Metabolic rates of juvenile scalloped hammerhead sharks (Sphyrna lewini)

Oxygen consumption of juvenile scalloped hammerhead sharks, Sphyrna lewini, was measured in a Brett-type flume (volume=635 l) to quantify metabolic rates over a range of aerobic swimming speeds and water temperatures. Oxygen consumption (log transformed) increased at a linear rate with increases in tailbeat frequency and swimming speed. Estimates of standard metabolic rate ranged between 161 mg O₂ kg^-1 h^-1 at 21°C and 203 mg O₂ kg^-1 h^-1 at 29°C (mean-SD: 189ᆣ mg O₂ kg^-1 h^-1 at 26°C). Total metabolic rates ranged from 275 mg O₂ kg^-1 h^-1 at swimming speeds of 0.5 body lengths per second (L s^-1) to a maximum aerobic metabolic rate of 501 mg O₂ kg^-1 h^-1 at 1.4 L s^-1. Net cost of transport was highest at slower swimming speeds (0.5-0.6 L s^-1) and was lowest between 0.75 and 0.9 L s^-1. Therefore, these sharks are most energy efficient at swimming speeds between 0.75 and 0.9 L s^-1. These data indicate that tailbeat frequency and swimming speed can be used as predictors of metabolic rate of free-swimming juvenile hammerhead sharks.     

Aerobic metabolic rates of swimming juvenile mako sharks, <Emphasis Type="Italic">Isurus oxyrinchus</Emphasis>

The shortfin mako shark, Isurus oxyrinchus, is a highly streamlined epipelagic predator that has several anatomical and physiological specializations hypothesized to increase aerobic swimming performance. A large swim-tunnel respirometer was used to measure oxygen consumption (MO₂) in juvenile mako sharks (swimming under controlled temperature and flow conditions) to test the hypothesis that the mako shark has an elevated maintenance metabolism when compared to other sharks of similar size swimming at the same water temperature. Specimen collections were conducted off the coast of southern California, USA (32.94°N and 117.37°W) in 2001-2002 at sea-surface temperatures of 16.0–21.0°C. Swimming MO₂ and tail beat frequency (TBF) were measured for nine mako sharks [77–107 cm in total length (TL) and 4.4 to 9.5 kg body mass] at speeds from 28 to 54 cm s⁻¹ (0.27–0.65 TL s⁻¹) and water temperatures of 16.5–19.5°C. Standard metabolic rate (SMR) was estimated from the extrapolation to 0-velocity of the linear regression through the LogMO₂ and swimming speed data. The estimated LogSMR (±SE) for the pooled data was 2.0937 ± 0.058 or 124 mg O₂ kg⁻¹ h⁻¹. The routine metabolic rate (RMR) calculated from seventeen MO₂ measurements from all specimens, at all test speeds was (mean ± SE) 344 ± 22 mg O₂ kg⁻¹h⁻¹ at 0.44 ± 0.03 TL s⁻¹. The maximum metabolic rate (MMR) measured for any one shark in this study was 541 mg O₂ kg⁻¹h⁻¹ at 54 cm s⁻¹ (0.65 TL s⁻¹). The mean (±SE) TBF for 39 observations of steady swimming at all test speeds was 1.00 ± 0.01 Hz, which agrees with field observations of 1.03 ± 0.03 Hz in four undisturbed free-swimming mako sharks observed during the same time period. These findings suggest that the estimate of SMR for juvenile makos is comparable to that recorded for other similar-sized, ram-ventilating shark species (when corrected for differences in experimental temperature). However, the mako RMR and MMR are apparently among the highest measured for any shark species.     

