Effects of lateral morphology on swimming performance in two sturgeon species

Fish express a high degree of diversity in morphology, which is closely related to behaviors such as swimming ability. The effect of morphology on swimming performance is explored using geometric morphometric analyses and classic critical swimming speed (U_crit) tests in Chinese sturgeon Acipenser sinensis and Siberian sturgeon A. baerii. It was found that A. sinensis is a stronger swimmer compared to A. baerii, with an average 25% higher U_crit (expressed in body lengths per second). In A. sinensis, the depth and length of the snout and the trailing edge length of the dorsal fin were negatively correlated with U_crit, whereas the height of the trunk anterior, the leading edge length of the dorsal fin and anal fin, and the length and width of the ventral lobe were positively related to U_crit; similar relationships between U_crit and morphological characters of the anterior trunk, dorsal fin, anal fin and caudal fin were found in A. baerii. Moreover, although the degree of upward bending of the snout of A. baerii was negatively related to U_crit, there was a positive relationship between the length of the caudal peduncle and U_crit as well as between the dorsal tail lobe and U_crit. In addition, the streamline index (SI) was calculated by comparing landmark coordinates on the trunk displayed in the relative warp, with its corresponding point on the NACA (the U.S. National Advisory Committee for Aeronautics) airfoil shape. SI showed that the body shape in RW1 of the A. baerii with more swimming capacity was more approximate to the NACA 0016 airfoil shape, but there was no such symmetry for A. sinensis, possibly due to body bending caused by stiffness.     

The influence of flume length and group size on swimming performance in shortnose sturgeon Acipenser brevirostrum

The main objectives of this study were to determine optimal methodologies to assess the general swimming performance of juvenile shortnose sturgeon Acipenser brevirostrum. Swimming densities (group v. individual swimming) and flume length (2 v. 1 m) were altered to verify if any of those variables affected performance (i.e. time to fatigue) during critical swimming (U(crit)) and endurance tests. Results for both U(crit) and endurance swimming were not significantly different between fish swum in groups of five or fish swum individually. The U(crit) values, however, were c. 22% higher for fish swum in a longer flume. Although swimming fish in groups did not improve swimming performance, group swimming lowered the variance of the data. Results also reveal that juvenile A. brevirostrum may not possess an ability to swim at high speeds (i.e. burst phase) for long periods.     

The effect of substratum type on aspects of swimming performance and behaviour in shortnose sturgeon Acipenser brevirostrum

The swimming performance and associated swimming behaviour (i.e. substratum‐skimming, station‐holding and free swimming) were assessed in shortnose sturgeon Acipenser brevirostrum during critical swimming and endurance swimming tests over a rough and a smooth substratum. It was hypothesized that the addition of a rough substratum in the swimming flume may provide a surface for the A. brevirostrum to grip and offer an energetic advantage. Substratum type did not affect the critical swimming performance, but A. brevirostrum consistently performed more bottom behaviours (i.e. substratum‐skimming and station‐holding) while on a smooth substratum. Acipenser brevirostrum had little contact with the rough substratum until the velocity was >1 body length s^?1. Endurance swimming time was significantly lower for A. brevirostrum over the rough bottom at the highest velocity (30 cm s^?1) which may be attributed to the observed increase in free swimming and decrease in bottom behaviours. During endurance swimming, the rough substratum was mainly used at intermediate velocities, suggesting that there may be a stability cost associated with being in contact with the rough substratum at certain velocities.     

The effects of temperature on swimming performance of juvenile shortnose sturgeon (Acipenser brevirostrum)

The swimming performance of juvenile shortnose sturgeon (～16 cm TL, ～20 g), Acipenser brevirostrum, was quantified with regards to temperature (5 to 25°C) using both increased (U_crit) and fixed velocity (endurance) tests in a laboratory setting. Sturgeons were found to show reduced U_crit values at 5 and 10°C (25.99 and 28.86 cm s^?1 respectively), with performance beginning to plateau at 15°C through 25°C (33.99 cm s^?1). For the endurance protocol, fish were tested at speeds of 35, 40 and 45 cm s^?1 at 5, 15 and 25°C. Performance within a single speed was similar at all temperatures, indicating the usage of anaerobic metabolism to fuel locomotion at these higher velocities. Overall, shortnose sturgeon demonstrated high tolerance towards a wide range of temperatures but showed few differences between performance levels at colder or warmer water conditions.     

