scholarly journals Using an oceanographic model to investigate the mystery of the missing puerulus

2021 ◽  
Author(s):  
Jessica Kolbusz ◽  
Tim Langlois ◽  
Charitha Pattiaratchi ◽  
Simon de Lestang
Keyword(s):  
Early Summer ◽  
Rock Lobster ◽  
East Indian ◽  
Leeuwin Current ◽  
Recruitment Failure ◽  
Pelagic Larvae ◽  
Consistent Increase ◽  
Panulirus Cygnus ◽  
Offshore Transport ◽  
Management Changes

Abstract. Dynamics of ocean boundary currents and associated shelf processes can influence onshore/offshore transport of water, critically impacting marine organisms that release long-lived pelagic larvae into the water column. The western rock lobster, Panulirus cygnus, endemic to Western Australia, is the basis of Australia's most valuable wild-caught commercial fishery. After hatching, western rock lobster larvae (phyllosoma) spend up to 11 months in offshore waters before ocean currents and their ability to swim, transport them back to the coast. The abundance of western rock lobster puerulus (settlement phase post phyllosoma) has historically been observed to be positively correlated with the strength of the Leeuwin Current, and an index of puerulus numbers is used by fisheries managers as a predictor of subsequent lobster abundance 3–4 years later. In 2008 and 2009 the Leeuwin Current was strong, yet a settlement failure occurred throughout the fishery prompting management changes and a rethinking of environmental factors associated with their settlement. Thus, understanding factors that may have been responsible for the settlement failure is important for fisheries management. Oceanographic parameters likely to influence puerulus settlement were derived for a 17 year period to investigate correlations. Analysis indicated that puerulus settlement at adjacent monitoring sites have similar oceanographic forcing with kinetic energy in the offshore and the strength of the Leeuwin Current being key factors. Settlement failure years were synonymous with “hiatus” conditions in the south-east Indian Ocean, and periods of sustained cooler water present offshore. Post 2009, there has been an unusual but consistent increase in the Leeuwin Current during the early summer months with a matching decrease in the Capes Current, that may explain an observed settlement timing mismatch compared to historical data. Our study has revealed that a culmination of these conditions likely led to the recruitment failure and subsequent changes in puerulus settlement patterns.

scholarly journals Changes in Panulirus cygnus Settlement Along Western Australia Using a Long Time Series

2021 ◽  
Vol 8 ◽  
Author(s):  
Jessica Kolbusz ◽  
Simon de Lestang ◽  
Tim Langlois ◽  
Charitha Pattiaratchi
Keyword(s):  
Western Australia ◽  
Environmental Changes ◽  
Marine Invertebrate ◽  
Temporal Distribution ◽  
Second Phase ◽  
East Indian ◽  
Recruitment Failure ◽  
Starting Point ◽  
Before And After ◽  
Panulirus Cygnus

The pelagic development stages of many marine invertebrate species dictates their spatial and temporal distribution once reaching their benthic second phase of life. This life cycle is associated with the Western Rock Lobster (Panulirus cygnus) along the coast of Western Australia. Over the past 50 years, the number of puerulus reaching the nearshore reefs after their first 9 to 11 months of pelagic life in Western Australia has been monitored. These numbers, collected now at eight sites over the latitudes of the fishery, are indicative of the catchable stock 3–4 years into the future. In 2008, the fishery experienced a recruitment failure which lasted for several years before recovering to mean numbers pre-2008. This was associated with spatial and temporal shifts in the patterns of puerulus settlement. Previous research has hypothesized that physical and biological conditions in the south-east Indian Ocean no longer favored their survival. However, this decline has not been attributed to a single process. As the recovery is ongoing, contrasts in the settlement data before and after the decline are not completed. Here we characterize the data using ANOVA and pairwise comparisons to gain a better understanding of the typical patterns after the decline. Our results demonstrate that there has been a significant reduction in puerulus numbers over the first half of the season at all sites post decline. For the sites south of Lancelin there has been a significant reduction in puerulus numbers over the whole season. In addition, sites that show signs of recovery indicate that the majority of settlement occurred in the second half of the season. We anticipate these results to be the starting point for focused research into the environmental changes which may have occurred to generate these shifts in settlement numbers both from a timing and spatial perspective.

Environmental effects on recruitment of the western rock lobster, Panulirus cygnus

2001 ◽  
Vol 52 (8) ◽  
pp. 1167 ◽  
Author(s):  
Nick Caputi ◽  
Chris Chubb ◽  
Alan Pearce
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Larval Survival ◽  
Current Strength ◽  
Sea Surface ◽  
Rock Lobster ◽  
Leeuwin Current ◽  
Westerly Winds ◽  
Highly Correlated ◽  
Panulirus Cygnus

The Leeuwin Current, which brings warm, nutrient-poor waters southward along the edge of the West Australian continental shelf, is positively correlated with western rock lobster (Panulirus cygnus) puerulus settlement along the coast. Westerly winds, also positively correlated with puerulus settlement, probably assist the transport of larvae to the coast during settlement. We examined relationships between (a) monthly sea-surface temperature where phyllosoma larvae occur – and annual levels of puerulus settlement at locations throughout the fishery and (b) monthly variation in Leeuwin Current strength (and westerly winds) and annual puerulus settlement later in the year (August–January). The Leeuwin Current, when it begins to strengthen during February–April, was highly correlated with puerulus settlement; sea-surface temperature during this period may have strongly influenced puerulus settlement at many locations. Its influence on puerulus settlement may have been due to improved larval survival and growth caused by higher water temperatures associated with a stronger Leeuwin Current in April or to increased retention of larvae close to the coast. In years when the southward-flowing Leeuwin Current was very strong, settlement in the southern locations was relatively higher than that farther north. In years of strong puerulus settlement, settlement also occurred earlier in the season.

Ocean circulation, Stokes drift, and connectivity of western rock lobster (Panulirus cygnus) population

2011 ◽  
Vol 68 (7) ◽  
pp. 1182-1196 ◽  
Author(s):  
Ming Feng ◽  
Nick Caputi ◽  
James Penn ◽  
Dirk Slawinski ◽  
Simon de Lestang ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
West Coast ◽  
Early Stage ◽  
Austral Summer ◽  
Early Summer ◽  
Stokes Drift ◽  
Rock Lobster ◽  
The West ◽  
Larval Phase ◽  
Panulirus Cygnus

An individual-based model, incorporating outputs of a data-assimilating hydrodynamic model, was developed to investigate the role of ocean circulation in the recruitment processes of western rock lobster ( Panulirus cygnus ) during its 9- to 11-month larval phase off the west coast of Australia. During austral summer, strong northward alongshore winds aid the offshore movement of early-stage model larvae from midshelf hatching sites into open ocean; during austral winter, eastward flows that feed the enhanced Leeuwin Current facilitate onshore movement of late-stage larvae towards nearshore habitats. Stokes drift induced by swells from the Southern Ocean is critical to retain larvae off the west coast. Diurnal migration and temperature-dependent growth are also important. Model larvae hatched in late spring – early summer grow faster because of longer exposure to warm summer temperature, which allows them to be transported towards the coast by the strong onshore flows in winter and reduces their natural mortality. Preliminary source–sink relationship indicates that the population was well mixed off the coast, with higher likelihood of settlement success from hatching sites in the north, mostly due to higher surface temperature. Weighted with the breeding stock distribution, the area between 27.5°S and 29.5°S, including the Abrolhos Islands, is the most important hatching area to the success of settlement.

scholarly journals Stocking density and shelter type for the optimal growth and survival of western rock lobster Panulirus cygnus (George)

Aquaculture ◽  
2006 ◽  
Vol 260 (1-4) ◽  
pp. 114-127 ◽  
Author(s):  
Danielle Johnston ◽  
Roy Melville-Smith ◽  
Blair Hendriks ◽  
Greg B. Maguire ◽  
Bruce Phillips
Keyword(s):  
Stocking Density ◽  
Optimal Growth ◽  
Rock Lobster ◽  
Growth And Survival ◽  
Panulirus Cygnus

Seasonal variation in the long-term warming trend in water temperature off the Western Australian coast

2009 ◽  
Vol 60 (2) ◽  
pp. 129 ◽  
Author(s):  
N. Caputi ◽  
S. de Lestang ◽  
M. Feng ◽  
A. Pearce
Keyword(s):  
Seasonal Variation ◽  
Indian Ocean ◽  
Water Temperature ◽  
West Coast ◽  
Climate Models ◽  
Warming Trend ◽  
Temperature Cycle ◽  
Rock Lobster ◽  
Leeuwin Current ◽  
The Indian Ocean

Previous studies have demonstrated that one area of greatest increase in surface sea temperatures (SST) (0.02°C per year) in the Indian Ocean over the last 50 years occurs off the lower west coast of Australia, an area dominated by the Leeuwin Current. The present paper examines water temperature trends at several coastal sites since the early 1970s: two rock lobster puerulus monitoring sites in shallow water (<5 m); four sites from a monitoring program onboard rock lobster vessels that provide bottom water temperature (<36 m); and an environmental monitoring site at Rottnest (0–50 m depth). Two global SST datasets are also examined. These data show that there was a strong seasonal variation in the historic increases in temperature off the lower west coast of Australia, with most of the increases (0.02–0.035°C per year) only focussed on 4–6 months over the austral autumn–winter with little or no increase (<0.01°C per year) apparent in the austral spring–summer period. These increases are also apparent after taking into account the interannual variation in the strength of the Leeuwin Current. The warming trend results in a change to the seasonal temperature cycle over the decades, with a delay in the peak in the temperature cycle during autumn between the 1950s and 2000s of ~10–20 days. A delay in the timing of the minimum temperature is also apparent at Rottnest from August–September to October. This seasonal variation in water temperature increases and its effect on the annual temperature cycle should be examined in climate models because it provides the potential to better understand the specific processes through which climate change and global warming are affecting this region of the Indian Ocean. It also provides an opportunity to further test the climate models to see whether this aspect is predicted in the future projections of how increases will be manifest. Any seasonal variation in water temperature increase has important implications for fisheries and the marine ecosystem because it may affect many aspects of the annual life cycle such as timing of growth, moulting, mating, spawning and recruitment, which have to be taken into account in the stock assessment and management of fisheries.

Spatial and temporal variation in lipid and fatty acid profiles of western rock lobster pueruli at first settlement: biochemical indicators of diet and nutritional status

2009 ◽  
Vol 60 (8) ◽  
pp. 810 ◽  
Author(s):  
A. J. Limbourn ◽  
R. C. Babcock ◽  
D. J. Johnston ◽  
P. D. Nichols ◽  
B. Knott
Keyword(s):  
Fatty Acid ◽  
Nutritional Status ◽  
Spatial And Temporal Variation ◽  
Lipid Levels ◽  
Rock Lobster ◽  
Important Species ◽  
Fa Composition ◽  
Lipid Fatty Acid ◽  
Spatial And Seasonal Variation ◽  
Panulirus Cygnus

Rock lobster species are found worldwide and have a life history that includes development through a planktonic phyllosoma followed by a nektonic non-feeding puerulus that relies on stored energy during recruitment into near-shore habitats. Recruitment to adult populations of western rock lobster (Panulirus cygnus) is highly variable and is likely to be strongly influenced by shelf width and oceanic conditions affecting cross-shelf transport and nutrition. Since the nutritional status of newly settled pueruli will reflect the phyllosoma feeding environment and distance swum, we studied levels of lipid, fatty acid (FA) and protein of 422 pueruli and 79 first instar juveniles from four Western Australian locations. Lipid levels generally were inversely related to shelf width but were variable, suggesting pueruli may travel complex trajectories to coastal settlement. Lipid and FA composition of pueruli were consistent with spatial and seasonal variation in Leeuwin Current and coastal productivity regimes. Seasonal differences in FA composition occurred regardless of the year of settlement. Pueruli had lower lipid levels during ENSO years, when recruitment tends to be lower also. Measures of puerulus nutritional status appear to provide valuable insights into the processes underpinning recruitment in Panulirus cygnus and other commercially and ecologically important species.

Genetic structure of the western rock lobster, Panulirus cygnus, with the benefit of hindsight

1996 ◽  
Vol 47 (7) ◽  
pp. 889 ◽  
Author(s):  
AP Thompson ◽  
JR Hanley ◽  
MS Johnson
Keyword(s):  
Genetic Structure ◽  
Western Australia ◽  
Allozyme Variation ◽  
Genetic Homogeneity ◽  
Latitudinal Variation ◽  
Rock Lobster ◽  
Polymorphic Loci ◽  
Allelic Frequencies ◽  
Genetic Subdivision ◽  
Panulirus Cygnus

Allozyme variation was used to investigate the genetic structure of the western rock lobster, Panulirus cygnus, along the coast of Western Australia. The study involved genetic surveys in 1980 and 1994. The first survey showed strong suggestions of latitudinal variation at two polymorphic loci, EST and GPI, but these suggestions were statistically suspect. With the benefit of hindsight gained from 1980, the 1994 survey was designed to examine more directly the suggestion of latitudinal genetic subdivision in this species. No evidence of genetic subdivision was found at either the EST or the GPI locus. In addition, the average FST value over nine polymorphic loci was a very low 0.0002. The evidence is consistent with current interpretations that P. cygnus is a single, panmictic population. In contrast with this spatial genetic homogeneity, however, there were significant changes in allelic frequencies at the GPI locus between 1980 and 1994, indicating genetic differences among cohorts.

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