Roy Melville-Smith

Characterization of polymorphic microsatellite loci in the western rock lobster (Panulirus cygnus)

Nine microsatellite loci were identified in the western rock lobster (Panulirus cygnus) using two different methods. The first method involved the screening of a small, fragment, partial genomic library with a radioactive (CA)6 probe. The second method, was based upon an enrichment method and used biotinylated, tetranucleotide microsatellite oligonucleotide capture probes. The nine loci described are all very polymorphic, with 11 to 34 alleles observed for each locus and heterozygosities ranging from 0.58 to 0.86. These microsatellite loci will be useful in analysing both the population structure and the mating systems used by this species and will add important information for the management of the wild stocks of this economically important species.

Visual assessment of the reproductive condition of female western rock lobsters (Panulirus cygnus)

Abstract An important issue when surveying the reproductive condition of large numbers of female Panulirus cygnus in the field is that each animal must be assessed quickly and accurately on the basis of only a few easily discernable criteria. The four biological criteria most commonly recorded for each lobster are: (1) ovigerous setae condition (not present, partially developed, and fully developed); (2) the presence (unused or eroded) of a spermato‐phore mass; (3) the presence and developmental stage of external ova; and (4) the visual appearance of the ovaries through the dorso‐thoracic musculature. Using the above criteria each female can then be assigned to a reproductive state, i.e., immature, inactive breeder, single breeder, or double breeder. This study compared external assessments with internal cellular development of the ovary (via histology) and elucidated the shortcomings of the external technique. This has resulted in the production of a modified set of criteria that, if applied to samples collected during the peak of the breeding season, enables the breeding state of a female western rock lobster to be more accurately determined in the field without causing it any damage. The height of the breeding season is the optimum time for stock egg production assessment.

NEITHER MATERNAL SIZE NOR SITE OF SPAWNING INFLUENCES LARVAL COMPETENCY IN WESTERN ROCK LOBSTER PANULIRUS CYGNUS GEORGE

Abstract The size of the western rock lobster broodstock is variable over the range of the Western Australian fishery, due to regional differences in the density and length structure of the stock and the females size at maturity. Management regulations do not currently discriminate in the protection afforded to the broodstock in the different regions. This study has examined whether regional and size differences in early egg diameter, phyllosoma length at hatch and phyllosoma competency, are related to lipid class and fatty acid composition, protein composition and water content in late stage eggs and early stage phyllosoma larvae. A positive relationship, particularly to phyllosoma competency, would have management implications for the protection of broodstock in different parts of the fishery. Females were sampled in three size groups captured in two sampling regions (Abrolhos Islands 60-70 and 80-90 mm CL; coastal 80-90 and > 95 mm CL). Mostly, eggs and larvae from different maternal size classes and regions were not significantly different with respect to lipid class and fatty acid composition, protein composition and water content, and larval competency. The lipid classes of eggs differed significantly (P < 0.02) between the three maternal size-classes; fatty acids differed significantly between both eggs and phyllosoma grouped by maternal catch site and size-class (P = 0.02 and 0.003, respectively); and there was no correlation between biochemical differences and larval competency. These results imply that maternal identity and subsequent diet may have a greater influence on larval competency in P. cygnus than the maternal attributes (size and capture site) that were tested.

Effect of reproductive state and sex on movement and food consumption of western rock lobster (Panulirus cygnus) in a tank environment

Abstract The catchability of western rock lobsters (Panulirus cygnus) during the spawning season (October and November) may be affected by their reproductive state. In this study, movement and food consumption of males and females of different reproductive states held in laboratory tanks were measured as proxies for catchability. Density of lobsters was found to influence both movement and food consumption. Solitary animals and, to a lesser extent, two lobsters per tank, were more sedentary and consumed significantly less food than animals at a density of three or four specimens per tank. Tests using three animals per tank confirmed that mature, unmated, and ovigerous females carrying early stage eggs moved more frequently away from their shelters than males or females carrying late stage eggs (P < 0.0001, d.f. = 3). Further, unmated females and females with early stage eggs recorded significantly higher food consumption (P < 0.0061, d.f. = 3) compared with males or females carrying late stage eggs. The greater time spent away from shelter and also food consumption make unmated females and females with early stage eggs likely to be more catchable than males or females with late stage eggs. As catchability is commonly used to obtain population estimates from survey data, these results have implications for surveys which use catch rates of breeding animals as indicators of egg production.