Fiskevelferdsmessig vurdering av produksjon av 0-års smolt

4 Summary
In the following summary some major risk factors affecting animal welfare will be
briefly discussed. The discussion will be focused on, firstly, the possible effects on
the ability of the fish to adapt to its environment and, secondly, whether the factor in
question is a general risk factor in smolt production or whether it affects one or the
other group, 0+ or 1+ smolts to a greater extent.
When exposed to substantial deviation from near optimal environmental conditions
and/or in its physiology/anatomy the fish reacts with a stress response. The extent of
the stress response in each case will, thus, not be discussed in any detail as this may
vary with the degree and duration of the deviation.
As there is some debate on the degree of pain reception (nociception) and pain
perception in fish there will be no attempt to quantify the possible effect of each risk
factor in terms of pain.
The most important factors effecting smolts, disregarding the production method, can
be divided into 3 main groups:
− Physiological aspects, smoltification, deform
− Fish health
− Environmental
aspects
Smoltification
The smoltification is important if the smolt is to manage the transfer to seawater and
the challenges in terms of maintaining homeostasis. Incomplete smoltification
represents a gradient of welfare aspects based on the degree of smoltification. Those
can vary from moderate and brief symptoms such as loss of appetite and problems
in
maintaining homeostasis to acute symptoms resulting in outbreak of diseases and, in
its extreme, result in increased mortality. There are no indications on incomplete
smoltification representing a bigger problem in the production of 0+ smolts that 1+
smolts. Data from the r-Max database maintained by Skretting indicate somewhat
greater mortality immediately after transfer for 1+ smolts that for 0+ smolts. These
observations supports scientific work concluding that given the right production
strategy, 0+ smolts will adapt to seawater condition in the same way as 1+ smolts.
As smoltification is the most critical factor in successful transfer one should, at all
times, use the best available methods to assess the degree of smoltification prior to
transfer to sea.
It is assumed that deformities reduce the ability to cope with the cage environment to
a varying degree. All deformities will, to some degree, influence on the possibilities
the inflicted fish has to master some parts of it environment. Lack of data makes
comparison difficult but field data indicates somewhat higher prevalence in 0+. In
order to reduce the danger of deformities follow the advise in existing literature on
environment factors such as gasses in water, temperature and time for vaccination.
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