scholarly journals Improving catch prediction for tiger prawns in the Australian northern prawn fishery

2014 ◽  
Vol 72 (1) ◽  
pp. 117-129 ◽  
Author(s):  
Roy A. Deng ◽  
André E. Punt ◽  
Catherine M. Dichmont ◽  
Rik C. Buckworth ◽  
Charis Y. Burridge
Keyword(s):  
Population Model ◽  
Frequency Data ◽  
Length Frequency ◽  
Structured Population Model ◽  
Structured Population ◽  
Penaeus Semisulcatus ◽  
Tiger Prawn ◽  
Length Frequency Data ◽  
Northern Prawn Fishery ◽  
Quantities Of Interest

Abstract Population models form the basis for the assessments of species in the tiger prawn component of Australia's northern prawn fishery. Penaeus semisulcatus and P. esculentus are assessed using a size-structured population model. These assessments form the basis for a control rule which predicts future total allowable catches (TACs) for P. semisulcatus and P. esculentus so that the discounted profit from the fishery is maximized. However, there are concerns with this approach: (i) the TAC predictions have consistently overpredicted actual catches and (ii) the assessment for one of the species exhibits a retrospective pattern. A series of analyses was conducted to explore the causes of these observations. Results indicate that catch, effort, and recruitment prediction can be improved substantially by changing the assumed selectivity pattern for one of the surveys, changing how the length frequency data are assembled from the raw data collected, changing the constraints on the minimum amount of effort by target fleet, modifying how the distribution of effort by week is forecasted, and dropping the length frequency data from the most recent recruitment survey. More generally, the analyses illustrate how retrospective analysis can be used to improve how assessments and projections are undertaken when the quantities of interest are known retrospectively.

Population ecology of the grooved tiger prawn, Penaeus semisulcatus, in the north-western Gulf of Carpentaria, Australia: growth, movement, age structure and infestation by the bopyrid parasite Epipenaeon ingens

1991 ◽  
Vol 42 (4) ◽  
pp. 349 ◽  
Author(s):  
IF Somers ◽  
GP Kirkwood
Keyword(s):  
Sex Ratio ◽  
Age Structure ◽  
Frequency Data ◽  
Length Frequency ◽  
The North ◽  
Penaeus Semisulcatus ◽  
Growth Movement ◽  
North Western ◽  
Length Frequency Data ◽  
Trawl Surveys

Concurrent trawl surveys and tag-recapture studies carried out in the north-western Gulf of Carpentaria between August 1983 and March 1985 provided a detailed description of the growth, movement and age structure of the population of grooved tiger prawns, Penaeus semisulcatus. Growth curves based on the tag-recapture data were used to interpret the length-frequency data collected from the trawl surveys and to determine the number of year classes present. The length-frequency data pertaining to the 1984 year class provided the basis for an estimate of the longevity of the species and a description of the offshore movement patterns. The effect of infestation by the bopyrid parasite Epipenaeon ingens on growth and movement was also examined. Individuals of P. semisulcatus may live for about 2 years, but in the north-western Gulf of Carpentaria very few survive beyond 18 months. Subadults recruit to the offshore fishing grounds during summer and autumn (November-March) at sizes between 20 and 25 mm carapace length (CL) (between 4 and 6 months). By 18 months of age, males reach a size of about 39 mm CL and females about 50 mm CL. The growth rates of both sexes are affected by the presence of E. ingens: males grow faster and larger, the females slower and smaller, with both sexes attaining a size of around 43 mm CL by 18 months of age. The recruiting year class continues to disperse offshore during autumn (from March to May) in such a way that by winter (June and July), although highest abundance is in depths of 35-40 m, the population extends well beyond the commercial fishery into depths greater than 50 m. Although prawns infested with E. ingens show a similar offshore movement, they do not venture beyond depths greater than about 30 m. The sex ratio within the year class remains at around 1 : 1 from the time of recruitment to about 1 year of age. Thereafter, the percentage of females declines steadily; by about 18 months of age very few prawns remain in the population, and of these only about 25% are female. In contrast, the sex ratio for prawns infested with E. ingens remains at about 1 : 1 throughout.

Stock-recruitment relationships of the tiger prawns (Penaeus esculentus and Penaeus semisulcatus) in the Australian northern prawn fishery

1996 ◽  
Vol 47 (1) ◽  
pp. 87 ◽  
Author(s):  
YG Wang ◽  
D Die
Keyword(s):  
Population Model ◽  
Fishing Effort ◽  
Maximum Sustainable Yield ◽  
Production Model ◽  
Commercial Catch ◽  
Penaeus Semisulcatus ◽  
Spawning Stock ◽  
Tiger Prawn ◽  
Stock Recruitment ◽  
Northern Prawn Fishery

This paper investigates the stock-recruitment and equilibrium yield dynamics for the two species of tiger prawns (Penaeus esculentus and Penaeus semisulcatus) in Australia's most productive prawn fishery: the Northern Prawn Fishery. Commercial trawl logbooks for 1970-93 and research surveys are used to develop population models for these prawns. A population model that incorporates continuous recruitment is developed. Annual spawning stock and recruitment indices are then estimated from the population model. Spawning stock indices represent the abundance of female prawns that are likely to spawn; recruitment indices represent the abundance of all prawns less than a certain size. The relationships between spawning stock and subsequent recruitment (SRR), between recruitment and subsequent spawning stock (RSR), and between recruitment and commercial catch were estimated through maximum-likelihood models that incorporated autoregressive terms. Yield as a function of fishing effort was estimated by constraining to equilibrium the SRR and RSR. The resulting production model was then used to determine maximum sustainable yield (MSY) and its corresponding fishing effort (fMSY). Long-term yield estimates for the two tiger prawn species range between 3700 and 5300 t. The fishing effort at present is close to the level that should produce MSY for both species of tiger prawns. However, current landings, recruitment and spawning stock are below the equilibrium values predicted by the models. This may be because of uncertainty in the spawning stock-recruitment relationships, a change in carrying capacity, biased estimates of fishing effort, unreliable catch statistics, or simplistic assumptions about stock structure. Although our predictions of tiger prawn yields are uncertain, management will soon have to consider new measures to counteract the effects of future increases in fishing effort.

Integrating size-structured assessment and bioeconomic management advice in Australia's northern prawn fishery

2010 ◽  
Vol 67 (8) ◽  
pp. 1785-1801 ◽  
Author(s):  
André E. Punt ◽  
Roy A. Deng ◽  
Catherine M. Dichmont ◽  
Tom Kompas ◽  
William N. Venables ◽  
...  
Keyword(s):  
Population Model ◽  
Net Present Value ◽  
Fishing Effort ◽  
Bioeconomic Model ◽  
Short Term ◽  
Time Step ◽  
Structured Population Model ◽  
Penaeus Semisulcatus ◽  
Management Advice ◽  
Northern Prawn Fishery

Abstract Punt, A. E., Deng, R. A., Dichmont, C. M., Kompas, T., Venables, W. N., Zhou, S., Pascoe, S., Hutton, T., Kenyon, R., van der Velde, T., and Kienzle, M. 2010. Integrating size-structured assessment and bioeconomic management advice in Australia's northern prawn fishery. – ICES Journal of Marine Science, 67: 1785–1801. Three species in Australia's northern prawn fishery (Penaeus semisulcatus, P. esculentus, and Metapenaeus endeavouri) are assessed using a size-structured population model that operates on a weekly time-step. The parameters of this multispecies population model are estimated using data on catches, catch rates, length frequency data from surveys and the fishery, and tag release–recapture data. The model allows for the technical interaction among the three species. The results from the multispecies stock assessment are used to calculate the time-series of catches and levels of fishing effort that maximize net present value. The bioeconomic model takes into account costs which are proportional to catches and those which are proportional to fishing effort, as well as fixed costs. The sensitivity of the results is examined by changing the assumptions regarding the values for the economic parameters of the bioeconomic model as well as those on which the assessment are based. The results suggest that fishing effort needs to be reduced in the short term to achieve economic goals, although most stocks are estimated currently to be above the stock size corresponding to maximum sustainable yield. Short-term catches and effort levels are sensitive to model assumptions, and in particular, to trends in prices and costs.

scholarly journals POPULATION DYNAMICS OF MALAYAN LEAF FISH (Pristolepisgrooti Blkr.) IN RANAU LAKE, SOUTH SUMATRA

2018 ◽  
Vol 24 (2) ◽  
pp. 125
Author(s):  
Sevi Sawetri ◽  
Subagdja Subagdja ◽  
Dina Muthmainnah
Keyword(s):  
Mortality Rate ◽  
Growth Parameters ◽  
Total Mortality ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Frequency Data ◽  
Length Frequency ◽  
Lake Ecosystems ◽  
Exploitation Rate ◽  
Length Frequency Data

