Rik C Buckworth | CSIRO (original) (raw)

Papers by Rik C Buckworth

Journal of Fish Biology, Oct 24, 2016

Multivariate and machine-learning methods were used to develop field identification techniques fo... more Multivariate and machine-learning methods were used to develop field identification techniques for two species of cryptic blacktip shark. From 112 specimens, precaudal vertebrae (PCV) counts and molecular analysis identified 95 Australian blacktip sharks Carcharhinus tilstoni and 17 common blacktip sharks Carcharhinus limbatus. Molecular analysis also revealed 27 of the 112 were C. tilstoni × C. limbatus hybrids, of which 23 had C. tilstoni PCV counts and four had C. limbatus PCV counts. In the absence of further information about hybrid phenotypes, hybrids were assigned as either C. limbatus or C. tilstoni based on PCV counts. Discriminant analysis achieved 80% successful identification, but machine-learning models were better, achieving 100% successful identification, using six key measurements (fork length, caudal-fin peduncle height, interdorsal space, second dorsal-fin height, pelvic-fin length and pelvic-fin midpoint to first dorsal-fin insertion). Furthermore, pelvic-fin markings could be used for identification: C. limbatus has a distinct black mark >3% of the total pelvic-fin area, while C. tilstoni has markings with diffuse edges, or has smaller or no markings. Machine learning and pelvic-fin marking identification methods were field tested achieving 87 and 90% successful identification, respectively. With further refinement, the techniques developed here will form an important part of a multi-faceted approach to identification of C. tilstoni and C. limbatus and have a clear management and conservation application to these commercially important sharks. The methods developed here are broadly applicable and can be used to resolve species identities in many fisheries where cryptic species exist.

G3: Genes, Genomes, Genetics, Apr 1, 2013

Marine Ecology Progress Series, Aug 15, 2013

Marine Ecology Progress Series, 2013

Endangered Species Research, 2013

Glyphis sharks and pristid sawfishes are globally threatened. While some populations still exist ... more Glyphis sharks and pristid sawfishes are globally threatened. While some populations still exist in northern Australia, their distributions are poorly quantified. We used catch records from commercial fisheries and independent surveys to estimate the broad distribution and relative abundances of 2 Glyphis sharks (G. glyphis and G. garricki) and 4 pristid sawfishes (Pristis pristis, P. zijsron, P. clavata and Anoxypristis cuspidata) along the coast, estuaries and river systems of the Northern Territory, Australia. Coarse-scale catch data and records from commercial fishing logbooks that report encounters with Threatened, Endangered and Protected species confirm that small, fragmented populations are distributed across the Northern Territory coastline and suggest limited fishery interactions, although underreporting might occur.

Copyright and disclaimer © 2015 CSIRO To the extent permitted by law, all rights are reserved and... more Copyright and disclaimer © 2015 CSIRO To the extent permitted by law, all rights are reserved and no part of this publication covered by copyright may be reproduced or copied in any form or by any means except with the written permission of CSIRO. Important disclaimer CSIRO advises that the information contained in this publication comprises general statements based on scientific research. The reader is advised and needs to be aware that such information may be incomplete or unable to be used in any specific situation. No reliance or actions must therefore be made on that information without seeking prior expert professional, scientific and technical advice. To the extent permitted by law, CSIRO (including its employees and consultants) excludes all liability to any person for any consequences, including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from using this

Journal of Fish Biology, 2016

Sustainable exploitation of fisheries populations is challenging to achieve when the size of the ... more Sustainable exploitation of fisheries populations is challenging to achieve when the size of the population prior to exploitation and the actual numbers removed over time and across fishing zones are not clearly known. Quantitative fisheries' modeling is able to address this problem, but accurate and reliable model outcomes depend on high quality input data. Much of this information is obtained through the operation of the fishery under consideration, but while this seems appropriate, biases may occur. For example, poorly quantified changes in fishing methods that increase catch rates can erroneously suggest that the overall population size is increasing. Hence, the incorporation of estimates of abundance derived from independent data sources is preferable. We review and evaluate a fisheries-independent method of indexing population size; inferring adult abundance from estimates of the genetic effective size of a population (Ne ). Recent studies of elasmobranch species have shown correspondence between Ne and ecologically determined estimates of the population size (N). Simulation studies have flagged the possibility that the range of Ne /N ratios across species may be more restricted than previously thought, and also show that declines in Ne track declines in the abundance of model fisheries species. These key developments bring this new technology closer to implementation in fisheries science, particularly for data-poor fisheries or species of conservation interest.

