ASSESSMENT OF ARGOS LOCATION ACCURACY FROM SATELLITE TAGS DEPLOYED ON CAPTIVE GRAY SEALS

The Argos satellite system is commonly used to track and relay behavioral data from marine mammals, but their underwater habit results in a high proportion of locations of non-guaranteed accuracy (location classes (LC) O, A, and B). The accuracy of these locations is poorly documented in marine mammals. We assessed the accuracy of all LCs on four juvenile gray seals fitted with Argos satellite relay data loggers and held in captivity in an outdoor tank for a total of 61 seal-days. Four hundred and twenty-six locations were obtained from seals in captivity, and their latitude and longitude error was assessed before and after filtering, following MConnell et al. (1992). There was significantly more error in longitude than latitude in all LCs except I. C A. The ratio of the standard deviations of longitude : latitude ranged from 1.77 (LC 3) to 2.58 (LC 1). Filtering had very little effect on errors in LCs 3-1, but in the remaining LCs filtering resulted in error reductions ranging from 8% to 63%. In LCs O, A, and B, error reduction was greater in the 95th percentile errors, especially in longitude. The averages of the latitude and longitude 68th percentile errors and those predicted by Argos (in brackets) were 226 (150), 372 (350), and 757 (1000) m for LCs 3, 2, and 1 respectively. Both latitude and longitude errors of LCs > O were normally distributed. Both filtered and unfiltered LC A locations were of a similar accuracy to LC 1 locations, and considerably better than LC O locations.     

Evaluation of Argos Telemetry Accuracy in the High-Arctic and Implications for the Estimation of Home-Range Size

Animal tracking through Argos satellite telemetry has enormous potential to test hypotheses in animal behavior, evolutionary ecology, or conservation biology. Yet the applicability of this technique cannot be fully assessed because no clear picture exists as to the conditions influencing the accuracy of Argos locations. Latitude, type of environment, and transmitter movement are among the main candidate factors affecting accuracy. A posteriori data filtering can remove “bad” locations, but again testing is still needed to refine filters. First, we evaluate experimentally the accuracy of Argos locations in a polar terrestrial environment (Nunavut, Canada), with both static and mobile transmitters transported by humans and coupled to GPS transmitters. We report static errors among the lowest published. However, the 68^th error percentiles of mobile transmitters were 1.7 to 3.8 times greater than those of static transmitters. Second, we test how different filtering methods influence the quality of Argos location datasets. Accuracy of location datasets was best improved when filtering in locations of the best classes (LC3 and 2), while the Douglas Argos filter and a homemade speed filter yielded similar performance while retaining more locations. All filters effectively reduced the 68^th error percentiles. Finally, we assess how location error impacted, at six spatial scales, two common estimators of home-range size (a proxy of animal space use behavior synthetizing movements), the minimum convex polygon and the fixed kernel estimator. Location error led to a sometimes dramatic overestimation of home-range size, especially at very local scales. We conclude that Argos telemetry is appropriate to study medium-size terrestrial animals in polar environments, but recommend that location errors are always measured and evaluated against research hypotheses, and that data are always filtered before analysis. How movement speed of transmitters affects location error needs additional research.     

Moving in two worlds: aquatic and terrestrial locomotion in sea snakes (Laticauda colubrina,Laticaudidae)

Yellow‐lipped sea kraits (Laticauda colubrina) are amphibious in their habits. We measured their locomotor speeds in water and on land to investigate two topics: (1) to what degree have adaptations to increase swimming speed (paddle‐like tail etc.) reduced terrestrial locomotor ability in sea kraits?; and (2) do a sea krait’s sex and body size influence its locomotor ability in these two habitats, as might be expected from the fact that different age and sex classes of sea kraits use the marine and terrestrial environments in different ways? To estimate ancestral states for locomotor performance, we measured speeds of three species of Australian terrestrial elapids that spend part of their time foraging in water. The evolutionary modifications of Laticauda for marine life have enhanced their swimming speeds by about 60%, but decreased their terrestrial locomotor speed by about 80%. Larger snakes moved faster than smaller individuals in absolute terms but were slower in terms of body lengths travelled per second, especially on land. Male sea kraits were faster than females (independent of the body‐size effect), especially on land. Prey items in the gut reduced locomotor speeds both on land and in water. Proteroglyphous snakes may offer exceptional opportunities to study phylogenetic shifts in locomotor ability, because (1) they display multiple independent evolutionary shifts from terrestrial to aquatic habits, and (2) one proteroglyph lineage (the laticaudids) displays considerable intraspecific and interspecific diversity in terms of the degree to which they use terrestrial vs. aquatic habitats.     

