ISO 16541:2015

INTERNATIONAL ISO
STANDARD 16541
First edition
2015-07-15
Methods for sea lice surveillance on
marine finfish farms
Méthodes de surveillance des poux de mer dans les exploitations de
pisciculture marine
Reference number
©
ISO 2015
© ISO 2015, Published in Switzerland
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ii © ISO 2015 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Sampling design . 3
4.1 Purpose, precision, and accuracy . 3
4.2 Specification of measure to be used (abundance, prevalence, and median intensity) . 3
4.2.1 General. 3
4.2.2 Abundance . . 3
4.2.3 Prevalence and median intensity . 4
4.2.4 Minimum requirements for on-farm monitoring of sea lice levels and
effect of treatment . 4
5 Information requirements for sampling events . 5
5.1 General . 5
5.2 Contextual elements at each sampling event . 5
5.3 Sea lice elements at each sampling event . 5
5.3.1 Sea lice dislodged during handling . 6
5.4 Structured format for reporting . 6
6 Monitoring programme elements . 7
6.1 General . 7
6.2 Selection of fish and handling . 7
6.3 Frequency for regular monitoring . 7
6.4 Frequency for assessment of treatment efficacy . 8
7 Training requirements . 8
Annex A (informative) Rationale for collecting site and cage-level data .10
Annex B (informative) Typical measures used to summarize sea lice data and their variability .11
Foreword
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iv © ISO 2015 – All rights reserved

Introduction
The term “sea lice” refers to several species of naturally occurring marine copepods that parasitize fish.
They attach themselves to the skin, fins, and gills of wild and farmed fish, and feed on host mucus and
skin. If an infestation is severe, it can negatively impact the health of affected fish.
The abundance of sea lice can be amplified on marine finfish farms and a concern is that farms can
then act as a reservoir, releasing lice back into the broader marine environment. Farms could thus
act as a source of infestation for wild fish, particularly salmonids. While it is possible to control lice
levels on farms through integrated pest management approaches and the use of therapeutants, the
same intervention cannot easily be applied to wild fish populations. For this reason, many jurisdictions
place requirements on farmed salmon producers to carefully monitor lice levels on farms and to take
appropriate actions to reduce on-farm lice populations where lice have been identified as a concern.
Where sea lice are identified as a concern to be managed, counts may be used in a number of ways.
Over the past decade, it has become increasingly common for regulators to establish upper limits to
abundance of lice on farms with the intent of minimizing potential impacts to wild fish populations.
Farming companies can also monitor lice abundance to maintain appropriate fish welfare conditions.
In addition, the development of reduced sensitivity to in-feed medication (following similar trends seen
for bath treatments in the 1990s), is a concern to both regulators and producers. Clear and standardized
sea lice counts are necessary for the early detection of any such trends. Both the aquaculture industry
and pharmaceutical suppliers of ecto-parasiticides would then be in a position to make better and
earlier determination of situations in which treatments were beginning to lose effectiveness, and thus,
to initiate appropriate mitigation strategies.
Over the past two decades, a range of counting methods have been developed across countries, and
sometimes within countries, such that it is often difficult to know how to interpret the sea lice levels
reported from farm sites. The goals of this International Standard are to ensure that the sea lice counts
carried out on marine finfish farms are accurate and fit for purpose and to establish a method for sea
lice on-farm surveillance that can be carried out in any farming area, affording accurate, consistent
estimates of lice. A standardized methodology will yield results that can better be compared across
jurisdictions and geographic regions, supporting the development and implementation of effective lice
management approaches and increasing public confidence that effective control measures are being
implemented.
This International Standard has been developed in consideration of the
— intended use of the results of sampling,
— practical and economic constraints of sampling,
— species of lice of concern in an area,
— cage and site configurations,
— seasonal or environmental conditions, and
— potential impacts on fish health and welfare.
INTERNATIONAL STANDARD ISO 16541:2015(E)
Methods for sea lice surveillance on marine finfish farms
1 Scope
This International Standard specifies both a method for sea lice counts on marine finfish farms and
a method for sea lice surveillance that can be carried out in any farming area to provide consistent
estimates of sea lice infestation.
It specifies the best practices associated with monitoring sea lice levels on marine finfish farms for
various purposes including the assessment of abundance, prevalence, and treatment efficacy. This will
include identifying minimum requirements for specific monitoring program elements (e.g. number of
fish and cages to be sampled, frequency of sampling, the level of detail recorded, etc.). The standard
will apply to all marine finfish farms which experience infestation with any of the range of “sea lice”
(copepodid) parasites.
2 Normative references
There are no normative references in this International Standard.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
sea lice
copepods of one of a number of lice species
Note 1 to entry: The most commonly occurring sea lice, depending on location, being the various salmon lice
Lepeophtheirus salmonis Krøyer, Caligus elongatus, Caligus clemensi, Caligus rogercresseyi, etc. and the cod louse
Caligus curtus.
3.2
sea lice stages
sea lice metamorphose to different life stages
Note 1 to entry: Sea lice stages includes the nauplii (free-swimming stage) through the copepodid stage (infectious
stage) to various stages of chalimus growth (attached stages) where they are attached to a single point on the fish
host. They then develop to pre-adult (for some lice species) and finally, adult stages, at which point they are able
to move around on the fish host (motile stages).
3.3
finfish
fish of the class Osteichthyes
3.4
facility
collective structures used for the purposes of finfish aquaculture; including the enclosures (net pens),
walkways, barges, floats plus associated lines and anchors
3.5
enclosures
containment structures, including net pens, cages, or similar structures used to contain finfish for the
purposes of aquaculture
3.6
treatment
measure applied to remove sea lice
EXAMPLE Treatment such as in-feed drug products, topical pesticides, or other methods that remove lice,
including mechanical removal.
3.7
abundance
mean number of lice across all of the fish that are examined at any particular sampling point
3.8
prevalence
proportion of fish on which at least one louse was observed from all of those examined during any
particular sampling event
3.9
intensity
mean number of lice across only those fish on which lice have been observed during the examination at
any particular sampling point
3.10
accuracy
quantitative measure of the degree of conformity with an accepted reference value
[SOURCE: ISO 6707-1:2004, definition 9.1.8]
3.11
precision
quantitative measure of the degree of agreement between individual measurements of the same
property
[SOURCE: ISO 6707-1:2004, definition 9.1.9]
3.12
sea lice count
event involving a number of fish from a range of cages on a marine finfish farm on a specific date which
enumerates the presence of different sea lice stages on these fish
3.13
sea lice surveillance
process by which sea lice levels are recorded and assessed over time; the protocol to organize and assess
a series of sea lice counts
3.14
clustering
degree to which parasites tend to aggregate within units (in this case cages)
Note 1 to entry: Can be formally measured by the intraclass correlation coefficient (ICC) which describes how
closely communities in the same unit tend to resemble each other.
2 © ISO 2015 – All rights reserved

4 Sampling design
4.1 Purpose, precision, and accuracy
The most important consideration in determining sampling design is the purpose for which the
monitoring is being carried out. The key issue in deciding on a sampling strategy is specifying the level
of precision or accuracy that is required as an outcome from the sampling process.
NOTE 1 The purpose of monitoring could be to fulfil regulatory requirements, in which case, it would be up to
the relevant authority to decide on the design details, or it could be to monitor the effectiveness of the treatments
for sea lice, in which case, the outcome could be of importance to both the authorities and producers of fish. The
design and frequencies of the monitoring will therefore vary.
NOTE 2 When reporting mean sea lice levels for comparison against treatment triggers, or simply to visualize
trends over time, it can be that ±20 % is adequate, while estimating efficacy of a treatment intervention can
require a more tightly defined precision.
There are also a number of biological factors that will affect the accuracy of estimates. In particular,
the level of clustering which exists in a given situation will impact on the importance of selecting a
representative number of cages from within a farm.
NOTE 3 Clustering refers to the relationship of within-cage to between-cage variation and is known to be
important in most ecological monitoring situations.
4.2 Specification of measure to be used (abundance, prevalence, and median intensity)
4.2.1 General
It is not only precision and accuracy that are associated with purpose; the actual metric that is used to
express the level of sea lice load on fish may change in differing contexts and under varying conditions
(see also Annex B). Abundance is the most commonly used metric when sampling sea lice. However,
when sea lice levels are very low, as is assumed to be the case when trigger levels of, for example, 0,1
adult females per fish are in place, it is unlikely that abundance will be the best metric.
NOTE 1 General advice from the quantitative parasitology literature is that prevalence and median intensity
may be better metrics to use than mean abundance in this circumstance.
NOTE 2 Regulatory thresholds are usually based on average sea lice figures, or in parasitological terminology,
“abundance”; while estimates of intensity and prevalence are typically only used in epidemiological studies.
4.2.2 Abundance
Having taken note of the considerations above, a relevant level of accuracy should be selected. The cells
contained in Table 1 indicate the estimated levels of accuracy that can be expected to be obtained under
different configurations of cage coverage and total number of fish in the sample. The accuracy increases
as the total number of fish sampled is increased (i.e. from left to right) and under normal conditions,
where clustering is present, the same is true as a larger proportion of the cages is included (i.e. moving
from top to bottom in the table). The diagonal lines in Table 1 indicate sampling strategies of equivalent
accuracy.
NOTE The actual slope of the diagonal lines in Table 1 is dependent on the degree of clustering present in a
given situation. The metric used to define this is the Intra-class Clustering Coefficient or ICC, which in the example
shown, based on empirical data, has been set to a value of 0,35. As the ICC approaches a value of zero, i.e. no
clustering, the lines of accuracy-equivalence would tend towards the vertical, indicating that accuracy is based
only on total number of fish included in the sample.
Table 1 — Impact of number of fish and % of cages sampled on precision estimation
4.2.3 Prevalence and median intensity
In situations of low abundance (e.g. less than 0,2 individuals per fish), an alternative metric should be used
to report sea lice infestation. This may be in addition to or in place of abundance. In such situations, the
prevalence will also be low, in the region of 10 % to 15 % of fish having parasites. Similar general issues
as those outlined in 4.1 will hold when determining accuracy. However, for prevalence, the maximum
level of resolution in any estimate will be limited to 1/N (where N is the number of fish per cage, or per
site, depending on the level at which prevalence is being estimated). Intensity measures consider only
fish which have sea lice present on them, and thus, in such situations, taken with prevalence, can provide
a more useful summary of infestation than abundance. In addition,
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