Air‐breathing fishes in aquaculture. What can we learn from physiology?

Abstract

During the past decade, the culture of air-breathing fish species has increased dramatically and is now a significant global source of protein for human consumption. This development has generated a need for specific information on how to maximize growth and minimize the environmental effect of culture systems. Here, the existing data on metabolism in air-breathing fishes are reviewed, with the aim of shedding new light on the oxygen requirements of air-breathing fishes in aquaculture, reaching the conclusion that aquatic oxygenation is much more important than previously assumed. In addition, the possible effects on growth of the recurrent exposure to deep hypoxia and associated elevated concentrations of carbon dioxide, ammonia and nitrite, that occurs in the culture ponds used for air-breathing fishes, are discussed. Where data on air-breathing fishes are simply lacking, data for a few water-breathing species will be reviewed, to put the physiological effects into a growth perspective. It is argued that an understanding of air-breathing fishes' respiratory physiology, including metabolic rate, partitioning of oxygen uptake from air and water in facultative air breathers, the critical oxygen tension, can provide important input for the optimization of culture practices. Given the growing importance of air breathers in aquaculture production, there is an urgent need for further data on these issues.

Air breathing in the Arctic: influence of temperature, hypoxia, activity and restricted air access on respiratory physiology of Alaska blackfish (Dallia pectoralis)

“…5D) was even lower than that measured under resting conditions (Fig. 3 The standard Ṁ O2 values of Alaska blackfish measured in the present study are comparable to previous measurements on Alaska blackfish (Scholander et al, 1953;Crawford, 1971), as well as to values obtained for other air-breathing fishes (Lefevre et al, 2014c). It is interesting that up to 10 h was required for the Alaska blackfish to enter a resting state in the bimodal respirometer, but a similar pattern has been observed in the striped catfish Pangasianodon hypopthalmus (Lefevre et al, 2011).…”

“…A similar P crit has even been reported for Alaska blackfish at 20°C (Crawford, 1971). The P crit is well above the 1-4 kPa typical of hypoxia-tolerant teleosts (Nilsson and Randall, 2010), but falls within the range of P crit values reported for other air-breathing species (Lefevre et al, 2014c). The effect of temperature acclimation on the P crit of air-breathing fish has, to our knowledge, only been…”

High capacity for extracellular acid-base regulation in the air-breathing fishPangasianodon hypophthalmus

“…It might also be a consequence of a low HCO 3 − /Cl − -exchanger activity, augmenting HCO 3 − retention, which would be consistent with the proposed low Cl − permeability of the gill of P. hypophthalmus, as indicated by a low uptake rate of nitrite (Lefevre et al, 2011c). Both characteristics contrast with those of other air-breathing fishes (Graham, 1997;Lefevre et al, 2014;Tamura and Moriyama, 1976). Other mechanisms may contribute to the high regulatory capacity for pH e regulation in P. hypophthalmus, such as H + /Na + exchange, greater renal or intestinal contribution in acid-base regulation, the ability to excrete CO 2 across the air-breathing organ etc.…”

Lactate provides a strong pH-independent ventilatory signal in the facultative air-breathing teleost Pangasianodon hypophthalmus

“…Thus, at PO 2 tensions above 60 mmHg we saw an increased gill ventilation, stemming mainly from increased V amp , as was the case with lactate and NaCN injections (Figs 2 and 4) 10, 21, 37 . Hypoxia impairs growth in this species 38, 39 , in part from elevated energetic costs of air-breathing 40 , but the present data suggest that increased gill ventilation in moderate hypoxia might also contribute to the increased energetic costs. In more severe hypoxia (P w O 2  < 40 mmHg), gill ventilation started to decline as air-breathing rose (Fig.…”