129,954 results

Determining ecological effects of longline fishing in the Eastern Tuna and Billfish Fishery

Project number: 2004-063
Project Status:
Completed
Budget expenditure: $562,357.40
Principal Investigator: Jock Young
Organisation: CSIRO Oceans and Atmosphere Hobart
Project start/end date: 14 Apr 2005 - 30 Nov 2008
Contact:
FRDC

Need

The ET&BF is presently dealing separately with a number of ecological issues. For example, impacts of longliners on shearwaters and turtles are current high profile problems. However, other issues such as depletion of swordfish, SBT bycatch, availability of tunas in relation to oceanographic features, bycatch of sharks and finning have all taken centre stage at different times in the short history of the domestic fishery. This approach is often reactionary, rather than strategic, and may not be the best use of research resources over the long-term. If the ET&BF is to move substantially toward ecosystem-based fishery management, as it is required to do under the EPBC act, rather than continue the individual species management approach, an ecosystem analysis providing ecosystem metrics must be developed. If, for example, ET&BF managers opt for time area closures as part of their management strategy to protect key species, developing these on a species-by-species basis has the potential to impact the whole fishery. To develop and evaluate time area closures that allow for minimizing risk of adverse impacts to the suite of key species, while allowing for optimal efficiency of fishing, understanding the associations, linkages and interactions between species is essential. This is the ecosystem approach. Developing an understanding of how ecosystem-associations relate to oceanographic features is also essential in open ocean systems where the dominant influence on distribution and local abundance is oceanography. The approach we are taking will provide the information needed to support an ecosystem-based management framework. Through the analyses we are proposing we will identify regional “hot spots”, detail their linkages and provide detailed scenarios as to how we think different management strategies and fishing practices will or will not impact pelagic food chains, ecologically related non-target species, competitors (e.g. sharks, marlins etc.) and their associated ecosystems. The need for ecosystem-based fishery management for the Western Pacific region has also been supported by PrepCon for the soon-to-be formed WCPFC (Working Paper 9, 2002).

Objectives

1. Identify the spatial extent and the temporal stability of the main ecosystems of the eastern tuna and billfish fishery based on their species composition and physical environment.
2. Define the trophic structure within these ecosystems with emphasis on the relationship between target, bycatch and threatened and protected species.
3. Develop an ecosystem model for the ETBF fishery incorporating data on the relative abundance of the species, trophic linkages and the physical environment from which the impacts of longline fishing on the ecosystem can be investigated and from which alternative harvest strategies can be evaluated.

Final report

ISBN: 9.78E+12
Author: Jock Young
Environment
PROJECT NUMBER • 2004-051
PROJECT STATUS:
COMPLETED

Management and monitoring of fish spawning aggregations within the West Coast Bio-region of Western Australia

Many strategies have evolved among fishes to maximise spawning success. One of the most striking of these is aggregation spawning, in which individuals group together, often at predictable times and locations in order to reproduce (cf. a school, which refers to a group of non-spawning fish)....
ORGANISATION:
Department of Primary Industries and Regional Development (DPIRD) WA
Environment

Relationships between fish faunas and habitat type in south-western Australian estuaries

Project number: 2004-045
Project Status:
Completed
Budget expenditure: $480,277.85
Principal Investigator: Fiona Valesini
Organisation: Murdoch University
Project start/end date: 29 Jun 2004 - 31 Dec 2008
Contact:
FRDC

Need

Since estuaries constitute such an important environment for many recreational and commercial fish species, plans for their management must be based on reliable data if they are to be useful in protecting and, if necessary, restoring crucial estuarine fish habitats. Managers thus require the following.
1. Sound quantitative data on the ways in which commercially and recreationally-important fish species and their different life cycle stages are distributed among the different types of habitat found in south-western Australian estuaries.
2. An ability to identify rapidly and reliably the type of habitat to which any site in an estuary should be allocated and therefore also to predict the likely composition of the fish fauna at that site.
3. Knowledge of the extent and distribution of the various habitat types within and amongst different estuaries which can serve as benchmarks against which the impacts of future environmental changes on the fish faunas can be gauged.
4. An understanding of the relationships between the benthic invertebrate components of the fauna, particularly those that make major contributions to the diets of fish, and the different types of habitat in estuaries. This will facilitate an assessment of the broader implications of changes in the estuarine environment on the fauna as a whole.

This project is necessary to underpin the following conservation planning and programmes. Western Australian Marine Conservation Reserve Program under the CALM Act (1984), the Comprehensive Management Plan (parts c, d) in the Environmental Protection Policy for Swan and Canning Rivers (Government Western Australia 2003), the Peel Development Commission in sustaining environmental health of the Peel-Harvey Estuary, the Recfishwest Policy detailing their Guiding Principles for Responding to Coastal, Marine, Riverine and Impoundment Development Proposals, and the Fish and Fish Habitat Protection Program undertaken by the Department of Fisheries WA.
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Objectives

1. Determine the suite of environmental criteria that are most useful for readily and quantitatively assigning any site in a particular estuary in south-western Australia to its appropriate habitat type.
2. Determine statistically how the compositions of the fish and benthic invertebrate assemblages in particular south-western Australian estuaries are related to habitat type.
3. Formulate a readily usable and reliable method for predicting which fish species are likely to be abundant at any particular site in an estuary.

Final report

Determination of a cost effective methodology for ongoing age monitoring needed for the management of finfish fisheries in Western Australia

Project number: 2004-042
Project Status:
Completed
Budget expenditure: $224,006.00
Principal Investigator: Dan Gaughan
Organisation: Department of Primary Industries and Regional Development (DPIRD) WA
Project start/end date: 14 Aug 2004 - 31 Aug 2007
Contact:
FRDC

Need

The implementation of ESD and the Integrated Fisheries Management Strategy for finfish fisheries of Western Australia will require periodic assessment of the status of the major species within each fishery. In most cases, age structured models are being developed to provide these assessments, but even in cases where full simulation models are not possible, assessing the status of these fish stocks would benefit greatly by having some information on temporal changes to their age structure. Thus, collecting a suitably accurate, time series of age structures for each of the major finfish species is a high priority for the effective management of all commercial and recreational fisheries across WA.

To achieve these objectives, regular monitoring of the age structures of more than 20 stocks/species will be required for inputs into assessment models. It is imperative that the most cost efficient monitoring scheme is developed that will provide estimates of the age distribution for each of these stocks at the level of precision, accuracy and frequency required for suitably robust assessments to be completed. For all species, ages are determined from sectioned otoliths, and validated through marginal incriment analysis. the relationship between age and other proxies for age(including fork length, otolith weight, and other otolith dimensions)will be used when appropriate, to develop alternative predictors of age. Statistical methods will then be used to generate population age structures for market/field samples. The reliability and cost of these proxy-based age estimators, relative to the precision dictated by the stock assessment will then be tested. Irrespective of what age estimator is used, optimising the number of individuals that needs to be aged (100, 200, 500 etc) and determining how frequently these need to be sampled (monthly, yearly, bi yearly, tri-yearly) and what spatial distribution of samples need to provide data of a sufficient quality for use in modelling their abundance must be assessed in a rigorous and explicit manner.

To determine the appropriate monitoring scheme for each of the 20 major finfish species/stocks in WA will require the completion of a series of rigorous cost benefit analyses. These analyses will ultilise the relative level of accuracy of the different age estimators, the cost of obtaining the samples, the costs of processing the samples in relation to the acceptable levels of precision and accuracy needed for the stock assessment purposes for which these data are being collected.

Objectives

1. Determine for stocks of the 20 major WA finfish species (4 - 5 in each bioregion) the relative accuracy of structures used to estimate age (eg. Sectioned/whole otoliths, lengths, otolith weight, other otolith dimensions or some combination of these).
2. For each stock, examine the relative impact on the calculated age-compositions and their effect on model outputs and conclusions from varying (i) the method of ageing used (only where this is possible from available data) (ii) the number of individuals used in the samples (iii) the spatial distribution of the samples used (iv) if possible, the frequency of sampling.
3. Using agreed levels of precision for the model outputs, undertake cost benefit analyses to generate the most appropriate long-term age structured monitoring program for each major finfish species in WA by assessing the method(s) of ageing, sampling intensity within each year and the frequency of sampling among years.

Final report

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