Empowering Industry R,D&E: an analysis of water, sediment and biological samples from the Clarence River to identify potential causes for poor growth of school prawn during 2009/10

Funded Activity Summary

On 14 December the Clarence River estuary prawn trawl fishermen made a ‘gut wrenching’ decision – they closed the River and Lake Wooloweyah to prawn trawling until January 4. This at a time when harvest rates should be peaking to meet the demand for the school prawns over the Xmas and New Year period. The reason for the decision was based on the small size of the school prawn in the lake and river. It appears that they are not growing despite what seems to be ideal conditions. Following the major flood in May and a minor fresh in October it was expected that the up coming river trawl season would be a bumper.

For months there has been a problem with the size of the prawns in the river system. Although the reason is unknown, many theories are being proffered:

• high water temp (29 – 30 degrees) and maybe that is not conducive (too high) to the micro food the prawns eat;
• something left as a residue after the floods because the prawns are travelling when thy should not be (small ones going to sea);
• bream dying in crab traps;
• prawns are not separating into different class sizes as they usually do;
• flood mud on the banks from May that still has no grass growing on it in some places;
• pocket nets catching small travelling prawns when they normally catch a better grade of prawn;
• fish kill up the Coldstream River about mid November;
• eels dead in traps (South Arm) and look like they have been boiled;


Unless possible causes are eliminated and the likely problem identified then there could be ongoing impacts and a possibility that the prawn trawl season for the next few years affected.

Objectives:
1. Identify 18 key sites in the lower Clarence river for sediment and water sample testing
2. Engage a certified testing labarotory to sample and test these sites for a range of possible contanimants
3. Report on these test and results and determine a course in conjunction with relevant authorities of action if test results determine this

Funded Activity Details

Start Date: 08-06-2010

End Date: 30-09-2010

Funding Scheme: Funding Scheme not available

Funding Amount: $25,000.00

Funder: Fisheries Research and Development Corporation

Research Topics

ANZSRC Field of Research (FoR)

There are no FoR codes available for this funding activity

ANZSRC Socio-Economic Objective (SEO)

There are no SEO codes available for this funding activity

Other Keywords

Fisheries Management | Social Science | Stakeholder

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