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Potter I.C.,Murdoch University | Chuwen B.M.,Murdoch University | Chuwen B.M.,University of Tasmania | Hesp S.A.,Murdoch University | And 5 more authors.
Journal of Fish Biology | Year: 2011

Biological characteristics of the marine species King George whiting Sillaginodes punctatus and Australian herring Arripis georgianus in three seasonally open estuaries (Broke, Irwin and Wilson Inlets), one permanently open estuary (Oyster Harbour) and one normally closed estuary (Wellstead Estuary) on the south coast of Western Australia have been determined and compared. Sillaginodes punctatus enters the seasonally and permanently open estuaries early in life and reaches total lengths (L T) >280 mm at which it can be legally retained and thus contributes to commercial and recreational fisheries in these systems. This sillaginid almost invariably emigrates from these estuaries before reaching its typical size at maturity (L T50) and does not return after spawning in marine waters. In contrast, virtually all female A. georgianus (≥98%) in the three seasonally open estuaries and the majority in the normally closed (89·5%) and permanently open estuaries (83%) exceeded the L T50 of this species at maturity, reflecting the fact that the nursery areas of this species are predominantly located much further to the east. Although adult females of A. georgianus in seasonally open and normally closed estuaries had developed mature ovaries by autumn, at which time they were prevented from migrating to the sea by closure of the estuary mouths, this species did not spawn in those estuaries. The oocytes in their ovaries were undergoing extensive atresia, a process that had been incipient prior to oocyte maturation. As the adult females of A. georgianus in the permanently open Oyster Harbour at this time all possessed resting gonads, i.e. their oocytes were all previtellogenic, the adults that were present in that estuary earlier and were destined to spawn in autumn must have emigrated from that permanently open estuary to their marine spawning areas prior to the onset of gonadal recrudescence. The body masses at length of A. georgianus, which were almost invariably higher in summer and autumn than in winter and spring, were greater in the very productive environments of the seasonally open and normally closed estuaries than in the less productive and essentially marine environment of Oyster Harbour and coastal marine waters. In general, the same pattern of differences between water bodies was exhibited by the growth of A. georgianus and by the more restricted data for body mass at L T and growth of S. punctatus. Despite an increase in anthropogenic activities in Wilson Inlet over the last two decades, the growth of both species was very similar to that recorded 20 years earlier. The fisheries implications of the results for the two species are discussed. © 2011 The Authors. Journal of Fish Biology © 2011 The Fisheries Society of the British Isles. Source


Bellchambers L.M.,Marine Research Laboratories | Evans S.N.,Marine Research Laboratories | Meeuwig J.J.,University of Western Australia
Marine and Freshwater Research | Year: 2010

Ecosystem-based fisheries management (EBFM) requires the expansion of fisheries research programs to include the relationship between target species and their habitats such that trophic and other ecological interactions can be assessed. The western rock lobster (Panulirus cygnus) is an ecologically important species that supports Australia's most valuable single-species fisheries. We tested the relationship between abundance and size of western rock lobster and benthic habitats based on the annual independent breeding stock survey and benthic towed video transects. The work was undertaken at Dongara, Jurien Bay and Lancelin, Western Australia between 2005 and 2007. Abundance of western rock lobster was significantly but moderately related to benthic habitat (adjR2 =0.28), with high abundances associated with high cover of mixed assemblage and Ecklonia sp. Size was effectively predicted by habitat (adjR2 =0.65) with larger lobsters found in mixed assemblages with sponge and smaller lobsters associated with mixed assemblage with Ecklonia sp. Our study has shown that understanding the influence of habitat and fishing pressure on the abundance and size of targeted species is a critical step in the effective implementation of EBFM. © 2010 CSIRO. Source


Chandrapavan A.,Marine Research Laboratories | Kangas M.I.,Marine Research Laboratories | Sporer E.C.,Marine Research Laboratories
Journal of Shellfish Research | Year: 2012

Saucer scallops, Amusium balloti, are targeted by Shark Bay prawn and scallop trawl fisheries where regulatory discarding can occur during summer and winter months that may adversely impact the recruitment of this resource. Survival of repeatedly discarded saucer scallops was thus estimated for the Shark Bay trawl fisheries using short-term tag-recapture experiments under various fishing and environmental conditions. Estimates of apparent survival of discarded scallops was significantly higher during the postspawning winter period (>90%) than during the prespawning summer period (20-90%), but no differences in survival between fishing grounds or between postcapture treatment groups (air exposed vs. those kept in a holding tank) were observed. This suggests that thermal stress from large differences in seasonal temperatures was more critical to scallop survival than differences in scallop reproductive condition. Thus past (pre-2004) management regulations that imposed regulatory discarding during the warmer summer months would have incurred high discard mortalities. Under current management measures, however, regulatory discarding is predominantly during winter months, when scallops exhibit higher resilience to trawlinduced stress. The results support the current management strategy of fishing during the warmer prespawning summer months when the amount of discards is less. Regulatory discarding during the winter spawning period may generate a higher discard rate but the associated discard mortality is at its minimum. Copyright © 2013 BioOne. Source


Fairclough D.V.,Marine Research Laboratories | Brown J.I.,Marine Research Laboratories | Carlish B.J.,Marine Research Laboratories | Crisafulli B.M.,Marine Research Laboratories | Keay I.S.,Marine Research Laboratories
Scientific Reports | Year: 2014

Citizen science offers a potentially cost-effective way for researchers to obtain large data sets over large spatial scales. However, it is not used widely to support biological data collection for fisheries stock assessments. Overfishing of demersal fishes along 1,000 km of the west Australian coast led to restrictive management to recover stocks. This diminished opportunities for scientists to cost-effectively monitor stock recovery via fishery-dependent sampling, particularly of the recreational fishing sector. As fishery-independent methods would be too expensive and logistically-challenging to implement, a citizen science program, Send us your skeletons (SUYS), was developed. SUYS asks recreational fishers to voluntarily donate fish skeletons of important species from their catch to allow biological data extraction by scientists to produce age structures and conduct stock assessment analyses. During SUYS, recreational fisher involvement, sample sizes and spatial and temporal coverage of samples have dramatically increased, while the collection cost per skeleton has declined substantially. SUYS is ensuring sampling objectives for stock assessments are achieved via fishery-dependent collection and reliable and timely scientific advice can be provided to managers. The program is also encouraging public ownership through involvement in the monitoring process, which can lead to greater acceptance of management decisions. Source

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