Stress in African catfish (Clarias gariepinus) following overland transportation

Of the many stressors in aquaculture, transportation of fish has remained poorly studied. The objective of this study was therefore to assess the effects of a (simulated) commercial transportation on stress physiology of market-size African catfish (Clarias gariepinus). Catfish weighing approximately 1.25 kg were returned to the farm after 3 h of truck-transportation, and stress-related parameters were measured for up to 72 h following return. Recovery from transportation was assessed through blood samples measuring plasma cortisol, glucose and non-esterified fatty acids (NEFA) and gill histology. Also, the number of skin lesions was compared before and after transport. Pre-transport handling and sorting elevated plasma cortisol levels compared to unhandled animals (before fasting). Plasma cortisol levels were further increased due to transportation. In control fish, plasma cortisol levels returned to baseline values within 6 h, whereas it took 48 h to reach baseline values in transported catfish. Plasma glucose and NEFA levels remained stable and were similar across all groups. Transported catfish did not, on average, have more skin lesions than the handling group, but the number of skin lesions had increased compared to unhandled animals. The macroscopic condition of the gills was similar in control, transported and unhandled catfish; however, light microscopy and immunohistochemistry revealed atypical morphology and chloride cell migration normally associated with adverse water conditions. From our data, we conclude that transportation may be considered a strong stressor to catfish that may add to other stressors and thus inflict upon the welfare of the fish.     

An improved radioimmunoassay for measurement of pepsinogen in porcine blood samples

The study was conducted to develop a sensitive and specific radioimmunoassay (RIA) for the measurement of pepsinogen in porcine serum, and to use this test for the determination of pepsinogen concentrations in serum samples from fetuses and pigs of different ages. Compared to a previously described RIA, major improvements were made concerning the use of specific polyclonal antibodies and the use of an appropriate buffer. The assay was able to detect pepsinogen concentrations of >/=0.2 ng/mL. The recovery of pepsinogen was close to 95%. The intra-assay coefficients of variations ranged between 3.9 and 7.5% whereas the interassay ranged between 8.8 and 11.9%. These percentages correspond to a satisfactory accuracy and reproducibility of the assay. No cross-reactions were observed with the main commercially available products of the aspartic proteases family except porcine pepsin cross-reacted over 62.5 microg/mL. Pepsinogen concentrations increased steadily with increasing age of the fetuses and the pigs (P<0.05). Pepsinogen concentrations (+/-SE) in fetuses of 90-100 (n=24) and 100-110 days of pregnancy (n=36) were 0.5+/-0.1 and 5.3+/-1.3 ng/mL, respectively. In pigs of 21, 98, and 213 days of age, the pepsinogen concentrations were 290.6+/-10.8, 343.1+/-17.9 and 383.5+/-15.3 ng/mL, respectively. The results demonstrate that RIA is accurate and can be used easily to assess pepsinogen concentrations in pig sera. The test may constitute a valuable tool in epidemiological surveys and in studies related to gastric diseases in pigs.     

Spatial heterogeneity of soil solution chemistry in a mature Norway spruce (Picea abies (L.) Karst.) stand

The determination of the average soil solution concentrations in forest soils is hindered by the spatial heterogeneity of the soil conditions and the stand structure on all scales. The aim of this paper is to investigate the spatial heterogeneity of the soil solution chemistry within a mature stand of Norway spruce and to evaluate the implication of this heterogeneity for the sampling design for soil solutions. The site is a 140 years old Norway spruce stand of 2.5 ha located in the German Fichtelgebirge at 800 m elevation on granitic, deeply weathered bedrock. At 35 cm soil depth, 59 ceramic suction lysimeters (5 cm length, 2 cm diameter) were installed in a systematic grid of 25 · 25 m and soil solution was sampled at 3 dates in June and July 1994. The solutions were analysed for major cations and anions. Semi-variance of the concentrations at a given date revealed no systematic spatial patterns. The coefficients of variance of the element concentrations were between 36 and 298% with highest values for NH₄ ⁺-N. The implications of the observed heterogeneity for the appropriate number of replicates was investigated by Monte Carlo simulations. As an example, the probability that the measured average concentration of SO₄ ^2?-S is outside a ±10% range (related to the ‘true’ 59 lysimeter average) is about 68% if only 3 replicates would have been used, 41% with 10 replicates and 25% with 20 replicates. Due to the generally large spatial heterogeneity of the soil solution chemistry in forest soils the number of lysimeters used must be carefully adjusted to site conditions and the specific question.