Hypoxia tolerance in Atlantic cod

Abstract

Oxygen saturation levels that killed 50 and 5% of cod Gadus morhua over 96 h averaged 21·2 and 27·7%, respectively. No fish survived at 10% saturation and only a few survived at 16% saturation, whereas no mortality occurred at 34 and 40% oxygen saturation. Since metabolic rate and oxygen consumption increase with increasing temperature, we hypothesized that cod would be less tolerant to hypoxic conditions at 6 than at 2 C. However, temperature (2 and 6 C) had no measurable impact on cod survival. Small (mean ..; 45·2 4·2 cm) and large (57·5 3·8 cm) cod had the same tolerance to hypoxia. At the end of the experiments, hypoxia had a significant effect on blood haematocrit, mean cellular haemoglobin content, liver lactate, plasma glucose and plasma lactate, but accounted for only a small fraction (<10%) of the variation, except for plasma lactate which exhibited a strong response with concentrations increasing progressively with decreasing levels of oxygen saturation. Temperature had a significant effect on most variates in normoxia and hypoxia. Variates also affected by oxygen level showed significant interactions between oxygen and size or temperature effects. However, these interactions accounted for only a small proportion of the variation. Physiological parameters indicated that extending the duration of our tests beyond 96 h would not have changed our estimates of the lethal thresholds. Hypoxic conditions are a permanent feature of the deep waters of the Gulf of St Lawrence. This study shows that a significant portion of the benthic habitats in the Gulf are uninhabitable for cod which would be expected to avoid waters below 28% oxygen saturation. 1998 The Fisheries Society of the British Isles

Burst and coast use, swimming performance and metabolism of Atlantic cod Gadus morhua in sub‐lethal hypoxic conditions

“…At this level, aerobic scope is reduced (Claireaux et al, 2000) and further decreases with declining oxygen saturation. When saturation reaches 20%, which is close to LC 50 values for the species at both 2 and 6°C (Plante et al, 1998), scope for activity at any temperature (range 2-10°C) becomes zero (Claireaux et al, 2000).…”

“…Bottom waters in the channels are warmer than in the overlying cold intermediate layer, with the disadvantage of a poor oxygen content (D'Amours, 1993). While Atlantic cod may avoid extreme temperature conditions (D'Amours, 1993;Castonguay et al, 1999), particularly during summer, and may avoid lethal oxygen conditions (D'Amours, 1993;Plante et al, 1998), low and continually decreasing oxygen levels on the bottom in the channels (Gilbert et al, 2005) may limit their growth and survival capacity. A similar situation may prevail in the Baltic Sea (Mattha¨us & Franck, 1992;Neuenfeldt, 2002).…”

“…Atlantic cod in the northern Gulf of St Lawrence avoid areas where oxygen saturation levels are low (D’Amours, 1993). Mortalities are observed at <28% saturation (LC 05 ) in the laboratory (Plante et al , 1998). At this level, aerobic scope is reduced (Claireaux et al , 2000) and further decreases with declining oxygen saturation.…”

Anguilla rostrata glass eel migration and recruitment in the estuary and Gulf of St Lawrence

“…Oxygen levels have decreased over the last 75 years and now reach saturation levels < 20% (Gilbert et al ., 2005). The swimming capacity of Atlantic cod Gadus morhua L. is reduced in hypoxia with very poor performances observed at 35% saturation and mortalities occurring below 28% saturation (Plante et al ., 1998; Dutil et al ., 2007).…”

Effects of Hypoxia on the Behaviour, Mortality and Plasma Electrolyte Concentrations of Goldlined Seabream, Rhabdosargus sarba

“…Fish were kept in oxygenated seawater while on board and transferred to well-aerated tanks on land where the water temperature and salinity were kept at 21-24°C and 20-25 psu. Fish were acclimatized for a total of 3 weeks during which they were fed once daily (Plante, et al, 1998) with commercially-prepared fish pellets (Arasco, Saudi Arabia).…”