Predation by seals on salmonids in two Scottish estuaries

Detailed observations of the behaviour of harbour seals, Phoca vitulina L., at sites within the estuaries of the Rivers Dee and Don, in north-eastern Scotland, were made over two full years between 1993 and 1996. Small numbers of grey seals, Halichoerus grypus Fab., were also present. The presence of seals within the estuaries was strongly related to season, with maximum numbers observed in winter and early spring; seals were virtually absent in June and July. The River Don was used largely as a haul-out site, while the River Dee was used predominantly as a foraging site, although it was not possible to determine whether the same seals were using the two estuaries. More seals were hauled-out on the River Don during twilight and dark than in daylight. The seals were observed to eat mostly salmonids, Salmo salar L. and S. trutta L., unidentified roundfish and flounder, Pleuronectes flesus L. The otoliths identified in scats collected at the mouth of the River Don belonged to marine species indicating that the seals were also feeding outside the estuaries. A minimum estimate is given of the numbers of large salmonids eaten in each river during the course of the year. Although no information was available on the numbers of salmonids using the rivers or the reproductive status of the fish eaten by the seals, as a cause of mortality, seal predation on large salmonids in estuaries is apparently an order of magnitude less important than mortality caused by angling within the river.     

Fish meal replacement by plant and animal by-products in diets for the Australian short-finned eel, Anguilla australis australis (Richardson)

In this experiment, 23% of fish meal protein was replaced with protein from Australian soybean meal (SBM), lupin meal (LM), corn gluten meal (CGM) and meat meal (MM) in nutritionally balanced experimental diets. Growth and growth efficiencies of juvenile Australian short‐finned eel Anguilla australis australis (Richardson) elvers (2.23±0.4‐g average wet weight) were compared. Elvers were fed twice a day to a total of 5% body weight per day for 63 days. Total weight gain (g), specific growth rate (% day^?1), protein efficiency ratio (%) and productive protein value (%) were significantly higher (P<0.05) for elvers fed the MM diet than for those fed the LM diet. There were no differences in diurnal ammonia‐nitrogen excretion rates. However, diurnal urea‐nitrogen excretion rates were significantly (P<0.05) affected by diet and rates were two to three times higher for all diets, except CGM, 4 h following the afternoon feed. Diet significantly affected apparent digestibility (AD); ADs of protein for SBM and LM were significantly (P<0.001) higher than for control diet, CGM and MM; AD of energy for LM was significantly (P<0.05) lower than for all the other diets. Fish meal protein was replaced by CGM, SBM and MM without compromising growth rates of the Australian short‐finned eel. However, whole lupin seed meal (LM) depressed growth and growth efficiencies most likely because of the high indigestible carbohydrate content.     

Wheat-sensitive enteropathy in Irish setter dogs: possible age-related brush border abnormalities

The pathogenesis of a wheat-sensitive enteropathy was explored in a litter bred from two Irish setters with a naturally occurring enteropathy. Jejunal biopsies from all eight progeny exhibited morphological changes comparable to those in the parents, while biochemical abnormalities appeared to be related to age. In biopsies obtained from the first group of four dogs at eight months, the activities of alkaline phosphatase and of leucyl-2-naphthylamidase were almost undetectable while disaccharidases were unaltered. In contrast, analytical subcellular fractionation of biopsies obtained from the second group of four dogs at nine months showed that specific activities now reflected a major deficiency of brush border alkaline phosphatase, and normal brush border leucyl-2-naphthylamidase accompanied by elevated soluble activity. Further studies are indicated to determine whether these findings represent an age-related abnormality affecting specific microvillus membrane proteins.     

