Growth in the crayfish Austropotamobius pallipes (Crustacea: Astacidae)

SUMMARY. The growth of Austropotamobius pallipes was studied in the River Ouse during 1976–78. Growth of mature crayfish (>2.5 cm carapace length) was followed by determining the relationship between the growth increment at moult and premoult carapace length, together with the frequency of moulting of different categories of crayfish. These data are supplemented by the recapture of marked individuals and the measurement of crayfish held in corves in the river. Growth was limited to the period May–October when water temperatures exceeded 10°C. Growth rates of male and female crayfish are similar until maturity is reached, thereafter males moult twice per year and the majority of females moult once. No crayfish in excess of 3.7 cm carapace length has been observed to moult more than once per year. Growth of juveniles (<2.5 cm carapace length) was estimated from size frequency distributions constructed from regularly taken samples. Growth rates of juveniles showed great variation both between and within year classes. In the hot dry summer of 1976, juveniles exhibited faster growth rates (instantaneous growth rates (G) for 0+ and 1 + crayfish were 0.029 and 0.013 mg mg⁻¹ day⁻¹. respectively) than in other years. Laboratory experiments on the effect of temperature on the growth rate of 0 + crayfish were undertaken; for crayfish at 15°C. G = 0.0138 (0–53 days) and at 10°C, G = 0.0003 (0–90 days). Crayfish held at 10°C failed to undergo a single successful moult. At 20°C crayfish exhibited exponential growth over the first 40 days, with G = 0.0189. declining thereafter to G = 0.012 (40–90 days).     

Thermal tolerance of a northern population of striped bass Morone saxatilis

Thermal tolerance of age 0+ year Shubenacadie River (Nova Scotia, Canada) striped bass Morone saxatilis juveniles (mean ± s . e . fork length, L _F, 19·2 ± 0·2 cm) acclimated in fresh water to six temperatures from 5 to 30° C was measured by both the incipient lethal technique (72 h assay), and the critical thermal method ( C _m). The lower incipient lethal temperature ranged from 2·4 to 11·3° C, and the upper incipient lethal temperature ( I _U) from 24·4 to 33·9° C. The area of thermal tolerance was 618° C². In a separate experiment, the I _U of large age 2+ year fish (34·4 ± 0·5 cm L _F) was 1·2 and 0·6° C lower ( P < 0·01) than smaller age 1+ year fish (21·8 ± 0·5 cm L _F) at acclimation temperatures of 16 and 23° C. Using the C _m, loss of equilibrium occurred at 27·4–37·7° C, loss of righting response at 28·1–38·4° C and onset of spasms at 28·5–38·8° C, depending on acclimation temperature. The linear regression slopes for these three responses were statistically similar (0·41; P > 0·05), but the intercepts differed (25·3, 26·0 and 26·5° C; P < 0·01). The thermal tolerance of this northern population appears to be broader than southern populations.     

Variation in routine metabolism of juvenile muskellunge: evidence for seasonal metabolic compensation in fishes

Metabolic rate of age 0 muskellunge Esox masquinongy ranged from 0·10 at 5° C to 0·24 mg O₂ g^-1 h^-1 at 25° C and was significantly higher in spring and autumn than during winter months at comparable water temperatures. Reduced metabolic rate in winter was consistent with the metabolic compensation hypothesis, implying that metabolism of muskellunge varies independently of acclimation temperature and gonadogenesis. Moreover, seasonal variation in metabolic rate has important implications for energy budget studies. Single-season estimates of esocid metabolism may be inadequate to describe annual energy requirements; the magnitude of errors will depend on the time of year metabolic rate was measured. As a result, it is suggested that seasonal variation in metabolic rate be incorporated into energy budget determinations for fishes.     

