The Growth Of A Welsh Strain Of Arctic Charr

the growth of a welsh strain of arctic charr (salvelinus alpinus l.) and investigations into its aquaculture potential. i. k. berrill* † an

The growth of a Welsh strain of Arctic charr (Salvelinus alpinus L.)
and investigations into its aquaculture potential.
I. K. Berrill* † and I. D. McCarthy
School of Ocean Sciences, College of Natural Sciences, University of
Wales, Bangor,
Askew Street, Menai Bridge, Anglesey, LL59 5AB, U.K.
* Author to whom correspondence should be addressed. Tel.: +44 (0)
1786 467874;
fax: +44 (0) 1786 472133; e-mail: [email protected]
† Present address: Institute of Aquaculture, University of Stirling,
Stirling, FK9 4LA, U.K.
Abstract
The growth in captivity of a wild Welsh strain (Llyn Cowlyd) of Arctic
charr (Salvelinus alpinus) was compared to that of a commercial
Scottish strain over the course of a 12 month experiment. At the
conclusion of the study, the Welsh strain had a lower mass and
condition factor than the commercial fish, but a similar length.
Aspects of the growth and population structure of the Welsh strain
imply that it could be a subject for aquaculture development, but such
practises will be dependant on further work on selection and
broodstock development.
Keywords: Arctic charr, growth, development, aquaculture.
Arctic charr (Salvelinus alpinus L.) is a holarctic species
representing the most northerly of all freshwater and anadromous fish
(Klemetsen, 2003). Consequently the species is adapted to cold water
temperatures and shows good growth, development and survival rates in
low temperature ranges (Wallace & Aasjord, 1984a; Jensen et al., 1989;
Jobling et al., 1992; Jobling et al., 1998), being the salmonid able
to survive the lowest water temperatures (Baroudy & Elliott, 1994).
They have also been shown to grow and survive well when reared at
densities higher than those favoured by other commercially-reared
salmonids (Jobling et al., 1992; Siikavuopio & Jobling, 1995; Jobling
et al., 1998; Brännäs & Linnér, 2000). Additionally, Arctic charr have
long been prized for their taste and this, as well as currently
limited levels of production [e.g. 3.5 tonnes of Arctic charr were
reared in Scotland in 2006 (Anon., 2006)], has led to market prices
significantly higher than, for example, Atlantic salmon, Salmo salar
(L.), or rainbow trout, Oncorhynchus mykiss (Walbaum), (FAO
statistics, http://www.fao.org). These characteristics all indicate
that Arctic charr represent a species with potential for aquaculture,
in particular in climates and conditions where the culture of other
salmonids may not prove profitable.
There has been increasing interest surrounding the ecology and
aquaculture potential of U.K. populations of Arctic charr in recent
times (Heasman & Black, 1998; Maitland et al., 2007). However, in
North Wales, where three native and four translocated resident
populations exist (McCarthy, 2007) detailed information on the biology
of charr populations, necessary for aquaculture development, is not
available. Importantly, the threat that commercial Arctic charr
farming practises present to the genetic integrity of native U.K.
stocks has been highlighted (Heasman & Black, 1998; Maitland et al.,
2007). Consequently, decisions regarding the commercial culture of
Arctic charr and the development of breeding programmes will be
enhanced by the use of regional stocks, which reduce the chances of
genetic contamination, as well as a detailed knowledge of the culture
potential of native charr within localised regions. Consequently, the
current study aimed to investigate the aquaculture potential of a
Welsh strain of Arctic charr by comparing its growth with a commercial
strain from Scotland.
Spawning adult Arctic charr were collected from Llyn Cowlyd, North
Wales (53o08’ N; 3o54’ W) using multipanel benthic gill nets
(Lundgrens Fiskredskap; Sweden) on 8 December 2004. Eggs were hand
stripped from females [mass (M) = 64.5 ± 8.0g, fork length (LF) =
196.0 ± 8.4mm, (mean ± s.d., n=5)] and each batch fertilised using
milt hand stripped from a single male [M = 69.7 ± 10.2g, LF = 190.8 ±
5.1mm, (mean ± s.d., n=5)]. The eggs (approx. n=500) were water
hardened and transferred to aquarium facilities at the University of
Wales, Bangor. On 11 February 2005, 1000 eyed eggs of a commercial
Scottish strain of Arctic charr were obtained from John Eccles
Hatcheries, Orkney. A sub-sample of eggs (n=20) from each strain were
weighed and measured, with those of the Llyn Cowlyd fish [M = 61.4 ±
5.5mg, 5.11 ± 0.25mm diameter, (mean ± s.d.)] found to be larger than
those from the commercial strain [M = 50.3 ± 5.7mg, 4.59 ± 0.19mm
diameter, (mean ± s.d.)] (P<0.05, students t-test).