Plasma concentrations of luteinising hormone and body weights during somatic maturation in intact and castrated Australorp cockerels from a line of hens selected for increased ovulation rate

1. Plasma concentrations of luteinising hormone (LH), comb size and body weight were measured between 46 and 208 d of age in intact and castrated cockerels from lines of selected and control Australorp domestic chickens. The selected line had been selected for increased rate of lay by reducing oviposition intervals within sequences. The cockerels were reared and maintained on 15.25 h light/d. 2. Concentrations of plasma LH in the intact control cockerels were low in the 'immature' phase (less than 100 d old) and increased during the 'mature' phase (older than 175 d) with a peak occurring when the testes are beginning to grow at the onset of the 'mature' phase. In comparison with the control line of cockerels, the selected line had significantly higher plasma LH concentrations at the onset of the 'mature' phase. Selection had no effect on the mean concentration of plasma LH in either the immature phase or a few weeks after the onset of the mature phase. 3. There was no effect of selection in sibling females for higher rates of lay on changes in comb size or body weight during sexual maturation in the intact cockerels. 4. Castration at 45-46 d of age resulted in increased plasma LH concentrations and no comb growth. Plasma LH concentration increased progressively between 40-208 d. There was no difference between the two lines of cockerels in plasma LH concentration or rate of body growth after castration. 5. It is concluded that selection of females for a change in the rate of egg production has resulted in increased plasma LH concentrations in sibling males around the onset of sexual maturation. Selection appears to have caused this effect by altering an unidentified component of the inhibitory feedback mechanism which controls the tonic secretion of LH.     

Assessment of Suitable Porcine Semen for Freezing,According to the Ejaculate Characteristics in the Iberico × Landrace Breed

A total of 35 ejaculates were studied in order to assess the suitability of porcine semen for freezing according to the ejaculate characteristics. The effects of the freezing procedure were identified; a decrease in motility and acrosome quality was found after thawing. The best results on motility were linked to the ejaculates with a volume of less than 100 ml of the sperm‐rich fraction, a concentration lower than 450 × 10⁶ spermatozoa/ml and an agglutination score below 2. However, the best normal apical ridge (NAR) was found when the volume of the sperm‐rich fraction was greater than 150 ml. For this reason, an intermediate volume of the sperm‐rich fraction of the ejaculate for the best motility and the best NAR, a concentration lower than 450 × 10⁶ spermatozoa/ml and a rate of agglutination below 2 should provide the best quality after freezing. This study also attempted to determine whether a positive effect of ejaculate selection on the overall freezing performance might be expected.     

Phenological development in spring cereals: response to temperature and photoperiod under northern conditions

Phenological development of spring cereals was investigated using observations from several sites in Finland during the period 1970–1990. Different mathematical models which relate temperature to development rate were examined to predict the duration of phenological phases. A photoperiodic response of plant development before heading was also tested. For all phases the relationship between temperature and development was approximately linear. There was no significant response of plant development to photoperiod. This was explained by consistently long photoperiods in the observational material. Parameters for a linear model were derived from a regression analysis of mean development rate of each phase against mean temperature. However, a different response may occur under higher or lower temperatures or under shorter photoperiods than those experienced here.     

Sample size and power determination for detecting interactions in mixtures of chemicals

In the analysis of mixtures of drugs/chemicals it is often of interest to test for the presence of interaction. If the hypothesis of no interaction (additivity) is not rejected, then the analyst may reasonably claim additivity if and only if the study is powered to a desired (e.g., biologically meaningful) level. The objective of this article is to address the sample size and power issues related to testing the hypothesis of additivity at specified mixture points. The study of disinfectant by-products (DBPs) found in drinking water, described in earlier literature, is used to illustrate the procedures for estimating power and sample sizes for detecting interactions at specified mixtures. The four trihalomethanes used in the study are bromodichloromethane (BDCM), chlorodibromomethane (CDBM), chloroform (CHCl₃), and bromoform (CHBr₃)     

Apollo 14 and apollo 16 heavy-particle dosimetry experiments

Doses of heavy particles at positions inside the command modules of Apollo missions 8, 12, 14, and 16 correlate well with the calculated effects of solar modulation of the primary cosmic radiation. Differences in doses at different stowage positions indicate that the redistribution of mass within the spacecraft could enhance safety from the biological damage that would otherwise be expected on manned, deep-space missions.