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 2008 across 11 study sites in a subtropical small stream, the Puxi Stream, of the Huangshan Mountain. Along the longitudinal gradient from headwater to downstream, fish species richness and abundance increased gradually, but then decreased significantly at the lower reaches. The highest species richness and abundance were observed in August and the lowest in February. Based on analysis of similarities （ANOSIM）, fish assemblages were significantly different in spatial variation but not in temporal variation. Although differences were observed both among sites and among stream orders, the lower R value in order-variation suggested stream order was not the optimal factor explaining the spatial variation of fish assemblages. In addition, dam construction did not significantly alter fish assemblages in the sites adjacent to and immediately downstream to dams. Using cluster analysis and non-metric Multi Dimensional Scaling analysis （NMS）, assemblages were separated into three groups at a Bray-Curtis similarity value of 42%： the upper, middle and lower groups. Following analysis of similarity percentages of species contributions （SIM- PER）, shifts in occurrence or abundance of S. curriculus, Z. platypus, R. bitterling and A. fasciatus contributed most to the differences amongst 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 pattem 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 perhaps induced the decrease in species diversity in the lower reaches. However, no significant change was observed for fish assemblages in sites far from and immediately downstream from low-head dams [Current Zoology 56 （6）： 670-677, 2010].

Fish and fish side streams are valuable sources of high-value components

The current practice of fish processing generates increasing quantities of side streams and waste,such as skin,heads,frames,viscera,and fillet cut offs.These may account for up to 70%of the fish used in industrial processing.Low-value fish catches,and under-utilized fish species comprise another source of side streams.These side streams have been discarded in the environment leading to environmental problems or they have ended up as low commercial value products,such as feed for fur animals and aquaculture.However,several studies have shown that fish side streams contain valuable bioactive ingredients and fractions,such as fish oils,proteins and peptides,collagen,gelatin,enzymes,chitin,and minerals.These compounds and fractions may provide the opportunity to develop novel applications in health promoting foods,special feeds,nutraceuticals,pharmaceuticals,and cosmetic products.Better utilization of side streams and low-value fish would simultaneously improve both the environmental and ecological sustainability of production.This review summarizes the current knowledge on fish and fish side streams as sources of high-value components such as peptides with antimicrobial,antioxidative,antihypertensive,and antihyperglycemic properties,proteins such as fish collagen and gelatin,fish enzymes,fish oils and fatty acids,polysaccharides like glucosaminoglycans,chitin and chitosan,vitamin D,and minerals.Production technologies for recovering the high-value fractions and potential product applications are discussed.Furthermore,safety aspects related to the raw material,technologies,and fractions are considered.

Conversion of fish processing wastewater into fish feed ingredients through submerged cultivation of Aspergillus oryzae

Fish processing towards production of fillet gives rise to wastewater streams that are ultimately directed to biogas production and/or wastewater treatment.However,these wastewater streams are rich in minerals,fat,and proteins that can be converted to protein-rich feed ingredients through submerged cultivation of edible filamentous fungi.In this study,the origin of wastewater stream,initial pH,cultivation time,and extent of washing during sieving,were found to influence the amount of recovered material from the wastewater streams and its protein content,following cultivation with Aspergillus oryzae.Through culti-vation of the filamentous fungus in sludge,330 kg of material per ton of COD were recovered by sieving,corresponding to 121 kg protein per ton of COD,while through its cultivation in salt brine,210 kg of material were recovered per ton of COD,corresponding to 128 kg protein per ton of COD.Removal ranges of 12-43%,39-92%,and 32-66%for COD,total solids,and nitrogen,respectively,were obtained after A.oryzae growth and harvesting in the wastewater streams.Therefore,the present study shows the versatility that the integration of fungal cultivation provides to fish processing industries,and should be complemented by economic,environmental,and feeding studies,in order to reveal the most promising valorization strategy.