摘要:

AbstractThe behavior of black mudfish (Neochanna diversusStokell, 1949: Galaxiidae) and mosquitofish (Gambusia affinisBaird&Girard, 1854: Poeciliidae) was investigated in laboratory tanks. Black mudfish are indigenous to northern New Zealand, and mosquitofish are introduced; both species are sympatric in wetlands in the Waikato region. By comparing position, feeding rates and aggressive behavior of both species, we found that black mudfish were increasingly able to compete with mosquitofish as they grew from fry to adults. Mosquitofish were more aggressive towards mudfish fry and juveniles than were these two life stages towards mosquitofish, but adult mudfish were aggressive towards mosquitofish. Both small (18–24 mm total length (TL)) and large mosquitofish (25–36 mm TL) showed high aggression towards mudfish fry (13–18 mm TL), and fry were eaten by large mosquitofish. However, 3 interspecific differences appear to allow coexistence of these two species. Firstly, mudfish reproduce in winter, whereas mosquitofish reproduce in summer, resulting in mudfish fry being present when mosquitofish are at their lowest abundance. Secondly, mudfish can survive in seasonally dry habitats by aestivation, while mosquitofish cannot. Thirdly, adult black mudfish are nocturnal, whereas mosquitofish are primarily di

ISSN:0906-6691    

DOI:10.1111/j.1600-0633.1994.tb00110.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractStellifer rastrifer(Sciaenidae) from the Sergipe River (Brazil) sagittal otoliths show a microstructure that is common to many fish, with microincrements of growth made up of continuous and discontinuous units. The microincrements show thickness and structure variations, which apparently correspond with the rings seen at the macrostructural level.

ISSN:0906-6691    

DOI:10.1111/j.1600-0633.1994.tb00111.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractWe monitored water chemistry and populations of brook trout (Salvelinus fontinalis) and mottled sculpins (Cottus bairdi) in 5 streams and some tributaries to determine how the severity of acidic episodes (low pH and high Al) influenced density and distribution of these species. Among streams, Linn Run had the lowest pH (4.8) and highest concentrations of total dissolved Al (>400 μg‐l−1) during periods of high discharge. Densities of brook trout and mottled sculpins were low in Linn Run, but high in tributaries, where pH (6.5) and Al (30 μg‐l−1) remained well below lethal levels. Among the other streams, brook trout density was highest where the acidic episodes were least severe and the density of age‐0 brook trout was lowest when precipitation during the early months of the year was above normal. Immigration of brook trout from downstream areas maintained populations in the stream segments subjected to severe episodes. Mottled sculpins were not found in streams with seve

ISSN:0906-6691    

DOI:10.1111/j.1600-0633.1994.tb00112.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe effect of natural lakes on the fish species distribution in surrounding streams was studied using electrofishing survey data from 3281 localities in streams throughout Sweden. The occurrence of lake fish (northern pike, European perch, roach and burbot) was significantly higher close to lakes, both up‐ and downstream, as compared to localities further up‐ or downstream of lakes. Correspondingly, the occurrences of stream fish (brown trout, grayling, European minnow and bullheads) were lower close to lakes. It is suggested that the lower occurrences of the latter close to lakes be due to biotic interaction with lake fish, especially predation from pike and burbot. The results strongly indicate that the effect of lakes on water temperature, drift of plankton and invertebrates or the moderating effect on water fluctuations and quality did not influence the stream fish fauna to the same extent as the presence of lake fish in a zone up‐ as downstream of the lakes. Lakes function as a reservoir of strong predators and compet

ISSN:0906-6691    

DOI:10.1111/j.1600-0633.1994.tb00113.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractWe quantified microhabitat use inBarbus graellsii, Cyprinus carpio, Chrondostoma toxostoma, Esox lucius, Gobio gobioandLeuciscus cephalusduring 1984–1987 in the lower Rio Matarraña, Spain. Fluctuations in numerical abundances of assemblage members increased during 1986–1987. These increased fluctuations were due to decreases in the abundances ofCh. toxostoma, E. luciusandG. gobioduring the latter 2 years of our study. OnlyC. carpioincreased slightly in abundance during this period. An analysis of microhabitat availability data indicated that 16 seasonal samples could be assigned to 1 of 6 groups ranging from: seasons with zero velocities, shallower depths and an algal/debris substratum to those with high velocities and depths and a substratum composed of algae/debris, rubble and gravel. Most seasonal changes in the substratum were attributable to conditions inhospitable to the growth of benthic algae (i. e., high velocities or low oxygen levels) rather than to actual changes in the underlying lithospheric substratum. Principle component analyses indicated that most species were overrepresented in deeper microhabitats with depositional substrata.Ch. toxostoma, however, tended to occur over rubble substrata in both shallow and deep microhabitats. Most seasonal changes in microhabitat use were produced by seasonal variations in microhabitat availability. However, all species exceptE. luciusexhibited seasonal variations in microhabitat use that typically involved velocity, depth and substratum composition. Although smaller specimens of most species were found closer to the substratum in 1984–1985, they tended to occupy shallow areas in 1986–1987. Canonical analyses of discriminants and univariate data demonstrated that the distance from the substratum was the best predictor of interspecific differences in microhabitat use. Species could be arrayed along a vertical gradient withL. cephalusandCh. toxostomaoccupying mid‐water column positions,B. graellsiiandC. carpiooccurring in lower‐water column microhabitats andE. luciusandG. gobiostrongly associated with the substratum. Changes in interspecific microhabitat use were not correlated with changes in species abundances, and hence, interspecific competition did not appear to strongly influence microhabitat use duri

ISSN:0906-6691    

DOI:10.1111/j.1600-0633.1994.tb00114.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractOn 3 occasions during summer 1977, small groups of a typically run‐ and pool‐dwelling minnow (blacktail shiner,Cyprinella venusta) were observed feeding in a shallow riffle on items dislodged by foraging northern hog suckers (Hypentelium nigricans). Although such nuclear‐attendant following behavior has been documented in marine systems and has been reported from some African freshwater lakes, descriptions from freshwater streams are rare. We describe the interaction and consider the probable development of the search behaviour of the blacktail shiners. We also explore the possible benefits of searching for hog suckers in small groups, as observed, rather than as individuals or in large groups. This feeding strategy may be an important mechanism of food acquisition for some individuals when usual resources are s

ISSN:0906-6691    

DOI:10.1111/j.1600-0633.1994.tb00115.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY