34
K-H. Kock and I. Everson
The growth perfonnance of a number of high-Antarctic nototheniids lies
outside the range commonly occupied by marine and brackish-water fish
(Fig. 1). This is due to their simultaneously low values estimated for K,
Loo and Woo, except in T newnesi (point 17), a high-Antarctic species
investigated in the Antarctic Peninsula region for which a relatively high
value of K has been described. However, as mentioned above, growth
parameters of high-Antarctic species with very few exceptions have been
derived from unvalidated age estimates and could be subject to revisions
during forthcoming validation studies [1].
Comparing Antarctic species with ecologically similar fish species from
temperate and boreal waters, we note that the growth perfonnance of the
Dissostichus species is comparable to that of North Sea cod (Gadus
morhua) (point 32C) and little tuna (Euthynnus alletteratus) (point 43);
that of N rossii compares to Atlantic cod from West Greenland (point
32B) and saithe (Pollachius virens) (point 40) in the North Sea. Growth
perfonnance of other larger nototheniids and channichthyids in lesserAntarctic/subAntarctic waters is similar to common North Sea species,
such as the ballan wrasse (Labrus bergylta) (point 46) or mackerel
(Scomber scombrus) (point 35). Growth perfonnance in small-sized
nototheniids both in lesser-Antarctic/subAntarctic waters and in the
vicinity of the Antarctic continent compares well with that of the sea
scorpion (Taurulus bubalis) (point 37) in the Baltic Sea, of Cottus kessleri
(point 38) in Lake Baikal, and the dragonet (Callionymus lyra) (point 34)
in the North Sea.
Feeding Regime
Few studies have followed feeding activity and diet composition year
round. Available infonnation indicates a change in food composition of
some species in winter ([1] for review). These shifts in prey composition
are likely to reflect changes in the availability of prey organisms.
Studies on energy requirements suggested that the daily food demands
of N rossii and G. gibberifrons in the vicinity of South Georgia were
reduced by a factor 2-3 in winter compared with the summer [30,31]. The
condition factor in juvenile N rossii around South Georgia exhibited a
strong seasonal signal usually being lowest in winter [32]. However, the
level of lipid in juvenile P. antarcticum in the Weddell Sea was similar in
winter and summer [33]. Similarly, the evidence for a reduction in feeding
intensity during winter is not unequivocal: a reduction in feeding intensity
in winter was observed in some nototheniids [13,34]. It has also been
induced in captive H. antarcticus [35]. However, observations in other
nototheniids provided no evidence for a decline in feeding intensity during
K-H. Kock and I. Everson
The growth perfonnance of a number of high-Antarctic nototheniids lies
outside the range commonly occupied by marine and brackish-water fish
(Fig. 1). This is due to their simultaneously low values estimated for K,
Loo and Woo, except in T newnesi (point 17), a high-Antarctic species
investigated in the Antarctic Peninsula region for which a relatively high
value of K has been described. However, as mentioned above, growth
parameters of high-Antarctic species with very few exceptions have been
derived from unvalidated age estimates and could be subject to revisions
during forthcoming validation studies [1].
Comparing Antarctic species with ecologically similar fish species from
temperate and boreal waters, we note that the growth perfonnance of the
Dissostichus species is comparable to that of North Sea cod (Gadus
morhua) (point 32C) and little tuna (Euthynnus alletteratus) (point 43);
that of N rossii compares to Atlantic cod from West Greenland (point
32B) and saithe (Pollachius virens) (point 40) in the North Sea. Growth
perfonnance of other larger nototheniids and channichthyids in lesserAntarctic/subAntarctic waters is similar to common North Sea species,
such as the ballan wrasse (Labrus bergylta) (point 46) or mackerel
(Scomber scombrus) (point 35). Growth perfonnance in small-sized
nototheniids both in lesser-Antarctic/subAntarctic waters and in the
vicinity of the Antarctic continent compares well with that of the sea
scorpion (Taurulus bubalis) (point 37) in the Baltic Sea, of Cottus kessleri
(point 38) in Lake Baikal, and the dragonet (Callionymus lyra) (point 34)
in the North Sea.
Feeding Regime
Few studies have followed feeding activity and diet composition year
round. Available infonnation indicates a change in food composition of
some species in winter ([1] for review). These shifts in prey composition
are likely to reflect changes in the availability of prey organisms.
Studies on energy requirements suggested that the daily food demands
of N rossii and G. gibberifrons in the vicinity of South Georgia were
reduced by a factor 2-3 in winter compared with the summer [30,31]. The
condition factor in juvenile N rossii around South Georgia exhibited a
strong seasonal signal usually being lowest in winter [32]. However, the
level of lipid in juvenile P. antarcticum in the Weddell Sea was similar in
winter and summer [33]. Similarly, the evidence for a reduction in feeding
intensity during winter is not unequivocal: a reduction in feeding intensity
in winter was observed in some nototheniids [13,34]. It has also been
induced in captive H. antarcticus [35]. However, observations in other
nototheniids provided no evidence for a decline in feeding intensity during