title: Assessing niche width of endothermic fish from genes to ecosystem.
abstract: Endothermy in vertebrates has been postulated to confer physiological and ecological advantages. In endothermic fish, niche expansion into cooler waters is correlated with specific physiological traits and is hypothesized to lead to greater foraging success and increased fitness. Using the seasonal co-occurrence of three tuna species in the eastern Pacific Ocean as a model system, we used cardiac gene expression data (as a proxy for thermal tolerance to low temperatures), archival tag data, and diet analyses to examine the vertical niche expansion hypothesis for endothermy in situ. Yellowfin, albacore, and Pacific bluefin tuna (PBFT) in the California Current system used more surface, mesopelagic, and deep waters, respectively. Expression of cardiac genes for calcium cycling increased in PBFT and coincided with broader vertical and thermal niche utilization. However, the PBFT diet was less diverse and focused on energy-rich forage fishes but did not show the greatest energy gains. Ecosystem-based management strategies for tunas should thus consider species-specific differences in physiology and foraging specialization.
authors.affiliation: Tuna Research and Conservation Center of Hopkins Marine Station, Stanford University, Pacific Grove, CA 93950; daniel.madigan@stonybrook.edu.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Madigan
authors.affiliation: Tuna Research and Conservation Center of Hopkins Marine Station, Stanford University, Pacific Grove, CA 93950;
authors.forename: Aaron B
authors.initials: AB
authors.lastname: Carlisle
authors.affiliation: Tuna Research and Conservation Center of Hopkins Marine Station, Stanford University, Pacific Grove, CA 93950;
authors.forename: Luke D
authors.initials: LD
authors.lastname: Gardner
authors.affiliation: Tuna Research and Conservation Center of Hopkins Marine Station, Stanford University, Pacific Grove, CA 93950;
authors.forename: Nishad
authors.initials: N
authors.lastname: Jayasundara
authors.affiliation: Hopkins Marine Station, Stanford University, Pacific Grove, CA 93950;
authors.forename: Fiorenza
authors.initials: F
authors.lastname: Micheli
authors.affiliation: Inter-American Tropical Tuna Commission, La Jolla, CA 92037.
authors.forename: Kurt M
authors.initials: KM
authors.lastname: Schaefer
authors.affiliation: Inter-American Tropical Tuna Commission, La Jolla, CA 92037.
authors.forename: Daniel W
authors.initials: DW
authors.lastname: Fuller
authors.affiliation: Tuna Research and Conservation Center of Hopkins Marine Station, Stanford University, Pacific Grove, CA 93950;
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Block
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics* / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002140:California; D017753:Ecosystem; D005247:Feeding Behavior / Q000502:physiology; D029941:Fish Proteins / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression; D005843:Geography; D010140:Pacific Ocean; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000235:genetics / Q000378:metabolism; D013045:Species Specificity; D013696:Temperature; D014413:Tuna / Q000145:classification / Q000235:genetics* / Q000502:physiology
chemical_list: D029941:Fish Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D002118:Calcium
keywords: Thunnus; endothermy; evolution; pelagic; tuna