Environmental influences on daily commercial catch rates of South Australia's southern rock lobster (Jasus edwardsii)

Puerulus catches on artificial collectors were measured monthly at four sites around Tasmania from 1991 to April 2000, with the aim of predicting future changes in recruitment to the fishery. Support for the potential of catch-rate prediction in Tasmania was provided at the two sites that have overlap of several years between indices of puerulus settlement and indices of the abundance of recruits to the fishery. At Bicheno, on the northeast coast, correlations between annual puerulus index and commercial catch rates were highly significant, with a lag of 5 years (P< 0.01). Similar interannual trends in puerulus index and estimates from a stock-assessment model of the biomass of recruits to the fishery provided additional support for a link with puerulus index. A 5-fold interannual variation in puerulus index detected at Bicheno, with a peak in 1995, was preceded by 3 years of relatively low puerulus catch. The peak in puerulus index appears to lead to an increase in the abundance of sublegal males in research sampling 3 years later. Correlation between annual measures of puerulus index and catch rate also appeared significant at King Island (P= 0.06) although data at this site had less contrast.

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How reliable are the abundance indices derived from commercial catch–effort standardization?

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f09-070 ◽

2009 ◽

Vol 66 (7) ◽

pp. 1169-1178 ◽

Cited By ~ 33

Author(s):

Yimin Ye ◽

Darren Dennis

Keyword(s):

Generalized Linear Model ◽

Observation Error ◽

Potential Bias ◽

Catch Per Unit Effort ◽

Rock Lobster ◽

Commercial Catch ◽

Abundance Indices ◽

Catch Rates ◽

Power Component ◽

Stock Abundance

Commercial catch-per-unit-effort (CPUE) data are often standardized to construct indices of stock abundance. The value of such standardization lies in the improvement in the proportionality between the derived index and true abundance. Using the Torres Strait rock lobster ( Panulirus ornatus ) fishery in Australia as an example, we first standardized the commercial CPUE data using a generalized linear model (GLM) and then fitted observation error models to the resulting abundance indices and independent abundance data (as estimated by research diver surveys) to examine the proportionality. While the GLM standardization greatly improved proportionality in comparison with the nonstandardized commercial catch rates, it could produce biased results if the model did not explicitly incorporate variables that had caused changes in fishing efficiency. As most catch–effort standardizations do not model the fishing power component simultaneously, this result may serve as a warning to the potential bias in stock abundance indices extracted from GLMs that are underfitted.

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The orientation and migratory dynamics of the western rock lobster, Panulirus cygnus, in Western Australia

ICES Journal of Marine Science ◽

10.1093/icesjms/fst205 ◽

2014 ◽

Vol 71 (5) ◽

pp. 1052-1063 ◽

Cited By ~ 4

Author(s):

Simon de Lestang

Keyword(s):

Large Scale ◽

Economic Benefits ◽

Rock Lobster ◽

Commercial Catch ◽

Breeding Grounds ◽

Mean Size ◽

Catch Rates ◽

Panulirus Cygnus ◽

The Impact ◽

Oceanic Currents

Abstract Large-scale migrations are known to occur in numerous species, and in the case of the Western Rock Lobster, Panulirus cygnus, result in juveniles moving from nursery areas into deeper offshore breeding grounds. In 2008 the Western Rock Lobster fishery reduced harvest rates to increase legal and spawning biomass throughout the fishery, which also allowed greater numbers of lobsters to migrate. Increased lobster migration could potentially reduce biomass in some areas, thus adversely impacting commercial catch rates. Over 20 000 tag–recaptured lobsters were analysed to determine the dynamics underlying migration in this species and to assess the impact reduced harvest rates may have had on catches. This study showed that P. cygnus migration was associated with body size and water depth, and that magnetism and oceanic currents appear to be the most likely guideposts used for orientation. Size at migration varied in a constant fashion along the coast, being larger towards the southern end of the fishery and smallest at the offshore Abrolhos Islands. During the migration period, up to 50% of lobsters at their mean size of migration moved from coastal areas out towards deeper waters (>40 m), whereas <15% of those in deeper water at the same size moved significant distances northward. This behaviour appears to be contranatant, counteracting the downstream redistribution of larvae after their 9–11 month larval life. Reduced harvest rates and catches being focussed onto higher valued sedentary lobsters have allowed more lobsters to migrate. However, the numbers moving between management areas are relatively small, with the biological and economic benefits of fishing at a reduced exploitation rate outweighing losses to catches.

