摘要:

Because organisms living in Florida's fully-flooded caves depend upon allochthonous input for food, abundances of cave fauna may be related to distance from cave openings. Distributions of cave crayfish and catfish were investigated within 16 fully-flooded cave systems. In each cave, a transect was established beginning at the edge of the aphotic zone and continuing into the cave for 244 m. Transects were divided at their mid-points, and abundances from the outer half-transects were compared to abundances from the inner half-transects. Crayfish abundances were not significantly different between half-transect pairs, but catfish abundances were significantly greater along outer half-transects (p<0.05, Wilcoxon matched-pairs signed ranks test). During this investigation, three species of catfish were observed along transects—the yellow bullhead,Ameiurus natalis, the brown bullhead,Ameiurus nebulosus, and the channel catfish,Ictalurus punctatus.

ISSN:0270-5060    

DOI:10.1080/02705060.1994.9664883

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Fish were collected at 18 sites in the Arkansas (N=6) and Eagle (N=12) rivers. Richness at all sites was low (1–3 species). Analyses of fish assemblage data from the Arkansas and Eagle rivers and their tributaries suggested significant differences among sites subject to mine impacts and control or recovering sites. Native taxa were collected at only one site in the Arkansas River drainage (Oncorhynchus clarki clarki) and only at the Eagle River control sites (Paiute sculpins,Cottus beldingi).

ISSN:0270-5060    

DOI:10.1080/02705060.1994.9664884

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

We used radio telemetry to determine movement and habitat use of 19 paddlefish (Polyodon spathula) stocked into the Neches River system, Texas. Thirteen fish weighing 0.5–0.8 kg were released in April 1990 in the upper reaches of B.A. Steinhagen Reservoir and six fish weighing 2.4–3.7 kg were released in October 1990 in the lower reaches of B.A. Steinhagen Reservoir. Fish were tracked from April 1990 to September 1991. Five fish died within four months of release. There was a significant relation between: 1) habitat type and both water depth in which fish were found and their distance to shore and 2) season of year and both water depth in which fish were found and their distance to shore. These relations suggest seasonal patterns of habitat use. Farthest upstream movement was 270.4 km and farthest downstream movement was 161.3 km. Eleven fish remained upstream of the dam and six fish moved through reservoir floodgates or over the spillway into the lower Neches River. Our findings indicated: 1) paddlefish size relative to size of implanted radio transmitter may have a bearing on survival. 2) young paddlefish may migrate great distances shortly after stocking and 3) location of release site may influence direction of paddlefish dispersement.

ISSN:0270-5060    

DOI:10.1080/02705060.1994.9664885

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The growth of northern pike (Esox lucius) in Lake Thompson, South Dakota was assessed seasonally over a two-year period. Northern pike were short-lived; the oldest fish collected was age 8. Female northern pike lived longer than male fish, and mean length-at-age was significantly higher for females than for males. Significant increases in mean body length occurred during cool- and cold-water seasons, but no increases in mean length were found for either sex from July through August, which was the period of highest water temperature. Incremental growth in length (mm/d) for male northern pike was related to water temperature, with maximum growth rates occurring in the range of approximately 8–18°C.

ISSN:0270-5060    

DOI:10.1080/02705060.1994.9664886

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Concentrations of chlorophyll-a in waters with high average annual concentrations of suspended sediment were measured in three lakes and compared with broad band Landsat MSS satellite digital data for 104 dates between December 1976 and August 1988. Concentrations of chlorophyll-a ranged from 0.3 to 211 mg·m−3for 452 measurements. Concentrations of suspended sediment ranged from 1 to 867 mg·l−1in the same samples. In general, chlorophyll-a concentrations were inversely related to suspended sediment concentrations. Radiance and reflectance calculated from the four MSS bands increased as a function of increasing concentrations of suspended sediment. Radiance and reflectance were inversely related to the concentration of chlorophyll-a, but the relationships were not statistically significant. This study indicated that the measurement of chlorophyll-a with broad band (100 nanometer) MSS data in waters dominated by suspended sediments is not effective since the detection of the increased absorption or reflectance of radiation due to chlorophyll-a is masked by the spectral reflectance due to suspended sediments. In order to quantitatively determine chlorophyll by remote sensing in systems dominated by suspended sediment high spectral resolution information (10 to 15 nm band widths) at approximately 675 and 705 nanometers (nm) will be required.