Comparison of fin ray sampling methods on white sturgeon Acipenser transmontanus growth and swimming performance

Effects of two fin‐ray sampling methods on swimming performance, growth and survival were evaluated for hatchery‐reared sub‐adult white sturgeon Acipenser transmontanus. Fish were subjected to either a notch removal treatment in which a small section was removed from an anterior marginal pectoral‐fin ray, or a full removal treatment in which an entire marginal pectoral‐fin ray was removed. Control fish did not have fin rays removed, but they were subjected to a sham operation. A modified 3230 l Brett‐type swim tunnel was used to evaluate 10 min critical station‐holding speeds (S_CSH) of A. transmontanus, immediately after the fin ray biopsies were obtained with each method. Survival and growth were evaluated over a 6 month period for a separate group of fish subjected to the same biopsy methods. Mean ± s.e . 10 min S_CSH were 108·0 ± 2·3, 110·0 ± 2·6 and 115·0 ± 3·5 cm s^?1 for the notch removal group, full removal group and control group, respectively, and were not significantly different among treatments. Behavioural characteristics including tail‐beat frequency and time spent hunkering were also not significantly different among treatment groups swimming at the same speeds. There were no mortalities and relative growth was similar among treatment groups. Average biopsy time for the notch removal method was lower and the wounds appeared to heal more quickly compared with the full removal method.     

Maximum sustainable speed, energetics and swimming kinematics of a tropical carangid fish, the green jack Caranx caballus

Maximum sustained swimming speeds, swimming energetics and swimming kinematics were measured in the green jack Caranx caballus (Teleostei: Carangidae) using a 41 l temperature‐controlled, Brett‐type swimming‐tunnel respirometer. In individual C. caballus [mean ±s.d. of 22·1 ± 2·2 cm fork length (L_F), 190 ± 61 g, n = 11] at 27·2 ± 0·7° C, mean critical speed (U_crit) was 102·5 ± 13·7 cm s^?1 or 4·6 ± 0·9 L_F s^?1. The maximum speed that was maintained for a 30 min period while swimming steadily using the slow, oxidative locomotor muscle (U_max,c) was 99·4 ± 14·4 cm s^?1 or 4·5 ± 0·9 L_F s^?1. Oxygen consumption rate (M in mg O₂ min^?1) increased with swimming speed and with fish mass, but mass‐specific M (mg O₂ kg^?1 h^?1) as a function of relative speed (L_F s^?1) did not vary significantly with fish size. Mean standard metabolic rate (R_S) was 170 ± 38 mg O₂ kg^?1 h^?1, and the mean ratio of M at U_max,c to R_S, an estimate of factorial aerobic scope, was 3·6 ± 1·0. The optimal speed (U_opt), at which the gross cost of transport was a minimum of 2·14 J kg^?1 m^?1, was 3·8 L_F s^?1. In a subset of the fish studied (19·7–22·7 cm L_F, 106–164 g, n = 5), the swimming kinematic variables of tailbeat frequency, yaw and stride length all increased significantly with swimming speed but not fish size, whereas tailbeat amplitude varied significantly with speed, fish mass and L_F. The mean propulsive wavelength was 86·7 ± 5·6 %L_F or 73·7 ± 5·2 %L_T. Mean ±s.d . yaw and tailbeat amplitude values, calculated from lateral displacement of each intervertebral joint during a complete tailbeat cycle in three C. caballus (19·7, 21·6 and 22·7 cm L_F; 23·4, 25·3 and 26·4 cm L_T), were 4·6 ± 0·1 and 17·1 ± 2·2 %L_T, respectively. Overall, the sustained swimming performance, energetics, kinematics, lateral displacement and intervertebral bending angles measured in C. caballus were similar to those of other active ectothermic fishes that have been studied, and C. caballus was more similar to the chub mackerel Scomber japonicus than to the kawakawa tuna Euthynnus affinis.     

