South African Abalone Haliotis Midae Research Articles

Can the End Products of Anaerobic Metabolism, Tauropine and D-lactate, Be Used As Metabolic Stress Indicators During Transport of Live South African Abalone Haliotis Midae?

This study was undertaken to investigate whether the accumulation of end products of anaerobic metabolism can be used as an early indicator of deteriorating conditions during transport of live abalone Haliotis midae. A first series of experiments revealed that the enzyme tauropine dehydrogenase, responsible for the production of tauropine, is present in high activities (54 U g wet weight−1) in the shell adductor muscle, but D-lactate dehydrogenase, responsible for the production of D-lactate, is the predominantly active enzyme (10 U g wet weight−1) in foot muscle. The next series of experiments investigated the potential of anaerobic metabolism in the abalone by subjecting the gastropod to either functional anoxia (exercise metabolism) or 6 h of environmental anoxia (seawater gassed with nitrogen). Exercise, primarily powered by the shell adductor muscle, was mainly fueled by glycolysis resulting in the production of tauropine, whereas during 6 h of experimental anoxia, fermentation of glycogen led to the formation of mainly tauropine in the shell adductor muscle and mainly D-lactate in the foot muscle. The last experiment, investigating changes in these metabolites during simulated (abalone packed in oxygen-filled plastic bags resting on foam sponges soaked in seawater) transportation stress of up to 36 h at 7 and 10°C, clearly showed that tauropine accumulation in the shell adductor muscle and D-lactate accumulation in the foot muscle is time-dependent. Both metabolites are already produced during the first 6 h of simulated transportation (especially at 10°C), indicating that aerobic metabolism is impaired at an early stage of transportation. Hence, these metabolites can serve as indicators of the conditions abalone were subjected to during transport. Furthermore, abalone use the strategy of metabolic depression in this simulation experiment, as indicated by the decreased glycolytic flux in various tissues.

Optimum dietary crude protein level for growth in South African abalone (Haliotis midae L.)

A 95-day feeding trial was conducted to evaluate the effects of dietary crude protein level on total body weight gain and protein gain of juvenile (4.89 ± 0.57 g) South African abalone (Haliotis midae). Six semi-purified diets containing casein, fish meal and cottonseed meal as protein sources, and with crude protein levels ranging from 54.8 to 479.2 g kg )1 dry matter (DM), were fed to four tanks containing 30 abalone each in a continuous flow system. No differences (P > 0.05) were found in moisture, ash or lipid content of soft-body tissue as dietary crude protein level increased, indicating that differences (P < 0.05) in soft-body protein content were solely due to dietary crude protein level. The relationships between dietary crude protein level and total body weight gain and protein gain were analysed by brokenline and second-order polynomial regression models. Based on total body weight gain, 358.7 g kg )1 DM dietary protein from good quality sources is recommended for maximum growth of juvenile H. midae, while, if dietary protein is reduced to 280.7 g kg )1 DM, growth will be depressed with 5gk g )1 .

Apparent and true availability of amino acids from common feed ingredients for South African abalone (Haliotis midae L.)

Apparent (APD) and true (TPD) protein digestibility and apparent (AAAA) and true (TAAA) amino acid availability of fish meal and plant protein ingredients utilized in the South African animal feed industry (corn gluten meal, soya bean meal, cottonseed meal, sunflower meal, canola meal, peanut meal, lupins and faba beans), incorporated at 450 g kg−1 into single protein diets, were determined with juvenile South African abalone (Haliotis midae). Soya bean meal (96.34%) and lupins (96.51%) presented the highest APD values, with corn gluten meal (76.08%) the lowest value, while values for sunflower meal (92.21%), canola meal (93.94%) and faba beans (93.17%) were above 90%. APD values for cottonseed meal (86.28%) and peanut meal (86.73%) were comparable with that of fish meal (82.94%). A correlation coefficient (r) of 0.99 was found between ADP and mean AAAA. Furthermore, amino acid availabilities were relatively consistent within various feed ingredients. The mean amino acid secretion from a protein-free diet was 19.08 mg 100 g−1 dry diet, resulting in a mean increase of 1.88% units over all feed ingredients when comparing TAAA with AAAA. Calculated APD according to APD coefficients determined with single protein diets underestimated determined APD in several compound diets by 1.10–6.50%, while mean AAAA was underestimated by 6.93%.

