SARF090 - Impacts of salmonid pen aquaculture on hard substrates

493 Pages·2012·4.05 MB·English

SARF090
Impact of Salmonid Pen Aquaculture on Hard Substrates
A REPORT COMMISSIONED BY SARF
AND PREPARED BY
ABP Marine Environmental Research Ltd
Institute of Aquaculture, University of Stirling
WRc plc
Published by the: Scottish Aquaculture Research Forum (SARF)
This report is available at: http://www.sarf.org.uk
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Suggested Citation:
CA Roberts1, TC Telfer2 ,I Johnson3, DJ Honey1, FM Miller1, E, Aldous3, HM Tillin1and SC Hull1,
2014. Impact of Salmonid Pen Aquacultureon Hard Substrates. A report by ABP Marine
Environmental Research Ltd.1, Institute of Aquaculture, University of Stirling2and WRc plc3for the
Scottish Aquaculture Research Forum.
1ABP Marine Environmental Research Ltd., Quayside Suite, Medina Chambers, Southampton,
SO14 2AQ
2Institute of Aquaculture, School of Natural Sciences, University of Stirling, Stirling, FK9 4LA
3WRc plc, Frankland Road, Blagrove, Swindon, SN5 8YF
Title: Impact of Salmonid Pen Aquaculture on Hard Substrates
ISBN:978-1-907266-61-4
First published:April 2014
© SARF2014
Scottish Aquaculture Research Forum

SARF090: Impact of Salmonid Pen Aquaculture
on Hard Substrates

Report R.2127

January 2014

SARF090: Impact of Salmonid Pen Aquaculture on Hard Substrates

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SARF090: Impact of Salmonid Pen Aquaculture on Hard Substrates

Executive Summary

Future increases in the extent of marine salmonid aquaculture in Scotland are likely to require
expansion of the industry into new locations in addition to the extension of existing pen sites. The trend
is for new sites to be considered in more exposed locations than existing sites, where the higher energy
nature of the locations may be reflected in the presence of hard substrate benthic habitats and
associated species. Alternatively potential new sites may be located over hard substrate benthic
habitats in more sheltered lower energy environments. However, less is known about the impacts of
aquaculture emissions on the features and species of conservation importance within these ‘hard
substrate’ habitats, compared to the soft sediment habitats of most current aquaculture sites. As such,
the present study was commissioned by the Scottish Aquaculture Research Forum (SARF) to
undertake the following:

 A review of the biological impacts of emissions from all forms of industrial activity on subtidal
hard substrate features (habitats and associated species), including recommended methods of
assessing the effects on an ongoing basis, and recommending further research where
necessary to fill current knowledge gaps;
 An assessment of how the Environmental Quality Standards (EQS) (or operational Predicted
No Effect Concentrations (PNECs)) currently in use by SEPA have been derived, in relation to
their applicability to all the possible hard substrate features that might be encountered in
Scottish coastal waters, that are relevant to aquaculture development;
 A review of guidance, case law and practical case studies relating to developments in Europe
where designated features may be present within the proposed development footprint; and
 A review of the available sources of information on the extent of hard substrate features around
the coasts of Scotland, how this information can be accessed and techniques, sampling
protocols and indicative costs that could be used to collect data where information gaps
currently exist.

Biological Knowledge Relating to Effects of Industry Emissions on Marine Hard
Substrate Features

For the purposes of this study, ‘hard substrate’ habitats have been considered to comprise subtidal
rocky reefs, boulders and cobbles in the infralittoral and circalittoral zones and biogenic reefs. The
review considered the effects of pressures which may arise from salmonid pen aquaculture (siltation,
organic enrichment of sediments, deoxygenation of sediments, nutrient enrichment of the water
column, deoxygenation of the water column, non-synthetic (heavy metal) and synthetic compound
contamination of the water column and sediment, surface abrasion and physical change in seabed
habitat) on hard substrate habitats and species of conservation interest which occur within these broad
scale habitats.

In general, evidence suggested that nutrient enrichment of the water column arising from the emission
of dissolved nutrients from fish farms, and related secondary effects such as eutrophication,
deoxygenation of the water column and increased occurrence of harmful algal blooms, are not major
issues for marine fish farms in their current relatively sheltered locations. Hence this pressure is not
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considered likely to be an issue for potential new sites located over benthic hard substrate habitats in
low to moderate energy environments, while in higher energy more exposed locations , the magnitude
of this pressure would be expected to decrease further.

