Population modelling of Tasmanian rock lobster, Jasus edwardsii, resources

1997 ◽  
Vol 48 (8) ◽  
pp. 967 ◽  
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.

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

2001 ◽  
Vol 52 (8) ◽  
pp. 1495 ◽  
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.

Relationship between settlement of southern rock lobster pueruli, Jasus edwardsii, and recruitment to the fishery in Tasmania, Australia

2001 ◽  
Vol 52 (8) ◽  
pp. 1271 ◽  
Author(s):  
C. Gardner ◽  
S. D. Frusher ◽  
R. B. Kennedy ◽  
A. Cawthorn
Keyword(s):  
Interannual Variation ◽  
Stock Assessment ◽  
Catch Rate ◽  
Assessment Model ◽  
Rock Lobster ◽  
Commercial Catch ◽  
Jasus Edwardsii ◽  
Catch Rates ◽  
Additional Support ◽  
Northeast Coast

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.

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

2008 ◽  
Vol 88 (3) ◽  
pp. 583-589 ◽  
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.

scholarly journals Fewer eggs from larger size limits: counterintuitive outcomes in a spatially heterogeneous fishery

2014 ◽  
Vol 72 (suppl_1) ◽  
pp. i252-i259 ◽  
Author(s):  
Caleb Gardner ◽  
Klaas Hartmann ◽  
André E. Punt ◽  
Eriko Hoshino
Keyword(s):  
Marine Protected Areas ◽  
Egg Production ◽  
Slow Growth ◽  
Minimum Length ◽  
Bioeconomic Model ◽  
Rock Lobster ◽  
Total Allowable Catch ◽  
Jasus Edwardsii ◽  
Negative Impacts ◽  
Size Limits

Abstract The legal minimum length (LML) of female Southern Rock Lobster (Jasus edwardsii) was reduced in the Tasmanian fishery in 1966 for higher sustainable catches. Originally, the LML was to be reduced in slow growth southern areas only; however, the change was implemented across the entire fishery due to lobbying by commercial fishers. The lower LML has been controversial ever since, including during recent years when low recruitment resulted in a lower total allowable catch (TAC). Fishers argued that this could have been prevented with a higher female LML across the jurisdiction. A length- and sex-based bioeconomic model was used to examine probable outcomes of the larger statewide LML. This model showed that management of egg production would be poorly served by raising the statewide LML because of spatial patterns in the stock and fishery. Catch would be displaced from areas where egg production was already high and into the most depleted areas thus reducing production in areas of greatest concern. Spatial variation in biological parameters can have a profound effect on outcomes of management perceived to be conservative, possibly leading to negative impacts. This risk exists wherever catch is displaced, such as with Marine Protected Areas, spatial TACs and gear restrictions.

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

2014 ◽  
Vol 23 (4) ◽  
pp. 362-374 ◽  
Author(s):  
John Feenstra ◽  
Richard McGarvey ◽  
Adrian Linnane ◽  
André E. Punt ◽  
Nigel Bean
Keyword(s):  
Environmental Influences ◽  
Rock Lobster ◽  
Commercial Catch ◽  
Jasus Edwardsii ◽  
Catch Rates

scholarly journals A multi‐stock, length‐based assessment model for New Zealand rock lobster(Jasus Edwardsii)

2009 ◽  
Vol 43 (1) ◽  
pp. 355-371 ◽  
Author(s):  
Vivian Haist ◽  
Paul A. Breen ◽  
Paul J. Starr
Keyword(s):  
New Zealand ◽  
Assessment Model ◽  
Rock Lobster ◽  
Jasus Edwardsii

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

2002 ◽  
Vol 53 (8) ◽  
pp. 1143 ◽  
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.

