Compensatory growth of juvenile brown flounder Paralichthys olivaceus (Temminck & Schlegel) following thermal manipulation

The compensatory growth of juvenile brown flounder Paralichthys olivaceus (body mass c. 12 g) following different thermal exposure was investigated. Fish were exposed to one of the five temperatures: 8·5 ( T _8·5), 13·0 ( T _13·0), 17·5 ( T _17·5), 22·0 ( T _22·0) and 26·5° C ( T _26·5) for 10 days and fish grew best at 22·0° C. Then the water temperature in all treatments was equably adjusted to 22·0° C over 3 days. At the end of the following 30 days after temperature adjustment, there were no significant differences between body masses of fish in the different treatments (wet body mass at the end of the experiment ranged from 22·13 to 24·56 g). Results indicated that the juvenile P. olivaceus achieved complete compensatory growth. Analysis of the dynamics of the feeding rates and feed conversion efficiencies indicated that compensatory growth of the fish experienced low temperature ( T _8·5, T _13·5 and T _17·5) or high temperature ( T _26·5) exposure was mainly dependent on increasing feed intake (hyperphagia) and possibly by improvement in feed conversion efficiency. The moisture content was not affected by different temperature exposure significantly. The lipid and energy content of juvenile P. olivaceus in T _8·5, however, were significantly lower than other treatment. Results of the current study indicate that a short period of low or high temperature exposure may not affect annual growth, but may affect lipid and energy deposition.     

Seasonal variability in growth of larval Japanese anchovy Engraulis japonicus driven by fluctuations in sea temperature in the Kii Channel, Japan

Seasonal variability in the growth of larval Japanese anchovy Engraulis japonicus was examined through otolith microstructure analysis based on the samples collected from the northern side (inner area, IA) and the southern side (outer area, OA) of the Kii Channel from April 2006 to March 2007. Growth trajectories (otolith backcalculated mean standard length of 5 day intervals from 5 days after hatch to 24 days) as well as the most recent 5 day mean growth rate of larvae before capture ( G ₅) differed among months. Growth trajectories showed the same pattern as G ₅. In IA, mean ± s.d. G ₅ ranged from 0·31 ± 0·04 mm day⁻¹ (January) to 0·73 ± 0·06 mm day⁻¹ (October). In OA, mean ± s.d. G ₅ ranged from 0·36 ± 0·05 mm day⁻¹ (January) to 0·79 ± 0·11 mm day⁻¹ (August). G ₅ values declined from November to January and then started to increase. In general, the seasonal patterns of growth were similar between IA and OA, and a clear seasonal pattern in growth was identified. When the relationships among larval growth rate, sea temperature, zooplankton density and larval density were examined, growth rate was positively related with sea temperature in both areas and not related with the other factors. The similar pattern in growth observed between IA and OA was probably due to the low spatial variability in sea temperature compared to its seasonal variability.     

Growth, diet and metabolism of common wolf–fish in the North Sea, a fast–growing population

The von Bertalanffy growth parameters for common wolf–fish Anarhichas lupus in the North Sea were: male: L ∞=111·2 cm, t ₀=–0·43 and K =0·12; and female: L ∞=115·1 cm, t ₀=–0·39 and K =0·11, making this the fastest growing stock reported. Resting metabolic rates (RMR±S.E.) and maximum metabolic rates (MMR±S.E.) for six adult common wolf–fish (mean weight, 1·39 kg) at 5° C were 12·18±1·6 mg O₂ kg^–1 h^–1 and 70·65±7·63 mg O₂ kg^–1 h^–1 respectively, and at 10° C were 25·43±1·31 mg O₂ kg^–1 h^–1 and 113·84±16·26 mg O₂ kg^–1 h^–1. Absolute metabolic scope was 53% greater at 10° C than at 5° C. The diet was dominated by Decapoda (39% overall by relative occurrence), Bivalvia (20%) and Gastropoda (12%). Sea urchins, typically of low energy value, occupied only 7% of the diet. The fast growth probably resulted from summer temperatures approximating to the optimum for food processing and growth, but may have been influenced by diet, and reduced competition following high fishing intensity.     