Eggs were incubated under darkness in gently aerated static water
baths (10 l.) held at 4.0 ± 1.5oC, with 75% of the water changed with
fresh, aerated lake water at 7d intervals. The eggs were incubated in
one 10 l. water bath for each strain (Llyn Cowlyd and the commercial
strain). Whilst this did not allow replication at the incubation
stage, the rearing conditions accurately matched those commonly used
in commercial production. The experiment focused primarily on juvenile
growth in the first year of development and the egg rearing conditions
were not considered detrimental to the overall aims of the study. 50%
hatching occurred on 14 February and 16 March for the commercial and
Llyn Cowlyd fish respectively and at hatch the water temperature was
gradually increased and maintained at 7.4 ± 0.4oC until first feeding
on 4 April (340 degree days post hatch) and 23 April 2005 (270 degree
days post hatch) for the commercial and Llyn Cowlyd fish respectively.
At first feeding, the water temperature was further increased to 10oC
and three groups of fish from each strain (n=100 per group and n=75
per group for the commercial and Llyn Cowlyd fish respectively) were
transferred to each of six 1m x 1m x 0.75m fibreglass rearing tanks,
which were part of a recirculation system where water was filtered and
re-used, with approximately 10% of the recirculated water replaced per
day. The fish from each strain were reared for 12 months from their
respective date of first feeding. Water temperature was 12.6 ± 5.0oC
over the course of the experiment and water flow rates were initially
0.1 l.s-1 but were increased to 0.25 l.s-1 as the fish became larger.
Fish were exposed to a natural photoperiod regime and fed commercial
salmon feed (EWOS Micro; EWOS Ltd., U.K.) throughout the light phase
of the photoperiod, according to feed rates described by Johnston
(2002). At monthly intervals from first feeding all fish were weighed
(M, ±0.1g) with fork length (LF, ±1mm) recorded from three months
after first feeding.
Condition factor (K) was calculated as: 100MLF-3. Data were analysed
using Minitab v14. Changes in M, LF and K between strains were
compared using a General Linear Model, with natural log
transformations used to improve the normality and homogeneity of
variance of the M and LF data. A significance level of 5% was applied
to the statistical tests (Zar, 1999).
The M of both strains of fish increased throughout the experiment
(P<0.001) (Fig. 1a). The average M of the Llyn Cowlyd fish was greater
than the commercial strain charr for the first three months post first
feeding (P<0.001) and then from month seven onwards the commercial
strain fish were significantly heavier than the Llyn Cowlyd fish
(P<0.01). The LF of both strains increased over the course of the
experiment (P<0.001) (Fig. 1b). In month three, the Llyn Cowlyd fish
were significantly longer than the commercial fish (P<0.05), but from
month four onwards the average lengths of the two strains were
similar. The K of both strains increased over the experimental period
(P<0.001) (Fig. 1c) and from month five onwards, the K of the
commercial strain fish was significantly higher than that of the Llyn
Cowlyd fish (P<0.01).
At the conclusion of the experiment there were differences in the
coefficient of variation in M, LF and K between the two strains of
fish (Table I). The commercial fish were significantly heavier with a
higher K than the Llyn Cowlyd fish (both P<0.05) but the coefficient
of variation in the M and K of the Llyn Cowlyd fish was larger (by an
order of magnitude) than that of the commercial fish. The LF of the
commercial and Llyn Cowlyd fish were similar at the conclusion of the
experiment, and although the coefficient of variation in LF of the
Llyn Cowlyd fish was larger than for the commercial fish, the
difference in variation was not of a similar magnitude to that
recorded for M and K.
The current study has been the first to examine the growth of a Welsh
strain of Arctic charr in captivity and compare it to a commercial
strain. After 12 months, the Welsh charr had a lower M and K than the
commercial fish. Previous studies have shown differences in
performance between wild and commercial strains of Arctic charr (Ringø
et al., 1988) as well as other salmonids (Fleming & Einum, 1997;
Handeland et al., 2003) with these results likely to be due to the
selection for rapid growth in commercial strains (Handeland et al.,
2003; Brännäs et al., 2005). Conversely though, Brännäs et al. (2005)
found no difference between the growth of fourth generation selected
charr and their wild strain of origin. However, in their study culture
conditions were adapted to promote dominance hierarchies, with the
result that fish having undergone selection for fast growth had
reduced subordinate behaviour, leading to less size variation, and
indeed a similar mechanism may have been influential in the size
differences recorded in the current experiment. Importantly, although
there was a difference in M between the strains in the current
experiment, the Llyn Cowlyd fish achieved a M of approximately 75% of
the commercial strain. A 10% per generation increase in growth rate
has been reported for Arctic charr in a captive rearing programme in
Sweden (Brännäs et al., 2005) and it may be that continued breeding of
the Llyn Cowlyd strain could rapidly improve its performance.
