Global climate change is altering freshwater ecosystems and affecting fish populations and communities. Underpinning changes in fish distribution and assemblage‐level responses to climate change are individual‐level physiological constraints. In this review, we synthesize the mechanistic effects of climate change on neuroendocrine, cardiorespiratory, immune, osmoregulatory, and reproductive systems of freshwater and diadromous fishes. Observed climate change effects on physiological systems are varied and numerous, including exceedance of critical thermal tolerances, decreased cardiorespiratory performance, compromised immune function, and altered patterns of individual reproductive investment. However, effects vary widely among and within species because of species, population, and even sex‐specific differences in sensitivity and resilience and because of habitat‐specific variation in the magnitude of climate‐related environmental change. Research on the interactive effects of climate change with other environmental stressors across a broader range of fish diversity is needed to further our understanding of climate change effects on fish physiology.

No abstract

Using critical thermal maximum (CTMax) tests, we examined the relationship between upper temperature tolerances and fish size (fry–adult or subadult lengths) of rainbow trout Oncorhynchus mykiss (41–200‐mm TL), Apache trout O. gilae apache (40–220‐mm TL), largemouth bass Micropterus salmoides (72–266‐mm TL), Nile tilapia Oreochromis niloticus (35–206‐mm TL), channel catfish Ictalurus punctatus (62–264 mm‐TL), and Rio Grande cutthroat trout O. clarkii virginalis (36–181‐mm TL). Rainbow trout and Apache trout were acclimated at 18°C, Rio Grande cutthroat trout were acclimated at 14°C, and Nile tilapia, largemouth bass, and channel catfish were acclimated at 25°C, all for 14 d. Critical thermal maximum temperatures were estimated and data were analyzed using simple linear regression. There was no significant relationship (P > 0.05) between thermal tolerance and length for Nile tilapia (P = 0.33), channel catfish (P = 0.55), rainbow trout (P = 0.76), or largemouth bass (P = 0.93) for the length ranges we tested. There was a significant negative relationship between thermal tolerance and length for Rio Grande cutthroat trout (R2 = 0.412, P < 0.001) and Apache trout (R2 = 0.1374, P = 0.028); however, the difference was less than 1°C across all lengths of Apache trout tested and about 1.3°C across all lengths of Rio Grande cutthroat trout tested. Because there was either no or at most a slight relationship between upper thermal tolerance and size, management and research decisions based on upper thermal tolerance should be similar for the range of sizes within each species we tested. However, the different sizes we tested only encompassed life stages ranging from fry to adult/subadult, so thermal tolerance of eggs, alevins, and larger adults should also be considered before making management decisions affecting an entire species.

Natal origin and dispersal potential of the federally threatened Pecos bluntnose shiner (Notropis simus pecosensis) were successfully characterized using otolith microchemistry and swimming performance trials. Strontium isotope ratios ( 87 Sr: 86 Sr) of otoliths within the resident plains killifish (Fundulus zebrinus) were successfully used as a surrogate for strontium isotope ratios in water and revealed three isotopically distinct reaches throughout 297 km of the Pecos River, New Mexico, USA. Two different life history movement patterns were revealed in Pecos bluntnose shiner. Eggs and fry were either retained in upper river reaches or passively dispersed downriver followed by upriver movement during the first year of life, with some fish achieving a minimum movement of 56 km. Swimming ability of Pecos bluntnose shiner confirmed upper critical swimming speeds (U crit ) as high as 43.8 cm·s −1 and 20.6 body lengths·s −1 in 30 days posthatch fish. Strong swimming ability early in life supports our observations of upriver movement using otolith microchemistry and confirms movement patterns that were previously unknown for the species. Understanding patterns of dispersal of this and other small-bodied fishes using otolith microchemistry may help redirect conservation and management efforts for Great Plains fishes.Résumé : L'origine natale et le potentiel de dispersion du méné (Notropis simus pecosensis), une espèce menacée au niveau fédéral, ont été caractérisés avec succès par la microchimie des otolithes et des essais de performance natatoire. Les rapports d'isotopes de strontium ( 87 Sr: 86 Sr) des otolithes chez le fondule résident (Fundulus zebrinus) ont été utilisés comme substituts des rapports d'isotopes de strontium dans l'eau et ont révélé trois tronçons distincts sur le plan isotopique le long de 297 km de la rivière Pecos (Nouveau-Mexique, États-Unis). Deux motifs distincts de déplacements associés au cycle biologique ont été décelés chez méné. Les oeufs et les alevins étaient soit retenus dans des tronçons supérieurs de la rivière ou dispersés passivement vers l'aval pour ensuite se déplacer vers l'amont durant la première année de vie, le déplacement minimum de certains poissons atteignant 56 km. La capacité natatoire de méné a confirmé des vitesses de nage critiques supérieures (U crit ) pouvant atteindre 43,8 cm·s -1 et 20,6 longueurs du corps·s -1 30 jours après l'éclosion des poissons. Une bonne capacité natatoire tôt durant la vie appuie nos observations de déplacements vers l'amont obtenues de la microchimie des otolithes et confirme des motifs de déplacement jusqu'ici inconnus pour cette espèce. La compréhension des motifs de dispersion de cette espèce et d'autres poissons à petit corps à l'aide de la microchimie des otolithes pourrait aider à réorienter les efforts de conservation et de gestion des poissons des grandes plaines de l'Ouest. [Traduit par la Rédaction]

The Rio Grande Cutthroat Trout Oncorhynchus clarkii virginalis is the southernmost subspecies of Cutthroat Trout, and as with the other subspecies, stream temperature regulates growth, reproductive success, distribution, and survival. An understanding of the upper thermal tolerance of Rio Grande Cutthroat Trout is important for developing water temperature standards and for assessing suitable habitat for reintroduction and management. Hatch success of Rio Grande Cutthroat Trout eggs was determined under static temperatures. The thermal requirements of fry and juveniles were also assessed under static and fluctuating temperature regimes using the acclimated chronic exposure method. Egg hatch success was 46-70% from 6 • C to 16 • C but declined significantly at 18 • C and 20 • C. Maximum growth of fry that were fed to satiation occurred at 15.3 • C. The 30-d ultimate upper incipient lethal temperature (UUILT) was 22.6 • C for fry and 21.7 • C for juveniles. Survival during fluctuating temperature experiments was dependent upon the daily maximum temperature and the daily fluctuation. The upper thermal limits for Rio Grande Cutthroat Trout were lower than those of Rainbow Trout O. mykiss but similar to those of other Cutthroat Trout subspecies. The low UUILT of Rio Grande Cutthroat Trout relative to some salmonids may increase the risk of deleterious effects brought about by a changing climate, habitat alteration, and sympatric nonnative salmonids, which are known to outcompete Cutthroat Trout at temperatures above the species' optimal range. Daily mean water temperatures near the Rio Grande Cutthroat Trout's optimal growth temperature of 15 • C would be suitable 1395 1396 ZEIGLER ET AL.for reintroduction of this subspecies. Depending on the daily temperature fluctuation, daily maximum temperatures within reintroduction streams and current habitat should remain at or below 25 • C to ensure long-term persistence of a Rio Grande Cutthroat Trout population. This information will aid in establishing water quality standards to protect habitat where the subspecies currently occurs.

No abstract

No abstract

This research was initiated to characterize atmospheric deposition of reactive gaseous mercury (RGM), particulate mercury (HgP; <2.5 microm), and gaseous elemental mercury (Hg0) in the arid lands of south central New Mexico. Two methods were field-tested to estimate dry deposition of three mercury species. A manual speciation sampling train consisting of a KCl-coated denuder, 2.5 microm quartz fiber filters, and gold-coated quartz traps and an ion-exchange membrane (as a passive surrogate surface) were deployed concurrently over 24-h intervals for an entire year. The mean 24-h atmospheric concentration for RGM was 6.8 pg m(-3) with an estimated deposition of 0.10 ng m(-2) h(-1). The estimated deposition of mercury to the passive surrogate surface was much greater (4.0 ng m(-2) h(-1)) but demonstrated a diurnal pattern with elevated deposition from late afternoon to late evening (1400-2200; 8.0 ng m(-2) h(-1)) and lowest deposition during the night just prior to sunrise (2200-0600; 1.7 ng m(-2) h(-1)). The mean 24-h atmospheric concentrations for HgP and Hg0 were 1.52 pg m(-3) and 1.59 ng m(-3), respectively. Diurnal patterns were observed for RGM with atmospheric levels lowest during the night prior to sunrise (3.8 pg m(-3)) and greater during the afternoon and early evening (8.9 pg m(-3)). Discernible diurnal patterns were not observed for either HgP or Hg0. The total dry deposition of Hg was 5.9 microg m-2 year-' with the contribution from the three species as follows: RGM (0.88 microg m(-2) year(-1)), HgP (0.025 microg m(-2) year(-1)), and Hg0 (5.0 microg m(-2) year(-1)). The annual wet deposition for total mercury throughout the same collection duration was 4.2 microg m(-2) year (-1), resulting in an estimated total deposition of 10.1 microg m(-2) year(-1) for Hg. On one sampling date, enhanced HgP (12 pg m(-3)) was observed due to emissions from a wildfire approximately 250 km to the east.