The roles of bacteria and micro and macro algae in abalone aquaculture: a review.

ABSTRACT Abalone aquaculture is dependent on cultured algae to induce larval settlement and as a food source for the early life stages of abalone until formulated feed or macroalgae such as Macrocystis sp., Porphyra sp. and Ulva sp. are introduced into the growout system. In the natural environment, abalone larvae settle on coralline red algae, which provide one of the strongest and most consistent settlement cues available for abalone larvae. However, propagation of coralline red algae is not practical commercially. Abalone farms in Japan successfully settle abalone larvae (Haliotis discus hannai) on the green alga Ulvella lens. U. lens also proved to be suitable to enhance settlement of cultured southern Australian abalone species (Haliotis laevigata, H. rubra). Most abalone farms in Australia are now growing U. lens for that purpose. U. lens is easy to culture, no specific facilities are needed and the alga can be grown on PVC settlement plates in commercial nursery tanks. However, U. lens has limited value as a feed for young postlarvae. Instead, cultured diatoms can be added after larvae successfully settle and start feeding. Juvenile abalone (>3 mm in shell length) can consume U. lens and grow rapidly on this alga. Diatom cultures and biofilms developing on settlement plates are not axenic and the role of bacteria in early postlarvae feeding is poorly understood. It has been suggested that bacteria may perform metabolic activities in the undeveloped gut of young postlarvae. At later stages of the nursery phase it becomes increasingly difficult to maintain adequate feed on the plates and this is still regarded as a significant bottleneck for the abalone aquaculture industry. Recent investigations have indicated that sporelings of macroalgae like Ulva sp. or diatoms that can provide more biomass may provide a suitable additional food source for juveniles (>3 mm in shell length).

KEY WORDS: abalone, abalone eggs, antibiotics, algae, bacteria, diatoms, growth, larval quality, lipids, settlement, Ulva sp., Ulvella lens

INTRODUCTION

Abalone fisheries (Haliotis spp.) produce high value, export-orientated products with about 50% of the world supply being provided by Australian fisheries in 1999 (Gordon & Cook 2001). The worldwide catch from abalone fisheries has declined by about 30% over a 10-year period from ca. 14,000 mt in 1989 to 10,000 mt in 1999, and consequently the interest in aquaculture products has increased substantially. The world production of abalone from aquaculture in 1999 was approximately 7,775 tonnes (Gordon & Cook 2001). Future production from the numerous farms and sites established, under construction or approved in several countries including Australia, could be even more substantial if the technology is improved.

In an aquaculture environment, abalone larvae are produced by spawning recently collected wild broodstock, or wild or farmed abalone broodstock that have been held in conditioning systems for extended periods. The nonfeeding larvae have a short larval phase (e.g., 7 days at 17[degrees]C for Haliotis rubra Leach and Haliotis laevigata Donovan). When larvae are ready for settlement they actively seek a suitable surface. In the natural environment, abalone larvae settle on coralline red algae (Shepherd & Daume 1996); however on farms the surface is typically vertical, spaced plastic plates that have been colonized by a variety of different algal species. Abalone aquaculture in most countries is dependent on cultured algae at least for the early life stages, to induce larval settlement and as a food source for postlarvae and juveniles, until formulated food is introduced into the growout system. As provision of algal supplies decline, the juveniles may be weaned onto formulated foods. They can be transferred to various land-based tanks or sea-based systems (Freeman 2001). In several countries around the world (e.g., South Africa) even the growout depends solely on algae; macroalgae that are harvested from the ocean are fed to the abalone in specialist growout systems. A large component of the cost of producing juveniles is the provisioning of live food in a manner suitable for a grazing herbivore. This review examines the roles of bacteria, micro and macroalgae during the nursery phase of abalone aquaculture and emphasizes research conducted by the author with postlarval and juvenile H. laevigata and H. rubra in Australia. It complements earlier reviews by Roberts (2001) on larval settlement and by Kawamura et al. (1998c) on postlarval growth and survival by highlighting the applicability of bacteria and algae for commercial abalone hatcheries and nurseries. Their roles are considered in the context of the main areas of research undertaken to improve juvenile production efficiency: (1) presettlement larvae quality; (2) larval settlement; (3) dietary requirements for postlarvae and juveniles.