The Malayan leaf fish or locally named as kepor (Pristolepis grooti) is one of important biotic components in Ranau Lake ecosystems. This study aimed to estimate population dynamic and exploitation rate of kepor in Ranau Lake, South Sumatera. The population parameters are estimated based on length frequency data which were collected in March to October 2013. Growth parameters and fishing mortality rates were calculated using FiSAT software package. The results showed that kepor’s growth was negative allometric, which tended to gain length faster than weight. Kepor population was dominated (42%) by individual length of 10.0 to 11.0 cm. Predicted length infinity (L) was 17.28 cm with high value of growth rates (K) of 1.4 year-1. The natural mortality rate (M) is 2.57 year-1, the fishing mortality rate (F) is 5.36 year-1 and total mortality rate (Z) is 7.93 year-1. The exploitation rate of Malayan leaf fish in Ranau Lake (E = 0.68 year-1) has passed the optimum score.  

scholarly journals Investigation and Development of Post-Season Modelling of Arrow Squid in the Snares and Auckland Islands

2021 ◽  
Author(s):  
◽  
Vidette Louise McGregor
Keyword(s):  
Automatic Differentiation ◽  
Integrated Model ◽  
Current Data ◽  
Management Approach ◽  
Frequency Data ◽  
Catch Per Unit Effort ◽  
Length Frequency ◽  
Model Builder ◽  
Set Up ◽  
Length Frequency Data

<p>Squid fisheries require a different management approach to most fish species which are much longer living. Most squid live for around one year, spawn and then die. The result of this is an entirely new stock each year with little or no relationship of stock sizes between the years. Hence, it is difficult to set appropriate catch limits prior to the season. Currently, there is nothing set up for modelling the New Zealand squid fishery in-season or post-season. In-season management would allow for adjustments of catch limits during a season. Post-season management would provide information on how much the stock was exploited during a season (described as the escapement). I have produced an integrated model using ADMB (Automatic Differentiation Model Builder) (Fournier et al., 2011) which models length frequency data, CPUE (Catch Per Unit Effort) indices and catch weights from a season. It calculates escapement which indicates how much the fishery is currently being exploited. In running the model against data from four area and year combinations, I found the escapement calculation to be stable. The results suggest this modelling approach could be used with the current data collected for post-season modelling of the fishery. I am less confident about in-season modelling with the current data collected. The integrated model fits quite poorly to the CPUE data, suggesting some discrepancy either between the data or the assumptions made of them. Sampling from a greater number of tows is recommended to improve the length frequency data and this may also improve the ability of the model to fit both to these and the CPUE.</p>

scholarly journals Investigation and Development of Post-Season Modelling of Arrow Squid in the Snares and Auckland Islands

2021 ◽  
Author(s):  
◽  
Vidette Louise McGregor
Keyword(s):  
Automatic Differentiation ◽  
Integrated Model ◽  
Current Data ◽  
Management Approach ◽  
Frequency Data ◽  
Catch Per Unit Effort ◽  
Length Frequency ◽  
Model Builder ◽  
Set Up ◽  
Length Frequency Data

<p>Squid fisheries require a different management approach to most fish species which are much longer living. Most squid live for around one year, spawn and then die. The result of this is an entirely new stock each year with little or no relationship of stock sizes between the years. Hence, it is difficult to set appropriate catch limits prior to the season. Currently, there is nothing set up for modelling the New Zealand squid fishery in-season or post-season. In-season management would allow for adjustments of catch limits during a season. Post-season management would provide information on how much the stock was exploited during a season (described as the escapement). I have produced an integrated model using ADMB (Automatic Differentiation Model Builder) (Fournier et al., 2011) which models length frequency data, CPUE (Catch Per Unit Effort) indices and catch weights from a season. It calculates escapement which indicates how much the fishery is currently being exploited. In running the model against data from four area and year combinations, I found the escapement calculation to be stable. The results suggest this modelling approach could be used with the current data collected for post-season modelling of the fishery. I am less confident about in-season modelling with the current data collected. The integrated model fits quite poorly to the CPUE data, suggesting some discrepancy either between the data or the assumptions made of them. Sampling from a greater number of tows is recommended to improve the length frequency data and this may also improve the ability of the model to fit both to these and the CPUE.</p>

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