The influence of pelagic habitat selection and interspecific competition on productivity of juvenile walleye pollock (Theragra chalcogramma) and capelin (Mallotus villosus) in the Gulf of Alaska

Here we investigate processes affecting productivity of capelin and walleye pollock in the Gulf of Alaska. We examine pelagic habitat selection by comparing the distribution of juvenile fish and their prey with oceanographic properties and we evaluate the potential for interspecific competition by comparing diets and measures of foraging. The primary field study was conducted in Barnabus Trough, Kodiak Island, Alaska, during September 2005. The distribution of fish was assessed acoustically and trawls were used to collect individual fish for stomach content analyses. Physical and biological data were collected with conductivity–temperature–depth probes and zooplankton tows. Age‐0 pollock were distributed in cool waters offshore of a mid‐trough front, coincident with the distribution of euphausiids, their preferred prey. In contrast, capelin and their prey (copepods) were distributed throughout the trough. We observed that sympatric capelin (occurring with pollock) often had reduced foraging success compared to allopatric capelin (occurring alone). Results of a bioenergetic model also suggest that the exclusion of capelin from foraging on euphausiids can have negative consequences for capelin growth.     

MORPHOLOGICAL,ANATOMICAL AND BIOCHEMICAL EFFECTS OF PROPACHLOR ON SEEDLING GROWTH*

Summary. The root and shoot growth of oat (Avena saliva L.) and squash (Cucurbita maxima Duchesne) was reduced in proportion to propachlor concentration. Corn (Zea mays L.) root growth was inhibited only by concentrations of 16 ppm and higher. Cell division in onion (Allium cepa L.) root tips was reduced by propachlor and totally inhibited by 16 ppm. Auxin-induced cell elongation of oat coleoptiles was inhibited in proportion to propachlor concentration. Propachlor treatment prevented the normal senescence of squash cotyledons by inhibiting the autolysis of proteinaceous and lipid reserves. Effets morphologiques, anatomiques et biochimiques du propachlore sur la croissance des plantules Riisumi.     

防病促生枯萎病拮抗菌“98-Ⅰ”对4种枯萎病防治效果研究

经 8年系统试验研究从 330个细菌菌株中筛选出 1株防病促生枯萎病拮抗菌“98 Ⅰ” ,经鉴定属蜡质芽孢杆菌。该菌对黄瓜枯萎病、西瓜枯萎病、青椒枯萎病和番茄枯萎病 4种土传病害均有显著防治效果 ,其平皿孢子萌发抑制率分别为 79 2 %、75 1%、72 3%和 95 7% ,且该菌对多种蔬菜有促生和促进种子发芽功效。     

Mixed Signals in the Job Training Partnership Act

The Job Training Partnership Act of 1982 was developed to train the disadvantaged for work or better jobs. The Act that passed targeted the economically disadvantaged but stressed efficiency in the operation of the program. Program performance standards were established, and local Private Industry Councils (PICs) were developed to operate the program and to involve local business in JTPA training. Critics argued that this structure resulted in “creaming” of participants to the exclusion of the most disadvantaged workers. We test the “creaming” hypothesis using data on JTPA participants in Tennessee in 1987 and a sample of disadvantaged workers in Tennessee extracted from the Current Population Surveys. We find that racial and welfare targets are met but that the most able among those groups are chosen for help. We also find some evidence of “channeling.” The most disadvantaged groups are less likely to receive the most successful type of training — on-the-job training. Finally, we present alternative strategies to encourage PICs to do less “creaming,” and we make predictions about their likely success.     

Mass larval mortalities in giant freshwater prawn, Macrobrachium rosenbergii de Man, cultured in Malaysian modified static'green water' systems

Abstract. Repeated mass mortalities occurred in larval Macrobrachium rosenbergii de Man reared in modified static'green water' systems in two commercial hatcheries in Malaysia. Mean age of larval cultures at the time of mass mortalities was 164 days, or at larval stage 8 or 9. Gross signs, wet mount preparation pathology and/or histopathology revealed bacterial necrosis, midcycle larval disease-like and idiopathie muscle necrosis associated tissue changes, in some cases together with uncharacterised fungal infections. Strict attention to hatchery hygiene and the sanitary lot technique was effective in reducing the occurrence of mass larval mortalities.     

欧拉羊与乔科羊杂交后代屠宰性能分析

用欧拉羊杂交改良乔科羊,生产的欧乔杂交F1代羔羊,18月龄时公、母羊体重增加9.06kg和3.77 kg,比对照组分别提高了20.92%和9.08%。试验组F1代18月龄公、母羊体重、体高、胸围及公羊体长极显著的高于对照组(P(0.01);母羊体长显著高于同期对照组母羊(P(0.05)。屠宰试验结果表明,欧乔杂交F1代18月龄公、母羊屠宰前活重比同龄的乔科羊对照组后代分别高8.94 kg和6.00 kg,胴体重比同龄的乔科羊对照组后代分别高4.88 kg和3.27 kg,差异极显著;屠宰率比同龄的乔科羊对照组后代分别高1.43%和1.10%,差异不显著。     

Paleontology and Chronology of Two Evolutionary Transitions by Hybridization in the Bahamian Land Snail Cerion

The late Quaternary fossil record of the Bahamian land snail Cerion on Great Inagua documents two transitions apparently resulting from hybridization. In the first, a localized modern population represents the hybrid descendants of a 13,000-year-old fossil form from the same area, introgressed with the modern form now characteristic of the adjacent regions. In the second case, a chronocline spanning 15,000 to 20,000 years and expressing the transition of an extinct fossil form to the modern form found on the south coast was documented by morphometry of fossils dated by amino acid racemization and radiocarbon. Hybrid intermediates persisted for many thousands of years.