Growth, pigmentation and activity of juvenile Japanese eels in relation to temperature and fish size

The growth and activity of juvenile Japanese eels Anguilla japonica in different pigmentation stages from the glass eel to the elver stage were studied in the laboratory at 15, 20 and 25° C. The growth and activity of the eels were significantly influenced by both temperature and fish size. Growth rate generally declined with increasing fish size, and fish were least active and experienced a low growth during the pigmenting stage at all temperatures. They were nocturnal and spent significantly more time moving (swimming, feeding and moving over the substratum) at 20 and 25° C than at 15° C at night within each pigmentation stage. Accordingly, they grew significantly faster at 20 and 25° C than at 15° C throughout the study. The development of pigmentation appeared to be dependant on water temperature but not on fish size. This study suggested that the growth and activity of juvenile Japanese eels were positively correlated, because fish were least active and grew slowest at low temperature (15° C) or during the pigmenting stage at all temperatures.     

Diel activity patterns of South Scandinavian high mountain ground beetles (Coleoptera, Carabidae)

Fourteen species of carabids were studied throughout the snowfree season in outdoor arenas above the timberline at Finse, South Norway (60°36'N, 7°30'E). Ten species were nocturnal. Onset of nocturnal activity occurred after termination of twilight with peak activity before midnight, but in June, with less than 1 h of darkness, activity was extended into evening twilight, the peak being around midnight. Linear regressions between ground surface temperature and nocturnal activity predicted zero activity in the range −2.0 to0.8°C, mean −0.5°C, indicating that activity is possible on most nights throughout the snowfree season. Two diurnal species had activity threshold temperatures at 4 and 8°C, respectively, the former with a peak at 16°C and an upper threshold at 28°C.
The proportion of nocturnal species in the study area was significantly greater than in lowland open fields. Large and common species were mainly nocturnal, while small and rare species were mainly diurnal. It is suggested that nocturnalism in the South Scandinavian high mountains is a response to avoid bird predation and desiccation.     

The effect of temperature on the activity of three species of Helicid snail (Mollusca: Gastropoda)

The activity of the land snails Cepaea nemoralis (L.), C. hortensis (Müll.) and Arianta arbustorum (L.) was measured over 24 hours at the constant temperatures of 0, 3, 8, 17, 22 and 26°C at 100% relative humidity and with 16 hours light and 8 hours dark. The activity of all three species varies significantly with temperature and light, and there are differences in the activities of the species at each temperature. A. arbustorum is relatively more active than Cepaea at low rather than high temperatures, as is C. hortensis with respect to C. nemoralis , though to a lesser extent. There is little diurnal rhythm in activity at 0°C, but all species become more nocturnal as temperature increases; C. nemoralis is most, and A. arbustorum least nocturnal. The results obtained assist in explaining the observed geographical and local distributions of the species concerned.     

The importance of habitat temperatures for growth in the tropical cichlid Tilapia rendalli Boulenger

Like many cichlids living in shallow tropical freshwater systems of Africa, Tilapia rendalli exhibit a marked daily movement into warm shallow water during the day and return to cooler, deeper water at night. Such movements have an important impact on the growth of juvenile fish. Growth is enhanced by this movement and is predicted to be optimal if the fish occupy water with a temperature of 30°C during the day but retire to nocturnal habitats with temperatures of 18°C. The reasons for this phenomenon are discussed using a bio-energetic model incorporating measurements of feeding intensity, metabolic energy demands and assimilation efficiencies at temperatures ranging from 18°C—3°C and the ecological implications discussed using examples from natural systems.     

Thermoregulatory behaviour, diel activity and the relationship of spontaneous locomotor activity to temperature in the sea raven, Hemitripterus americanus (Gmelin)

Twelve sea ravens, Hemitripterus americanus , were tested individually for three day periods in electronic shuttleboxes to measure their preferred and avoided temperatures, diel activity pattern and relationship of activity to temperature. The fish avoided temperatures below 9°C or above 25°C, preferring temperatures with a central tendency of 15–17°C. The fish were primarily nocturnal, being more active at night than by day. Locomotor activity increased eightfold between 10 and 20°C, but exhibited an anomalous decrease between 14 and 18°C, corresponding to the preferred-temperature zone, characteristic of maximal summer temperatures in the natural habitat.     

Assessment of cardiac output as a predictor of metabolic rate in rainbow trout

When water temperature was increased from 12 to 27°C at a rate of 2°C h⁻¹, oxygen consumption of rainbow trout Oncorhynchus mykiss was correlated strongly with both heart rate and blood oxygen extraction but the relationship with cardiac output was variable and weak. On the other hand, when water temperature was decreased from 21 to 12°C at a rate of 0·5°C h⁻¹, oxygen consumption was correlated with both heart rate and cardiac output but not with blood oxygen extraction. When fish were forced to swim increasingly faster, heart rate, cardiac output and blood oxygen extraction all correlated positively with oxygen consumption. For both cardiac output and heart rate, the slope of the regression line with oxygen consumption was elevated significantly more when the fish were forced to swim at increasingly higher swimming speeds than when water temperature was increased or decreased. The variation of the regression lines between cardiac output and oxygen consumption indicated that cardiac output presents few advantages over heart rate as a predictor of metabolic rate.     

Laboratory studies on food intake, growth and food conversion of young herring, Clupea harengus (L.)

Food intake, growth and food conversion of young, O-group herring were studied at two temperatures and feeding regimes over a period of 19 weeks. The food intake of fish fed to satiation twice daily showed considerable variation. Food intake per fish at 14.5° C was about three times that at 6.5° C, and was generally much higher than in most other species of fish studied. The mean increase in wet weight over the 19-week period was 0.581 g/week at 14.5° C and 0.236 g/week at 6.5° C in fish fed to satiation and 0.094 g/week at 6.2° C and a ration of 1.3% of the body weight. Growth depensation was found to occur even in fish fed to satiation. The changes in specific growth rate, that is the percentage increase in weight/day, showed similar trends at different temperatures and food regimes. The mean conversion efficiency of fish on a ration of 1.3% at 6.2° C was higher than that of fish fed until satiation, at 14.5 and 6.5° C. The conversion efficiency of fish fed to satiation at 14.5° C showed a distinct decrease with increasing weight while at 6.5° C such a clear trend was not observed. In general, the conversion efficiency of young herring were found to be much lower than that of most other species studied. The weight exponent of the quantitative relationship between food intake and body weight at 14.5° C was 0.744. The total metabolic expenditure at 14.5° C, calculated using Winberg's (1956) 'utilization coefficient, gave a weight exponent of 0.773.     

Isolation of a Pseudomonas species from fish intestine that produces a protease active at low temperature

A psychrotrophic bacterium producing a protease active at low temperatures was isolated from fish intestine and identified as a Pseudomonas species. Optimum growth and protease-producing temperatures of this strain were 15°C and 10°C, respectively. The maximum temperature for proteolytic activity was 25°C, an unusually low temperature.     

Temperature effects on metabolic rate, swimming performance and condition of Pacific cod Gadus macrocephalus Tilesius

Critical swimming speed ( U _crit) and rate of oxygen consumption of Pacific cod Gadus macrocephalus acclimated to 4 and 11° C were determined to assess the influence of water temperature on performance. The physiological effect of exercise trials on fish held at two temperatures was also assessed by comparing haematocrit and plasma concentrations of cortisol, metabolites and ions collected from fish before and after testing. The U _crit of fish acclimated and exercised at 4° C did not differ from those acclimated and exercised at 11° C [1·07 body lengths (total length) s⁻¹]. While the standard metabolic rate of 11° C acclimated fish was 28% higher than that of 4° C fish, no significant difference was observed between fish acclimated at the two temperatures. Plasma concentrations of cortisol, glucose and lactate increased significantly from pre- to post-swim in both groups, yet only concentrations of cortisol differed significantly between temperature treatments. Higher concentrations of cortisol in association with greater osmoregulatory disturbance in animals acclimated at the lower temperature indicate that the lower water temperature acted as an environmental stressor. Lack of significant differences in U _crit between temperature treatments, however, suggests that Pacific cod have robust physiological resilience with respect to swimming performance within temperature changes from 4 to 11° C.     

Water temperature fluctuations and territoriality in the intertidal zone: two possible explanations for the elevational distribution of body size in Graus nigra

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).     

Laboratory studies on the effects of thermal change on the behaviour and distribution of juvenile chum salmon in sea water

Schooling chum salmon Oncorhynchus keta were biased towards the water surface (median position <1 m) under isothermal conditions (10° C) in a water column simulator (WCS). Thermal stratification (24/10° C) inhibited upward movement with fish congregating at the thermocline and displaying a clear avoidance of potentially lethal surface waters. A tri-phase model based on piece-wise nonlinear regression was used to describe the distribution shifts of chum salmon during a change from isothermal to thermally stratified conditions. Fish distribution was consistent with thermoregulatory behaviour and exhibited 'attraction', 'preference' and 'avoidance' phases. The thermal preference of 50% of the fish lay between 12·2 and 20·2° C, however, >83·5% of the fish occupied a 'preferred' temperature range of 13·7–17·9° C. The mean temperature at which 50% of chum salmon avoided rising temperature by shifting deeper in the water column and using the cooler thermocline was 20·2° C, and 90% avoidance occurred at 22·9° C. Behavioural responses to thermal stratification were consistent amongst underyearling fish of differing size and age.     

Effects of temperature on the growth and survival of the European eel, Anguilla anguilla L.

Experiments to determine the growth rate of eels ( Anguilla anguilla L.) at different temperatures are described and show the optimum temperature for growth to be 22–23° C. The ultimate upper lethal temperature was found to be 38° C and the critical thermal maximum varied from 33 to 39° C for fish acclimated at 14 to 29° C. An attempt was also made to determine lower lethal temperatures. Eels enter a state of torpor at temperatures varying from 3° C for fish acclimated at 29° C to less than 1° C for fish acclimated at 23° C or below. The results have been used to estimate the growth rates expected from eels cultured in power station cooling water using different types of temperature control.     

Behavioural thermoregulation and homing by spring chinook salmon, Oncorhynchus tshawytscha (Walbaum), in the Yakima River

Temperature-sensitive radio transmitters were employed to study the patterns of behavioural thermoregulation, habitat preference and movement of 19 adult spring chinook salmon, Oncurhynchus tshawytscha (Walbaum), in the Yakima River. During the 4 months prior to spawning, fish maintained an average internal temperature 2.5°C below ambient river temperature. This represented a 12 to 20% decrease in basal metabolic demand or a saving of 17.3 to 29.9 calkg⁻¹ h⁻¹. Fish were most commonly associated with islands, pools, and rock out-croppings along stream banks. Homing behaviour appeared to be modified to optimize temperature regimes and energy conservation. As the time of spawning approached, fish left thermal refuges and migrated to spawning grounds upstream and downstream of refuge areas. Although spring chinook salmon residing within cool-water refuges may be capable of mitigating sub-lethal temperature effects, cool-water areas need to be abundant and available to the fish. The availability of suitable thermal refuges and appropriate holding habitat within mainstem rivers may affect long-term population survival.     

The stress and metabolic responses of juvenile Atlantic cod Gadus morhua L. to an acute thermal challenge

Survival, oxygen consumption (     ), total plasma cortisol and glucose levels and gill heat-shock protein 70 (hsp70) expression were measured in 10 and 50 g juvenile Atlantic cod Gadus morhua during an acute temperature increase (2° C h⁻¹) to their critical thermal maximum. Ninety three per cent of the fish in both size classes survived to 24° C; however, mortality was 100% within 15 min of reaching this temperature. The     for both size classes increased significantly with temperature, reaching peak values at 22° C that were c. 2·8-fold those of control (10° C) fish. Resting plasma cortisol and glucose levels were lower in 10 g as compared to 50 g fish. Plasma glucose levels were highly variable in both size classes, and significant increases were only seen at >22° C for the 10 g fish. In contrast, plasma cortisol showed an exponential increase with temperature starting at 16° C in both size classes, and reached maximum levels at 22° C that were 19-fold (10 g fish) and 35-fold (50 g fish) higher than their respective control groups. Both the constitutive (73 kDa) and inducible (72 kDa) isoforms of hsp70 were detected in both size classes using the widely utilized mouse monoclonal antibody. Expression of these isoforms, however, did not change when Atlantic cod were exposed to elevated temperature, and the 72 kDa isoform was not detected using salmonid-specific antibodies. These results indicate that juvenile Atlantic cod are very sensitive to acute increases in water temperature. In addition, they (1) show that     and plasma cortisol, but not plasma glucose or gill hsp 70 levels, are sensitive indicators of thermal stress in Atlantic cod and (2) support previous reports that the upper critical temperature for this species is 16° C.     

Shifts in the optimal temperature for nocturnal CO2 uptake caused by changes in growth temperature for cacti and agaves

When the day/night air temperatures were raised from 10°C/10°C to 30°C/30°C, the optimal tempearture for nocturnal CO² uptake by six species of cacti and three species of agave shifted from an average of 12°C to an average of 20°C. The maximum rate of CO² uptake was higher for Agave americana at the higher ambient temperature, lower for A. deserti , and much lower for A. utahensis , consistent with the relative mean temperatures of their native habitats. For the cactus Coryphantha vivipara , which had the greatest temperature shift observed (13°C), the halftime was 8 days for the upward shift and 4 days for the downward shift. The halftimes for the comparable shifts averaged 1.6 days for three other species of cacti and less than 1 day for two agave species. The shifts in the optimal temperature for nocturnal CO² uptake were in response to changes in nighttime temperature, at least for C. vivipara , and reflected temperature responses of both the stomates and the chlorenchyma.     

