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.     

The compatibility of the fungicide azoxystrobin with Pochonia chlamydosporia, a biological control agent for potato cyst nematodes (Globodera spp.)

The biological control potential of Pochonia chlamydosporia against root-knot ( Meloidogyne spp.) and cyst-forming ( Heterodera and Globodera spp.) nematodes is widely appreciated. In spite of this, little has been undertaken to determine the compatibility of this fungus with modern fungicides. A series of experiments were undertaken to investigate the effect of azoxystrobin on P. chlamydosporia . Initial Petri dish experiments found a significant reduction in the growth of P. chlamydosporia . EC₅₀ values were calculated at 7 and 14 mg L⁻¹, respectively, for hyphal growth and chlamydospore germination. A microcosm experiment based on counts of the colony-forming units of the re-isolated fungus showed a reduction in EC₅₀ values for azoxystrobin in soil after 12, 20 and 40 days incubation (1.25, 1.00 and 3.00 mg kg⁻¹ soil, respectively). There was evidence the fungus recovered over time in response to azoxystrobin application. This was also demonstrated in a glasshouse experiment where EC₅₀ values of 1.32 and 4.4 mg kg⁻¹ soil were obtained for 35 and 49 days after planting (DAP), respectively.     

Long-term effects of successive Ca(OH)2 and CaCO3 treatments on the water quality of two eutrophic hardwater lakes

1. Whole-lake experiments were conducted in two hardwater lakes (Halfmoon and Figure Eight) in Alberta, Canada, to investigate the effectiveness of repeated lime (slaked lime: Ca(OH)₂ and/or calcite: CaCO₃) treatments (5–78 mg L^–1) for up to 7 years.
2. Randomized intervention analysis of intersystem differences between the experimental and three reference lakes demonstrated a decline in euphotic total phosphorus and chlorophyll a concentrations in the experimental lakes after repeated lime treatments.
3. After the second lime application to Halfmoon Lake, mean winter total phosphorus release rates (TPRR) decreased to < 1 mg m^–2 day^–1 compared with 3.6 mg m^–2 day^–1 during the winter after initial treatment. In the final year of lime application, mean summer TPRR decreased to 4.5 mg m^–2 day^–1 compared with 7.6 mg m^–2 day^–1 in the pre-treatment year.
4. Mean macrophyte biomass declined and species composition was altered at 1 and 2 m depths in Figure Eight Lake during lime application. Over the first 6 years of treatment, macrophyte biomass at 2 m declined by 95% compared with concentrations recorded during the initial treatment year. In the last year of the study, macrophyte biomass at 2 m reached initial treatment concentrations, which coincided with the greatest water transparency. Over the treatment period, macrophyte species shifted from floating to rooted plants.
5. Multiple lime applications can improve water quality in eutrophic hardwater lakes for periods of up to 7 years.     

The effect of different dietary iron levels on growth and hepatic iron concentration in juvenile gibel carp (Carassius auratus gibelio)

An 83-day growth trial was conducted using a flow-through system to examine the effects of different dietary iron levels on growth and hepatic iron concentration in juvenile gibel carp ( Carassius auratus gibelio ). Six purified diets supplemented with different levels of iron (0, 10, 30, 60, 100 and 200 mg kg⁻¹) (as ferrous sulfate) were fed to triplicate groups of fish (initial weight 2.12 ± 0.00 g per fish). The results showed that the addition of iron to the basal diet did not significantly affect the specific growth rate (SGR), feed efficiency (FE), survival, red blood cell amount (RBC), hemoglobin content (Hb), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) or mean corpuscular hemoglobin concentration (MCHC). Hepatic iron concentration and hematocrit (Hct) were significantly influenced by dietary iron level (P < 0.05). On the basis of the iron concentration for the maintenance of optimum hepatic iron concentration and Hct, it was concluded that the dietary iron concentration of juvenile gibel carp should be not less than 202 mg Fe kg⁻¹ diet.     

Habitat use and trophic position determine mercury concentration in the straight fin barb Barbus paludinosus, a small fish species in Lake Awassa, Ethiopia

The diet, habitat use and mercury concentration of the small fish species, the straight fin barb Barbus paludinosus , were studied in Lake Awassa, Ethiopia, for a period of 1 year from February 2003 to January 2004. Stable isotope signatures of nitrogen and carbon in different total length ( L _T) classes were used to determine trophic positions and organic carbon sources, respectively. Barbus paludinosus mainly occupied the protected benthic habitats (littoral and profundal) of the lake. The δ¹³C values were in the range from −24 to −19‰, indicating that the carbon source for B. paludinosus was benthic, as well. Small individuals (≤ 60 mm L _T) mainly preyed upon ostracods, intermediate sizes (60–100 mm) on aquatic insects and gastropods, while a tiny cyprinodont fish Aplocheilichthys antinorii dominated the diet of large individuals (100–160 mm). The progressively increase in δ¹⁵N with increasing L _T also indicated a diet shift towards piscivory in larger individuals. The mercury concentration ranging from 0·02 to 0·74 mg kg⁻¹ wet mass (wm), was unexpectedly high in this small species, and was significantly positively related to L _T, as well as to δ¹⁵N. Some large individuals had mercury concentrations < 0·1 mg kg⁻¹ wm, and low δ¹⁵N, indicating substantial variations in diet between individuals of same size. The study suggests that other piscivorous species which include B. paludinosus in their diet may have a high mercury intake risk.     

Cellular and biochemical response to Cr(VI) in Stenotrophomonas sp.

Chromium (Cr)-resistant bacteria isolated from a soil with 6 g kg⁻¹ of Cr were identified based on 16S rRNA gene sequence analysis as a Stenotrophomonas , and designated as JD1. Growth of JD1 was accompanied by transformation of Cr(VI) to Cr(III) in liquid medium initially containing 300 mg L⁻¹ Cr(VI), the maximum concentration allowing growth. JD1 produced the highest levels of a Cr(VI)-binding exopolysaccharide when grown in medium with 100 mg L⁻¹ Cr(VI). The relative exopolysaccharide monosaccharide composition was analysed by HPLC, which showed that rhamnose+galactose was the major component, and that its relative level increased when cells were grown with Cr(VI). JD1 grew as a biofilm on various inert surfaces. Biofilm macromolecular composition analysis indicated that the relative levels of exopolysaccharide and protein were more abundant in biofilms grown in 100 mg L⁻¹ Cr(VI), whereas relative uronic acid levels remained constant. Biofilm cells exposed to Cr(VI) were elongated, grouped in clusters and exopolysaccharide obtained from the biofilm extracellular matrix had an enhanced capacity to bind Cr(VI). Exopolysaccharide production and composition, and biofilm growth are discussed as a mechanism of protection that allows survival during Cr(VI) stress.     

Growth performance, mortality and carotenoid pigmentation of fry offspring as affected by dietary supplementation of astaxanthin to female rainbow trout (Oncorhynchus mykiss) broodstock

Growth performance, mortality and carotenoid pigmentation were studied in triplicate groups each with 1000 swim-up larvae of rainbow trout ( Oncorhynchus mykiss ), derived from five groups of female broodstock fed diets with 0.07, 12.5, 33.3, 65.1 or 92.9 mg astaxanthin kg⁻¹, respectively. The first feeding fry (initial weight range from 113 to 148 mg) were fed a diet not supplemented with carotenoids in an experiment lasting 45 days. Fry were initially sampled for astaxanthin content and initial weight, and in subsequent 15-day intervals to determine weights, condition factors (CF), specific growth rates (SGR) and thermal growth coefficients (TGC). Total carotenoid concentration of the larvae was highly linearly correlated to that of the eggs ( r ² = 0.97, P = 0.002). About 59–67% of fry carotenoids consisted of esterified astaxanthin, and on average 39.7% of the egg carotenoids were recovered in the fry. Overall (0–45 days) SGRs and TGCs were significantly higher (P < 0.05) in the offspring of the four groups of females fed supplemented diets (12.5–92.9 mg astaxanthin kg⁻¹) than in offspring of females fed the non-supplemented diet. TGCs (0–45 days) within groups derived from broodstock supplemented with astaxanthin were similar (P > 0.05), but higher than in the group derived from females fed the diet not supplemented with astaxanthin (P < 0.05). Mortality (average 0.76%) was not significantly affected by treatment. The study indicates that dietary supplement of astaxanthin (>12.5 mg kg⁻¹) to maternal broodstock diets improves offspring SGR and TGC with up to 33 and 38%, respectively.     

Potential of Bacillus sp. to produce polyhydroxybutyrate from biowaste

Aim:  To test the Bacillus strains for their abilities to produce polyhydroxybutyrate (PHB) from different sugars and biowaste (Pea-shells).
Methods and Results:  Six Bacillus strains were checked for their ability to produce PHB from GM2 medium supplemented with different sugars at the rate of 1% (w/v) and from biowaste and GM2 (BW : M) combinations (3 : 7, 1 : 1, 7 : 3). Glucose supplemented GM2 medium resulted in maximum PHB production of 435 mg l⁻¹ constituting 31–62% w/w of the total cell dry mass. Substituting GM2 medium to the extent of 50% with biowaste (pea-shell slurry) resulted in 945–1205 mg l⁻¹ PHB (55–65% w/w). Optimization for additional nitrogen supplementation, inoculum size resulted in a final PHB production of 3010–3370 mg l⁻¹ equivalent to 300 g kg⁻¹ biowaste (dry wt).
Conclusion:  The Bacillus strains were able to produce PHB from biowaste (Pea-shells) as cheap source of substrate.
Significance and Impact of the Study:  This is the first report on usage of pea-shells as feed for PHB production, opening new possibilities for its use for production of PHB and Bacillus as potential candidate for the purpose.     

More effective induction of spawning with long-acting GnRH agonist in the shi drum, Umbrina cirrosa L. (Sciaenidae, Teleostei), a valuable candidate for Mediterranean mariculture

Three experiments of spawning induction in shi drum, Umbrina cirrosa L., were performed in six different commercial Italian hatcheries from May to August (water temperatures: 19–29 °C; salinity: 21–37 p.p.t.). In the first experiment, 119 females (1–4.7 kg), subdivided into 29 lots, were injected with a single dose (2, 5, 8, 10, 15 and 20  μ g kg⁻¹ body weight) of short-acting gonadotropin- releasing hormone agonist (GnRHa-S), des-Gly10,[D-Ala6]-LH-RH ethylamide. In the other two experiments, 85 females (0.7–5.8 kg), subdivided into 22 and four lots, were treated with one (40 or 80  μ g kg⁻¹) or three doses (40  μ g kg⁻¹) of long-acting GnRHa (GnRHa-L), respectively. GnRHa-S stimulated spawning in 69% of the 29 treated lots; the number of eggs laid reached a maximum of 130 000 and a weighted mean of 29 200 total eggs kg⁻¹. GnRHa-L elicited a spawning response in 95% of the 22 one-dose treated lots; the number of laid eggs was higher than with GnRHa-S, reaching a maximum of 213 100 and a weighted mean of 59 400 total eggs kg⁻¹. The yield of developing embryos in 67% of the single GnRHa-L treatments was higher (sometimes up to three times) than with GnRHa-S. Triple treatments of the four lots of females with GnRHa-L always resulted in spawning responses; the best result corresponded to a number of total laid eggs of 358 900 eggs kg⁻¹ with a yield of 177 300 developing embryos.     

Farm-scale trials to compare the entomopathogenic fungus Beauveria bassiana with pirimiphos methyl + deltamethrin and essential oil of lemon grass for protection of stored cowpea against Callosobruchus maculatus (Coleoptera: Bruchidae)

In trials conducted in Benin, conidia of Beauveria bassiana were evaluated as a control method against the cowpea weevil, Callosobruchus maculatus , in stored cowpea. In the first trial using a high artificial infestation of C.   maculatus in 8-kg batches of cowpea in jerry cans under typical conditions, concentrations of 1 × 10⁹ and 1 × 10¹¹ conidia kg⁻¹ were compared with lemon grass oil at 2 mL kg⁻¹ and the synthetic pesticide mixture of 1.5% pirimiphos methyl + 0.05% deltamethrin at 0.5 g kg⁻¹. After 2 months of storage, seed losses (SD) were 20.63 (5.3)% in the untreated control, 8.04 (3.2)% in the low-dose B.   bassiana group, 3.12 (1.3)% in the high-dose B.   bassiana group, 2.52 (0.4)% in the lemon grass oil group and 0% in the pirimiphos methyl + deltamethrin group. In a second trial with natural infestations in 50-kg batches of cowpea in 200-L drums, treatment with B.   bassiana 1 × 10¹¹ conidia kg⁻¹ was compared with pirimiphos methyl + deltamethrin at 0.5 g kg⁻¹. After 6 months of storage on six farms, losses reached 30.76 (1.5)% in the control, 1.28 (0.2)% in the pirimiphos methyl + deltamethrin group and 3.69 (0.6)% in the B.   bassiana group.     