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Contrasting fecundity, size at maturity and reproductive potential of southern rock lobster Jasus edwardsii in two South Australian fishing regions

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315408001021 ◽

2008 ◽

Vol 88 (3) ◽

pp. 583-589 ◽

Cited By ~ 17

Author(s):

A.J. Linnane ◽

S.S. Penny ◽

T.M. Ward

Keyword(s):

Egg Production ◽

Spatial Scales ◽

Reproductive Potential ◽

South Australia ◽

Egg Mass ◽

Rock Lobster ◽

Commercial Catch ◽

Southern Zone ◽

Significant Difference ◽

Jasus Edwardsii

The annual commercial catch from the Southern Zone of the South Australian rock lobster (Jasus edwardsii) fishery is ~1900 tonnes, representing ~50% of total landings from south-east Australia. A single minimum legal size (MLS) of 98.5 mm carapace length (CL) exists across the entire zone. Fecundity (F), size at onset of maturity (SOM) and relative reproductive potential (RRP) of female rock lobsters were investigated in two major fishing regions, i.e. the North Southern Zone (NSZ) and South Southern Zone (SSZ) with a view to providing a basis for future fine-scale spatial management of the resource. F ranged from 45,292 to 466,800 eggs per female and increased proportionally with CL according to the relationship: F = 0.0584 × CL3.1642. F was significantly higher in the NSZ compared to the SSZ but was attributed to differences in lobster size between regions. There was no significant difference in the number of eggs · g−1 of egg mass between areas. SOM, estimated as the size at which 50% of females reached sexual maturity (L50) was higher in the NSZ (104.1 mm CL) compared to SSZ (92.3 mm CL). Approximately 20% of lobsters above the MLS in the commercial catch in the NSZ were under the L50 estimate. RRP, as a measure of egg production, was calculated for each size-class from the product of F, SOM and population length–frequency. The modal RRP size-classes in the NSZ were 117.5–122.5 mm CL, while in the SSZ it was 97.5–102.5 mm CL. Only 6% of RRP was contributed by female rock lobsters below the MLS in the NSZ, compared to 34% in the SSZ. Regional differences in SOM and RRP in the Southern Zone of South Australia suggest that different MLSs may be beneficial, particularly if the fishery is to be effectively managed at finer spatial scales.

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Catchability of the southern rock lobster Jasus edwardsii. I. Effects of sex, season and catch history

Marine and Freshwater Research ◽

10.1071/mf01243 ◽

2002 ◽

Vol 53 (8) ◽

pp. 1143 ◽

Cited By ~ 20

Author(s):

P. E. Ziegler ◽

S. D. Frusher ◽

C. R. Johnson ◽

C. Gardner

Keyword(s):

Carapace Length ◽

Early Summer ◽

Rock Lobster ◽

Marked Contrast ◽

Density Estimates ◽

Male And Female ◽

Jasus Edwardsii ◽

Males And Females ◽

Catch Rates ◽

Trap Catches

Seasonal variation in catchability of the southern rock lobster Jasus edwardsii, was estimated in a scientific reserve in south-east Tasmania by comparing estimates of lobster density based on direct visual observations underwater with concomitant estimates from trapping surveys. Underwater density estimates of undersized and legal-sized male and female lobsters >80 mm carapace length, did not change significantly over the 14-month study period, with the exception of undersized males (≤110 mm carapace length). Sex ratios remained constant at approximately 1 : 1. In marked contrast, catch rates of males and females and the sex ratio of trapped lobsters varied strongly with season, implying that catchability varies seasonally and with sex. Catchability of males and females was highest in early summer and lowest in winter. Impact of capture on subsequent catchability appeared to be weak, since the ratios of tagged animals in the population observed underwater generally reflected recapture rates of tagged animals in trap catches. Recapture rates increased with size and were higher for medium-sized and large males than for similar-sized females. However, for each particular sex-size group, recapture rates remained relatively constant throughout the study period.

