restore the total commercial catch to a range of 500-600 t/year, which approximates the median annual catch of the fishery since its the inception in 1960 (Fig. 1). It is likely that enhanced production of H. rubra can only occur at the expense of other reef surface and drift seaweed grazers that compete with H. rubra for food and space. However, when it is considered that 300 t of additional H. rubra equates to about 0.6% of the biomass of its most important competitor, the black sea urchin, C. rodgersii, estimated at 40,000-50,000 t by Worthington and Blount (2003), such impacts are likely to be sustainable.

* The assumed mean age and weight of released abalone at harvest are 5 y and 300 g respectively. This estimate constitutes a median growth rate for H. rubra populations throughout NSW, based on regional specific rates originally derived from tag and recapture size data reported by Hamer (1982) and re-evaluated by Worthington and Andrew (1997).

* The five size/age classes of seed (Tables 2-3) and associated assumptions were as follows:

1. Competent larvae. It was assumed that only 1 in about 20,000 seeded larvae would survive to market size adults in compliance with yield per recruit predictions presented in Table 2. The latter, including a mortality rate of ~95% in the first week, are based on published instantaneous mortality data for wild H. rubra presented in Figure 9 and assume that seeding does not significantly reduce natural recruitment. Apart from enormous logistical problems of deploying the requisite 20 billion larvae over hundreds of hectares of juvenile habitat by SCUBA under calm sea conditions, the production of the 2 billion larvae required would entail the reproductive conditioning and induced spawning of about 30,000 captive female broodstock (Table 3). The latter is considered impractical if not cost prohibitive.

2. 0.4-mm postlarvae. It was assumed that postlarvae would be preseeded onto vector rocks thereby circumventing otherwise prohibitively costly and difficult production and deployment problems plus very high postrelease mortality losses sustained by larvae and postlarvae during the first week in the wild. An assumed yield per recruit rate of 1 harvestable H. rubra per 2,000 seeded postlarvae is based on data presented in Table 2 and incorporates an experimentally determined postsettlement mortality rate of 50% in the absence of predators. This particular mode of seeding would require year-round reproductive conditioning and induced spawning of about 3,000 captive female broodstock (Table 3). The latter, although daunting, is considered practicable and affordable. The most critical limitation of this seeding strategy is uncertainty surrounding the fact that it has not been experimentally trialed in the field let alone on a commercially significant scale.

3. 2-mm postlarvae. An estimated yield per recruit of 1 harvestable 14. rubra per 157 ex-diatom nursery plate 2 mm postlarvae is based on reported age specific natural mortality data presented in Table 2. Production of requisite 157 million 2-mm postlarvae, needed to raise sustainable fisheries yields by 300 t, would be cost prohibitive using current commercial hatchery technology. Although the scale of such seed production dwarfs that of existing commercial hatcheries in southern Australia, it is nevertheless considered to be practicable and affordable provided much more space, labor and cost efficient hatchery and nursery technologies, developed in this project, are used. Using such technology would entail the reproductive conditioning and induced spawning of 3,200 captive female broodstock. Again, the most critical limitation of this seeding option is uncertainty surrounding the fact that it has not been experimentally trialed in the field let alone on a commercially significant scale.

4. 8-mm juveniles ("buttons"). An estimated yield per recruit of 1 harvestable H. rubra per 26 "buttons" is based on mortality data of wild H. rubra data presented in Table 2. Production of the 26 million buttons required would entail the reproductive conditioning and induced spawning of 2,600 captive female broodstock (Table 3). As with the previous two alternative seed classes, this relatively large broodstock requirement is considered both practicable and affordable as is seed production using new high efficiency hatchery and nursery technology developed during this project. However unlike week-old postlarvae and 2-mm postlarvae, commercial-scale low density dispersed seeding methods for this class of seed have been fully developed and very extensively trialed in the field over the past 5 y.

5. 40-mm juveniles. An estimated yield per recruit of 1 harvestable H. rubra per 15 seed comprising 40 mm juveniles, is based of mortality data of wild H. rubra data presented in Table 2. Production of the 15 million required juveniles would entail the reproductive conditioning and induced spawning of 2,900 captive female broodstock (Table 3). As with the previous three alternative seed classes, this broodstock requirement, though relatively large is considered both practicable and affordable. The extremely large seed production requirement of 15 million 40 mm juveniles equates to 150 t live weight, which is likely to be cost prohibitive being about twice the annual output of Australia's largest producing farm in 2004/5 (J. Hall, King Island Abalone P/L, pets. comm.). Further factors mitigating against these large seed are daunting logistical difficulties of handling, transporting and dispersion in the field.

