249 results
Environment
PROJECT NUMBER • 1995-058
PROJECT STATUS:
COMPLETED

Seamount fauna off southern Tasmania: impacts of trawling; conservation and role within the fishery ecosystem

In September 1995, the deepwater trawl fishing industry agreed not to trawl in an area of 370 km2 on the continental slope south of Tasmania for three years, as stated in a Memorandum of Understanding between the former Australian Nature Conservation Agency (now Environment Australia) (EA) and the...
ORGANISATION:
CSIRO Oceans and Atmosphere Hobart
TAGS
Remote Sensing
Habitat
Fishing Gear
Fishing Effort
Ecosystem

Development of the egg production method to assess the blue grenadier stock in the South East Fishery

Project number: 1995-035
Project Status:
Completed
Budget expenditure: $258,699.00
Principal Investigator: Tony Koslow
Organisation: CSIRO Oceans and Atmosphere Hobart
Project start/end date: 28 Jun 1995 - 30 Jan 1998
Contact:
FRDC
TAGS
Stock Assessment
Reproduction
Electronic Monitoring
Distribution
Biomass

Objectives

1. Overall objective: To develop the use of the egg proiduction method to assess the biomass of blue grenadier on the west Tasmania spawning ground. To achieve this overall objective requires completion of the following sub-objectives
2. Surveys of the blue grenadier egg distribution be completed during the 1995 and 1996 spawining seasons, covering the full period and area of blue grenadier spawning. The initial (1994) survey will provide a biomass estimate
3. The mean fecundity of the blue grenadier will be determined
4. The development rate of the blue grenadier eggs will be assessed as a function of temperature

Final report

ISBN: 0 643 06153 3
Author: Tony Koslow
Final Report • 2017-09-29 • 956.64 KB
1995-035-DLD.pdf

Summary

The blue grenadier stock is potentially the largest fish stock in the SEF, and following the decline in quota of orange roughy, the need to assess its potential became urgent. The stock has been surveyed using traditional trawl methods and acoustics, but both methods provide only 'snapshot' estimates and are unable to provide absolute estimates. There are two reasons for this: first, the stock is not currently being fished down so relative biomass estimates cannot be calibrated, and second, the proportion of fish spawning on the ground at any time -a factor by which the "snapshot" estimates must be multiplied to obtain an absolute estimate-is unknown.
 
Annual egg production estimates of stock size based upon egg surveys have been widely and successfully used since 1895 and this method has recently been used in the SEF with orange roughy. The method can provide an absolute measure of spawning stock biomass. Egg surveys tend to be less precise statistically than acoustic surveys, but there is less non­statistical error associated with the supplementary data required for egg production biomass assessment compared with those for an acoustic assessment.
 
Blue grenadier met the criteria for use of the annual egg production method of stock assessment. The blue grenadier spawning stock off western Tasmania was first surveyed from June through September 1994. The survey design was refined and the area resurveyed the following year.

Development of acoustic methods to survey orange roughy in the eastern and southern zones

Project number: 1995-031
Project Status:
Completed
Budget expenditure: $144,588.00
Principal Investigator: Tony Koslow
Organisation: CSIRO Oceans and Atmosphere Hobart
Project start/end date: 20 Sep 1995 - 5 May 1999
Contact:
FRDC
TAGS
Survey
Reproduction
Remote Sensing
Life History
Harvest Strategy

Objectives

1. Conduct 2-3 acoustic surveys of orange roughy spawning ground off St Helens, TAS during the peak spawning period 1995
2. Determine the species composition of acoustic marks through trawl sampling of the acoustic marks and the ensonification of targets with several frequencies
3. Determin the relative biomass and spawning condition of orange roughy in the Eastern and Southern zones during the spawining period based upon a survey of selected hills in the Southern Zone that contain the principal concentration of orange roughy
4. Assess the biomass of orange roughy in the area between St. Helens and the Southern Hills through a series of zig-zag transects between 700-1200m and to assess their spawning condition

Final report

ISBN: 0643 06191 6
Author: Tony Koslow
Final Report • 1999-04-09 • 9.30 MB
1995-031-DLD.pdf

