27 results
Environment
Environment
PROJECT NUMBER • 1994-148
PROJECT STATUS:
COMPLETED

The age composition of ling catches

Ling (Genypterus blacodes) catches are an increasing component of the South East Fishery. There is increasing pressure to raise the trawl sector TAC for ling and there has been a substantial increase in catch by the non-trawl sector, particularly line, which is currently unregulated. Despite the...
ORGANISATION:
Agriculture Victoria
Environment
Environment
Environment
PROJECT NUMBER • 1995-032
PROJECT STATUS:
COMPLETED

Age Composition of orange roughly in the eastern and southern management zones

Orange roughy is an important species in the South East Fishery (SEF). The main areas in the SEF where orange roughy fishing has occurred are a major spawning aggregation off the east coast of Tasmania (the Eastern Management Zone) during winter and on non-spawning summer aggregations of the...
ORGANISATION:
Agriculture Victoria
Environment

Movement and re-aggregation of blacklip abalone in response to intensive fishing

Project number: 1995-165
Project Status:
Completed
Budget expenditure: $116,068.00
Principal Investigator: Harry Gorfine
Organisation: Agriculture Victoria
Project start/end date: 28 Jun 1996 - 29 Sep 1998
Contact:
FRDC

Objectives

1. To determine the extent of migration and re-aggregation of a blacklip abalone population in response to fishing
2. To describe differences between pre and post-fishing spatial distribution patterns in blacklip abalone population
3. To determine the growth rates of a "stunted" abalone sub-stock

Final report

ISBN: 0 7311 4207 1
Author: H.K. Gorfine R.A. Officer C.D. Dixon
Final Report • 1998-09-10 • 2.09 MB
1995-165-DLD.pdf

Summary

Typically abalone are found clustered into aggregations of many individuals along gutters and ledges that dissect the surfaces of the reefs they inhabit. Commercial abalone divers take advantage of this clustering behaviour and specifically target aggregations to minimise the time spent searching for abalone and maximise their catch rates. This approach to abalone harvesting would be expected to progressively reduce the number and size of the aggregations to produce a less clustered pattern of distribution. Most methods used to detect changes in abalone abundance that result from fishing assume that abalone movement will have minimal effect on post-fishing patterns of distribution.

Abalone are generally viewed as relatively inactive organisms that occupy specific homesites from which they seldom move. Evidence for this lack of movement includes the oval shaped 'scars' of bare rock, free of algae and other immobile invertebrates, that remain after abalone are harvested. However there are many anecdotes describing the tendency for abalone to reform aggregations after fishing and during spawning periods. Presumably the latter promotes fertilisation success by increasing the quantities of sperm and eggs that mix in the water. It is unclear why abalone may aggregate into clusters outside spawning periods. If re-aggregation does occur after fishing, it is also unclear where these 'replacement' abalone come from. There is some speculation that small abalone may emerge from crevices and cryptic habitat. Other hypotheses include small-scale movements within aggregations or migration from unfished areas. An understanding of how re-aggregation occurs after fishing and to what extent it occurs, is essential to determine its effect on estimates of abalone abundance and to estimate important population characteristics such as rates of natural mortality.

Keywords: Haliotis rubra, abalone, dispersal, movement, aggregation, natural mortality, tag-loss, tag-recapture, stunted, growth.

Environment
PROJECT NUMBER • 1983-032
PROJECT STATUS:
COMPLETED

Port Phillip Bay and Bass Strait scallop research

During the 3 years of the study, scallop spatfall was observed to occur over a short period (October-December) after the scallops had spawned in spring. Growth was rapid and scallops reached an acceptable harvestable size of 70mm within 16 months. Spatfall one year can therefore be related to...
ORGANISATION:
Agriculture Victoria
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