Temporal changes in the taxonomic and functional diversity of fish communities in shallow Chinese lakes: the effects of river–lake connections and aquaculture

相似文献   

Is scuba sampling a relevant method to study fish microhabitat in lakes? Examples and comparisons for three European species

Abstract – We compared fish microhabitat use patterns in the littoral zone of a lake using a new direct method (point abundance sampling by scuba, PASS) and the widely used point abundance sampling by electrofishing technique (PASE). We collected microhabitat data for age 0+ roach ( Rutilus rutilus L.), perch ( Perca fluviatilis L.), and pike ( Esox lucius L.). The two methods yielded different results for fish assemblage structure and microhabitat patterns. Using PASE, fish were mainly found in "shelter habitats" such as shallow waters and dense vegetation. It is likely that this behavior is caused by the disturbance of the observer stamping around. Using PASS, fish escapement behavior was rarely observed. Therefore, we concluded that this direct and nondestructive sampling technique can be used to provide an accurate microhabitat estimation of a fish community and is assumed to be more suitable than PASE for fish habitat studies.     

Biogeographic freshwater fish pattern legacy revealed despite rapid socio‐economic changes in China

Understanding drivers of freshwater fish assemblages is critically important for biodiversity conservation strategies, especially in rapidly developing countries, which often have environmental protections lagging behind economic development. The influences of natural and human factors in structuring fish assemblages and their relative contributions are likely to change given the increasing magnitude of human activities. To discriminate natural and human drivers of fish diversity and assemblage patterns in developing countries with rapid socio‐economic development, a dataset of 908 freshwater fish species and 13 metrics including three categories of both natural (i.e., biogeographic) and human drivers (i.e., economic growth, inland fisheries) in China were analysed with machine learning algorithms (i.e., self‐organizing map, random forest). Here, we found that biogeographic drivers explained 21.8% of the observed fish assemblage patterns in China and remained stronger predictors when compared to human drivers (i.e., 15.6%, respectively). Freshwater fish species richness was positively correlated to rainfall, air temperature, surface water area and inland fisheries production but negatively correlated with urbanization. In addition, the strong structuring effects of climatic variables on Chinese fish richness patterns suggested that the fish assemblages could be particularly vulnerable to climate change. Our results showed that natural biogeographic factors still dominate in driving freshwater fish assemblage patterns despite increased human disturbances on aquatic ecosystems in a rapidly developing country. These findings consequently suggested that we should consider both natural (e.g., climate) and human (e.g., urbanization, inland fisheries) factors when establishing aquatic conservation strategies and priorities for developing countries that are experiencing rapid socio‐economic changes.     

石窟河国家级水产种质资源保护区浮游植物群落组成初探

2008年6月对蕉岭石窟河国家级水产种质资源保护区的浮游植物群落组成及水环境状况进行初步调查,结果发现浮游植物(包括变种、变型)5门30属63种。其中,绿藻18属43种,占总种数的68.25%;硅藻5属10种,占总种数的15.87%;蓝藻4属6种;甲藻2属3种;隐藻1种。绝对优势种为扎卡四棘藻(Attheya zachariasi),隐藻(Cryptomonas sp.)、细小隐球藻(Aphanocapsa elachista)和双对栅藻(Scenedesmus bijuga)的优势程度次之。从浮游植物种类组成和多样性指数水平来看,该保护区的水体存在一定程度的富营养化,属中度污染。     

Food risk trade‐off in the Indo‐Pacific humpback dolphin: An exploratory case study

1. Based on optimal foraging theory, animals are expected to maximize foraging benefits whilst minimizing risks. Despite risking being subjected to anthropogenic impacts such as water contamination, marine traffic, and underwater noise, estuaries have been identified as the preferred habitat of the Indo‐Pacific humpback dolphin (Sousa chinensis, IPHD). However, it remains unclear why this vulnerable species favours such risky habitats.
2. Here, an exploratory case study in Zhanjiang estuary, China, was conducted to test the hypothesis that IPHDs select estuarine habitats as a trade‐off that maximizes foraging opportunities whilst minimizing the risk of mortality.
3. The results showed that IPHDs accept greater mortality risks for higher food rewards but select habitats with lower risks when food rewards are similar between two locations.
4. Although this type of information is important for underpinning models for individual dolphins, its principal role is to show environmental protection agencies why IPHDs favour estuaries despite the increased mortality risks.
5. Habitat conservation plans should carefully consider prey stocks, possibly through the presence of marine protected areas near estuaries, as local overfishing may lead vulnerable cetacean populations to take greater risks.

     

Nested patterns of spatial diversity revealed for fish assemblages in a west European river

Abstract –  The longitudinal distribution of fish assemblages across a large west European river basin, the Garonne river (south-west France) were investigated using a self-organising map. This nonlinear statistical method was employed to classify sampling sites according to their species composition. We found three main nested patterns in an aggregated hierarchy: a replacement and succession of species along a gradient without defined boundaries, four main zones of fish assemblages and an upstream-downstream shift of fish communities. We suggest that fish assemblages are too complex to be identified with a single species as in the zonation model, and that the diversity patterns found might be part of the same ecological process influencing fish assemblages on different spatial scales. Thus, discrepancies in the analysis of longitudinal patterns of fish communities in streams may have been basically a matter of local conditions and of conceptual perception.