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

Breeding strategy of Acrossocheilus fasciatus in the Puxi Stream of the Huangshan Mountain

Breeding strategies of Acrossocheilus fasciatus were studied from 592 specimens collected monthly during May 2007 and April 2008 in the Puxi Stream of the Huangshan Mountain.Sex ratio of the studied population was 0.90∶1(♀∶♂),not significantly different from 1∶1.Both sexes reached their first sexual maturity at age 2(the second calendar year of their birth).Fifty percent of females and males reached maturity at a total length of 69.75 mm and 69.36 mm respectively,and the minimum total length was 61.54 mm and 58.96 mm,respectively.Based on the monthly changes in gonado-somatic index and egg-development process,the breeding season of the population was from May to August,with one obvious interval(in June)occurring in the breeding activity for the females.The nonsynchronous development of oocytes observed in mature ovaries indicated that A.fasciatus is a batch spawner.Absolute fecundity of A.fasciatus ranged from 308 to 2002 eggs with a mean of 857 eggs,increased significantly with total length,and was significantly different among three age groups.Relative fecundity ranged from 38.63 to 71.70 egg/g with a mean of 53.29 egg/g,and was not significantly different among the three age groups.It was suggested that these reproductive characteristics were adaptive strategies for A.fasciatus to acclimatize to lotic water where environmental factors were unstable but predictable.

Variations in reproductive strategies between one invasive population and two native populations of Pseudorasbora parva

Reproductive traits of one invasive population in Lake Fuxian and two native populations in Lakes Chao and Dongting for Pseudorasbora parva were investigated to determine the variations in their reproductive strategies associated with the change of environmental conditions. Compared with the two native populations,P.parva markedly experienced the protraction in their spawning time and the decrease in mortality for adult individuals in Lake Fuxian. The three populations all got their first sexual maturity at the same age,but their total lengths at maturity were quite different for those in Lake Chao were significantly lower than in Lakes Fuxian and Dongting. Additionally,in spite that no significant difference occurred in their relative fecundities for P. parva in Lakes Fuxian and Dongting,the population in Lake Chao showed the markedly higher relative fecundity than the other two populations. These results were analyzed with the variations in water temperature,nutrient status,fishing stress among the three lakes. The relative decline in fecundity for the invasive population,which conflicted with the enemy release hypothesis,was disscussed with the context of the preponderance of another invasive fish,Neosalanx taihuensis,in Lake

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.

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.