22 research outputs found
Effect of waterfalls and the flood pulse on the structure of fish assemblages of the middle Xingu River in the eastern Amazon basin
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Brown bullhead as an indicator species: Seasonal movement patterns and home ranges within the Anacostia River, Washington, D.C.
Elevated liver and skin tumor prevalence has been reported in brown bullhead(Ameiurus nebulosus) from the tidal Anacostia River, Washington, D.C. Movement data areneeded to effectively use tumor prevalence as an indicator of habitat quality. We used ultrasonictelemetry to verify the residency of 40 adult brown bullheads (250–310 mm total length) in theAnacostia River during summer 2000, spring 2001, and fall–winter 2001–2002. During summer(10 fish tagged), fish remained within 500 m of their capture–release location, and their mean95% minimum area polygon (MAP) and linear home ranges were 4.5 ha and 0.50 km. Duringspring (12 fish tagged), most fish traveled upstream of the capture–release location as watertemperatures increased; they were approximately 1 km upriver by the end of the season. Mean95% MAP and linear home ranges in spring were 19.7 ha and 2.1 km. During fall–winter (18 fishtagged), fish released in the river remained within 4.2 km upstream and 3.1 km downstream oftheir capture– release location, and their mean 95% MAP and linear home ranges were 15.9 haand 2.1 km. In comparison, the 95% MAP and linear home ranges of fish released in LakeKingman (a tidal freshwater impoundment of the Anacostia) were 5.8 ha and 0.58 km. No fishwere located outside of the Anacostia River. We conclude that adult brown bullheads wereresident in the system throughout the year
Hot deformation, dynamic recovery, and recrystallisation behaviour of aluminium 6061–SiC p
Sibship Analysis to Characterize Alligator Gar Reproductive Contributions in Two Texas Systems
© 2019 American Fisheries Society We used sibship analysis to further our understanding of Alligator Gar Atractosteus spatula reproductive biology. Quantifying the relative contributions of spawners and spatial patterns of reproduction is important in making management decisions, especially with regard to long-lived, large-bodied fish like Alligator Gar, for which exploitation of large females may negatively impact recruitment. Using genetic data from age-0 fish, we estimated the effective number of breeders (Nb) and the number of spawning adults (NS) at multiple spatial and temporal scales in two Texas systems over a 2-year period. Analysis of 265 fish collected in 2015 from six sites within an approximately 3,000-ha floodplain wetland system on the Trinity River identified no full siblings or half siblings with a probability greater than 0.90. Estimates of Nb (24–30) and NS (21–33) were comparable among sites, with low levels of relatedness among individuals within sites. Analysis of an additional 136 age-0 Alligator Gar collected during 2015 from six other sites distributed over 275 river kilometers downstream of the wetland system revealed similar patterns. Age-0 fish collected in Choke Canyon Reservoir (N = 131) in 2015 also demonstrated close correspondence between estimates of Nb and NS (54 and 56, respectively). Age-0 Alligator Gar (N = 88) were again collected at three sites in the Trinity River system during 2016; results were comparable to those of the previous year, with no evidence of repeat spawning at each site. The similarities we observed between the estimated Nb and NS indicated little variance in the number of offspring produced among individual spawners. Because individual spawners appear to contribute somewhat equally to the year-classes and spawning appears to occur over a broad geographic extent, there is likely little risk of year-class failure from harvesting a sustainable number of spawning adults