Blacklip Abalone Research Articles

The relative suitability of the von Bertalanffy, Gompertz and inverse logistic models for describing growth in blacklip abalone populations ( Haliotis rubra) in Tasmania, Australia

Three candidate, non-nested, growth models (von Bertalanffy, Gompertz and inverse logistic) were fitted to multiple samples of tag-recapture data ( n = 27 samples) to determine the best statistical model for blacklip abalone ( Haliotis rubra) populations in Tasmania, Australia. Wild populations of blacklip abalone were sampled for growth data using tag-recapture methods. The best statistical model was identified for each sample using Akaike's Information Criteria and Akaike weights to measure the relative statistical fit. Using these criteria, the best fitting model was the inverse logistic for 21 of the 27 samples, both the von Bertalanffy and the Gompertz models were the best fitting model in three samples each. When the inverse logistic was the best fitting model it was the best unambiguously, as indicated by the high Akaike weight values (generally w i > 0.8 ; 0.65–1.0). In contrast, when either the von Bertalanffy or the Gompertz growth models were statistically optimal, the highest Akaike weights ranged between 0.15 and 0.44 across both models. We conclude that the use of either the von Bertalanffy or Gompertz growth models in the assessment of Tasmanian blacklip abalone would be statistically sub-optimal and may mislead assessments of Tasmanian abalone stocks. The inverse logistic model can be considered as a good candidate growth model for other fished invertebrate stocks.

Estimating Species-Specific Catch Rates in a Mixed-Species Dive Fishery

Catch-per-unit-effort (CPUE) is frequently used as a measure of relative abundance in fisheries stock assessment. Determining reliable estimates of species-specific CPUE is more challenging in multispecies, rather than single-species, fisheries because identification of appropriate effort data for each species is often difficult. Divers in the South Australian abalone fishery can harvest blacklip (Haliotis rubra) and greenlip (Haliotis laevigata) abalone simultaneously, but report only a single value for daily fishing effort. This is problematic because total allowable commercial catches are set for each species following species-specific stock assessments in which CPUE is a key index of relative abalone abundance. To provide an evidence-based approach to the identification of the most appropriate CPUE estimation method for ongoing assessment of the fishery, we assessed six diverse CPUE estimation methods for estimating annual, species-specific CPUEs using 30 y of data. The candidate CPUE estimation methods yielded relative CPUE time series with similar temporal trends throughout the 30-y period. These relative CPUE estimates each had low coefficients of variation and were highly correlated with one another, requiring consideration of other factors to determine a preferred method. Using a catch-weighted estimate of CPUE (CPUEwt) overcomes many of the problems associated with using the other five methods tested. Specifically, CPUEwt (1) weights each daily catch and effort objectively; (2) removes the need to “subset” the data subjectively, which ensures that data availability and representation are not reduced by arbitrary rules; and (3) is relatively simple to explain to stakeholders and can be applied consistently to greenlip and blacklip abalone at multiple spatial scales across the fishery. Although the requirement to estimate species-specific catch rates in mixed-species dive fisheries is rare, our analyses demonstrate that CPUEwt could provide a robust measure of species-specific CPUEs across other diverse multispecies fisheries.

Survey estimates of fishable biomass following a mass mortality in an Australian molluscan fishery

Mass mortality events are relatively uncommon in commercially fished populations, but when they occur, they reduce production and degrade ecosystems. Observing and documenting mass mortalities is simpler than quantifying the impact on stocks, monitoring or predicting recovery, and re-establishing commercial fishing. Direct survey measures of abundance, distribution and harvestable biomass provide the most tenable approach to informing decisions about future harvests in cases where stock collapses have occurred because conventional methods have been disrupted and are less applicable. Abalone viral ganglioneuritis (AVG) has resulted in high levels of mortality across all length classes of blacklip abalone, Haliotis rubra Leach, off western Victoria, Australia, since May 2006. Commercial catches in this previously valuable fishery were reduced substantially. This paper describes the integration of research surveys with commercial fishermen's knowledge to estimate the biomass of abalone on AVG-impacted reefs. Experienced commercial abalone divers provided credible information on the precise locations of historical fishing grounds within which fishery-independent surveys were undertaken. Abalone density estimates remained low relative to pre-AVG levels, and total biomass estimates were similar to historical annual catch levels, indicating that the abalone populations have yet to adequately recover. Survey biomass estimates were incorporated into harvest decision tables and used with prior accumulated knowledge of the populations to determine a conservative harvest strategy for the fishery.

Limited evidence for ecosystem‐level change on reefs exposed to Haliotis rubra (‘blacklip abalone’) exploitation

AbstractIt is increasingly recognized that fisheries must take the broader ecosystem into account for sustainable management of marine systems, requiring an understanding of the interaction between fished species and other organisms. This study uses a correlative approach to investigate potential interactions between benthic organisms and Haliotis rubra, a dominant herbivore that is the subject of a large and valuable commercial fishery in south‐eastern Australia. Specific emphasis was placed on understanding associations between H. rubra and understorey organisms, because particular understorey algae (crustose coralline algae) provide critical habitat for H. rubra larval recruitment and juvenile ecology. Broad‐scale surveys along the 6–8 m depth contour (the depth range where H. rubra fishing activity is intense) were conducted across four regions (separated by 104−105 m), including at least 10 sites (separated by 102−103 m) within each region. Positive correlations between H. rubra and crustose coralline algae were found, while negative correlations were observed between H. rubra and sessile invertebrates and understorey algae. While significant, these associations were weak and H. rubra abundance generally only explained a small proportion of the variability in the abundance of understorey organisms (r2 0.02–0.30). H. rubra abundance also had a minor influence on community‐level understorey patterns in comparison with differences in community structure attributable to regional variation. Patterns of H. rubra abundance and benthic community structure were also examined in relation to depth at a restricted number of sites. At sites where differences in understorey groups were evident, H. rubra abundance also varied significantly, highlighting the issue of confounding when contrasting patterns of understorey abundance using a correlative approach. Further manipulative experiments are required to confirm causal relationships; however, the available correlative evidence suggests limited ecosystem effects of H. rubra depletion at the scale of individual reefs.

Enhancing fishery assessments for an Australian abalone fishery using commercial weight-grade data

Effective management of commercial fisheries is dependent on the reliability of fishery assessments that, in turn, are determined by the quantity and quality of the available data. Data on the length-structure of the catch provide important information on exploited stocks, but representative sub-sampling is difficult to achieve, especially where numerous licence holders fish over large areas. This study evaluates the potential for routinely collected, commercial, weight-grade data to overcome this challenge and enhance assessment of the Western Zone blacklip ( Haliotis rubra) and greenlip ( Haliotis laevigata) abalone fisheries in South Australia. Current weight-grade data for blacklip abalone are inaccurate. However, the accuracy, rigour and consistency of the data for greenlip abalone confirm they are sufficiently reliable for aiding fishery assessments on this species. The greenlip abalone data were highly representative of the catch and the fishery and have been obtained in a consistent manner for >20 years. Changes in the composition of the grades in the catch provide a meaningful measure of change in the harvested stock. Similarly, measures of mean weight and number harvested, derived from the weight-grade data, are valuable as additional indices of stock status. These attributes substantially enhance the credibility of these data for use in assessing changes in stock status through time, and suggest these data should be used to supplement current assessments of this species. The value of the weight-grade data would increase substantially if the resolution was improved by using automated weighing and grading systems. The analysis of weight-grade data, routinely collected from numerous fisheries, is likely to benefit their assessment.

A simple model for the determination of the relative utilization efficiency of protein by blacklip abalone (Haliotis rubraLeach)

A 6-week growth rate trial of 6.7 mm ± 1.35 SD long blacklip abalone (Haliotis rubra) fed one of four graded protein feeds (26%, 32%, 37%, 45% crude protein, CP) resulted in a maximum average growth rate of 81 μm day−1 (percentage daily weight gain of 5.2% day−1) with the 45% CP diet. Based on the results, a new, simple, non-destructive method to calculate the relative utilization efficiencies (RUE) of nutrients is presented to estimate the relative contributions of a nutrient to growth, body maintenance and the excess used for energy. Calculations of RUE of protein estimated that at the maximum growth rate, 59% of the CP was responsible for growth, while 31% was used for body maintenance and an excess of 10% was lost and presumably catabolized for energy and carbohydrate anabolism. At the %CP where the highest proportion of CP was used for growth, i.e. the maximum RUE of protein for growth (slightly higher at 62%), 35% was used for body maintenance and only 3% of the excess was lost to energy.

Scale-dependent relationships between benthic habitat characteristics and abundances of blacklip abalone, Haliotis rubra (Leach)

Habitat characteristics can influence marine herbivore densities at a range of spatial scales. We examined the relationship between benthic habitat characteristics and adult blacklip abalone (Haliotis rubra) densities across local scales (0.0625–16 m2), at 2 depths, 4 sites and 2 locations, in Tasmania, Australia. Biotic characteristics that were highly correlated with abalone densities included cover of non-calcareous encrusting red algae (NERA), non-geniculate coralline algae (NCA), a matrix of filamentous algae and sediment, sessile invertebrates, and foliose red algae. The precision of relationships varied with spatial scale. At smaller scales (0.0625–0.25 m2), there was a positive relationship between NERA and ERA, and negative relationships between sediment matrix, sessile invertebrates and abalone densities. At the largest scale (16 m2), there was a positive relationship between NERA and abalone densities. Thus, for some biotic characteristics, the relationship between NERA and abalone densities may be scalable. There was very little variability between depths and sites; however, the optimal spatial scale differed between locations. Our results suggest a dynamic interplay between the behavioural responses of H. rubra to microhabitat and/or to abalone maintaining NERA free of algae, sediment, and sessile invertebrates. This approach could be used to describe the relationship between habitat characteristics and species densities at the optimal spatial scales.

Molecular Analyses Indicate Homogenous Structure of Abalone Across Morphologically DifferentHaliotis rubraCollections in South Australia

ABSTRACT It is widely accepted that the identification and management of abalone populations is critical for the ongoing sustainability of the fishery. However management of the endemic blacklip abalone throughout the Australian states generally occurs over large spatial scales and in some instances, across morphologically different populations on a finer scale. In this study, we use molecular techniques to show that blacklip abalone from seven sampling sites (of which four sites were characterized by stunted abalone growth patterns) in South Australia were genetically homogenous. Ten microsatellite loci and five composite restriction fragment length polymorphisms from the ND3/COIIImtDNA region showed high levels of genetic diversity across the collections, irrespective of growth characterization. Both molecular techniques also revealed a concordant outcome; no significant hierarchical variance was detected across geographically close, yet morphologically different collections (microsatellite φST = 0.002;...

Differences in abalone growth and morphology between locations with high and low food availability: morphologically fixed or plastic traits?

Many species of sedentary marine invertebrates exhibit large spatial variation in their morphology, which allow them to occupy a broad geographic distribution and range of environmental conditions. However, the detection of differences in morphology amongst variable environments cannot determine whether these differences represent a plastic response to the local environment, or whether morphology is genetically fixed. We used a reciprocal transplant experiment to test whether ‘stunted’ blacklip abalone (Haliotis rubra) are the result of a plastic response to the environment or fixed genetic trait. Furthermore, we related environmental factors, that affect food availability (density of abalone, water movement, algal cover and reef topography), to differences in growth and morphology. Morphological plasticity was confirmed as the mechanism causing morphological variation in H. rubra. Individuals transplanted to sites with ‘non-stunted’ H. rubra grew significantly faster when compared to stunted controls, whilst individuals transplanted to stunted sites grew significantly slower compared to non-stunted controls. The growth response was greater for individuals transplanted from ‘non-stunted’ to ‘stunted’ sites, suggesting that the environmental stressors in morphologically ‘stunted’ habitat are stronger compared to locations of faster growing morphology. We propose that these differences are related to resource availability whereby low algal cover and topographic simplicity results in stunted populations, whereas high algal abundance and topographic complexity results in non-stunted populations.

Using a simple morphometric marker to identify spatial units for abalone fishery management

AbstractSaunders, T., Mayfield, S., and Hogg, A. 2009. Using a simple morphometric marker to identify spatial units for abalone fishery management. – ICES Journal of Marine Science, 66: 305–314. Managing stocks of sedentary marine invertebrates is complicated by the highly structured populations they form. Blacklip abalone (Haliotis rubra) form isolated populations with variable life-history characteristics. Many of the populations are “stunted”, attaining a lower maximum size than those in adjacent areas. To reduce the risks of overfishing and localized depletion, management units (MUs) that encompass individual populations need to be determined, then managed according to their life-history characteristics. Here, potential MUs in a South Australian abalone fishery were identified from the broad-scale, spatial distribution of stunted and “non-stunted” populations of blacklip abalone, by applying a morphometric marker to commercial shell samples. Key life-history parameters of the populations within the potential MUs were estimated using relationships between the morphometric marker and blacklip abalone biology. Data from fine-scale systematic sampling by commercial fishers were used to validate spatial patterns observed from the more broadly distributed commercial catch samples. The location, distribution, and size of potential MUs were largely inconsistent with those of current management. The locations of two MUs (in Gerloffs Bay) were consistent across the broad- and fine-scale datasets, with the fine-scale samples more informative for identifying a potential boundary between them. The disparity between these data and current management arrangements are highlighted, and approaches for modifying them are discussed. This approach is among the first to provide a practical means of more closely aligning the scales of assessment and management with biological reality for sedentary marine invertebrates.

Genetic diversity and gene flow in collapsed and healthy abalone fisheries

Overexploitation of marine species invariably results in population decline but can also have indirect effects on ecological processes such as larval dispersal and recruitment that ultimately affect genetic diversity and population resilience. We compared microsatellite DNA variation among depleted and healthy populations of the black-lip abalone Haliotis rubra from Tasmania, Australia, to determine if over-fishing had affected genetic diversity. We also used genetic data to assess whether variation in the scale and frequency of larval dispersal was linked to greater population decline in some regions than in others, and if larval dispersal was sufficient to facilitate natural recovery of depleted populations. Surprisingly, allelic diversity was higher in depleted populations than in healthy populations (P < 0.05). Significant subdivision across hundreds of metres among our sampling sites (F(ST) = 0.026, P < 0.01), coupled with assignment tests, indicated that larval dispersal is restricted in all regions studied, and that abalone populations across Tasmania are largely self-recruiting. Low levels of larval exchange appear to occur at the meso-scale (7-20 km), but age estimates based on shell size indicated that successful migration of larvae between any two sites may happen only once every few years. We suggest that genetic diversity may be higher in depleted populations due to the higher relative ratio of migrant to self-recruiting larvae. In addition, we expect that recovery of depleted abalone populations will be reliant on sources of larvae at the meso-scale (tens of km), but that natural recovery is only likely to occur on a timescale unacceptable to fishers and resource managers.

Detection of QTL for growth rate in the blacklip abalone (Haliotis rubra Leach) using selective DNA pooling

The objective of this study was to identify QTL for growth rate in the blacklip abalone Haliotis rubra using selective DNA pooling. Three full-sibling families of H. rubra derived from crosses of wild broodstock were used. DNA was extracted from the largest and smallest 10% of progeny and combined into two pools for each phenotypic tail. The DNA pools were typed with 139 microsatellites, and markers showing significant differences between the peak height ratios of alleles inherited from the parents were individually genotyped and analysed by interval mapping. A strong correlation (r = 0.94, P < 0.001) was found between the t-values from the analysis of pools and the t-values from the analysis of individual genotypes. Based on the interval mapping analysis, QTL were detected on nine linkage groups at a chromosome-wide P < 0.01 and one linkage group at a chromosome-wide P < 0.05. The study demonstrated that selective DNA pooling is efficient and effective as a first-pass screen for the discovery of QTL in an aquaculture species.

Oceaniserpentilla haliotis gen. nov., sp. nov., a marine bacterium isolated from haemolymph serum of blacklip abalone

An aerobic, Gram-negative bacterial isolate, strain DSM 19503(T), was isolated from haemolymph serum of the blacklip abalone Haliotis rubra. Cells of strain DSM 19503(T) were vibrioid to spiral, motile and were able to pass through sterile filters with a pore size of 0.2 microm, indicating the small width of the bacterium. The isolate was psychrophilic, with the ability to grow at 2-8 degrees C. Oxidase activity was present, whereas catalase activity was absent. The nearly complete 16S rRNA gene sequence of strain DSM 19503(T) was obtained and phylogenetic sequence analysis showed that it formed a distinct genus in the family Oceanospirillaceae with highest sequence similarity of 92.9% to Oleispira antarctica RB-8(T). The cellular fatty acid composition was dependent on the growth medium used for cultivation. During growth on seawater agar, the fatty acid composition was most similar to that of Oleispira antarctica DSM 14852(T), with mainly C(16:0) (90.3%). In contrast, Columbia blood agar/NaCl-grown cells exhibited mainly C(10:0) 3-OH (11.8%), C(12:1)cis5 (8.2%), C(16:1)cis9 (29.6%), C(16:0) (19.3%) and C(18:1)cis9 (13.1%) fatty acids. On the basis of phenotypic, chemotaxonomic and genotypic data, strain DSM 19503(T) is considered to represent a novel species in a new genus for which the name Oceaniserpentilla haliotis gen. nov., sp. nov. is proposed. The type strain of Oceaniserpentilla haliotis is DSM 19503(T) (=LMG 24225(T)).