Pre-settlement Larvae Quality

Previously wild abalone broodstock that feed on a range of macroalgae have been the main source of gametes for commercial abalone hatcheries. Selection of broodstock is mainly based on gonad size and appearance (Litaay & De Silva 2001), with abalone judged to be ready for induced spawning and have mature eggs based on the amount of swelling of the gonad. However, animal selection based on these criteria shows variable results in spawning success and produce offspring with large variability in larval and postlarval survival. More recently there has been greater commercial and research interest in conditioning captive and farmed broodstock using macroalgae or formulated foods (Grubert & Ritar 2003, Daume & Ryan 2004a, Freeman et al. this volume).

Lipids and protein in abalone eggs are known to fuel the development and metamorphosis of the larvae (Jaeckle & Manahan 1989a, 1989b, Litaay et al. 2001). Nelson et al. (2002) demonstrated that variations in lipid content and fatty acid profile of the digestive gland coincided with variation in their macroalgal diets and are related to seasonal temperature fluctuations. Biochemical variation in the diet may affect the composition of the eggs and ultimately larval performance. However studies of changes in biochemical composition such as fatty acids in abalone eggs are scarce. Litaay et al. (2001) demonstrated changes in biochemical composition during larval development. Recently, Daume and Ryan (2004a) showed high variability in proximate biochemical composition and fatty acid profiles of abalone eggs between batches derived from conditioned and wild broodstock as well as between two consecutive spawning seasons. The relative proportions of some PUFAs in the broodstock diets were reflected in the eggs and varied between batches of conditioned and wild broodstock, indicating that formulated diets designed to maximize growth rates are not necessarily adequate to maintain viable, high quality eggs and larvae from captive broodstock.

Other factors that can influence the quality and success of larval culture are opportunistic pathogenic bacteria that can bloom and cause deformities in and collapse of whole larval batches under potentially stressful commercial growing conditions. Many abalone hatcheries are using antibiotics like oxytetracycline prophylactically. Similarly they may be used in research projects. Roberts (2001) suggested using antibiotics to eliminate bacterial interference in settlement assay systems. Apart from the general problem of development of antibiotic resistant strains of bacteria in hatcheries, problems have been reported with certain antibiotics when used with abalone during larval rearing or settlement assays. Streptomycin at low doses of 5 [micro]g [mL.sup.-1] was toxic to Haliotis diversicolor (Bryan & Qian 1998). Emitine caused abnormal loss of velum that could have been confused with metamorphosis (Fenteany & Morse 1993).

An experiment conducted to assess the effect of two antibiotics (Ampicillin and Kanamycin at 50 [micro]g [mL.sup.-1]) on the settlement of H. rubra revealed no difference in settlement rate between treated and untreated settlement substrate (Table 1). In this experiment 3 algal settlement substrata were tested (Navicula cf. jeffreyi, Ulvella lens, Sporolithon durum) and compared with a negative control (plastic square of commercial settlement plate without any algal growth) all with and without antibiotics. The ratios of settlement rates between treated and untreated substrates did not change over time. In addition, the difference in settlement preferences between specific substrates remained the same regardless if antibiotics were used or not. The antibiotics were initially effective as indicated by the higher survival of swimming larvae (in water column) in control jars treated with antibiotics. However, the settlement rate was not higher in the antibiotic treatment, indicating that unfit larvae might survive if treated with antibiotics but they do not settle successfully. This result questions the need and usefulness of antibiotics in abalone hatcheries. Further studies are needed to assess the effects of other antibiotics and earlier treatment with antibiotics (e.g., during larval rearing). However, alternatives like probiotics should be investigated to enhance larval survival safely.