Effect of long-term and rapid cold hardening on the cold torpor temperature of an aphid

Abstract.  The effect of long-term (seasonal) acclimation and rapid cold hardening is investigated on the cold torpor temperature ( CT _min) of adult grain aphids, Sitobion avenae, reared at 20 or 10 °C for more than 6 months before experimentation. Rapid cold hardening is induced by exposing aphids reared at 20 to 0 °C for 3 h and aphids reared at 10 to 0 °C for 30 min (acclimation regimes previously found to induce maximum rapid cold hardening). The effect of cooling aphids from the same rearing regimes from 10 to −10 °C at 1, 0.5 and 0.1 °C min⁻¹ is also investigated. In the 20 °C acclimated population, rapid cold hardening and cooling at 0.1 °C min⁻¹ both produce a significant decrease in CT _min from 1.5 ± 0.3 to –0.9 ± 0.3 and –1.3 ± 0.3 °C, respectively. Rapid cold hardening also results in a significant reduction in CT _min of the population reared at 10 °C from 0.8 ± 0.1 to –0.9 ± 0.2 °C. However, none of the cooling regimes tested reduces the CT _min of the winter-acclimated (10 °C) population. The present study demonstrates that rapid cold-hardening induced during the cooling phase of natural diurnal temperature cycles could lower the movement threshold of S. avenae , allowing insects to move and continue feeding at lower temperatures than would otherwise be possible.     

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.     

Physiological studies on pea tendrils. XII. Effects of temperature on contact coiling and uncoiling

When excised tendrils of pea ( Pisum sativum L. cv. Alaska 2B) are mechanically perturbed and allowed to coil at different constant temperatures, the greatest amount of coiling occurs between 27°C and 33°C. Coiling of tendrils continues for about 2 h after mechanical perturbation at which time uncoiling usually begins. The temperature at which the rate of uncoiling is greatest appears to be influenced, at least in part, by the temperature at which the tendrils coiled. For example, when tendrils coil at 20°C their rate of uncoiling at 20°C is less than if they had coiled at 23°C. Estimated activation energies for the uncoiling process are greater than for coiling, with 35 J/mol × s and 97 J/mol × s for uncoiling in the temperature ranges 18°C to 23°C and 10°C to 18°C, respectively. The estimated activation energy for coiling is 5.4 J/mol × s. It is suggested that the process of tendril uncoiling, as well as tendril coiling, might be an active, energy requiring process.
When mechanically perturbed tendrils are placed in the cold (5°C) they do not coil. But this interruption of the coiling process with a cold (5°C) treatment, either immediately after mechanical perturbation or after coiling has begun, does not prevent coiling from continuing after tendrils are again given a more suitable temperature. It is concluded that the cessation of coiling during the cold period may be due to a slowdown in metabolism. It is suggested that there may be a factor which is responsible for the motor response and which is retained during the cold treatment.     

Heat-resistant Bacteria in Pasteurized Whole Egg

Samples of egg melange taken from an egg packing station contained an average of 7·3 x 10⁴ organisms/ml which survived laboratory pasteurization at 65°C for 3 min. Many of the organisms surviving pasteurization were found to be coryneform bacteria related to Microbacterium lacticum which could be differentiated into several groups. The remainder were a miscellaneous collection of unidentified cocci and coccobacilli and some Bacillus spp. The coryneform bacteria were shown to be the most heat-resistant isolates with negligible loss of viability after 60 min at 65°C, At least two of the representative strains were very heat-resistant, 0·01% surviving 20 and 38 min at 80°C in phosphate buffer at pH 7·1. Growth tests showed that none of the isolates grew at 5°C after 10 d incubation but those capable of growing most rapidly at 10° and 15°C were also the most heat-resistant. Such strains had a doubling time at 15°C of between 6 and 8 h in whole egg. Freezing the coryneform bacteria in liquid whole egg at –18°C had negligible effect on viability or heat-resistance at 65°C.     

