consultancy and research in aquaculture and the aquatic environment

CONSULTANCY AND RESEARCH IN AQUACULTURE AND THE AQUATIC ENVIRONMENT

A Company in the NIVA-group

Monitoring survey type

Data collection

Hydrographic analyses

Water quality analyses

Chemical analyses

Benthic faunal analyses


Method and equipment usedecho-sounder and/or existing bathymetric mapseventual modifications to tide tablescurrent meterwind speed monitor current drift recordinghydrographic sensor

Data providedThe data obtained will reveal the bottom topography and any hidden features that might influence local hydrographic conditions. The data are further used to validate eventual waste dispersal models.

EffectivenessSuch hydrographic measurements are essential for baseline surveys/ monitoring of pre-licence sites. Most of the techniques can to advantage be applied to near- or in-cage monitoring to help optimise conditions for the ongrowing stock.


The dispersal of aquaculture discharges is dependent on the hydrographic conditions and water exchange mechanisms in the area. Environmental impacts on bottom substrates and the water column are minimised in areas with strong current flow. However, the degree of exposure must not exceed the physical tolerance of the production installations or the culture organisms. It is therefore important to measure a range of hydrographic variables, particularly during the planning or pre-licence phases. The most important information required is as follows:

current speed; current direction; neap and spring variations; current residuals; bathymetry; winds and wave action; temperature; salinity; water stratification;


Hydrographic conditions are seasonally variable, measurements should be carried out at certain time intervals, to take into account different sea temperatures and seasonal stratification/upwelling of bottom water masses.

In areas with significant tidal flows, current measurements should be made over a full tidal cycle, preferably at both spring and neap tides.

Peaks in production activities should also be taken into consideration.


Further, where possible, hydrographic measurements should be carried out at several sites within a given area to assess local variations in hydrography that could affect the aquaculture activities. For example, small variations in topographical features could cause local anomalies in current flow.

In addition, it is essential that accurate position fixing is used and that relocation of stations for time series analysis or for specific spatial monitoring, is considered.

Chemical analyses

Chemical analyses of bottom sediments around aquaculture sites quantify the levels of contaminants or the chemical properties.

These can be compared with natural conditions in the area as well as pre-defined levels of acceptability or consent.

Some measurements can be carried out in situ using probes for which the results are immediately available. These include the following variables, all of which give information on the sediment loading:

pH,

redox (Eh),

oxygen.

Chemical analyses

Laboratory analyses most often focus on the following:

Total organic carbon

organic content,

hydrogen sulphide,

sediment granulometry (indicative of organic deposition, bottom current speeds)

heavy metals.

In addition, specific pesticides, medicinal agents and antifoulants may be analysed according to individual requirements.


Changes in the organic loading of an area result in marked changes in the fauna present on the sea floor. The normal situation in undisturbed areas is a high species diversity with few dominant species and relatively few individuals representing each species. With organic loading of the sediment leads to a reduction in species diversity and an increase in abundance of opportunistic species. If the level of pollution becomes very severe, even opportunistic species will disappear, such that there are no macro-organisms present in extreme conditions.A white bacterial layer may form on the sediment surface. In this way, the changing status of macrofaunal communities is a very sensitive indicator of sedimentary conditions, allowing the detection of environmental impacts, where other methods might not record them.


Specific methodology concerning benthic faunal analysis would include

specification of sieve mesh size (e.g. in Northern latitude coastal areas, 1mm should be used, whereas in similar situations in the Mediterranean, 0.5mm should be used),

sample preservation

level of taxonomic identification e.g. Family level;

Rigorous analytical quality control procedures must be developed for all areas of practical work and implemented.

Survey timing

Pre licence or start up

During operation

Increase in production

Fallowing or close-down

Pre-licence or start-up

The main aims of a pre-licence environmental survey are summarised as follows:

To conduct baseline (or benchmark) study of natural conditions in the area. This allows comparison with future developments at the site;

To assess local variations in topography and hydrography;

To predict the likely impact of the proposed production project;

To provide information on management procedures.