Geophagy and nutrient supplementation in the Ngorongoro Conservation Area, Tanzania, with particular reference to selenium, cobalt and molybdenum

Wildlife and livestock in the Ngorongoro Conservation Area (NCA), Tanzania, commonly practise geophagy. We investigated the nutrient content of nine earth licks and adjacent topsoils in the NCA, and for comparative purposes, two salt pans in north-eastern Tanzania, licks in central Tanzania and a lick near Puerto Maldonado, Peru. The licks had no consistent pattern of nutrient enrichment relative to unutilized topsoils, although the Na content of licks was greater than that of the adjacent topsoils at all but one site. The three largest licks in the NCA (Gibbs Farm, Seneto and Ascent Road) were enriched relative to topsoils and global averages in Se (maximum of 4.7 mg kg⁻¹), Co (maximum of 107 mg kg⁻¹) and/or Mo (maximum of 7.4 mg kg⁻¹). We suggest that licks do provide supplemental Na, but that Se, Co and/or Mo at the largest licks provide easily overlooked nutritional benefits and are perhaps the primary target for geophagy at these sites. Subsoil zones of clay deposition are likely to be enriched in various elements through illuviation or mineral precipitation from solution. Animals may use the taste of NaCl as a clue for locating such zones where they are likely to find a greater quantity of micronutrients relative to other soils. These findings have consequences for conservation and pastoralism in that these large licks may be key resources, providing micronutrients that are essential for maintaining the health and fecundity of animal as well as human populations in the region.     

Modulation of nonspecific defence mechanisms and specific immune responses after suppression induced by xenobiotics

Summary In the present study the possible modulation of nonspecific defence mechanisms and specific immune responses after suppression induced by oxytetracycline, oxolinic acid, and lindane – an organochlorine pesticide, were analysed in carp. Modulation was attempted using a natural immunostimulant, dimerized lysozyme (KLP-602, Nika Health Products, USA). Five groups of fish were given intraperitoneal injections of selected doses of the drugs on days 7, 6 and 4 before immunization with Yersinia ruckeri vaccine. At each injection, group I was also given 10 mg kg⁻¹ oxytetracycline, group II 10 mg kg⁻¹ oxolinic acid, group III 10 mg kg⁻¹ lindane, group IV was only immunized, and group V was injected with PBS. The immunostimulant was added in food before and after immunization. The study showed the immunotoxic effects of oxytetracycline, oxolinic acid and lindane; dimerized lysozyme corrected the defence mechanisms suppressed by these drugs and chemicals. The immunostimulatory effects of dimerized lysozyme were better when added before rather than after fish immunization.     

Plant palatability and disturbance level in aquatic habitats: an experimental approach using the snail Lymnaea stagnalis (L.)

1. The palatability of aquatic macrophytes to the snail Lymnaea stagnalis was investigated in the laboratory. Eight species of macrophyte were selected from habitats that differed in either flood disturbance regime or nutrient status.
2. In a non-choice test, single macrophyte species were offered to individual snails. The average amount of plant dry mass consumed per Lymnaea dry mass ranged from 3.6 ± 1.4 (±SE) to 63.6 ± 13.9 mg g^–1 day^–1 across plant species. In a choice test, all eight plant species were presented simultaneously to sets of five snails. The average total consumption was 66.1 ± 3.8 mg g^–1 day^–1 and the maximum average consumption for a single plant was 26.2 ± 3.6 mg g^–1 day^–1.
3. In both tests, the amount consumed by snails differed significantly between the plant species. The species growing in undisturbed habitats were the least consumed. Habitat nutrient status was unrelated to plant palatability.
4. These results suggest that macrophyte species growing in habitats that are rarely disturbed by floods allocate a greater proportion of their resources to resisting herbivory.     

