65 results
Environment
Communities
PROJECT NUMBER • 2014-226
PROJECT STATUS:
COMPLETED

Indigenous Fishing Subprogram: Improving the recognition and integration of traditional owner customary fishing and ecological knowledge in the management of Victoria’s fisheries

With growing recognition of Traditional Owner groups across Victoria as native title claims are being resolved. There is a strong interest from within Victorian Traditional Owner community to actively participate in the management of Victoria’s fisheries. However, despite these strongly held...
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
:

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
Industry

Evaluation of methods to assess abalone abundance

Project number: 1993-100
Project Status:
Completed
Budget expenditure: $166,101.00
Principal Investigator: Harry Gorfine
Organisation: Agriculture Victoria
Project start/end date: 14 Nov 1993 - 25 Mar 1999
:

Objectives

1. To compare methods of abundance estimation in determining the effects of stock depletion by pulse fishing a stunted backlip abalone population.

Final report

Author: Harry Gorfine
Final Report • 1996-07-29 • 1.30 MB
1993-100-DLD.pdf

Summary

The issue of how best to survey abalone populations to obtain estimates of abundance has been the subject of debate among fisheries biologists for many years.  In an attempt to resolve this issue we compared and evaluated abalone abundance estimated by the following methods: Transect survey, Timed-collection surveys, Mark-Recapture, Change-in-Ratio and Leslie (catch-effort) estimates. This study involved a fish-down of an abalone reef by commercial abalone divers.  Estimates of abalone abundance were made by applying the different methods before, during and after the fish-down.  The total catch (number of abalone harvested) was used as a bench-mark against which the differences between the before and after abundance estimates for each method could be compared.  In addition the precision for each method was estimated and compared.

Previously, the use of area-based transects was thought to be limited for estimating the abundance of spatially aggregated animals such as abalone.  However, the outcome of this study was that transect surveys are the preferred method because they accurately reflected absolute abundance, required a relatively small number of sampling days and were reasonably precise.  It is recommended that a stratified random approach be adopted when using transect sampling.  Timed-collections gave precise but inaccurate estimates of abundance which were somewhat more sensitive to diver (operator) effects.  CIR methods using transect data to estimate proportions can be as efficient as transect-based abundance estimates, however they require more intensive data collection.  If a cost-effective and quick tagging method can be identified, then a mark-recapture study will also work well, although a test for equal catchability of tagged and untagged animals should be included in the design of the experiment.  CIR analysis using timed collection data is less certain due to possible violation of equal catchability of two animal types, but will still give a workable result.  The use of catch and effort data as an index of abundance is not recommended for monitoring abalone abundance because, despite the controlled conditions during this study, estimates of abundance using these data could not be obtained in two out of three instances.

Future research should be directed towards a better understanding of the importance of aggregating behaviour in determining the impact of harvesting on blacklip abalone populations.  The involvement of commercial abalone divers is crucial to the success of these types of studies.  For this project, co-operation between managers, researchers and commercial divers was beneficial to all parties involved and it is hoped this will become a common occurrence in future research of the Victorian abalone fishery.

Environment
Industry
View Filter

Organisation