Transcript No Slide Title

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
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
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 <1 – ? m (incl. bacteria,
phyto-, zoo-plankton and particulate detritus)
•Mytilus edulis dominant bivalve on biofilters
•Attained biomass of 3.45 ± 0.38g (AFDW m2) after 5 months
•Clearance rates (ml g dry mass-1 h-1) = 700 –
5300 (Prins et al. 1996).
•Commercially valuable seafood product
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.
Location of Biofilters
Methodology
Sampling protocol = Bi-monthly intervals
for 18 months.
1. Underwater video surveys
2. Removal of x4 MLs from fish farm and
control site
Video Survey
Mussel Line (Control Site - Sept 2002)
3. ML sampling (including total biomass &
species diversity/ abundance
Video Survey
Fish Farm
Control
Total Biomass
450
400
Biomass (DW g m-2)
350
300
Fish Farm
250
Control
200
150
100
50
0
Mesh 2mths_2001 ML7 2 mths_2002
Mesh 4
mths_2001
ML 4 mths_2002
Filter Type/ Year
*Data for mussel lines represents n=1, whereas n=4 for mesh data
A
A - July 2002
B - Sept 2002
B
Species Diversity
4 months post deployment:
Mussel Lines
Mesh Filters
• Species No. = 16 (FF) & 19 (CTL)
• Species No.= 23 (FF) & 21 (CTL)
• Dominant Species:-
• Dominant Species:-
FF – Mytilus, Caprellidae, Obelia &
Ascidiella
FF – Mytilus, Caprellidae, Obelia,
Ascidiella, Pectinidae
CTL – Obelia*, Ascidiella*,
Terebellidae*, Pinnotheres* & Mytilus
CTL – Ascidiella, Obelia, Pectinidae,
Terebellidae
Ascidiella aspersa
Mytilus edulis
Caprella linearis
Comparative Studies*
Abundance (No. ML-1)
250
200
150
FF
CTL
100
50
0
Obelia
Ascidiella
Mytilus
Terebellidae Caprellidae
Species
* Comparisons made after 4 months of deployment (Mussel Lines – 2002)
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
Acknowledgements
Simon Thurston (Diving & Video Footage)
Alex Keay (Aquarium and construction)
Seabird CTD
Zooplankton sampling
…sampling by day and night!!