Background Agriculture has greatly influenced water quality,habitats,and fish assemblages in streams of the Mississippi Alluvial Plain(MAP)ecoregion.However,MAP streams have historically been understudied compared to ...Background Agriculture has greatly influenced water quality,habitats,and fish assemblages in streams of the Mississippi Alluvial Plain(MAP)ecoregion.However,MAP streams have historically been understudied compared to streams in other agricultural regions of the USA.In this study,water quality,habitat,and fish assemblage composition were assessed seasonally(spring,summer,and fall)in eight representative MAP streams located across three U.S.states.The study design included four streams containing highly agricultural watersheds(herein termed“agriculture”streams)and four streams containing mostly forested watersheds(herein termed“forest”streams),which were intended to represent reference conditions for MAP streams.Results In general,forest streams contained significantly better instream and riparian habitats than agriculture streams(P=0.010–0.040)whereas agriculture streams contained significantly greater levels of primary nutrients(P<0.001–0.010).Differences between agriculture and forest streams with respect to other physical and chemical variables were intermittent and season dependent.Fish assemblages in agriculture and forest streams were structured primarily along an environmental gradient reflecting instream habitat conditions,water nutrient concentrations,and benthic chlorophyll-a production.Structurally,fish assemblages in both stream types contained many regionally common species,though some species appeared to exhibit affinities for a particular stream type.Functionally,fish assemblages in agriculture streams contained more tolerant species,more omnivores,and fewer insectivores compared to forest stream assemblages,which were nearly all insectivores.Overall,one-third of the fish specimens collected in forest streams classified as intolerant species.Conclusions Our results suggested that stream water quality,habitat,and fish assemblages differed between agriculture and forest streams in the MAP,with fish assemblages exhibiting both structural and functional differences.Results were consistent with a larger body of literature from smaller,headwater streams whereby land-use changes(e.g.,row-crop agriculture)impacted the physical,chemical,and biological characteristics of stream ecosystems.Results further highlight the importance of land use management and its effects on habitat diversity in stream ecosystems,and that protecting the few remaining undisturbed or less-disturbed streams should be a priority.展开更多
Background Since the late 1990s,bigheaded carps(largely silver carp[Hypophthalmichthys molitrix]but also bighead carp[H.nobilis])have established throughout the lower Mississippi River basin.Using previously studied o...Background Since the late 1990s,bigheaded carps(largely silver carp[Hypophthalmichthys molitrix]but also bighead carp[H.nobilis])have established throughout the lower Mississippi River basin.Using previously studied oxbow lakes in the lower White River basin,Arkansas,we compared current(2017,“post-carp”establishment)fish assemblages to historical(2002,“pre-carp”establishment)fish assemblages.Fish assemblages were comprehensively assessed using multiple gears,including boat electrofishing,mini-fyke nets,and experimental small-mesh gill nets.Results T-tests suggested that fish assemblage indices of richness,diversity,evenness,and dominance were often greater(P<0.05)during the post-carp period as reflected by boat electrofishing and experimental gill nets.However,all indices were generally similar(P>0.05)between the pre-carp and post-carp period with fish assemblages depicted using mini-fyke nets.Nonmetric multidimensional scaling analyses indicated that fish assemblages differed structurally between pre-carp and post-carp periods.Assemblage differences were linked to both small and large abundance changes for more than 20 species.Abundances of gizzard shad(Dorosoma cepedianum),emerald shiner(Notropis atherinoides),pugnose minnow(Opsopoeodus emiliae),crappies(Pomoxis spp.),bluegill(Lepomis macrochirus),orangespotted sunfish(L.humilis),and yellow bass(Morone mississippiensis)declined between the pre-carp and postcarp periods.Conversely,abundances of weed shiner(N.texanus),pallid shiner(Hybopsis amnis),longear sunfish(L.megalotis),buffalofishes(Ictiobus spp.),and gars(Lepisosteus spp.)generally increased during the same period.Conclusions Although not possible to conclude assemblage shifts were entirely related to bigheaded carps due to the absence of an appropriate reference system where carps did not establish,the wide establishment of these carps is one of the most pervasive changes to have occurred in the lower White River ecosystem during the past two decades.Thus,it is probable to conclude that post-carp establishment observations from this study were at least,in part,attributable to bigheaded carp establishment.Impacts of further range expansions by bigheaded carps in the White River and other lower Mississippi River sub-basins are unclear,though this study suggests probable effects on native fish assemblages,underscoring the need for further research and monitoring.展开更多
The aquatic fauna of large river systems have been the cornerstones of multiple civilizations throughout human history.Today,they remain critically important as primary resources for humans as well as indicators of ge...The aquatic fauna of large river systems have been the cornerstones of multiple civilizations throughout human history.Today,they remain critically important as primary resources for humans as well as indicators of general ecosystem structure and function.Unfortunately,nearly all large-river systems globally are at risk from over-exploitation,pollution,large-scale development,navigation,dredging,climate change,and other threats.For instance,human stressors(such as dams,navigation,agriculture,fshing)and fooding and droughts have afected aquatic biological resources in both the Mississippi and Yangzte River basins(Chen et al.2016).展开更多
基金partially funded by an USDA Natural Resources Conservation Service(NRCS)Conservation Innovation Grant(CIG)the NRCS Mississippi River Basin Healthy Watersheds Initiative(MRBI)+2 种基金National Water Quality Initiative(NWQI)programspartially supported by National Key R&D Program of China(2019YFD0901201,2019YFD0901203)Chinese Academy of Sciences(ZDRW-ZS-2017-3-2)
文摘Background Agriculture has greatly influenced water quality,habitats,and fish assemblages in streams of the Mississippi Alluvial Plain(MAP)ecoregion.However,MAP streams have historically been understudied compared to streams in other agricultural regions of the USA.In this study,water quality,habitat,and fish assemblage composition were assessed seasonally(spring,summer,and fall)in eight representative MAP streams located across three U.S.states.The study design included four streams containing highly agricultural watersheds(herein termed“agriculture”streams)and four streams containing mostly forested watersheds(herein termed“forest”streams),which were intended to represent reference conditions for MAP streams.Results In general,forest streams contained significantly better instream and riparian habitats than agriculture streams(P=0.010–0.040)whereas agriculture streams contained significantly greater levels of primary nutrients(P<0.001–0.010).Differences between agriculture and forest streams with respect to other physical and chemical variables were intermittent and season dependent.Fish assemblages in agriculture and forest streams were structured primarily along an environmental gradient reflecting instream habitat conditions,water nutrient concentrations,and benthic chlorophyll-a production.Structurally,fish assemblages in both stream types contained many regionally common species,though some species appeared to exhibit affinities for a particular stream type.Functionally,fish assemblages in agriculture streams contained more tolerant species,more omnivores,and fewer insectivores compared to forest stream assemblages,which were nearly all insectivores.Overall,one-third of the fish specimens collected in forest streams classified as intolerant species.Conclusions Our results suggested that stream water quality,habitat,and fish assemblages differed between agriculture and forest streams in the MAP,with fish assemblages exhibiting both structural and functional differences.Results were consistent with a larger body of literature from smaller,headwater streams whereby land-use changes(e.g.,row-crop agriculture)impacted the physical,chemical,and biological characteristics of stream ecosystems.Results further highlight the importance of land use management and its effects on habitat diversity in stream ecosystems,and that protecting the few remaining undisturbed or less-disturbed streams should be a priority.
基金U.S.Fish and Wildlife Service—Gulf States Marine Fisheries Commission through the Gulf&Atlantic Regional Panel on Aquatic Invasive Speciesthe U.S.Fish and Wildlife Service—Lower Mississippi River Conservation CommitteeAdditional financial support and facilities were provided by the Aquaculture/Fisheries Center at the University of Arkansas at Pine Bluff(UAPB)
文摘Background Since the late 1990s,bigheaded carps(largely silver carp[Hypophthalmichthys molitrix]but also bighead carp[H.nobilis])have established throughout the lower Mississippi River basin.Using previously studied oxbow lakes in the lower White River basin,Arkansas,we compared current(2017,“post-carp”establishment)fish assemblages to historical(2002,“pre-carp”establishment)fish assemblages.Fish assemblages were comprehensively assessed using multiple gears,including boat electrofishing,mini-fyke nets,and experimental small-mesh gill nets.Results T-tests suggested that fish assemblage indices of richness,diversity,evenness,and dominance were often greater(P<0.05)during the post-carp period as reflected by boat electrofishing and experimental gill nets.However,all indices were generally similar(P>0.05)between the pre-carp and post-carp period with fish assemblages depicted using mini-fyke nets.Nonmetric multidimensional scaling analyses indicated that fish assemblages differed structurally between pre-carp and post-carp periods.Assemblage differences were linked to both small and large abundance changes for more than 20 species.Abundances of gizzard shad(Dorosoma cepedianum),emerald shiner(Notropis atherinoides),pugnose minnow(Opsopoeodus emiliae),crappies(Pomoxis spp.),bluegill(Lepomis macrochirus),orangespotted sunfish(L.humilis),and yellow bass(Morone mississippiensis)declined between the pre-carp and postcarp periods.Conversely,abundances of weed shiner(N.texanus),pallid shiner(Hybopsis amnis),longear sunfish(L.megalotis),buffalofishes(Ictiobus spp.),and gars(Lepisosteus spp.)generally increased during the same period.Conclusions Although not possible to conclude assemblage shifts were entirely related to bigheaded carps due to the absence of an appropriate reference system where carps did not establish,the wide establishment of these carps is one of the most pervasive changes to have occurred in the lower White River ecosystem during the past two decades.Thus,it is probable to conclude that post-carp establishment observations from this study were at least,in part,attributable to bigheaded carp establishment.Impacts of further range expansions by bigheaded carps in the White River and other lower Mississippi River sub-basins are unclear,though this study suggests probable effects on native fish assemblages,underscoring the need for further research and monitoring.
基金supported by National Key Research and Development Program of China(2023YFC3209002,2019YFD0901203)Chinese Academy of Sciences(QYZDB-SSW-SMC041,ZDRW-ZS-2017-3-2)
文摘The aquatic fauna of large river systems have been the cornerstones of multiple civilizations throughout human history.Today,they remain critically important as primary resources for humans as well as indicators of general ecosystem structure and function.Unfortunately,nearly all large-river systems globally are at risk from over-exploitation,pollution,large-scale development,navigation,dredging,climate change,and other threats.For instance,human stressors(such as dams,navigation,agriculture,fshing)and fooding and droughts have afected aquatic biological resources in both the Mississippi and Yangzte River basins(Chen et al.2016).
