ECASA WP 2
Friday, 17 December 2004
Annotated sheet for indicators1
related to the impact of aquaculture on the environmenti
1- Name of indicator, authors
Infaunal Trophic Index (ITI)
Not widely accepted as an indicator of impact but may merit further testing. Used partly in
Scottish regulatory monitoring surveys and modelling and tested in North American waters.
Word (1979); Mearns and Word (1982)
From SAMS
2- Computation: Formulae, or model output.
Whenever possible, please use a range of 0-100. Ranking the results in few classes (five?) is
another option for qualitative indicators.
ITI (range 0-100) has been tested to some extent for assessing the impact of aquaculture:
ITI = 100 - 33.3 (
0 N1+1 N 2 + 2 N3 + 3 N4
N1+ N 2 + N3 + N4
where Ni is abundance of organisms in trophic group i. See text below for explanation.
3- List of data / parameters required for computation.
Sampling and identification of benthic macrofauna community as described for Annotated
sheet on Macrofauna univariate statistics. Categorisation of species identified into trophic
groups using a published list (WRc, 1992) and determination of abundance in each trophic
group so that formula above can be applied.
4- Description of scientific meaning, references
The purpose of the Infaunal Trophic Index (ITI) is to describe the feeding behaviour of soft
bottom benthic communities in terms of a single understandable parameter. These animals
fall into four groups; they are either suspension or deposit feeders that feed above, on or
below the mud surface. The ITI was developed in California, USA and was first published in
1979 (Word, 1979). Since then it has been adapted for use in UK waters (WRc 1992) but the
principles remain the same. Invertebrates have been divided into four groups based on what
type of food is eaten, where it is obtained and how it is obtained. ITI trophic group 1 are
suspension feeders (e.g. Mya arenaria), group 2 are surface detritus feeders, group 3 are
surface deposit feeders and group 4 are sub–surface deposit feeders (e.g. Capitella capitata).
References:
1
Please return these sheets to the WP 2 leader, BEFORE end of March 2005.
Dauer, D.M. 1984. The use of polychaete feeding guilds as biological variables. Marine
Pollution Bulletin 15: 301-305.
Levinton, J.S. 1991. Variable feeding behaviour in three species of Macoma (Bivalvia:
Tellinascea) as a response to water flow and sediment transport. Marine Biology 110:
375-383.
Maurer, D., H. Nguyen, G. Robertson and T. Gerlinger, 1999. The infaunal trophic index
(ITI): its suitability for marine environmental monitoring. Ecological Application 9:
699-713.
Mearns, A.J. and J.Q. Word. 1982. Forecasting effects of sewage solids on marine benthic
communities. In: Ecological Stress and the new york Bight: Science and
Management. (ed mayer) GF. Columbia S. Carolina Estuarine Research Federation.
pp. 495-512.
Word, J.Q. 1979. The Infaunal Trophic Index. In, Annual Report 1978. Coastal Water
Research Project, El Segundo, California, USA, pp. 19–39.
Word, J.Q. 1980. Classification of benthic invertebrates into Infaunal Trophic Index feeding
groups. In, Coastal Water Research Project Biennial Report 1979–1980. SCCWRP,
Long Beach, California, USA, pp. 103–121.
WRc plc 1992. Development of a biotic index for the assessment of the pollution status of
marine benthic communities. WRc report no. SR2995.
5- Range of validity; please provide a description of the field of validity for the
indicator, its limits, endpoints. Careful explanations should be given in a table
about the correspondence between the computed values and the impact (from
positive effect, no impact , moderate impact, high impact, unacceptable impact).
Tested mostly for soft sediment communities and known to have limitations for coarse
sediment communities. In addition, ITI needs to be interpreted with care when diversity is
low (e.g. number of species ≤ 5).
ITI
> 50
20 – 50
< 20
Description of community (general definition from sea loch data sets)
little effect
enriched
degraded
6 -Type of aquaculture on which this indicator applies
ALL
7 - Relevant environments for this indicator
Soft sediment communities (further testing in coarse sediments required)
8- Quotation. We will need to select the most appropriate indicators to be proposed for
EIA and site selection. Please suggest a quotation for this indicator for the following
criteria (from A, perfectly adequate, to E, not relevant), to help evaluating the
indicator within WP 4. Additional comments are welcome.
 Direct relevance to objectives :
C – Used in Scottish regulation but not widely accepted

Clarity in design : It is important that the selected indicators are defined clearly in
order to avoid confusion in their development or interpretation. – C - The list which
assigns species to trophic groups exists for some environments but is a point of debate
Species will change feeding mode due to the quality and quantity of food available
and therefore species may occupy different trophic groups according to conditions.
This effects the value of the index (Levinton 1991; Maurer et al., 1999; Dauer, 1984).

Realistic collection or development costs : Indicators must be practical and realistic,
and their cost of collection and development therefore need to be considered. This
may lead to trade-offs between the information content of various indicators and the
cost of collecting them. – C - Main limitation is the cost of macrobenthic surveys and
subsequent identification to species level similar to annotated sheet on Macrobenthic
univariate indices. There is an additional cost/time in categorising species into trophic
groups. Where the information does not exist for a particular species, the user will
need to make an informed decision as to which group the species occupies.

High quality and reliability : Indicators, and the information they provide, are only
as good as the data from which they are derived. – C – Quality and reliability variable
depending on limitations previously described with trophic groups and environment.

Appropriate spatial and temporal scale : Careful thought should be given to the
appropriate spatial and temporal scale of indicators. – B – Appropriate for assessment
of spatial and temporal gradients

Obvious significance : The meaning and usefulness of the indicator should easily be
understood by stakeholders. B – Summarises information into a single understandable
index. Differences between species in trophic group 1 (suspension feeders) and trophic
group 4 (deposit feeders) and the effect of the relative abundances of these groups on
the value of the index can be easily explained to stakeholders. In addition, limitations
can be easily explained to stakeholders.
9- Data and models related to this indicator, available for use by WP 4. Please list the
data and models output available at local, national or regional scales for use by ECASA.
They may not correspond to the more theoretical list asked for in §3.
Numerous data sets collated by SAMS for assessment of North Atlantic salmonid farms.
DEPOMOD model (Cromey et al. 2002) contains relationship between solids flux arising
from salmonid fish farms (g solids m-2 bed yr-1) and ITI.
Cromey, C.J., Nickell, T.D. and Black, K.D. (2002). DEPOMOD - modelling the deposition
and biological effects of waste solids from marine cage farms. Aquaculture, 214, 211239.
10- Suggestions for use by WP 5. Give examples of indicators/aquaculture/environments
which can be field-tested during the course of WP 5.
All aquaculture types above soft sediment environments can be assessed using this
indicator.
0.1 m-2 van Veen grab or corer taking duplicate grabs along an organic gradient with
samples taken at reference stations.
There is a trend in Scottish regulation towards positioning sampling stations on a site
specific basis, rather than using a nominal distance between stations (e.g. 0, 25, 50 m
from cages etc). This new system locates sampling stations, assisted partly by modelling,
close to the boundary of the Allowable Zone of Effect (AZE). This aims to measure
where the zone of effect of the farm ends (along the main axis of current) and is
supplemented with the usual adjacent to cage sampling station. The change in benthic
community between near cage and boundary is of less interest. A second transect
perpendicular with the main axis of current is not required. Such a sampling station
arrangement could be tested in WP5.
This document is intended to be used for internal work on ECASA workpackage. The final
indicator sheet may include a format somewhat different. Please suggest any improvement for
both the content and the form of this document.
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