Effect of predator–prey and competitive interactions on size at emergence in the black-lip abalone Haliotis rubra in a Tasmanian MPA

Following more than a decade of protection from fishing activity, the direct and indirect effects of fishing on benthic community structure are becoming apparent inside no-take marine protected areas (MPAs) on Tasmania's east coast. Gradual increases in the abundance and average size of putative abalone predators inside the no-take Maria Island Marine Reserve (MIMR) have coincided with increases in the minimum size of the emergent abalone Haliotis rubra. This suggests that the threat of predation may influence the structuring of abalone populations. The abundance of emergent abalone was negatively associated with predator abundance, especially the rock lobster Jasus edwardsii, inside the MPA and in adjacent fished areas. Abalone leave cryptic habitat at smaller sizes in fished areas compared to abalone inside the MPA. Although the patterns in abalone size at emergence (SAE) were strongly correlated with rock lobster abundance and average size, the abundance of other predators (demersal predatory fish and crabs) or competitors (sea urchins) did not influence the patterns in abalone SAE. However, predation mortality in isolation could not account for the differences we observed in abalone size frequency distributions between MPA and adjacent fished locations. We suggest that a combination of factors including predation, intra and interspecific competitive interactions are responsible for patterns in abalone SAE.

Predicting biological variation using a simple morphometric marker in the sedentary marine invertebrate Haliotis rubra

Many sedentary marine invertebrates have a fine-scale (100s m) population structure that complicates their conservation and management. This is a consequence of the limited informa- tion on the boundaries between component populations and the biological variability among them. Blacklip abalone Haliotis rubra form discrete populations, many of which are 'stunted' with individ- uals reaching a maximum length less than those in adjacent areas. In the present study, we obtained information on the growth, size at maturity and fecundity of H. rubra from stunted and 'non-stunted' populations spread across broad (10s km) and fine (100s m) spatial scales. Relationships between each of these key population parameters and a simple 'morphometric marker' based on the relation- ship between shell length and shell height were also examined. Variation in broad-scale growth and size at maturity could primarily be attributed to differences between stunted and non-stunted sites. Within the stunted site, growth and size at maturity were substantially different over distances >150 m. However, within the non-stunted site these parameters tended to be similar across 1000 m. While the lowest fecundities tended to be in the stunted sites, there was significant overlap among all sites. These spatial patterns in biology were highly correlated with the spatial variability observed in a simple morphometric marker. These results suggest that this morphometric marker can be used as a tool for the spatial management of abalone fisheries by cheaply inferring key biological parameters for individual populations and identifing the boundaries among these based on these differences.

Growth and reproductive performance of triploid and diploid blacklip abalone,Haliotis rubra(Leach, 1814)

Growth and reproduction of triploid and diploid blacklip abalone Haliotis rubra (Leach, 1814) were compared in a 30-month study. Triploidy was induced by inhibition of the second polar body formation using 6-dimethylaminopurine (6-DMAP) or cytochalasin B (CB). There were no significant differences in growth and survivorship between triploid and diploid abalone. However, triploid abalone had a more elongated shell and greater foot muscles than diploid abalone. A slightly curvilinear growth in shell length was conformed to all treatments. While diploid abalone had reached sexual maturity and spawned during the study, gonadal development and gamete maturation were abnormal in triploids. Female triploids lacked an apparent gonad at the macroscopic level but microscopic examination revealed that they had a thin layer of oogonia development. In contrast, male triploids were able to form similar-sized gonads to diploids during most of the reproductive period, but with brown-yellow discolouration and stalled gametogenesis at spermatocyte formation. Sex ratio of triploid abalone did not deviate from 1:1. With the onset of sexual maturation, growth and gonadal maturation occurred concurrently in diploid abalone, and there was no indication that growth of (diploid) abalone was reduced.

A simple, cost-effective, morphometric marker for characterising abalone populations at multiple spatial scales

The ability to identify and separately manage component populations is becoming increasingly important in guarding against overexploitation of many marine species. Blacklip abalone (Haliotis rubra) form isolated populations with variable life history characteristics as a result of the heterogenous areas they inhabit. Many of these populations are ‘stunted’, reaching a lower maximum size compared with those in adjacent areas. We obtained a range of morphological measurements from samples of ‘stunted’ and ‘non-stunted’ H. rubra collected from sites spread across broad (tens of kilometres) and fine (hundreds of metres) spatial scales in southern South Australia. The ratio between shell length and shell height showed clear and significant differences among samples from ‘stunted’ and ‘non-stunted’ sites. The morphometric collections from the sub-sites suggested that ‘stunted’ populations existed at smaller spatial scales (up to 400 m) compared with that for ‘non-stunted’ populations (at least 1000 m). The ‘morphometric marker’ developed in the present study has the potential to be used as a tool to identify individual populations rapidly and cost-effectively that can then be managed separately. Our approach is applicable to other species of abalone as well as other sedentary invertebrates with limited larval dispersal.

