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Factors related to the sustainability of shellfish aquaculture operations in the Firth of Thames: a preliminary analysis

TR200209

Report: TR 2002/09

Author: N Broekhuizen, J Zeldis, SA Stephens, JW Oldman, AH Ross, J Ren & MR James (NIWA)

About this report

Over the past decade shellfish farming operations in New Zealand have grown rapidly. Most of this growth has been in the cultivation of the greenshell mussel, Perna canaliculus, though significant numbers of Japanese oyster Crassostrea gigas are also farmed.

In the year 2000, approximately 2500 ha of New Zealand’s coastal seabed were allocated to mussel production (Inglis et al. 2000), yet there are pending applications for approximately 6000 ha of mussel farms within the Firth of Thames alone. Furthermore, many of the pending applications for the Firth of Thames (and elsewhere in New Zealand) are for farms which are at least an order of magnitude larger than any farm presently operating in New Zealand. Development of marine aquaculture operations has been regulated by regional authorities through application of the Resource Management Act; however, to date this has tended to be an ad-hoc process with few formalised guiding principals.

Central government has recently proposed a two year moratorium upon further aquaculture development in order to provide an opportunity in which: (a) government and regional authorities can commission the research which they deem necessary to improve the scientific foundations upon which judgements of sustainability are to be made, and (b) develop appropriate zoning policies and aquaculture management areas (AMAs) for their coastal waters.

This report aims to

  • review relevant data on the Firth of Thames
  • highlight issues which are specific to the Firth of Thames
  • discuss approaches to the assessment of the sustainability of aquaculture – with emphasis on the types of data and models which are required
  • provide an initial assessment of sustainability of aquaculture within the Firth of Thames, based upon data which are currently available
  • provide examples of what further improvements upon the initial assessment might be gained with additional funding (using presently available tools)
  • summarise the data and modelling requirements for an improved estimate of the impacts of aquaculture in the Firth of Thames
  • develop a research plan to yield the required additional data and enhanced numerical models which will make it possible to derive more robust estimates of the sustainability of aquaculture activities within the Firth of Thames.

Read or download the report

Factors related to the sustainability of shellfish aquaculture operations in the Firth of Thames: a preliminary analysis [PDF, 3.8 MB]

Contents
  Executive summary 
1 Introduction
1.1 Aims and structure of this report
1.2 Terminology
1.3 Review of documented aquaculture impacts
2 Review of present data
2.1 Physical characteristics
2.2 Mixing fluxes of water and nutrients
2.3 Physical processes and primary production in the Firth of Thames
2.4 Secondary production in the Firth
2.5 Facecal contaminants
3 Issues specific to the Firth of Thames
4 Approaches to assessing carrying capacity and sustainability
4.1 Definition of characteristics
4.2 Definition of thresholds
4.3 Definition of statistical tests
5 Assessment of sustainaibiilty based upon present knowledge
5.1 Physical carrying capacity
5.2 Production carrying capacity
5.3 Ecological carrying capacitgy
5.4 Flushing times within the Firth of Thames
6 Depletion estimates
6.1 Introduction
6.2 Results
6.3 Discussion
7 Scoping of research leading to an improved estimate of the sustainability of shellfish aquaculture within the Firth of Thames
7.1 Site specific issues
7.2 Generic issues
8 Summary and conclusions
9 Appendices
10 References