Information provided in Table 3 summarizes and compares key logistical, technical and cost issues in producing and deploying the five alternative size/age classes of seed. It also compares utility of producing each size/age class using either conventional single annual batch hatchery production with much more efficient technology developed during this project.

Predictions regarding use of button size juveniles as seed are particularly encouraging in that the potential margin for profit forecast is so handsome that break-even enhancement would still occur even if survival of hatchery-produced seed fell as low as 10% that of wild counterparts. Alternatively, if average survival rates of say 25% to 50% of comparable wild stock are achievable, profitable seeding of depleted populations of abalone could still be attained at much smaller scales of operation than applied to this model, which assumes 100% parity with survival of wild counter parts.

The model also predicts that seeding of larvae is likely to be unprofitable and also casts doubt on the economic viability of large-scale seeding of natural reef using advanced (18-mo-old, 40-mm) juvenile H. rubra. This is not to say that cost-effective seeding of more advanced juveniles cannot be achieved under reduced competition for food and shelter from competitors and/or reduced predation. For example, R. Day (pers. comm.) reported 50% survival of green lip abalone (H. laevigata) 1 year after being seeded as 28 mm SL juveniles onto reefs constructed from natural reef rocks in shallow, high food flux (drift seaweed) sea-grass beds.

RECENT DEVELOPMENTS

Continuing research of cost-effective technology for enhancing the H. rubra fishery in NSW and elsewhere in southern Australia is being pursued under a 12-mo extension of this project. Continuing research towards improving postrelease survival is now being undertaken by A. Underwood and G. Chapman (Sydney University). All field experimentation has been confined to the Port Stephens area because stock translocation limitations imposed by an outbreak of the disease Perkinsus that devastated the region's H. rubra stocks by an estimated 90% between 2000 and 2002 (Daly 2004). This research is further addressing a number of factors likely to influence postrelease survival that includes evaluation of:

* clustered and dispersed seeding of button size (5-15 mm) juveniles,

* size of juveniles within the button size range on postrelease survival,

* urchin shadows or similar devices for reducing early postrelease mortality,

* multiple low-density seeding of sites and single higher density seeding, and

* natural and artificial diets on postrelease performance of seeded juveniles.

Complementary research being undertaken by NSW Fisheries includes development of a novel method of achieving low density dispersed seeding. This has involved the design and manufacture of small, predator-protective release capsules that accommodate only 10-20 button size seed. These miniaturized deployment devices can be broadcast over entire juvenile habitats of depleted reefs during daylight hours from surface craft, thereby negating costly deployment by divers. A key design feature of the capsules is that they pack together to form complete level platforms. This feature together with the use of intensive light, encourages in excess of 95% of the "buttons" to self-load into the capsules (Heasman, unpublished data). Once loaded, the "buttons" can be maintained within the capsules in good health for several days of storage awaiting either more favorable sea and weather conditions or off-road transportation to sites up to several hundred kilometers from the hatchery. The latest advance in this technology has been the development of two alternative environmentally friendly forms of the capsule. One is manufactured from a specially developed biodegradable resin and the other of aluminum that will corrode away in seawater within a year.

In late July and early August 2005, almost 60,000 button size (average SL 11 mm) juveniles were stocked into aluminum dispersion release devices. Approximately 560 devices containing an average of 17 "buttons" were used to seed each of six 1,000 [m.sup.2] sites marked by surface buoys. All six seeded and an additional six unseeded control sites were located along an 8 km section of coast on the southern side of the Tomaree Peninsula at Port Stephens. All sites were considered typical juvenile habitat comprising a high component of crustose coralline algae coated boulders, immediately adjacent to locations identified by local commercial fishermen to have consistently supported good catches prior to Perkinsus epidemics that decimated these stocks between 2000 and 2002. Broadcast seeding of the capsules from a 10-m vessel required only a few minutes per site. Aims of this long term experiment are to evaluate the commercial utility of dispersed seeding of depleted stocks and to assess genetic impacts of such releases.

