Spatial and temporal variation of fish assemblages in a subtropical small stream of the Huangshan Mountain

Spatial and temporal variation of fish assemblages were investigated seasonally from May 2007 to February 2008across 11 study sites in a subtropical small stream, the Puxi Stream, of the Huangshan Mountain. Along the longitudinal gradientfrom headwater to downstream, fish species richness and abundance increased gradually, but then decreased significantly at thelower reaches. The highest species richness and abundance were observed in August and the lowest in February. Based on analysisof similarities (ANOSIM), fish assemblages were significantly different in spatial variation but not in temporal variation. Althoughdifferences were observed both among sites and among stream orders, the lower R value in order-variation suggestedstream order was not the optimal factor explaining the spatial variation of fish assemblages. In addition, dam construction did notsignificantly alter fish assemblages in the sites adjacent to and immediately downstream to dams. Using cluster analysis andnon-metric Multi Dimensional Scaling analysis (NMS), assemblages were separated into three groups at a Bray-Curtis similarityvalue of 42%: the upper, middle and lower groups. Following analysis of similarity percentages of species contributions (SIMPER),shifts in occurrence or abundance of S. curriculus, Z. platypus, R. bitterling and A.fasciatus contributed most to the differencesamongst the three groups. Standard Deviation Redundancy Analysis (RDA) suggested that habitat structure (such as elevation,substrate, and flow velocity) contributed to the spatial and temporal pattern of fish assemblages in the Puxi Stream. In conclusion,the fish assemblages in Puxi Stream presented significant spatial but not temporal variation. Human disturbance has perhapsinduced the decrease in species diversity in the lower reaches. However, no significant change was observed for fish assemblagesin sites far from and immediately downstream from low-head

Age,growth and reproduction of Sarcocheilichthys nigripinnis from the Qingyi Stream in the Huangshan Mountains

Identifying the life-history strategies of fish and their associations with the surrounding environment is the basic foundation in the conservation and sustainable utilization of fish species.We examined the age,growth,and reproduction of Sarcocheilichthys nigripinnis using 352 specimens collected monthly from May 2009 to April 2010 in the Qingyi Stream.We found the sex ratio of this study population was 0.58:1(female:male),significantly different from expected 1:1.Females and males both comprised four age groups.The annuli on the scales were formed during February and March.No obvious between-sex difference was observed in length-weight and length-scale-radius relationships.The total length in back-calculation significantly increased with age for both sexes,but did not differ significantly at each age between the two sexes.An inflection point was observed in the growth curves given by the von Bertalanffy growth function for total weight.At this inflection point,fish were 3.95 years.Both sexes reach their 50% sex maturity at age 2,when females and males were 94.7 mm and 103.0 mm total length.The temporal pattern of the gonado-somatic index corresponded to a spawning period that occurred from April through July.The non-synchronicity of egg diameter in each mature ovary during the breeding period suggested these fish may be batch spawners.The absolute fecundity increased significantly with total length and weight,whereas no significant correlation was observed between the relative fecundity and body size.

Influences of local habitat, tributary position, and dam characteristics on fish assemblages within impoundments of low-head dams in the tributaries of the Qingyi River, China

Low-head dam impoundments modify local habitat and alter fish assemblages; however, to our knowledge, the pattern of how fish assemblages in the impoundments relate to local habitat, tributary position, and dam characteristics is still unclear. We used data collected in 62 impoundments created by low-head dams Jn headwater streams of the Qingyi River, China, to examine relationships between fish assemblages and local habitat, tributary position, and dam characteristics. We also assessed the relative importance of the three groups of factors in determining fish species richness and composition. Linear regression models showed that fish species richness was related to substrate heterogeneity, confluence link, and dam number upstream. Redundancy analysis showed that fish species compositions were influenced by substrate heterogeneity, confluence link, dam height, dam numbers upstream and downstream. Overall, dam characteristics were more important in affecting fish species richness but less important in determining fish species composition than local habitat （i.e., substrate heterogeneity） and tributary position. Our results suggest that low-head dam may affect fish species richness in impoundments by modifying local habitat and constraining fish movement, and the relative abundances of those fish species may depend more on species habitat presences and stream size than on impoundment size and number.