The effects of chronic developmental hypoxia on swimming performance in zebrafish

Relative to normoxia-reared fish, hypoxia-reared zebrafish Danio rerio achieved 24·9 and 21·4% slower maximal swim velocities in both normoxic and hypoxic waters, respectively. Hypoxia-reared fish also produced 26·1 and 63·9% less lactate during resting conditions across both normoxic and hypoxic waters, respectively. During exercise, this trend continued as hypoxia-reared fish produced 68·2 and 55·1% less lactate across both normoxic and hypoxic waters, respectively. This reduction in performance, rather than representing a purely pathological (maladaptive) response to hypoxia, appears to represent a fundamental shift in the metabolic response to hypoxia.     

Navigation impacts on freshwater fish assemblages: the ecological relevance of swimming performance

Waterways provide many ecological and socialservices, such as water supply, navigation,freshwater reservoirs for aquatic organisms,recreation, and fisheries. However, in heavilydeveloped waterways, the diversity andproductivity of fish assemblages typicallybecome reduced, mainly due to migrationbarriers, pollution, habitat loss, and biotopesimplification. Additionally, navigation maydirectly or indirectly reduce fish assemblages,amplifying the effects of habitat destruction.This study summarizes navigation impacts toimprove the evaluation of direct navigationeffects on fish assemblages. Literature onhydraulic forces created by moving tows wasreviewed to compare the pressures induced byshipping with the biological capabilities offish, especially with their swimming speeds.Available studies of swimming performance offreshwater fishes were compiled to developgeneral models of length-specific burst, aswell as critical swimming speeds. Modelsregressing total length on burst and criticalswimming speeds were highly significant.Linking applied hydrology and hydraulicengineering with fish ecology and physiology,absolute speed was concluded to be the bestpredictor for thresholds and limitations ofhabitat use by fish. A navigation-inducedhabitat bottleneck hypothesis (NBH) wasinferred from the threshold flow velocity,determining habitat availability for fish.According to the NBH presented here, swimmingperformance of juvenile freshwater fish is themajor bottleneck for fish recruitment inwaterways, as a result of their inability towithstand bank-directed navigation-inducedphysical forces. In essence, under commonnavigation conditions, with respect to inlandwaterway morphology, channel cross section,vessel speeds, and dimensions of commercialvessels, the navigation-induced return currentsalong the shore are usually around 0.8 ms^–1 (0.7–1.0 m s^–1) accompanied by a0.1–0.3 m drawdown. Under such conditions, theproposed threshold for small fish survival wasestimated to be 147 mm total length at criticalswimming performance (>20 s – 60 min withoutfatigue) and 47 mm at burst performance (<20s). These theoretical findings were supportedby empirical studies of fish recruitment inwaterways. The strong dependence of fishrecruitment on hydraulic forces opens uppossibilities of formulating suitable criteriafor safe ship operation (speed and distance tobank), as well as for effective fairwaymanagement (construction and maintenance) andsustainable fish conservation (species andproduction). A more ecologically orientatedhydraulic engineering will not constraincommercial navigation and their socioeconomicbenefits, but it will substantially enhancefish recruitment in waterways and theirecological sustainability, for the overallbenefit of fish, fisheries, and society.     

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.     

The effects of low-speed swimming following exhaustive exercise on metabolic recovery and swimming performance in brook trout (Salvelinus fontinalis)

Experiments were conducted to determine whether low-speed swimming during recovery from exhaustive exercise improved both metabolic recovery and performance during a swimming challenge. For these experiments, brook trout were allowed to recover from exhaustive exercise for 2 h while swimming at 0, 0.5, 1.0, or 1.5 body length (BL) s(-1) or allowed to recover from exhaustive exercise for 1, 2, or 3 h while swimming at 1.0 BL s(-1). At the appropriate interval, either (i) muscle and blood samples were removed from the fish or (ii) fish were assessed for performance (i.e., fatigue time) during a fixed-interval swimming test. Low-speed swimming during recovery from exhaustive exercise resulted in significantly longer fatigue times compared with fish recovering in still water (i.e., 0 BL s(-1)). However, swimming during recovery did not expedite recovery of muscle lactate or blood variables (e.g., lactate, osmolarity, glucose). These observations suggest that metabolic recovery and subsequent swimming performance may not be directly linked and that other factors play a role in swimming recovery in brook trout.     