Development of a Monoclonal Antibody Detection Assay for Species-Specific Identification of Abalone

Species identification based on biochemical and molecular techniques has a broad range of applications. These include compliance enforcement, the management and conservation of marine organisms, and commercial quality control. Abalone poaching worldwide and illegal trade in abalone products have increased mainly because of the attractive prices obtained and caused a sharp decline in stocks. Alleged poachers have been acquitted because of lack of evidence to correctly identify species. Therefore, a robust method is required that would identify tissue of abalone origin to species level. The aim of this study was to develop immunologic techniques, using monoclonal and polyclonal antibodies, to identify 10 different abalone species and subspecies from South Africa, the United States, Australia, and Japan. The combination of 3 developed monoclonal antibodies to South African abalone (Haliotis midae) enabled differentiation between most of the 10 species including the subspecies H. diversicolor supertexta and H. diversicolor diversicolor. In a novel approach, using antibodies of patients with allergy to abalone, the differentiation of additional subspecies, H. discus discus and H. discus hannai, was possible. A field-based immunoassay was developed to identify confiscated tissue of abalone origin.

Influences of the sea urchin Parechinus angulosus (Leske) on the feeding behaviour and activity rhythms of juveniles of the South African abalone Haliotis midae Linn

Almost all juveniles of the abalone Haliotis midae shelter beneath the urchin Parechinus angulosus. Field observations showed that all juvenile abalone remained concealed under urchins by day. Even by night, only 10–25% left the protection of urchins to forage. Offered a choice of rocks or urchins in tide pools, the juveniles strongly preferred urchins rather than rocks. In aquaria, both urchins and abalone were active only at night. The frequency with which juvenile abalone left shelter was greatest if rocks constituted the only form of concealment, intermediate when they sheltered under urchins alone and least when the urchins had access to drift kelp. The treatment that provided abalone with both urchins and drift kelp had the lowest rate of urchin movement and the highest microalgal benthic standing stocks, the gut contents of the abalone comprised mainly kelp and their gut fullness indices were higher than in the other treatments. Concealment of juvenile abalone beneath urchins evidently provides them with several benefits. First, when urchins trap drift kelp, the abalone are capable of feeding on it and enhance their uptake of food. Second, this behaviour reduces the frequency with which juvenile abalone leave the shelter of urchins. Third, urchins that trap drift kelp reduce their rates of movement and their consumption of benthic microalgae, and we speculate that this may improve feeding conditions for the early postsettlement “recruit” stages of H. midae, and reduce the risk of urchins “bulldozing” them. Thus, for a complex of reasons, the dependency of P. angulosus on drift kelp provides benefits to abalone that would not exist if this urchin acted as a conventional grazer.

Effects of benthic grazers on microalgal communities of morphologically different encrusting corallines: implications for abalone recruits

Recruits of the South African abalone Haliotis midae are more abundant on irregularly textured than on smooth encrusting corallines, and experimental removal of the urchin Parechinus angulosus leads to the virtual disappearance of H. midae recruits. Explanations include the following; (1) In the absence of larger grazers, prostrate diatoms that are preferentially consumed by abalone recruits become displaced by less suitable overstorey diatoms, filamentous algae or blue-green algae; (2) textured corallines protect pockets of suitable diatoms, whereas large grazers eliminate these from smooth corallines. We tested these possibilities in aquarium experiments in which microalgal communities were grown on artificial coralline mimics with different textures and then exposed to different grazers at densities simulating those in the field. Microalgal standing stocks (measured as chlorophyll a) increased in the absence of grazers, but this was reflected only in the amounts of fila- mentous and blue-green algae. Diatoms remained unchanged in quantity and community composi- tion between different grazing treatments and substratum textures. Changes in diatom communities following urchin removal are thus unlikely to explain the ensuing disappearance of abalone recruits, although changes in filamentous and blue-green algae may do so. Textured surfaces did, however, consistently support higher stocks of microalgae than smooth surfaces (in either the presence or the absence of grazers), which may account for the preference of abalone recruits for irregular encrust- ing corallines in the field.

Interrelations among rock lobsters, sea urchins, and juvenile abalone: implications for community management

Field and laboratory experiments demonstrate that juveniles of South African abalone (Haliotis midae) depend vitally on the protection from predation that they gain from living concealed beneath Cape urchins (Parechinus angulosus). Recent reports suggest that rock lobsters (Jasus lalandii) have increased substantially in the region where the commercial abalone fishery is centered. This increase has been blamed for a recorded collapse of urchin populations and dramatic reductions in the numbers of juvenile abalone. We verified the substantial increase in rock lobster abundance there. Surveys covering 200 km of coastline showed that densities of urchins were negatively correlated with those of large lobsters (&gt;68 mm carapace length) and that densities of juvenile abalone were positively correlated with those of urchins. The indirect negative effects of rock lobsters on juvenile abalone clearly pose a major threat to the abalone industry, already under stress from poaching. Quantification of the relationship between juvenile abalone and urchins and between urchins and rock lobsters allows a forecast of the magnitude of lobster harvesting necessary to reduce them to a level at which urchins may recover and sustain juvenile abalone. The complex interactions involved emphasize the importance of an ecosystem approach for the management of these stocks.