During farm operation

The main aims of monitoring at operational farms are as follows:

To measure deviation from conditions at the time of the baseline/benchmark study;

To monitor the environment over time, to assess whether conditions are improving, staying the same or deteriorating as a result of the farm activities;

To assess the sustainability of the farm;

To provide the basis for recommending remedial action if required.

The frequency of this type of survey is defined by the regulators. Generally, annual monitoring of large farms is recommended, whereas smaller farms may be investigated less frequently or less intensively.

Increase in production

To review environmental status in relation to the organic loading during previous production;

To estimate whether an increase in production will cause environmental effects exceeding the safe carrying capacity of the receiving waters/ sediment;

To give guidelines on the permitted level of production increase;

To provide information towards the development of management procedures.

Close-down/fallowing

To measure recovery of a site previously used for production.

If a site is designated for re-use, the survey should predict when production can safely be renewed.

Survey types

Diver surveys

Sensory analysis

Photographic and video

SPI

ROV

Diving surveys (shallow-water)Method and equipment used

Qualified divers authorised to perform commercial surveys.Data provided

The data provided by diving surveys can be quantitative (where samples are taken for analyses), semi-quantitative or qualitative, e.g. in the form of a visual description.

EffectivenessThe main advantage of diver surveys is that the diver assesses a larger and better quality area than any of the remote methods and can discuss conditions with the producer directly upon completion of the survey. Diver-based visual assessment is very effective at a general level, but has a low sensitivity to mild impacts because these are not always apparent to the naked eye. A good impression of the conditions under fish farms is obtained, backed up by photographic documentation. An additional advantage is that the diver can swim directly under the cages and therefore assess the worst conditions (without the risk of cable entanglement. In addition, the samples obtained by diver are usually of good quality.However, the deeper a site is, the less time the diver is able to remain on the bottom. The maximum legal diving depth is 50m. In addition, the method is subjective and different divers may give differing assessments of the conditions, depending on competence and experience.

Data collected by diver surveys

Surveys carried out by diver offer a good overview of both the severity of the effects and the size of the impacted area.

The diver can swim under the cages to assess the most severely impacted areas, and can at the same time evaluate the condition of the moorings and nets at the farm.

This method is relatively flexible as the diver can take photographs as well as bringing for example core samples to the surface for visual inspection or chemical measurements.The results of such a diver survey are, therefore, easy to understand, and may be illustrated visually by the use of photography. The farmer is also given instant feedback on the conditions under the cages, allowing remedial action to be taken as soon as possible. However this method is limited to sites in relatively shallow areas and is therefore unsuitable for use where farms are located in deep water, as is the current trend. The method is also subjective such that error would be introduced by using different divers, thus reducing the validity of inter-site or inter‑year comparisons.

Semi-quantitative sensory assessment

Method and equipment usedSensory description of sediment collected by diver or remote sampling device (grab or corer).

Data providedThe data will give information on the general degree to which the sediment is affected, as for diver surveys. The main data provided are as follows: sediment colourvisible animal life; gas vesicles size and position in the sediment; sediment smell and texture; presence of bacterial layer (this may be washed away during ascent); outgassing.

EffectivenessSensory assessment is very effective for broad-scale assessments of general trends, but no quantitative information given. As with diver surveys, operator standardisation is essential to avoid discrepancies in interpretations. Samples can be photographed to give a permanent record.

Photography and video interpretation

Method and equipment usedWater proof cameras or video cameras used by a diver or remotely by sled or ROV.

Data providedAs for diver surveys, photographs and video recording can be used for semi-quantitative assessment of anaerobic conditions (bacterial layer), deposition of waste and some benthic fauna (presence of large animals and burrows/ tracks).

EffectivenessUnderwater photography is the only means of providing visual assessment at deep sites. As with diver methods, minor impacts may not be observed.

Data collected by sediment profile image

An analysis of the sediment profile is often considered essential in the monitoring of aquaculture sites.

This can be obtained by sediment profile image (SPI) photography. Using the diver operated SPC it is possible to obtain images from directly under the cages and the diver can also conduct a conventional diving survey at the same time. Where the site is beyond diving depth, a remote operated SPC can be used.The main results from a SPI survey are obtainable almost instantly, given access to photographic processing facilities, although the detailed interpretation and reporting may take somewhat longer. Thus, if conditions were critical, the farmer would receive instant warning.This method, while being relatively easy to operate in the field demands very specialised and expensive equipment.

