Search

The reliable quantification of microplastic contamination in chitinous organisms requires validated methods to remove interfering complex organic and inorganic material. This study trialled KOH, H 2 O 2 and HNO 3 digestion methods on the digestive tracts of two large decapods (Panulirus cygnus and Portunus armatus) to validate a protocol that facilitates reliable microplastic extraction. KOH digestion provided the best recovery (>95 %) of all polymers (e.g. polyamide, polyethylene, polyethylene terephthalate, polypropylene, polystyrene and polyvinyl chloride), with the lowest impact to their physical morphology and chemical spectra. While HNO 3 , and HNO 3 + H 2 O 2 treatments were more effective at digesting chitin, they destroyed polyamide, and altered several other polymers. High digestion efficiency did not result in high matrix clarification or high microplastic recovery for large decapods. This study emphasises the importance of validating species-specific microplastic extraction methods, whilst proposing additional post-digestion protocols, such as density separation, for complex samples, that can be applied in future research investigating plastic contamination in large decapods. • KOH provided best recovery of microplastics from digestive tracts of large decapods. • High digestion efficiency (HNO 3 /H 2 O 2) did not result in high polymer recovery. • Specific method protocols depend on sample composition. • Density separation is needed when digestive tracts contain sediment. [ABSTRACT FROM AUTHOR]

Abstract The frequency of disease within coral communities was evaluated using an 18-month series of coral photographs taken before, during, and after a major dredging program at Barrow Island, off Australia's northwest coast. Up to 60 corals were assessed repeatedly at each of four dredging 'impact' sites (<1 km from dredging), and four 'reference' sites (>20 km from dredging). Contrary to an earlier report, the frequency of occurrence of coral disease (usually <5% of corals) was not significantly altered by dredging. The pattern of occurrence of coral disease does not constitute a suitable early warning bioindicator of dredging impacts on coral. This study suggests that disease is difficult to measure and evaluate, and is not a key indicator in the potential impacts of dredging on coral health. We propose that environmental monitoring during dredging should continue to focus on known impact indicators. Highlights • Investigation showed no increase in coral disease during or after a large dredging program. • Disease may occur naturally in many coral communities without much impact. • Coral disease is not a suitable indicator of dredging impacts. • Visual diagnosis of some coral diseases may be unreliable. [ABSTRACT FROM AUTHOR]

Ecosystem-based fisheries management (EBFM) is often termed triple bottom line because it takes into account ecological, economic and social criteria. Effective implementation of EBFM requires development of appropriate governance structures for decision-making processes and management, so governance effectiveness and efficiency can be regarded as the fourth element in a ‘quadruple bottom line.’ Few fisheries have explicitly considered all four criteria within their resource assessments and harvest strategies. Furthermore, as some of these objectives may be in competition (e.g. employment levels, profit), a simultaneous evaluation of these criteria is required to identify the optimal level of fishing to deliver the best overall community outcome. The western rock lobster, Panulirus cygnus , resource in Western Australia is used as an EBFM case study by evaluating: sustainability of target species and effects on ecosystem and protected species; economics of the fishery; effect on employment, coastal communities and quality of recreational fishing; and governance effectiveness including explicit sectoral catch allocations, and the efficiency of monitoring and compliance systems. In 2010 the fishery moved from effort-controlled maximum sustainable yield (MSY) to a quota-controlled, maximum economic yield (MEY) system. This study explicitly examined how different levels of harvesting across the MSY to MEY range affected each of ten EBFM criteria. We confirmed that these individual objectives were maximised at different total allowable commercial catches. However an example is provided for weighting of objectives from a possible management perspective that identified the upper end of the MEY range as likely to generate the optimum outcome for this fishery. [ABSTRACT FROM AUTHOR]

The western rock lobster ( Panulirus cygnus ) fishery is Australia’s most valuable single-species fishery, worth AUD$200–$400 million annually. Stock assessment for this fishery utilises the puerulus settlement to predict recruitment to the fishery 3–4 years later. This predictive ability has been particularly useful recently, due to an unprecedented period of low settlement between 2006/07 and 2012/13. Pre-emptive management action (~70% effort reduction) was taken to provide greater protection to the breeding stock which also moved the fishery to the maximum economic yield (MEY) level of effort for the projected recruitment. In 2010/11, the fishery moved from an effort-controlled to a quota-controlled fishery, which led to changes in fishing practices resulting in reductions in fishing costs and increases in lobster prices of about US$16/kg. This provided a unique opportunity to compare an MEY assessment under effort and quota controls. The MEY assessment under quota controls for a 5-year period indicated that annual harvest rates of 37–47% of legal biomass will achieve catches of 5780–7370 t. in 2014. This MEY target harvest range, which complements existing sustainability reference points based on egg production, is robust to a range of costs, prices and profit discount rates. This catch range enables industry/managers to take into account marketing implications and social issues (e.g. employment) in quota setting and therefore could be considered a socio-economic target. The MEY level of fishing has increased egg production to well above threshold levels that were based on maximum sustainable yield, providing the fishery with increased resilience when faced with environmental perturbations. This enables consideration for relaxing some existing biological controls, e.g. setose (mature) females, females above a maximum size, and lobsters 76–77 mm carapace length. The relaxation of these controls is estimated to increase profits by about AUD$15 million annually due to higher catch rates and reduced fishing effort while maintaining egg production well above threshold levels. [ABSTRACT FROM AUTHOR]

Abstract: The western rock lobster (Panulirus cygnus) fishery has been facing significant economic pressure from increasing costs, lower prices as well as predicted reduced catches due to low recruitment. A maximum economic yield (MEY) assessment estimated the fishing effort that would maximise the net present value of profits over 2008/09–2013/14 was about 50%–70% reduction of 2007/08 effort. The assessment accounted for fixed vessel costs and the variable pot lift cost. An important component of this assessment was the use of puerulus settlement time series that provided a reliable predictor of recruitment to the fishery 3–4 years later. This can be contrasted to most MEY assessments that would use an average catch-effort relationship rather than taking into account the expected recruitment. This predictive ability has been particularly useful as there has been a period of unusually low puerulus settlements over the 5 years (2006/07–2010/11) including the lowest two settlements in the 40-year time series. Due to the low settlements, substantial management changes were implemented in 2008/09 and 2009/10 (44% and 73% reduction in nominal fishing effort, respectively compared to 2007/08) to maintain the breeding stock at sustainable levels by having a significant carryover of legal lobsters into future years of lower recruitment. These effort reductions provided a unique opportunity to assess the economic impact of a fishery moving to an MEY effort level over two years. The CPUE increased from 1.1kg/pot lift in 2007/08 to 1.7 and 2.7 in 2008/09 and 2009/10, respectively. These CPUEs were much higher than the expected levels (1.2 and 1.1, respectively) if the 2007/08 effort had been maintained in these two years. The vessel numbers declined by 14% and 36% in 2008/09 and 2009/10, respectively, compared to 2007/08. The fishery profit increased by AUS$13 and 49 million for 2008/09 and 2009/10, respectively, compared to that estimated if the 2007/08 effort level had continued. This assessment demonstrates the economic benefits of fishing at a level close to that estimated for MEY under an input management regime. The management decision-rule framework is currently based on having the egg production above a threshold reference level to ensure sustainability and now a target reference point based on MEY principles is also being considered. [Copyright &y& Elsevier]

Use of catch and release, a growing aspect of recreational angling, is promoted for most recreational fisheries, including the fishery for the barramundi Lates calcarifer, an iconic sport fish of northern Australia. Landing nets are commonly used to remove fish from the water and to help hold and control fish while hooks or lures are removed before release. We investigated damage to mucus, scales, skin, and fins of 1.0-3.5-kg barramundi that were caught and held for 60 s in two different types of landing net. The two landing nets represented the commonly used knotted-mesh net and the newer knotless net, which has a smaller mesh size and a fiat bottom. Both types of landing net caused some injury, such as mucus loss, scale loss, and fin tears. However, use of the knotless, flat-bottomed landing net considerably reduced the occurrence of these injuries. Holding in the knotted net was associated with fin damage scores and dermal abrasion scores that were over four and five times greater, respectively, than the scores associated with holding in the knotless net. No fish died as a result of being handled in either net. These results are similar to those of other studies that investigated smaller fish. The effects of these injuries on fish survival are discussed. [ABSTRACT FROM AUTHOR]

There are several ways to set biological reference points (BRP) for harvest strategies, but one of the most direct methods is to use the stock-recruitment relationship (SRR). Even if the SRR is not statistically significant, it provides valuable information about the spawning stock levels that don't influence the recruitment that is relevant to setting BRP. Environmental factors, particularly extreme events such as the 2011 Western Australia (WA) marine heatwave, are typically a major driver of recruitment, so it is important to assess their influence as ignoring this effect may bias the SRR. This study examines the SRR for 13 invertebrate stocks in WA including lobster, prawn, scallop, abalone, pearl oysters and crabs. These stocks have long time series of fishery-independent juvenile abundance indices, which provide a clear signal of the year-class strength that improves the ability to assess the SRR and environmental effects. Eleven stocks showed a significant environmental effect on recruitment with seven stocks demonstrating a significant spawning stock effect. The stock-recruitment data is used to determine the BRP based on the species' specific biological information, even when the relationship is not significant. Importantly, management action in the harvest control rules is not just reactive to low spawning stock levels but is proactive based on the juvenile abundance to ensure that the level of fishing results in future spawning stocks being maintained above the BRP. This evidence-based approach to setting BRPs and the proactive management approach adopted in the harvest strategy can be invaluable to fisheries management generally. [ABSTRACT FROM AUTHOR]

Fishing rights and co-management are considered important aspects of fisheries management. But with rights comes a responsibility to contribute data that improves stock assessments and harvest strategies. This responsibility should include contributing data based on fishery-independent surveys (FIS) that provide robust measures of stock abundance and greater confidence in stock assessments, reducing risks to stock sustainability and resulting in more reliable management. FIS conducted with stakeholders provides a direct link between stock abundance indices and their own experience giving them ownership and a better appreciation of stock status. We examine case studies from Western Australian fisheries in four categories: FIS conducted using research vessels; FIS conducted on recreational fisheries using citizen-science; FIS conducted using volunteer industry vessels, and FIS using chartered industry vessels. These FIS cover fisheries with different gear, management, fishing sectors, value and number of participants. The case studies demonstrate that there are a number of ways that FIS designs may be implemented, with each fishery having a unique approach with a common element that they represent standardised surveys. We consider that all fisheries require some type of FIS and this paper discusses options of how this might be achieved. However, FIS can be expensive, so surveys must be cost effective to ensure that they endure. The approach to developing FIS should include collaboration with stakeholders in a co-management agreement. The FIS could be a requirement of having fishing rights and taken into account when developing management arrangements, e.g. allocation of part of the entitlements for a FIS. • Fishers with fishing rights and co-management should support stock surveys. • Survey designs will vary depending on the objectives and fishery characteristics. • Case studies examine surveys with different gear, management, sectors and value. • Fishery-independent surveys must be cost effective to ensure that they endure. • Survey development should be part of co-management and management arrangements. [ABSTRACT FROM AUTHOR]