ORCID Profile
0000-0003-4317-8186
Current Organisations
Western Australia Department of Fisheries
,
Universidad de Buenos Aires
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Publications
Gillnet selectivity for non‐targeted shark species in temperate Australia
Publisher: Wiley
Date: 09-11-2022
DOI: 10.1111/FME.12570
Abstract: The use of size‐selective fishing gear has been fundamental for the successful management of shark populations. For the main Australian shark fisheries, available data sets on gillnet selectivity experiments conducted since the 1990s were used to estimate gillnet selectivity parameters for nine commonly caught non‐target species: broadnose, draughtboard, Port Jackson and school sharks, common and southern sawsharks, smooth hammerhead and spikey and whitespotted dogfish. Size at selection increased with mesh size, but it varied with species, with some species having broader selectivity curves due to their particular morphological features. In particular, smooth hammerhead had much broader selectivity curves and larger length at maximum selection than other species of comparable size such as the broadnose shark. The selectivity curves derived in this study will allow a more accurate interpretation of catch size composition and model‐based assessments of stock status of these species
Quantifying shark and ray discards in Western Australia’s shark fisheries
Publisher: CSIRO Publishing
Date: 09-11-2021
DOI: 10.1071/MF21159
Abstract: Commercial fisheries can discard a considerable volume of sharks and rays, which, as a group, are of high conservation concern. In Western Australia (WA), commercial shark fishing commenced in the 1940s however, catch time series are not available for discarded species. The present study quantified catch (i.e. dead in iduals) time series of discarded sharks and rays in WA’s shark fisheries using on-board observer information collected since 1993 and testing assumptions through sensitivity analysis. Overall, 18 shark and ray taxonomic groups were discarded, comprising ~20% of the observed catch by number. Port Jackson shark, southern eagle ray and spurdogs were the most commonly discarded elasmobranchs, followed by western wobbegong, angel sharks, stingrays, and guitarfish and shovelnose rays. For the base case scenario, the catch of these species was small, peaking at 12.6, 5.6, 1.3, 1.8, 4, 1.3 and 2.7 tonnes (Mg) respectively, given their low post-release mortality (PRM). Current catch levels were even lower (e.g. Mg for Port Jackson shark). Other discarded elasmobranchs were rarely caught. Assuming 100% PRM resulted in higher annual catches, highlighting the need for further research on the PRM of sharks and rays. The reconstructed catch series will be used in risk assessments to determine the sustainability of discarded species.
Conventional tagging of sharks in Western Australia: the main commercial species exhibit contrasting movement patterns
Publisher: CSIRO Publishing
Date: 21-07-2021
DOI: 10.1071/MF20367
Abstract: Understanding movement patterns underlies effective management and conservation measures. The current study summarises the main findings from a tagging program of Western Australian sharks to provide insights into the movement patterns of the main commercial shark species: dusky (Carcharhinus obscurus), sandbar (C. plumbeus), gummy (Mustelus antarcticus) and whiskery (Furgaleus macki) sharks. Between 1993 and 2020, 000 in iduals from 52 taxonomic groups were implanted with conventional tags in Western Australia, of which 8.5% were recaptured. Most of the tagged (74.5%) and recaptured (95.8%) in iduals belong to the four main commercial shark species. Recaptured in iduals of these species, as well as tiger (Galeocerdo cuvier) and bronze whaler (C. brachyurus) sharks showed displacements of km and rates of movement (ROMs) of km day–1, with the exception of whiskery sharks, which showed much slower ROMs ( km day–1). Despite tagged dusky and sandbar sharks being predominately small in iduals and gummy and whiskery sharks being large in iduals, dusky and sandbar sharks had faster ROMs and a greater proportion of recaptures outside the release zone. Our study provided the information required for estimating movement rates across different fishing zones and therefore defining the spatial scale for managing these shark species.
Spatial and temporal patterns in catch rates from multispecies shark fisheries in Western Australia
Publisher: Elsevier BV
Date: 11-2021
Patterns in abundance and size of sharks in northwestern Australia: cause for optimism
Publisher: Oxford University Press (OUP)
Date: 10-10-2020
Abstract: Reliable information for population assessments is rare for sharks. We quantified patterns in catch rates and mean size for numerous tropical and subtropical species from 15 years of fishery-independent surveys (2002–2017) in northwestern Australia. This study region represents an area of ~0.8 million km2 which was closed to commercial shark fishing from 1993 or 2005 onward due to the very high State-wide catches of sandbar (Carcharhinus plumbeus) and dusky (Carcharhinus obscurus) sharks. A total of 43 shark and ray species were s led, with sandbar shark being the most commonly caught species, followed by milk (Rhizoprionodon acutus), spot-tail (Carcharhinus sorrah), tiger (Galeocerdo cuvier), blacktip (Carcharhinus limbatus and Carcharhinus tilstoni), dusky and sliteye (Loxodon macrorhinus) sharks, and scalloped hammerhead (Sphyrna lewini). For sandbar shark, catch rates increased between 2008 and 2017 whereas for other taxa catch rates were mostly stable (albeit fluctuating). Mean size at capture fluctuated across years with no particular trends. Unlike for other parts of the world, catch rates and mean size of northwestern Australian sharks have been stable or increased in recent years. Though most shark species have conservative life histories, when science, management and enforcement work synergistically, sustainable resource use, recovery and conservation outcomes can all be achieved.
The spatial segregation patterns of sharks from Western Australia
Publisher: The Royal Society
Date: 08-2016
DOI: 10.1098/RSOS.160306
Abstract: The extent to which sharks segregate by size and sex determines the population structure and the scale at which populations should be managed. We summarized 20 years of fisheries-dependent and independent s ling to define the spatial patterns of size and sexual segregation for sharks in Western Australia. Carcharhinus obscurus and C. plumbeus showed a large-scale (more than 1000 km) latitudinal gradient in size. Large in iduals occurred predominantly in the northwest and north whereas smaller in iduals occurred predominantly in the southwest and south. Mustelus antarcticus and Furgaleus macki showed strong sexual segregation at very large scales. Females occurred predominantly in the west and southwest whereas the proportion of males in catches substantially increased in the southeast. The populations of other shark species did not show sex and size segregation patterns at very large scales most species, however, showed varying degrees of segregation when data were analysed at a smaller scale. These findings highlight the importance of matching the scale of observation to the scale of the phenomenon observed. As many shark species are highly mobile, if s ling is opportunistic and constrained both temporally and spatially, the observed segregation patterns may not be representative of those at the population level, leading to inaccurate scientific advice.
Acoustic and conventional tagging support the growth patterns of grey nurse sharks and reveal their large-scale displacements in the west coast of Australia
Publisher: Springer Science and Business Media LLC
Date: 29-10-2019
Evidence of historical isolation and genetic structuring among broadnose sevengill sharks (Notorynchus cepedianus) from the world’s major oceanic regions
Publisher: Springer Science and Business Media LLC
Date: 26-03-2021
Quantifying teleost discards in the shark fisheries of Western Australia
Publisher: Wiley
Date: 10-09-2022
DOI: 10.1111/JFB.15193
Abstract: Quantifying discards is essential for assessing the impact of fisheries on non‐target species and the ecosystems in which these fisheries operate. In Western Australia (WA), fishers are required only to report catches of retained species. For the currently operating shark fisheries of WA, the authors quantified catch time series of discarded teleosts using data from at‐sea observers collected since 1993. Sixty‐two teleost species were observed in the catch of which 20 were routinely discarded. The most commonly discarded teleosts were western buffalo bream/silver drummer, Kyphosus cornelii / K. sydneyanus, and dusky morwong, Dactylophora nigricans . Annual discards peaked in the 1990s nonetheless, current discard levels, 36.9 ± 2.1 ( S.E. ) t year −1 , are much lower than the overall annual retained catches ( c. 1000 t year −1 ). The catch time series reconstructed in this study are important inputs for assessing the ecosystem‐based approach used for managing WA's shark fisheries.
Quantifying the unreported and unaccounted domestic and foreign commercial catch of sharks and rays in Western Australia
Publisher: Springer Science and Business Media LLC
Date: 07-02-2021
Risk-based weight of evidence assessment of commercial sharks in western Australia
Publisher: Elsevier BV
Date: 05-2021
Recreational Harvest of Sharks and Rays in Western Australia Is Only a Minor Component of the Total Harvest
Publisher: MDPI AG
Date: 31-05-0007
DOI: 10.3390/SU13116215
Abstract: Sharks and rays are a global conservation concern with an increasing number of species considered at risk of extinction, mostly due to overfishing. Although the recreational harvest of sharks and rays is poorly documented and generally minimal, it can be comparable to the commercial harvest. In this study, we quantified the recreational harvest of sharks and rays in Western Australia, a region with a marine coastline greater than 20,000 km. A total of 33 species/taxonomic groups were identified, with the harvest dominated by dusky and bronze whalers, blacktip reef sharks, gummy sharks, Port Jackson sharks, wobbegongs, and rays and skates. Eighty-five percent of in iduals were released with an unknown status (alive or dead). We found a latitudinal gradient of species composition, with tropical and subtropical species of the genus Carcharhinus dominating in the north and temperate species from a range of families dominating in the south. Overall, our findings showed that the recreational harvest was negligible when compared with commercial landings.
Related Organisations
Related Funding Activities
No related grants have been discovered for Matias Braccini.