John F. Steffensen

Some errors in respirometry of aquatic breathers: How to avoid and correct for them.

Respirometry in closed and flow-through systems is described with the objective of pointing out problems and sources of errors involved and how to correct for them.Both closed respirometry applied to resting and active animals and intermillent-flow respirometry is described. In addition, flow-through or open respirometry is discussed, in particular when the system is in non-steady state.Simulations are used to show how improper analysis can lead to improper conclusions.

An automated swimming respirometer

Abstract An automated respirometer is described that can be used for computerized respirometry of trout and sharks.

Oxygen consumption in four species of teleosts from Greenland: no evidence of metabolic cold adaptation

Standard metabolic rate of Greenland cod or uvak, Gadus ogac, polar cod, Boreogadus saida, Atlantic cod, Gadus morhua, and sculpin, Myxocephalus scorpius, caught in the same geographical area on the west coast of Greenland was measured at 4.5°C, the temperature at which the fish were caught. The present data does not support the Metabolic Cold Adaptation theory in the traditional sense of the standard metabolic rate being 2–4 times higher for Arctic fishes than for temperate species. The standard metabolic rate of the two exclusively Arctic species of teleosts was only 10% and 26% higher, respectively, than the two species that occur in temperate as well as Arctic areas. The critical oxygen tension, with respect to oxygen consumption, of resting uvak was between 50 and 60 mmHg, and the lethal oxygen tension 20–25 mmHg at 4.5°C, which is considerably higher than for Atlantic cod from a temperate area measured at the same temperature.

Aerobic capacity influences the spatial position of individuals within fish schools

The schooling behaviour of fish is of great biological importance, playing a crucial role in the foraging and predator avoidance of numerous species. The extent to which physiological performance traits affect the spatial positioning of individual fish within schools is completely unknown. Schools of juvenile mullet Liza aurata were filmed at three swim speeds in a swim tunnel, with one focal fish from each school then also measured for standard metabolic rate (SMR), maximal metabolic rate (MMR), aerobic scope (AS) and maximum aerobic swim speed. At faster speeds, fish with lower MMR and AS swam near the rear of schools. These trailing fish required fewer tail beats to swim at the same speed as individuals at the front of schools, indicating that posterior positions provide hydrodynamic benefits that reduce swimming costs. Conversely, fish with high aerobic capacity can withstand increased drag at the leading edge of schools, where they could maximize food intake while possibly retaining sufficient AS for other physiological functions. SMR was never related to position, suggesting that high maintenance costs do not necessarily motivate individuals to occupy frontal positions. In the wild, shifting of individuals to optimal spatial positions during changing conditions could influence structure or movement of entire schools.

Preferred temperature of juvenile Atlantic cod Gadus morhua with different haemoglobin genotypes at normoxia and moderate hypoxia.

SUMMARY Atlantic cod Gadus morhua has polymorphic haemoglobin, which can be separated into two homozygous types, HbI-1 and HbI-2, and one heterozygous type HbI-1/2. The geographical distribution of Atlantic cod with the different haemoglobin types varies, with the HbI2 allele occurring at high frequency in northern regions, and the HbI1 allele dominant in warmer areas. To determine if temperature is a selective parameter in the distribution of the haemoglobin types, the preferred temperature of the homozygous genotypes HbI-1 and HbI-2 was measured. We found that HbI-2 cod preferred a temperature of 8.2±1.5°C while HbI-1 cod preferred 15.4±1.1°C, and this preference was significant. The effect of hypoxia (35% oxygen saturation) on the preferred temperature was also measured. Previous studies showed that the preferred temperature of fish decreases during hypoxia, and this was the case for HbI-1 cod, which preferred 9.8±1.8°C during hypoxia, whereas HbI-2 cod did not show this effect. The results indicate that environmental temperature changes will lead to a distributional change in the different haemoglobin types of Atlantic cod, global warming providing an advantage for HbI-1 cod. However, since HbI-1 cod prefer a low temperature under hypoxic conditions, a combination of increased water temperature and hypoxia could be unfavourable for Atlantic cod stocks.

Effects of Ration Size and Hypoxia on Specific Dynamic Action in the Cod

We present the first data on the effect of hypoxia on the specific dynamic action (SDA) in a teleost fish. Juvenile cod (Gadus morhua) were fed meals of 2.5% and 5% of their wet body mass (BM) in normoxia (19.8 kPa Po2) and 5% BM in hypoxia (6.3 kPa Po2). Reduced O2 availability depressed the postprandial peaks of oxygen consumption, and to compensate for this, the total SDA duration lasted \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape

Gill ventilation and O2 extraction during graded hypoxia in two ecologically distinct species of flatfish, the flounder (Platichthys flesus) and the plaice (Pleuronectes platessa)

212.0\pm 20

4 – The Secondary Vascular System

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