Latitudinal cline of requirement for far‐red light for the photoperiodic control of budset and extension growth in Picea abies (Norway spruce)

To test for the effects of far‐red light on preventing budset in Picea abies , seedlings of six populations originating from latitudes between 67°N and 47°N were grown for 4–8 weeks in continuous incandescent (metal halogen) light at 300 µmol m⁻² s⁻¹ and 20°C and then transferred, at the same temperature, to a daily regime of 8 h incandescent light (300 µmol m⁻² s⁻¹) followed by 16 h cool white fluorescent light (40 µmol m⁻² s⁻¹). (Cool white lamps are deficient in far‐red light, with a R/FR ratio of 7.5 compared with 2.0 for the incandescent lamps.) All the seedlings from 67° and 80% of those from 64° stopped extension growth and set terminal buds within 28 days of the change of regime. The seedlings from 61° and further south continued growing, as did control seedlings from 67° grown as above but with incandescent light at 20 µmol m⁻² s⁻¹ replacing cool white illumination. To distinguish between a clinal and ecotypic pattern of variation, the interval between 64° and 59° was investigated by growing populations originating from that area in the same regimes as before. After 28 days in the cool white day‐extension regime, the percentage budset was 86 for the population from 64°, 0 for the population from 59° and 25–50 for the intermediate populations; i.e. the populations showed a clinal variation in requirement for far‐red light according to latitude. Thus northern populations of Picea abies appear to behave as 'light‐dominant' plants for the photoperiodic control of extension growth and budset, whereas the more southern populations behave as 'dark‐dominant' plants.     

CHARACTERIZATION OF A LYTIC VIRUS INFECTIOUS TO THE BLOOM-FORMING MICROALGA AUREOCOCCUS ANOPHAGEFFERENS (PELAGOPHYCEAE)

Aureococcus anophagefferens Hargraves and Sieburth has caused recurring monospecific blooms in Long Island embayments since it was first described in 1985. It was termed the "brown tide," due to the resulting water color, and has had a devastating effect on Long Island's (New York) marine ecosystem. In 1992, a virus that was capable of causing lysis of A. anophagefferens was isolated and maintained in culture. We report on the further characterization of this virus, Aureococcus anophagefferens virus-1 (AaV-1), indicated by a buoyant density of 1.2776 g·mL⁻¹ in a CsCl equilibrium gradient. Electron microscopy revealed a phage with a hexagonal head and tail similar to previously described phages. By using adenovirus for calibration, the virus was found to have a head 50—55 nm wide and a tail 70–75 nm long. The viral band was infectious to A. anophagefferens after dialysis. The virus was composed of at least 16 distinct polypeptides ranging in molecular weight from 20 to 230 kDa. The adsorption coefficient for the virus was 7.2 × 10⁻⁹ mL·min⁻¹, and the burst size was calculated to be 9.4 viruses per A. anophagefferens cell at 20° C. Complete lysis of A. anophagefferens occurred with a titer as low as 893 viruses·mL⁻¹, and the lower limit of infectivity was 93 viruses·mL⁻¹. The virus lost its infectivity between 30° and 40° C. These results suggest that AaV-1 is highly infectious and that the role of the virus in preventing or ending A. anophagefferens blooms needs further investigation.     

Requirement for far-red light to maintain secondary needle extension growth in northern but not southern populations of Pinus sylvestris (Scots pine)

