Thermal Refugia Research Articles

Tolerance of nonindigenous cichlid fishes (Cichlasoma urophthalmus, Hemichromis letourneuxi) to low temperature: laboratory and field experiments in south Florida

The cold tolerance of two non-native cichlids (Hemichromis letourneuxi and Cichlasoma urophthalmus) that are established in south Florida was tested in the field and laboratory. In the laboratory, fishes were acclimated to two temperatures (24 and 28°C), and three salinities (0, 10, and 35 ppt). Two endpoints were identified: loss of equilibrium (11.5–13.7°C for C. urophthalmus; 10.8–12.5°C for H. letourneuxi), and death (9.5–11.1°C for C. urophthalmus; 9.1–13.3°C for H. letourneuxi). In the field, fishes were caged in several aquatic habitats during two winter cold snaps. Temperatures were lowest (4.0°C) in the shallow marsh, where no fish survived, and warmest in canals and solution-holes. Canals and ditches as shallow as 50 cm provided thermal refuges for these tropical fishes. Because of the effect on survival of different habitat types, simple predictions of ultimate geographic expansion by non-native fishes using latitude and thermal isoclines are insufficient for freshwater fishes.

Massartella hirsuta sp. nov. (Ephemeroptera: Leptophlebiidae: Atalophlebiinae) and new data on mayflies of Guyana Highlands

Description and figures of the larva and egg of Massartella hirsuta sp. nov. (Ephemeroptera: Leptophlebiidae) from the south-eastern part of Grand Sabana region (Venezuela) are presented. Diagnostic characters distinguishing the larvae of this species from other known Massartella species include a heavy row of setae along the entire outer margin of the mandibles. This character, among others, will also distinguish the new species from undescribed species of Massartella from the sandstone table mountains. Two well-defined species groups of the genus Massartella can be distinguished in the Guyana Highlands: (1) M. venezuelensis group including M. venezuelensis and M. hirsuta sp. nov., and (2) M. devani group containing M. devani and undescribed taxa from Mt. Roraima and Mt. Chimantá plateaus. The first group seems to be distributed in uplands (∼1000 m a.s.l.), while the second group appeared to be restricted to the thermal refugia above 2000 m a.s.l. The origin of Massartella species in Guyana Highlands is discussed.

Insect eggs protected from high temperatures by limited homeothermy of plant leaves

Virtually all aspects of insect biology are affected by body temperature, and many taxa have evolved sophisticated temperature-control mechanisms. All insects, however, begin life as eggs and lack the ability to thermoregulate. Eggs laid on leaves experience a thermal environment, and thus a body temperature, that is strongly influenced by the leaves themselves. Because plants can maintain leaf temperatures that differ from ambient, e.g. by evapotranspiration, plant hosts may protect eggs from extreme ambient temperatures. We examined the degree to which leaves buffer ambient thermal variation and whether that buffering benefits leaf-associated insect eggs. In particular, we: (1) measured temperature variation at oviposition sites in the field, (2) manipulated temperatures in the laboratory to determine the effect of different thermal conditions on embryo development time and survival, and (3) tested embryonic metabolic rates over increasing temperatures. Our results show that Datura wrightii leaves buffer Manduca sexta eggs from fatally high ambient temperatures in the southwestern USA. Moreover, small differences in temperature profiles among leaves can cause large variation in egg metabolic rate and development time. Specifically, large leaves were hotter than small leaves during the day, reaching temperatures that are stressfully high for eggs. This study provides the first mechanistic demonstration of how this type of leaf-constructed thermal refuge interacts with egg physiology.