Summary

Three acoustic surveys were carried out between 17 and 20 July 1996 on the orange roughy spawning ground off St. Helens, Tasmania. A combination of 22 demersal trawls and ensonification with three frequencies (12, 38 and 120 kHz) was used to assess the species composition around the spawning hill. Both methods showed that orange roughy were aggregated on only the north/northwestern half of the hill. Acoustic marks on the south/southwestern sector of the hill were composed predominantly of macrourids (rattails) and deepwater cods. This was the first successful use of multi-frequency acoustics to discriminate among species groups in a deepwater environment and should greatly enhance the resolution of deepwater acoustic surveys. Acoustic estimates of orange roughy biomass on the spawning hill ranged from 5649 - 9706 tonnes, down from 16,777 tonnes in 1993. A survey of the trawl ground off St. Patrick's Head noted a single moderate-sized aggregation on a single transect.
 
If the school as assumed to be spherical in cross-section, its biomass was 6% the biomass of the largest orange roughy school observed at St. Helens. The biomass at St. Patrick's Head thus appears to have been a small proportion of the biomass around St. Helens Hill during the survey, but the data were insufficient to derive a biomass estimate from this area with confidence. Acoustic surveys were also carried out on a small hill just north of St. Helens and on the seamounts in the Southern Zone but no significant acoustic marks associated with orange roughy were observed in these areas.
 
Several changes were made to the methods of analysis. First, the area of the strata comprising the St. Helens hill were re-calculated based on improved bathymetric and GPS data,. Secondly, we changed the method used to account for targets within the deep scattering layers (DSL) that extend across the survey area. A constant fraction of the ensonified targets were previously assumed to belong to the DSL, but this assumption was no longer tenable considering both the decline in orange roughy abundance on the hill and the ~2-fold variation in the abundance of midwater scatterers between surveys in 1996. Acoustic backscattering from areas outside the survey area were now measured for each survey and subtracted from the backscattering observed around the hill itself. These changes were applied retrospectively to biomass estimate from previous orange roughy surveys.
 
Environment
PROJECT NUMBER • 1995-016
PROJECT STATUS:
COMPLETED

The impact of changes in fishing patterns on red-legged banana prawns (Penaeus indicus) in the Joseph Bonaparte Gulf

The fishery for red-legged banana prawns in the Joseph Bonaparte Gulf (JBG) developed in the early 1980s. Since then, fishing effort has varied from 700 to 2600 boat-days per year and catches range from 200 to 1000 tonnes per year. Initially the JBG fishery developed as an alternative to fishing in...
ORGANISATION:
CSIRO Oceans and Atmosphere Hobart
TAGS
Stock Assessment
Resource Access And Allocation
Fishing Effort
Fisheries Management
Economic
Environment
PROJECT NUMBER • 1995-015
PROJECT STATUS:
COMPLETED

Estimation of population parameters for Australian prawn fisheries

One of the main objectives of fisheries management is to ensure the sustainability of fished stocks. To reach this objective scientists have to adequately assess the status of fished populations with quantitative models of the fishery systems. Most of these models require estimates of population...
ORGANISATION:
CSIRO Oceans and Atmosphere Hobart
TAGS
Wild Catch
Sustainability
Stock Assessment
Stakeholder
Population Dynamics
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
TAGS
Stock Assessment
Resource Access And Allocation
Reproduction
Population Dynamics
Oceanography
Environment
Environment
PROJECT NUMBER • 1994-152
PROJECT STATUS:
COMPLETED

Resolution of taxonomic problems and preparation of a user-friendly identification guide to whole fish and fillets for South East Fishery "quota species"

An upgraded identification guide to fish and fillets of the South East Fishery (SEF) quota species groups has been compiled from new information. This reference, South East Fishery.Quota Species: an Identification Guide (Daley et al., 1997) and hereafter referred to as SEF Species Guide, was...
ORGANISATION:
CSIRO Oceans and Atmosphere Hobart
TAGS
Population Dynamics
Physiology
Nutrition
Individual Transferable Quota
Fishing Effort
Environment
Industry
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