Ontogeny of critical and prolonged swimming performance for the larvae of six Australian freshwater fish species

Critical (<30 min) and prolonged (>60 min) swimming speeds in laboratory chambers were determined for larvae of six species of Australian freshwater fishes: trout cod Maccullochella macquariensis, Murray cod Maccullochella peelii, golden perch Macquaria ambigua, silver perch Bidyanus bidyanus, carp gudgeon Hypseleotris spp. and Murray River rainbowfish Melanotaenia fluviatilis. Developmental stage (preflexion, flexion, postflexion and metalarva) better explained swimming ability than did length, size or age (days after hatch). Critical speed increased with larval development, and metalarvae were the fastest swimmers for all species. Maccullochella macquariensis larvae had the highest critical [maximum absolute 46·4 cm s^?1 and 44·6 relative body lengths (L_B) s^?1] and prolonged (maximum 15·4 cm s^?1, 15·6 L_B s^?1) swimming speeds and B. bidyanus larvae the lowest critical (minimum 0·1 cm s^?1, 0·3 L_B s^?1) and prolonged swimming speeds (minimum 1·1 cm s^?1, 1·0 L_B s^?1). Prolonged swimming trials determined that the larvae of some species could not swim for 60 min at any speed, whereas the larvae of the best swimming species, M. macquariensis, could swim for 60 min at 44% of the critical speed. The swimming performance of species with precocial life‐history strategies, with well‐developed larvae at hatch, was comparatively better and potentially had greater ability to influence their dispersal by actively swimming than species with altricial life‐history strategies, with poorly developed larvae at hatch.     

Enhancing the use of Argos satellite data for home range and long distance migration studies of marine animals

Accurately quantifying animals' spatial utilisation is critical for conservation, but has long remained an elusive goal due to technological impediments. The Argos telemetry system has been extensively used to remotely track marine animals, however location estimates are characterised by substantial spatial error. State-space models (SSM) constitute a robust statistical approach to refine Argos tracking data by accounting for observation errors and stochasticity in animal movement. Despite their wide use in ecology, few studies have thoroughly quantified the error associated with SSM predicted locations and no research has assessed their validity for describing animal movement behaviour. We compared home ranges and migratory pathways of seven hawksbill sea turtles (Eretmochelys imbricata) estimated from (a) highly accurate Fastloc GPS data and (b) locations computed using common Argos data analytical approaches. Argos 68(th) percentile error was <1 km for LC 1, 2, and 3 while markedly less accurate (>4 km) for LC ≤ 0. Argos error structure was highly longitudinally skewed and was, for all LC, adequately modelled by a Student's t distribution. Both habitat use and migration routes were best recreated using SSM locations post-processed by re-adding good Argos positions (LC 1, 2 and 3) and filtering terrestrial points (mean distance to migratory tracks ± SD = 2.2 ± 2.4 km; mean home range overlap and error ratio = 92.2% and 285.6 respectively). This parsimonious and objective statistical procedure however still markedly overestimated true home range sizes, especially for animals exhibiting restricted movements. Post-processing SSM locations nonetheless constitutes the best analytical technique for remotely sensed Argos tracking data and we therefore recommend using this approach to rework historical Argos datasets for better estimation of animal spatial utilisation for research and evidence-based conservation purposes.     

