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Mortality in eiders (Somateria mollissima) on the Ythan estuary, Aberdeenshire, and elsewhere, has been claimed to be associated with the spiny-headed worm, Profilicollis botulus. Eiders acquire the disease by eating crabs (Carcinus maenas) infected with the cystacanth stage of the parasite. A detailed quantitative study was undertaken to elucidate some of the factors which control the abundance of the parasite in its intermediate and definitive hosts. During 1979-81 the P. botulus burdens in eiders and crabs were regularly monitored. Eiders were either taken alive off the estuary, or off the nest, and sacrificed, or found dead on the shore line. Crabs were caught in traps at two sites on the estuary. Female P. botulus in eiders were assigned to one of five categories according to the state of development of the eggs contained within their pseudocoelom. To estimate the size range and numbers of crabs eaten by eiders, crab chelipeds, or parts of chelipeds, were recovered from eider faeces collected monthly from roost sites. Regression equations relating certain cheliped dimensions to crab carapace width were used to estimate the size range eaten. The numbers of chelipeds per unit weight of faeces, equivalent to the quantity excreted per eider per day, was used to estimate the numbers of crabs eaten. Daily P. botulus infection rates in eiders were calculated by combining the quantitative data on crab intake by eiders with the cystacanth burdens in the crabs. Captive eiders, reared from eggs, were used to determine the age, days post-infection, of the five categories of female parasites. These development times were combined with the burdens found in the eiders sampled from the estuary to produce a static life-table of the mortality of female P. botulus. From this, estimates of the parasite's establishment rate, mortality rate and lifespan were obtained.

Egg weight and fecundity of Clyde spring-spawning and autumn-spawning herrings, Clupea harengus L., in the nothern North Sea and North Minch in different years were analysed. For Clyde spring-spawning herring high variation in egg weight was found and it was attributed to more than one spawning group spawning in the area. Annual variation in fecundity between 1963-1984 was found. Fecundity in 1984 was found to be about 10% higher than previous years. For autumn-spawning herring, fish spawn in the North Minch produce about 1.18 times heavier eggs than those spawning in the northern North Sea. Regional annual variation in fecundity between 1971-1984 was found. In 1984 fecundity of samples collected from Shetland was 1.12 higher than those of North Minch. Fecundity indices for Shetland samples were found to be 1.23 to 1.77 higher in 1984 than 1971-1973. Annual variation between 1971-1973 was also found. It was concluded that fecundity is a potential contributor to population regulation not necessarily related to population density. Monthly analysis of energy content of soma and gonad was carried out for Clyde spring-spawning herring. Differences in the magnitude and timing of energy allocated to the gonad was found between sexes. Energy budget was prepared for each sex at ages 2 and 3. No deficient of energy during winter was apparent due to gonad maturation and metabolic activity. Routine metabolic rate was measured in a group of herring in a respirometer. Oxygen consumption was estimated to be 31.3, 93.3 and 278.6 mgO2 kg-1 h-1 at 5, 10 and 15oC respectively. Standard oxygen consumption was derived from oxygen consumption and theoretical swimming speed to be 20.4, 59.5 and 164.8 mgO2 kg-1h-1 at 5, 10 and 15oC.

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Population dynamics of ducks is a complex process influenced by both biotic and abiotic factors, and good understanding about the mechanisms behind this process is needed not only for the management of duck harvest but also for the conservation of wetland, which is under threat in the face of land change and climate warming. Basic time series analysis techniques, such as correlogram, partial correlogram and periodogram, cluster analysis and partial least squares regression (PLSR) are applied to the long-term breeding population data gathered by Waterfowl Breeding Population and Habitat Survey and monthly weather data from Environment Canada in order to explore the pattern in the duck abundance data and the effect of local weather on population dynamics of ducks. Results of above analysis show that the duck abundance of previous years has short but strong correlation with the duck abundance of following years suggesting a large part of variability in duck abundance is explained by the abundance of previous years, especially that of last year. There is also clear periodic pattern in the duck abundance data, but the length of the cycle varies both for duck species and ecozones suggesting separating duck species and ecozones for analysis is necessary. The effects of weather on duck populations appear weak or absent in most PLSR models; this is consistent with previous studies. More detailed information, such as age structure of the duck populations and interspecific interactions, will be needed for future modeling. Among the small number of PLSR models exhibiting the weather effect, results suggest potential mechanisms, such as the impact of weather on recharge and discharge of wetland basins and nest failure caused by flooding.