Many antibiotics, including Kanamycin and oxytetracycline, work by inhibiting or interfering with the protein biosynthesis by targeting the bacterial ribosomes. The close similarity between bacterial and mitochondrial ribosomes makes the latter (present in all cells of the "treated" organisms) a potential target (Hart 2004). Inhibition of mitochondrial protein synthesis or injuries in mitochondria of the treated organism have occurred and can lead to various dysfunction: any cell type or tissue with a high aerobic energy requirement is more likely to be affected when this organelle is injured (Hart 2004). The effects of antibiotics on abalone larval settlement and postlarval performance however are not well understood. The knowledge we have from other systems, however, warrants extreme caution and highlights the danger of introducing other, potentially detrimental factors. These may not be obvious initially but may manifest themselves at later stages of larval or postlarval development.

Larval Settlement

The term "settlement" in this review describes the permanent attachment of abalone larvae to the substrate after shedding of the velum to complete metamorphosis. In the natural environment, abalone larvae, like many other invertebrate larvae, settle on coralline red algae. Daume et al. (1999a) revealed that settlement of Haliotis laevigata larvae in response to three nongeniculate coralline red algae is species-specific. In that study the frequency of occurrence of epiphytic bacteria and diatoms was assessed on all coralline red algal species tested. However, no significant correlation was found indicating that the settlement induction is algal in origin. The authors concluded that bacteria and diatoms may influence the settlement response of abalone larvae but they are not the main driving force. Roberts (2001) referred to some of his unpublished work and stated that bacteria can induce abalone larval settlement but that the response is slow, taking 1 week to reach 50% metamorphosis. In contrast, very rapid settlement was reported in small-scale laboratory experiments through the use of the coralline red alga, Sporolithon durum, with the maximum rate being reached after 24 h (Daume et al. 1999a) indicating that nongeniculate coralline red algae are strong settlement inducers. This result coincides with disproportional high numbers of recruits found on S. durum in the natural environment (Shepherd & Daume 1996).

Historically, benthic biofilms, consisting of bacteria and mixed diatom species growing on PVC settlement plates, have been used in abalone hatcheries worldwide to induce larval settlement. Diatoms, brought in by the incoming seawater, colonize clear plastic sheets arranged in commercial nursery tanks. This process is unpredictable and larval settlement rates can be low (1% to 10% of larvae) (Daume 2003). In both experimental and commercial systems, to achieve more control and consistency, films dominated by single algal species can be generated (Daume et al. 2000, Daume & Ryan 2004b). H. rubra did not respond to films of any diatom species tested, but settled on the nongeniculate coralline red alga Phymatolithon repandum (Daume et al. 1999b). In contrast, H. laevigata settled comparably well on the diatom Navicula ramosissima and on the coralline S. durum. Roberts (2001) reviewed data on settlement cues including diatoms and other biofilms. Overall it is apparent that coralline red algae provide more consistent and reliable settlement cues, whereas settlement on diatoms can be highly variable. However, propagation of coralline red algae is not practical at a commercial scale.

Abalone hatcheries in Japan successfully settle abalone larvae (Haliotis discus hannai) on the green alga Ulvella lens (Takahashi & Koganezawa 1988). U. lens is also suitable for enhancing settlement of both cultured southern Australian abalone species (H. rubra and H. laevigata) (Fig. 1). Most abalone farms in Australia are now growing U. lens for that purpose (Daume et al. 2000, Daume et al. 2004, Daume & Ryan 2004b). The earlier study established settlement preferences of H. rubra for U. lens at laboratory scale whereas the later studies focused on commercial scale experiments. Both species (14. rubra, H. laevigata) showed a clear preference for older rather than for younger U. lens (Table 2, Table 3) even with similar percentage cover, indicating that the developmental stage of the alga and not percentage cover per se is important in settlement induction (Table 3). Settlement was also significantly higher in the combined U. lens treatments (old and young) compared with 2 diatom treatments (Navicula cf. jeffreyi and Cocconeis sp. demonstrating the suitability of U. lens to improve the settlement of Haliotis laevigata larvae on commercial scale (Table 3). No significant difference between high and low larval release densities was found with H. rubra in the nursery (Table 2) confirming earlier findings at laboratory scale with /4. laevigata larvae that settlement of abalone larvae is not gregarious when tested with larvae of the same batch (Daume et al. 1999a). In contrast, settlement was found to be gregarious in response to conspecific postlarvae as young as 7 days (Daume et al. 1999a) and older conspecific juveniles and adults and their grazing mucus is believed to be responsible (Seki & Kan-no 1981, Slattery 1992).

[FIGURE 1 OMITTED]

Recently alternative systems, to replace live algae as a means of settlement and growing postlarvae, have been proposed in Japan for H. discus discus and H. diversicolor (Stott et al. 2002, 2003, 2004a, 2004b). In the earlier studies, an alginate gel solution containing micro particulate diets was pasted onto settlement plates. In more recent studies settlement plates are sprayed with a solution of agar and one of the following: dried algal powder (Spirulina platensis, Chlorella vulgaris, Undaria pinnafifida), dried natural diatom powder, formulated diet and two different concentrations of "[gamma]-aminobutyric acid (GABA), each with and without antibiotics, and compared with negative (clean plates) and positive (living natural diatom biofilms). In both recent studies there was no significant difference in settlement rates between the microalgae powder treatments and the living natural biofim but both supported significantly higher rates when compared with the negative control and GABA treatments (Stott et al. 2004a, 2004b). The authors demonstrated that pregrazing of plates by conspecific juveniles covered with microalgal powder/ agar solution enhanced larval settlement significantly (85% vs. 30% on grazed and ungrazed plates respectively). This system shows some potential, however mechanized and cost-efficient ways of spraying the plates need to be developed before it becomes viable commercially.

Dietary Requirements

Post-larval abalone feed on benthic diatoms (Kawamura et al. 1995) and the diatom film on plates also provides the food for growing postlarvae in commercial abalone nurseries. Commercial farms traditionally rely on mixed species of diatoms as a food source throughout the nursery period (settled larvae to 8-10 mm). The film is maintained through passive seeding (new cells are brought in with the incoming seawater), adding nutrients and manipulating the light intensity through shading. Without much control over composition and density of the biofilm species, the results are very inconsistent and often very poor. Isolating particular diatom species and growing them in monoculture before inoculating settlement tanks in the nursery affords greater control. This however has not been embraced by the industry and further investigations are needed to assess the effectiveness in larger scale systems. However, a significant bottleneck experienced by industry is the inability to maintain adequate food (both quantity and quality) on the plates particularly at later stages of the nursery phase. Growth rates of juveniles are influenced by the availability, digestibility and nutritional composition of the algae (Kawamura et al. 1998b, Roberts et al. 1999, Daume et al. 2003).

The Role of Bacteria in Postiarval Nutrition

Diatom cultures and biofilms developing on settlement plates are not axenic and the role of bacteria in early postlarvae feeding and growth is poorly understood. Newly settled postlarvae ingest diatoms but are often not able to digest the cell contents. This suggests that bacteria and the extracellular material produced by the diatoms, present in the biofilm, are a significant source of nutrition for postlarval abalone (Fig. 1). Garland et al. (1985) reported that postlarval H. rubra ingested bacteria growing on the surface of coralline red algae. It has been suggested that bacteria may perform metabolic activities in the undeveloped gut of young postlarvae and are able to enhance the digestion efficiency of the host by supplying polysaccharolytic enzymes (Garland et al. 1985, Erasmus et al. 1997). Polysaccharolytic enzyme activity has been reported in day 17 H. discus hannai postlarvae (Takami et al. 1998). Sawabe et al. (2003) detected the bacteria Vibrio halioticoli in the gut of H. diversicolor aquatilis and suggested that this bacterium may play a crucial role in converting alginate to acetic acid. As part of the alternative systems proposed by Stott et al. (2002, 2003, 2004a, 2004b), the authors observed that the growth of postlarvae H. diversicolor aquatilis fed a formulated diet was reduced when antibiotics were added and suggested that bacteria that assisted in digestion became limiting. In a later study they discovered that 5-10 times more bacteria (including Vibrio spp.) were present on plates sprayed with the agar/formulated diet solution. These bacteria could have provided a substantial food source to early postlarvae, which may have contributed to the significantly better growth rates on these plates 1 week after settlement (Stott et al. 2004b). The authors suggest that for recently settled postlarvae, bacteria might be a superior food source compared with diatom and abalone grazing mucus. All these studies indicate that bacteria are ingested and play an important role in early postlarvae nutrition and health, but further studies are needed to elucidate their role and contribution.