ISSN:0270-5060    

DOI:10.1080/02705060.1994.9664887

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

We measured species richness, diversity, and abundance of fish in both shallow and deep water areas in regulated and unregulated sections of the Tallapoosa River in Alabama from July 1990 through September 1992 to compare the effects of flow regulation on fish assemblages in shallow and deep water habitats. Flow regulation had a greater effect on shallow water fish assemblages than on deep water fish assemblages. Species richness and diversity of shallow water fishes were reduced below two hydroelectric dams compared with unmodified river segments, and we attribute this to a reduction in species adapted to fluvial environments below the two dams. Additionally, the density of fish in shallow water areas of unregulated portions of the river was significantly (P<0.05) higher than the density at most of the regulated sites. No reductions in species richness or diversity below the two dams were observed for species inhabiting deep water areas. However, we collected a significantly (P<0.05) higher number of catostomid species in the unmodified river sections compared to the flow-regulated sections.

ISSN:0270-5060    

DOI:10.1080/02705060.1994.9664888

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

We placed eight 1500 L mesocosms in a 0.2 ha eutrophic cattle pond during summer 1991 to determine if zooplankton grazing, nutrients, or both control algal biomass and productivity. The three treatments: + zooplanktivorous fish (39 bluegill, mean total length = 36 mm); + zooplankton (10x ambient); and + N + P (160 μM NH4+and 10.0 μM PO43-) were duplicated and compared to ambient pond conditions and two control mesocosms. In the + N + P treatment, chlaconcentrations increased 700% in four days and then decreased to initial levels; further nutrient enrichments failed to create an algal response, probably because of grazing associated with an eightfold increase in large cladocerans. After nutrients were added to the + fish treatment, the NH4+and soluble reactive phosphorus concentrations rose and then decreased rapidly, whereas chlaconcentrations and rotifer numbers increased. When nutrients were added to the + zooplankton treatments, chlaincreased, but less than when either fish or nutrients alone were added. In small eutrophic ponds, trophic manipulations may have little effect during equilibrium conditions but do alter algal responses during nutrient pulses. An increase in large cladocerans in response to a nutrient pulse may control nuisance algal blooms, even with subsequent nutrient additions.

ISSN:0270-5060    

DOI:10.1080/02705060.1994.9664889

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

While most aquatic herbicides have undergone some toxicity testing for effects on non-target aquatic organisms, little of this testing has been conducted on early life stages of gamefish found in lakes undergoing treatment. Commercial formulations of diquat, endothall, and fluridone were selected for acute toxicity testing using very early life stages of walleye (Stizostedion vitreum), largemouth bass (Micropterus salmoides), and smallmouth bass (Micropterus dolomieu). In addition, the rates of diquat photodegradation and uptake by sediment were determined. These results were used to predict diquat concentrations in lakes of various depths. The results of the toxicity tests were compared to the predicted concentrations. Diquat, with 96-h LCSOs of 0.74–4.9 mg/L, was more toxic to these early life stages than endothall or fluridone, with 96-h LC50s of 16–130 mg/L and 1.8–13 mg/L respectively. The LC50s for endothall and fluridone were at least one order of magnitude greater than the labeled application concentrations. As the LC50s for diquat were very close to the predicted concentration, the safety margin for the use of diquat appears to be very small.

ISSN:0270-5060    

DOI:10.1080/02705060.1994.9664890

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Wintertime toxic blooms of the blue-green algaAnabaena flos-aquaehave been documented since 1989 in American Lake, a 446-ha lake near Tacoma, Washington. The toxic episodes were unusual in that algal toxicity occurred during the winter and this lake is considered to be only moderately productive. A year-long study was conducted to determine the environmental factors associated with toxic conditions. Toxic blue-green algal blooms in American Lake were associated with increased nutrient (especially phosphorus) availability following winter turnover. Phosphorus released from lake sediments under conditions of low oxygen during lake stratification fueled winter blooms of algae, including the toxicAnabaena flos-aquaestrain. The lake's extremely low iron content was insufficient to completely remove this released phosphorus from the water column during lake turnover.

ISSN:0270-5060    

DOI:10.1080/02705060.1994.9664891

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

During a short-term telemetry study to determine behavior of angler-caught and released muskellunge, an individual muskellunge was caught and displaced into a separate lake in a chain of lakes. Following its release, this female fish (980 mm) traveled 10 km in three days. The fish bypassed numerous areas with suitable habitat in which muskellunge were commonly found and returned to the area from which it was originally captured.

ISSN:0270-5060    

DOI:10.1080/02705060.1994.9664892

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor