Routine Swimming Research Articles

Environmental levels of atrazine and its degradation products impair survival skills and growth of red drum larvae

Red drum larvae ( Sciaenops ocellatus) were exposed to environmentally realistic and sublethal levels of the herbicide atrazine (2-chloro-4-ethylamin-6-isopropylamino- S-triazine) to evaluate its effects on ecologically critical traits: growth, behavior, survival potential, and resting respiration rate. Settlement size larvae (7 mm total length) were given an acute exposure of atrazine at 0, 40, and 80 μg l −1 for 4 days. Tests of 96 h survival confirmed that these naturally occurring concentrations were sublethal for red drum larvae. Growth, routine swimming, antipredator responses to artificial and actual predators, and resting respiration rate were monitored 1 and 3 days after onset of exposure. Atrazine exposure significantly reduced growth rate. Atrazine-exposed larvae also exhibited significantly higher routine swimming speeds, swam in more convoluted paths, and were hyperactive. Responses to artificial and actual predators were not affected by atrazine exposure nor were resting respiration rates. The higher rate of travel (86% higher in atrazine-treated larvae) resulted in higher predicted encounter rates with prey (up to 71%) and slow moving predators (up to 63%). However, hyperactivity and faster active swimming speeds of exposed larvae indicated that naturally occurring sublethal levels of atrazine will result in an elevated rate of energy utilization (doubling the total metabolic rate), which is likely to increase the risk of death by starvation. Moreover, atrazine effects on growth will prolong the larval period, which could reduce the juvenile population by as much as 24%. We conclude that environmentally realistic levels of atrazine induce behavioral and physiological effects on fish larvae that would compromise their survival expectations.

High Swimming and Metabolic Activity in the Deep‐Sea EelSynaphobranchus kaupiiRevealed by Integrated In Situ and In Vitro Measurements

Several complementary studies were undertaken on a single species of deep-sea fish (the eel Synaphobranchus kaupii) within a small temporal and spatial range. In situ experiments on swimming and foraging behaviour, muscle performance, and metabolic rate were performed in the Porcupine Seabight, northeast Atlantic, alongside measurements of temperature and current regime. Deep-water trawling was used to collect eels for studies of animal distribution and for anatomical and biochemical analyses, including white muscle citrate synthase (CS), lactate dehydrogenase (LDH), malate dehydrogenase (MDH), and pyruvate kinase (PK) activities. Synaphobranchus kaupii demonstrated whole-animal swimming speeds similar to those of other active deep-sea fish such as Antimora rostrata. Metabolic rates were an order of magnitude higher (31.6 mL kg(-1) h(-1)) than those recorded in other deep-sea scavenging fish. Activities of CS, LDH, MDH, and PK were higher than expected, and all scaled negatively with body mass, indicating a general decrease in muscle energy supply with fish growth. Despite this apparent constraint, observed in situ burst or routine swimming performances scaled in a similar fashion to other studied species. The higher-than-expected metabolic rates and activity levels, and the unusual scaling relationships of both aerobic and anaerobic metabolism enzymes in white muscle, probably reflect the changes in habitat and feeding ecology experienced during ontogeny in this bathyal species.

Life in a warm deep sea: routine activity and burst swimming performance of the shrimp Acanthephyra eximia in the abyssal Mediterranean

Measurements of routine swimming speed, “tail-flip” escape responses, and oxygen consumptions were made of the deep-sea shrimp Acanthephyra eximia using autonomous landers in the Rhodos Basin at depths of up to 4,400 m and temperatures of 13–14.5°C. Routine swimming speeds at 4,200 m averaged 0.18 m s−1 or 3.09 body lengths s−1, approximately double those of functionally similar oceanic scavengers. During escape responses peak accelerations of 23 m s−2 or 630.6 body lengths s−2 were recorded, with animals reaching speeds of 1.61 m s−1 or 34.8 body lengths s−2. When compared to shallow-water decapods at similar temperatures these values are low for a lightly calcified shrimp such as A. eximia despite a maximum muscle mass specific power output of 90.0 W kg−1. A preliminary oxygen consumption measurement indicated similar rates to those of oceanic crustacean scavengers and shallower-living Mediterranean crustaceans once size and temperature had been taken into account. These animals appear to have high routine swimming speeds but low burst muscle performances. This suite of traits can be accounted for by high competition for limited resources in the eastern Mediterranean, but low selective pressure for burst swimming due to reductions in predator pressure.

Tail loss, body condition and swimming performances in tiger snakes,Notechis ater occidentalis

In limbless tetrapods such as snakes, propulsive forces are generated by lateral undulations of the body and of the tail. In a large population of tiger snakes from Western Australia, tail loss was extremely common (58% of the individuals) and often very severe (more than two-thirds of the tail was missing in 14% of the cases, and in some instances, the tail was totally lost). Tail loss was not however correlated with body size, mass or body condition of wild individuals, and hence did not influence their abilities to acquire resources. These large venomous snakes exhibit marked aquatic habits. Locomotor tests in controlled conditions revealed that tail loss had a significant negative influence on burst swimming performances. However, no effect was found on routine swimming speed and total distance travelled over 5 min. These results suggest that a long and slender tail, although important for maximal speed, is not necessarily relevant for the locomotor abilities required for successful hunting. Tail-damaged individuals outnumbered intact snakes, suggesting that tail loss did not severely compromise survival. Overall, in this species, a slight deterioration of maximal speed due to severe tail loss probably has a low (undetectable) ecological impact, at least for adults.

Fish functional design and swimming performance

Classifications of fish swimming are reviewed as a prelude to discussing functional design and performance in an ecological context. Webb (1984a, 1998) classified fishes based on body shape and locomotor mode into three basic categories: body and caudal fin (BCF) periodic, BCF transient (fast‐starts, turns) and median and paired fin (MPF) swimmers. Swimming performance and functional design is discussed for each of these categories. Webb hypothesized that specialization in any given category would limit performance in any other. For example, routine MPF swimmers should be penalized in BCF transient (fast‐start propulsion). Recent studies offer much support for Webb's construct but also suggest some necessary amendments. In particular, design and performance compromises for different swimming modes are associated with fish that employ the same propulsor for more than one task (coupled, e.g. the same propulsor for routine steady swimming and fast‐starts). For example, pike (BCF transient specialist) achieve better acceleration performance than trout (generalist). Pike steady (BCF periodic) performance, however, is inferior to that of trout. Fish that employ different propulsors for different tasks (decoupled, e.g. MPF propulsion for low‐speed routine swimming and BCF motions for fast‐starts) do not show serious performance compromises. For example, certain MPF low‐speed swimmers show comparable fast‐start performance to BCF forms. Arguably, the evolution of decoupled locomotor systems was a major factor underlying the adaptive radiation of teleosts. Low‐speed routine propulsion releases MPF swimmers from the morphological constraints imposed by streamlining allowing for a high degree of variability in form. This contrasts with BCF periodic swimming specialists where representatives of four vertebrate classes show evolutionary convergence on a single, optimal ‘thunniform’ design. However, recent experimental studies on the comparative performance of carangiform and thunniform swimmers contradict some of the predictions of hydromechanical models. This is addressed in regard to the swimming performance, energetics and muscle physiology of tuna. The concept of gait is reviewed in the context of coupled and decoupled locomotor systems. Biomimetic approaches to the development of Autonomous Underwater Vehicles have given a new context and impetus to research and this is discussed in relation to current views of fish functional design and swimming performance. Suggestions are made for possible future research directions.

Behavioral performance of wild-caught and laboratory-reared red drum Sciaenops ocellatus (Linnaeus) larvae

Laboratory- and hatchery-reared fish often differ morphologically, physiologically, and/or behaviorally from wild-caught fish. We compared the behavioral performance of laboratory-reared red drum ( Sciaenops ocellatus) larvae to that of wild-caught larvae to examine potential differences due to rearing and to validate interpretations of experiments on lab-reared larvae. Routine swimming speed and the timing and magnitude of startle responses elicited by acoustic and visual stimuli were measured on three size classes (developmental stages) of larvae (8, 13, and 27 mm TL). Mean routine swimming speeds were greater in wild larvae compared to reared larvae at 8 mm TL, but 27-mm wild larvae exhibited lower speeds than reared larvae at 27 mm TL. In acoustically mediated startle responses, wild larvae of all sizes were more responsive, took less time to respond, and in the 8-mm size class, had greater response distances and speeds than reared larvae. In visually mediated startle responses, 8- and 13-mm reared larvae had greater response distances and durations, while 27-mm wild larvae were less responsive than reared larvae. These observations suggest caution when inferring behavioral capabilities of wild larvae based on observations of lab-reared red drum and that behavioral deficiencies due to rearing may reduce survivorship of lab-reared red drum upon release into the environment.

The turn of the sword: length increases male swimming costs in swordtails.

Sexual selection via female mate choice can result in the evolution of elaborate male traits that incur substantial costs for males. Despite increased interest in how female mating preferences contribute to the evolution of male traits, few studies have directly quantified the locomotor costs of such traits. A sexually selected trait that could affect movement costs is the sword exhibited by male swordtail fishes: while longer swords may increase male mating success, they could negatively affect the hydrodynamic aspects of swimming activities. Here, we examine the energetic costs of the sword in Xiphophorus montezumae by experimentally manipulating sword length and measuring male aerobic metabolism during two types of activity, routine swimming and courtship swimming. Direct measurements of oxygen consumption indicate that males with longer swords expend more energy than males with shortened swords during both types of swimming. In addition, the sword increases the cost of male courtship. Thus, while sexual selection via female choice favours long swords, males with longer swords experience higher metabolic costs during swimming, suggesting that sexual and natural selection have opposing effects on sword evolution. This study demonstrates a hydrodynamic cost of a sexually selected trait. In addition, this study discriminates between the cost of a sexually selected trait used in courtship and other courtship costs.

BEHAVIOR AND RECRUITMENT SUCCESS IN FISH LARVAE: REPEATABILITY AND COVARIATION OF SURVIVAL SKILLS

Survival of larvae of highly fecund fishes is often considered to be random, although some investigators have hypothesized that survivors are exceptional individuals. If behavior is important to survival, individuals that perform both well and repeatably will be favored. We conducted experiments on red drum larvae (Sciaenops ocellatus, mean length = 7.7 mm) to assess individual variability in skills related to foraging and predator evasion. We measured routine swimming speed and, for responses to two startle stimuli, response score, latency, distance, duration, and speed. We tested 100 larvae five times each. A large proportion of larvae exhibited repeatable performance for 10 of the performance variables. However, repeatability (or performance level) in one skill was not correlated with repeatability (or level) in an independent skill, except for a positive correlation between acoustic and visual response scores. This result suggested that the level of attentiveness to predators varies among individuals. The absence of individuals with consistently low performance was taken as evidence for historical selection on performance and repeatability of escape speeds and distances. Individuals that performed repeatably or well in multiple skills represented 1–2% of the sample, which is not a trivial number of individuals when extrapolated over a female's reproductive lifetime. The persistence of many poor performers may be due to limited heritability of behavioral traits, a trade-off of behavioral skills with another selected trait, or extreme variability in the nature of mortality in coastal environments. The presence of repeatable behavior and apparent selection for a small number of related traits imply that, under some circumstances, survivors of a cohort may be individuals with exceptional behavioral skills, but behavior may be more important to survival and recruitment in fish larvae from more stable environments. Corresponding Editor: M. A. Hixon.

Aroclor 1254 affects growth and survival skills of Atlantic croaker Micropogonias undulatus larvae

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 252:295-301 (2003) - doi:10.3354/meps252295 Aroclor 1254 affects growth and survival skills of Atlantic croaker Micropogonias undulatus larvae Ian D. McCarthy1,2,*, Lee A. Fuiman1, Maria C. Alvarez1 1University of Texas at Austin, Marine Science Institute, 750 Channel View Drive, Port Aransas, Texas 78373, USA 2Present address: School of Ocean Sciences, University of Wales-Bangor, Menai Bridge, Askew Street, Anglesey LL59 5AB, Wales *Email: i.mccarthy@bangor.ac.uk ABSTRACT: The aim of this study was to evaluate the effect of environmentally realistic egg loadings of the polychlorinated biphenyl Aroclor 1254 on the subsequent growth and behavioural survival skills of Atlantic croaker Micropogonias undulatus larvae. Adult fish were given a dietary administration of 0 (control) or 0.4 (dosed) mg Aroclor 1254 kg-1 fish d-1 for 2 wk during the final stages of gonadal recrudescence. Fertilised eggs collected from control and dosed adults immediately after spawning contained 0 and 0.66 µg Aroclor 1254 g-1 egg, respectively. Growth rate (increase in total length) of dosed larvae was significantly lower than that of control larvae between 2 and 13 d post-hatching, with dosed larvae showing a 4 d delay in attaining the same size as control larvae. Behavioural assays were conducted to evaluate survival skills of larvae on Days 5 (complete yolk absorption), 9 (complete oil globule absorption), and 13 (larva wholly dependent on exogenous food sources) post-hatching. Survival skills examined were potential foraging rate (routine swimming speed and activity) and the response to a startle (transient vibratory stimulus) stimulus. Routine swimming speed and activity were similar for control and dosed larvae. There was a significant dose x age interaction in the responses of the control and dosed larvae to a vibratory stimulus. The percentage of control larvae responding to the stimulus, and their average and maximum burst speeds, increased with age. In contrast, no such age-related response was found in the dosed larvae. The results indicate that environmentally realistic body burdens of Aroclor 1254 transfer to the eggs and larvae, reducing their growth rates and impairing their startle responses, possibly making the larvae more susceptible to predation. KEY WORDS: Endocrine disrupting chemicals · Polychlorinated biphenyls · Atlantic croaker · Fish larvae · Swimming activity · Predator avoidance · Sublethal effects · Growth Full text in pdf format PreviousExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 252. Online publication date: April 30, 2003 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2003 Inter-Research.

Ecomorphology of Locomotion in Labrid Fishes

The Labridae is an ecologically diverse group of mostly reef associated marine fishes that swim primarily by oscillating their pectoral fins. To generate locomotor thrust, labrids employ the paired pectoral fins in motions that range from a fore-aft rowing stroke to a dorso-ventral flapping stroke. Species that emphasize one or the other behavior are expected to benefit from alternative fin shapes that maximize performance of their primary swimming behavior. We document the diversity of pectoral fin shape in 143 species of labrids from the Great Barrier Reef and the Caribbean. Pectoral fin aspect ratio ranged among species from 1.12 to 4.48 and showed a distribution with two peaks at about 2.0 and 3.0. Higher aspect ratio fins typically had a relatively long leading edge and were narrower distally. Body mass only explained 3% of the variation in fin aspect ratio in spite of four orders of magnitude range and an expectation that the advantages of high aspect ratio fins and flapping motion are greatest at large body sizes. Aspect ratio was correlated with the angle of attachment of the fin on the body (r = 0.65), indicating that the orientation of the pectoral girdle is rotated in high aspect ratio species to enable them to move their fin in a flapping motion. Field measures of routine swimming speed were made in 43 species from the Great Barrier Reef. Multiple regression revealed that fin aspect ratio explained 52% of the variation in size-corrected swimming speed, but the angle of attachment of the pectoral fin only explained an additional 2%. Labrid locomotor diversity appears to be related to a trade-off between efficiency of fast swimming and maneuverability in slow swimming species. Slow swimmers typically swim closer to the reef while fast swimmers dominate the water column and shallow, high-flow habitats. Planktivory was the most common trophic associate with high aspect ratio fins and fast swimming, apparently evolving six times.

Contrasts in the capacity and underlying mechanisms for compensatory growth in two pelagic marine fishes

The widespread capacity for teleost fishes to engage in compensatory growth suggests there are costs or trade-offs that constrain normal growth to sub-maximal rates. Some potential trade- offs include behavioral conflicts between foraging and avoiding predators, and physiological aspects of energy allocation between synthesis of new tissue and functional demands of metabolism and maintenance. We examined the capacity for compensation and some potential underlying mecha- nisms in juveniles of 2 northern Pacific fish species, walleye pollock Theragra chalcogramma and sablefish Anoplopoma fimbria. Fish were deprived of food for 2 to 3 wk, then returned to ad libitum rations. Growth rates were subsequently compared to those for continually fed fish for up to 16 wk, and potential trade-offs in behavior (food consumption, routine swimming speeds, and response to a predator) and physiology (indexed by critical swimming speeds) were examined during 3 time peri- ods: immediately after deprivation, after 4 wk of ad libitum rations, and after 9 wk. We distinguished between routine swimming speeds, which indicate volitional motor activity, and critical swimming speeds, which estimate physiological capacity by forcing fish to swim to exhaustion against an increasing current. Previously deprived walleye pollock exhibited a clear, sustained capacity for accelerated growth, allowing them to quickly catch up in size to continually fed fish. Sablefish, how- ever, exhibited only a minor level of growth compensation. Underlying mechanisms of compensatory growth also differed between the 2 species. Previously deprived walleye pollock increased food con- sumption to levels 3 to 4× greater than those of control fish and reduced energy expenditure by low- ering routine swimming speeds. Compensating sablefish did not differ from control fish in consump- tion rates or routine swimming, but had lower critical swimming speeds than control fish, suggesting a trade-off in energy allocation. Responses to a simulated predator threat did not differ between pre- viously deprived and continually fed fish of either species. The experimental results are suggestive of different mechanisms, behaviorally based for walleye pollock and physiologically based for sablefish, associated with accelerated growth. The differences between the 2 species in integrated processes of growth, behavior, and physiology are likely to be a function of their contrasting life history strategies and different baseline growth rates.

Erratum Ontongeny of routine swimming speed and startle responses in red drum, with a comparison of responses to acoustic and visual stimuli

Erratum Ontongeny of routine swimming speed and startle responses in red drum, with a comparison of responses to acoustic and visual stimuli

The Effects of Hypoxia on Three Sympatric Shark Species: Physiological and Behavioral Responses

Behavioral and physiological responses to hypoxia were examined in three sympatric species of sharks: bonnethead shark, Sphyrna tiburo, blacknose shark, Carcharhinus acronotus, and Florida smoothhound shark, Mustelus norrisi, using closed system respirometry. Sharks were exposed to normoxic and three levels of hypoxic conditions. Under normoxic conditions (5.5–6.4 mg l −1 ), shark routine swimming speed averaged 25.5 and 31.0 cm s −1 for obligate ram-ventilating S. tiburo and C. acronotus respectively, and 25.0 cm s −1 for buccal-ventilating M. norrisi. Routine oxygen consumption averaged about 234.6 mg O2 kg −1 h −1 for S. tiburo, 437.2 mg O2 kg −1 h −1 for C. acronotus, and 161.4 mg O2 kg −1 h −1 for M. norrisi. For ram-ventilating sharks, mouth gape averaged ∼1.0 cm whereas M. norrisi gillbeats averaged 56.0 beats min −1 . Swimming speeds, mouth gape, and oxygen consumption rate of S. tiburo and C. acronotus increased to a maximum of 37–39 cm s −1 , 2.5–3.0 cm, and 496 and 599 mg O2 kg −1 h −1 under hypoxic conditions (2.5–3.4 mg l −1 ), respectively. M. norrisi decreased swimming speeds to 16 cm s −1 and oxygen consumption rate remained similar. Results support the hypothesis that obligate ram-ventilating sharks respond to hypoxia by increasing swimming speed and mouth gape while buccal-ventilating smoothhound sharks reduce activity.

Swimming Speed and Metabolic Rate during Routine Swimming and Simulated Diel Vertical Migration of Sergestes similis in the Laboratory

Swimming Speed and Metabolic Rate during Routine Swimming and Simulated Diel Vertical Migration of Sergestes similis in the Laboratory1 David L. Cowles Abstract Sergestes similis (Hansen, 1903) is a common mesopelagic vertically migrating shrimp common in the temperate and subarctic North Pacific Ocean. The species is a diel vertical migrator, although it remains primarily above the oxygen minimum layer in regions such as off California where the layer is well developed. This shipboard study with a computer-controlled swim tunnel provided the first continuous examination of this species' swimming behavior and metabolism over a 24-hr cycle. Sergestes similis swam at a routine speed of around 4.4 to 4.95 cm sec-1. Burst speeds ranged from 14 to >20 cm sec-1. Swimming speeds during the day, at low temperatures simulating those at daytime depths, were similar to those at night at the higher temperatures characteristic of the surface. Night metabolic rates were higher than in the day, especially during the early night when most feeding activity may take place. Swimming speeds during times of simulated vertical migration averaged slightly faster than those of routine day or night swimming, averaging 6.2 cm sec-1 during the time of upward migration and 5.4 cm sec-1 during simulated downward migration, but the difference was not significant. Downward migration is not accomplished by passive sinking. Calculations based on observed swimming activities and metabolic rates indicate that vertical migration confers a clear metabolic energy savings to S. similis over remaining resident in surface waters, though this result may not be applicable to other vertical migrators and is likely moderated by decreased feeding opportunities at depth. Diel Vertical Migration is a widespread phenomenon among midwater species, the adaptive value of which has generated considerable discussion since discovery of the phenomenon. Postulated adaptive values have included predator avoidance, optimal foraging strategies, horizontal dispersal, growth and fecundity effects, metabolic advantages of changes in temperature, niche segregation, avoidance of photo-damage, group selection effects, and various combinations of these (Kerfoot 1970, 1985, Lampert 1989, 1993, Bevelhimer and Adams 1993, Loose and Dawidowicz 1994). Most of these hypotheses can be grouped into two major categories: that vertical migration confers some sort of metabolic advantage, or that it serves to reduce mortality by some mechanism such as predator avoidance (Lampert 1993). Sergestes similis (Hansen, 1903) is a mesopelagic vertically migrating penaeid shrimp found in abundance along the North Pacific coast from Japan to the Gulf of California, off Chile, and in the eastern South Atlantic (Butler 1980, Farfante and Kensley 1997). It inhabits primarily the region above the oxygen minimum layer (Figure 1). Daytime depths for the species off the Oregon and California coasts, where it is one of the most abundant midwater micronektonic species (Barham 1956, Genthe 1969, Pearcy and Forss 1969, Omori 1979), range from 200 to 650 m, and nighttime depths range from 50 to 200 m (Pearcy and Forss 1966, Omori and [End Page 215] Gluck 1979, Schlining et al. 1997). Eighty percent of the population can be found between 10 and 400 m depths off California (Childress 1975). Click for larger view View full resolution Figure 1. Depth distribution of Sergestes similis off California and Oregon, with vertical profiles of temperature and oxygen level. Error bars depict the day and night depth distributions reported in the literature. Solid bars indicate the depth range in which 80% of the population is found; dashed lines indicate the full reported depth range. See text for references. Temperature and oxygen profiles are from 32.05° N, 120.65° W in Rhines (1994). Depth distributions were extracted from Pearcy and Forss (1966), Omori and Gluck (1979), Schlining et al. (1997), and Childress (1975). As with most mesopelagic species, little is known about vertical migration in S. similis other than the range of depths in which it is found during the day and night. Information is scant, for example, about its behavior or activity levels at daytime and nighttime depths, on the costs and benefits of vertical migration to the species, or even whether downward migration is accomplished by active swimming or by passive sinking. Recent in situ studies of the species from a remotely...

Effects of feeding ration on larval swimming speed and responsiveness to predator attacks: implications for cohort survival

We conducted laboratory experiments to examine the effects of feeding ration on the routine swimming speed of larval striped bass (Morone saxatilis) and their responsiveness to simulated-predator attacks. Striped bass were reared in low (7 prey·L-1), medium (354 prey·L-1), or high (740 prey·L-1) prey treatments from age 4 to 14 days posthatch. Larvae reared in the low-prey treatment had slower routine swimming speeds and shorter reactive distances and were less responsive to simulated-predator attacks. These differences were most pronounced after age 10 and appeared to be an effect of deteriorating larval condition rather than an effect of size. Simulation models were constructed for two potential fish predators, Alosa aestivalis and Pomoxis nigromaculatus, to examine how variation in growth rate, swimming speed, and responsiveness to predator attacks might influence mortality rate. Our simulations predicted that cohort mortality rate would decrease with increasing larval growth rates, even though faster routine swimming speed and growth rate increased encounter rates with predators. The influence of larval growth rate and responsiveness on mortality rate varied between the two predators, but cohorts experiencing no growth always had the greatest mortality rate.

Ontogeny of routine swimming speed and startle responses in red drum, with a comparison of responses to acoustic and visual stimuli

Routine swimming speed of larval red drum Sciaenops ocellatus increased throughout development but most rapidly for larvae >10 mm LT. Red drum of all sizes swam faster than predicted by published summary equations based on other species, possibly due to more advanced development at a given length. Frequency and magnitude of startle responses increased over the larval period for both types of stimuli with most of the improvement taking place before larvae reached 8 mm LT. Time to response for an acoustic and visual stimulus decreased early in the larval period but levelled off after 10 mm LT. Response distance and response speed for both stimuli generally increased throughout the larval period, but response duration remained constant. Visually stimulated responses were generally longer in duration and distance covered than acoustically stimulated responses, while mean response speeds were similar.

Ontogeny of routine swimming speed and startle responses in red drum, with a comparison of responses to acoustic and visual stimuli

Routine swimming speed of larval red drum Sciaenops ocellatus increased throughout development but most rapidly for larvae >10 mm LT. Red drum of all sizes swam faster than predicted by published summary equations based on other species, possibly due to more advanced development at a given length. Frequency and magnitude of startle responses increased over the larval period for both types of stimuli with most of the improvement taking place before larvae reached 8 mm LT. Time to response for an acoustic and visual stimulus decreased early in the larval period but levelled off after 10 mm LT. Response distance and response speed for both stimuli generally increased throughout the larval period, but response duration remained constant. Visually stimulated responses were generally longer in duration and distance covered than acoustically stimulated responses, while mean response speeds were similar.

Metabolic trade-off between locomotion and detoxification for maintenance of blood chemistry and growth parameters by rainbow trout ( Oncorhynchus mykiss) during chronic dietary exposure to copper

The aim of this study was to obtain a holistic view of the sublethal toxic responses, and compensations, of fish exposed to Cu in the diet. Rainbow trout were fed to appetite on either a Cu-loaded diet (500 mg Cu kg −1 dw) or a control diet (11.9 mg Cu kg −1 dw) for 3 months. Nutritional performance, blood and muscle chemistry, histology, respiration, and swimming behaviour were measured. Copper concentration in intestine and liver of exposed fish was 16 and 2.5 times greater than in controls respectively, confirming oral Cu exposure. [Cu] remained low in the gills of fish irrespective of Cu treatment (<0.096 μmol g −1 dw). Hepatic and intestinal metallothionien levels increased 8- and 1.5-fold, respectively, in Cu-treated fish compared to controls. Growth rate, appetite, food conversion ratios, carcass composition, oxygen consumption and ventilation rate in exposed fish were not different from controls. There were no treatment related changes in serum chemistry (glucose, triglycerides, protein, Na, K, Hb) or the mineral composition of skeletal muscle (Ca, Mg, Zn, Na, or K). However, quantitative histology showed a 9% increase in gill secondary lamellae length, together with lipid depletion in the livers of copper treated fish compared to controls. Routine swimming activity was affected significantly by oral Cu exposure. Time spent swimming was 35% lower in Cu-exposed fish after 3 months, while total distance moved was reduced by only 21% because mean swimming speed was 12% higher in contaminated fish. Maximum speeds attained by exposed fish were not different compared to controls. Exposed fish lowered activity overall by decreasing time spent swimming at low (1–17 cm s −1) and medium speeds (17–40 cm s −1), whilst increasing proportionately time spent fast swimming (40–58 cm s −1). These results are discussed in terms of sub-lethal oral Cu affecting the partitioning of energy utilisation between locomotion and maintenance metabolism by trout in a physiological drive towards invariant growth rates.

Early development and allometric growth patterns in Siberian sturgeon and their ecological significance

Early development of Siberian sturgeon Acipenser baeri was divided into two different phases, the prelarval stage between hatching (10·4–11·1 mm LT) and first feeding (19·6–21·0 mm LT), and the larval stage between the initiation of external feeding and metamorphosis (28·6–32·4 mm LT). Morphogenesis and differentiation were more intense during the prelarval than larval and early juvenile stages; the prelarval period was characterized by the replacement of embryonic adaptations and functions by definitive ones, such as branchial respiration, exogenous feeding, and active swimming. The positive allometry of the head for feeding, sensorial and respiratory functions (inflexion point at 20·0 mm LT), and the tail for reducing costs of transport, routine swimming and escape reactions from predators (inflexion point at 20·2 mm LT) confirmed the hypothesis that growth patterns of early life stages closely match specific needs.

Behavioural and metabolic effects of chronic exposure to sublethal aluminum in acidic soft water in juvenile rainbow trout (Oncorhynchus mykiss)

Triplicate groups of 15 softwater-acclimated juvenile rainbow trout (Oncorhynchus mykiss) were randomly allocated to one of three treatments: pH 6.5 with no aluminum, pH 5.2 with no aluminum, and pH 5.2 with 30 µg labile aluminum·L-1. The aluminum dose was sublethal and continued for 34 days. Treatment effects on swimming behaviour, metabolism, feeding, food conversion efficiency, and blood parameters were determined. Fish exposed to aluminum displayed hypoactivity that was statistically distinct from both control groups from day 1 onwards. Exposure to acid alone elicited no behavioural effects. There were no significant differences in metabolic rates between the treatment groups. Feeding rates of the fish exposed to aluminum became depressed, reaching a minimum on day 15, and gradually recovered thereafter, but never to the preexposure levels. Swimming behaviour was a more sensitive index of exposure to aluminum than feeding. Fish exposed to aluminum had significantly fewer red blood cells and lower haematocrit than the controls, indicating haemodilution. Aluminum is known to act as a respiratory toxicant, restricting aerobic scope. In addition, these data suggest that fish respond to aluminum exposure by reducing metabolically costly activities such as routine swimming behaviour to allow for the increased maintenance costs associated with acclimation and damage repair.