Decrease in size at maturity of female American lobsters Homarus americanus (H. Milne Edwards, 1837) (Decapoda: Astacidea: Nephropidae) over a 50-year period in Maine, USA

2019 ◽  
Vol 39 (4) ◽  
pp. 509-515 ◽  
Author(s):  
Jesica D Waller ◽  
Kathleen M Reardon ◽  
Sarah E Caron ◽  
Henry M Masters ◽  
Erin L Summers ◽  
...  
Keyword(s):  
Egg Production ◽  
Gulf Of Maine ◽  
Stock Assessment ◽  
Homarus Americanus ◽  
Assessment Method ◽  
Cement Gland ◽  
Assessment Model ◽  
Size At Maturity ◽  
Significant Difference ◽  
Bank Stock

ABSTRACTThe size at which female American lobsters Homarus americanus (H. Milne Edwards, 1837) reach maturity was determined for females collected from inshore (< 3 nautical miles, or 5.5 km) Boothbay Harbor (BBH), Maine, USA in 2018. A total of 272 females were collected during a three-week period in the spring and each female was assigned a maturity status (immature or mature) based on ovarian staging. These determinations were then compared to two similar female-maturity studies undertaken in BBH by the Maine Department of Marine Resources over the last 50 years. The comparison revealed that the length at which 50% of females reach maturity has decreased by 5 mm over the last 25 years and a significant difference between maturity ogives generated over time in BBH. Cement-gland stage was also recorded for all females and further analysis revealed no significant difference between maturity ogives generated using ovarian and cement-gland staging. Results indicate that cement-gland staging is an effective maturity assessment method in female lobsters from this region. Because there is a well-documented relationship between temperature and size at maturity in crustaceans, we also examined changes in sea-surface temperature during this period in BBH. We found that the region has warmed significantly over this period of time with extreme high temperatures occurring more frequently during the last 25 years. Our results can be used to update key parameters in the stock-assessment model related to growth and egg production in the Gulf of Maine/George’s Bank stock. These findings can also be used to inform future management decisions related to the carapace length of harvested lobsters and the preservation of mature females.

A Bayesian hierarchical formulation of the De Lury stock assessment model for abundance estimation of Falkland Islands' squid (Loligo gahi)

2004 ◽  
Vol 61 (6) ◽  
pp. 1048-1059 ◽  
Author(s):  
Murdoch K McAllister ◽  
Simeon L Hill ◽  
David J Agnew ◽  
Geoffrey P Kirkwood ◽  
John R Beddington
Keyword(s):  
Sampling Error ◽  
Stock Assessment ◽  
Assessment Model ◽  
Abundance Estimation ◽  
Falkland Islands ◽  
Parameter Estimates ◽  
Bayesian Hierarchical ◽  
Stock Assessments ◽  
Catch Rates ◽  
Using Data

In stock assessments of short-lived species, De Lury depletion models are commonly applied in which commercial catches and changing catch rates are used to estimate resource abundance. These methods are applied within fishing seasons to decide when to close the fishery and can be reliable if the data show a distinct decline in response to the catch removals. However, this is not always the case, particularly when sampling error variation masks trends in abundance. This paper presents a Bayesian hierarchical formulation of the De Lury model in which data from previous years are combined hierarchically in the same stock assessment model to improve parameter estimation for future stock assessments. The improved precision in parameter estimates is demonstrated using data for the Falkland Islands' Loligo gahi squid fishery.

scholarly journals Applying a two-stage Bayesian dynamic model to a short lived species, the anchovy in the Aegean Sea (Eastern Mediterranean). Comparison with an Integrated Catch at Age stock assessment model.

2014 ◽  
Vol 15 (2) ◽  
pp. 350 ◽  
Author(s):  
M. GIANNOULAKI ◽  
L. IBAIBARRIAGA ◽  
K. ANTONAKAKIS ◽  
A. URIARTE ◽  
A. MACHIAS ◽  
...  
Keyword(s):  
Egg Production ◽  
Missing Values ◽  
Stock Assessment ◽  
Eastern Mediterranean ◽  
Aegean Sea ◽  
Production Method ◽  
Assessment Model ◽  
Two Stage ◽  
Commercial Catch ◽  
The North

Two different stock assessment models were applied to the North Aegean Sea anchovy stock (Eastern Mediterranean Sea): an Integrated Catch at age Analysis and a Bayesian two-stage biomass based model. Commercial catch data over the period 2000-2008 as well as acoustics and Daily Egg Production Method estimates over the period 2003-2008 were used. Both models results were consistent, indicating that anchovy stock is exploited sustainably in relation to an exploitation rate reference point. Further, the stock biomass appears stable or increasing. However, the limitations in age-composition data, potential problems related to misinterpretation of age readings along with the existence of missing values in the survey data seem to favour the two-stage biomass method, which is based on a simplified age structure.  

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