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Increasing Water Temperature (increasing + water_temperature)
Selected AbstractsUsing underwater cameras to describe the reproductive behaviour of the endangered eastern freshwater cod Maccullochella ikeiECOLOGY OF FRESHWATER FISH, Issue 3 2009G. L. Butler Abstract,,, Underwater cameras were used to observe the breeding behaviour of the endangered eastern freshwater cod, Maccullochella ikei, over 3 years and across three areas in the Mann and Nymboida rivers, Australia. The annual breeding season for M. ikei was short and succinct, lasting only 8,10 weeks. Spawning commenced each year in the lowest altitude area during the first week of spring, and approximately 1 week later in the closest upstream area. Day-length is the primary spawning cue for M. ikei, but increasing water temperature may also be of importance. Nesting sites were located in slow-flowing pools, under cover such as large boulders and bedrock shelves, at depths of 0.9,4.0 m, and with one or two entrances only. The nesting site was vigorously cleaned by the male up to 1 week prior to spawning and was only entered by the female for spawning. Paternal care of eggs and larvae was undertaken for up to 24 days, after which larvae dispersed. Greater protection of breeding M. ikei must be a management priority to ensure long-term conservation of the species. [source] Temperature dependence of stream benthic respiration in an Alpine river network under global warmingFRESHWATER BIOLOGY, Issue 10 2008V. ACUÑA Summary 1. Global warming has increased the mean surface temperature of the Earth by 0.6 °C in the past century, and temperature is probably to increase by an additional 3 °C by 2100. Water temperature has also increased, which in turn can affect metabolic rate in rivers. Such an increase in metabolic rate could alter the role of river networks in the global C cycle, because the fraction of allochthonous organic C that is respired may increase. 2. Laboratory-based incubations at increasing water temperature were used to estimate the temperature dependence of benthic respiration in streams. These experiments were performed on stones taken from seven reaches with different thermal conditions (mean temperature ranging 8,19 °C) within the pre-alpine Thur River network in Switzerland, June,October 2007. 3. The activation energy of respiration in different reaches along the river network (0.53 ± 0.12 eV, n = 94) was similar, indicating that respiration was constrained by the activation energy of the respiratory complex (E = 0.62 eV). Water temperature and the thickness of the benthic biofilm influence the temperature dependence of respiration and our results suggest that an increase of 2.5 °C will increase river respiration by an average of 20 ± 1.6%. [source] Synchrony in the downstream migration of smolts and upstream migration of adult Atlantic salmon in the subarctic River UtsjokiJOURNAL OF FISH BIOLOGY, Issue 6 2007P. Orell Seasonal and diel migration timing of wild Atlantic salmon Salmo salar smolts and adults were investigated annually (2001,2004) in the subarctic River Utsjoki, a tributary of the large River Teno (70° N), using underwater video monitoring. Submerged video cameras provided information on the exact timing and intensity of both migrations in a natural river channel, without disturbing the fish. In contrast to the mainly nocturnal migration pattern described from temperate rivers, the River Utsjoki smolts and adults migrated throughout the day. Smolts migrated most intensively during hours of rising (0300,0900 hours) and high sun (0900,1500 hours), while adults favoured the period of low sun (2100,0300 hours). Smolt migrations started in June and lasted on average 42 days. Adults usually ascended the site 2,3 weeks before the first descending smolts were observed and the adult migrations extended to the end of August. Seasonal synchrony was observed between smolt and adult migrations in years of slowly warming water, whereas in a year of exceptionally warm early summer (2002), smolts migrated earlier than adults. Thus, water temperature seemed to be an important environmental factor triggering the smolt migration, while the migration of adults was probably more fixed to a certain season. Weak positive correlations between fish counts and water temperature were observed, indicating that increasing water temperature may have promoted both smolt and adult migrations. The influence of discharge was negligible, although increasing discharge late in the season may have activated the remaining individuals in both groups. [source] Water temperature fluctuations and territoriality in the intertidal zone: two possible explanations for the elevational distribution of body size in Graus nigraJOURNAL OF FISH BIOLOGY, Issue 2 2002C. E. Hernández On the central coast of Chile, distribution of body size in Graus nigra varied with