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Locomotor Activity in the Western Rock Lobster, Panulirus longipes cygnus

Marine and Freshwater Research ◽

10.1071/mf9780169 ◽

1978 ◽

Vol 29 (2) ◽

pp. 169 ◽

Cited By ~ 23

Author(s):

GR Morgan

Keyword(s):

Locomotor Activity ◽

Individual Variation ◽

Daily Variation ◽

High Water ◽

Peak Activity ◽

High Water Temperature ◽

Rock Lobster ◽

Commercial Catch ◽

Catch Rates ◽

Increasing Temperature

Daily locomotor activity rhythms in individual P. longipes cygnus were shown to be of a non- crepuscular nature with peak activity occurring immediately after the onset of darkness. Mean activity of animals in an intermoult stage increased with increasing temperature between 17 and 25�C but then declined, whilst for animals in a premoult stage there was no significant trend with temperature, activity rates remaining at a low level. Individual variation of response of intermoult animals also increased with temperature and is suggested as a contributing factor to high daily variation in commercial catch rates during months of high water temperature.

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Size-structured population modelling and risk assessment of the Victorian southern rock lobster, Jasus edwardsii, fishery

Marine and Freshwater Research ◽

10.1071/mf01050 ◽

2001 ◽

Vol 52 (8) ◽

pp. 1495 ◽

Cited By ~ 27

Author(s):

David Hobday ◽

André E. Punt

Keyword(s):

Egg Production ◽

Stock Assessment ◽

Reference Points ◽

Assessment Model ◽

Data Series ◽

Population Modelling ◽

Rock Lobster ◽

Southeastern Australia ◽

Jasus Edwardsii ◽

Catch Rates

Current annual landings of southern rock lobster, Jasus edwardsii, from southeastern Australia are around 5000 tonnes valued at A$140 million. The Victorian component of this catch during the 1998-99 fishing season was 550 t, valued at A$18 million. During the past 20 years catch rates have declined from 0.8 kg per pot lift to 0.6 and 0.3 kg per pot lift in the western and eastern management zones respectively. The fishery has been managed with input controls during this period, but at the time of writing, the direction of future management is not clear. A size-structured model was developed to assess risk associated with both effort (input) and catch (output) controlled harvest strategies in each zone. The stock-assessment model was fitted to historical catch data (in weight and by number) from 1951, catch rates, and the length-frequency by sex. The uncertainty associated with the estimates of exploitable biomass and egg production was assessed according to Bayesian methods. The output of the assessment formed the basis for projections intended to determine the risk associated with different future levels of effort and catch. Reference points based on estimated biomass and egg production relative to the start of the data series in 1951 were considered.

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Population modelling of Tasmanian rock lobster, Jasus edwardsii, resources

Marine and Freshwater Research ◽

10.1071/mf97070 ◽

1997 ◽

Vol 48 (8) ◽

pp. 967 ◽

Cited By ~ 95

Author(s):

André E. Punt ◽

Robert B. Kennedy

Keyword(s):

Growth Rate ◽

Egg Production ◽

Stock Assessment ◽

Assessment Model ◽

High Yield ◽

Population Modelling ◽

Rock Lobster ◽

Jasus Edwardsii ◽

Northern Regions ◽

Catch Rates

From 1980 to 1995, annual catch rates of southern rock lobster (Jasus edwardsii) in Tasmanian waters declined from 1·6 to 0·9 kg per pot lift. From March 1998, the Tasmanian government intends to base management of this fishery on output controls using individual transferable catch quotas. This has necessitated the development of a stock assessment model that can be used to evaluate the relative merits of a variety of alternative catch limits in terms of the trade-off between protecting the rock lobster resource and achieving a high yield. Each of eight regions around Tasmania is assessed separately because of spatial heterogeneity between regions in lobster growth, size at maturity and catch rates. The stock assessment model is size-structured and is fitted to catch, effort and length–frequency data as well as to estimates of exploitation rate from experimental data. A Bayesian estimation framework is employed to estimate the quantities needed for risk analysis. Egg production differs markedly among the eight regions: from as low as 6% of the unexploited equilibrium level in the northern regions, where the growth rate is fast, to more than 80% in the south-west, where the growth rate is slowest.

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