In situ biofilters at commercial fish farms in Scotland the effectiveness of mussel lines as biofilt

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In situ biofilters at commercial fish farms in
Scotland the effectiveness of mussel lines as
biofilters
EJ Cook, KD Black MDJ Sayer (SAMS)
BIOFAQs Workshop, Eilat (October 2002)
EU 5th Framework BIOFAQs BIOFiltration
Aquaculture Q5RS-2000-30305 Website
www.sams.ac.uk/biofaqs
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Introduction

• Question Mono vs multi-species communities?
• Use of active suspension feeders (e.g. bivalve
  molluscs ascidians)
• Use of species of commercial value

Fish Farm Site, Lynne of Lorne
Scallop farm, Loch Fyne
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Active Suspension Feeders
Expend energy to drive sea water and suspended
seston across the filtration surface using
ciliary or muscular pumps.

• Retains particles 1 100 ?m (incl. bacteria,
  diatoms, other phytoplankton non-living
  detritus)
• Ascidiella aspersa dominant ascidian on
  biofilters in Oban
• Attained biomass of 86.12 28.08g (AFDW m-2)
  after 5 months
• Clearance rates (ml g dry mass-1 h-1) 3180
  (Holmes, 1973) 3240 (Randløv and Riisgård,
  1979).
• Commercial value Unknown potential high
  pharmaceutical value

• Retains particles lt1 ? ?m (incl. bacteria,
  phyto-, zoo-plankton and particulate detritus)
• Mytilus edulis dominant bivalve on biofilters
• Attained biomass of 3.45 0.38g (AFDW m-2) after
  5 months
• Clearance rates (ml g dry mass-1 h-1) 700
  5300 (Prins et al. 1996).
• Commercially valuable seafood product

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Construction/Deployment
Mussel lines (ML) were constructed from 1m
lengths of DANLINE mussel spat polypropylene
rope. Each rope was weighted at one end to
ensure that the rope remained vertical in the
water column.
The MLs were deployed in Oban at a fish farm (10
m from cages) and a control site (500 m from the
salmon farm) in 25 May 2002. Each line was
suspended at a depth of 10 m and at a distance
apart of 0.25 m.
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Methodology
Sampling protocol Bi-monthly intervals for 18
months.
Video Survey
Mussel Line (Control Site - Sept 2002)
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Video Survey
Fish Farm
Control
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Total Biomass
Data for mussel lines represents n1, whereas
n4 for mesh data
A - July 2002 B - Sept 2002
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Species Diversity
4 months post deployment
Ascidiella aspersa
Mytilus edulis
Caprella linearis
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Comparative Studies
Comparisons made after 4 months of deployment
(Mussel Lines 2002)
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Conclusions

• Still early days
• Significant colonisation of mussel lines (MLs)
  within 4 months
• Total biomass is comparable to the mesh
  filters, although higher biomass is observed on
  the MLs at the control site compared to the fish
  farm
• Reduced species number on the MLs compared to
  mesh filters
• Increased abundance of Mytilus edulis and
  Caprellidae at fish farm compared with control
  site on the MLs

• Need for mesocosm trials using mussel lines
  colonised by M. edulis from Loch Creran (2003?)
  for comparison with environmental data collected
  in Sept. 2002

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Acknowledgements
Simon Thurston (Diving Video Footage) Alex Keay
(Aquarium and construction)
Seabird CTD
Zooplankton sampling
sampling by day and night!!