Furthermore, the Llyn Cowlyd fish maintained a similar LF to the
commercial fish and grew much larger than their wild parents. Although
differences between the nutritional content of the commercial diets
and those gained in the wild would have been a major factor in the
size differential between the reared Llyn Cowlyd fish and their wild
parents, it seems that the Llyn Cowlyd fish can perform well on
commercial diets when reared in captivity. Consequently, it seems
sensible to suggest that with continued research there may be scope
for developing commercial Welsh charr lineages.
The two strains of charr exhibited different patterns of growth during
the experiment. Initially the Welsh fish had a greater M and LF than
the commercially farmed strain. A positive correlation between egg
size and hatch size is well documented in salmonids (Wallace &
Aasjord; 1984b; Springate & Bromage, 1985) and the larger eggs clearly
resulted in the Welsh fish being larger during the early stages of the
experiment. However, this size differential only persisted until month
three, indicating that the early growth of the commercial strain was
greater than that of the Welsh fish. This also indicates that large
size at hatch or first feeding does not necessarily equate to a growth
advantage in later life (Fowler, 1972; Thorpe et al., 1984). In the
current study, the commercial strain became heavier than the Llyn
Cowlyd fish seven months after first feeding, with the differential in
M increasing to the conclusion of the experiment. This indicates that
the growth in M of the commercial fish was not only higher during
early development but may have persisted in being higher throughout
the experiment. Both strains maintained a similar LF and because the
differences in M and LF were not coupled, the commercial fish had a
higher K than the Llyn Cowlyd fish. The reasons for this differential
in M and LF between the strains are not clear, but it may be that M
and/or K have been traits preferentially selected for over LF in the
commercial strain.
Interestingly, the Welsh strain exhibited more variation in M, LF and
K at the conclusion of the experiment, with this variation more
prominent in the M and K data. Previously, Brännäs et al. (2005) found
similar differences in weight variation between wild and captive
strains of Arctic charr and ascribed this difference to the selection
for fast growth favouring selection against subordinates, which then
resulted in a decrease in individual differences in growth. In the
current study social status was not determined but it is likely that
similar differences in population social structure between the two
strains caused the notable differences in size variation.
In summary, the current study has identified differences between the
development of a Welsh strain of Arctic charr and a commercial U.K.
stock, although this is to be expected when comparing the first
generation of a wild strain with a commercial strain (Handeland et al.,
2003). The results of this study show that there is potential for the
development of Welsh Arctic charr strains for aquaculture.
This research was financed with the support of the European Union ERDF
- Interreg IIIB "Atlantic Area" (project 091).
References
Anon. (2006). Scottish fish farms: Annual production survey. Fisheries
Research Services. Aberdeen, UK. 36pp.
Baroudy, E. & Elliott, J. M. (1994). The critical thermal limits for
juvenile Arctic charr Salvelinus alpinus. Journal of Fish Biology 45,
1041-1053. doi:10.1111/j.1095-8649.1994.tb01071.x
Brännäs, E. & Linnér, J. (2000). Growth effects in Arctic charr reared
in cold water: Feed frequency, access to bottom feeding and stocking
density. Aquaculture International 8, 381-389.
Brännäs, E., Chaix, T., Nilsson, J. & Eriksson, L-O. (2005). Has a
4-generation selection programme affected the social behaviour and
growth pattern of Arctic charr (Salvelinus alpinus)? Applied Animal
Behaviour Science 94, 165-178.
Fleming, I. A. & Einum, S. (1997). Experimental tests of genetic
divergence of farmed from wild Atlantic salmon due to domestication.
ICES Journal of Marine Science 54, 1051-1063.
Fowler, L. G. (1972). Growth and mortality of fingerling chinook
salmon as affected by egg size. Progressive Fish-Culturist 34, 66-69.
Handeland, S. O., Porter, M., Björnsson, B. Th. & Stefansson, S. O.
(2003). Osmoregulation and growth in a wild and a selected strain of
Atlantic salmon smolts on two photoperiod regimes. Aquaculture 222,
29-43.