Data collected by sediment profile image

An analysis of the sediment profile is often considered essential in the monitoring of aquaculture sites.

This can be obtained by means of core samples, or by sediment profile image (SPI) photography. The profile analysis should include visual observations as well as some basic chemical measurements.Using the diver operated SPC it is possible to obtain images from directly under the cages and the diver can also conduct a conventional diving survey at the same time. Where the site is beyond diving depth, a remote operated SPC can be used, but then the method relies on the point sampling principle which does not offer a full overview of the conditions, as well as being unable to access the areas under the cages.The main results from a SPI survey are obtainable almost instantly, given access to photographic processing facilities, although the detailed interpretation and reporting may take somewhat longer. Thus, if conditions were critical, the farmer would receive instant warning.This method, while being relatively easy to operate in the field demands very specialised and expensive equipment.

Sediment Profile Imagery - Norway

20 meters awayUnder Cages

Data collected by qualitative video transect surveys

This method of impact monitoring has been used extensively by regulatory authorities. The most commonly used method is to lay a marked transect rope on the seabed from 50m off the cages to the cage edge and use a diver to follow this rope and video the seabed along the route.This method allows the gross pollution indicated by bacterial mats and waste feed to be identified, but is somewhat subjective and cannot accurately determine effects on the benthic community or physico-chemical conditions, which allow comparison to sediment analysis taken by grab or corer. Video observations therefore cannot be to benthic infaunal standards.

Data collected by sled mounted video or photography

A video camera mounted on a sled, bulled by a suitable vessel can give a continuous visual image along relatively long transects of the area in question.

In this way it is possible to gain an impression of the variation and patchiness in bottom conditions.

The main drawback with this method in relation to aquaculture monitoring is the danger of entanglement with mooring cables around the cage group.

Remote operated vehicles (ROVs)

A video contained within a ROV is connected to the surface by means of an umbilical cable, containing power lines.

The machine is equipped with thrusters so that it can be steered by an operator at the surface and monitor connections allow instant viewing of the conditions.

In this way the machine can be steered under the cage group to record the worst case conditions as well as giving visual information from more peripheral locations.

Problems may however be encountered in areas with strong current conditions, where steering may become difficult.

Small, relatively lightweight ROVs have been used successfully in aquaculture monitoring in coastal areas and in deep or exposed waters, a larger and heavier ROV requiring winch deployment has been developed.

ROV data collection

Remote photography

Various types of remotely operated underwater photographic techniques are currently in use to monitor the sea floor, and include both still photography and video filming.

These allow visual and easily understood information to be obtained at depths where it is impractical or impossible to use a diver.

Still photography

A still camera mounted on a frame may be pulled behind a boat. The camera is triggered when the frame settles on the bottom. In this way a series of point photographs of the sediment surface may be obtained.

There is some danger that individual photographs may not be representative of the area in general, but since there are minimal processing costs, this uncertainty can be reduced by increasing the number of points sampled.

It is not possible to obtain images of the area directly under the cage group. In very fine flocculent sediment, it may be difficult to obtain images of an undisturbed sediment surface, or the framework may sink too deep into the soft sediment before the camera is triggered.

Analyses types

Analyses of sediment chemistry


Hydrography

Nutrients and plankton

Analyses of sediment chemistry

Method and equipment used

Samples are usually collected remotely by grab, corer or by diver in shallower waters.

Data provided

The data provided can easily be adjusted to individual requirements. In addition, specific contaminants or other chemical compounds can easily be added to the monitoring programme, depending on the discharges at the individual sites.

Effectiveness

Providing the analyses are carried out according to international laboratory standards, sediment chemistry analyses give informative, quantitative and inter-comparable assessment of both the actual contaminant loading and eventual changes. Interpretation requires personnel with experience in sediment chemistry.


Method and equipment usedUsually grab or core samplers are used. An area of the sea floor is sampled and the benthic fauna (invertebrate animals living on or in the sediment) are identified and counted. Statistical analyses of community composition are carried out. The data are interpreted using a knowledge of faunal responses to environmental disturbance (indicator species, dominant organisms, species diversity and known habitat tolerances of different animal groups).

