摘要:

Eleotrid fish (gudgeons) commonly dominate the small-fish fauna throughout much of the Indo-Pacific region. Eleotrids frequently occupy habitats comprised of dense emergent macrophytes, making estimation of fish abundance difficult. In this study, the suitability of unbaited fish traps to measure carp gudgeon (Hypseleotrisspp.) abundance in giant rush habitats was studied in a River Murray floodplain billabong using depletion trapping. Traps were repeatedly set at ten locations within giant rush beds over a two-day period. There was no significant variation in carp gudgeon catch rate over time within locations, but variation between locations was significant. It was not possible to deplete fish from any location over two days of trapping, suggesting rapid replacement of trapped fish in sampled locations. Patch specific variation in the gudgeon catch rate among different traps in macrophyte beds may reflect small-scale variation in habitat quality.

ISSN:0270-5060    

DOI:10.1080/02705060.2000.9663757

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The distribution and abundance of soft bottom chironomids in an organically polluted lowland river of Central Italy were investigated relative to correlations with physicochemical parameters of the water and sediments. Chironomus were the dominant tribe in the river with the highest density at the most polluted stations.Chironomus ripariusshowed the highest annual mean densities at the very highly polluted station, where it was the dominant species in late spring and summer. At the same station,Micropsectrasp.,Polypedilum breviantennatum, Cryptochironomussp.,Harnischiasp. andCricotopus bicinctusreplacedC. ripariusin winter, when the environmental conditions improved slightly. Densities of all the above mentioned taxa generally showed a positive correlation with the orthophosphate and BOD5contents and a negative correlation with the oxygen content.C. riparius, Micropsectrasp. andHarnischiasp. preferred fine sediments (silt/clay and very fine sand) with high organic matter content, whereasP. breviantennatumwas mostly confined to sandy stations.Robackia demejerei, Acalcarellasp.,Rheosmittia spinicornisandParacladopelma clorisgroup were present and/or abundant exclusively at unstable sandy stations with summer regulation of the water. Principal Component Analyses based on chironomid densities seems to provide an integrated response to the effects of both physical (hydraulic stress and granulometric composition of the sediment) and chemical characteristics (organic pollution) of the river.

ISSN:0270-5060    

DOI:10.1080/02705060.2000.9663758

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Smallmouth bass (Micropterus dolomieu) introduced nearly 50 years ago have established a permanent population in Little Moose Lake, NY. Over 500 smallmouth bass were collected by angling in the littoral zone from June to August. Gut contents were compared for differences based on length of bass, date of capture, and substrate type where each fish was caught. Crayfish were the most frequent diet item and made up the largest percent composition by number. The average number of crayfish per stomach increased with bass length as did the number of fish per stomach. Crayfish, Ephemeroptera, Odonata, and fish made up 77% of the total number of diet items, excluding zooplankton. A noticeable diet shift from smaller diet items (Ephemeroptera) to larger ones (crayfish and fish) occurred when smallmouth bass approached 150 mm. A high amount of diet overlap occurred between bass caught over different substrate types and among most size classes. Smallmouth bass in Little Moose Lake were opportunistic feeders, using benthic, terrestrial, and pelagic littoral zone food resources. The most likely processes by which smallmouth bass affect salmonid and native fishes in Little Moose Lake are competition for food resources and predation.

ISSN:0270-5060    

DOI:10.1080/02705060.2000.9663759

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Horsehair wormsParagordius varius, Chordodes morganiandGordius robustusare reported for the first time from Indiana. These observations increase the known distribution of these species.

ISSN:0270-5060    

DOI:10.1080/02705060.2000.9663760

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The early life history of blue sucker (Cycleptus elongatus) is relatively unknown across its range; however, we collected seven age-0 specimens in an upper Missouri River backwater in North Dakota during the flood pulses of 1997 and 1999. Specifically, the specimens were captured in the upper 0.4 m of the water column (1.O to 2.5 m total depth) in close proximity to the backwater-channel connection points and in the margins of marsh smartweed (Polygonum coccineum) beds.

ISSN:0270-5060    

DOI:10.1080/02705060.2000.9663761

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

ISSN:0270-5060    

DOI:10.1080/02705060.2000.9663762

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

ISSN:0270-5060    

DOI:10.1080/02705060.2000.9663746

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor