Funded Activity Summary
The need for this project arises from a number of directions. Firstly, the Exmouth Gulf region of the fishery (Zone 1) is currently experiencing a very high exploitation rate. In a review of the Zone 1 fishery in 1997, a lack of knowledge of length-fecundity relationships and Natural Mortality rates for MOP was highlighted. As a result of a high exploitation rate, it was hypothesized that the flow through of recruits to the MOP stock may be less than the Natural Mortality Rate of the MOP stock, thus placing a long-term risk on the breeding population. Therefore research into MOP stock dynamics was identified to be of critical importance to maintaining the sustainability of the harvest regime in Zone 1.
Second, there is the long-term strategic need to find an alternative supply of large nuclei to counteract the declining source from the American Freshwater Mussel industry. In anticipation of demands for harvesting of MOP for nuclei, there is an urgent need to start gathering information, to enable a sustainable harvesting regime for MOP to be implemented in 3 years time. Most likely this will result in the setting of an appropriate quota for MOP, within the current TAC allocation mechanisms in zone 2 or 3 where MOP stocks have built up.
In order to implement sustainable harvesting, we need to address a number of uncertainties. First, what is the extent of MOP stocks with respect to overall numbers of pearl shell. Secondly, what are the rates of recruitment into, and natural mortality of, the MOP stocks. These data, combined with knowledge of stock size, particularly with reference to the culture shell, will enable rates of sustainable harvest to be estimated. Finally, what is the impact of harvesting of MOP on recruitment. Recently, for example, there is good evidence from catch rate data of increased recruitment at two spatially distinct areas, 80 Mile Beach and the Lacepede Islands. Whether this has been environmentally and/or stock driven is currently undetermined, although recent data suggests a considerable environmental factor in the central area (Zones 2/3) of the fishery.
Another identified strategy for sustainable management of MOP is relocation of MOP to better growth areas. Obviously the quality of MOP shell will determine the amount of nuclei which can be produced. There is some anecdotal information suggesting that MOP shell from different areas have different quality of shell, and there is the possibility that shell growth and quality may be improved by transplanting to these areas. Ultimately, after establishing the parameters for natural mortality, fecundity, and recruitment in MOP populations, there is the potential to undertake: a) a one-off, large-scale stock survey of MOP, and b) investigate the possibility of re-locating hatchery produced shell, after they have grown too large for culturing pearls, into areas to grow to a suitable MOP size.
Objectives:
1. The overall objective of the study is to obtain scientific information to: a) allow assessment of the status of MOP stocks in Zone 1; b) investigate the nuclei production quality of MOP within Zones 2 and 3, and c) allow the setting of sustainable harvest levels for MOP within each Zone of the WA Pearl fishery.Specific objectives of the project are:1. To determine growth, natural mortality, and size-fecundity parameters in MOP.2. To determine the distribution and abundance of 'nuclei quality’ MOP.3. To determine the effects of location and depth on the biofouling and overall quality of MOP.4. To undertake a preliminary assessment of the effects on growth and mortality, of transplanting MOP to quality areas.5. To develop a protocol for setting quota of MOP.
Funded Activity Details
Start Date:
21-06-1998
End Date:
02-09-2004
Funding Scheme:
Funding Scheme not available
Funding Amount:
$375,210.41
Funder: Fisheries Research and Development Corporation