Siltation and subsequent smothering effects, organic enrichment and deoxygenation will only occur
where particulate waste (i.e. uneaten food and faeces) accumulates or becomes trapped. This was
judged less likely to occur in higher energy more dynamic environments, although some evidence from
sedimentary habitats indicates that ‘enrichment’ pressures are still relevant in higher energy
environments. Very little direct evidence was found of siltation impacts on hard substrate features. One
study in a macrotidal estuarine environment in England recorded the species present on large cobbles
and small boulders on a 50m transect downstream of a fish farm, however, insufficient data was
available to assess the significance of any effects of the fish farm on the distribution of these species.
Evidence of anthropogenic-related increases in sedimentation (not specifically from aquaculture) having
detrimental effects on several algal species in rocky subtidal habitat, has been provided by studies in
the Mediterranean, although it must be noted that tidal currents are generally very weak in the
Mediterranean compared to those in Scottish waters. With regard to the effects of heavy metal and
chemical contamination, a few studies were identified which had assessed the concentrations of metals
or chemicals in naturally occurring blue mussel populations in the vicinity of fish farms. However, the
majority of evidence related to laboratory toxicity or bioaccumulation studies or anecdotal observations
of the presence of hard substrate features (Horse mussels and Serpulid reefs) occurring in areas with
high levels of heavy metal contamination. Furthermore, very little information relating to impacts of
emission-related pressures from other marine industries on hard substrate habitats and species was
available to fill these data gaps.

As such, it has been concluded that there is a paucity of direct evidence (i.e. data from field studies) of
impacts of aquaculture-related emissions on hard substrate habitats and associated biological
communities, which is due to the lack of spatial overlap between fish farms and hard substrate habitats
and species to date. Evidence of environmental impacts from fish farms located over sedimentary
habitats, in both sheltered and more exposed locations, may be used to infer potential impacts on hard
substrate habitats and species, however, this increases uncertainties in relation to the impacts of some
pressures. In particular, a greater understanding is required of the dispersion of particulate waste in
higher energy environments and the sensitivity of hard substrate receptors to siltation and non-synthetic
and synthetic contaminants if the local hydrodynamics lead to the deposition and accumulation of
particulate waste on hard substrate features. The development of sediment based communities on hard
substrates within smothered areas (which would require colonisation by ‘pollution tolerant’ infauna
characteristic of sediments directly underneath fish farms in current locations) will have implications for
succession and eventually for recovery on cessation of fish farming and more research is needed in
this area.

Review of Environmental Survey Methods for Hard Substrate Seabeds

Studies of hard seabed environments are complex and often have technical limitations which are not
present when considering sedimentary habitat, which allow direct sampling and subsequent analysis in
controlled laboratory conditions. The survey of hard substrate seabeds is largely visual in nature with
quantitative analysis being performed in situ by divers or post hoc on photographic or video images.
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However, there is little standardisation of underwater survey methods and it is important that any survey
method adopted to monitor the impacts of aquaculture on hard substrate habitats and associated
communities is standardised and has an associated quality scheme to enable effective comparison for
monitoring purposes. Such standardisation and quality assurance is currently being undertaken by the
National Marine Biology AQC scheme for underwater image collection and analysis.

Although some current monitoring methods are applicable to aquaculture sites located over hard
substrates, for example, water column sampling to assess compliance with EQS, other current methods
for environmental monitoring (e.g. modelling of solid waste distribution, the use of infaunal organisms
as indicators and sediment sampling using standard collection devices) may not be wholly applicable to
hard substrates. Therefore alternative monitoring techniques will be required. Initial recommendations
have been made regarding the types of survey methods and parameters that could be used to monitor
the effects of fish farms located over hard substrates.

Review of EQS

The applicability of the current EQS or operational PNECs for chemicals (sea lice therapeutants,
antibiotics, antifoulants and in-feed nutrients) used in Scottish aquaculture to subtidal hard substrate
features was reviewed. In particular the review considered the relevance of the taxonomic groups (e.g.
algae, invertebrates) on which the EQSs or PNECs are based, whether the derivation was consistent
with the requirements of the Water Framework Directive (in-particular the approach described in
Guidance Document No 27 under the Common Implementation Strategy (CIS)) and whether any
additional data relevant to the EQS/PNEC derivation process had become available since the values
were derived. A theoretical risk assessment (in relation to short-term effects in the water column) was
then undertaken to assess the level of ‘protectiveness’ of the EQSs/PNECs based on the likely
exposure to the chemicals and the potential for cumulative effects.

The review highlighted that for all of the chemicals assessed, except the antibacterial agent florfenicol,
the absence of data on the toxicity to some characteristic groups associated with hard substrates does
not affect the protection afforded by EQSs/PNECs. This is because either data were available for the
group that were expected to be the most sensitive to the substance (based on its mode of action)
and/or the characteristic groups associated with hard substrates are evidently not the most sensitive to
the identified substances. The absence of data on the toxicity to characteristic species associated with
hard substrates for florfenicol may potentially affect the protection afforded by the current PNEC for this
substance. This is because it is possible that these species may be most sensitive to this substance.
However, it should be noted that the current operational PNEC for florfenicol is considered to be
overprotective based on the available data. Therefore, even if the PNEC for this chemical was revised
to include data for hard substrate or soft substrate receptors, the level of actual exposure to this
chemical in the marine environment would not give rise to a significant risk as the risk assessment (for
another antibiotic) indicated that the predicted environmental concentrations are well below the current
PNEC. Hence any revision of the current PNEC would not have any implications for the use of this
substance.