Food Preferences for Postlarval Abalone

Worldwide, several studies have examined postlarval feeding and growth on different algal species (Ohgai et al. 1991, Ishida et al. 1995, Kawamura et al. 1998a, Roberts et al. 1999). Studies devoted to examining their feeding preferences and growth (Kawamura & Kikuchi 1992, Kawamura & Takami 1995, Kawamura et al. 1995, Matthews & Cook 1995, Kawamura 1996, Takami et al. 1997, Daume et al. 2000, Takami & Kawamura 2003) have shown that food requirements change as abalone grow (Fig. 1). Two to three weeks after settlement, postlarvae become responsive to the "digestibility" of the diatom strains and grow more rapidly on effectively digested strains (Kawamura et al. 1998a, 1998b). Post-larvae 0.8-2 mm in shell length grow ca 40-60 [micro]m [day.sup.-1] on "digestible" diatoms and only ca 15-30 [micro]m [day.sup.-1] on "indigestible" diatoms (Kawamura et al. 1998b). In addition, the diatom cell size, attachment strength, frustule's strength and postlarval size can influence digestion. In a feeding trial covering the whole post-larval period, Roberts et al. (1999) showed that different diatom food species affected survival and growth. After day 17, postlarvae grew faster on Cocconeis scutellum and Cylindrotheca closterium. Both species were most efficiently digested. Transitions in postlarval feeding preferences and growth performances on different algal species are reviewed in Kawamura et al. (1998c).

Alternative Food Sources for all Stages of Nursery Culture

The green alga U. lens has limited value as a food for growing postlarvae. Instead, cultured diatoms can be added after larvae successfully settle and start feeding. Seki (1997) reported that growth rates of postlarvae on U. lens were improved by the inoculation of cultured diatoms.

Recent studies showed that plates with a low cover of young germlings of U. lens could be used for settlement induction of Australian abalone species (H. rubra, H. laevigata) and followed with inoculation of the cultured diatom Navicula cf. jeffreyi to ensure sufficient food for the growing postlarvae (Daume et al. 2000, 2004, Daume & Ryan 2004b). The former study provided crucial information on early development of H. rubra and established that growth rates on several diatom species are significantly higher than on U. lens at laboratory scale (Fig. 2). In the more recent study, at commercial scale, the type of substrate on which larvae settled, light (which affected the food density) and the density of postlarvae all had very marked effects on growth (Daume et al. 2004). The results also suggest that early growth is important in determining later performance. Daume and Ryan (2004b) investigated settlement, growth, survival and size variability of the abalone H. laevigata on commercial scale. Both growth rate and size variability increased over time until juveniles reached approximately 5 mm in shell length. Whereas postlarval abalone do not grow well on U. lens (Fig. 2), juvenile abalone (>3 mm in shell length) can consume U. lens and grow rapidly (80-110 [micro]m [day.sup.-1]) on this alga (Table 4).

[FIGURE 2 OMITTED]

At later stages of the nursery phase (>5 mm in shell length), it becomes increasingly difficult to maintain adequate food on the plates and this is still regarded as a significant bottleneck for the industry. Recent investigations have indicated that sporelings of macroalgae like Ulva sp. may provide a suitable food source for juveniles (see Strain et al. this volume) (Fig. 1). Alternatively, chain forming diatoms, like Delphineis, offer a 3-D structure compared with the 2-D structure of nonchain forming prostrate attaching species, like Navicula spp. and thus providing more biomass for the growing juveniles (Fig. 1). Kawamura et al. (1995) reported growth rates of 48 [micro]m [day.sup.-1] of H. discus hannai juveniles 1-2 mm in shell length, when feeding on the diatom Achnanthes longipes, which has a 3-D structure. More recently, Takami and Kawamura. (2003) found that juveniles 2.8-2.9 mm in shell length grew 100 [micro]m [day.sup.-1] on this diatom species, which was comparable to growth rates achieved on juvenile sporophytes of the macroalga Laminaria japonica.

