Western Rock Lobster Research Articles

Determination of the Maximum Foregut Volume of Western Rock Lobsters (Panulirus cygnus) from Field Data

Two methods are presented for estimating the parameters of a line that describes the upper boundary of a triangular set of points. One method is a nonparametric maximum likelihood approach in which an unknown mixing distribution is introduced to account for the vertical spread of the points. The EM algorithm is used to maximize the likelihood. The other method is an iterative modification of the least squares procedure, in which points are weighted according to their distance from a trial line, and thus a new line is obtained; this forms the basis for the next iteration. This procedure is shown to be a onesided trimming method, equivalent to the least squares line through a subset of the data. Estimates of the slope, intercept and residual variance are obtained from this subset in the usual way. The study was motivated by data on the foregut contents of the rock lobster Panulirus cygnus. The two methods give similar results when applied to these data. The first method requires a large number of iterations and is expensive; the second method is fast and inexpensive. Simulations of the estimates obtained by the second method show that biases are present, although small, and that the estimates of slope and intercept are approximately normally distributed.

Factors affecting the recapture of undersize western rock lobster Panulirus cygnus George returned by fishermen to the sea

The rock lobster fishery of Western Australia is one of the largest of its kind; its average catch in the years 1974/75 to 1981/82 was almost 10000 tonnes. The fishery has been stable for many years, largely by virtue of licence limitation and other management measures. Among the regulatory measures is a requirement that all traps used in the fishery must be furnished with escape gaps and another requires fishermen to return to the sea all undersize lobsters that enter the traps, but fail to escape and consequently are brought on board the fishing boat when the trap is lifted. Despite the presence of the escape paps, considerable numbers of undersize lobsters are brought aboard; the number is estimated to be some 16 to 20 million in each season. Moreover, it has been estimated that about a quarter of these retained undersize lobsters remain on board for 10 min or more, and some have been observed to remain on board for more than two hours. Studies were therefore undertaken to ascertain whether this cipture-and-release experience was in fact causative of mortality. Laboratory experiments on animals exposed in direct sunlight resulted in an expected time for 50% mortality of 99, 158 and 233 min with increasing temperature compared with a time of 387 min for animals exposed under shade. Behavioural observations showed that as exposure time increased, returned animals exhibited a decreasing rate of descent through the water column, a decrease in the percentage of active animals and increased loss from predators. In addition, in ten laboratory experiments on octopus predation, octopus predated or injured animals exposed for 15 or 30 min, despite a recovery period of 3.5–5.5 h, but not on unexposed animals. Four tagging operations with over 7000 undersize animals resulted in a significant decrease in recapture rates by commercial fishermen with increasing exposure times. Damage (number of appendages lost) incurred by the rock lobsters and displacement beyond the home range were also generally found to reduce the recapture rates significantly. The combination of all these factors resulted in an estimated reduction in recapture rate of 14.6% in the 1978/79 fishing season and after taking into account natural mortality, this would have resulted in a loss of $A6.4 million to the fishery.

Migrations of pre-adult western rock lobsters, Panulirus cygnus, in Western Australia

In September 1978, 5 034 juvenile western rock (spiny) lobsters (Panulirus cygnus George) were tagged on a shallow coastal reef near Cliff Head in Western Australia. Of these, 26% were recaptured and removed from the population during the subsequent commercial fishery between 15 November 1978 and 30 June 1979. A resurvey of the tagging site in September 1979 found that size structure of the population was similar to the tagged population in September 1978 but that the 1979 population was composed of almost completely different individuals and only 2% of the rock lobsters tagged in September 1978 were recaught at this time. A wide range of movement was indicated by the recapture positions of 354 rock lobsters caught off the tagging site. Most travelled almost directly offshore but some also travelled offshore in a northwesterly direction. Both trends were shown in the data from the recaptures of 18 rock lobster released farther offshore from Cliff Head in September 1981, and of 19 released at a close inshore site in earlier years. Maximum offshore rates of movement of up to 622 m d-1 were recorded for distances up to 37 nautical miles (ca. 68 km). Growth rates for the tagged individuals which moved off, and those that were caught on, the tagging site were similar and close to growth rate under optimal conditions for this species. Under the present high levels of exploitation few, if any, of the rock lobsters remain to become permanent residents in the coastal reefs. It is believed that the north-westerly movements of some of the pre-adult rock lobsters, on their way to the breeding grounds on the outer edge of the continental shelf, are due to the upstream movement of these rock lobsters in a current from the north. The north-westerly movements allow the rock lobster population increased utilization of the food supplies of the coastal area.

Longevity, reproductive condition and growth of the western rock lobster, Panulirus cygnus george, reared in aquaria

Rock lobsters have been reared in the laboratory from the puerulus stage up to 13 years of age, under conditions of a constant temperature of 25�C or ambient temperatures (mean 20�C, range 15-26�C). The natural death of a male held at ambient temperatures occurred at 6 years of age, and at 25�C natural deaths occurred at 6 years. However, two males, both 12 years of age, one held at 25�C and the other at ambient temperatures, are still alive. Natural deaths of females occurred at 7 and 12 years of age at 25�C and 7 years at ambient temperatures. After reaching maturity, females held at 25�C spawned repetitively. The female that survived to 12 years of age spawned 47 times and produced an estimated 22 × 106 eggs during her lifetime. A fresh mating was not required for the fertilization of each batch of eggs spawned. The two surviving males both showed a change in growth pattern at approximately 8 years of age. This event was correlated with a behavioural change: they attacked and usually killed all moulting females held in the same aquarium. A new method of representing growth data for rock lobsters by fitting empirical stochastic differential equation models to each of a series of growth phases is described.

Calcium uptake by juvenile western rock lobster, Panulirus cygnus George, from dietary coralline algae

Foliose coralline algae form a large proportion of the diet of juvenile Panulirus cygnus George at some locations but its rôle in the diet is not clear. In the laboratory, early post-moult rock lobsters fed Corallina cuvieri Lamouroux, labelled with 45Ca primarily in the algal skeleton showed significant uptake of calcium compared with lobsters maintained in sea water containing dissolved 45Ca. Shortly after ingestion by the rock lobsters the isotopic calcium was distributed through all the soft tissues examined and the exoskeleton. After a 5-day period isotopic calcium levels had fallen in most soft tissues but were not significantly lower in the digestive gland, the mid-gut or the exoskeleton. The data indicate that calcium in the algal skeleton of dietary C. cuvieri is absorbed by the digestive system and may be important in the postmoult re-mineralization of the exoskeleton.

SYNTHESIS OF β-TRIMETHYLARSONIUMLACTATE

Abstract The biochemistry of arsenic is of considerable interest owing to the widespread presence of the element in marine organisms.1 The substance arsenobetaine (Me3-As+CH2CO2 −) has been isolated from the tail muscle of the western rock lobster (Panulirus longipes cygnus) and from the flesh of the dusky shark (Carcharhinus obscurus) and subsequently characterized by independent synthesis and X-ray crystal structure analysis.2 In addition, two arsenic-containing ribose derivatives have been isolated from the brown kelp Ecklonia radiata, which is part of the coastal ecosystem to which the rock lobster belongs.3 Assimilation, reduction, and methylation of arsenate also occurs in photosynthetic marine organisms,4,5 particularly in phosphate-depleted tropical waters, and in molluscs and ascidians, where arsenic accumulation was found to be greatest in organisms bearing symbiotic algae.5 Marine algae cultured in [74As] arsenate synthesize an arsenic-containing phospholipid.6 Base-catalysed deacylation of the...

Foregut evacuation of four foods by the western rock lobster, Panulirus cygnus, in Aquaria

Foregut evacuation of four foods (two species of foliose coralline algae Corallina cuvieri and Metagoniolithon stelliferum, the gastropod Littorina unifasciata and foot muscle of the abalone Haliotis roei) by P. cygnus at 25°C was examined by serial slaughter techniques. Animals were allowed to consume the weighed meals voluntarily, but because of indifference to the corallines it was necessary to allow a 2-h feeding period. Evacuation of all foods was rapid and almost complete 4-6 h after the termination of the feeding period.

Arseno-sugars from brown kelp (Ecklonia radiata) as intermediates in cycling of arsenic in a marine ecosystem

The high concentration (relative to seawater) of arsenic in many marine animals eaten as human food has stimulated interest in the cycling of arsenic in the marine environment1. Although arsenic is present as arsenobetaine [(CH3)3As+CH2COO−] in the western rock lobster2 (Panulirus cygnus), the dusky shark3 (Carcharhinus obscurus) and the school whiting4 (Sillago bassensis) it is not clear what intermediate stages are involved in the biosynthesis of this compound from arsenate, the major form of arsenic in seawater5. We now report the isolation of the two main arsenical constituents of the brown kelp, Ecklonia radiata, and their identification as a 2-hydroxy-3-sulphopropyl-5-deoxy-5-(dimethylarsenoso)furanoside and a 2,3-dihy-droxypropyl-5-deoxy-5-(dimethylarsenoso)furanoside. A β-ribo structure for the sugar system is strongly indicated in each case (A and B below). Ecklonia is the major organism that concentrates arsenic in the coastal ecosystem to which the western rock lobster and school whiting belong. It is clear that the compounds described here could readily be further metabolized to arsenobetaine and may well be the source of arsenobetaine in marine fauna associated with the region.

Behaviour of the Western Australian spiny lobster, Panulirus cygnus George, in the field and laboratory

The behaviour of the spiny lobster, Panulirus cygnus, of Western Australia was studied in the laboratory and field. A brief description of behavioural units is provided. A den residency survey showed only 3% of the lobsters sheltered singly, and the number of lobsters in a single den ranged from 1 to more than 100. Lobsters left dens in the evening and returned in the morning, following specific pathways along the reef face, implying knowledge of the local topography. The lobsters returned to the same area of the reef but not necessarily the same den after foraging. The occupancy of any particular den remained fairly constant over a period of time but changed markedly after a storm. The reactions of lobsters to a predator (Octopus tetricus) released at the mouth of a den were high alert postures, antennae pointing and waving, and slow retreat from the den. In a large laboratory pool, stridulation and tail flip were frequent when an octopus was out of its lair and moving around.

Isolation, crystal structure and synthesis of arsenobetaine, a constituent of the western rock lobster, the dusky shark, and some samples of human urine

Arsenobetaine has been isolated from the tail muscle of the western rock lobster (Panulirus cygnus George) and from the flesh of the dusky shark (Carcharhinus obscurus Le Sueur), both of which are commercially important seafoods. Trigonelline has also been isolated from the lobster and both arsenobetaine and trigonelline have been isolated from human urine obtained after ingestion of cooked rock lobster. The crystal structures of the monohydrates of arsenobetaine and trigonelline have been determined and a simple synthesis of arsenobetaine has been developed.

Increases in fishing effort in a limited entry fishery - the western rock lobster fishery 1963-1976

Increases in fishing effort in a limited entry fishery - the western rock lobster fishery 1963-1976

Distribution and dispersal of the phyllosoma larvae of the western rock lobster, Panulirus cygnus, in the southeastern Indian Ocean : Phillips, B. F., P. A. Brown, D. W. Rimmer and D. D. Reid, 1979. Aust. J. mar. Freshwat. Res., 30(6): 773–783

Distribution and dispersal of the phyllosoma larvae of the western rock lobster, Panulirus cygnus, in the southeastern Indian Ocean : Phillips, B. F., P. A. Brown, D. W. Rimmer and D. D. Reid, 1979. Aust. J. mar. Freshwat. Res., 30(6): 773–783

Population dynamics and management of the western rock lobster fishery

Population dynamics and management of the western rock lobster fishery

The effect of exogenous 20-hydroxyecdysone on levels of epidermal DNA and RNA in the western rock lobster

Direct measurements of epidermal DNA and RNA were made during the normal premoult period (proecdysis) and after 20-hydroxyecdysone (crustecdysone, β-ecdysone) injection in the western rock lobster, Panulirus longipes (Milne Edwards). The distal segments of the pleopods contain mostly epidermis, one appendage providing a readily removable sample adequate for DNA and RNA analysis. Amount per unit area appeared to be a more rational measure of polynucleotide changes during proecdysis than amount per unit weight of epidermis. Epidermal DNA increased during stages D 2 and D 3, and thereafter declined towards intermoult levels, but RNA increased steadily from stage D 1 and almost doubled by stage D 4. Injected crustecdysone caused a marked increase in RNA but not in DNA, and eventually depressed the latter. From this it was concluded that the principal effect of injected crustecdysone in the western rock lobster is to cause the epidermis to secrete new cuticle by inducing RNA synthesis directly and not by stimulating cellular multiplication.

Diurnal migration and vertical distribution of phyllosoma larvae of the western rock lobster Panulirus cygnus

Studies off the west coast of Australia showed that the phyllosoma larvae of Panulirus cygnus George undergo a diurnal vertical migration, with light as an important factor influencing the depth distribution of all 9 phyllosoma stages. The early stages (I to III) occurred at the surface at night regardless of moonlight intensity, whereas late stages (VI to IX) concentrated at the surface only on nights with less than 5% of full moonlight. Midday peak densities of early-stage larvae occurred in the 30 to 60 m depth range while those of mid (IV to VI) and late stages were in the 50 to 120 m range. Depths of peak densities of larvae increased with distance offshore. The limits of vertical distribution of the phyllosoma remained within ranges of illuminance which were estimated to be in the order of 50 to 250 μE m-2 sec-1 for early stages, 20 to 200 μE m-2 sec-1 for mid stages and 5 to 50 μE m-2 sec-1 for late stages. Minimal rates of net vertical movement were estimated for the larvae. Early stages exhibited mean net rates of ascent and descent of 13.7 and 13.0 m h-1, respectively, while the rates for mid stages were 16.0 and 16.6 m h-1 and for late stages 19.4 and 20.1 m h-1. Diurnal migrations and vertical distribution are shown to have a vital role in the relationships between circulation in the south-eastern Indian Ocean and the transport and dispersal of the phyllosoma larvae. The diurnal migrations of early stages place them at the surface at night, when offshore vectors of wind-driven ocean-surface transport dominate, and below the depth of wind-induced transport during the day, when offshore vectors are small or negative, thus accounting for their offshore displacement. Mid and late stages, because of their deeper daytime distribution and absence from the surface on moonlight nights, are predominantly subject to circulation features underlying the immediate surface layer. This is hypothesized to account for the return of the phyllosoma to areas near the continental shelf edge by subjecting them to a coastward mass transport of water which underlies the immediate surface layer.

Estimates of the Size of First Maturity of the Western Rock Lobster, Panulirus cygnus, Using Secondary Sexual Characteristics

The size of first maturity of P. cygnus has been estimated using the intersect analysis method and shown to be applicabIe to males as well as females which are smaller than males at this stage of development. The method which is based on significant differences between slopes of regression lines also demonstrated variation in size of maturity of males within the coastal population. Estimates were in close agreement with those obtained by examination of gonad material.

Distribution and Dispersal of the Phyllosoma Larvae of the Western rock Lobster, Panulirus cygnus, in the South-eastern Indian Ocean

Data on the phyllosoma larvae of P. cygnus caught on seven cruises carried out between April 1976 and January 1977 off the west coast of Australia are presented and discussed. The studies were undertaken to determine the length of the plankton cycle, the distribution of the phyllosoma in the south-eastern Indian Ocean and the extent of the offshore dispersal. Analyses showed the average length of the planktonic life to be less than one year and probably between 9 and 11 months. After hatching most early phyllosoma were transported offshore. Few larvae remained on or near the continental shelf. The maximum westward extent of the phyllosoma distribution of P. cygnus was not determined because significant numbers of phyllosoma were still found as far offshore as 99� 001E. (1500 km offshore), the furthest station sampled. The phyllosoma were distributed over an extensive area of the south-eastern Indian Ocean, and there were few stations beyond the continental shelf between 24� 30'S. and 35� 00'S., from 99� 00'E. to 115� 00'E., during midwinter, at which phyllosoma were not caught. The highest densities of mid-and late-stage phyllosoma occurred between 111� 00' E. and 104� 00' E. (between 375 and 1030 km offshore), at 29� 30'S. The area of greatest abundance was due west of the approximate centre of the adult distribution on the coast. The significance of the circulation of the south-eastern Indian Ocean in the transport of the larvae is discussed.

Assessment of the Stocks of the Western Rock Lobster Panulirus cygnus Using Surplus Yield Models

Four different surplus yield models (namely Schaefer, GENPROD, PRODFIT and delayed recruitment) were applied to the data from the fishery for the western rock lobster. The four models all provided similar estimates of maximum yield and optimum effort. These estimates were 8.0-8.6 × 106 kg at a level of effort of 5.6-5.9 × 106 units. Variation in catches was shown to increase with increasing effort although this could not be attributed to increased variation in catch per unit of effort. It was considered that while the four surplus yield models provided good descriptions of the relationship between total catch and equilibrium effort up to the level of effort so far encountered in the fishery, not as much confidence could be placed in their ability to predict catches at levels of effort outside the already observed range.

Water uptake at ecdysis in the western rock lobster

Water ingestion at ecdysis by the western rock lobster. Panulirus longipes (Milne Edwards) was investigated using the reference markers 51Cr-EDTA and 58Co-EDTA. Two possible mechanisms controlling water absorption were examined: first, changes in osmolarity of blood and muscle and secondly, the effects of extracts of central nervous system. Water ingestion was 16.071 ± 2.365 ml kg −1 h −1 during swelling just before ecdysis (stage D 4(S)) and 23.099 ± 1.238 ml kg −1 h −1 during stage A. There was no significant absorption in the foregut or hindgut and the digestive gland appeared to be the site of major absorption. Total water ingested during stages D 4(S) and A was 13.7% of the proecdysis weight. Calculating total water uptake by wet weight differences plus wet weight of exuviae gave a value that was too high and instead weight increases were calculated from a carapace length-weight formula. Allowing for postecdysis increase in weight the net increase at ecdysis was 18.4–21.4% which was 4.7–7.7% more than the water ingested. It was concluded from this that water enters the body at ecdysis both by ingestion and by absorption through the external surface. It is suggested that water ingestion provides the main source of swelling of the cephalothorax in stage D 4(S) and after ecdysis both ingested water and external absorption enables the flaccid abdomen and appendages to swell rapidly. Statistically significant differences were found in the concentrations of total cations and chloride in leg muscle during the transition from stage C 4 to late D 4 but the trends were not consistent and probably have no functional significance. There were no changes in the concentration of osmotically active organic constituents. The freezing-point depression of the blood in stage D 4 was significantly higher than that in stage C 4( P < 0.02) but the mean difference was only 1.8%. It was concluded that osmoticchanges were unlikely to be an important mechanism of water uptake. Water-soluble extract (WSE) and acetone-soluble extract (ASE) of brains and first ventral ganglia were without significant effect when compared together with controls. There was a barely significant decrease, however, in water in the proventriculus of WSE-treated animals compared with that of controls ( P < 0.05). and further investigation on the effects of such extracts on water uptake at ecdysis is warranted.

Changes in apparent water permeability during the moulting cycle in the western rock lobster

The kinetics of water exchange, as measured by 3H 2O fluxes, were examined in the western rock lobster, Panulirus longipes (Milne Edwards) during stages C 4, D 3, D 4, D 4-E and B 1 of the moulting cycle. A series of samples of blood and external water was taken during each experiment and the inward and outward rate constants found using the SAAM 25 computer program, assuming a simple 2-compartment model with reversible exchange. Both inward and outward turnover rates remained constant up to the swelling prior to ecdysis when there was an increase of 203% inwards compared with 133% outwards. The latter increased in stage B 1, so that both rates were comparably high, probably due to the increased permeability of the soft integument. Further analysis showed that the rock lobster does not behave as a single compartment with respect to tritiated water. Two compartments were resolved by graphical analysis, one with fast and the other with slow exchange. It is suggested that blood and tissue ‘free’ water comprise one compartment and chemically ‘bound’ water the other, with fast exchange between the free and bound water and relatively slow exchange between free body water and the external medium.