tidal pool height. With the objective of determining whether environmental temperature is one of the possible causes which explains the observed distribution pattern, two behavioural responses were analysed during an experimental period of increasing water temperature: number of opercular movements (an indirect measure of energy expenditure) and activity levels. The interactions of temperature × time and body size × time had a significant effect on the number of opercular movements. At low temperatures (13,15° C), large fish reached a maximum number of opercular movements, while small fish reached a maximum only at high temperatures (23,25° C). The interaction temperature × time had a significant effect on activity levels of different body sizes. In general, large fish appeared to be less active than small fish, however, at very high temperatures (24,26° C) all individuals increased their activity levels. These data indicate that small fish are acclimatized to live in a wider range of temperatures (13,23° C), and, for fish of all body sizes, the highest temperatures (23,26° C) probably constitute a suboptimal microhabitat. Strong territoriality was observed, with large individuals displacing smaller individuals. These data suggest that temperature is an important factor in explaining why large individuals are not present in high tidal pools (high temperatures), whereas territoriality explains why small individuals are not in low tidal pools (habitat of large individuals). [source] Effect of Feeding Frequency, Water Temperature, and Stocking Density on the Growth of Tiger Puffer, Takifugu rubripesJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 1 2006Kotaro Kikuchi Effects of daily feeding frequency, water temperature, and stocking density on the growth of tiger puffer, Takifugu rubripes, fry were examined to develop effective techniques to produce tiger puffer in a closed recirculation system. Fish of 4, 14, and 180 g in initial body weight were fed commercial pellet diets once to five times a day to apparent satiation each by hand for 8 or 12 wk at 20 C. Daily feeding frequency did not affect the growth of 14- and 180-g-size fish. However, the daily feed consumption and weight gain of the 4-g-size fish fed three and five times daily were significantly higher than those of fish fed once daily (P < 0.05). Fish of 4 and 50 g in initial body weight were reared with the pellet diet at 15,30 C for 8 wk. The weight gain of fish increased with increasing water temperature up to 25 C and decreased drastically at 30 C for both sizes. Similar trends were observed for feed efficiency, although 4-g fish had highest efficiency at 20 C. Effects of stocking density on growth were examined with fish of 8, 13, and 100 g in initial body weight. Fish were reared with the pellet diet for 8 or 16 wk at 20 C. Fish were placed in floating net cages in the culture tank, and the stocking density was determined based on the total weight of fish and volume of the net cage. Fish of 8 g in body weight grew up to 35,36 g during the 8-wk rearing period independent of the stocking density of 8, 15, and 31 kg/m3 at the end of rearing. Final biomass per cage reached 32, 60, and 115 kg/m3 for 13-g-size fish, and 10, 18, and 35 kg/m3 for 100-g-size fish, and the growth of the fish tended to decrease with increasing stocking density for both sizes. [source] Batch solvent extraction of flavanolignans from milk thistle (Silybum marianum L. Gaertner)PHYTOCHEMICAL ANALYSIS, Issue 1 2005Sunny N. Wallace Abstract Seeds of milk thistle (Silybum marianum L. Gaertner) contain silymarins and ca. 25% (w/w) of oil. A pre-treatment step involving re,uxing with petroleum ether is usually performed before extraction of the silymarins using organic solvents. This paper compares the extraction of whole and defatted milk thistle seeds in various solvents as a function of temperature. The extraction of whole seeds of milk thistle with water at 50, 70 and 85°C was also examined: the yield of silymarin increased with increasing water temperature. In most cases, ethanol at 60°C recovered the largest quantities of silymarins. However, boiling water proved to be an ef,cient extraction solvent for the more polar silymarins such as taxifolin and silychristin, even when using whole seeds. Extractions of defatted seed meal with boiling ethanol returned maximum yields of 0.62, 3.89, 4.04, and 6.86 mg/g defatted seed of taxifolin, silychristin, silybinin A and silybinin B, respectively. When extracting defatted seed meal with ethanol, yields of taxifolin, silybinin A and silybinin B were, respectively, 6.8-, 0.95-, 1.7- and 1.6-fold higher than when extracting whole seeds. When extracting with boiling water, the yields of silychristin, silybinin A, and silybinin B were 380, 47 and 50% higher for whole seeds compared with defatted seeds. Copyright © 2005 John Wiley & Sons, Ltd. [source] | |||||||||||||