Heasman, M. S. & Black, K. D. (1998). The potential of Arctic charr,
Salvelinus alpinus (L.), for mariculture. Aquaculture Research 29,
67-76. doi:10.1046/j.1365-2109.1998.00929.x
Jensen, A. J., Johnsen, B. O. & Saksgård, L. (1989). Temperature
requirements in Atlantic salmon (Salmo salar), brown trout (Salmo
trutta), and Arctic char (Salvelinus alpinus) from hatching to initial
feeding compared with geographic distribution. Canadian Journal of
Fisheries and Aquatic Sciences 46, 786-789.
Jobling, M., Jørgensen, E. H., Christiansen, J. S., Arnesen, A. M. &
Palsson, J. Ø. (1992). Investigation of growth requirements and
aquaculture potential of Arctic charr (Salvelinus alpinus). Icelandic
Agricultural Science 6, 47-62.
Jobling, M., Tveiten, H. & Hatlen, B. (1998). Cultivation of Arctic
charr: an update. Aquaculture International 6, 181-196.
Johnston, G. (2002). Arctic charr aquaculture 1st Ed., Blackwell
Publishing: Oxford, UK. 272pp.
Klemetsen, A., Amundsen, P.-A., Dempson, J. B., Jonsson, B., Jonsson,
N., O’Connell, M. F. & Mortensen, E. (2003). Atlantic salmon Salmo
salar L., brown trout Salmo trutta L. and Arctic charr Salvelinus
alpinus (L.): a review of aspects of their life histories. Ecology of
Freshwater Fish 12, 1-59. doi:10.1034/j.1600-0633.2003.00010.x
Maitland, P. S., Winfield, I. J., McCarthy, I. D. & Igoe, F. (2007).
The status of Arctic charr Salvelinus alpinus in Britain and Ireland.
Ecology of Freshwater Fish 16, 6-19.
doi:10.1111/j.1600-0633.2006.00167.x
McCarthy, I. D. (2007). The Welsh Torgoch (Salvelinus alpinus): a
short review of its distribution and ecology. Ecology of Freshwater
Fish 16, 34-40. doi:10.1111/j.1600-0633.2006.00166.x
Ringø, E., Kristoffersen, R. & Nilsen, B. (1988). Wild and
hatchery-reared landlocked Arctic charr, Salvelinus alpinus (L.), from
Lake Takvatn, reared in fresh and sea water. Content of free amino
acids and ninhydrin-positive substances. Aquaculture 74, 359-367.
Siikavuopio, S. I. & Jobling, M. (1995). The effect of stocking
density on survival and growth of wild-caught Arctic char. Nordic
Journal of Freshwater Research 71, 419-423.
Springate, J. R. C. & Bromage, N. R. (1985). Effects of egg size on
early growth and survival in rainbow trout (Salmo gairdneri
Richardson). Aquaculture 47, 163-172.
Thorpe, J. E., Miles, M. S. & Keay, D. S. (1984). Developmental rate,
fecundity and egg size in Atlantic salmon, Salmo salar L. Aquaculture
43, 289-305.
Wallace, J. C. & Aasjord, D. (1984a). The initial feeding of Arctic
charr (Salvelinus alpinus) alevins at different temperatures and under
different feeding regimes. Aquaculture 38, 19-33.
Wallace, J. C. & Aasjord, D. (1984b). An investigation of the
consequences of egg size for the culture of Arctic charr, Salvelinus
alpinus (L.). Journal of Fish Biology 24, 427-435.
doi:10.1111/j.1095-8649.1984.tb04813.x
Zar, J.H. (1999). Biostatistical analysis. 4th Ed., Prentice Hall:
Upper Saddle River, New Jersey. 662pp.
Table I.
The mean and coefficient of variation (CV) in mass (M), fork length (LF)
and condition factor (K) (n=3) of a commercially reared and Welsh
strain of Arctic charr at the conclusion of a 12 month growth
experiment. * denotes a statistical difference (P<0.05) between the
mean values of the two strains.

Fig. 1 Changes in mass (M) (a), fork length (LF) (b) and condition
factor (K) (c) (mean ± s.e.m., n=3) of two strains of Arctic charr; a
commercially reared Scottish strain ( ) and those reared from
eggs collected from spawning adults caught in Llyn Cowlyd, North Wales
( ), following a 12 month growth experiment starting from first
feeding. Significant differences are indicated by asterisks (P<0.05)
with the numbers (1) and (2) indicating a larger mean value for the
commercial or Llyn Cowlyd strain respectively.
Fig. 1

15