Seasonal differences in routine oxygen consumption rates of the bonnethead shark

Routine oxygen consumption rates of bonnethead sharks, Sphyrna tiburo , increased from 141·3±29·7 mg O₂ kg⁻¹ h⁻¹ during autumn to 218·6±64·2 mg O₂ kg⁻¹ h⁻¹ during spring, and 329·7±38·3 mg O₂ kg⁻¹ h⁻¹ during summer. The rate of routine oxygen consumption increased over the entire seasonal temperature range (20–30° C) at a Q ₁₀=2·34.     

Some morphometric and biochemical features of ready-to-migrate silver and pre-migratory yellow stages of the shortfin eel of south-eastern Australian waters

The mean total length ( L _T), mass and age of ready to migrate female silver shortfin eels Anguilla australis from the Hopkins River estuary and the mouth of the Merri River in south-eastern Australia, were 83·2 ± 1·2 cm, 1051 ± 51 g, and 17·2 ± 1·79 years, respectively. The eye index ( I _E) of the silver shortfin eels was < 5·2 (mean 7·64 ± 0·29) and differed significantly from that of the yellow shortfin eels collected from two other sites. The I _E increased with L _T (mm) and was related by log I _E= 2·656 log L _T6·925. The per cent moisture, protein and ash content of the liver of silver shortfin eels was significantly lower than in yellow shortfin eels, but lipid content was significantly higher in the former (35·5 ± 2·0%). The mean mass μg mg lipid ⁻) of saturates (230·4 ± 2·6 v . 181·7 ±2·6), monoenes (367·4 ± 6·3 v . 290·8 ± 8·9) and PUFA (177·3 ± 5·3 v . 159·7 ± 4·6) in muscle was significantly higher, and the great majority of individual fatty acids was found also in higher quantities in silver shortfin eels. In the liver, the PUFA found in the highest quantity was 22:6n-3, except in shortfin eels from Hopkins River estuary, and the amount of 18:2n-6 in the liver of silver shortfin eels was significantly higher than that in yellow shortfin eels but the reverse was true of 20:4n-6. In both muscle and liver tissues the saturate 16:0 and the monoene 18:ln-9 collectively accounted for >50% of all the fatty acids in the lipid.     

Polyaluminum chloride-enhanced concentration efficiency of poliovirus and f2 phage from sewage water

Aims:  To enhance the recovery of f₂ bacteriophage and poliovirus by an established method based on the adsorption to and elution from positively-charged Al(OH)₃-treated silica gel.
Methods and Results:  Polyaluminum Chloride (PAC) was added to water samples to neutralize the negatively charged materials, which can reduce virus recovery by providing a competing adsorption mode on the media surface. Using this improved process (PAC 30 mg l⁻¹, pH 6·5, temperature 20∼30°C), the recoveries of Poliovirus I and f₂ from small-volume sewage (100 ml) were 110·76 ± 36·0% and 92·06 ± 8·65%, respectively ( P  < 0·05 vs. traditional methods). Recovery from a 20-L volume of sewage averaged 85·65 ± 4·43% for f₂ and 88·73 ± 9·76% for poliovirus, significantly higher than the recoveries in the traditional methods ( P  < 0·05).
Conclusions:  PAC could enhance concentration efficiency of poliovirus and f₂ phage from sewage water.
Significance and Impact of the Study:  This method should significantly improve the recovery of viruses from sewage.     

Physiological impact of sea lice on swimming performance of Atlantic salmon

Atlantic salmon Salmo salar were infected with two levels of sea lice Lepeophtheirus salmonis (0·13 ± 0·02 and 0·02 ± 0·00 sea lice g⁻¹). Once sea lice became adults, the ventral aorta of each fish was fitted with a Doppler cuff to measure cardiac output ( ̇ ), heart rate ( f _H) and stroke volume ( V _S) during swimming. Critical swimming speeds ( U _crit) of fish with higher sea lice numbers [2·1 ± 0·1 BL (body lengths) s⁻¹] were significantly lower ( P  < 0·05) than fish with lower numbers (2·4 ± 0·1 BL s⁻¹) and controls (sham infected, 2·6 ± 0·1 BL s⁻¹). After swimming, chloride levels in fish with higher sea lice numbers (184·4 ± 11·3 mmol l⁻¹) increased significantly (54%) from levels at rest and were significantly higher than fish with fewer lice (142·0 ± 3·7 mmol l⁻¹) or control fish (159·5 ± 3·5 mmol l⁻¹). The f _H of fish with more lice was 9% slower than the other two groups at U _crit. This decrease resulted in ̇ not increasing from resting levels. Sublethal infection by sea lice compromised the overall fitness of Atlantic salmon. The level of sea lice infection used in the present study was lower than has previously been reported to be detrimental to wild Atlantic salmon.     

Effects on acid-base balance, methaemoglobinemia and nitrogen excretion of European eel after exposure to elevated ambient nitrite

Haemoglobin, methaemoglobin, blood nitrite concentration and acid-base balance were measured in European eel Anguilla anguilla following exposure to 0 (control), 0·142, 0·356, 0·751 and l·549 mM nitrite in fresh water for 24 h. Blood GOT (glutamate oxaloacetate transaminase) and GPT (glutamate pyruvate transaminase) activities and whole animal ammonia-N and urea-N excretions were also measured. Blood nitrite, methaemoglobin, PO ₂ (oxygen partial pressure), GOT, and whole animal ammonia-N excretion and urea-N excretion increased directly with increasing ambient nitrite concentrations, whereas blood pH, PCO ₂, and HCO⁻₃ were inversely related to ambient nitrite concentration. An accumulation of nitrite in the blood of A. anguilla following 24 h exposure to elevated ambient nitrite as low as 0·751 mM increased its blood methaemoglobin, PO ₂, GOT and nitrogen excretion, but decreased its PCO ₂ (carbon dioxide partial pressure), HCO⁻₃ and functional haemoglobin.     

The use of a surface adhesion immunofluorescent (SAIF) method for the rapid detection of Yersinia enterocolitica serotype O:3 in meat

This study examined the attachment kinetics of Yersinia enterocolitica serotype O:3 to determine the optimum conditions for its isolation from meat enrichment systems using a novel surface adhesion technique. Minced beef was inoculated with Y. enterocolitica at an initial level of 10 cfu g⁻¹ and incubated at 25 °C in an enrichment broth. Yersinia was recovered from enriched samples on polycarbonate membranes by surface adhesion and enumerated using immunofluorescence microscopy. The surface adhesion immunofluorescence technique (SAIF) had a minimum detection limit of approximately 4·0–4·5 log₁₀ cfu ml⁻¹ and provided good correlation between the estimation of the numbers of Yersinia in the enrichment broth derived from plate counts on Yersinia Selective agar (CIN) and those determined by SAIF ( r ² ₌ 0·94; rsd ₌ ± 0·21). A derived regression equation of the SAIF count vs plate counts was used to predict Y. enterocolitica numbers in spiked meat samples stored at 0 °C for up to 20 d. The numbers as predicted by the SAIF method showed good correlation with counts derived by plating techniques ( r ² ₌ 0·78; rsd ₌ ± 0·42). The application of the SAIF technique for the rapid detection of Y. enterocolitica serotype O:3 from meat is discussed.     

31P NMR Relaxation Does Not Affect the Quantitation of Changes in Phosphocreatine, Inorganic Phosphate, and ATP Measured In Vivo During Complete Ischemia in Swine Brain

Abstract: Ischemia-induced changes in ³¹P NMR relaxation were examined in 16 piglets. NMR spectra were acquired under control conditions and during complete cerebral ischemia induced via cardiac arrest. Changes in T ₁ were assessed directly in six animals during control conditions and after 30–45 min of complete ischemia when changes in brain P₁ levels had reached a plateau. The T ₁ for P₁ did not change, i.e., 2.3 ± 0.5 s during control conditions versus 2.4 ± 1.0 s during ischemia. To evaluate phosphocreatine and ATP, two types of spectra, with a long (25-s) or short (1-s) interpulse delay time, were collected during the first 10 min of ischemia (n = 10). Both types of spectra showed the same time course of changes in phosphocreatine and ATP levels, implying that the T ₁ relaxation times do not change during ischemia. There were no changes in the linewidths of phosphocreatine, ATP, or P₁ during ischemia, implying that the T *₂ values remain constant. Our results suggest that the ³¹P T ₁ and T *₂ for phosphocreatine, P_i, and ATP do not change during ischemia, and therefore changes in ³¹P NMR peak intensity accurately reflect changes in metabolite concentrations.     

Cyclic feeding and subsequent compensatory growth do not significantly impact standard metabolic rate or critical swimming speed in rainbow trout

Standard metabolic rate ( R _s) and critical swimming speed ( U _crit) were used to assess the aspects of physiological status (stamina) of rainbow trout Oncorhynchus mykiss . Fish were fed either 1·5% body mass daily, 1·5% body mass cyclically (3 weeks of food deprivation followed by 3 weeks of refeeding), a ration based on Stauffer's formula (a maximum temperature-specific ration level) daily or on Stauffer's ration cyclically for 18 weeks. It was hypothesized that if cyclic feeding had no impact on the status of the fish, R _s and U _crit would not cycle with the feeding regime. This hypothesis was supported. No significant difference was found between the mean mass and the fork length of the four groups at the end of the experiment ( P > 0·05). Feeding had no effect on changes in R _s among the four groups, which were significantly different throughout the experiment ( P ≤ 0·05). No significant difference in U _crit was found ( P > 0·05) until at week 12 between groups fed 1·5% body mass ration cyclically and Stauffer's ration daily ( P ≤ 0·05). For groups fed a 1·5% body mass ration cyclically and daily, significant differences occurred at week 15 ( P ≤ 0·05) but no significant difference was found by week 18 ( P > 0·05), suggesting that cyclic feeding does not affect the aspects of physiological status (stamina) of the fish.     

The immunoglobulin of the brown trout, Salmo trutta and its concentration in the serum of antigen-stimulated and non-stimulated fish

Immunoglobulin production in the primary and secondary immune response of brown trout to keyhole limpet haemocyanin has been investigated including the effect of dose size, route and number of injections, and the use of adjuvant. Antibody activity was found in the first fraction from Sephadex G200 and in the second from Sepharose 6B. Trout immunoglobulin had β₂—Γ₁ electrophoretic mobility, and S_app of 16·7 and an approximate molecular weight of 670 000 daltons. It was sensitive to dithiothreitol and stable at 56°C for 30 min. Immunoglobulin concentrations were measured by single radial immunodiffusion with a specific rabbit antiserum. Sera from non-injected trout had a mean immunoglobulin level of 7·3 ± 0·3 mg ml⁻¹ which accounted for 10% of the total serum protein. Phosphate buffered saline-injected controls contained 6·7 ± 0·2. In fish given a single injection the mean concentration ranged from 7·5 to 12·9 and in those given more than one injection from 12·6 to 16·8. The use of adjuvant resulted in higher immunoglobulin concentrations. Neither dose nor route had any significant effect on the primary response. However, in the secondary response the intramuscular route resulted in significantly increased immunoglobulin production.     

Effects of temperature, body size and feeding on rates of metabolism in young‐of‐the‐year haddock

The mean rate of oxygen consumption (routine respiration rate, R _R, mg O₂ fish⁻¹ h⁻¹), measured for individual or small groups of haddock Melanogrammus aeglefinus (3–12 cm standard length, L _S) maintained for 5 days within flow‐through respiratory chambers at four different temperatures, increased with increasing dry mass ( M _D). The relationship between R _R and M _D was allometric ( R _R = α  M ^b ) with b values of 0·631, 0·606, 0·655 and 0·650 at 5·0, 8·0, 12·0 and 15·0° C, respectively. The effect of temperature ( T ) and M _D on mean R _R was described by     indicating a Q ₁₀ of 2·27 between 5 and 15° C. Juvenile haddock routine metabolic scope, calculated as the ratio of the mean of highest and lowest deciles of R _R measured in each chamber, significantly decreased with temperature such that the routine scope at 15° C was half that at 5° C. The cost of feeding ( R _SDA) was c . 3% of consumed food energy, a value half that found for larger gadoid juveniles and adults.     

Differences in size and growth rates of male and female migrating Japanese eels in Pearl River, China

The Sr/Ca ratios in otoliths of silver Japanese eels Anguilla japonica , in Pearl River, China, indicated that both sexes did not stay in brackish water and grew in fresh water from the glass eel stage until spawning migration. This did not support the hypothesis that females tended to distribute upstream and males might be restricted to estuaries. The back-calculated total length of males at glass eel stage was not significantly different from that of females, indicating that the hypothesis that small glass eels became males and larger ones became females may not be true. The mean (±S.D.) age and total length of males at migration were 6·4±1·6 years and 48·3±4·5 cm, which were significantly smaller than for females, 8·3±1·6 years and 61·4±4·1 cm. The age of migration was related inversely to growth rate for both sexes. Growth parameters of the von Bertalanffy growth equation were K =0·21 cm year°1, L _∞=55·7 cm and t _o=-0·55 year for males and K =0·14 cm year⁻¹, L _∞=77·5 cm and t _o=-0·60 year for females. The difference in asymptotic length ( L _∞) between males and females may be because females postpone migration to achieve larger size for maximizing reproductive success.     

Comparison of field-based and indirect estimates of daily food consumption in larval perch and zander

Since bioenergetics models for 0+ fish have seldom been validated by field consumption estimates, field-based and indirectly estimated daily food rations were compared in larval perch Perca fluviatilis and zander Stizostedion lucioperca. Field-based estimates were calculated with linear and exponential evacuation rates based on gut fullness data during a 24-h cycle, with hourly field samplings instead of the normally recommended 3-h intervals. Indirect calculations used bioenergetics modelling with variable activity multipliers ( A ). Field-based estimates of daily rations ranged between 0·21 and 0·27 g g⁻¹ day⁻¹ in perch (mean L _T 13·1 mm) and 0·31–0·40 g g⁻¹ day⁻¹ in zander (mean L _T 10·6 mm). The higher values were calculated by using the exponential model. Daily rations calculated by bioenergetics modelling with A = 1 were only slightly higher than direct estimates in both species. However, if A values >1 were used, calculated daily rations were substantially higher than direct estimates. Estimates of daily ration based only on every third value ranged between 41 and 72% compared with 1-h intervals, mainly because of lower estimates of evacuation rate.     

Poikilothermic traits and thermoregulation in the Afrotropical social subterranean Mashona mole-rat (Cryptomys hottentotus darlingi) (Rodentia: Bathyergidae)

When acclaimated for two months at 26 C the social Mashona mole-rat Cryptomys hottentotus darlingi (±S.D.) resting metabolic rate (RMR) of 0·98±0.·14cm²O₂g _-1 h_-1 ( n =21), within a thermal neutral zone (TNZ) of 28 31·5 C ambient temperature (Ta). The body temperature (Tb) of the mole-rat is very low. 33·3±0·5 C, and remained stable between 25 31·5 C ( n =28). Above 33 C. Tb increased to a mean of 34·±0· C (n=28) (Ta range 33 39 C). Below Ta 25 C. Tb showed strong poikilothermic tendencies, with Tb dropping to a mean of 26·8±1·16 C. whereas above Ta25 C. Tb varied in a typically endothermic pattern. The conductance is high 0·19±0·03 cm² O_2g¹ C ¹ (n=28) at the lower limit of thermoneutrality. The mean RMR at 18 C (the lowest Ta tested) was 2·63 ± 0·55 cm³ O₂g ¹ h ¹ (n=7) which is 2·6 times that of the resting metabolic rate in the TNZ.     

Plasma non-esterified fatty acid profiles in wild Atlantic salmon during their freshwater migration and spawning

Total plasma non-esterified fatty acid (NEFA) levels increased significantly in adult Atlantic salmon during the first months of their upstream migration and spawning in the Exploits River, Newfoundland, Canada. The highest levels occurred in May and were 5467±270·43 nmol ml⁻¹ for females and 4617±334·70 nmol ml⁻¹ for males. Significantly higher levels were maintained by females compared with males for most of the upstream migration. Between August and October, total plasma NEFA levels declined by 61% in females but only 23% in males. The decline in plasma monounsaturated and polyunsaturated fatty acid levels accounted for 74% of the loss of NEFAs in females. Specific plasma NEFAs such as 16: 0 (palmitic), 16: 1 (palmitoleic), 18: 1n9 (oleic) and 20: 5n3 (eicosapentaenoic acid) differed significantly between males and females during migration and spawning. The mean gonadosomatic index ( I _G) values of females in May and just prior to spawning were 0·37±0·01 and 10·25±0·32, respectively. The rapid decline in the plasma NEFA content of females coincided with the largest increase in their I _G (1·85±0·02–10·25±0·32). Corresponding I _G values for males were 0·34±0·01 in May and 3·33±0·78 prior to spawning. Plasma NEFA levels of spent salmon did not differ between sexes and were significantly lower than those of salmon preparing to spawn.     

Swimming performance, oxygen consumption and excess post-exercise oxygen consumption in adult transgenic and ocean-ranched coho salmon

Routine oxygen consumption ( M o ₂) was 35% higher in 1 day starved and 21% higher in 4 day starved adult transgenic coho salmon Oncorhynchus kisutch relative to end of migration ocean-ranched coho salmon. Critical swimming speed ( U _crit) and M o ₂ at U _crit ( M o _2max) were significantly lower in 4 day starved transgenic coho salmon (1·25 BL s⁻¹; 8·79 mg O₂ kg⁻¹ min⁻¹) compared to ocean-ranched coho salmon (1·60 BL s⁻¹; 9·87 mg O₂ kg⁻¹ min⁻¹). Transgenic fish swam energetically less efficiently than ocean-ranched fish, as indicated by a poorer swimming economy at U _crit ( M o _2max     ). Although M o _2max was lower in transgenic coho salmon, the excess post-exercise oxygen consumption (EPOC) measured during the first 20 min of recovery was significantly larger in transgenic coho salmon (44·1 mg O₂ kg⁻¹) compared with ocean-ranched coho salmon (34·2 mg O₂ kg⁻¹), which had a faster rate of recovery.     

Early growth and juvenile population structure of lemon sharks Negaprion brevirostris in the Atol das Rocas Biological Reserve, off north‐east Brazil

Lemon sharks Negaprion brevirostris were sampled in the Atol das Rocas, a nursery area, on nine occasions from March 1999 to October 2003, during which 157 individuals were tagged and 35 were recaptured. The male : female sex ratio of captured individuals was 1 : 1·12. Mean ±  s . d . growth rates were 24·7 ± 3·4 cm year⁻¹ in total length ( L _T), 20·7 ± 3·2 cm year⁻¹ in fork length, and 19·5 ± 2·7 cm year⁻¹ in precaudal length. There was no significant difference in growth rates between males and females. Mean ±  s . d . increase in mass was 2565 ± 762 g year⁻¹. The von Bertalanffy growth parameters estimated by the Fabens method based on L _T were: k  = 0·077, L _∞ = 399·9 cm and t ₀ = −2·16. Despite the large variation of environmental conditions, particularly of tidal range and currents, and the lack of protective mangrove cover in the nursery area at Atol das Rocas, juvenile lemon sharks grew relatively faster than at other nurseries. Such rapid growth could be a response to abundant food availability or high risk of predation by adults that enter the nursery area.     

Countergradient variation in growth and food conversion efficiency of juvenile turbot

Growth performance of a high latitude (Norway) population of juvenile turbot Scophthalmus maximus , was superior to that of two other lower latitude populations (Scotland, France) especially at 18° and 22° C. Overall these results lend some support to the hypothesis of countergradient variation in growth. The Norwegian population had the highest estimated temperature optimum for growth ( T _opt.G, ±S.E.) (23·0±0·9°C) and food conversion efficiency ( T _opt.Ec) (17·5±0·3), followed by the French ( T _opt.G 21·1±1·0; T _opt.Ec, 16·7±0·1) population, whereas the Scottish population had the lowest optimum ( T _opt.G, 19·6±0·6; T _{opt Ec}, 16·5±0·1°C). These results have two major implications: firstly, for turbot culture, particularly in selection work focusing on growth performance; secondly, if countergradient variation in growth performance takes place within a species one cannot assume automatically that one set of physiological parameters, in this case growth-related parameters, is satisfactory to predict growth for a species throughout its range as different populations might show a difference in response towards different physiological parameters.