36
K.-H. Kock and 1. Everson
biggest species among Antarctic coastal fish are found in this family: D.
eleginoides which has a widespread distribution in subAntarctic waters
and its high-Antarctic congener D. mawsoni attain maximum sizes of
more than 200 cm (>100 kg) and 174 cm (ca. 70 kg) respectively. About
two thirds of the channichthyids which lack the respiratory pigment
hemoglobin grow larger than 45 cm [1].
The Onset of Sexual Maturity
Antarctic fish tend to spawn for the first time when between 55 and 80%
of their maximum length. There does not appear to be any difference
between notothenioids in the high-Antarctic region in comparison with
those of the lesser-Antarctic/subAntarctic waters [1]. A notable exception
is the mackerel icefish C. gunnari which, at South Georgia, spawns for the
first time when only about 40% of its maximum length. Close to
spawning, ovaries account for 20-30%(in some species up to 40%) of the
body weight [1].
Discussion
Comparatively small maximum sizes, high maximum ages and the
extreme thermal environment of Antarctic fish have led to the widespread
belief that notothenioids grow slowly. Although our analysis was impaired
by the paucity of validated age determinations, the growth performance
analysis provides sufficient evidence to suggest that growth performance
in a number of Antarctic nototheniids and channichthyids is by no means
low as suggested by the low values of K of the von Bertalanffy growth
formula, but is in many cases comparable to ecologically similar species
from boreal and temperate waters. Growth performance of nototheniids
and channichthyids exhibits the large variation one would expect from a
group of fish species which occupy a broader range of ecological niches.
The results which have been cited in the past as evidence for slow growth
fit within this range of values.
Three basic explanations had been offered in support of the hypothesis
that Antarctic fish grow slowly:
• A direct limitation by temperature;
• Adaptation to subzero temperatures necessitates an elevation of
metabolic rate with a concomitant reduction in the energy available
for growth; and
• Seasonality in food availability [6].
After an extensive discussion of the three possible explanations, Clarke
and North [6] concluded that the evidence from larval fish (and from
K.-H. Kock and 1. Everson
biggest species among Antarctic coastal fish are found in this family: D.
eleginoides which has a widespread distribution in subAntarctic waters
and its high-Antarctic congener D. mawsoni attain maximum sizes of
more than 200 cm (>100 kg) and 174 cm (ca. 70 kg) respectively. About
two thirds of the channichthyids which lack the respiratory pigment
hemoglobin grow larger than 45 cm [1].
The Onset of Sexual Maturity
Antarctic fish tend to spawn for the first time when between 55 and 80%
of their maximum length. There does not appear to be any difference
between notothenioids in the high-Antarctic region in comparison with
those of the lesser-Antarctic/subAntarctic waters [1]. A notable exception
is the mackerel icefish C. gunnari which, at South Georgia, spawns for the
first time when only about 40% of its maximum length. Close to
spawning, ovaries account for 20-30%(in some species up to 40%) of the
body weight [1].
Discussion
Comparatively small maximum sizes, high maximum ages and the
extreme thermal environment of Antarctic fish have led to the widespread
belief that notothenioids grow slowly. Although our analysis was impaired
by the paucity of validated age determinations, the growth performance
analysis provides sufficient evidence to suggest that growth performance
in a number of Antarctic nototheniids and channichthyids is by no means
low as suggested by the low values of K of the von Bertalanffy growth
formula, but is in many cases comparable to ecologically similar species
from boreal and temperate waters. Growth performance of nototheniids
and channichthyids exhibits the large variation one would expect from a
group of fish species which occupy a broader range of ecological niches.
The results which have been cited in the past as evidence for slow growth
fit within this range of values.
Three basic explanations had been offered in support of the hypothesis
that Antarctic fish grow slowly:
• A direct limitation by temperature;
• Adaptation to subzero temperatures necessitates an elevation of
metabolic rate with a concomitant reduction in the energy available
for growth; and
• Seasonality in food availability [6].
After an extensive discussion of the three possible explanations, Clarke
and North [6] concluded that the evidence from larval fish (and from