Possible deleterious genetic consequences of seeding large numbers of juveniles produced in the hatchery from relatively small number of parents have also been addressed in the current project through the development and assessment of triploid H. rubra. Chemical induction techniques yielding almost 100% stable triploids were developed. These triploids were subsequently shown to be reproductively sterile and although no whole weight growth advantage could be demonstrated in triploids up to 37 mo old and 70 mm SL, yield of saleable flesh was 20% greater than in full sib diploids (Lui 2005). Furthermore, one particular treatment used to induce triploidy was found to have inadvertently produced significant numbers of tetraploid individuals paving the way for future research to produce 100% functionally sterile triploid progeny by fertilizing eggs from diploid females with sperm of a tetraplod males (Liu et al. 2004).

CONCLUSION

Considerable progress towards cost effective enhancement of the NSW abalone fishery has been made through reducing costs of production and transportation of H. rubra seed and from the identification of button size, 6-9-mo-old juveniles as the most appropriate class of seed for enhancing depleted subpopulations. The detection of a major apparent flaw in the use of clustered deployment of these juveniles and development of low density dispersed seeding technology is also a significant step forward. This will hopefully enable seeding to be aligned with surface grazing based on carrying capacity limitations of CCA rock habitats in relation to juveniles up to at least 12 mo old and 25 mm SL.

Nevertheless, many other major questions and issues remain to be addressed. Foremost is the issue of matching seeding operations with inherent capacities of individual depleted reefs to sustainably yield higher quantities of marketable 4+-year-old adults. Division of the NSW abalone fishery into six geographical management zones (Fig. 12) reflects a very steep south to north gradient of decreasing abundance of H. rubra. Almost 80% of TACC quotas are taken on average from zones 4-6 that collectively fall within 150 km of the Victorian border (Cape Howe). At the opposite extreme, catches from zone 1, that stretches 600 km north from Jervis Bay to the Queensland border, have fallen from around 20% of total commercial landings in the mid 1980s to only about 5% over the recent years (Anon. 2002). The relative importance of such interactive factors as recruitment, availability of food, primarily drift seaweed (Shepherd & Hearn 1983), competition for food and shelter and differential mortality factors, including natural predation and fishing pressure, plus disease (especially Perkinsus) on this changing pattern of abundance, is not well understood.

Higher sea temperatures in the north are undoubtedly a greater constraint to full development of gonads and hence to successful spawning and recruitment in some years. These processes require at least 1,200 degree days at moderate temperatures in the range 8[degrees]C to 18[degrees]C (Grubert & Ritar 2003). Likewise, losses of up to 90% of stocks in the Port Stephens area of zone 1 in 2000 and 2002, attributed to stress-induced susceptibility of H. rubra to the disease Perkinsus, could, together with impaired breeding, be linked to increased water temperatures. This condition has also been suggested by Shepherd et al. (1998) as a possible cause of the decline of another abalone fishery.

Future development of tetraploid H. rubra offers the prospect of using functionally sterile 100% triploid seed to enhance depleted reefs. This could in turn enable "put and take" ranching in NSW, capitalizing on large-scale, cost efficient, centralized production of seed. Home ranges of H. rubra and natural recruitment in relation to parent stock, have both been shown to be limited to scales of several hundred meters in H. rubra. Likewise, productivity of particular areas of reef can vary greatly over distances of hundreds or even tens of meters. Effective management protocols therefore need to be tailored to accommodate these fine spatial scales.

In addition to a put-and-take ranching of sterile triploid seed, there seems to be good scope for rebuilding depleted natural populations of H. rubra in NSW. However, for that strategy, seed will need to be produced in hatcheries from genetically matched parent stock in sufficient numbers to safeguard the integrity of natural gene pools, including preservation of rare or unique alleles. Rebuilding standing stocks of H. rubra to high levels at which self sustaining natural recruitment can be restored, will probably require integration of seeding with new and innovative fisheries management initiatives. Such initiatives will need to address apparent imbalances that have developed between H. rubra and several of its major competitors, especially the black urchin C. rodgersii and other large and common grazing gastropods, especially Turbo torquatus (Gmelin, 1791), Turbo militaris (Reeve, 1848) and Astralium tentoriiformis (Jonas, 1845). This in turn can only be achieved through the comanagement of these competing species (Andrews et al. 1998). In contrast to H. rubra, black urchins and the other common gastropods cited earlier have not to date been subjected to substantial levels of fishing pressure in NSW. It is also likely that efficient reseeding protocols will need to be aligned to the patchy distribution of legal size adults. In practice this will entail targeted reseeding of juvenile habitat that lies adjacent to high yielding patches of reef. Such "hot spots" for abalone and drift seaweed are well known to experienced commercial divers and are commonly characterized by fast growing abalone with elongated shells (Worthington & Andrew 1997).

ACKNOWLEDGMENTS

The author thanks Nick Savva, Rowan Chick, John Diemar, Duncan Worthington, Craig Brand and Peter Gibson for their individual and collective contributions in the implementation of the research undertaken; the TACC quota holders for their practical and financial support of the project, with special reference to John Smythe; Mr. Peter Dundas-Smith, Dr. Patrick Hone and Dr. Ann Fleming, for their unwavering support provided through the Abalone Sub-Program; Dr Greg Maguire, Dr Wayne O'Connor and Mr. Mark Booth for reviewing the manuscript and Mrs. Helena Heasman who assisted with manuscript preparation. Fisheries Research & Development Corporation funded this research.

LITERATURE CITED

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Andrew, N. L., D. G. Worthington, P. A. Brett, N. Bentley, R. Chick & C. Blount. 1998. Interactions between the abalone fishery and sea urchins in New South Wales. Final Report to FRDC. Sydney, NSW: NSW Fisheries. 63 pp.

Andrew, N. L. & A. J. Underwood. 1992. Associations and abundance of sea urchins and abalone on shallow subtidal reefs in Southern New South Wales. J. Mar. Freshwater Res. 43:1547-1559.

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Hamer, G. D. 1982. Abalone population dynamics and reef area estimation: fishing industry research trust account final report. Canberra, ACT: FRDC. 43 pp.

Heasman, M., R. Chick, N. Savva, D. Worthington, C. Brand, P. Gibson & J. Diemar. 2004. Enhancement of populations of abalone in NSW using hatchery-produced seed. Final report to FRDC Project No. 1998/219. NSW fisheries final report series No. 62. Sydney, NSW: NSW Fisheries. 269 pp.

Keesing, J., S. Clarke, S. Shepherd, R. Trengove & R. Werner. 1994. Application to FRDC for funding. (Unpublished).

Kojima, H. 1995. Evaluation of abalone stock enhancement through the release of hatchery-reared seeds. Mar. Freshwater Res. 46:689-695.

Liu, W. 2005. Induction and evaluation of triploidy in the blacklip abalone, Haliotis rubra (Leach 1814), for farming. PhD Thesis. University of New England (Submitted).

Liu, W., M. Heasman & R. Simpson. 2004. Evaluation of cytochalasin B (CB) treatments for triploidy induction in the blacklip abalone, Haliotis rubra (Leach, 1814). Aquaculture Res. 35:1062-1075.

Masuda, R. & K. Tsukamoto. 1998. Stock enhancement in Japan: review and perspective. Bull. Mar. Sci. 62:337-358.

McShane, P. E. 1991. Density-dependent mortality of recruits of the abalone Haliotis rubra (Mollusca: Gastropoda). Mar. Biol. 110:385-389.

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Preece, P. A., S. A. Shepherd, S. M. Clarke & J. K. Keesing. 1997. Abalone stock enhancement by larval seeding: effect of larval density on settlement and survival. Mollusc. Res. 18:265-273.

Prince, J. D., T. L. Sellers, W. B. Ford & S. R. Talbot. 1988. Confirmation of a relationship between the localized abundance of breeding stock and recruitment for Haliotis rubra Leach (Mollusca:Gastropoda). J. Mar. Exp. Biol. Ecol. 122:91-104.

Schiel, D. R. 1993. Experimental evaluation of commercial-scale enhancement of abalone Haliotis iris populations in New Zealand. Mar. Ecol. Prog. Ser. 97:167-181.

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Shepherd, S. A. 1998. Studies on Southern Australian abalone (genus Haliotis) XIX: long-term juvenile mortality dynamics. J. Shellfish Res. 17(3):813-825.

Shepherd, S. A. & P. A. Breen. 1992. Mortality in abalone: its estimation, variability and causes. In: S. A. Shepherd, M. J. Tegner & S. A. E. Guzman Del Proo, editors. Abalone of the world: biology, fisheries and culture: proceedings of the 1st international symposium on abalone. Fishing News Books. pp. 276-304.

Shepherd, S. A. & S. Daume. 1996. Ecology and survival of juvenile abalone in a crustose coralline habitat in South Australia. In: Y. Watanabe, Y. Yamashita & Y. Oozeki, editors. Proceedings of an international workshop-survival strategies in early life stages, October 11-14, 1994, Yokohama, Japan. Rotterdam, The Netherlands: A. A. Balkema. pp. 297-314.

Shepherd, S. A. & W. S. Hearn. 1983. Studies on Southern Australian abalone (Genus Haliotis). IV. Growth of H. laevigata and H. rubra. J. Mar. Freshwater Res. 34:461-475.

Shepherd, S. A., G. P. Kirkwood & R. L. Sandland. 1982. Studies on southern Australian abalone (genus Haliotis). III. Mortality of two exploited species. Aust. J. Mar. Freshwater Res. 34:461-475.

Shepherd, S. A., P. A. Preece & R. W. G. White. 2000. Tired nature's sweet restorer? Ecology of abalone (Haliotis spp.) stock enhancement in Australia. Can. Spec. Publ. Fish. Aqua. Sci. 130:84-97.

Shepherd, S. A. & J. A. Turner. 1985. Studies on southern Australian abalone (genus Haliotis) VI. Habitat preference, abundance and predators of juveniles. Exp. Mar. Biol. 93:285-298.

Shepherd, S. A., J. R. Turrubiates-Morales & K. Hall. 1998. Decline of the abalone fishery at La Natividad Mexico: overfishing or climate change? J. Shellfish Res. 17(3):839-846.

Worthington, D. G. 2002 Abalone Fishery Report. In: NSW Fisheries status of fisheries resources 2001/2002. Sydney, NSW: NSW fisheries. pp. 127-134.

Worthington, D. G. & C. Blount. 2003. Research to develop and manage sea urchin fisheries of NSW and Eastern Victoria. NSW fisheries final report series No. 56. 147 pp.

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M. P. HEASMAN *

NSW Department of Primary Industries, Port Stephens Fisheries Centre, Private Bag 1, Nelson Bay NSW 2315, Australia

* Corresponding author. E-mail: [e-mail]

Note: these budgets incorporate new highly efficient hatchery and nursery technologies developed in this study but do not include depreciation on plant and equipment.

Figure 2. Variation in growth of eight commercial scale batches of H.
rubra postlarvae grown on conventional diatom plates. Note: growth was
exponential in all cases (Heasman et al. 2004).

Batch.      Larval       Spawning         Growth season
            seeding        Date
            density

  A       5882/plate     23/07/98    law Winter early Spring
  B       5147/plate     27/08/98      early to mid Spring
  C       1838/plate     25/12/98            Summer
  D       7625/plate     20/01/99          late Summer
  E       1472/plate      6/09/99      early to mid Spring
  F        735/plate     14/09/99      mid to late Spring
  G       1323/pllate    24/11/99      early to mid Summer
  H       2507/plate      1/02/00          late Summer

Batch.    Period to min. mean     Mean growth     Best fit regression
          weaning size of 1500    rate microns
                microns               /day

  A             50 days             23 um/day      y = 314.71e0.0322x
  B             72 days             17 um/day       y = 373.24e0.02x
  C             45 days             26 um/day      y = 323.15e0.0335x
  D             32 days             36 um/day      y = 348.05e0.0464x
  E             52 days             22 um/day      y = 345.04e0.0319x
  F             47 days             24 um/day      y = 320.56e0.0442x
  G             41 days             28 um/day      y = 333.86e0.0362x
  H             35 days             33 um/day       y = 33731e0.0431x

Batch.    [R.sup.2]

  A         0.9813
  B         0.9751
  C         0.9808
  D         0.9731
  E         0.9921
  F         0.9999
  G         0.9988
  H         0.9923

TABLE 1.