Behavioral thermoregulation and associated mortality trade-offs in migrating adult steelhead (Oncorhynchus mykiss): variability among sympatric populations

We used radiotelemetry to assess thermoregulatory behaviors for 14 populations (n = 3985) of adult summer steelhead ( Oncorhynchus mykiss ) as they passed through the Columbia River migration corridor. Steelhead use of small cool-water tributaries (“thermal refugia”) rapidly increased when the Columbia River reached a temperature threshold of about 19 °C. When main stem temperatures were warmest (i.e., >21 °C), more than 70% of the tagged fish used refugia sites and these fish had median refugia residence times of 3–4 weeks. Thermoregulatory responses were similar across populations, but there were large among-population differences in the incidence and duration of refugia use likely linked to population-specific migration timing patterns. In survival analyses using 1285 known-origin steelhead, fish that used thermal refugia were significantly less likely to survive to natal basins, were harvested at relatively high rates in refugia tributaries, and had greater unknown mortality in the main stem. These results highlight the trade-off between the presumed physiological benefits of thermal refugia use and a likely increase in harvest and other mortality risks that arise when preferred thermal habitats are severely constricted.

Interactions between non-native armored suckermouth catfish (Loricariidae: Pterygoplichthys) and native Florida manatee (Trichechus manatus latirostris) in artesian springs

Non-native suckermouth armored catfishes (Loricariidae) of the genus Pterygoplichthys are now common throughout much of peninsular Florida. In this paper, we present preliminary observations on interactions between a Pterygoplichthys species, tentatively identified as P. disjunctivus (Weber, 1991), and endangered native Florida manatees, Trichechus manatus latirostris (Harlan, 1824), in artesian spring systems in Florida's St. Johns River drainage. The introduced catfish have become abundant in spring habitats, sites used by manatees as winter thermal refuges. In the spring runs, Pterygoplichthys regularly attaches to manatees and grazes the epibiota on their skin. On occasion, dozens of Pterygoplichthys congregate on individual manatees. Manatee responses varied widely; some did not react visibly to attached catfish whereas others appeared agitated and attempted to dislodge the fish. The costs and/or benefits of this interaction to manatees remain unclear.

Site Fidelity, Home Range, and Tidal Movements of White Perch during the Summer in Two Small Tributaries of the York River, Virginia

AbstractThe white perch Morone americana is one of the most common species residing in the brackish tributaries of Chesapeake Bay. White perch make long‐distance movements during spring spawning events and find thermal refuge in the winter; however, little is known about their movements in the summer. This study tracked 16 white perch that were implanted with acoustic tags during the summer in two small tributaries of the York River, Virginia. Site fidelity, tidal interactions, and habitat effects were investigated with the program ArcView. If site fidelity existed, a home range and utilization distribution (frequently used locations) were calculated. Most of the tagged fish exhibited site fidelity; for those that did, home ranges averaged 0.11 km2. White perch only frequented a small portion of their home range, as depicted by utilization distributions equal to 10% or less of the home range. White perch exhibiting site fidelity displayed one of two different behavioral patterns based upon the surrounding habitat. White perch associated with a marsh habitat used two core areas of activity. The fish were located during high tide upon the flooded marsh and shallow creeks, possibly to forage, and in the relatively deep main channels during low tide, thus avoiding stranding and avian predators. In contrast, white perch associated with submerged structures had only one core area of activity, typically remaining around the one location for the duration of the tag's battery life. The relatively small home range of white perch makes this species vulnerable to local stressors and habitat degradation.

Hypoxia affects spatial distributions and overlap of pelagic fish, zooplankton, and phytoplankton in Lake Erie

Bottom hypoxia has reemerged as a prominent feature of Lake Erie's central basin during late summer. Similar to coastal and marine systems, the influence of hypoxia on pelagic organisms remains largely enigmatic in Lake Erie. During 2005, we used a plankton survey system (a sensor package consisting of an optical plankton counter, fluorometer, dissolved oxygen sensor, light sensor, and conductivity–temperature–depth sensor), coupled with a fish hydroacoustics system, to explore how the distribution of phytoplankton (chlorophyll), mesozooplankton, and fish varied vertically and horizontally in relation to oxygen concentrations. To do so, we conducted surveys of the entire water column on a continuous basis during mild (August) and severe (September) hypoxia. Our surveys included two sampling designs: 1) basin-wide transects sampled during day and night to define broad-scale patterns of spatial overlap among pelagic organisms; and 2) shorter (5 km) transects sampled every 4 h over a 24-h period to explore how diel vertical migration and hypoxia interact to affect time-specific spatial overlap among fishes, mesozooplankton, and phytoplankton. Our findings indicated that fish avoided regions of the hypolimnion with dissolved oxygen concentrations < 3 mg l − 1 by 1) moving horizontally into areas with higher oxygen or 2) moving vertically into the metalimnion, where a sharp thermocline and oxycline existed. A portion of the mesozooplankton continued to use the hypoxic hypolimnion as a refuge from fish predation during daytime at oxygen concentrations between 1 and 3 mg l − 1 ; however, there was usually a mesozooplankton maximum in the metalimnion, even when fish were compressed into this region. Prior to development of hypoxia, the metalimnion in some areas may have served as thermal refuge from predation from the epilimnetic planktivore, the emerald shiner, and the hypolimnetic planktivore–benthivore, the rainbow smelt. Overall, the horizontal compression of fish into less-hypoxic regions in the deep area of the central basin followed by vertical compression into the metalimnion as hypoxia developed further may have led to local reduction of mesozooplankton prey in these regions. Herein, we discuss the potential implications of these hypoxia-induced impacts for understanding food web interactions and fisheries management.

Lake morphometry predicts the degree of habitat coupling by a mobile predator

Habitat coupling is an ecosystem process whereby semi‐discontinuous habitats are connected through the movement of energy and nutrients by chemical, physical or biological processes. One oft‐cited example is that of littoral–pelagic coupling in lakes. Theory has argued that such habitat coupling may be critical to food web dynamics, yet there have been few empirical studies that have quantified ecological factors that affect the degree of habitat coupling in ecosystems. Specifically, the degree to which habitat coupling occurs across important physical gradients has largely been ignored. To address this, we investigate the degree of littoral habitat coupling (i.e. the degree to which a top predator lake trout, Salvelinus namaycush, derives energy from the littoral zone) along a gradient of lake shape, where lake shape modifies the relative quantity of coupled epilimnetic benthic and pelagic habitats within each lake. Herein we demonstrate that littoral habitat coupling is intensified in simple circular lakes compared to their reticulate counterparts in seven Canadian Shield lakes. Although the more reticulate lakes had larger areas of epilimnetic benthic habitat, littoral food sources comprised 11% compared to 24% of lake trout diet in reticulate and circular lakes, respectively. This heightened interaction in circular lakes also appears to translate into increased omnivory in more circular lakes compared to reticulate lakes such that lake trout of circular lakes have a significantly lower trophic position than lake trout of reticulate lakes (F1,5=6.71 p=0.05). These results suggest that it is the accessibility of littoral production via thermal refugia, and not the amount of littoral production, that determines the degree to which lake trout couple littoral and pelagic habitats in lakes.

Movements of Prespawn Adult Atlantic Salmon Near Hydroelectric Dams in the Lower Penobscot River, Maine

AbstractAcoustic telemetry was used to assess riverine behavior and passage success for prespawn male adult Atlantic salmon Salmo salar in the lower Penobscot River, Maine, in 2005 (n = 10) and 2006 (n = 25). Only 3 of 10 (30%) and 2 of 25 (8%) tagged Atlantic salmon successfully passed all three dams between the head of tide and presumed spawning habitat in 2005 and 2006, respectively. Migrants that failed to pass the second upstream dam frequently fell back into the estuary (3 of 4 in 2005; 17 of 23 in 2006), and few successfully reascended Veazie Dam at the head of tide. Fallback behavior was associated with temperatures exceeding 22°C and may reflect a strategy for coping with thermal stress and migratory delays. Atlantic salmon were also observed to actively seek out thermal refuge near one of the dams. Passage data were compared with results from previous telemetry studies that used Carlin tags and radio telemetry from 1987–1990 and 1992, and passive integrated transponder tags from 2002–2004. For all 10 years of study combined, median passage success was 64, 72, and 93% for the three dams. While 2006 may represent an uncommonly poor year for upstream passage at these dams, median cumulative passage past two of these dams was only 71% and ranged from 8% to 87% among years. Study results indicate that poor upstream passage severely limits migratory success in this system, particularly during periods of high discharge. Planned removal of two of these lower river dams is expected to improve migratory success for adult Atlantic salmon in the Penobscot River system.

Characteristics of Summer and Fall Diurnal Resting Habitat Used by American Martens in Coastal Northwestern California

American martens use resting habitat between periods of activity to provide both thermal refugia and protection from predators. Maintenance or restoration of key elements of marten resting habitat, such as resting structures, requires that managers recognize their characteristics to protect them, or manage for their creation. We measured resting habitat at 4 scales : (1) the resting location—where the marten actually rested; (2) the resting structure—the habitat element that contained the resting location; (3) the resting site—characteristics in the immediate vicinity of each resting structure; and (4) the resting stand—the forest stand containing the resting structure. During the summer and fall of 2001 and 2002 we identified resting structures used by 12 radio-collared martens (7 Male, 5 Female) and 1 uncollared marten. The animals were the members of the only remnant population of martens within the historical range of the Humboldt marten (M. a. humboldtensis). The study area included portions of the Six Rivers National Forest, Smith River National Recreation Area, and adjacent Green Diamond Resource Company lands in coastal northwestern California. We located martens resting on 55 occasions in the following types of structures: snags (37%), logs (23%), live-trees (17%), slash-piles (10%), rock-piles (8%), and shrub clumps (6%). The location in the structure where the marten actually rested was determined on 92% of occasions and included chambers (33%), cavities (33%), broken tops (22%), branch platforms (6%), ground sites (6%), and basal hollows (2%). Woody structures were large, with mean dbh of 93.9 cm for live-trees , 94.9 cm for snags, and 88.2 cm maximum-diameter for logs. The mean age of 24 of the woody resting structures was 339 years (range 131–666 years). Our results are consistent with results from other studies on resting structure use and highlight the importance of large live and dead woody structures for American martens in coastal forests of northwestern California.

Modelling phase shifts in a rocky subtidal ecosystem

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 375:25-39 (2009) - DOI: https://doi.org/10.3354/meps07758 Modelling phase shifts in a rocky subtidal ecosystem Jean-Sébastien Lauzon-Guay1,*, Robert E. Scheibling2, Myriam A. Barbeau1 1Biology Department, University of New Brunswick, Bag Service 45111, Fredericton, New Brunswick E3B 6E1, Canada 2Biology Department, Dalhousie University, Halifax, Nova Scotia B3H 4J1, Canada *Email: js.lauzon@unb.ca ABSTRACT: The rocky subtidal ecosystem of the Atlantic coast of Nova Scotia is characterised by 2 community states, kelp beds and urchin barrens that alternate on a decadal time scale. While the shift from barrens to a kelp bed requires a large perturbation, namely a disease outbreak causing urchin mass mortality, the reverse shift is more gradual and mediated by the formation and propagation of destructive grazing aggregations (or fronts) of sea urchins Strongylocentrotus droebachiensis. We have developed a spatial model for the re-establishment of kelp beds and the formation of a feeding front of urchins in order to describe transitions (phase shifts) between kelp bed and barrens states following an urchin mass mortality event. Our model includes size-specific movement, growth, and survival of urchins, as well as growth of kelp and grazing by urchins. The position of the kelp bed–barrens interface (or grazing front) predicted by our model is in general agreement with field observations at 2 sites and for up to 7 yr after a mass mortality event. Elasticity analysis showed that daily foraging movements by individual urchins have the greatest effect on the position of the feeding front and the density of the urchins there. Survival and recruitment rates of urchins also have large effects on urchin density at the front. The density of urchin populations in deep-water thermal refuges (from a disease agent) and the distance between these source populations and remnant or emergent kelp beds have large effects on the time required for the re-formation of a feeding front after an event of urchin mass mortality. These findings suggest that site-specific characteristics should be taken into account in the development of sustainable harvesting strategies and habitat-based management of the urchin fishery. KEY WORDS: Alternative states · Feeding front · Sea urchins · Strongylocentrotus droebachiensis · Kelp beds · Phase shifts · Population dynamics · Mathematical modelling Full text in pdf format PreviousNextCite this article as: Lauzon-Guay JS, Scheibling RE, Barbeau MA (2009) Modelling phase shifts in a rocky subtidal ecosystem. Mar Ecol Prog Ser 375:25-39. https://doi.org/10.3354/meps07758 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 375. Online publication date: January 26, 2009 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2009 Inter-Research.

Heterogeneity of Thermal Extremes: Driven by Disturbance or Inherent in the Landscape

Ecologists are beginning to recognize the effect of heterogeneity on structure and function in arid and semiarid ecosystems. Additionally, the influences of temperature on ecosystems are widely documented, but landscape temperature patterns and relationships with vegetation are rarely reported in ecological studies. To better understand the importance of temperature patterns to the conservation and restoration of native ecosystems, we designed an experiment to investigate relationships among soil surface temperature, landscape heterogeneity, and grazing intensity. Grazing intensity did influence the vegetation structure and composition. Heavy treatments had the greatest bare ground and the least vertical structure. Ungrazed treatments had the most litter and live grass cover. However, average temperatures among the three grazing treatments were not different and ranged less than 2 degrees C during midday summer periods. The temperature difference between riparian and upland landscapes within grazing treatments was 21 degrees C. Landscape position (riparian vs. upland) did have a significant influence on soil surface temperature and produced a variation in temperature 11 times greater than grazing intensities. Thermal heterogeneity did not differ among grazing treatments. Lower soil surface temperatures (associated with riparian areas) may provide a critical thermal refuge for many animals in arid and semiarid ecosystems on hot summer days, when air temperatures can exceed 37 degrees C. Riparian zones, specifically riparian vegetation, are an important component in ecosystem management.

Summer temperature variation and implications for juvenile Atlantic salmon

Temperature is important to fish in determining their geographic distribution. For cool- and cold-water fish, thermal regimes are especially critical at the southern end of a species’ range. Although temperature is an easy variable to measure, biological interpretation is difficult. Thus, how to determine what temperatures are meaningful to fish in the field is a challenge. Herein, we used the Connecticut River as a model system and Atlantic salmon (Salmo salar) as a model species with which to assess the effects of summer temperatures on the density of age 0 parr. Specifically, we asked: (1) What are the spatial and temporal temperature patterns in the Connecticut River during summer? (2) What metrics might detect effects of high temperatures? and (3) How is temperature variability related to density of Atlantic salmon during their first summer? Although the most southern site was the warmest, some northern sites were also warm, and some southern sites were moderately cool. This suggests localized, within basin variation in temperature. Daily and hourly means showed extreme values not apparent in the seasonal means. We observed significant relationships between age 0 parr density and days at potentially stressful, warm temperatures (≥23°C). Based on these results, we propose that useful field reference points need to incorporate the synergistic effect of other stressors that fish encounter in the field as well as the complexity associated with cycling temperatures and thermal refuges. Understanding the effects of temperature may aid conservation efforts for Atlantic salmon in the Connecticut River and other North Atlantic systems.

Fish community responses to ecosystem stressors in coastal estuarine wetlands: a functional basis for wetlands management and restoration

Functional responses of estuarine fish species to environmental perturbations such as wetland impoundment, changes in water quality, and sediment accretion are investigated. The study focuses on the feeding, growth and habitat use by California killifish (Fundulus parvipinnis), topsmelt (Antherinops affinis), and juvenile California halibut (Paralichthys californicus) in impacted coastal wetlands to provide an ecological basis for guidance on the management and restoration of these ecosystems. The ecology of California killifish, Fundulus parvipinnis, is closely tied with the marsh surface, which they access at high tide to feed and grow. Field estimates of food consumption show that killifish can increase their food intake by two-fold to five-fold by adding marsh surface foods to their diet. Bioenergetics modeling predicts that killifish can grow over an order of magnitude faster if they add intertidal marsh surfaces to their subtidal feeding areas. Tidal inlet closures and increased marsh surface elevations due to sediment accretion can restrict killifish access to the marsh surface, affecting its growth and fitness. An open tidal inlet and tidal creek networks that allow killifish to access the marsh at high tide must be incorporated into the restoration design. Topsmelt and California halibut are also adversely affected by tidal inlet closures. Food consumption rates of topsmelt are 50% lower when the tidal inlet is closed, compared to when the estuary is tidally-flushed. Tidal inlet closures inadvertently induce variations in water temperature and salinity and negatively affect growth of juvenile California halibut. Tidal creek networks which consist of channels and creeks of various orders are also important to halibut. Large halibut (>200 mm TL) inhabit deeper, high order channels for thermal refuge, while small halibut (<120 mm TL) are abundant in lower order channels where they can feed on small-sized prey which are typically less abundant in high order channels. Maintaining an open tidal inlet, implementing sediment management programs and designing coastal wetlands with tidal creek networks adjacent to intertidal salt marsh habitat (for fish access) are key elements that need to be considered during the planning and implementation of coastal wetland restoration projects.

Influence of Motorboat Use on Thermal Refuges and Implications to Salmonid Physiology in the Lower Rogue River, Oregon

AbstractMotorboats can affect the behavior, physiology, and ecology of riverine fishes in several ways. One interaction that has been inadequately examined is the influence of motorboats and their wakes on thermal refuges and fishes using them. I used maps and thermal imagery to locate refuges, and continuous temperature monitors, behavioral observations, and bioenergetics models (including Q10) to quantify effects of motorboat use on salmonids in the lower Rogue River, Oregon. Motorboat wake height was inversely related to motorboat proximity; however, there was no clear relation between wake height and the intensity of temperature increases in thermal refuges. Eight of 10 boat passes were associated with slight increases in refuge temperatures (mean = 0.1°C; SD = 0.8; N = 10), although temperature differences before, during, and after boat activity were not significant (ANOVA: F = 0.41; df = 2, 18; P = 0.66). The presence of motorboats and their wakes did not appear to provoke startle responses in juvenile Chinook salmon Oncorhynchus tshawytscha when boats passed 3 m or farther from fish. Bioenergetics models showed negligible increases in salmonid daily standard metabolism or the chance of mortality from temperatures associated with boat wakes. These findings, albeit limited in scope, suggest that the current level of motorboat activity and its associated wakes have minor effects on the physiology of migrating salmonids using thermal refuges in the lower Rogue River.

Thermal maxima for juvenile shortnose sturgeon acclimated to different temperatures

Many populations of shortnose sturgeon, Acipenser brevirostrum, in the southeastern United States continue to suffer from poor juvenile recruitment. High summer water temperatures, which may be exacerbated by anthropogenic activities, are thought to affect recruitment by limiting available summer habitat. However, information regarding temperature thresholds of shortnose sturgeon is limited. In this study, the thermal maximum method and a heating rate of 0.1°C min−1 was used to determine critical and lethal thermal maxima for young-of-the-year (YOY) shortnose sturgeon acclimated to temperatures of 19.5 and 24.1°C. Fish used in the experiment were 0.6 to 35.0 g in weight and 64 to 140 days post hatch (dph) in age. Critical thermal maxima were 33.7°C (±0.3) and 35.1°C (±0.2) for fish acclimated to 19.5 and 24.1°C, respectively. Critical thermal maxima significantly increased with an increase in acclimation temperature (p < 0.0001). Lethal thermal maxima were 34.8°C (±0.1) and 36.1°C (±0.1) for fish acclimated to 19.5 and 24.1°C, respectively. Lethal thermal maxima were significantly affected by acclimation temperature, the log10 (fish weight), and the interaction between log10(fish weight) and acclimation temperature (p < 0.0001). Thermal maxima were used to estimate upper limits of safe temperature, thermal preferences, and optimal growth temperatures of YOY shortnose sturgeon. Upper limits of safe temperature were similar to previous temperature tolerance information and indicate that summer temperatures in southeastern rivers may be lethal to YOY shortnose sturgeon if suitable thermal refuge cannot be found.

Elevated body temperatures of adult female leopard sharks, Triakis semifasciata, while aggregating in shallow nearshore embayments: Evidence for behavioral thermoregulation?

The leopard shark, Triakis semifasciata, is an abundant nearshore elasmobranch, ranging from Baja California, Mexico to Oregon, USA. Mature female leopard sharks have been observed aggregating in shallow embayments throughout California; however, it is unclear why only females aggregate in these shallow areas. The goal of this study was to determine if mature female leopard sharks selectively occupy the warmest areas of a shallow embayment, if free-ranging leopard sharks' body temperatures are significantly warmer during the day than at night, and to quantify temporal use of these shallow habitats. Visual observations of sharks' fine-scale movements within the shallows of Big Fisherman's Cove Marine Life Refuge (Santa Catalina Island) aggregation site indicated that sharks preferred the warmest areas of the embayment and moved to warmer locations over the course of the day ( p < 0.05). Active and passive acoustic tracking, along with archival transponder technology (Vemco: V13, V13-R256, VX32TP-CHAT tags respectively) of 16 sharks caught and tagged within this aggregation were used to monitor core body temperature, swimming depth, and movements. Sharks had significantly higher core body temperatures in the late afternoon (1700 h–2000 h) during the summer, showed increased fidelity to thermal refuges during the day and increased movement away from these refuges at night ( χ 2, p < 0.05). Seasonal variations in warm, shallow water usage were also observed. Elevated core body temperature of mature female leopard sharks using warm shallow embayments will likely augment metabolic and physiological functions such as digestion, somatic growth, and possibly reproduction.

Erratum: Salmonid observations at a Klamath River thermal refuge under various hydrological and meteorological conditions

River Research and ApplicationsVolume 23, Issue 7 ErratumFree Access Erratum: Salmonid observations at a Klamath River thermal refuge under various hydrological and meteorological conditions Ronald J. Sutton, Corresponding Author Ronald J. Sutton rsutton@do.usbr.gov Bureau of Reclamation, Denver Office, PO Box 25007, Denver, CO 80225, USABureau of Reclamation, Denver Office, PO Box 25007, Denver, CO 80225, USA.Search for more papers by this authorMichael L. Deas, Michael L. Deas Watercourse Engineering, Inc., 424 Second Street, Suite B, Davis, CA 95616, USASearch for more papers by this authorStacy K. Tanaka, Stacy K. Tanaka Watercourse Engineering, Inc., 424 Second Street, Suite B, Davis, CA 95616, USASearch for more papers by this authorToz Soto, Toz Soto Karuk Tribe, PO Box 282, Orleans, CA 95556, USASearch for more papers by this authorR. Alex Corum, R. Alex Corum Karuk Tribe, PO Box 282, Orleans, CA 95556, USASearch for more papers by this author Ronald J. Sutton, Corresponding Author Ronald J. Sutton rsutton@do.usbr.gov Bureau of Reclamation, Denver Office, PO Box 25007, Denver, CO 80225, USABureau of Reclamation, Denver Office, PO Box 25007, Denver, CO 80225, USA.Search for more papers by this authorMichael L. Deas, Michael L. Deas Watercourse Engineering, Inc., 424 Second Street, Suite B, Davis, CA 95616, USASearch for more papers by this authorStacy K. Tanaka, Stacy K. Tanaka Watercourse Engineering, Inc., 424 Second Street, Suite B, Davis, CA 95616, USASearch for more papers by this authorToz Soto, Toz Soto Karuk Tribe, PO Box 282, Orleans, CA 95556, USASearch for more papers by this authorR. Alex Corum, R. Alex Corum Karuk Tribe, PO Box 282, Orleans, CA 95556, USASearch for more papers by this author First published: 09 August 2007 https://doi.org/10.1002/rra.1049AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume23, Issue7September 2007 RelatedInformation

Effects of climatic change and eutrophication on the glacial relict, Mysis relicta, in Lough Neagh

Summary1. The glacial relict, Mysis relicta, which occurs mainly in unproductive cold water habitats, shows increased mortality rates in temperatures above 16–18 °C. Using a 12‐year data set the growth, mortality and fat stores of Mysis in Lough Neagh, an increasingly hypertrophic lake which lacks a thermal refuge and which is subject to warming, were investigated.2. Mysis showed a significant reduction in fat stores on reaching sexual maturity, contrary to studies elsewhere.3. The contributions of temperature and eutrophication (total phosphorus, chlorophyll‐a concentrations) to growth, mortality and the timing and duration of developmental events were investigated by regression.4. Water temperatures rose between 1994 and 2005 and the time when temperatures exceeded 16 °C doubled over this period. Juvenile and adult growth rates declined and the duration of the juvenile stage increased in warmer years. Eutrophication also affected these variables but, in general, to a lesser extent than temperature.5. Year class strength (YCS) declined by a factor of 10 over the study period. YCS was independent of temperature up to 2000 °C degree days (&gt;4 °C) but declined steeply above that point. Temperature was more important than eutrophication in predicting mortality and YCS. YCS was positively correlated with the length of time water temperature was below 7 °C, the upper temperature for Mysis breeding.6. An established bioenergetic model predicted that water temperature and the timing of embryo release would have appreciable effects on Mysis viability. It also indicated that Mysis would lose mass at summer temperatures, consistent with the observed fat decline.

Salmonid observations at a Klamath River thermal refuge under various hydrological and meteorological conditions

AbstractThe Beaver Creek confluence with the main‐stem Klamath River was studied to assess salmonid use in a thermal mixing zone under various summer hydrological and meteorological conditions. Main‐stem flow releases from Iron Gate Dam ranged from 17 cms (615 cfs) to 37 cms (1320 cfs) during the study period and main‐stem water temperatures ranged from 19.5 to 26°C. A grid was constructed to define the thermal refuge as a system of cells. Temperatures were monitored using remote temperature loggers and fish counts were conducted using daytime snorkelling. Most juvenile salmonids were observed moving into the refuge when main‐stem temperatures exceeded 22–23°C. Salmonids in the thermal refuge did not necessarily seek the coolest water, but were generally located in habitats commensurate with species‐specific behavioural needs within their thermal tolerance range. Such ranges largely occurred within refuge areas. Variable meteorological conditions confounded observable biological thermal benefit to fish resulting from higher or lower main‐stem flows. Thermal regime dynamics indicated that under the hydrological and meteorological conditions observed, higher flows from Iron Gate Dam showed some ability to change the structure of the refuge area. It appeared that without the thermal refuge, main‐stem flows alone could not sustain the salmonid population because high water temperatures usually exceeded their published thermal tolerance limits. Copyright © 2007 John Wiley &amp; Sons, Ltd.