Chris Wood. 2022. Chapter 7: Conservation aspects of osmotic, acid-base, and nitrogen homeostasis in fish. Fish Physiology, volume 39, Part A, 2022, Pages 321-388.
The basic mechanisms of iono/osmoregulation, acid-base regulation, and homeostasis and excretion of nitrogenous wastes (ammonia and urea) are reviewed for freshwater fish, marine and euryhaline fish, and for special cases (marine hagfish and chondrichthyans). Six different examples are then explored where physiological understanding of environmental impacts on these processes has already informed regulatory and conservation strategies, or should do so in the future. These include: (i) the acid-rain crisis; (ii) survival of fishes in the acidic, ion-poor blackwaters of the Rio Negro; (iii) development of the Biotic Ligand Model for environmental regulation of metals; (iv) survival of fishes in highly alkaline lakes; (v) the commercial hagfish fishery; and (vi) the critical importance of feeding for osmoregulation in chondrichthyans. These lessons argue for a greater awareness of the wide-spread variation in the physical chemistry of natural waters, and the associated physiology of the fish that live there. This knowledge should be incorporated into regulatory strategies for both environmental protection and conservation of resident species at risk.