Biochemical Composition and Nutritional Value of Algal Diets

The biochemical composition of microalgae, and therefore their nutritional value to herbivores varies between species (Brown et al. 1996) and is greatly affected by harvest stage, light intensity (Thompson et al. 1993, Brown et al. 1996), nutrient concentrations (Fabregas et al. 1996, Fabregas et al. 1998) and culture methods (Otero & Fabregas 1997). It is known that the biochemical composition of algae can be altered by changing the growing conditions (e.g., Otero & Fabregas 1997, Thompson et al. 1993, Brown et al. 1996). When microalgal cultures are grown in nitrogen-limited media, the protein content of the cells decreases (Enright et al. 1986, D'Souza & Kelly 2000, Daume et al. 2003). Daume et al. (2003) showed previously that juvenile H. rubra grew faster when feeding on the diatom Navicula cf. jeffreyi that was cultured in a higher nitrate medium. Searcy-Bernal et al. (2003) found that recently settled H. fulgens postlarvae grew and survived better under low light (6 [micro]E) conditions, whereas a lower number of cells of the diatom Navicula incerta were available in the lower light treatment. The authors suggested that oxygen supersaturation in the boundary layer, particularly in high-density diatom films at high light levels (75 [micro]E), could have caused high mortality in this treatment. In another study, the influence of light intensity on two diatom species (Navicula cf. jeffreyi, Cocconeis sp.) as a food for juvenile 14. laevigata (3-4 mm in shell length) was tested (Watson et al. 2004). In contrast to N. cf. jeffreyi, growth of Cocconeis sp. was not inhibited at lower light levels making it a good candidate for culture in shaded nursery systems. Light was more influential in juvenile grazing behavior (photophobic) than food availability. Watson et al. (2005) examined the combined effect of manipulations in light intensity and nitrate concentrations on the nutritional value of the diatom Navicula cf. jeffreyi when fed to juvenile abalone (H. laevigata). Under high light conditions Navicula cf. jeffreyi was lower in protein and higher in carbohydrates and fat. Juveniles grazed larger numbers of diatom cells when the protein content was low, possibly compensating for the lower protein levels. The authors reported elevated pH levels in higher light treatments and suggested that this could have caused high mortality. These studies indicate that changes in light intensity and nitrate concentration, under which the diatom species are cultured, can have a dramatic effect on growth, grazing rates and particularly survival of postlarval and juvenile abalone. This emphasizes the need for selecting the right light and nutrient level to achieve high value food and conditions for optimal growth and survival of juvenile abalone in commercial nurseries.

This study reviewed three main areas of abalone research associated with abalone hatchery and nursery production. Further studies are needed to find alternatives, such as probiotics, to the use of antibiotics in abalone hatcheries. Alternative cost effective foods, for broodstock and for the latter stage of the nursery still need to be found that will increase larval quality and allow abalone farmers to keep animals on the plates longer and thus reduce weaning mortality.

ACKNOWLEDGMENTS

The author thanks Stephen Ryan, Sylvain Huchette, Ben Long, Peter Crouch, Anton Krisnich, Sascha Brand-Gardner, Rob Day and Bill Woelkerling who were involved in various parts of the work on H. laevigata and H. rubra, and Greg Maguire for many useful comments.

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SABINE DAUME

Research Division, Department of Fisheries Western Australia, PO Box 20, North Beach, WA 6920, Australia

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

TABLE 1.

Percentage settlement of Haliotis rubra on different settlement
substrates (Ulvella lens and Navicula cf. jeffreyi and a negative
control), with and without antibiotics, as well as Sporolithon durum
(positive control) after 24, 48 hours, % settled and survived up to 1
week and % of larvae in water column after 1 week (n = 6 [+ or -] SE).
Data are from Daume (2003).