Endurance swimming of European eel

A long‐term swim trial was performed with five female silver eels Anguilla anguilla of 0·8–1·0 kg ( c . 80 cm total length, L _T) swimming at 0·5 body lengths (BL) s⁻¹, corresponding to the mean swimming speed during spawning migration. The design of the Blazka‐type swim tunnel was significantly improved, and for the first time the flow pattern of a swim tunnel for fish was evaluated with the Laser‐Doppler method. The velocity profile over three different cross‐sections was determined. It was observed that 80% of the water velocity drop‐off occurred over a boundary layer of 20 mm. Therefore, swim velocity errors were negligible as the eels always swam outside this layer. The fish were able to swim continuously day and night during a period of 3 months in the swim tunnel through which fresh water at 19° C was passed. The oxygen consumption rates remained stable at 36·9 ± 2·9 mg O₂ kg⁻¹ h⁻¹ over the 3 months swimming period for all tested eels. The mean cost of transportation was 28·2 mg O₂ kg⁻¹ km⁻¹. From the total energy consumption the calculated decline in fat content was 30%. When extrapolating to 6000 km this would have been 60%, leaving only 40% of the total energy reserves for reproduction after arriving at the spawning site. Therefore low cost of transport combined with high fat content are crucial for the capacity of the eel to cross the Atlantic Ocean and reproduce.     

Characterization of the cortisol response following an acute challenge with lipopolysaccharide in yellow perch and the influence of rearing density

Two experiments were performed to characterize the corticosteroid response of yellow perch Perca flavescens following an intraperitoneal injection of lipopolysaccharide (LPS) and determine if sustained differences in rearing density alter this response. In the first experiment, yellow perch were injected with LPS (3 mg kg⁻¹), saline, or handled without receiving any injection. Concentrations of cortisol in plasma were elevated in all groups relative to non‐disturbed fish at 1·5 and 3 h after handling but by 6 h after injection the mean concentration of cortisol in plasma from LPS‐injected yellow perch were three to five times higher than fish before injection and significantly larger than groups of fish not treated with LPS. In the second test, yellow perch were held at different rearing densities (9 v . 18-19 kg m⁻³) for 3, 7 and 14 days before injection with LPS (3 mg kg⁻¹). The cortisol response of yellow perch following LPS injection of fish held for 14 days at high density was significantly lower than that of fish held at the low density for the same duration. Additionally a trend of a decreased cortisol response to LPS injection as duration of holding increased was observed among fish held at high density relative to fish held at low density. These data illustrate that the corticosteroid response of yellow perch following LPS injection is distinct from handling alone and that the magnitude of the response is impacted by rearing density.     

Phenolic compounds in peach (Prunus persica) cultivars at harvest and during fruit maturation

Six peach and six nectarine cultivars were evaluated for the phenolic content in their pulp and peel tissues. Chlorogenic acid, catechin, epicatechin, rutin and cyanidin-3-glucoside were detected as the main phenolic compounds of ripened fruits. The concentration was always higher in peel tissue, with average values ranging from 1 to 8 mg g⁻¹ dry weight (DW) depending on cultivar. Of the tested varieties, the white-flesh nectarine 'Silver Rome' emerged as the cultivar with the highest amount of total phenolics. Phenolic compounds were also profiled during fruit growth and ripening in the yellow nectarine cv. 'Stark Red Gold', which showed a decreasing concentration during fruit development in both peel and pulp tissues. Average amounts of total phenolics were approximately 25 mg g⁻¹ DW 60 days after full bloom and decreased to 3 mg g⁻¹ DW at ripening in pulp tissue. Differences among peel and pulp composition show the different dietetic and antioxidant potential of fruits consumed unpeeled and peeled.     

Inactivation of oenological lactic acid bacteria (Lactobacillus hilgardii and Pediococcus pentosaceus) by wine phenolic compounds

Aims:  To investigate the inactivation properties of different classes of phenolic compounds present in wine against two wine isolates of Lactobacillus hilgardii and Pediococcus pentosaceus , and to explore their inactivation mechanism.
Methods and Results:  After a first screening of the inactivation potency of 21 phenolic compounds (hydroxybenzoic and hydroxycinnamic acids, phenolic alcohols, stilbenes, flavan-3-ols and flavonols) at specific concentrations, the survival parameters (MIC and MBC) of the most active compounds were determined. For the L. hilgardii strain, the flavonols morin and kaempferol showed the strongest inactivation (MIC values of one and 5 mg l⁻¹, and MBC values of 7·5 and 50 mg l⁻¹, respectively). For the P. pentosaceus strain, flavonols also showed the strongest inactivation effects, with MIC values between one and 10 mg l⁻¹ and MBC values between 7·5 and 300 mg l⁻¹. Observations by epifluorescence and scanning electron microscopy revealed that the phenolics damaged the cell membrane and promoted the subsequent release of the cytoplasm material into the medium.
Conclusions:  The antibacterial activity of wine phenolics against L. hilgardii and P. pentosaceus was dependent on the phenolic compound tested, and led not only to bacteria inactivation, but also to the cell death.
Significance and Impact of the Study:  New information about the inactivation properties of wine lactic acid bacteria by phenolic compounds is presented. It opens up a new area of study for selecting/obtaining wine phenolic preparations with potential applications as a natural alternative to SO₂ in winemaking.     

Automated sperm morphology analysis in fishes: the effect of mercury on goldfish sperm

This study is the first to examine the morphology of fish sperm using automated sperm morphology analysis (ASMA). The technique was applied to investigate the effect of an environmental pollutant, mercury, on the sperm morphology of goldfish Carassius auratus , and the effects on sperm morphology were compared with those on sperm motility. Goldfish sperm flagellar length was significantly shortened after instant exposure to 100 mg l⁻¹ (368 µM) mercuric chloride, while curvilinear velocity (VCL) and the percentage of motile sperm were significantly decreased at mercuric chloride concentrations of 1 and 10 mg l⁻¹ (3·68 and 36·8 µM), respectively. After 24 h exposure to 0·001 mg l⁻¹ (0·0037 µM) mercuric chloride, flagellar length was significantly reduced in 38% of the spermatozoa. Following exposure to 0·1 mg l⁻¹ (0·37 µM) mercuric chloride for 24 h, however, the majority of spermatozoa (98%), had significantly shortened flagella and increased sperm head length, width and area. Sperm motility was also significantly decreased at 0·1 mg l⁻¹ (0·37 µM) mercuric chloride, probably due to the significantly reduced flagellar length at this concentration. This study shows that the morphological examination of fish sperm by ASMA provides, not only, an excellent tool for monitoring reproductive disruption caused by environmental pollution, but also has applications to other areas of fish reproductive biology, such as cryopreservation and aquaculture.     

Stimulation of biomethanation by Clostridium sp. PXYL1 in coculture with a Methanosarcina strain PMET1 at psychrophilic temperatures

Aim:  Bioaugumentation of low temperature biogas production was attempted by addition of cold-adapted Clostridium and a methanogen.
Methods and Results:  A psychrotrophic xylanolytic acetogenic strain Clostridium sp. PXYL1 growing optimally at 20°C and pH 5·3 and a Methanosarcina strain, PMET1, growing optimally on acetate and producing methane at 15°C were isolated from a cattle manure digester. Anaerobic conversion of xylose at 15°C with the coculture of the two strains was performed, and batch culture methane production characteristics indicated that methanogenesis occurred via acetate through 'acetoclastic' pathway. Stimulation studies were also undertaken to evaluate the effect of exogenous addition of the coculture on biogas yields at 15°C. Addition of 3 ml of PXYL1 at the rate of 12 × 10² CFU ml⁻¹ increased the biogas 1·7-fold (33 l per kg cowdung) when compared to control (19·3 l per kg cowdung) as well as increased the volatile fatty acid (VFA) levels to 3210 mg l⁻¹ when compared to 1140 mg l⁻¹ in controls. Exogenous of addition of 10 ml PMET1 inoculum at the rate of 6·8 ± 10² CFU ml⁻¹ in addition to PXYL1 served to further improve the biogas yields to 46 l kg⁻¹ as well as significantly brought down the VFA levels to 1350 mg l⁻¹.
Conclusions:  Our results suggest that the rate-limiting methanogenic step at low temperatures could be overcome and that biogas yields improved by manipulating the population of the acetoclastic methanogens.
Significance and Impact of the Study:  Stimulation of biomethanation at low temperature by coculture.     

Water‐based measurement of rainbow trout melatonin

Melatonin (MLT) was isolated from water samples using solid phase extraction cartridges and measured by radioimmunoassay. In tanks of rainbow trout Oncorhynchus mykiss , concentrations of MLT in water increased rapidly from <0·1 ng l⁻¹ in the light phase to 0·7 ng l⁻¹ in the dark giving calculated release rates of <1 ng kg⁻¹ h⁻¹ and 15 ng kg⁻¹ h⁻¹, respectively. This cycle in water MLT values corresponds to reported changes in plasma MLT concentrations. The colour of the tanks and a daytime acute handling stress did not affect concentrations of MLT in either the light or dark phase.