Relationship of oxygen consumption to swimming speed in Euphausia pacifica

Swimming efficiency (the ratio of thrust power required to overcome hydrodynamic drag to net metabolic energy expenditure) was calculated for the vertically migrating euphausiid Euphausia pacifica swimming at speeds of 1–20 cm s^–1 and at temperatures of 8° and 12°C. Efficiencies ranged from 0.014 to 2.8% at 8°C and 0.009 to 1.69% at 12°C. A comparison with efficiency in fishes 2–3 orders of magnitude larger in weight (efficiency range 10–25%) indicates that locomotion in E. pacifica is far less efficient, a probable result of the organism's small size (x=33.5 mg WW) and multiple-paddle mode of propulsion. Net cost of transport of E. pacifica is three to six times the cost of a hypothetical value for sockeye salmon. Low swimming efficiencies in zooplankton such as E. pacifica are responsible for the underestimation of zooplankton swimming costs. Multiple-paddle propulsion is less efficient than the undulatory mode of fishes.     

Energetics of underwater swimming in the great cormorant (Phalacrocorax carbo sinensis)

Resting metabolic rate (RMR), energy requirements and body core temperature were measured during underwater swimming in great cormorants (Phalacrocorax carbo sinensis) at the zoological garden in Neumünster, Germany, using gas respirometry and stomach temperature loggers. We used a 13 m long still water canal equipped with a respiration chamber at each end. Birds swam voluntarily in the canal at a mean speed of 1.51 ms^-1. Power input during underwater swimming averaged 31.4 W kg^-1. Minimal costs of transport of 19.1 J kg^-1 m^-1 were observed at a speed of 1.92 m s^-1. Body core temperature was stable in all birds within the first 60 min spent in the canal. After that, body temperature dropped at a rate of 0.14°C min^-1 until the birds voluntarily left the water. Our data indicate that great cormorants spend 2.7 times more energy than Adélie penguins (Pygoscelis adeliae) during underwater swimming. This can be essentially attributed to their poor insulation, their mode of locomotion underwater and differences in streamlining. RMR on land was related to body mass via VO₂=0.691 M^0.755 (where VO₂ is O₂-consumption in litre h^-1 and M is body mass in kg). In order to quantify the effects of external devices on energy consumption during underwater swimming, we tested a dummy data logger attached to the back of the cormorants as well as a ring on the leg. The ring had no apparent influence on the swimming energetics of the cormorants. In birds equipped with dummy loggers, swimming speed was not significantly influenced, but both power input and costs of transport increased by a mean of 19% for swimming speeds between 1.4 and 1.8 m s^-1.     

The effect of acute hypoxia on swimming stamina at optimal swimming speed in flathead grey mullet <Emphasis Type="Italic">Mugil cephalus</Emphasis>

Flathead grey mullets Mugil cephalus are commonly found in Mediterranean lagoons, which are regularly subject to high environmental variations. Oxygen is one of the factors that shows extremely high variation. The objective of this study was to test the effects of acute hypoxia exposure at two experimental temperatures (i.e. 20 and 30°C) on the stamina (time to fatigue) in M. cephalus swimming at the minimal cost of transport (i.e. optimal swimming speed; U _opt). At each temperature, a relationship was established between swimming speed and oxygen consumption (MO₂). This allowed estimation of U _opt at 45 cm s⁻¹ (~1.12 Body Length s⁻¹). Independent of temperature, stamina at U _opt was significantly reduced in severe hypoxia, i.e. at 15% of air saturation (AS). In these conditions, oxygen supply appears therefore to be insufficient to maintain swimming, even at the low speed tested here. After the stamina test, MO₂ measured in fish tested at 15% AS was significantly higher than that measured after the test in normoxia. Therefore, we suggest that in hypoxia, fish used anaerobic metabolism to supplement swimming at U _opt, leading to an oxygen debt. Since flathead grey mullet is a hypoxia-tolerant species, it is possible that hypoxic conditions less severe than those tested here may reduce stamina at low speed in less tolerant species. In addition, we suggest that testing stamina at these speeds may be relevant in order to understand the effect of hypoxia on behavioural activities carried out at low speed, such as food searching.     