ICES Journal of Marine Science: Journal du Conseil, 2015

Developing bioeconomic models of sequential fisheries is complicated when the two (or more) fishe... more Developing bioeconomic models of sequential fisheries is complicated when the two (or more) fisheries overlap temporally. In such cases, each fishery will be affected by the other, so both cannot be properly modelled as separate activities. This has recently become an issue for the Northern Prawn Fishery, in which bioeconomic modelling is used to set management limits. Modelling has focused on the tiger prawn component of the fishery, which mostly occurs in the second half of the year. However, successful management leading to stock recovery has resulted in this fishery now overlapping temporally with the banana prawn fishery, which occurs in the first half of the year. Ideally, an integrated model covering the whole year would be developed, but this is not practical for a number of reasons. In this study, we model the factors driving the level of fishing effort in the banana prawn fishery, which affects, and is affected by, the tiger prawn fishery. As expected, banana prawn fishing effort is driven largely by stock size, fleet size, catch rates, prices, and fuel costs. Effort increases with fleet size, but at a decreasing rate. Further, we find evidence that opportunity cost, namely the ability to fish in the tiger prawn fishery and the price of tiger prawns, also affects the level of effort in the banana prawn fishery.

Marine Policy, 2015

A holistic approach to stock structure studies utilises multiple different techniques on the same... more A holistic approach to stock structure studies utilises multiple different techniques on the same individuals sampled from selected populations and combines results across spatial and temporal scales to produce a weight of evidence conclusion. It is the most powerful and reliable source of information to use in formulating resource management and monitoring plans. Few examples of the use of a holistic approach in stock structure studies exist, although more recently this is changing. Using such an approach makes integration of results from each technique challenging. An integrated stock definition (ISD) approach for holistic stock structure studies was developed in this study to aid in the appropriate interpretation of stock structure results to guide the determination of fishery management units. The ISD approach is applied herein to a study of the northern Australian endemic grey mackerel, Scomberomorus semifasciatus (Scombridae). Analyses of genetic (mitochondrial DNA and microsatellites), parasite, otolith stable isotope, and growth data are synthesised to determine the stock structure of S. semifasciatus across northern Australia. Integration of the results from all techniques identified at least six S. semifasciatus stocks for management purposes. Further, the use of the ISD approach provided a simple basis for integrating multiple techniques and for their interpretation. The use of this holistic approach was a powerful tool in providing greater certainty about the appropriate management units for S. semifasciatus. Future stock structure studies investigating spatial management questions in the fisheries context should adopt a holistic approach and apply the ISD approach for a more accurate definition of biological stocks to improve fisheries management.

ICES Journal of Marine Science, 2014

Biomass, catchability, and natural mortality are key parameters in fish stock assessment. Yet, it... more Biomass, catchability, and natural mortality are key parameters in fish stock assessment. Yet, it is difficult to estimate these quantities, especially natural mortality, when only fishery data are available. Using a method of population depletion analysis, we estimated these population and biological quantities for the white banana prawn (Penaeus merguiensis) in Australia's valuable Northern Prawn Fishery. In addition, we directly included fishing power change over time. The models were implemented in a Bayesian framework by incorporating process error, observation error, and random variability for the underlying parameters. The posterior median initial fishable biomass ranged from ∼2000 to 7000 t year−1, and the median catchability varied from ∼3.8 × 10−4 to 7.3 × 10−4 boat-day−1, resulting in an average fishing power increase of 2.6% per year. An unexpected result is the estimate of exponential natural mortality rate of ∼0.03 week−1. This value is substantially lower than an ...

The current project investigated relationships between environmental factors and harvests of crab... more The current project investigated relationships between environmental factors and harvests of crabs in the Gulf of Carpentaria (GoC), northern Australia. This was in response to industry and managerial concerns about consistent declines in harvests of GoC Giant Mud Crab (Scylla serrata). In the orthern Territory (NT), declines occurred between 2009 and 2016, whilst in Queensland (Qld), declines occurred between 2013 and 2016. The declines occurred despite different management arrangements (e.g. NT harvests females, whereas Qld does not), suggesting common environmental factors were involved.

