44 results

Predicting the impact of hook decrements on the distribution of fishing effort in the ETBF

Project number: 2008-028
Project Status:
Completed
Budget expenditure: $130,865.00
Principal Investigator: Chris Wilcox
Organisation: CSIRO Oceans and Atmosphere Hobart
Project start/end date: 29 Sep 2008 - 30 Jun 2009
Contact:
FRDC

Need

AFMA recently announced the completion of amendments to the ETBF management plan, and the call for applications for statutory fishing rights. These fishing rights, and the effort allocation of effort that accompanying them, will be managed using Spatial Area Factors (SAFs). SAFs are multipliers that translate the actual amount of fishing effort expended, e.g. in thousands of hooks, into the amount of effort units that are taken off an SFR holders allocation. The intent of these SAFs is to allow spatial management of the fishery, by providing incentives for fishing in areas with low SAFs and disincentives in areas with high SAFs. If used effectively, these SAFs may provide a mechanism for reducing many of the management conflicts in the fishery, such as catch of seabirds and turtles, local depletion of target stocks, and under-exploitation of high seas areas. However, in order to effectively apply the SAFs, AFMA will need to be able to determine the motivational effect of the SAF on fishermen's location choices. Moreover, the SAFs will affect the total allowable effort (TAE) that is actually realized in the fishery in a given year, so not only will they affect individual fishers, they will also affect the performance of the fishery as a whole. It will be critical to be able to make some predictions about how the realized TAE will change, based on the structure of the SAFs in order to weigh alterative management options prior to implementing them. Finally, a move from TAEs to TACs and ITQs will substantially affect the structure of the fishery. Although we will not directly address those changes in this proposal, the behavioral models developed in this project would be rapidly adaptable to a TAC/ITQ system, and could form a basis for informing management as to the potential effects.

Objectives

1. Develop a statistical (multivariate logit) model to predict the distribution of fishing effort in the ETBF
2. Develop a process (a state-dependent behavioral) model of effort allocation for an input managed fishery with individual effort allocations
3. Evaluate the impact of a series of SAF scenarios on the distribution of fishing effort in the ETBF using statistical and state-dependent behavioral models
Environment
PROJECT NUMBER • 1995-014
PROJECT STATUS:
COMPLETED

Indices of recruitment and effective spawning for tiger prawns stocks in the Northern Prawn Fishery

In the mid to late 1980s NORMAC began to suspect that tiger prawn spawning stocks in the NPF may have been reduced by fishing to levels that reduced recruitment to the fishery. A vessel buy-back scheme and other effort reductions were introduced to reverse this trend but, by the mid-1990s, the...
ORGANISATION:
CSIRO Oceans and Atmosphere Hobart

Biological parameters for stock assessments in South Eastern Australia – an information and capacity uplift

Project number: 2022-032
Project Status:
Current
Budget expenditure: $766,806.00
Principal Investigator: Alistair Hobday
Organisation: CSIRO Oceans and Atmosphere Hobart
Project start/end date: 28 Feb 2023 - 27 Feb 2027
Contact:
FRDC

Need

South-east Australian waters are recognised as ocean warming hotspots and overall, Australian waters have warmed faster than the global average (Hobday and Pecl 2013, IPCC 2019). Key components of the productivity of marine fish (growth, maturity, and recruitment) are expected to be changing in response to shifts in climate and it is entirely possible that there have been changes in fundamental productivity parameters for Australian stocks.
The regularity with which the biological parameters that are used in stock assessments are evaluated and updated varies considerably among the species that are targeted in Commonwealth Fisheries. Assessment of changes in these parameters is limited largely to sensitivity analyses consisting of exploring alternate time-invariant values of natural mortality, maturity and stock recruitment steepness at values close to those used in the base-case assessment and generally agreed upon as within acceptable ranges of values. Recently an evaluation of the provenance of the biological parameters used in stock assessments found that species from the SESSF contained the largest number of parameters where provenance could not be ascertained from the literature and that SESSF species comprised over 50% of those species where biological parameters were determined to be more than 20 years old (FRDC project 2019-010, Evans et al. 2022). When plausible changes to biological parameters (such as those that might occur under environmental change) were explored quite substantial changes in biomass estimates for key target species occurs. This means that parameter mis-specification, such as due to relying on older parameter estimates that encode predator-prey and other ecosystem processes from a system state that has since changed, could be a real issue for assessments in the SESSF.
The reliance of current assessments on what is likely to be out-of-date information leads to considerable uncertainty, which cannot be easily quantified that then propagates into management decisions. Without an understanding of changes in biological parameters and how these changes might impact assessments, it is difficult (if not impossible) to evaluate whether current management measures are ensuring sustainability. Overall, the project recommended that updating parameters in stock assessments, modifying base cases, or more heavily drawing on results from sensitivity analysis in discussion of stock assessment results would be strongly advisable, especially in regions where large environmental shifts are known to be occurring, such as the SESSF.
The RV Investigator voyages to be conducted in 2023 and 2024 under the CSIRO led SEA-MES project provide a unique opportunity to access relevant biological samples that could be used to update the biological parameters identified in FRDC Project 2019-010 as a high priority (age, growth, reproduction, stock structure and although not directly used in stock assessments themselves but having significant influence on parameters that are used in assessments (such as growth and mortality), diet and food webs). These voyages have a focus on the marine ecosystem that supports the SESSF and a number of the hypotheses being posed by the study are focused on target species within the SESSF and their food webs. This will result in significant sampling of those species , with the co-benefit that there will be new samples available for the contemporary estimation of key biological parameters and evaluation of the representativeness of parameters being used in stock assessments (and with sufficient sample numbers to ensure robust updated estimates). These voyages also provide a unique opportunity to build capacity in at sea sampling, exposure to ecosystem level sampling design and post-voyage biological analyses. By linking post voyage analyses with the direct needs of both stock assessments and ecosystem models used in the SESSF, the project provides opportunities for building deeper understanding of the use of biological parameters in stock assessments, and direct application of fisheries biology.

Objectives

1. Develop, in collaboration and consultation with key research and fishery stakeholders a series of projects involving postgraduate students and early-mid career researchers that directly address priority areas for updating biological parameters for target species in the SESSF and understanding the implications of changing parameters on the fishery
2. Reduce uncertainties in stock assessments for the SESSF through the updating of biological parameters and understanding of key interactions between and drivers of change in biological parameters
3. Progress methods development associated with ascertaining biological parameters and progressing stock assessments to increase efficiencies, reduce time and financial costs, expand applicability and reduce uncertainties in stock assessments
4. Build fisheries capability across multiple pathways to support the ongoing sustainability of high quality fisheries research
Environment
PROJECT NUMBER • 2011-032
PROJECT STATUS:
COMPLETED

Incorporating the effects of marine spatial closures in risk assessments and fisheries stock assessments

Within the framework of the Commonwealth Harvest Strategy Policy, the Australian Fisheries Management Authority (AFMA) has adopted clear decision rules to set catch limits for commercially targeted species in Commonwealth fisheries. In several fisheries, AFMA has adopted a tiered harvest strategy...
ORGANISATION:
CSIRO Oceans and Atmosphere Hobart
Environment
PROJECT NUMBER • 2004-024
PROJECT STATUS:
COMPLETED

Variation in banana prawn catches at Weipa: a comprehensive regional study

Since about the year 2000 there have been very low catches in the Weipa Region of the Northern Prawn Fishery (NPF); these low catches were different to other areas of the NPF where they continued to fluctuate around long-term means and continued to fall within predicted levels. Industry and managers...
ORGANISATION:
CSIRO Oceans and Atmosphere Hobart
Environment
PROJECT NUMBER • 1998-109
PROJECT STATUS:
COMPLETED

Risk analysis and sustainability indicators for prawn stocks in the Northern Prawn Fishery

This project has been highly successful at determining factors that affect the outputs and outcomes of the model and the uncertainty underlying the model system. The report has been divided into seven broad sections and two Appendices. The first chapter contains the context of the work;...
ORGANISATION:
CSIRO Oceans and Atmosphere Hobart
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