The feeding, growth and behaviour of juvenile cod, Gadus morhua L., in cold environments

Most studies on feeding-related activities of fish in cold water (0° C) have not used eurythermal species or examined a broad suite of activities. In this study we report on the feeding, growth, behaviour and conversion-efficiency of 0 + Atlantic cod in response to water temperature and food availability. In one experiment, activity, opercular beat and growth decreased with decreasing temperature over the range 8·3–0·6° C. However, the conversion efficiency increased with decreasing temperature, a result partly explained by the relative change in activity and opercular rate. In another experiment, temperature had a linear effect on growth in cod fed different food rations. Both food availability and temperature were found to influence growth in group 0 + cod. The specific growth rate of cod in this experiment exceeded 2% day^-1. Growth data collected from cod sampled in the field during the cold-water period showed a progressive increase of mean length over the season. Overall, these results demonstrate that 0 + cod have adapted to life in cold-water environments, in contrast to adult cod which mostly inhabit warmer environments.     

A radiographic estimation of the effect of temperature on gastric emptying time in Sarotherodon niloticus (L) × S. aureus (Steindachner) hybrids

A radiographic technique was used to determine temperature effects on gastric emptying time in S. niloticus/aureus hybrids. Stomach evacuation times for 30 g fish fed 3% of their body weight were 8.5 h at 30° C, 10.8 h at 25° C and 16.4 h at 20° C. Hence, there was a negative correlation between stomach evacuation time and temperature. The Q ₁₀ between 20 and 30° C was calculated to be 1.92. Similar relationships were found for intestinal evacuation and total evacuation.
The data were used to estimate maximum daily feed intake levels of fish within the size range studied. Levels for 30 g fish were 8.5% body weight at 30° C, 6.6% at 25° C and 4.4% at 20° C. However, the optimum feeding regime should take account of the feeding behaviour of the animals.     

Behavioural studies on the lesser sandeel Ammodytes marinus (Raitt) III. The effect of temperature on activity and the environmental control of the annual cycle of activity

The behaviour of the lesser sandeel, Ammodytes marinus (Raitt), has been investigated at 5, 10 and 15° C, using a photographic method of recording activity. The activity patterns at 10 and 15° C were very similar, there being a high level of swimming activity during the light period, which fell to a low level at 5° C. It was also lower at 10° C at the end of the experiment than at the beginning and it is suggested that this might have been due to an increase in the fat contents of the fish. The feeding rate of the fish was measured and showed a Q ₁₀ of 2.08 for the temperature range 5–15° C. The annual cycle of activity of A. marinus is discussed in relation to seasonal changes in food availability, light and temperature, and in the fat content of the fish. It is concluded that after spawning in the December–January period the fish remain buried in the sand until April, because of the limiting effect on swimming and feeding activity of the environmental factors in the intervening period. The proportion of fish available for capture at the start of the fishery in April is related mainly to temperature, but food (as measured by numbers of copepods) light intensity and photoperiod are by then increasing rapidly. After July the fishery ceases and it is thought that this is because the fish have entered an overwintering stage, during which they remain buried in the sand. This phase is also thought to be associated with the maturation of the gonads in readiness for the winter spawning. The factors causing the fish to enter this stage are as yet undetermined but may be related to the attainment of a certain level of fat content.     

Toxicity of rotenone to some species of coarse fish and invertebrates

The toxicity of rotenone was determined for seven species of fish and three species of invertebrates. The results show that there is a marked variation in sensitivity of different species to rotenone. The survival times of roach Rutilus rutilus (L.) were reduced by a rise in temperature and also by a reduction in water hardness. Temperature affected the rate at which rotenone is degraded; 3 days after being prepared a solution containing 2 mg/1 of 5 % rotenone was non-toxic to roach over a 7-day period at 20°C, but it was still toxic for at least 11 days at 11.5°C. The data are discussed in relation to the use of rotenone in fisheries management.     

The influence of temperature on growth and proximate body composition of under yearling Lake Inari arctic char (Salvelinus alpinus (L.))

The growth of underyearling Lake Inari arctic char was studied in groups of fish held at 5.9, 8.7, 12.1, 15.1 and 18.0 °C for 31 days. Growth rate increased with increasing water temperature, reached a peak at 15.1 °C, and then declined. The temperature influence on relative growth was expressed as a non-linear function.
There were differences in body composition between fish reared at different temperatures: percentage water being highest at the lowest temperature, whereas energy content was highest in the fish held at the three highest temperatures. The body wet weight explained most of the variance in water content and it is suggested that this may also apply to other body constituents.