Journal of Fish Biology, Oct 24, 2016

Multivariate and machine-learning methods were used to develop field identification techniques fo... more Multivariate and machine-learning methods were used to develop field identification techniques for two species of cryptic blacktip shark. From 112 specimens, precaudal vertebrae (PCV) counts and molecular analysis identified 95 Australian blacktip sharks Carcharhinus tilstoni and 17 common blacktip sharks Carcharhinus limbatus. Molecular analysis also revealed 27 of the 112 were C. tilstoni × C. limbatus hybrids, of which 23 had C. tilstoni PCV counts and four had C. limbatus PCV counts. In the absence of further information about hybrid phenotypes, hybrids were assigned as either C. limbatus or C. tilstoni based on PCV counts. Discriminant analysis achieved 80% successful identification, but machine-learning models were better, achieving 100% successful identification, using six key measurements (fork length, caudal-fin peduncle height, interdorsal space, second dorsal-fin height, pelvic-fin length and pelvic-fin midpoint to first dorsal-fin insertion). Furthermore, pelvic-fin markings could be used for identification: C. limbatus has a distinct black mark >3% of the total pelvic-fin area, while C. tilstoni has markings with diffuse edges, or has smaller or no markings. Machine learning and pelvic-fin marking identification methods were field tested achieving 87 and 90% successful identification, respectively. With further refinement, the techniques developed here will form an important part of a multi-faceted approach to identification of C. tilstoni and C. limbatus and have a clear management and conservation application to these commercially important sharks. The methods developed here are broadly applicable and can be used to resolve species identities in many fisheries where cryptic species exist.

G3: Genes, Genomes, Genetics, Apr 1, 2013

Marine Ecology Progress Series, Aug 15, 2013

Marine Ecology Progress Series, 2013

Endangered Species Research, 2013

Glyphis sharks and pristid sawfishes are globally threatened. While some populations still exist ... more Glyphis sharks and pristid sawfishes are globally threatened. While some populations still exist in northern Australia, their distributions are poorly quantified. We used catch records from commercial fisheries and independent surveys to estimate the broad distribution and relative abundances of 2 Glyphis sharks (G. glyphis and G. garricki) and 4 pristid sawfishes (Pristis pristis, P. zijsron, P. clavata and Anoxypristis cuspidata) along the coast, estuaries and river systems of the Northern Territory, Australia. Coarse-scale catch data and records from commercial fishing logbooks that report encounters with Threatened, Endangered and Protected species confirm that small, fragmented populations are distributed across the Northern Territory coastline and suggest limited fishery interactions, although underreporting might occur.

Copyright and disclaimer © 2015 CSIRO To the extent permitted by law, all rights are reserved and... more Copyright and disclaimer © 2015 CSIRO To the extent permitted by law, all rights are reserved and no part of this publication covered by copyright may be reproduced or copied in any form or by any means except with the written permission of CSIRO. Important disclaimer CSIRO advises that the information contained in this publication comprises general statements based on scientific research. The reader is advised and needs to be aware that such information may be incomplete or unable to be used in any specific situation. No reliance or actions must therefore be made on that information without seeking prior expert professional, scientific and technical advice. To the extent permitted by law, CSIRO (including its employees and consultants) excludes all liability to any person for any consequences, including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from using this

Journal of Fish Biology, 2016

Sustainable exploitation of fisheries populations is challenging to achieve when the size of the ... more Sustainable exploitation of fisheries populations is challenging to achieve when the size of the population prior to exploitation and the actual numbers removed over time and across fishing zones are not clearly known. Quantitative fisheries' modeling is able to address this problem, but accurate and reliable model outcomes depend on high quality input data. Much of this information is obtained through the operation of the fishery under consideration, but while this seems appropriate, biases may occur. For example, poorly quantified changes in fishing methods that increase catch rates can erroneously suggest that the overall population size is increasing. Hence, the incorporation of estimates of abundance derived from independent data sources is preferable. We review and evaluate a fisheries-independent method of indexing population size; inferring adult abundance from estimates of the genetic effective size of a population (Ne ). Recent studies of elasmobranch species have shown correspondence between Ne and ecologically determined estimates of the population size (N). Simulation studies have flagged the possibility that the range of Ne /N ratios across species may be more restricted than previously thought, and also show that declines in Ne track declines in the abundance of model fisheries species. These key developments bring this new technology closer to implementation in fisheries science, particularly for data-poor fisheries or species of conservation interest.