                                            % Settlement
       Species           Antibiotics          24 Hours

Ulvella lens                  -          30 [+ or -] [8.1.sup.a]
Ulvella lens                  +          22 [+ or -] [4.4.sup.a]
Navicula cf. jeffreyi         -           5 [+ or -] [1.4.sup.b]
Navicula cf. jeffreyi         +         0.3 [+ or -] [0.3.sup.b]
Control                       -           0 [+ or -] [0.sup.b]
Control                       +           0 [+ or -] [0.sup.b]
Sporolithon durum             -          39 [+ or -] 3.7

                               % Settlement            % Survival Up
       Species                   48 Hours                to 1 Week

Ulvella lens              35 [+ or -] [7.6.sup.a]     12 [+ or -] 1.5
Ulvella lens              36 [+ or -] [5.3.sup.a]     17 [+ or -] 1.1
Navicula cf. jeffreyi      3 [+ or -] [2.0.sup.b]      4 [+ or -] 1.2
Navicula cf. jeffreyi      1 [+ or -] [0.3.sup.b]      2 [+ or -] 0.3
Control                    1 [+ or -] [0.6.sup.b]    0.5 [+ or -] 0.3
Control                  0.3 [+ or -] [0.3.sup.b]    0.6 [+ or -] 0.3
Sporolithon durum         50 [+ or -] 4.6             16 [+ or -] 2.6

                         % in Water Column
       Species             After 1 Week

Ulvella lens               0 [+ or -] 0
Ulvella lens               5 [+ or -] 1.6
Navicula cf. jeffreyi      8 [+ or -] 3.5
Navicula cf. jeffreyi     30 [+ or -] 4.2
Control                    3 [+ or -] 1.1
Control                   54 [+ or -] 6.7
Sporolithon durum          0 [+ or -] 0

* Means with different superscript letters are significantly different
(P < 0.05).

TABLE 2.

Percentage settlement ([+ or -] SE) of Haliotis rubra in the nursery
3 days after larval release (n = 32). Data from Daume et al. (2004).

Larval                                     Per U. lens
Density          Ulvella lens               Treatment

High       Old (18 days 31% cover).     31.9 [+ or -] 7.5
           Young (4 days 57% cover).    21.7 [+ or -] 6.8
Low        Old (18 days 31 % cover).    44.0 [+ or -] 7.3
           Young (4 days 57% cover).    26.4 [+ or -] 7.6
Average

Larval           Total
Density         per Tank

High       53.6 [+ or -] 5.8
Low        70.4 [+ or -] 8.7
Average           62.0

TABLE 3.

Percentage settlement ([+ or -] SE) of Haliotis laevigata 3 days after
larval release (n = 3) when given a choice between 4 substrates. Data
from Daume and Ryan (2004b).

                    Old U. lens           Young U. lens
 Treatments     (8 weeks-97% cover)    (6 weeks-82% cover)

% Settlement      61 [+ or -] 14          14 [+ or -] 1

                                                     Total
 Treatments      Navicula sp.      Cocconeis sp.    per Tank

% Settlement    7 [+ or -] 0.3    5 [+ or -] 0.5       87

TABLE 4.

Daily growth-rates ([micro]m [day.sup.-1]) of juveniles (Haliotis
rubra) on plates 52 days after settlement and shell length (mm) 114
days after settlement (mean [+ or -] SE). Data from Daume et al.
(2004).

                     Daily Growth Rate ([micro]m [day.sup.-1])

U. lens      52-64 Days           64-94 Days           94-114 Days

Old       79.4 [+ or -] 7.7   107.4 [+ or -] 4.2    82.8 [+ or -] 4.2
Young     94.9 [+ or -] 8.4   115.3 [+ or -] 14.8   87.8 [+ or -] 8.2

          Shell Length (mm)

U. lens       114 Days

Old       6.9 [+ or -] 0.2
Young     7.4 [+ or -] 0.2