Temperature-dependent changes of amine levels during early seedling development of the cold-adapted subantarctic crucifer Pringlea antiscorbutica

Pringlea antiscorbutica R. Br., an endemic crucifer from the Kerguelen Archipelago in the subantarctic, has been previously shown to be unable to acclimatize to 25°C when transferred after several months cultivation under cold conditions. Furthermore, the polyamine composition was greatly modified in such high-temperature-treated plants. The development of seedlings of this species was investigated under a regime mimicking the subantarctic summer thermoperiod (5/10°C night/day) and a regime with high temperatures (22/25°C night/day). In parallel, the associated changes in polyamine composition that occurred during the first 6 days of seedling life were determined. Marked acceleration of seedling growth and intense cotyledon greening were observed at day 4 in 5/10°C-grown seedlings but not in 22/25°C-grown seedlings. Seedlings grown at high temperature accumulated agmatine and putrescine, whereas cold-cultivated seedlings maintained high levels of spermidine. Cold-cultivated seedlings accumulated the uncommon long-chain polyamines norspermidine and homospermidine. These seedlings also accumulated free 1,3-diaminopropane, cadaverine, N¹-acetylspermidine, N¹-acetylspermine and bound polyamines, whereas seedlings under high temperature accumulated N¹-acetylputrescine. Aromatic amine metabolism also appeared to be very responsive to temperature: seedlings under a cold regime accumulated free dopamine and bound phenylethylamine and tyramine, whereas seedlings grown at high temperature accumulated free tyramine. The possible relationships between the observed amine patterns and seedling growth under low and high temperature are discussed.     

AN INCREASE OF ORNITHINE δ-AMINOTRANSFERASE-MEDIATED PROLINE SYNTHESIS IN RELATION TO HIGH-TEMPERATURE INJURY IN GRACILARIA TENUISTIPITATA (GIGARTINALES, RHODOPHYTA)

Changes of proline biosynthesis in relation to high-temperature (35° C) injury were investigated in Gracilaria tenuistipitata var. liui Zhang et Xia. On exposure to 35° C, the specific growth rate decreased after 5 days while free proline levels increased gradually after 2 days and reached the maximal level on days 4–6 but decreased at day 7. The repair ability of thalli treated at 35° C by measuring the growth rate after transfer to 25° C for another 5 days decreased in thalli that had been grown at 35° C for more than 2 days, and the extent increased as treatment at 35° C was prolonged. After 4 days of treatment at 35° C, the activities of both ornithine δ-aminotransferase (δ-OAT; EC 2.6.11.3) and Δ¹-pyrroline-5-carboxylate reductase (P5CR; EC 1.5.1.2) increased, but that of γ-glutamyl kinase (γ-GK; EC 2.7.2.11) remained unchanged, and that of glutamate-5-semialdehyde dehydrogenase (GSAd; EC 1.4.1.3) decreased. The application of 10 μM gabaculine, an irreversible inhibitor of δ-OAT, at 35° C recovered the growth ability but inhibited the increase of both δ-OAT activity and free proline level; its effects were reversed by 1 mM proline. G. saliconia, which is relatively tolerant to high temperature, showed a decrease of both δ-OAT activity and free proline level at 35° C. It seems that a stimulation of proline synthesis from the ornithine pathway via an increase in both δ-OAT and P5CR activities might be associated with high-temperature injury in G. tenuistipitata.     

The effects of temperature and pH on the ethanol tolerance of the wine yeasts, Saccharomyces cerevisiae, Candida stellata and Kloeckera apiculata

The influences of temperature and pH on the survival and growth of Saccharomyces cerevisiae, Candida stellata and Kloeckera apiculata were examined in the presence of ethanol concentrations between 2.5 and 15% v/v. At 15°C, the maximum concentrations of ethanol permitting the growth of S. cerevisiae, C. stellata and K. apiculata were 15%, 11% and 9%, respectively. These maximum concentrations were decreased at 10°C and 30°C. Cells of S. cerevisiae showed no loss in viability when incubated for 12 d at 10°C or 15°C in the presence of 15% ethanol but showed some loss at 30°C. Cells of C. stellata were tolerant of 12.5% ethanol at 10°C and 15°C but not at 30°C. Cells of K. apiculata were tolerant of 10–12.5% ethanol at 15°C but not at 10°C or 30°C. Sensitivity of the yeast cells to ethanol was marginally increased on decreasing the pH from 6-0 to 3–0.     

