Spatial and temporal patterns of vertical distribution for three planktivorous fishes in Lake Washington

Abstract – We sampled three limnetic fish species: juvenile sockeye salmon (Oncorhynchus nerka), three‐spine stickleback (Gasterosteus aculeatus) and longfin smelt (Spirinchus thaleichthys) in Lake Washington to quantify species‐specific patterns of diel vertical migration (DVM). Catch‐per‐unit‐effort data analysed from 15 years of midwater trawling documented seasonal and diel differences in vertical distributions for each species. These results were consistent with the hypothesis that the patterns of DVM in Lake Washington were affected by life history, size and morphology. Sockeye salmon showed clear DVM in spring but essentially no DVM in fall, remaining in deep water, whereas three‐spine sticklebacks were prevalent at the surface at night in both seasons. In fall, distribution patterns may be explained by differences in thermal performance (e.g., sticklebacks favouring warm water), but the patterns were also consistent with inter‐specific differences in predation risk. Younger sockeye salmon and longfin smelt were present in greater proportions higher in the water column during dusk and night periods than older conspecifics. Compared with sockeye salmon, the greater use by three‐spine sticklebacks of surface waters throughout the diel cycle during weak thermal stratification in spring was consistent with the hypothesis that sticklebacks’ armour reduces predation risk, but use of this warmer, metabolically beneficial stratum may also have promoted growth. This study illustrates variation in the vertical distribution of three sympatric planktivores and offers broader implications for the DVM phenomenon and applied lake ecology.     

群养鸡谨防痢菌净中毒

痢菌净学名乙酰甲喹,是我国研制的具有自主知识产权的兽用抗菌药品.本品抗菌谱广,不易产生抗药性,价格低廉,在畜牧养殖业上应用广泛.但在使用过程中常因超剂量应用导致中毒现象发生,造成不应有的损失.本文从药品特性、中毒症状、剖检变化、治疗、中毒原因分析等五个方面对群养鸡痢菌净中毒做了详尽阐述,以期基层兽医临床工作者有所借签.     

RADIOGRAPHIC DIAGNOSIS OF MECHANICAL OBSTRUCTION IN DOGS BASED ON RELATIVE SMALL INTESTINAL EXTERNAL DIAMETERS

Mechanical obstruction is a frequent cause of acute vomiting in dogs requiring prompt diagnosis to improve patient management and prognosis. The purpose of this retrospective study was to compare small intestinal radiographic characteristics in dogs with versus without mechanical intestinal obstruction. Fifty dogs with gastrointestinal clinical signs and abdominal radiographs were recruited from hospital record archives and assigned to groups (group 1, obstructive, n = 25; group 2, nonobstructive n = 25). Abdominal radiographs were randomized and independently interpreted by three examiners who were unaware of group status. Intestinal dilation was subjectively scored based on distribution (segmental, regional or diffuse), and severity (absent, mild, moderate or severe). Small intestinal maximal diameter (SI_max), L5 vertebral body height, small intestinal minimal diameter (SI_min), and an estimated average of small intestinal diameters (SI_ave) were measured and three ratios were calculated: SI_max/L5, SI_max/SI_min, and SI_max/SI_ave. Segmental dilation was more prevalent in obstructed dogs for all examiners (P ≤ 0.03) and most nonobstructed dogs had no dilation (P ≤ 0.05). All ratios were higher in obstructed dogs (P < 0.002). Subjective dilation scores and ratio measurements had low interobserver agreement (absent to fair, with kappa values between ?0.06 and 0.57) and reproducibility (coefficients of 0.35–0.61). Findings indicated that dogs with SI_max/L5 ≤ 1.4, SI_max/SI_min ≤ 2, and SI_max/SI_ave ≤ 1.3 values are very unlikely to be mechanically obstructed; dogs with SI_max/L5 ≥ 2.4, SI_max/SI_min ≥ 3.4 and SI_max/SI_ave ≥ 1.9 are very likely obstructed, particularly if segmental dilation (less than 25% of the small intestine) is present. Dogs with ratios falling between these thresholds may need further testing unless other signs justify surgical exploration or endoscopy.     

Cretaceous cold-seep communities and methane-derived carbonates in the canadian arctic

Lower Cretaceous cold-seep fossil assemblages have been found in the Canadian Arctic Archipelago. Serpulid worm tubes and bivalves are most abundant in these communities; in contrast, fossils are scarce in the surrounding strata. The fossils are contained in an isotopically light (delta(13)C = -25 to -50 per mil) carbonate rock groundmass that is interpreted to have formed from bacterial oxidation of methane. The rocks were deposited at intermediate depth (相似文献