Published age related mortality data for wild Haliotis rubra (See
Shepherd & Breen 1992, for the mathematical relationship between
instantaneous and proportional mortality).

                                                  M (Annualized
                                 Survival for     Instantaneous
                                    Period       Natural Rate of
     Mean Age (Age Span)         or Per Year        Mortality)

25 days (0-49 days)                  0.5%             311/y
80 days (1 week to 5 months)          3%         6.6-10.2 (8.4)/y
4 months (1 week to 8 months)        5.5%             1.4/y
1.25 years (6 months-2 years)        20%              0.7/y
2 years (1.5-2.5 years)          44% per year         0.81/y
2.25 years (2 to 2.5 years)      41% per year         0.9/y
2.5 years (2 to 3 years)         64% per year         0.45/y
3 years (2-4 years)              66% per year         0.42/y
3.3 years (3 to 3.5 years)       45% per year         0.8/y
3.5 years (2-5 years)            70% per year         0.36y
4 years (2-6 years)              81% per year         0.21/y
4.3 years (4 to 4.5 years)       74% per year         0.3/y
4.5 years (4 to 5 years)         76% per year         0.274/y
5+ years                         82% per year         0.20/y
5.3 years (5 to 5.5 years)       90% per year         0.1/y
6.3 years (6 to 6.5 years)       78% per year         0.25/y

     Mean Age (Age Span)                  Source

25 days (0-49 days)              Preece et al. 1997
80 days (1 week to 5 months)     McShane 1991
4 months (1 week to 8 months)    Prince et al. 1988
1.25 years (6 months-2 years)    Prince et al. 1988
2 years (1.5-2.5 years)          Day & Leorke 1986
2.25 years (2 to 2.5 years)      Prince et al. 1988
2.5 years (2 to 3 years)         Hamer 1982 (Botany Bay stock)
3 years (2-4 years)              Shepherd & Breen 1992
3.3 years (3 to 3.5 years)       Prince et al. 1988
3.5 years (2-5 years)            Shepherd et al. 1982
4 years (2-6 years)              Shepherd et al. 1982
4.3 years (4 to 4.5 years)       Prince et al. 1988
4.5 years (4 to 5 years)         Hamer 1982 (Eden Stock)
5+ years                         Beinssen & Powell 1979
5.3 years (5 to 5.5 years)       Prince et al. 1988
6.3 years (6 to 6.5 years)       Prince et al. 1988

TABLE 2.

Estimated age related survival, yield per recruit and associated
parameters for wild H. rubra.

                                     Assumed Rate
                                   of Instantaneous    Proportion
      Period/life Stage,               Natural         Surviving
 Age (post sell and Size (mm)       Mortality (M)        Period

Spawning to competent larvae              ?                ?
Competent larvae to 8 days post
  set (0.3-0.4 m)                     0.44/day            0.03
8-19 days post set (0.4-0.6 mm)       0.042/day           0.63
0.5-1.5 months (0.6-2.0 mm)           0.9/month           0.4
1.5-2.5 months (2-4 mm)               0.7/month           0.5
2.5-3.5 months (4-0 mm)               0.6/month           0.55
3.5-4.5 months (6-8 mm)               0.5/month           0.61
5.5-0.5 months (8-10 mm)              0.4/month           0.67
0.5-1.5 years (10-35 mm)              0.91/year           0.403
1.5-2.5 years (35-60 mm)              0.81/year           0.445
2.5-3.5 years (60-85 mm)              0.42/year           0.67
3.5-4.5 years (85 105 mm)             0.3/year            0.74
4.5-5.5 years (105-115 mm)            0.25/year           0.78
5.5-6.5 years (115-120 mm)            0.20/year           0.82

                                                       Number of
                                                         Larvae
                                      Cumulative        Required
                                      Proportion       to Yield 1
      Period/life Stage,              Surviving        Abalone to
 Age (post sell and Size (mm)        from Larvae        This Age

