Respiration and Activity of Arctic and Antarctic Fish: A Multivariate Analysis
Results and Discussion
Activity and Respiration
167
Twenty respiration experiments, lasting for a total of 2300 h (up to 380 h
per experiment) were used for the factor analysis (Table 1); 1500 h of
video recordings were evaluated and more than 82 000 movements
detected.
Differences between active and sluggish representatives were clearly
visible, especially in the movement rate. While the most active cryopelagic
individual (Boreogadus) showed a mean movement rate of up to 600 per
hour (max.: 2000 moves), the most sluggish specimen (a Pogonophryne)
did not move more than 2.7 times an hour (max.: 360). The quotient (ratio)
of max. and mean movement rate is high for sluggish species compared to
active ones (Table 1 b). The most sluggish Antarctic animals exhibited
periods of up to 22 h without any significant movement (Pogonophryne
sp.). Mean intervals between moves were 22 min for this species. The
most torpid Arctic specimen investigated was a Myoxocephalus scorpius
with maximum inactivity intervals of 1.1 h and mean periods of inactivity
of3.5 min.
The calculated individual SOC ranged from 8.0 (± 0.04) mg 02 h-I kg
WM (wet mass) -I for an Antarctic Pogonophryne sp. to 68 (± 2) mg 02 h- I
kg WM-I for a large and very active Arctic Myoxocephalus scorpius. The
individual variability was generally high. Routine oxygen consumption
(including phases with spontaneous activity) was up to 6 times and
respiration during phases with maximum spontaneous activity up to 8
times higher than the calculated SOC.
Factor Analysis
The first three factors separated by factor analysis had Eigen values of
3.31, 1.96 and 1.54. They explained almost three-quartes of the total
variance among the original variables. The communalities for the 9
variables analyzed ranged between 71% and 91%, which means that all
variables were well explained by the extracted factors.
The factor loadings of the 9 variables are visualized by the orientation
and length of vectors, which are projected in the planes between factor 1
and 2 as well as factor 1 and 3 (Fig. 2).
The first factor explains almost 35% of the variance in the standardized
variable values. It is related mainly to the mean movement rate and the
standard oxygen consumption rate of the investigated fishes. The second
factor represents temperature-related variables and is responsible for
almost 22% of the variation. The scope for activity has the strongest
relation to the third factor, which still has a variance share of about 17%.
Results and Discussion
Activity and Respiration
167
Twenty respiration experiments, lasting for a total of 2300 h (up to 380 h
per experiment) were used for the factor analysis (Table 1); 1500 h of
video recordings were evaluated and more than 82 000 movements
detected.
Differences between active and sluggish representatives were clearly
visible, especially in the movement rate. While the most active cryopelagic
individual (Boreogadus) showed a mean movement rate of up to 600 per
hour (max.: 2000 moves), the most sluggish specimen (a Pogonophryne)
did not move more than 2.7 times an hour (max.: 360). The quotient (ratio)
of max. and mean movement rate is high for sluggish species compared to
active ones (Table 1 b). The most sluggish Antarctic animals exhibited
periods of up to 22 h without any significant movement (Pogonophryne
sp.). Mean intervals between moves were 22 min for this species. The
most torpid Arctic specimen investigated was a Myoxocephalus scorpius
with maximum inactivity intervals of 1.1 h and mean periods of inactivity
of3.5 min.
The calculated individual SOC ranged from 8.0 (± 0.04) mg 02 h-I kg
WM (wet mass) -I for an Antarctic Pogonophryne sp. to 68 (± 2) mg 02 h- I
kg WM-I for a large and very active Arctic Myoxocephalus scorpius. The
individual variability was generally high. Routine oxygen consumption
(including phases with spontaneous activity) was up to 6 times and
respiration during phases with maximum spontaneous activity up to 8
times higher than the calculated SOC.
Factor Analysis
The first three factors separated by factor analysis had Eigen values of
3.31, 1.96 and 1.54. They explained almost three-quartes of the total
variance among the original variables. The communalities for the 9
variables analyzed ranged between 71% and 91%, which means that all
variables were well explained by the extracted factors.
The factor loadings of the 9 variables are visualized by the orientation
and length of vectors, which are projected in the planes between factor 1
and 2 as well as factor 1 and 3 (Fig. 2).
The first factor explains almost 35% of the variance in the standardized
variable values. It is related mainly to the mean movement rate and the
standard oxygen consumption rate of the investigated fishes. The second
factor represents temperature-related variables and is responsible for
almost 22% of the variation. The scope for activity has the strongest
relation to the third factor, which still has a variance share of about 17%.