Río de la Plata voyagers: Deciphering the migration ecology of a vulnerable marine catfish (Genidens barbus) in a large subtropical river (lower Uruguay River)

1. Genidens barbus is a vulnerable marine migrant catfish with low fecundity, a complex life cycle (i.e. mouth breeding), and is the target of industrial and artisanal fisheries of several countries. This species regularly migrates from marine to freshwater environments of the south-western Atlantic.
2. The aim of this work was to delve deeper into the migration ecology of G. barbus, characterizing both its timing and potential environmental drivers. Furthermore, aspects of the population structure and reproduction of migrants in the lower Uruguay River were studied and the presence of juveniles in the adjacent estuarine recruitment area was evaluated.
3. Data from 11 years (2008–2018) of records of adult G. barbus captured by artisanal fisheries were used alongside relevant environmental variables that were recorded monthly. Reproductive biology (i.e. sex ratio, gonadosomatic index, fecundity, and oocyte size) was analysed for a period of 3 years (2016–2018). The juvenile abundance in the Río de la Plata estuary was evaluated seasonally.
4. A total of 935 adult individuals of G. barbus were captured, representing a total biomass of 3,123 kg. The migration timing was from early spring to early summer. The abundance of migrants strongly increased with river discharge, suggesting that this variable regulates the upriver migration. Furthermore, pre- and post-spawn females and males displaying mouth breeding were recorded during the study period, confirming G. barbus reproduction in the lower Uruguay River.
5. The results obtained suggest that G. barbus ascend to spawn in the freshwater environments upstream from the mouth of the Uruguay River. Then, adult males incubate and carry the embryos downstream, releasing juveniles in the Río de la Plata estuary.
6. This relevant information will help with the implementation of effective management polices (e.g. fishing restrictions during the reproductive period) for the presently unregulated fishery of this vulnerable species in the lower Uruguay River.

     

越冬圆叶莴苣品种比较试验

为筛选出适合武汉市越冬栽培的莴苣品种,对4个越冬圆叶品种进行品种比较试验,结果表明,华笋在株高、叶片数、笋茎长、茎粗、抗病性等方面优势明显;熟性上,华笋比对照品种雪里松晚7 d左右;净菜率上,华笋为62.2%,雪里松为66.7%;产量方面,华笋比雪里松显著增产23.0%;耐寒性和抗病性方面,华笋均表现最好,华笋的冻害指数和感病指数分别为40.8和62.0,雪里松为51.0和77.5,差异均达显著性水平;其他2个品种的综合性状表现均较华笋差。因此,华笋在越冬品种栽培上优势较大,具有极大的推广价值。     

环青海湖地区草地生态环境质量评价方法

按照分层综合评价方法,确定环湖地区草地生态环境质量评价分层指标和各级分层指标权重系数,选定具体评价因子并进行分级,设定分级分值,建立环湖地区草地生态环境质量评分模式并作出质量分级评述。