Oxygen consumption of pelagic juveniles and demersal adults of the deep-sea fish Sebastolobus altivelis,measured at depth

Oxygen consumption rates of the deep-sea fish Sebastolobus altivelis were measured in situ on pelagic juveniles at mesopelagic depths (608 m) and on demersal adults at bathyal depths (1 300 m) in the Santa Catalina Basin in March 1982. Two pelagic juveniles were individually collected, and respiration was measured continuously for approximately 2 d with a slurp gun respirometer manipulated from the submersible “Alvin”. Oxygen consumption rates of these juveniles were highly variable and were 1.5 to 1.8 times higher during the night than during the day. Gut contents of the juveniles were mainly euphausiids (Euphausia pacifica and Nematoscelis difficilis). Four demersal adults were collected by “Alvin” and individually placed in fish-trap respirometers on the bottom where respiration was measured continuously for approximately 1 d. Weight-specific O₂ consumption rates for adults decreased with increasing body weight and were consistent in magnitude throughout the incubation period. Population O₂ consumption for demersal S. altivelis (calculated from abundance, size-frequency distribution, and O₂ consumption regression equation) was 11.01 μl O₂ m^-2 h^-1, which is two orders of magnitude less than the O₂ consumption rate for the population of the most abundant epibenthic megafaunal species in the Santa Catalina Basin, the ophiuroid Ophiophthalmus normani. O. normani is a principal prey for adults of S. altivelis based on gutcontent analysis. Given the population O₂ consumption rate as an estimate of food energy demand, the demersal population of S. altivelis would assimilate only 0.007% of the standing crop of O. normani per day.     

Metabolic properties of Northern krill, Meganyctiphanes norvegica, from different climatic zones. I. Respiration and excretion

Adaptive processes linked to overall metabolism were studied in terms of oxygen consumption and ammonia excretion in each of three self-contained krill populations along a climatic gradient. In the Danish Kattegat, krill were exposed to temperatures which ranged from 4°C to 16°C between seasons and a vertical temperature gradient of up to 10°C during summer. In the Scottish Clyde Sea, water temperatures varied less between seasons and the vertical temperature gradient in summer was only 3°C. Temperatures in the Ligurian Sea, off Nice, were relatively constant around 12-13°C throughout the year, with a thin surface layer (20-30 m) of warm water developing during summer. The trophic conditions were rich in the Kattegat and, particularly, in the Clyde, but comparatively poor in the Ligurian Sea. Oxygen consumption increased exponentially with increasing experimental temperature, which ranged from 4°C to 16°C. Overall respiration rates were between 19.9 and 89.9 µmol O₂ g^-1 dry wt h^-1. Krill from the Kattegat, the Clyde Sea, and the Ligurian Sea all exhibited approximately the same level of oxygen consumption (30-35 µmol O₂ g^-1 dry wt h^-1) when incubated at the ambient temperatures found in their respective environments (9°C, 5°C, and 12°C). This indicates that krill adjust their overall metabolic rates to the prevailing thermal conditions. The exception to this were the respiration rates of Ligurian krill from winter/spring, which were about twice as high as the rates from summer krill despite the fact that the thermal conditions were the same. This effect appears to result from enhanced somatic activity during a short period of increased food availability and reproduction. Accordingly, krill appears to be capable of adapting to both changing thermal and trophic conditions, especially when nutrition is a limiting factor in physiological processes.     

Temperature effects on the metabolism of larvae of the Antarctic starfish Odontaster validus, using a novel micro-respirometry method

Oxygen consumption of individual larvae of the Antarctic sea-star Odontaster validus was measured during the 50-day period following fertilisation. Values ranged from 0.76 pmol O₂ h^-1 for one specimen at the coeloblastula stage to 77.6 pmol O₂ h^-1 for one bipinnaria larva. At 0°C the mean oxygen consumption rate of an individual larva increased from 10.9 pmol O₂ h^-1 (standard error of the mean, SEM, 0.13) for a gastrula larva, 13 days post-fertilisation, to 25.4 pmol O₂ h^-1 (SEM 3.5) at the bipinnaria stage (50 days post-fertilisation). Gastrulae reared at -0.5°C did not have significantly different oxygen consumption rates between days 13 and 45 post-fertilisation (mean=11.4 pmol O₂ h^-1). Individual metabolic rates were highly variable, covering more than a 40-fold range. At 2°C gastrula oxygen consumption was on average 45% higher (17.35 pmol O₂ h^-1), giving a Q₁₀ temperature effect of 4.4. For bipinnaria, mean oxygen consumption in 2°C larvae (31.4 pmol O₂ h^-1) was not significantly different from that in larvae at -0.5°C, suggesting bipinnaria metabolism may be less sensitive to temperature change than earlier stages. At 2°C the bipinnaria stage was reached at 30-35 days compared with 45-50 days at 0°C, giving a Q₁₀ of 4.5 for temperature effects on development. The method here used a new, highly sensitive micro-respirometry method that is inexpensive and straightforward in design. Individual larvae of O. validus were held in 35- to 50-µl respirometers. These larvae have very low metabolic rates, and published work on such organisms have utilised at least 25 individuals per chamber. The oxygen content of the respirometers was measured using a 25-µl sample injected into a couloximeter. Oxygen consumption rates down to -1 pmol h^-1 can be detected. Under optimum conditions oxygen consumption of a single larva of -4 pmol O₂ h^-1 was measured with an accuracy of ᆨ%. Values of ~15 pmol h^-1 could routinely be measured with this accuracy. This method would allow oxygen consumption to be evaluated in individual field-caught larvae of most marine ectotherms.     

ATP content and adenylate energy charge of the mussel Mytilus edulis during the annual reproductive cycle in Lindåspollene,Western Norway

The oxygen consumption rates ( VO₂) of 6 specimens (6 to 13 kg) of the albacore tuna Thunnus alalunga were measured at sea, using specimens collected 300 km west of San Diego, California (USA) during July and August, 1981. Fish were tested in a closed continuous-flow respirometer, where they swam at about 1.3 body lengths s^-1 velocity in 15° to 19°C water. The albacore tuna is a temperate pelagic species experiencing water temperatures from about 10° to 20°C and attaining a maximum weight of 45 kg. The VO₂ ranged from 1 249 to 3 336 ml h^-1 (the mean VO₂ for the 6 fish was 2 228 ml h^-1); such values approach those of mammals of a similar size and are 3 to 4 times those of most active fishes (e.g. sockeye salmon). Among fishes, the only higher VO₂ values yet recorded were for the skipjack tuna Katsuwonus pelamis, a tropical species. The remarkably high metabolic rates of tunas are presumably correlated with their continuous swimming activity and the maintenance of endothermy. The exponent relating VO₂ to body weight (1.18), although large, is not statistically different from the exponents for most other active vertebrates.     

Environmental preferences of yellowfin tuna (Thunnus albacares) at the northern extent of its range

We used acoustic telemetry to examine the small-scale movement patterns of yellowfin tuna (Thunnus albacares) in the California Bight at the northern extent of their range. Oceanographic profiles of temperature, oxygen, currents and fluorometry were used to determine the relationship between movements and environmental features. Three yellowfin tuna (8 to 16 kg) were tracked for 2 to 3 d. All three fish spent the majority of their time above the thermocline (18 to 45 m in depth) in water temperatures >17.5 °C. In the California Bight, yellowfin tuna have a limited vertical distribution due to the restriction imposed by temperature. The three fish made periodic short dives below the thermocline (60 to 80 m), encountering cooler temperatures (>11 °C). When swimming in northern latitudes, the depth of the mixed layer largely defines the spatial distribution of yellowfin tuna within the water column. Yellowfin prefer to spend most of their time just above the top of the thermocline. Oxygen profiles indicated that the tunas encountered oceanic water masses that ranged most often from 6.8 to 8.6 mg O₂ l⁻¹, indicating no limitation due to oxygen concentrations. The yellowfin tuna traveled at speeds ranging from 0.46 to 0.90 m s⁻¹ (0.9 to 1.8 knots h⁻¹) and frequently exhibited an oscillatory diving pattern previously suggested to be a possible strategy for conserving energy during swimming. Received: 14 February 1997 / Accepted: 14 April 1997     

Irradiance and temperature regulation of oxygenic photosynthesis and O2 consumption in a hypersaline cyanobacterial mat (Solar Lake, Egypt)

 Short-term effects of temperature and irradiance on oxygenic photosynthesis and O₂ consumption in a hypersaline cyanobacterial mat were investigated with O₂ microsensors in a laboratory. The effect of temperature on O₂ fluxes across the mat–water interface was studied in the dark and at a saturating high surface irradiance (2162 μmol photons m⁻² s⁻¹) in the temperature range from 15 to 45 °C. Areal rates of dark O₂ consumption increased almost linearly with temperature. The apparent activation energy of 18 kJ mol⁻¹ and the corresponding Q ₁₀ value (25 to 35 °C) of 1.3 indicated a relative low temperature dependence of dark O₂ consumption due to mass transfer limitations imposed by the diffusive boundary layer at all temperatures. Areal rates of net photosynthesis increased with temperature up to 40 °C and exhibited a Q ₁₀ value (20 to 30 °C) of 2.8. Both O₂ dynamics and rates of gross photosynthesis at the mat surface increased with temperature up to 40 °C, with the most pronounced increase of gross photosynthesis at the mat surface between 25 and 35 °C (Q ₁₀ of 3.1). In another mat sample, measurements at increasing surface irradiances (0 to 2319 μmol photons m⁻² s⁻¹) were performed at 25, 33 (the in situ temperature) and 40 °C. At all temperatures, areal rates of gross photosynthesis saturated with no significant reduction due to photoinhibition at high irradiances. The initial slope and the onset of saturation (E _k = 148 to 185 μmol photons m⁻² s⁻¹) estimated from P versus E _d curves showed no clear trend with temperature, while maximal photosynthesis increased with temperature. Gross photosynthesis was stimulated by temperature at each irradiance except at the lowest irradiance of 54 μmol photons m⁻² s⁻¹, where oxygenic gross photosynthesis and also the thickness of the photic zone was significantly reduced at 40 °C. The compensation irradiance increased with temperature, from 32 μmol photons m⁻² s⁻¹ at 25 °C to 77 μmol photons m⁻² s⁻¹ at 40 °C, due to increased rates of O₂ consumption relative to gross photosynthesis. Areal rates of O₂ consumption in the illuminated mat were higher than dark O₂ consumption at corresponding temperatures, due to an increasing O₂ consumption in the photic zone with increasing irradiance. Both light and temperature enhanced the internal O₂ cycling within hypersaline cyanobacterial mats. Received: 30 November 1999 / Accepted: 11 April 2000     

Temperature and plankton

The relationship between temperature and metabolism was studied in Artic copepods with regard to the concept of metabolic cold adaptation of polar poikilotherms. Temperature tolerance and respiration rates of the dominant copepods Calanus finmarchicus (Gunnerus), C. glacialis (Jaschnov), C. hyperboreus (Krøyer) and Metridia longa (Lubbeck), collected in Fram Strait, Greenland Sea, in July 1983, were studied at different temperatures. Temperature tolerance in the boreal C. finmarchicus was slightly higher than in the three Arctic species. Respiration rates at lower temperatures followed the Arrhenius equation in all species, with values for (temperature characteristics) between 11.05 and 22.95, corresponding to a Q₁₀ between 2.05 and 4.5. This increase in metabolic rate with rising temperature was not related to an increase of swimming activity, as was shown by videoanalysis. Activity was determined as average swimming speed and as frequency of certain locomotor patterns. Average swimming speed remained unchanged at all temperatures and was ca 1 cm s^-1 for all species, when only periods of active swimming were considered. The time spent with active swimming did not change with temperature in M. longa and C. finmarchicus, but decreased in c. glacialis. In C. hyperboreus it increased at 5°C and decreased again at higher temperatures. It is suggested that the increase in oxygen consumption is fully accounted for by the basal metabolism.     

Studies on short-term variations of heterotrophic activity in the Kiel Fjord

In summer, 1973, a short-term study with frequent sampling was performed in the Kiel Fjord (FRG). Temperature, salinity, number of viable bacteria, maximum uptakevelocity of glucose and acetate, concentrations of chlorophyll a, labile organic substances and ammonia and phosphate were measured. Strong variations in all parameters during short periods of time could be demonstrated. The number of viable bacteria fluctuated between 26x10⁶ and 195x10⁶ bacteria/l. Changes in the maximum uptake-velocity (V _m ) of glucose between 0.23 and 0.85 μg C l^-1 h^-1 and in the V _m of acetate between 0.36 and 2.40 μg C l^-1 h^-1 were recorded. A highly significant correlation between the number of viable bacteria and the maximum uptake-velocity of the two solutes was found. It is assumed that, at least for this area, at certain times the plate counts represent a major part of the active bacteria flora.     

Influence of algal concentration and temperature on the filtration rate of Mytilus edulis

The filtration rates of Mytilus edilis (=galloprovincialis; 40 mm) were determined in relation to food concentration and temperature, using pure suspensions of the unicellular alga Platymonas suecica in concentrations ranging from 3x10⁵ cells/l to 1.5x10⁸ cells/l. The rate of filtration (ml/h/mussel) generally decreased as cell concentrations increased, and dropped to low values when concentrations above 5x10⁷ cells/l were supplied. The amount of water swept clear varied continuously, and noticeable differences in the filtration activity of M. edulis were observed over short time intervals (5 min). Fluctuations of filtered volumes per unit time were greater with lower than with higher concentrations of algae. The influence of temperature on filtration activity was highest between 5°–15°C and 25°–30°C. A temperature increase from 15° to 25°C resulted in only a slight increase in filtration rate. At 5° and 30°C, filtration dropped to very low values, namely 350 and 100 ml/h, respectively. The temperature coefficients for the filtration rates of M. edulis were determined as: Q₁₀ (5° to 15°C)=4.96; Q₁₀ (10° to 20°C)=1.22. The amount of algae cells ingested per mussel per hour is directly related to food concentration. The maximum number of cells filtered/mussel/h in an algal suspension of 70x10⁶ cells/l was 21.5x10⁵ cells/h. Cell concentrations of up to 40x10⁶ cells/l were swept clear without producing pseudofaeces. The critical cell density for M. edulis was reached at algal concentrations of 70 to 80x10⁶ cells/l. Above these concentrations no normal filtration activity was observed.     

Adjustment of the components of energy balance in the gastropod Crepidula fornicata in response to thermal acclimation

Synchronous measurements were made of the routine rate of oxygen consumption and the clearance rate of Phaeodactylum tricornutum at different exposure temperatures by specimens of the suspension-feeding gastropod Crepidula fornicata which had been acclimated to temperatures between 10° and 25°C. The results show that the cost of activity (l O₂ consumed h^-1/ml seawater cleared h^-1) increases dramatically in individuals exposed to short-term increases of temperature up to 30°C, especially in limpets acclimated to 10°C. The process of thermal acclimation, however, results in two compensatory adjustments in energy expenditure and uptake which profoundly affect the energetics of water transport. Firstly, the routine oxygen consumption shows lateral translation of the rate-temperature curve which results in the maintenance of a relatively uniform energy expenditure despite an increase in acclimation temperature from 10° to 25°C. Secondly, because of the form of the rate-temperature curve for filtration by C. fornicata, lateral translation in response to warm acclimation results in an increase in the maximal clearance rate. Lateral translation of the rate-temperature curves for feeding rates and for oxygen consumption in response to thermal acclimation may thus be linked to maintain a balance between energy gain and expenditure. In this way, the greatly increased cost of activity which would occur with increase of temperature in the absence of acclimation is evaded. The minimal maintenance energy requirement, and hence the greatest scope for growth and reproduction, is then adjusted to coincide with temperatures prevailing in the environment.     

