摘要:

We examined associations between habitat variables and occurrence and density of alewife (Alosa pseudohareneus) and blueback herring (Alosa aestivalis) early egg stages (unfertilized and newly fertilized) in a tributary of the Rappahannock River, Virginia from February to May 1992. We looked for temporal associations between tidal condition, time of day, light intensity, and temperature and peaks in egg densities. Occurrences of alewife early egg stages were positively related to dissolved oxygen (7–12 mg/l) and velocity (3–20 cm/s), and peak densities were positively associated with peaks in water temperature (within the range of 4–19°C). Occurrences of blueback herring early egg stages were positively related to water temperature (14–22°C). There was no correlation between occurrences of early eggs of either species and tidal condition.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663691

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

We documented potential spatial differences within the aquatic bacterial community in a newly rehabilitated wetland. Replicate 10 meter transects were partitioned into four sites of various depths representing open water (>35 cm), water/macrophyte interface (20–30 cm), a submersed macrophyte bed (10–25 cm), and a nearly dry (<5 cm) macrophyte stand. We isolated 30 bacterial strains from the senescing plant/water interface from each site, and characterized the Gram stain and morphology across each transect. The majority of isolates (66.6%) were Gram negative, bacillus forms. Also, senescing matter from each site was collected and the ability of each set of isolates to utilize each leachate was tested. The isolated bacteria exhibited a significantly greater ability (p< 0.05) to utilize its co-occurring leachate than did bacteria from other sites within a transect.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663692

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

We introduced a new four-parameter growth equation and tested it with observed growth data sets for a variety of aquatic species. The equation is:

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663693

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

We conducted a biotelemetry study to assess spring movements and locate spawning areas of sauger (Stizostedion canadense) in a small (2800 ha.) Kansas reservoir lacking large river inflow. Twenty adult sauger were implanted with ultrasonic tags and tracked in Melvern Lake from February to June 1993. Movements, calculated as minimum displacement from 254 fish fixes, were greatest in March (P<0.003) prior to the spawn, ranging to 2.8 km/d. Male sauger inhabited deeper water than females (P=0.04). Multiple regression analysis revealed that water column depth utilized by sauger was a function of barometric pressure and reservoir inflow/discharge. Tagged sauger inhabited different lake regions throughout the study period (P<0.001), moving from mid-lower lake in February to down-lake north shores for the April spawn and dispersing thereafter. In April, at water temperatures of approximately 8 C, sauger congregated in mainstem shoals, where they apparently spawned in shallow (1–2 m) water over cobble, pebble, and clay-silt substrates.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663694

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

We explored whether certain behaviors by prey fish species contributed to selective predation by lake trout (Salvelinus namaycush). Schooling behavior, reactive distance, and predator attack and prey escape swimming speeds were examined for alewife (Alosa pseudoharengus), bloater (Coregonus hoyi), rainbow smelt (Osmerus mordax), and yellow perch (Perca flavescens). In addition, two- and three-prey species combinations were presented to lake trout to determine if a particular prey species was utilized to a greater extent than others and to observe which specific behaviors or other prey characteristics could account for their greater utilization. There was little difference in percent capture of various prey species and no significant difference (p > 0.05) in escape swimming speeds or attack swimming speeds. However, maximum attack swimming speeds by the lake trout exceeded the maximum escape swimming speeds of prey. Average escape swimming speeds ranged from 2.5 to 2.9 m/sec, and average attack swimming speeds ranged from 2.8 to 3.1 m/sec. Reactive distances were not important since more than 90% of the prey were captured before they had time to react. Prey reactive distances ranged from 0.0 to 1.0 m. Even a small reactive distance and an average escape swimming speed allowed the prey to get close to the aquarium wall where lake trout would not attack. In two-species trials, bloater was preferred over yellow perch (p < 0.025) in one trial. In three-species trials, lake trout foraged preferentially (p < 0.05) on alewife when compared to bloater and yellow perch in four of five trials. The bloater appeared as the second most utilized species although there was no significant difference (p > 0.05) in utilization between bloater and yellow perch. Lake trout were probably reacting to the continuous movement and tight schooling of alewives in the water column.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663695

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663696

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663680

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor