New England Aquarium: Supporting Environmentally Responsible Seafood Choices - SEAFOOD Ecolabelling: Principles and Practice - page 331

A second organisational philosophy of the ADRT is the concept that a best 'B'
ranking (see Figure 16.3) is often synonymous with an ideal operating condition,
or no impact. In a real world scenario, such a practice may be nearly impossible
to attain. However, this strict definition of 'best' remains as one of the ranking
options in the ADRT in order to serve as a reminder of the performance level and
management practices towards which the industry should strive.
In the practical application of the ADRT, the first DP, output controls and effluent
(Figure 16.3), considers ecosystem impacts located immediately surrounding the
farm. While national, local and corporate rules and regulations controlling site
choices are central to determining overall farm impact (Levings et al. 1995), they
are not evaluated within the ADRT because this programme assesses performance-
based standards, and not policies or regulations. A farm's impacts on the benthic
habitat below net pens are impacts that the farm can take immediate action to
decrease by reducing wastes (Holmer et al . 2005). Within DP1, benthic parameters,
such as redox potential and sulphides, are assessed first because of the shorter
time scale over which those impacts can occur (Hargrave et al. 1995). Longer-
term impacts would include changes to the diversity of benthic infauna beneath the
cages (Holmer et al . 2005). Excessive benthic impacts would indicate an improperly
sited or mismanaged farm and a situation that would quickly translate into other
ecosystem, fish health and overall corporate performance impacts (Lumb 1989).
As an example, the B, S and M ranking are as follows:
B: sulphide concentrations would always be equivalent to that of a reference
station (with the reference station matched for sediment physiochemical
properties);
S: would have an impact from slightly increased sulphide concentrations; and
M: would have greatly increased sulphide concentrations.
DP2 considers farm inputs - additions to the production system such as feed util-
isation and sources, therapeutant usage and strategies including treating external
parasites such as sea lice, and chemical treatments associated with net and cage
cleaning and maintenance. Within the spirit of the hierarchical assessment, the fish
oil and fishmeal (feed) usage is assessed at several levels. The use of fish oil is as-
sessed prior to fishmeal because of the lower conversion rate from fish products, and
oil is a more dominant limiting factor than meal (Tacon et al . 2006). For both these
factors, the minimisation of 'wild fish use' (fish oil and meal from wild-capture
fisheries) is taken into account, and when combined with a feed conversion ratio,
this determines the outcome for use of fish oil or fishmeal in the diet.
DP2 also considers the amount of therapeutants used in treating internal diseases
as well as the treatment strategy (e.g. cage management schemes) and external
parasite treatments and strategies. An MAS is determined for each point based on
the treatment rates and the therapeutants and chemicals used. A DNB condition
outcome from DP2 would include sourcing fish oil and fishmeal from overfished
wild populations or where overfishing is occurring.