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A similar situation would apply for the sea lice therapeutant hydrogen peroxide where the current
operational PNEC is considered underprotective based on currently available data but the potential risk
from its use is considered to be low. Saltwater EQS derived under the Water Framework Directive for
cypermethrin, copper and zinc will supersede the current EQS for marine waters if, and when, they are
adopted by the UK’s regulatory agencies.

The short-term risk assessment used a theoretical scenario, which was conservative in design as it
only considered initial dilution and not dispersion of chemical emissions, and indicated that the current
EQS or PNEC values for each chemical are considered to be protective (i.e. there is no likelihood of
significant effects) of hard substrate receptors following exposure. With regard to potential cumulative
effects, under the theoretical scenario, the risk assessment suggested that for specific combinations of
treatments it is feasible (although unlikely) that there could be a temporary and localized exceedance of
a risk ratio of 1 (i.e. that there is the potential for cumulative effects on hard substrate receptors).
However, given the fact that dispersion was not accounted for in the scenarios and highly conservative
estimates of the concentrations of the chemicals in the water column were used in this assessment, this
effect, if it occurs, would be transient and not of significant concern. Risk assessments were not
undertaken in regard to sediment EQS as it it is not clear from the available biological review data
whether exposure of hard substrate features and species to the identified chemicals of concern via the
sediment is a significant route of exposure. It is considered that further research should be directed
towards understanding the nature and extent of the deposition of particulate matter on hard substrate
features and subsequent chemical contaminant pressures.

Review of European Approach to Development and Designated Features

Projects or plans affecting areas in or near sites designated as Special Protection Areas (SPAs) under
the EU Wild Birds Directive or Special Areas of Conservation (SACs) under the EU Habitats Directive,
are subject to the requirements of Article 6 of the Habitats Directive. There is an extensive body of
guidance relating to implementation of these Directives in relation to plans and projects, which sets out
a clear procedure to be followed, underpinned by case law defining how the process needs to be
interpreted and applied.

Some guidance documents provide lists of indicators/parameters which may be useful when assessing
the likelihood of significant effects during the appropriate assessment screening stage and for
assessment of the likelihood of adverse effects on features and site integrity during the appropriate
assessment process. However, there is no guidance, case law or case study precedent relating to
thresholds or targets which signify an adverse effect. On the contrary, recent Scottish Natural Heritage
(SNH) guidance, literature and case studies indicate that the use of specific percentage thresholds to
assess significance or assess impacts in relation to conservation objectives are of limited value and
cannot be scientifically supported at the current time. As such consideration of potential salmonid pen
aquaculture developments in, or in the vicinity of, designated sites and features should continue to be
judged on a site by site basis with regard to the conservation objectives of that site.

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Information on Distribution of Hard Substrate Features in Scottish Waters

There are numerous sources of publically available information on Scotland’s nature conservation
designated sites and the distribution, extent and quality of subtidal hard substrate features in Scottish
inshore waters. How these sources of information can be accessed, how frequently they are updated
and the type of data available has been summarised in a ‘factsheet’ designed to be useful tool for both
the aquaculture industry and regulators as sites for new fish farms are considered. Limitations of the
data currently available relate to the ‘patchy’ coverage of surveys undertaken in inshore waters and the
‘level’ to which habitats are identified. However, ongoing survey work in Scotland to support the MPA
process will improve the coverage of inshore data and information on how this data will be made
available is presented.

Summary and Recommendations

The review has highlighted considerable data and knowledge gaps on the impacts of marine
aquaculture on hard substrate habitats and species around Scottish coasts. These data gaps include
information on the sensitivity of epibiotic species to effluents from marine fish farms and gaps in the
knowledge of spatial distribution of biotopes related to hard substrates within Scottish inshore waters,
including in areas where future aquaculture developments may occur.

Filling these knowledge gaps can be categorised under two approaches:

 Laboratory assessment of the toxicity of aquaculture chemicals to hard substrate epibiota and
in situ field studies to investigate any community level and longer term impacts of aquaculture
related emissions on hard substrate communities; and
 Standardised survey methods to further map the distribution of hard substrates in inshore
waters and characterise the associated fauna/flora and communities (biotopes).

Furthermore, data generated by these two approaches can be used in the development of new, or
further development of existing, regulatory models of waste distribution for the different hydrodynamic
conditions which may be associated with hard substrates. Recommendations relating to appropriate
survey methodologies or approaches to fill these data gaps have been made. Indicative costs have
been provided where information was available.

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