Simple field methods for monitoring stress and general condition of fish

While physiological stress in fish can be assessed by several laboratory-based methods, many of those methods use very sensitive and expensive instruments, which make them impracticable under field conditions. The objective of this study was to determine the feasibility of detecting stressed states in fish, under Held conditions, using simple but reliable methods. The first set of experiments were conducted in the laboratory, where a standard handling stressor was applied to juvenile coho salmon, Oncorhynchus kisutch (Walbaum). Results of blood samples analysed by both laboratory-based and portable methods (e.g. glucometers for diabetic patients) were in good agreement. The second set of experiments focused on field-testing the most promising methods based on the laboratatory tests. Production lots of Atlantic salmon. Salmo salar L., at commercial fish farms were sampled to assess stress and health status with the selected field techniques, from the swim-up to smolting stages. The measured variables included: blood glucose, protein, haemoglobin concentrations: haematocrit: erythrocyte and lymphocyte numbers: and an autopsy-based health profile, which involved the internal and external examination of the body for texture and colour. In addition to establishing resting, or normal, values for each variable under field conditions, blood glucose levels were observed to increase significantly at 4 h after a stressful event (e.g. grading, handling) using these field methods. Some of these field techniques were found to be reliable indicators of stress in fish and have potential for use in aquaculture facilities and field monitoring programmes.     

Unreduced gamete in interspecific hybrids in the Festuca/Lolium complex

Self-sterile interspecific hybrids between diploid Lolium perenne and either Festuca arundinacea or F. gigantea (both hexaploids) set some seeds when subjected to a heavy pollen cloud from the amphiploids derived from the hybrids. All the progeny were octoploid and were formed from the fertilization of unreduced gametes in the F₁ hybrid by amphiploid pollen. The significance of the results in relation to breeding efforts within the Lolium/Festuca complex is discussed.     

Variation in thylakoid proteins and photosynthesis in Syrian landraces of barley

Summary Barley breeders at ICARDA have observed that genotypes adapted to dry regions have leaves which are lighter in colour than those of unadapted ones. We measured photosynthesis, chlorophyll content and chlorophyll a:b ratios in two sets of genotypes which had previously been observed to have either light green or dark green leaves when grown in the field. Thylakoid membranes were also extracted and the proteins analysed on SDS-PAGE gels.The light leaf colour was associated with a higher chlorophyll a:b ratio. This was a measure of a reduction in the amount of antenna chlorophyll compared to that in the core complex of PSII. Genotypes with light green leaves had consistently less chlorophyll per unit leaf area and lower photosynthetic rates per unit area than those with dark green leaves.It is suggested that these features of light green leaves may confer the ability to adapt to high levels of irradiance under drought conditions. This ability may result from a high rate of photosynthetic electron transport through each PSII reaction centre, thus reducing the risk of damage from the overexcitation of these centres.     

Investigation of sodium monofluoroacetate (1080) bait shyness in wild brushtail possum (Trichosurus vulpecula) populations

Bait shyness is a significant threat to the sustainable control of vertebrate pests. New Zealand's foremost vertebrate pest is the introduced brushtail possum (Trichosurus vulpecula). Bait shyness was identified in two wild possum populations by comparing the consumption of two non-toxic bait types before and after each population was presented with one of the bait types containing the toxin sodium monofluoroacetate (1080). Before poisoning, approximately 60% of total bait consumption was of the type which 1080 was later presented in, whereas after poisoning this bait type made up only 2-4% of total consumption. This shyness persisted for at least 11 weeks in one of the populations. No individual component (bait base, cinnamon lure or green dye) of the toxic bait could be isolated as the primary cue eliciting bait shyness as the response. Possible means of overcoming bait shyness are discussed in light of these findings.     

A Threshold Model for Heron Productivity

We demonstrate the potential of conditionally Gaussian state-space models in integrated population modeling, when certain model parameters may be functions of previous observations. The approach is applied to a heron census, and the data are best described by a model with three population-size thresholds which determine the population productivity. The model provides an explanation of how the population rebounds rapidly after major falls in size, which are characteristic of the data. By contrast, a simple logarithmic regression of productivity on population size was not significant. The results are of ecological interest, and suggest hypotheses for further investigation. Supplementary figures are available online.     

Effects of Rice Variety and Growth Location in Cambodia on Grain Composition and Starch Structure

The effects of variety and growth location on grain composition and starch structures were investigated using three rice （Oryza sativa L.） cultivars （Phka Romduol, Sen Pidao and IR66） with different amylose contents. All the three cultivars were planted in three different agro-climatic zones （Phnom Penh, Coastal and Plateau） of Cambodia. The protein content of polished grains increased when rice was planted at a location with higher average temperature, but their lipid content decreased. The amylose content and degree of branching were not greatly affected by the minor temperature differences among the growing locations. Starch fine structures characterized by the chain-length distribution were significantly different among the cultivars, but not significantly among different locations. The results suggested that protein and lipid biosyntheses were more sensitive to the environmental temperature than that of starch in rice grains.