Tail beat frequency as a predictor of swimming speed and oxygen consumption of saithe (<Emphasis Type="Italic">Pollachius virens</Emphasis>) and whiting (<Emphasis Type="Italic">Merlangius merlangus</Emphasis>) during forced swimming

Oxygen consumption and tail beat frequency were measured on saithe (Pollachius virens) and whiting (Merlangius merlangus) during steady swimming. Oxygen consumption increased exponentially with swimming speed, and the relationship was described by a power function. The extrapolated standard metabolic rates (SMR) were similar for saithe and whiting, whereas the active metabolic rate (AMR) was twice as high for saithe. The higher AMR resulted in a higher scope for activity in accordance with the higher critical swimming speed (U _crit) achieved by saithe. The optimum swimming speed (U _opt) was 1.4 BL s⁻¹ for saithe and 1.0 BL s⁻¹ for whiting with a corresponding cost of transport (COT) of 0.14 and 0.15 J N⁻¹ m⁻¹. Tail beat frequency correlated strongly with swimming speed as well as with oxygen consumption. In contrast to swimming speed and oxygen consumption, measurement of tail beat frequency on individual free-ranging fish is relatively uncomplicated. Tail beat frequency may therefore serve as a predictor of swimming speed and oxygen consumption of saithe and whiting in the field.     

An energy budget for the free-swimming and metamorphosing larvae of Balanus balanoides (Crustacea: Cirripedia)

Analysis of biochemical components and measurements of oxygen consumption rates of cypris larvae of Balanus balanoides (L.) maintained in the laboratory at 10°C for up to 5 weeks after capture shows that lipid is the primary energy reserve, although later protein is utilised. Initially, the cyprids swim freely with an oxygen consumption rate of ca. 37×10^-3 l O₂ h^-1 cyprid^-1, but within a few days the rate falls to ca. 21×10^-3 l O₂ h^-1 cyprid^-1 when they cease swimming and explore the substratum. The cost of metamorphosis was calculated both from the loss of biochemical components and oxygen consumption rates during metamorphosis; the values were 2.8×10^-2 and 3.2×10^-2 cal cyprid^-1, respectively. A budget was collated from the data on respiration and biochemical composition, whereby the energy per cyprid was partitioned into that required for essential structural components (6.8×10^-2 cal), that needed for metamorphosis (3.0×10^-2 cal) and an excess available for swimming and exploring, which in the batches studied was about 5.0×10^-2 cal. This excess is mainly derived from the utilisation of lipid reserves and is used up usually 2 1/2 to 4 weeks after capture. During these measurements, samples of cyprids were taken at weekly intervals to test the rate of settlement and success of metamorphosis. The results showed that they lose their competence to metamorphose successfully approximately at the same time (3 to 4 weeks) that the energy supply for swimming and exploration is used up.     

Activity and metabolism of larval Atlantic cod (Gadus morhua) from Scotian Shelf and Newfoundland source populations

Patterns of activity and metabolism were investigated in larval Atlantic cod (Gadus morhua L.) between December 1991 and July 1992: (1) throughout larval development; (2) between two genetically discrete populations (Scotian Shelf and Newfoundland) and (3) as a function of two different culture temperatures. During the yolk-sac stage (0 to 5 d post-hatch), changes in swimming speed were not related to mass-specific metabolic rates; no portion of the mass-specific oxygen consumption could be explained by changes in activity. In the mixed feeding stage (6 to 14 d posthatch), there was a tendency for oxygen consumption to be related to changes in swimming speed. In the exogenous feeding stage (>14 d post-hatch), oxygen consumption significantly increased with swimming speed. These ontogenetic patterns of activity and metabolism were the same for larvae from the Scotian Shelf and Newfoundland populations. However, over the entire larval life and among ontogenetic stages, the metabolic cost of activity (mass-specific O₂ consumption/swimming speed) of Scotian Shelf larvae was significantly higher than that of Newfoundland larvae. When cod larvae, that had developed at 5°C, were acutely exposed to 10°C, Scotian Shelf larvae had a higher intrinsic cost of activity than Newfoundland larvae, over the entire larval life. During the exogenous feeding stage, the mean metabolic cost of activity for Newfoundland larvae raised at 10°C and tested at 10°C was significantly higher and more variable than that of larvae raised at lower temperatures. However, the metabolic cost of activity of larvae raised and tested at 10°C was not significantly different between source populations. Together these findings suggest that differences in swimming energetics reflect changing energy requirements for activity among ontogenetic stages, and reflect adaptation to regional environments among genetically discrete populations.     

