Grants and Contributions:

Grant or Award spanning more than one fiscal year. (2017-2018 to 2022-2023)

In a country with the longest coastline in the world, with 1/7 of the world’s freshwater, & an economy where fish and fisheries contribute over $17B annually (sportfishing ~ $10B, commercial fishing ~ $6B, aquaculture ~ $1B), the importance of understanding the basic physiology of fish & protecting the health of natural waters cannot be overstated. The present application opens new frontiers in a long term research program aimed at understanding the mechanisms involved in the transport & metabolism of nutrients, wastes, ions, acid-base equivalents, & respiratory gases in fish, & how these processes are modified by environmental conditions & phylogeny. This basic research program underpins a parallel applied program in aquatic toxicology, aquaculture, & environmental management. Mechanisms are analyzed at molecular, cellular, organ system, whole animal, & behavioral levels simultaneously. A comparative approach is used with respect to species (trout, killifish, sharks, hagfish, zebrafish etc.) & stressors (ammonia, O 2 , CO 2 , salinity, exercise, feeding). The four main areas are: (i) the physiology of ammonia & urea metabolism; (ii) the “osmorespiratory compromise” which is the functional tradeoff between ion/water vs O 2 exchange at the gills; (iii) the physiology of feeding; (iv) the importance of dissolved organic matter (DOM, an abundant, ubiquitous but poorly understood component of all natural waters) in regulating gill physiology. Particular projects focus on the functions of NH 3 as a respiratory gas in the regulation of breathing, its interactions with O 2 & CO 2 , the control of gene expression of ammonia-transporting Rh proteins in the gills & kidney, & their roles in the homeostatic regulation of ions, acid-base status, & N-wastes. The mechanisms of N-scavenging are examined in N-limited sharks. The different types of osmorespiratory compromise, the contributions of transcellular vs paracellular pathways, & their cellular/molecular bases are investigated in relation to salinity, habitat, & behaviour of different species. Multiple aspects of feeding physiology are explored, including the importance of acid-base signals, the upregulation of transport pathways associated with food ingestion, & the metabolism of the gut itself. The O 2 costs of feeding & their interactions with hypoxia & exercise performance are quantified. Through collaboration with a chemist, the relationships between the physical chemistry of different types of DOM molecules & their supportive actions on gill ionoregulatory function are examined. Particular emphasis is placed on the role(s) of metal-binding moieties in DOM molecules, on structural changes in gills associated with DOM exposures, & on the adaptation of fish to native DOMs. Overall, this program will train 3 postdoctoral fellows, 5 PhDs, & 15 undergrads in innovative aspects of integrative fish physiology.