Extension growth of secondary needles is under photoperiodic control in Pinus sylvestris . To test for the effects of far-red light on maintaining this extension growth, seedlings of six populations originating from latitudes between 57° and 67°N were raised for 11 weeks in continuous incandescent (metal halogen) light at 300 µmol m⁻² s⁻¹ and 20°C and then transferred at the same temperature to a daily regime of 8 h incandescent light (230 µmol m⁻² s⁻¹) followed by a 16 h day extension with cool white fluorescent light (40 µmol m⁻² s⁻¹, R/FR ratio 7.5) or with incandescent lamps (20 µmol m⁻² s⁻¹, R/FR ratio 2.0). For the seedlings from the three populations north of 64°, needle extension growth over 42 days in the FR-poor day extension treatment was lower by up to 40% than in the FR-rich day extension treatment, whereas for the seedlings from the three southern populations the needle extension growth was similar in both day extension treatments. The requirement for FR in day extensions is characteristic of 'light-dominant' photoperiodic control mechanisms. It appears that P. sylvestris changes from dark-dominant night timekeeping to light-dominant day timekeeping with increasing latitude, as with the photoperiodic control of budset in Picea abies .     

Division of guard cell protoplasts of Nicotiana glauca (Graham) in liquid cultures

Abstract. Guard cells are uniquely differentiated to transduce signals into the metabolic and ion transport processes that result in turgor-driven stomatal movements. We tested the hypothesis that these highly specialized cells are terminally differentiated. Guard cell protoplasts were isolated from abaxial epidermal tissue of leaves of Nicotiana glauca (Graham) and cultured in a medium designed for culturing mesophyll protoplasts of Nicotiana tabacum. Protoplasts were incubated at densities of 2–5 × 10¹¹ cells m⁻³ in eight-well microchamber slides under 50μmol m⁻² s⁻¹ of photons of continuous fluorescent light at 25°C. When the medium was modified by the addition of 100mol m⁻³ of sucrose and by buffering with 10mol m⁻³ of MES buffer at pH 6.1, cell division began within 96h of the time the culture was initiated. After 9d of culture, 80% of surviving cells had synthesized new cell walls, had dedifferentiated, and were dividing to form small colonies. Callus tissue was visible after 4–5 weeks. We conclude that guard cells of Nicotiana glauca are not terminally differentiated, and that guard cell protoplasts of this species have the capacity to grow, synthesize cell walls and divide.     

The Isolation and Some Characteristics of Photosynthetic Bacteria (Chromatiaceae and Chlorobiaceae) from Antarctic Marine Sediments

Sediment samples taken at depths from 5 to 50 m in Borge Bay, Signy Island, Antarctica yielded purple ( Chromatiaceae ) and green ( Chlorobiaceae ) phototrophic bacteria when inoculated into Winogradsky columns or directly into Pfennig's medium. Pure cultures of Thiocapsa roseopersicina (2 strains), Thiocapsa pfennigii, Chromatium gracile, Chromatium vinosum, Thiocystis violaceae, Chlorobium limicola, Chlorobium vibrioforme and Prostaecochloris aestuarii were subsequently isolated from these enrichments. Thiocapsa roseopersicina and Chromatium vinosum were the species isolated most commonly. None of the isolates showed evidence of temperature adaptation; optimum growth was achieved between 25–30°C but all grew readily at low white light levels (spectral irradiance 160 μW/cm²) with mean generation times ranging from 8·9 to 14·2 h at 23°C depending upon the isolate. The green phototrophs grew readily in blue light (440–510 nm) of low irradiance (126 μW/cm²) which penetrates to a depth of 40–50 m in coastal waters surrounding Signy Island. Under these conditions Chlorobium limicola and Chlorobium vibrioforme had mean generation times of 22 and 12·2 h respectively compared with 10·3 and 8·9 when grown in white light of similar total irradiance. None of the purple phototrophs grew under blue light but they grew under yellow light (peak transmission 590 nm, irradiance 137 μW/cm²). Chromatium gracile and Thiocapsa roseopersicina had mean generation times of 22·3 and 18·3 h respectively compared with 14·2 and 12·3 h in white light of similar total irradiance.     

CIRCADIAN RHYTHM OF PHOTOSYNTHETIC OXYGEN EVOLUTION IN KAPPAPHYCUS ALVAREZII (RHODOPHYTA): DEPENDENCE ON LIGHT QUANTITY AND QUALITY

The rate of oxygen evolution of the tropical red alga Kappaphycus alvarezii (Doty) Doty was measured for 6 days in the laboratory using a computer-aided method for long-term recording. In cool white light, Kappaphycus exhibited a robust circadian rhythm of O₂ evolution in the irradiance range of 100 to 1000 μmol photons·m ^{− 2}·s ^{− 1}. With increasing irradiance, the period of the free-running rhythm, τ, decreased in blue and increased in red light but did not change significantly in green light. The accelerating or slowing action of blue or red light, respectively, points to two photoreceptors used in the light transduction pathway of the circadian oscillator controlling oxygen evolution or the light reactions of photosynthesis in Kappaphycus. No significant changes of τ were observed with increasing irradiance in cool white light, possibly due to the additive opposing responses caused by blue and red light.     

Response to directional light by leaves of a sun-tracking lupine (Lupinus succulentus)

Experiments were done to examine the phototrophic response of sun-tracking leaves of Lupinus succulentus Dougl. to fixed beams of white and broad band light. Upon irradiation with 15 W m⁻² white light that struck the laminae at an angle of 45°, there was a 45–60 min lag period prior to leaf movement. The greatest rate of movement was 15° h⁻¹, and reorientation ceased when leaves attained a position within 15° of perpendicular to the light beam. Laminar movement was largely pulvinar, and a 60 min inductive light treatment was sufficient to activate a maximum pulvinar response in subsequent darkness. Light striking the lamina at angles between 20 and 70° induced similar maximum pulvinar responses and only light that struck the upper (adaxial) leaf surface was effective. Leaf tracking was fully activated by blue light but not by red or yellow light.     

SULPHIDE PRODUCTION FROM SULPHATE-ENRICHED SEWAGE SLUDGES

SUMMARY: Sterilized raw sewage sludge enriched with sulphate and inoculated with pure strains of Desulphovibrio desulphuricans produced negligible sulphide. Unsterilized sludge supplemented with 7% (w/v) CaSO₄.2H₂O and inoculated with crude cultures of sulphate-reducing bacteria obtained from sewage yielded 1·0% S^2- (wt S^2- produced as H₂S/vol. of raw sludge) in 6 months at 30°. By repeated subculture more active cultures developed which produced 1% S^2- in 7 days and 1·2–1·9% in 28 days. Digested sludge yielded only 0·1% S^2-. In semicontinuous fermentations at 30°, raw sludge without added sulphate produced 20 times its own volume of gas containing 70% CH₄ and 30% CO₂. When 5% CaSO₄.2H₂O and an active crude culture of sulphate reducers were added, gas production decreased steadily to zero. There were no differences in pH, temperature and redox potential in sludges producing methane or sulphide. The chief cause of inhibition appeared to be the action of sulphide: 0·02% soluble sulphide (S^2-) totally inhibited methane formation; 0·01% S^2- initially decreased gas production by one-quarter but there was a slow recovery to normal, suggesting acclimatization of the methane-producing organisms to sulphide.
Linked fermentations, in which gas from a methane fermentation swept H₂S from a sulphide fermentation, gave a final gas mixture of about 60% CH₄, 30% CO₂ and 5–10% H₂S. The yield of sulphide depended on the rate of sweeping.     

Effect of Iysozyme concentration, heating at 90°C, and then incubation at chilled temperatures on growth from spores of non-proteolytic Clostridium botulinum

The heat treatment necessary to inactivate spores of non-proteolytic Clostridium botulinum in refrigerated, processed foods may be influenced by the occurrence of lysozyme in these foods. Spores of six strains of non-proteolytic Cl. botulinum were inoculated into tubes of an anaerobic meat medium, to give 10⁶ spores per tube. Hen egg white lysozyme (0–50 μg ml^-1) was added, and the tubes were given a heat treatment equivalent to 19·8 min at 90°C, cooled, and incubated at 8°, 12°, 16° and 25°C for up to 93 d. In the absence of added lysozyme, neither growth nor toxin formation were observed. A 6–D inactivation was therefore achieved. In tubes to which lysozyme (5–50 μg ml^-1) had been added prior to heating, growth and toxin formation were observed. With lysozyme added at 50 μg ml^-1, growth was first observed after 68 d at 8°C, 31 d at 12°C, 24 d at 16°C, and 9 d at 25°C. Thus, in these circumstances, a heat treatment equivalent to 19·8 min at 90°C was not sufficient, on its own, to give a 6–D inactivation. A combination of the heat treatment, maintenance at less than 12°C, and a shelf-life not more than 4 weeks reduced the risk of growth of non-proteolytic Cl. botulinum by a factor of 10⁶.     

Energy and ration requirements of juvenile Pacific halibut (Hippoglossus stenolepis) based on energy consumption and growth rates

Growth of captive juvenile Pacific halibut was linearly related to energy consumption (J g⁻¹ day⁻¹) at 4°C by the following equation: growth (% body weight (b.w.) day⁻¹)=0–007 (consumption J g⁻¹ day⁻¹)– 0.192; r² =0.81. Weight gain was independent of size for fish between 9 and 7000 g when growth was expressed as a function of consumption in J g⁻¹ day⁻¹. Maintenance ration determined in feeding–growth experiments averaged 27.4 J g⁻¹ day⁻¹ at 4–0°C. Small halibut ate significantly more food than large fish. Single meals following 2 day fasts averaged 4.1% b.w. for halibut under 100 g, 1.72% b.w. for 1.2 kg fish and 1.1% B.W. for 6.8 kg fish. Both large and small size categories of halibut tended to evacuate their meal in about 3 days even though small fish ate relatively larger meals. Minimum estimates for daily ration to achieve growth rates observed in the Gulf of Alaska were approximately 0.5 to 2.4% b.w. day⁻¹ depending on fish size and whether northern shrimp or yellowfin sole were their prey.     

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).     

NEW GENERA OF FRESHWATER CRYPTOMONADS FROM COLORADO

Given their rapid growth and nutrient assimilation rates, Porphyra spp. are good candidates for bioremediation. The production potential of two northeast U.S. Porphyra species currently in culture ( P. purpurea and P. umbilicalis ) was evaluated by measuring rates of photosynthesis (as O₂ evolution) of samples grown at 20° C. Gametophytes of P. umbilicalis photosynthesized at rates that were 80% higher than those of P. purpurea over 5–20° C at both sub-saturating and saturating irradiances (37 and 289 μmol photons m⁻² s⁻¹). Porphyra umbilicalis was both more efficient at low irradiances (higher alpha) and had a higher P_max than did P. purpurea (23.0 vs. 15.6 μmol O₂ g⁻¹ DW min⁻¹), suggesting that P. umbilicalis is a better choice for mass culture where self-shading may be severe. The photosynthesis-irradiance relationship for the Conchocelis stage of P. purpurea was also examined. Tufts of filaments, grown at 10, 15, and 20° C, were assayed at growth temperatures at irradiances ranging from 0–315 μmol photons m⁻² s⁻¹. Tufts were slightly more productive at 15° than at 10° C, but only ca. 4–6% as productive as gametophytes. Maximum rates of net photosynthesis were reduced by 66–74% in tufts grown at 20° C (only about 2% of gametophytes). The Conchocelis stage, however, need not limit mariculture operations; once Conchocelis cultures are established, they can be maintained over the long-term as ready sources of spores for net seeding.     

Ceratium in Lake Erken: vertical distribution, migration and form variation

External morphological features and growth characteristics of the dinoflagellates Ceratium hirundinella and C. furcoides were investigated in relation to the environmental conditions in Lake Erken. Three distinct population maxima were distinguished, one in June, one in July, and one in September. C. hirundinella dominated the spring and summer populations. C. furcoides was rare in June, but it continuously increased and composed ca. 18% of the Ceratium-cetts in the autumn. The size of a C. hirundinella decreased during the investigation period and a form with a long horn disappeared in June. Ceratium was most numerous during the warmer periods in summer when a distinct thermocline appeared and before the turnover period in September. The alga preferred depths down to 3 m where the blue light dominated and the following parametric magnitudes could be measured: oxygen contents >5 mg 1^-1, pH >7, HCO₃, >1.7 meq. · 1^-1, and a specific conductivity of ca. 250 mS · cm^-1. The algal growth periods displayed doubling times of 2.63 and 4.04 days at surface temperatures of 19°C and 15°C, respectively. The water transparency decreased 3.8 m when Ceratium reached cell densities of 13 individuals · ml^-1 (0–10 m depth). Its vertical migration demonstrated a dial rhythm with accumulation of cells in the surface waters during the day. Complicated patterns of surface avoidance occurred in clear weather and under wind stress.     

A light intensity threshold for schooling in the Atlantic mackerel, Scomber scombrus

The schooling behaviour of Atlantic mackerel was studied in a large tank at different light intensities in the range 12.6–1.8 × 10⁻¹⁰μEs⁻¹ m⁻². Variable light intensity was produced by accurately controlling the current to a green light-emitting diode (LED) 3 m above the experimental tank. Under high light levels (1.8 × 10⁻⁶μEs⁻¹ m⁻²) mackerel always formed a single school, whereas at lower levels (1.8 × 10⁻⁸μEs⁻¹ m⁻²) they swam as individuals. At light levels down to 1.0 × 10⁻⁶μEs⁻¹ m⁻² the mean nearest neighbour distance in a school remained relatively constant (0.3–0.9 body lengths), and individual mackerel swam along a path which deviated from the position of their nearest neighbours by less than 14°. As light dropped below 1.8 × 10⁻⁷μEs⁻¹ m⁻², both nearest neighbour distance and heading angle between nearest neighbours increased, with mean values of 1–1.8 body lengths and 23–92°, respectively, at 1.8 × 10⁻⁹μEs⁻¹ m⁻². The results are discussed in terms of ambient light conditions in the sea.     

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.     

Thermoregulation and metabolism in the Cape golden mole (Insectivora: Chrysochloris asiatica)

The Cape golden mole, Chrysochloris asiatica is an insectivore which excavates superficial foraging burrows as it searches for its food. It has a mean (±S.D.) resting metabolic rate (RMR) when newly captured of 1–17±0.17 cm³ O₂g^-1 h^-1 ( n = 14), within the thermoneutral zone (TNZ) of 30–32°C.
The body temperature (Tb) of the mole in the TNZ is low 32.9 ± 0.36 ( n = 14) and remains stable at ambient temperatures (Tas) from 28–32°C. Above 32°C (range 34–37°C), Tb increases albeit slightly to 36 ± 1.75°C ( n = 14). The conductance is high 0.27 ± 006cm³ O₂g^-1 h^-l°C^-1 ( n = 46) at the lower limit of thermoneutrality. The mean RMR at 9°C (the lowest Ta tested) was 4.82±11 cm³ O₂g^-1h^-1, which is 4.1 times that of the RMR in the TNZ.
At an ambient temperature of 9°C, three of the golden moles entered a state of torpor where the RMR was reduced from 5.9±0.56 to 10 1.0 ± 0.69cm³O₂g^-1h^-1.     

PHYSIOLOGICAL RESPONSES TO TEMPERATURE AND IRRADIANCE IN SPIROGYRA (ZYGNEMATALES, CHAROPHYCEAE)1

Spirogyra Link (1820) is an anabranched filamentous green alga that forms free-floating mats in shallow waters. It occurs widely in static waters such as ponds and ditches, sheltered littoral areas of lakes, and stow-flowing streams. Field observations of its seasonal distribution suggest that the 70-μm-wide filament form of Spirogyra should have a cool temperature and high irradiance optimum for net photosynthesis. Measurements of net photosynthesis and respiration were marie at 58 combinations of tight and temperature in a controlled environment facility. Optimum conditions were 25°C and 1500 μmol photons m⁻² s⁻¹, at which net photosynthesis averaged 75.7 mg O₂ gdm⁻¹ h⁻¹. Net photosynthesis was positive at temperatures from 5° to 35°C at most irradiances except at combinations of extremely low irradiances and high temperatures (7 and 23 μmol photons m⁻² s⁻¹ at 30°C and 7, 23, and 35 μmol photons m⁻² s⁻¹ at 35°C). Respiration rates increased with both temperature and prior irradiance. Light-enhanced respiration rates were significantly greater than dark respiration rates following irradiances of 750 μmol photons m⁻² s⁻¹ or greater. Polynomials were fitted to the data to generate response surfaces; such response surfaces can be used to represent net photosynthesis and respiration in ecological models. The data indicate that the alga can tolerate the cool water and high irradiances characteristic of early spring but cannot maintain positive net photosynthesis under conditions of high temperature and low light (e.g. when exposed to self-shading ).     

Longevity of the freshwater anostracan Streptocephalus mackini (Crustacean: Anostraca) in relation to food (Chlorella vulgaris) concentration

SUMMARY 1. Temporary ponds are inhabited by a variety of invertebrates, of which anostracans are an important group. We studied the lifetables of male and female anostracan Streptocephalus mackini at 3 algal concentrations (0.5 × 10⁶, 1.0 × 10⁶ and 1.5 × 10⁶ cells mL⁻¹).
2. Regardless of sex, S. mackini showed better survivorship at lower food levels. The longest average lifespan observed was 85 ± 2 days for males fed Chlorella at 0.5 × 10⁶ cells mL⁻¹.
3. Both net reproductive rate and generation time decreased with increasing food level. The highest net reproductive rate was about 120 cysts per female. The longest generation time of about 40 days, observed at 0.5 × 10⁶ cells mL⁻¹, was more than three times that at 1.5 × 10⁶ cells mL⁻¹.
4. The rate of population increase ( r ) was nearly the same (0.31 ± 0.06) at high (1.5 × 10⁶ cells mL⁻¹) and intermediate (1.0 × 10⁶ cells mL⁻¹) food levels. The r -value at low food level (0.5 × 10⁶ cells mL⁻¹ of Chlorella ) was 0.20 ± 0.01 per day.     

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.     

The effect of temperature and fish size on growth and feed efficiency ratio of juvenile spotted wolffish Anarhichas minor

The growth properties of juvenile spotted wolffish Anarhichas minor reared at 4, 6, 8 and 12° C, and a group reared under 'temperature steps', (T‐step) i.e . with temperature reduced successively from 12 to 9 and 6° C were investigated. Growth rate and feed efficiency ration was significantly influenced by temperature and fish size. Overall growth rate was highest at 6° C (0·68% day⁻¹) and lowest at 12° C (0·48% day⁻¹), while the 4 and 8° C, and the T‐step groups had similar overall growth rates, i.e . 0·59, 0·62 and 0·51% day⁻¹ respectively. Optimal temperature for growth ( T _{opt G} ) and feed efficiency ratio (T_{opt FCE}) decreased as fish size increased, indicating an ontogenetic reduction in T _{opt G} and T _{opt FCE}. The results suggest a T _{opt G} of juvenile spotted wolffish in the size range 135–380 g, dropping from 7·9° C for 130–135 g to 6·6° C for 360–380 g juveniles. The T _{opt FCE} dropped from 7·4° C for 120–150 g to 6·5° C for 300–380 g juveniles. A wider parabolic regression curve between growth, feed efficiency ratio and temperature as fish size increased, may indicate increased temperature tolerance with size. Individual growth rates varied greatly at all time periods within the experimental temperatures, but at the same time significant size rank correlations were maintained and this may indicate stable size hierarchies in juvenile spotted wolffish.