Optimal incision sites to reduce corneal aberration variations after small incision phacoemulsification cataract surgery

AIM： To analyze the effect of steep meridian small incision phacoemulsification cataract surgery on anterior,posterior and total corneal wavefront aberration.· METHODS： Steep meridian small incision phacoemulsification cataract surgery was performed in age-related cataract patients which were divided into three groups according to the incision site： 12 o＇clock, 9o＇clock and between 9 and 12 o＇clock（BENT） incision groups. The preoperative and 3-month postoperative root mean square（RMS） values of anterior, posterior and total corneal wavefront aberration including coma,spherical aberration, and total higher-order aberrations（HOAs）, were measured by Pentacam scheimpflug imaging. The mean preoperative and postoperative corneal wavefront aberrations were documented.·RESULTS： Total corneal aberration and total lower-order aberrations decreased significantly in three groups after operation. RMS value of total HOAs decreased significantly postoperatively in the 12 o＇clock incision group（P 〈0.001）. Corneal spherical aberration was statistically significantly lower after steep meridian small incision phacoemulsification cataract surgery in BENT incision group（P 〈0.05） and Pearson correlation analysisindicated that spherical aberration changes had no significant relationship with total astigmatism changes in all three corneal incision location.·CONCLUSION： Corneal incision of phacoemulsification cataract surgery can affect corneal wavefront aberration.The 12 o＇clock corneal incision eliminated more HOAs and the spherical aberrations decreased in BENT incision group obviously when we selected steep meridian small incision. Cataract lens replacement using wavefront-corrected intraocular lens combined with optimized corneal incision site would improve ocular aberration results.

Age,growth and reproduction of Sarcocheilichthys nigripinnis from the Qingyi Stream in the Huangshan Mountains

Identifying the life-history strategies of fish and their associations with the surrounding environment is the basic foundation in the conservation and sustainable utilization of fish species.We examined the age,growth,and reproduction of Sarcocheilichthys nigripinnis using 352 specimens collected monthly from May 2009 to April 2010 in the Qingyi Stream.We found the sex ratio of this study population was 0.58:1(female:male),significantly different from expected 1:1.Females and males both comprised four age groups.The annuli on the scales were formed during February and March.No obvious between-sex difference was observed in length-weight and length-scale-radius relationships.The total length in back-calculation significantly increased with age for both sexes,but did not differ significantly at each age between the two sexes.An inflection point was observed in the growth curves given by the von Bertalanffy growth function for total weight.At this inflection point,fish were 3.95 years.Both sexes reach their 50%sex maturity at age 2,when females and males were 94.7 mm and 103.0 mm total length.The temporal pattern of the gonado-somatic index corresponded to a spawning period that occurred from April through July.The non-synchronicity of egg diameter in each mature ovary during the breeding period suggested these fish may be batch spawners.The absolute fecundity increased significantly with total length and weight,whereas no significant correlation was observed between the relative fecundity and body size.

人为干扰对溪流鱼类功能多样性及其纵向梯度格局的影响

溪流鱼类多样性沿着河流纵向梯度的空间分布规律已得到大量报道,但这些研究大多聚焦基于物种组成的分类α多样性,而有关分类β多样性和功能多样性的纵向梯度分布规律及其对人类干扰的响应研究较少。本文以青弋江上游3条人为干扰程度不同的河源溪流为研究区域,比较研究了人为干扰对溪流鱼类功能α和β多样性及其纵向梯度分布格局的影响。结果显示,人类干扰改变了河源溪流鱼类功能多样性的纵向梯度格局——由线性变化变为二项式分布。此外,我们发现,人为干扰导致土著种被本地入侵种取代,且较强的土地利用和水污染排放可能增大环境的不连续性,而群落周转和嵌套变化往往取决于环境的变化。尽管功能β多样性由嵌套成分主导,但周转成分占比相对于人为干扰较小的溪流而言明显增加。人为干扰显著改变了受干扰溪流鱼类的物种组成和功能多样性,且功能多样性的纵向梯度格局在不同的多样性指标上存在差异。本研究强调,在评估人为干扰下多样性的变化时,需要从多方面考虑,包括空间尺度和多样性指标等。