45 results
Industry
PROJECT NUMBER • 2017-013
PROJECT STATUS:
COMPLETED

Rebuilding Southern Rock Lobster stocks on the east coast of Tasmania: informing options for management

Understanding relationships between fisher behaviour, their expectations/aspirations, responses to changes in stock status and to management intervention is critical when implementing effective management strategies. This project aims to inform on the practical challenges to achieving the stock...
ORGANISATION:
University of Tasmania (UTAS)
TAGS
Wild Catch
Survey
Stock Assessment
Stakeholder
Responsible Fishing
SPECIES
Southern Rock Lobster
Environment
Environment
PROJECT NUMBER • 2020-105
PROJECT STATUS:
COMPLETED

Development of a Stock Status Report Card for Rays and Sharks

In response to increasing concerns for the status of shark and ray populations world-wide, and increasing pressure to ensure Australia’s shark and ray species are effectively managed and conserved, this project synthesised the scattered information, assessed individual species’ status...
ORGANISATION:
University of Tasmania (UTAS)
Environment
Environment
PROJECT NUMBER • 2012-008
PROJECT STATUS:
COMPLETED

Assessing the impact of marine seismic surveys on southeast Australian scallop and lobster fisheries

The present study, undertaken by University of Tasmania’s Institute for Marine and Antarctic Studies in conjunction with Curtin University’s Centre for Marine Science and Technology, was developed to investigate the potential impact of seismic surveys on economically important fishery...
ORGANISATION:
University of Tasmania (UTAS)
TAGS
Seismic
Modelling
Education
Analytics
Ageing
SPECIES
Southern Rock Lobster
Commercial Scallop
Industry
PROJECT NUMBER • 2002-409
PROJECT STATUS:
COMPLETED

Pathogenic Vibrio parahaemolyticus in Australian oysters

This project was designed to produce a “snapshot” of the prevalence of the bacterium Vibrio parahaemolyticus in Australian oysters during March and April of 2002. V. parahaemolyticus occurs in two main forms: pathogenic and non-pathogenic. In the past 3 years there have been several...
ORGANISATION:
University of Tasmania (UTAS)
TAGS
Disease
Aquaculture
SPECIES
Sydney Rock Oyster
Pacific Oyster

Assessment of broad-scale exploitation rates and biomass estimates for the Tasmanian southern rock lobster fishery

Project number: 1997-101
Project Status:
Completed
Budget expenditure: $468,370.00
Principal Investigator: Stewart Frusher
Organisation: University of Tasmania (UTAS)
Project start/end date: 22 Jun 1997 - 29 Apr 2003
Contact:
FRDC
TAGS
Tagging
Survey
Stock Assessment
Fishing Gear
Fisheries Management

Need

Traditionally, catch per unit of effort (CPUE) is used to monitor the health of the fishery and indicate the success or otherwise of management practices. Under current input controls CPUE is based on fishers maximising their total catch. In contrast, under output controls where catch is predetermined fishers will alter their catching scenarios to maximise the return (dollars per kilogram) from their catch. In southern rock lobster fisheries there is significant potential to alter fishing patterns to maximise economic return, especially through seasonal shifts in effort. As this change occurs, the value of using CPUE data to continue monitoring the fishery will be eroded. As such, both fisheries independant means of monitoring the fishery and new monitoring methods will become increasing important.
Both exploitation rates and biomass estimates are important stock assessment parameters and biological reference points in sustainable management of fisheries resources.
This project will evaluate fishery independant means of deriving these estimates and by determining the precision of derived estimates, demonstrate their suitability as biological reference points.
In a report to the Department of Industry, Technology and Commerce titled "Oceans of Wealth?", the Review Committee on Marine Industries, Science and Technology stated in their conclusion, 'The knowledge gained from scientific research into fish stocks and the impacts of the environmental and harvesting factors is a necessary but not sufficient element in the conservation of productive fish stocks. A vital element in both scientific assessments is the availability of reliable information about exploitation levels'. This project is aimed at addressing this need for southern rock lobster.

Objectives

1. To assess the precision of exploitation rates and biomass estimates derived from broad scale sampling using fisheries independant and fishery dependant sampling.
2. To evaluate both the precision and cost effectiveness of biomass estimation from fisheries dependant and fisheries independent derived exploitation rates and recommend future monitoring methodology for the rock lobster fishery.

Final report

ISBN: 1-86295-079-2
Author: Stewart Frusher
Final Report • 2003-03-25 • 2.06 MB
1997-101-DLD.pdf

Summary

Exploitation rate is an important fishery assessment parameter linking catch to legal-sized biomass, the portion of the stock available for harvest.  Relative change in legal-sized biomass is a crucial performance indicator for the fishery as it measures the success of management outcomes.  Under the recently introduced Individual Transferable Quota Management System (ITQMS) in the Tasmanian rock lobster fishery, rebuilding of legal-sized biomass is a key management objective.  The assessment model that produces biomass estimates for this fishery is primarily dependent on commercial catch and effort data. 

The use of commercial catch and effort data for stock assessment relies on its de facto relationship with stock abundance.  However, the relationship between catch and effort data and abundance is not always constant or linear.  Improvements in fishing gear and technology can result in greater catch for a given amount of effort, unrelated to changes in the biomass.  Management changes and fishers’ behaviour can also affect the relationship between catch rates and biomass.  Under the new ITQMS introduced in 1998, catch is fixed and improved profits can be made by improving the return per unit of fish caught rather than by increasing the amount of catch through increased effort.  Thus fishing during periods when catch rates are low but price is high can change the catch effort relationship independent of biomass change.

Fishery independent surveys, using established sampling protocols and standardised fishing gear are a way in which catch rates can be standardised irrespective of gear efficiencies or fisher’s behaviour.  If these surveys can also produce accurate estimates of exploitation rate then accurate estimates of biomass can be achieved, provided the exploitation rate estimates are representative of the fishing grounds.  Fishery independent estimates of exploitation rate are thus a valuable way of validating model biomass estimates especially with the introduction of an ITQMS where the relationship between catch rates and legal-sized biomass was likely to change pre- and post-quota.

This project aimed to trial change-in-ratio (CIR) and index-removal (IR) techniques to obtain estimates of exploitation rate and biomass from broad scale regions in the fishery.

Keywords: southern rock lobster, change-in-ratio, index-removal, exploitation rates, tagging.

Environment
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