Metabolism of two dominant epibenthic echinoderms measured at bathyal depths in the Santa Catalina Basin

Metabolism of two abundant echinoderm species constituting 99.6% of the epibenthic megafauna in the Santa Catalina Basin, off southern California, USA was measured at 1 300 m during the 1979 “Bathyal Expedition”. Specimens of the ophiuroid Ophiophthalmus normani and the holothurian Scotoplanes globosa, collected by the submersible “Alvin”, were individually placed in respirometers, and measured in situ for O₂ consumption and ammonium excretion rates. For O. normani, weight-specific O₂ consumption rates decreased with increasing weight and were of comparable magnitude to rates of deep-sea and shallow-water ophiuroids; excretion rates were highly variable. Population O₂ consumption and excretion rates for O. normani (estimated from size-frequency distribution, abundance, and rate regression equations) were 1 129.28 μl O₂ m^-2 h^-1 and 27.30 nmol NH ₄ ⁺ m^-2 h^-1. Weight-specific O₂ consumption and ammonium excretion rates of S. globosa decreased with increasing weight and were of comparable magnitude to rases of shallow-water holothurians. Population O₂ constimption and excretion rates of S. globosa were 1.38 μl O₂ m^-2 h^-1 and 4.86 nmol NH ₄ ⁺ m^-2 h^-1. Combined population O₂ consumption rates for O. normani and S. globosa are of comparable magnitude to that of the sediment community and plankton in the benthic boundary layer (sediment and overlying 50 m water column) of the Santa Catalina Basin.     

Effect of temperature on the escape responses of larval herring,Clupea harengus

Herring (Clupea harengus L.) larvae from spring and autumn spawning stocks were reared at different constant temperatures from 5° to 17 °C. At equivalent developmental stages, the spring larvae were longer than the autumn larvae and the larvae reared at low temperatures were longer than those reared at high temperatures. At hatching and at the end of the yolk-sac stage, the larvae were induced, by a probe, to make C-start escape responses, which were recorded and analysed using a high-speed video recording at 400 frames s^-1. The response was rapid and of short duration. The tailbeat frequency and swimming speed were measured during the burst of swimming following the C-start at different test temperatures and in larvae with different temperature histories. The tail-beat frequency was strongly temperature-dependent, rising from 19 Hz at 5 °C to 37 Hz at 17 °C with no effect of temperature history, season or developmental stage. The burst-swimming speed ranged at hatching from 75 to 90 mm s^-1 at 5 °C to 110 to 160 mm s^-1 at 17 °C and at yolk resorption from 90–115 mm s^-1 at 5 °C to 175–190 mm s^-1 at 17 °C. The longer, spring-spawned larvae swam faster than the shorter autumn-spawned larvae. When the swimming speeds were expressed as body lengths (L) s^-1, these differences disappeared. Larvae swam from 7–9 L s^-1 at 5 °C to 15–20 L s^-1 at 17 °C at hatching, and from 8–9 L s^-1 at 5 °C to 15–17 L s^-1 at 17 °C at yolk resorption. There was, however, a significantly faster specific swimming speed by the larvae reared at 12 °C in spring 1991.Honorary Research Fellow of the Scottish Association for Marine ScienceUnfortunately, Karen Fretwell was drowned in an accident on 9 January 1993