Spawning to competent larvae
Competent larvae to 8 days post
  set (0.3-0.4 m)                     0.0300                33
8-19 days post set (0.4-0.6 mm)       0.0189                53
0.5-1.5 months (0.6-2.0 mm)           0.00756              132
1.5-2.5 months (2-4 mm)               0.00378              265
2.5-3.5 months (4-0 mm)               0.00208              481
3.5-4.5 months (6-8 mm)               0.00127              789
5.5-0.5 months (8-10 mm)              0.00085             1177
0.5-1.5 years (10-35 mm)              0.000342            2920
1.5-2.5 years (35-60 mm)              0.000152            6563
2.5-3.5 years (60-85 mm)              0.000102            9795
3.5-4.5 years (85-105 mm)             0.0000755          13236
4.5-5.5 years (105-115 mm)            0.0000589          16970
5.5-6.5 years (115-120 mm)            0.0000483          20695

                                                      Number of
                                     Proportion      Seed of This
                                     from This      Age Needed to
      Period/life Stage,           Age Living to    Yield 1 Legal
 Age (post sell and Size (mm)        Legal Size      Size Abalone

Spawning to competent larvae
Competent larvae to 8 days post
  set (0.3-0.4 m)                      0.0000           20704
8-19 days post set (0.4-0.6 mm)        0.0016             621
0.5-1.5 months (0.6-2.0 mm)            0.0026             391
1.5-2.5 months (2-4 mm)                0.0064             157
2.5-3.5 months (4-0 mm)                0.0128              78
3.5-4.5 months (6-8 mm)                0.0232              43
5.5-0.5 months (8-10 mm)               0.0381              26
0.5-1.5 years (10-35 mm)               0.0568              18
1.5-2.5 years (35-60 mm)               0.1411               7.1
2.5-3.5 years (60-85 mm)               0.3170               3.2
3.5-4.5 years (85-105 mm)              0.4731               2.1
4.5-5.5 years (105-115 mm)             0.6393               1.6
5.5-6.5 years (115-120 mm)             0.8196               1.2

                                      Number per
                                     Million Seed
                                     Deployed at
                                    This Age That
      Period/life Stage,              Will Reach    Source of Survival
 Age (post sell and Size (mm)        Harvest Size           Data

Spawning to competent larvae
Competent larvae to 8 days post
  set (0.3-0.4 m)                           48      Preece et al. 1997
8-19 days post set (0.4-0.6 mm)           1610      Preece et al. 1997
0.5-1.5 months (0.6-2.0 mm)               2556      McShane 1991
1.5-2.5 months (2-4 mm)                   6389      McShane 1991
2.5-3.5 months (4-0 mm)                  12778      McShane 1991
3.5-4.5 months (6-8 mm)                  23232      McShane 1991
5.5-0.5 months (8-10 mm)                 38086      McShane 1991
0.5-1.5 years (10-35 mm)                 56844      Day & Leorke 1986
1.5-2.5 years (35-60 mm)                141053      Day & Leorke 1986
2.5-3.5 years (60-85 mm)                316973      Shepherd 1992,
                                                      based on Shepherd
                                                      & Hearn 1983
3.5-4.5 years (85-105 mm)               473095      Derived from data
                                                      in Fig. 7
4.5-5.5 years (105-115 mm)              639317      Derived from data
                                                      in Fig. 7
5.5-6.5 years (115-120 mm)              819638      Derived from data
                                                      in Fig. 7

TABLE 3.

Bioeconomics model summarizing requirements and associated benefits and
costs of producing and deploying five age/size classes of H. rubra
aimed at increasing the sustainable commercial catch in NSW by 300
tonnes (1 million x 120 mm abalone).

                                                   Estimated Number of
                                                         Hatchery
                                                    Broodstock of this
                                                    Age/Size Needed to
                                                     Yield 1 Million
                                                      Legal Abalone
                          Assumed d Number of       Valued at ~AU$15 M
                         Seed Needed to Yield 1       (Assumes Same
                          Harvestable Abalone         Survival Rates
                          Averaging 120 mm and      as Equivalent Wild
 Age & size of seed       300 g (from Table 2)            Stock)

Competent larvae                 20,000                 20 Billion
1 wk old postlarvae               2,000             [less than or equal
  (0.4 mm)                                            to] 2 Billion
2 months ex plate                   157                157 Million
  (2 mm/0.002 g)
6 month old juveniles                26                 26 Million
  (8 mm/0.1 g)
21 months old                        15                 15 Million
  juveniles (40
  mm/10 g)