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.     

Behavioural studies on the lesser sandeel Ammodytes marinus (Raitt) III. The effect of temperature on activity and the environmental control of the annual cycle of activity

The behaviour of the lesser sandeel, Ammodytes marinus (Raitt), has been investigated at 5, 10 and 15° C, using a photographic method of recording activity. The activity patterns at 10 and 15° C were very similar, there being a high level of swimming activity during the light period, which fell to a low level at 5° C. It was also lower at 10° C at the end of the experiment than at the beginning and it is suggested that this might have been due to an increase in the fat contents of the fish. The feeding rate of the fish was measured and showed a Q ₁₀ of 2.08 for the temperature range 5–15° C. The annual cycle of activity of A. marinus is discussed in relation to seasonal changes in food availability, light and temperature, and in the fat content of the fish. It is concluded that after spawning in the December–January period the fish remain buried in the sand until April, because of the limiting effect on swimming and feeding activity of the environmental factors in the intervening period. The proportion of fish available for capture at the start of the fishery in April is related mainly to temperature, but food (as measured by numbers of copepods) light intensity and photoperiod are by then increasing rapidly. After July the fishery ceases and it is thought that this is because the fish have entered an overwintering stage, during which they remain buried in the sand. This phase is also thought to be associated with the maturation of the gonads in readiness for the winter spawning. The factors causing the fish to enter this stage are as yet undetermined but may be related to the attainment of a certain level of fat content.     

Seasonal changes in vertical distribution, biomass and faecal production of tubificids in the profundal region of a shallow Japanese lake

Two tubificid species Limnodrilus hoffmeisteri and L. claparedeianus formed more than 93% of the total number of oligochaetes in the profundal. Limnodrilus spp. worms were found down to 33 cm in the sediment but in great numbers in the upper zone in June and October. Worms confined to the top 15 cm of sediment accounted for 53-92% of the total number. There were two annual maxima in population density and biomass, one in late spring (66000 inds m⁻², 17 g wet wt m⁻²) and the other in mid autumn (97000 inds m⁻², 176 g wet wt m⁻²). Two regression lines describing the effect of temperature on faecal production rate were obtained; Log F = 0.0604 T (°C) −0.7660 (below 15°C), Log F = 0.0266 T – 0.2170 (above 15°C). In total 26.8 kg dry wt m⁻² of sediment was defecated annually by Limnodrilus spp. The sediment in the 0–10 cm stratum may pass through the guts of the worms 2.3 times a year. Sedimentation rates in profundal region were very low with respect to the faecal production rates of the tubificids.     

Effects of different incubation temperatures on the yolk‐feeding stage of Eupallasella percnurus(Pallas)

Embryos and yolk‐feeding larvae of lake minnow Eupallasella percnurus were reared at 13, 16, 19, 22 and 25° C with no access to external food. Time from egg activation to first embryonic movements, hatching, filling of swimbladder and final yolk resorption increased with decreasing temperature. At 13° C, c . 40% of larvae were unable to fill their swimbladder. The predicted lower temperature at which development and growth ceased (biological zero, t ₀) was the same for both processes, c . 7·5–10·5° C. There was no ontogenetic shift in the t ₀ value. Temperature coefficients for development ( Q _10dev.) ranged from 2 to 3 at 19–25° C, but were higher in hatched larvae at lower temperatures. Eggs of E. percnurus had a combination of small size, high hydration and low caloric value of fresh matter. Dry mass of larval tissue on yolk, percentage of dry matter in wet matter, and specific growth rate were maximized at 22 and 25° C. At 19–25° C, energy and matter contained in the initial eggs were converted to body tissue most efficiently. Temperatures from 22 to 25° C are considered optimal for E. percnurus embryos and yolk‐feeding larvae and are recommended for their indoor rearing.     

Increased susceptibility to photoinhibition in pre-existing needles experiencing low temperature at spring budbreak in Sakhalin spruce (Picea glehnii) seedlings

The seasonal changes in photosynthetic properties in 1-year-old needles of Sakhalin spruce ( Picea glehnii ) were measured using the chlorophyll fluorescence technique at various temperatures (5, 10, 20, 25 and 30°C). In the course of seasonal change, a temporary decrease in the quantum yield of PSII electron transport (Φ_PSII) was observed just before budbreak. A decline in photochemical quenching ( q _P) was observed at the same time as that of Φ_PSII but only at the two lowest temperatures (5 and 10°C). Photochemical efficiency of open PSII ( F _v'/ F _m') also declined just before budbreak at 25 and 30°C. An increase in thermal energy dissipation as indicated by a decrease in F _v'/ F _m' before budbreak was not significant at lower temperatures (5 and 10°C) in spite of the declines in q _P. This implies that thermal energy dissipation necessitated by the decline in Φ_PSII might not be sufficiently strong to prevent a decline in q _P at lower temperatures. On the other hand, at higher temperatures no decline was observed in q _P because Φ_PSII decreased to a relatively small extent, therefore thermal energy dissipation is sufficient in coping with the excessive energy accumulation in PSII. Seedlings of Sakhalin spruce exposed to ambient air temperature below 10°C before budbreak exhibited photoinhibition indicated by a decrease in the maximal photochemical efficiency of PSII ( F _v/ F _m) after an overnight dark adaptation. The present study suggests that 1-year-old shoots of Sakhalin spruce have an increased susceptibility to photoinhibition at low temperature just before budbreak.     

Temperature-induced changes of survival, development and yolk partitioning in Chondrostoma nasus

Fertilized Chondrostoma nasus eggs were incubated at 10, 13, 16 and 19° C until full resorption of the yolk sac. High survival was observed at 10–16° C (89–92% at the onset of external feeding), whereas at 19) C survival was depressed (76%). The time at which 5, 50 and 95% of individuals had hatched, filled the swim bladder, ingested the first food and fully resorbed the yolk sac was determined. An increase in temperature accelerated development and made it more synchronous. Within the period from fertilization to hatching embryonic development was theoretically arrested (t_{0 dev}) at 8·8° C, and growth was arrested (t_0gr) at 8·86° C. For the whole endogenous feeding period (from fertilization to full yolk resorption) the amount of matter transformed into tissue was temperature independent between 10° and 19° C. Respiration increased exponentially with age; the respiration increase was faster at higher temperatures, but, in general, metabolic expenditures of C. nasus were low. As a consequence, the efficiency of utilizing yolk energy for growth was high as compared with other fish species (57% during the whole endogenous feeding period); it was temperature independent. However, time was used less efficiently at low temperatures, increasing a risk of predation. Within the endogenous feeding period a shift from lower to higher temperatures for optimal yolk utilization efficiency was observed. The temperatures optimal for survival and energetic performance seem to be 13–16° C for egg incubation and 15–18° C for rearing of yolk-feeding larvae. Chondrostoma nasus is a potential candidate for aquaculture for restocking purposes.     

Apoplastic mobility of sucrose in storage parenchyma of sugar beet

The apoplastic movement of sucrose through storage parenchyma discs (2.4 mm thick) from roots of sugar beet ( Beta vulgaris var. altissima ) was investigated in order to evaluate the suitability of the apoplast for transcellular sugar transport. The sucrose permeability of the discs (P = 5.7 × 10⁻⁸ cm s⁻¹ at 25°C) was more than two orders of magnitude lower than that of an equally thick layer of unstirred water. This is due to the small volume fraction of free space (3.1%) and the decreased diffusion coefficient D of sucrose in the cell walls. The effective diffusion coefficient of the apoplast (6 to 9 × 10⁻⁷ cm² s⁻¹ at 25°C) was determined independently of the cross sectional area of free space by treating the time course of fluxes according to Fick's second law. The high diffusion resistance of the apoplast has to be considered in models of native parenchyma transport.     

Uptake regions of inorganic nitrogen in roots of carob seedlings

Three-week-old seedlings of carob ( Ceratonia siliqua L. cv. Mulata) were grown for 9 weeks under different root temperatures (20, 30 and 40°C) at pH values of 5, 7 and 9 with nitrate or ammonium as nitrogen source. Nitrogen uptake rates were determined by depletion from the medium and decreased with distance from the apex. The decline of nitrogen uptake rates along the roots depended on the form of inorganic nitrogen in the medium as well as on pH and temperature, such that the NO⁻₃ and NH⁺₄ ions were taken up essentially by the root tips (0–2 cm) through processes requiring energy. The uncharged NH₃ species entered passively, through the mature parts of the root (2–10 cm). Root zone temperature and pH affect the NH⁺₄/NH³ equilibrium in the nutrient solution and, consequently, the uptake areas of the root for these ions. Furthermore. while root tip uptake of nitrogen is energy dependent, uptake through mature root areas is essentially passive and seems to depend on a well developed apparent free space.     

Chilling-induced potassium leakage of cultured citrus cells

Callus of 'Marsh' grapefruit ( Citrus paradisi Macf.) albedo tissue was used to investigate the effect of preconditioning temperature on the rate of chilling - stimulated K⁺ leakage. Callus grew most rapidly at 30°C and attained a weight of about 1 g after 30 days. The rate of K.⁺ leakage from nonchilled callus tissue decreased as temperature decreased from 20 to 7.5°C, but no measurable change in rate was observed between 7.5 and 0°C. When calli were held for 40 days at 0¹ 2.5 or 5°C, K⁺ leakage increased 200%, 60% or 0%) respectively. Holding callus for 5 days at 10 or 15°C prior to chilling for 40 days at 0°C prevented the increase in K⁺ leakage observed in callus receiving no preconditioning treatment. Preconditioning at 7.5 and 20°C was less effective in reducing chilling - induced leakage. Preconditioning at 10°C for 5, 2 or 1 day reduced chilling – induced leakage after 40 days at 0°C by 50%, 33% and 15%. respectively.     

Influence of water temperature and feeding regime on otolith growth in Anguilla japonica glass eels and elvers: does otolith growth cease at low temperatures?

The influences of water temperature and feeding regime on otolith growth in Anguilla japonica glass eels and elvers were investigated using individuals reared at 5, 10, 15, 20, 25 and 30° C and in fed or unfed conditions at salinity 32 after their otoliths were marked with alizarin complexone (ALC). To eliminate the difficulty of observing the edges of otoliths with optical (OM) or scanning electron (SEM) microscopes, three to 10 individuals were sampled from each tank at 10, 20 and 30 days during the experiment and reared for an additional 10 days at 25° C after their otoliths were marked a second time. Otolith growth and the number of increments were measured using both OM and SEM. Most A. japonica commenced feeding after 10 days at 20–30° C or after 20 days at 15° C, but no feeding occurred at 5 and 10° C. No otolith growth occurred at 5 and 10° C except in two individuals with minimal increment deposition at 10° C. Otolith growth was proportional to water temperature within 15–25° C and not different between 25 and 30° C. At 15, 25 and 30° C, the mean otolith growth rate in fed conditions was higher than in unfed conditions. The number of increments per day was significantly different among water temperatures (0·00–0·01 day⁻¹ at 5 and 10° C, 0·43–0·48 day⁻¹ at 15° C and 0·94–1·07 day⁻¹ at 20–30° C). These results indicated that otolith growth in A. japonica glass eels and elvers was affected by temperature and ceased at ≤10° C under experimental conditions. Hence, future studies analysing the otoliths of wild-caught A. japonica glass eels and elvers need to carefully consider the water temperatures potentially experienced by the juveniles in the wild.