ICES Journal of Marine Science: Journal du Conseil, 2015

Developing bioeconomic models of sequential fisheries is complicated when the two (or more) fishe... more Developing bioeconomic models of sequential fisheries is complicated when the two (or more) fisheries overlap temporally. In such cases, each fishery will be affected by the other, so both cannot be properly modelled as separate activities. This has recently become an issue for the Northern Prawn Fishery, in which bioeconomic modelling is used to set management limits. Modelling has focused on the tiger prawn component of the fishery, which mostly occurs in the second half of the year. However, successful management leading to stock recovery has resulted in this fishery now overlapping temporally with the banana prawn fishery, which occurs in the first half of the year. Ideally, an integrated model covering the whole year would be developed, but this is not practical for a number of reasons. In this study, we model the factors driving the level of fishing effort in the banana prawn fishery, which affects, and is affected by, the tiger prawn fishery. As expected, banana prawn fishing effort is driven largely by stock size, fleet size, catch rates, prices, and fuel costs. Effort increases with fleet size, but at a decreasing rate. Further, we find evidence that opportunity cost, namely the ability to fish in the tiger prawn fishery and the price of tiger prawns, also affects the level of effort in the banana prawn fishery.

Marine Policy, 2015

A holistic approach to stock structure studies utilises multiple different techniques on the same... more A holistic approach to stock structure studies utilises multiple different techniques on the same individuals sampled from selected populations and combines results across spatial and temporal scales to produce a weight of evidence conclusion. It is the most powerful and reliable source of information to use in formulating resource management and monitoring plans. Few examples of the use of a holistic approach in stock structure studies exist, although more recently this is changing. Using such an approach makes integration of results from each technique challenging. An integrated stock definition (ISD) approach for holistic stock structure studies was developed in this study to aid in the appropriate interpretation of stock structure results to guide the determination of fishery management units. The ISD approach is applied herein to a study of the northern Australian endemic grey mackerel, Scomberomorus semifasciatus (Scombridae). Analyses of genetic (mitochondrial DNA and microsatellites), parasite, otolith stable isotope, and growth data are synthesised to determine the stock structure of S. semifasciatus across northern Australia. Integration of the results from all techniques identified at least six S. semifasciatus stocks for management purposes. Further, the use of the ISD approach provided a simple basis for integrating multiple techniques and for their interpretation. The use of this holistic approach was a powerful tool in providing greater certainty about the appropriate management units for S. semifasciatus. Future stock structure studies investigating spatial management questions in the fisheries context should adopt a holistic approach and apply the ISD approach for a more accurate definition of biological stocks to improve fisheries management.

ICES Journal of Marine Science, 2014

Biomass, catchability, and natural mortality are key parameters in fish stock assessment. Yet, it... more Biomass, catchability, and natural mortality are key parameters in fish stock assessment. Yet, it is difficult to estimate these quantities, especially natural mortality, when only fishery data are available. Using a method of population depletion analysis, we estimated these population and biological quantities for the white banana prawn (Penaeus merguiensis) in Australia's valuable Northern Prawn Fishery. In addition, we directly included fishing power change over time. The models were implemented in a Bayesian framework by incorporating process error, observation error, and random variability for the underlying parameters. The posterior median initial fishable biomass ranged from ∼2000 to 7000 t year−1, and the median catchability varied from ∼3.8 × 10−4 to 7.3 × 10−4 boat-day−1, resulting in an average fishing power increase of 2.6% per year. An unexpected result is the estimate of exponential natural mortality rate of ∼0.03 week−1. This value is substantially lower than an ...

The current project investigated relationships between environmental factors and harvests of crab... more The current project investigated relationships between environmental factors and harvests of crabs in the Gulf of Carpentaria (GoC), northern Australia. This was in response to industry and managerial concerns about consistent declines in harvests of GoC Giant Mud Crab (Scylla serrata). In the orthern Territory (NT), declines occurred between 2009 and 2016, whilst in Queensland (Qld), declines occurred between 2013 and 2016. The declines occurred despite different management arrangements (e.g. NT harvests females, whereas Qld does not), suggesting common environmental factors were involved.