Data providedThe data can be quantitative (all animals counted and identified in detail) or semi-quantitative (assessment of the general faunal structure and dominant organisms). The data obtained give a very accurate picture of the sedimentary conditions and the extent of organic loading. Comparing the data with previous surveys gives an accurate assessment of eventual recovery or deterioration in conditions.


Effectiveness

Benthic faunal analyses are highly accurate in assessing impacts, particularly when combined with chemical and physical analyses of the sediment. Faunal analyses often reveal changes in conditions below the detection threshold of chemical analyses, because the organisms are sensitive to low levels of impact. In general, faunal analyses are most effective in detecting organic impact.

Hydrography

Method and equipment usedVarious types of sensors are used, at chosen distances from the aquaculture farm and/or at different levels in the water column.

Data providedThe main parameters of interest are summarised below: current speeds; winds and wave action; oxygenation; temperature; salinity; eventual stratification (hydrographic profiles); and phytoplankton and primary production.It is important to measure at the critical periods of the year when biomass and feeding levels are at their highest. Changes as a result of differing tidal regimes should also be taken into account.

EffectivenessHydrographic measurements are effective for planning sites to assess their suitability for aquaculture, and also to analyse conditions during low water flow.

Nutrients and plankton

Method and equipment used

Bottled water samples taken at chosen distances from the aquaculture farm and/or at different levels in the water column. These can be sampled both by diver or by a remote controlled water sampler.

Data provided

The main parameters of interest are summarised below: nutrient levels, phytoplankton and primary production.

It is important to measure at the critical periods of the year when biomass and feeding levels are at their highest. Changes as a result of differing tidal regimes should also be taken into account.

Effectiveness

Quantification of primary production is an effective means of assessing the risk of eutrophication or hyper-nutrification.

Voluntary and enforced monitoring

Voluntary self-monitoring undertaken by the farm

Voluntary monitoring undertaken by independent specialists

Regulator enforced self-monitoring with spot checks (auditing)

Regulator enforced monitoring by independent specialists

Voluntary self-monitoring undertaken by the farm

Without regulator-imposed environmental monitoring schemes, some farms are prepare environmental policy statements and implementing voluntary environmental monitoring programmes.

It is recommended that the company initially establishes an environmental policy and then undertakes regular monitoring in such a way that good quality monitoring practice is implemented and reliable data obtained. The monitoring survey may take the form of diver inspections and/or a semi-quantitative sediment assessment (basic biological, physical and chemical conditions) depending on site location, scale of operation and site sensitivity.

Voluntary monitoring undertaken by independent specialists

At some farms voluntary self assessment is undertaken by independent specialists and follows procedures highlighted previously. The benefits to a company of high-quality voluntary monitoring include:

(i) a proactive measure for monitoring before enforced monitoring regulations are introduced;

(ii) early-warning of deteriorating conditions and professional advice on what remedial actions to take;

(iii) financial benefits as above (where applicable);

(iv) fostering a climate of co-operation between the licensee and Regulator;

(v) enhanced credibility with the local community and general environmental agencies.

Regulator enforced self-monitoring with spot checks (auditing) The regulator may enforce self-monitoring,

carried out by qualified personnel, with spot-checks, auditing or other means of quality control of the results. Quality assurance and analytical quality control practices need to be followed. In general, the results are sent to the regulator, for evaluation of the necessary remedial action, if appropriate. Audit programmes by regulators are essential and also require adequate resourcing. The intensity of monitoring required is adjusted to the actual environmental impact of the operations on the site and this encourages good practice.

Regulator enforced monitoring by independent specialists The regulator may enforce monitoring of

aquaculture farms, carried out by independent specialists. This may be done at pre-determined intervals (e.g. 1-3 years dependent on topology/ production), or if results of a smaller scale monitoring survey show unacceptable conditions (e.g. environmental impact exceeding the defined threshold of acceptable effects). An independent survey may also be enforced in cases where an aquaculture company fails to be proactive in undertaking regular monitoring surveys, or in case of any additional problems.

consultancy and research in aquaculture and the aquatic environment

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