Increasing ocean temperatures reduce activity patterns of a large commercially important coral reef fish

Large‐bodied fish are critical for sustaining coral reef fisheries, but little is known about the vulnerability of these fish to global warming. This study examined the effects of elevated temperatures on the movement and activity patterns of the common coral trout Plectropomus leopardus (Serranidae), which is an important fishery species in tropical Australia and throughout the Indo West‐Pacific. Adult fish were collected from two locations on Australia's Great Barrier Reef (23°S and 14°S) and maintained at one of four temperatures (24, 27, 30, 33 °C). Following >4 weeks acclimation, the spontaneous swimming speeds and activity patterns of individuals were recorded over a period of 12 days. At 24–27 °C, spontaneous swimming speeds of common coral trout were 0.43–0.45 body lengths per second (bls^?1), but dropped sharply to 0.29 bls^?1 at 30 °C and 0.25 bls^?1 at 33 °C. Concurrently, individuals spent 9.3–10.6% of their time resting motionless on the bottom at 24–27 °C, but this behaviour increased to 14.0% at 30 °C and 20.0% of the time at 33 °C (mean ± SE). The impact of temperature was greatest for smaller individuals (<45 cm TL), showing significant changes to swimming speeds across every temperature tested, while medium (45–55 cm TL) and large individuals (>55 cm TL) were first affected by 30 °C and 33 °C, respectively. Importantly, there was some indication that populations can adapt to elevated temperature if presented with adequate time, as the high‐latitude population decreased significantly in swimming speeds at both 30 °C and 33 °C, while the low‐latitude population only showed significant reductions at 33 °C. Given that movement and activity patterns of large mobile species are directly related to prey encounter rates, ability to capture prey and avoid predators, any reductions in activity patterns are likely to reduce overall foraging and energy intake, limit the energy available for growth and reproduction, and affect the fitness and survival of individuals and populations.     

A THREE-STAGE ALGORITHM FOR FILTERING ERRONEOUS ARGOS SATELLITE LOCATIONS

Several methods have been used to identify erroneous animal locations based on Argos satellite data. Using 15,987 satellite locations for 37 gray seals ( Haliockoerus grypus ), we tested a three-stage filtering algorithm designed to address shortcomings of other filters. In stage 1, for each location, four rates of travel were calculated—the rate to each of the two previous locations and the two subsequent locations. If all four rates exceeded 2 m/sec (95th percentile of our data), the location was removed (7.25% of total locations). Stage 2 incorporated the filtering algorithm developed by McConnell et al. (1992) resulting in the rejection of 22.75% of total locations based on reasonable assumptions of straight-line travel. At stage 3, the remaining data were evaluated against a distance threshold, defined as the 99th percentile of realized distance traveled over a period of seven days. Locations exceeding this threshold-were rejected (0.69% of total locations). Overall, the three-stage filter eliminated fewer locations (30.7 ± 1.62%), than the stage 2 filter alone. Most standard locations were retained, but 85.7% of location class 0, 76.6% of A, and 41.9% of B were also retained. These location classes account for most of data routinely collected but not used.     

Effect of age and environmental conditions on the movement characteristics of Pacific oyster (Crassostrea gigas) trochophores

The movement characteristics of Pacific oyster trochophores have received very little coverage in the scientific literature. Described here are not only changes in the swimming characteristics of Crassostrea gigas trochophores (size: 53–77 μm) in relation to time after fertilization and to inter‐female variation but also the effects of salinity and pH on movement characteristics. The percentage of motile trochophores was measured on images obtained through a dissecting microscope and the Velocity Average Path (VAP) was assessed using a Computer Assisted Sperm Analysis (CASA) system. At 20°C, the first movements of the trochophores were observed at 6.5 h post‐fertilization. The mean (± SD) percentage of swimming trochophores and the VAP observed in seawater at 11.5 h post‐fertilization were 85 ± 10% and 146 ± 75 μm s^?1, respectively (n = 8 females). Significant inter‐female variation in the percentage of motile trochophores (range: 66 ± 16–93 ± 3%) and in the VAP (55 ± 47–180 ± 90 μm s^?1) was detected. Most of the trochophores were motile in a 9‰ salinity solution. Adjusting the pH of the seawater to values from 5.10 to 9.08 had no effect on swimming characteristics. The present study shows that the movement of oyster trochophores exhibits high plasticity in relation to environmental conditions because the highest percentages of swimming trochophores and optimal velocity values were recorded within large ranges of salinity and pH. Further research is required to determine whether the swimming performances of trochophores can be used to assess embryo quality in commercial hatcheries.     

An evaluation of behavior inferences from Bayesian state‐space models: A case study with the Pacific walrus

State‐space models offer researchers an objective approach to modeling complex animal location data sets, and state‐space model behavior classifications are often assumed to have a link to animal behavior. In this study, we evaluated the behavioral classification accuracy of a Bayesian state‐space model in Pacific walruses using Argos satellite tags with sensors to detect animal behavior in real time. We fit a two‐state discrete‐time continuous‐space Bayesian state‐space model to data from 306 Pacific walruses tagged in the Chukchi Sea. We matched predicted locations and behaviors from the state‐space model (resident, transient behavior) to true animal behavior (foraging, swimming, hauled out) and evaluated classification accuracy with kappa statistics (κ) and root mean square error (RMSE). In addition, we compared biased random bridge utilization distributions generated with resident behavior locations to true foraging behavior locations to evaluate differences in space use patterns. Results indicated that the two‐state model fairly classified true animal behavior (0.06 ≤ κ ≤ 0.26, 0.49 ≤ RMSE ≤ 0.59). Kernel overlap metrics indicated utilization distributions generated with resident behavior locations were generally smaller than utilization distributions generated with true foraging behavior locations. Consequently, we encourage researchers to carefully examine parameters and priors associated with behaviors in state‐space models, and reconcile these parameters with the study species and its expected behaviors.     

COST OF TRANSPORT IN STELLER SEA LIONS, EUMETOPIAS JUBATUS

The cost of swimming is a key component in the energy budgets of marine mammals. Unfortunately, data to derive predictive allometric equations are limited, and estimates exist for only one other species of otariid. Our study measured the oxygen consumption of three juvenile Steller sea lions ( Eumetopias jubatus ) swimming in a flume tank at velocities up to 2.2 m sec⁻¹. Minimum measured cost of transport ranged from 3.5–5.3 J kg⁻¹ m⁻¹, and was reached at swimming speeds of 1.7–2.1 m s⁻¹. These cost-of-transport values are higher than those reported for other marine mammals. However, once differences in stationary metabolic rate were accounted for, the locomotor costs (LC) for the Steller sea lions were commensurate with those of other marine mammals. Locomotor costs (LC in J m⁻¹) appeared to be directly proportional to body mass (M in kg) such that LC = 1.651M^1.01. These estimates for the cost of locomotion can be incorporated into bioenergetic models and used to determine the energetic consequences of observed swimming behavior in wild marine mammals.     

Swimming patterns and behaviour of upriver-migrating adult pink (Oncorhynchus gorbuscha) and sockeye (O. nerka) salmon as assessed by EMG telemetry in the Fraser River,British Columbia,Canada

Little is known about the behaviour patterns and swimming speed strategies of anadromous upriver migrating fish. We used electromyogram telemetry to estimate instantaneous swimming speeds for individual sockeye (Oncorhynchus nerka) and pink salmon (O. gorbuscha) during their spawning migrations through reaches which spanned a gradient in river hydraulic features in the Fraser River, British Columbia. Our main objectives were to describe patterns of individual-specific swim speeds and behaviours, identify swimming speed strategies and contrast these between sexes, species and reaches. Although mean swimming speeds did not differ between pink salmon (2.21 BL s^–1) and sockeye salmon (1.60 BL s^–1), sockeye salmon were over twice as variable (mean CV; 54.78) in swimming speeds as pink salmon (mean CV; 22.54). Using laboratory-derived criteria, we classified swimming speeds as sustained (<2.5 BL s^–1), prolonged (2.5–3.2 BL s^–1), or burst (>3.2 BL s^–1). We found no differences between sexes or species in the proportion of total time swimming in these categories – sustained (0.76), prolonged (0.18), burst (0.06); numbers are based on species and sexes combined. Reaches with relatively complex hydraulics and fast surface currents had migrants with relatively high levels of swimming speed variation (e.g., high swimming speed CV, reduced proportions of sustained speeds, elevated proportions of burst speeds, and high rates of bursts) and high frequency of river crossings. We speculate that complex current patterns generated by river constrictions created confusing migration cues, which impeded a salmon's ability to locate appropriate pathways.     

The effect of vessel speed on the survivorship of biofouling organisms at different hull locations

This study used a specially designed MAGPLATE system to quantify the en route survivorship and post-voyage recovery of biofouling assemblages subjected to short voyages (<12 h) across a range of vessel speeds (slow, medium, fast; in the range 4.0–21.5 knots). The effect of hull location (bow, amidships and stern) was also examined. While no significant differences were evident in en route survivorship of biofouling organisms amongst hull locations, biofouling cover and richness were markedly reduced on faster vessels relative to slower craft. Therefore, the potential inoculum size of non-indigenous marine species and richness is likely to be reduced for vessels that travel at faster speeds (>14 knots), which is likely to also reduce the chances of successful introductions. Despite this, the magnitude of introductions from biofouling on fast vessels can be considered minor, especially for species richness where 90% of source-port species were recorded at destinations.     

Heart rates of Atlantic salmon Salmo salar during a critical swim speed test and subsequent recovery

In this study, heart rate (HR) bio-loggers were implanted in the abdominal cavity of 12 post-smolt Atlantic salmon Salmo salar weighing 1024 ± 31 g and acclimated to 12°C sea water. One week after the surgical procedure, a critical swim speed (U_crit) test was performed on tagged and untagged conspecifics, whereafter tagged fish were maintained in their holding tanks for another week. The U_crit was statistically similar between tagged and untagged fish (2.67 ± 0.04 and 2.74 ± 0.05 body lengths s⁻¹, respectively) showing that the bio-logger did not compromise the swimming performance. In the pre-swim week, a diurnal cycle was apparent with HR peaking at 65 beats min⁻¹ during the day and approaching 40 beats min⁻¹ at night. In the U_crit test, HR increased approximately exponentially with swimming speed until a plateau was reached at the final speed before fatigue with a maximum of 85.2 ± 0.7 beats min⁻¹. During subsequent recovery tagged fish could be divided into a surviving group (N = 8) and a moribund group (N = 4). In surviving fish HR had fully recovered to pre-swim levels after 24 h, including reestablishment of a diurnal HR cycle. In moribund fish HR never recovered and remained elevated at c. 80 beats min⁻¹ for 4 days, whereafter they started dying. We did not identify a proximal cause of death in moribund fish, but possible explanations are discussed. Tail beat frequency (TBF) was also measured and showed a more consistent response to increased swimming speeds. As such, when exploring correlations between HR, TBF and metabolic rates at different swimming speeds, TBF provides better predictions. On the contrary, HR measurements in free swimming fish over extended periods of time are useful for other purposes such as assessing the accumulative burden of various stressors and recovery trajectories from exhaustive exercise.     

Fish swimming stride by stride: speed limits and endurance

Summary Steadily swimming fish show a species-specific stride length and tail tip amplitude. These are constant over the entire speed range if expressed as a fraction of the body length. The speed of a fish equals the stride length times the tail beat frequency. We describe how maximum tail beat frequencies, and hence maximum swimming speeds, are related to temperature and body length.Maximum sustained swimming speeds, endurance during swimming at higher speeds, and maximum burst velocities of 27 species are compared. The rate of decline of endurance with increasing speed is either gradual or steep, with only a few cases in between Steady swimmers show the steepest decline.The published effects of temperature on endurance are not consistent.The effect of body size on the endurance curve could be investigated for two species. The maximum sustained speed decreases with increasing length, and the slope of the endurance curves steepens with increasing length with the same factor in both species. The maximum burst speed is 10 Ls^-1 on average.     

Extreme physiological adaptations as predictors of climate‐change sensitivity in the narwhal,Monodon monoceros

Rapid changes in sea ice cover associated with global warming are poised to have marked impacts on polar marine mammals. Here we examine skeletal muscle characteristics supporting swimming and diving in one polar species, the narwhal, and use these attributes to further document this cetacean's vulnerability to unpredictable sea ice conditions and changing ecosystems. We found that extreme morphological and physiological adaptations enabling year‐round Arctic residency by narwhals limit behavioral flexibility for responding to alternations in sea ice. In contrast to the greyhound‐like muscle profile of acrobatic odontocetes, the longissimus dorsi of narwhals is comprised of 86.8%± 7.7% slow twitch oxidative fibers, resembling the endurance morph of human marathoners. Myoglobin content, 7.87 ± 1.72 g/100 g wet muscle, is one of the highest levels measured for marine mammals. Calculated maximum aerobic swimming distance between breathing holes in ice is <1,450 m, which permits routine use of only 2.6%–10.4% of ice‐packed foraging grounds in Baffin Bay. These first measurements of narwhal exercise physiology reveal extreme specialization of skeletal muscles for moving in a challenging ecological niche. This study also demonstrates the power of using basic physiological attributes to predict species vulnerabilities to environmental perturbation before critical population disturbance occurs.     

Effects of acute temperature changes on the swimming abilities and oxygen consumption of Ptychobarbus kaznakovi from the Lancang River

Water temperature is known to be a particularly important environmental factor that affects fish swimming performance, but it is unknow how acute temperature changes affect the fish performance of Ptychobarbus kaznakovi. P. kaznakovi in the Lancang River have declined quickly in recent years, and this species was used to examine the effects of acute temperature changes on swimming abilities and oxygen consumption in a Brett‐type swimming tunnel respirometer. The standard metabolic rate (SMR) and routine metabolic rate (RMR) showed 216% and 134% increases, respectively, at 22°C (an acute increase from 17 to 22°C) compared to those at 12°C (an acute decrease from 17 to 12°C). Moreover, the RMR was approximately 1.7, 1.6 and 1.3 times the value of the SMR at 12°C, 17°C and 22°C, respectively. The critical swimming speed (U_crit) of P. kaznakovi at 22°C was 5.45 ± 0.45BL/S, which was 45% higher than that at 12°C (3.77 ± 0.92BL/S). The oxygen consumption rates (MO₂) reached their maximum values at swimming speeds near the U_crit for all the temperature treatments. The maximum metabolic rate (MMR) values at 12°C, 17°C and 22°C were 274.53 ± 142.60 (mgO₂ kg^?1 hr^?1), 412.85 ± 216.34 (mgO₂ kg^?1 hr^?1) and 1,095.73 ± 52.50 (mgO₂ kg^?1 hr^?1), respectively. Moreover, there was a narrow aerobic scope at 12°C compared to that at 17°C and 22°C. The effect of acute temperature changes on the swimming abilities and oxygen consumption of P. kaznakovi indicated that water temperature changes caused by dam construction could directly affect energy consumption during the upstream migration of fish.     

Patterns in early embryonic motility: effects of size and environmental temperature on vertical velocities of sinking and swimming echinoid blastulae

Early embryonic swimming is widespread among marine invertebrates, but quantitative information about swimming behaviors is scarce. Swimming may affect encounters with predators, positioning in the water column, and nutrient absorption. Measured rates and patterns of swimming and sinking for blastulae of four eastern Pacific echinoid species show that sinking speeds equal or exceed swimming speeds. Swimming speed scaled negatively with embryo size, though sinking speed did not scale with size. Analysis of swimming paths of Strongylocentrotus franciscanus revealed a temperature dependency in swimming pattern that affected speed of upward movement. Sinking speeds were significantly greater at 10 degrees C than at 14 degrees C for blastulae of all four species examined. In Dendraster excentricus, killing the blastulae annulled this temperature effect, indicating an active density regulation by these embryos. Finally, measurements of particle velocities around sinking and swimming D. excentricus blastulae show that swimming creates a more localized disturbance than sinking. Embryonic swimming may therefore decrease rather than increase encounters with pelagic predators. Results from subsequent experiments in which embryos were reared in low-oxygen environments suggest that any oxygen-absorption advantages of swimming have little, if any, effect on the development of D. excentricus embryos.