Interrelations among rock lobsters, sea urchins, and juvenile abalone: implications for community management

Field and laboratory experiments demonstrate that juveniles of South African abalone (Haliotis midae) depend vitally on the protection from predation that they gain from living concealed beneath Cape urchins (Parechinus angulosus). Recent reports suggest that rock lobsters (Jasus lalandii) have increased substantially in the region where the commercial abalone fishery is centered. This increase has been blamed for a recorded collapse of urchin populations and dramatic reductions in the numbers of juvenile abalone. We verified the substantial increase in rock lobster abundance there. Surveys covering 200 km of coastline showed that densities of urchins were negatively correlated with those of large lobsters (>68 mm carapace length) and that densities of juvenile abalone were positively correlated with those of urchins. The indirect negative effects of rock lobsters on juvenile abalone clearly pose a major threat to the abalone industry, already under stress from poaching. Quantification of the relationship...

Distribution and population dynamics of Porphyra (Bangiales, Rhodophyta) in the southern Western Cape, South Africa

Although Porphyra is commercially farmed in many countries, in South Africa only small harvests of wild populations for sale as nori have been carried out. The discovery that Porphyra improves growth of South African abalone (Haliotis midae) farmed inland-based tanks has led to increased pressure to harvest wild populations. This paper reports on a survey of the distribution and seasonality of Porphyra in the southern Western Cape. Porphyrawas present at all sites surveyed, and showed considerable temporal variation. A significant amount of the Porphyra present is in reserves and therefore protected from harvesting. Close rexamination of one site revealed seasonal populations of Porphyra that occupied different niches dependent on season. Recruitment peaked in spring and autumn, leading to dense summer and winter populations. Summer populations generally grew lower in the eulittoral than winter populations. No pattern in the mortality of larger thalli wasde tected, though sporeling mortality was high following recruitment peaks. Although it seems that most sites in the southern Western Cape are suitable for harvesting, the taxonomy of the genus in the region urgently needs revision if populations are to be appropriately managed.

Growth and movement of the South African abalone Haliotis midae: A reassessment

Growth rates of a number of Haliotis midae populations around the South African coast were studied by means of tagging. These populations ranged from the cool waters of the western coast to the more temperate environment of the eastern Cape. Standard von Bertalanffy growth curves were fitted and growth parameters derived. These ranged from 0.19 to 0.25 for K, the average rate at which L∞ is approached, and from 156 to 173 for L∞, the average theoretical maximum length. These indicate far higher growth rates than were previously published for this commercially fished species, and the reasons for this difference are discussed. The expectation that growth rates would be fastest in the warmer eastern Cape waters was not realized, there being no significant difference in growth between the Bird Island population on the eastern coast and the Robben Island population on the western coast. These new growth parameters indicate that H. midae in the commercial fishery grounds is attaining sexual maturity some four years earlier, and the minimum legal size some five years earlier, than previously considered. This has considerable significance for modelling studies presently underway. Movement of a small population of adult H. midae was studied over a three-year period, after which 47% of the original abalone were still present on the study site. Of these, 81.5% still occupied exactly the same position on the rocks. This indicates that H. midae that have located an optimum habitat, and that are not disturbed, tend not to move.

Bias towards brown algae in determining diet and food preferences: The South African abalone Haliotis midae

Previous studies of gut contents have suggested that Haliotis midae in South Africa feeds selectively on brown algae, and that the feeding preferences of this abalone might differ from other species in favouring tannin-rich foods in accord with an evolutionary hypothesis based on food availability. In the present study, H. midae specimens were starved for one month, then fed a variety of algae and frozen at intervals thereafter, to assess whether gut contents provide a good estimate of diets. Fragments of the brown kelps Ecklonia maxima and Laminaria pallida disappeared more slowly than did green or red algae from the abalone crop, as expected from work on H. rubra in Australia and the fact that the kelps contain high concentrations of phlorotannins. The apparent extent to which H. midae feeds on E. maxima, derived from gut content analysis, is biased. There is thus no good evidence that any abalone, faced with brown algae rich in polyphenolics, have adapted to select these foods.

Observations on the spawning, development and rearing of the South African abaloneHaliotis midaeLinn.

A description is given of the first successful controlled breeding of the South African abalone Haliotis midae. Gametes of ripe abalone were obtained from spontaneous spawnings as well as by subjecting animals to spawning stimuli. The larval period is five days at 20°C and seven days at 17,5°C. The first respiratory pore is completed at a shell length of 2,3 mm and the first shell ridge can be observed at approximately 23 mm. Benthic diatoms on fibreglass plates served as food for post-larval stages to a length of 5–8 mm. Larger juveniles were fed the seaweeds Plocamium spp. and Ulva fasciata. Shell pigmentation is affected by the food consumed. Variable growth rates for individuals from the same spawning were observed.