                             Estimated Number of
                            Brood-Stock Spawnings
                          Needed to Yield 1 Million
                            Legal Abalone Valued
 Age & size of seed              at -$15 M

Competent larvae         33,000
                           Assumed fecundity of 1.5 M
                           eggs/spawner and 40% yield
                           of competent larvae from
                           eggs = 0.6 M/spawner
1 wk old postlarvae      [less than or equal to] 3300
  (0.4 mm)                 Assumed 50% mean yield of
                           PL's from larvae = 0.3
                           M/spawner
2 months ex plate        3200
  (2 mm/0.002 g)           Assumed 20% yield to this
                           age from 1 week post set =
                           0.06 M/spawner
6 month old juveniles    2600
  (8 mm/0.1 g)             Assumed 10% yield to this
                           age from 1 week post set =
                           0.03 M/spawner
21 months old            2900
  juveniles (40            Assumed 9% yield to this age
  mm/10 g)                 from 1 week post set =
                           0.027 M/spawner

                          Estimated Annual Operating
                           Costs Using Conventional
                           Hatchery Production and
                           Seeding Techniques Plus
 Age & size of seed            General Comments

Competent larvae         Logistical problems, of huge
                           numbers of broodstock needed
                           and deployment of larvae,
                           appear insurmountable
1 wk old postlarvae      Conventional hatchery and
  (0.4 mm)                 nursery technology is
                           inappropriate
2 months ex plate        Prohibitively costly ($6.28 M)
  (2 mm/0.002 g)           based on current commercial
                           prices of 2 cents per mm = 4
                           cents per spat
6 month old juveniles    Prohibitively costly ($4.16 M)
  (8 mm/0.1 g)             based on 2 cents per mm = 16
                           cents per spat
21 months old            Prohibitive: facility would need to
  juveniles (40            be twice as big as Australia's
  mm/10 g)                 largest farm i.e. biomass of
                           seed = 150 tonnes/year

                           Estimated Annual Operating
                             Costs Using Production
                             and Seeding Techniques
                             Developed in This Study
                            NB Estimated Capital Cost
 Age & size of seed         of Hatchery = $1 Million

Competent larvae         Logistical problems associated
                           with huge numbers of
                           broodstock and deployment of
                           larvae appear insurmountable
1 wk old postlarvae      Promising option but technology
  (0.4 mm)                 of handling and deployment
                           lacking
2 months ex plate        $0.5 M (see Table 4) Promising
  (2 mm/0.002 g)           option but technology of
                           handling and deployment
                           lacking
6 month old juveniles    $0.665 M (see Table 4)
  (8 mm/0.1 g)
21 months old            Prohibitive facility would need
  juveniles (40            to be twice as big as
  mm/10 g)                 Australia's largest existing
                           farm i.e. biomass of seed =
                           150 tonnes/year

TABLE 4.

Estimated annual operating budgets for hatchery production and
seeding of 157 million 2 mm H. rubra postlarvae and 26 million
8 mm juveniles. Note: these budgets incorporate new highly efficient
hatchery and nursery technologies developed in this study but do
not include depreciation on plant and equipment.

                                              2 mm         8 mm
               Salaries                    Postlarvae    Juveniles
       (Including 30% On-Costs)                $             $

Seed Production
  Full time manager                         100,000       100,000
  Full time senior fisheries technician      80,000        80,000
  Full time fisheries technician(s)          60,000       120,000
Seed deployment and monitoring
  Casual assistants                          30,000        60,000
    Sub Total                               270,000       360,000
Travel & Accommodation
  20 trips for 3 days by 3 staff
    @$120/d/person                           21,600        21,600
Operating costs
  Power                                      60,000        80,000
  Repairs & Maintenance                      30,000        40,000
  Vehicle operating                          12,000        12,000
  Post freight & packaging                    5,000         5,000
  Air fills                                   3,000         3,000
  Telephone/email/www                         3,000         3,000
  Boat operating                             10,000        10,000
  Consumables                                10,000        10,000
  Chemicals/pharmaceuticals                   3,000         3,000
  Insurances                                  1,000         1,000
  Food                                        1,000        10,000
  Permits                                     1,000         1,000
    Sub Total                               139,000       178,000
Interest on $1 m or $1.5 m for
  capital works loans at 7% pa               70,000       105,000
Total                                       500,600       664,600