Effects of air exposure on the lysosomal membrane stability of haemocytes in blacklip abalone, Haliotis rubra (Leach)

The neutral red retention (NRR) assay was used to evaluate the effects of air exposure on lysosomal membrane integrity in the haemolymph of blacklip abalone, Haliotis rubra, and its subsequent recovery in water. After acclimation in 16°C water for 7 days, abalone were exposed to an air temperature of 7, 16 or 23°C for 12 h in the air exposure experiment or to these three air temperatures, e.g., for 12, 24 or 36 h, followed by re-immersion in 16°C water in the lysosomal membrane stability recovery experiment. Statistical analyses of the air exposure experiment showed that when abalone were exposed to different air temperatures (7, 16 or 23°C), the lysosomal membrane stability was significantly affected by the air temperature, the exposure duration and their interaction. Air temperature similar to the acclimation temperature had a significantly lower impact on the lysosomal membrane stability within the initial 4.5 h in comparison with the other two temperatures in the same period. The lysosomal membrane stability recovery experiment showed that after air exposure durations of 12, 24 or 36 h, the re-stabilization of the lysosomal membrane was faster in the animals exposed to lower temperatures than those exposed to higher temperatures. The recovery of the lysosomal membrane stability in abalone exposed to lower 7°C air temperature was not significantly affected (F2, 66=0.251, P=0.779) by the exposure durations (12, 24 and 36 h) used in this study. Alternatively, the lysosomal membrane stability in abalone exposed to higher air temperatures of 16 or 23°C recovered at a faster rate when subjected to shorter durations of air exposure (F2, 66=3.663, P=0.031 and F1, 44=17.057, P<0.001 for 16 and 23°C respectively).

Evidence of genetic subdivision among populations of blacklip abalone (Haliotis rubra Leach) in Tasmania

The scale over which populations exchange individuals (migration) is central to ecology, and important for understanding recruitment and connectivity in commercial species. Field studies indicate that blacklip abalone (Haliotis rubra) have localised larval dispersal. However, genetic studies show differentiation only at large scales, suggesting dispersal over more than 100 km. Most genetic studies, however, have failed to test for subdivision at scales equivalent to field experiments. We used microsatellite DNA to investigate genetic structure at small scales (100 m to 10 km) in blacklip abalone in south-east Tasmania. We found significant subdivision (FST = 0.021; P &lt; 0.05) among sites, and hierarchical FST analysis indicated 64% of genetic variation was at the smallest scale, supporting field studies that concluded larval dispersal is less than 100m. We also tested if genetic differentiation varied predictably with wave exposure, but found no evidence that differences between adjacent sites in exposed locations varied from differences between adjacent sites in sheltered populations (mean FST = 0.016 and 0.017 respectively). Our results show the usefulness of microsatellites for abalone, but also identify sampling scales as critical in understanding gene flow and dispersal of abalone larvae in an ecologically relevant framework. Importantly, our results indicate that H. rubra populations are self-recruiting, which will be important for the management of this commercial species.

EFFECTS OF WATER TEMPERATURE ON THE LYSOSOMAL MEMBRANE STABILITY IN HEMOCYTES OF BLACKLIP ABALONE, HALIOTIS RUBRA (LEACH)

Neutral red retention (NRR) assay was used to evaluate the effect of changes in water temperature on lysosomal membrane integrity in the hemolymph of blacklip abalone, Haliotis rubra. Results from gradual temperature changes between 7°C and 16°C and between 16°C and 25°C showed that water temperatures within the range of 15°C to 17°C were optimal for maintaining lysosomal membrane integrity in this species. The rapid temperature changes between the ranges used in the gradual temperature change experiments indicated that when abalone were transferred directly between these temperatures their NRR time gradually increased or decreased to the level corresponding with the new temperature. However, when abalone were transferred directly between 7°C and 25°C or between 11.5°C and 20.5°C their NRR times initially decreased significantly, and then gradually increased to the levels corresponding with the new temperatures, indicating that different ranges of water temperature change can affect the lysosomal membrane integrity differently. The NRR times of blacklip abalone at 7°C, 16°C and 25°C were 40.0 ± 2.89 min, 113.33 ± 3.85 min and 35.0 ± 2.89 min, respectively.