Effects of acoustic tagging on juvenile green sturgeon incision healing,swimming performance,and growth

Ultrasonic telemetry is a preferred method for fish-movement studies. Despite surgical tag implantation being the most common method for affixing tags, many studies lack tests addressing the assumption that tagging has no effect on fish performance or survival. The threatened, anadromous green sturgeon, Acipenser medirostris, has little documentation concerning its movements. We evaluated the effects of surgery and tag implantation in juveniles. We compared three groups: tagged fish with dummy transmitters implanted in the peritoneal cavity, sham fish that underwent surgery without tag implantation, and control fish that were handled and anesthetized but did not undergo surgery. We found no differences in growth or critical swimming velocity among groups. Photos of incisions were taken towards the beginning and at the end of the study to assess inflammation and to score each incision for closure and suture retention. Inflammation declined similarly for tagged and sham fish during the study. U_crit was not related to the extent of inflammation or to post-surgery time. All fish showed healing during the study (ca. 140 day duration) and 10 % of tagged and sham fish showed signs of inflammation by the study end. These results suggest that current ultrasonic surgical tagging methods do not significantly affect the short-term growth or swimming performance of juvenile green sturgeon. Additionally, effects of surgery can be mitigated by minimizing the number of suture entry points and by using rapid-absorbing sutures.     

Field swimming performance of bluegill sunfish,Lepomis macrochirus: implications for field activity cost estimates and laboratory measures of swimming performance

Mobility is essential to the fitness of many animals, and the costs of locomotion can dominate daily energy budgets. Locomotor costs are determined by the physiological demands of sustaining mechanical performance, yet performance is poorly understood for most animals in the field, particularly aquatic organisms. We have used 3‐D underwater videography to quantify the swimming trajectories and propulsive modes of bluegills sunfish (Lepomis macrochirus, Rafinesque) in the field with high spatial (1–3 mm per pixel) and temporal (60 Hz frame rate) resolution. Although field swimming trajectories were variable and nonlinear in comparison to quasi steady‐state swimming in recirculating flumes, they were much less unsteady than the volitional swimming behaviors that underlie existing predictive models of field swimming cost. Performance analyses suggested that speed and path curvature data could be used to derive reasonable estimates of locomotor cost that fit within measured capacities for sustainable activity. The distinct differences between field swimming behavior and performance measures obtained under steady‐state laboratory conditions suggest that field observations are essential for informing approaches to quantifying locomotor performance in the laboratory.     

Cohesive social behaviour shortens the stress response: the effects of conspecifics on the stress response in lake sturgeon Acipenser fulvescens

An examination was made of whether social interactions can have a beneficial effect through the attenuation of the stress response in a social species. In the first experiment, one larger (mean ± s . e . 194·0 ± 12·5 g) and seven smaller (32·0 ± 2·6 g) juvenile lake sturgeon Acipenser fulvescens were placed in tanks to determine whether a classic dominance effect would be established based on body size ( n = 6). Large fish did not establish a territory or aggressively interact with smaller fish, as there were no significant differences in nearest-neighbour distances and an absence of aggressive behaviour (biting, chasing and pushing). In the second experiment, it was hypothesized that the presence of conspecifics would have a beneficial effect through an attenuation of the stress response. Fish in groups or isolation were stressed by a brief aerial exposure (30 s), and blood plasma was measured at regular time intervals (0, 20, 40, 60, 120 and 240 min) following the stressor via an implanted cannula ( n = 9–11). The presence of conspecifics did not affect the peak cortisol response, however, the overall cortisol response was shorter in duration compared to fish in isolation. Furthermore, secondary stress variables (plasma ions and glucose) showed differences between fish in groups and isolation. The results of these experiments suggest that social interaction plays an important and beneficial role in regulating the stress response in cohesive social species such as A. fulvescens .     

The metabolic response to exercise in chronic alcoholics

The metabolic response to steady exercise was studied in six chronic alcoholics and six normal control subjects. Higher concentrations of lactated and pyruvate were observed in the alcoholics during exercise and they also developed post-exercise ketosis. These changes were probably not due to reduced fitness of the alcoholics as the heart rates of both groups were similar. Alcoholics had lower levels of growth hormone during exercise compared with the controls suggesting that chronic alcohol consumption has a depressor effect on pathways regulating the release of growth hormone.     

The effects of feeding on the swimming performance and metabolic response of juvenile southern catfish,Silurus meridionalis,acclimated at different temperatures

To test whether the effects of feeding on swimming performance vary with acclimation temperature in juvenile southern catfish (Silurus meridionalis), we investigated the specific dynamic action (SDA) and swimming performance of fasting and feeding fish at acclimation temperatures of 15, 21, 27, and 33 °C. Feeding had no effect on the critical swimming speeding (U_crit) of fish acclimated at 15 °C (p = 0.66), whereas it elicited a 12.04, 18.70, and 20.98% decrease in U_crit for fish acclimated at 21, 27 and 33 °C, respectively (p < 0.05). Both the maximal postprandial oxygen consumption rate (VO_2peak) and the active metabolic rate (VO_2active, maximal aerobic sustainable metabolic rate of fasting fish) increased significantly with temperature (p < 0.05). The postprandial maximum oxygen consumption rates during swimming (VO_2max) were higher than the VO_2active of fasting fish at all temperature groups (p < 0.05). The VO_2max increased with increasing temperature, but the relative residual metabolic scope (VO_2max? VO_2peak) during swimming decreased with increasing in temperature. The present study showed that the impairment of postprandial swimming performance increased with increasing temperature due to the unparalleled changes in the catfish's central cardio-respiratory, peripheral digestive and locomotory capacities. The different metabolic strategies of juvenile southern catfish at different temperatures may relate to changes in oxygen demand, imbalances in ion fluxes and dissolved oxygen levels with changes in temperature.     

The rising cost of warming waters: effects of temperature on the cost of swimming in fishes

Understanding the effects of water temperature on the swimming performance of fishes is central in understanding how fish species will respond to global climate change. Metabolic cost of transport (COT)-a measure of the energy required to swim a given distance-is a key performance parameter linked to many aspects of fish life history. We develop a quantitative model to predict the effect of water temperature on COT. The model facilitates comparisons among species that differ in body size by incorporating the body mass-dependence of COT. Data from 22 fish species support the temperature and mass dependencies of COT predicted by our model, and demonstrate that modest differences in water temperature can result in substantial differences in the energetic cost of swimming.     

Size-related effects and the influence of metabolic traits and morphology on swimming performance in fish

Energy metabolism fuels swimming and other biological processes. We compared the swimming performance and energy metabolism within and across eight freshwater fish species. Using swim tunnel respirometers, we measured the standard metabolic rate (SMR) and maximum metabolic rate (MMR) and calculated the critical swimming speed (U_crit). We accounted for body size, metabolic traits, and some morphometric ratios in an effort to understand the extent and underlying causes of variation. Body mass was largely the best predictor of swimming capacity and metabolic traits within species. Moreover, we found that predictive models using total length or SMR, in addition to body mass, significantly increased the explained variation of U_crit and MMR in certain fish species. These predictive models also underlined that, once body mass has been accounted for, U_crit can be independently affected by total length or MMR. This study exemplifies the utility of multiple regression models to assess within-species variability. At interspecific level, our results showed that variation in U_crit can partly be explained by the variation in the interrelated traits of MMR, fineness, and muscle ratios. Among the species studied, bleak Alburnus alburnus performed best in terms of swimming performance and efficiency. By contrast, pumpkinseed Lepomis gibbosus showed very poor swimming performance, but attained lower mass-specific cost of transport (MCOT) than some rheophilic species, possibly reflecting a cost reduction strategy to compensate for hydrodynamic disadvantages. In conclusion, this study provides insight into the key factors influencing the swimming performance of fish at both intra- and interspecific levels.     

Growth of swimming muscles and its metabolic cost in larvae of whitefish at different temperatures

The temperature relationship of routine metabolic rate (R_r) of non-feeding, non-growing Coregonus lavaretus larvae between 2 and 15°C is characterized by Q₁₀-values ranging from l.8-2.45. The rate of growth, based on weight determinations, of first-feeding larvae amounted to 3.5, 7.6 and 9.4% day-¹ at 5, 10 and 12°C respectively, from which Q₁₀-values between 4.0 and 4.8 can be calculated. The rate of increase of muscle mass between 5 and 10°C, based on the determination of the cross-sectional area of inner muscle fibres, resulted in a Q₁₀-value of 4.5. Water temperature influenced the pattern of growth of the inner muscle fibres. At hatching, after 360 day degrees, total muscle mass of larvae reared at 4 and 8°C was independent of temperature, but at 4°C the rate of mass increase owed more to hyperplasia (increase in fibre number) than to hypertrophy (increase in fibre mass), whereas at 8°C the opposite was the case. The calculation of power budgets (including the metabolic cost of growth) of first-feeding larvae yielded net conversion efficiencies (K₂) increasing with temperature from 46.3% at 5°C to 54.7% at 12°C. Comparing our data with literature data two general conclusions can be drawn. (1) In first-feeding larvae the net, but not the gross, conversion efficiency of food energy increases with temperature. This is due to net energy input being characterized by a much higher Q₁₀-value than energy expenditures. (2) In embryos of freshwater fish so far investigated hyperplasia plays a greater role in the increase of fibre mass than hypertrophy at the lower temperature, whereas in embryos of marine fish hyperplasia prevails at the higher temperature. It is suggested that this discrepancy correlates with the high concentration of free amino acids in the eggs of marine species which provide an additional, easily available, source of metabolic energy absent in freshwater species.     

Creep-feeding to stimulate metabolic imprinting in nursing beef heifers: impacts on heifer growth,reproductive and physiological variables

This experiment compared growth, physiological, and reproductive responses of beef heifers with (MI) or without (CON) access to a creep-feeder, as a manner to stimulate metabolic imprinting while nursing their dams. On day 0, 60 Angus×Hereford heifers were ranked by BW and age (140±3 kg and 68±3 days), and assigned to pairs so all ranking criteria were similar between heifers within each pair. On day 1, pairs were randomly assigned to MI (n=15) or CON (n=15). From day 1 to 51, MI pairs and their dams were allocated to 15 drylot pens where heifers had ad libitum access to a corn-based supplement through a creep-feeder. The CON pairs and their dams were maintained in an adjacent single drylot pen. From day 52 to 111, treatments were managed as a single group on a semiarid range pasture. On day 111, heifers were weaned and allocated to two pastures (one pasture/treatment), receiving hay and a corn-based concentrate until day 326. Heifer BW was recorded before and at the end of the creep-feeding period (day 1 to 51), and on days 112 and 326. On days 0, 51, 111, 187, 261, and 325, jugular blood was collected and real-time ultrasonography for longissimus muscle depth and backfat thickness assessment was performed. Blood was also collected every 10 days from days 113 to 323 for puberty evaluation via plasma progesterone. Liver and subcutaneous fat biopsies were performed on days 51, 111, 261 and 325. Average daily gain was greater (P<0.01) for MI than CON from day 1 to 51, tended (P=0.09) to be greater for CON than MI from day 112 to 326, while BW on day 326 was similar between treatments. On day 51, MI had greater (P⩽0.01) plasma IGF-I and glucose concentrations, as well as mRNA expression of hepatic pyruvate carboxylase and adipose fatty acid synthase than CON. On days 261 and 325, plasma insulin concentrations were greater (P⩽0.03) in CON than MI. Mean mRNA expression of hepatic IGF-I and adipose peroxisome proliferator-activated receptor gamma were greater (P⩽0.05) in MI than CON. No treatment effects were detected for puberty attainment rate. In conclusion, supplementing nursing heifers via creep-feeding for 50 days altered physiological and biochemical variables suggestive of a metabolic imprinting effect, but did not hasten their puberty attainment.