摘要:

Fluctuating water levels and water temperatures in recent years have had an influenced the food habits of walleye (Stizostedion vitreum) in Lake Oahe, South Dakota. We collected walleye from the upper, middle, and lower regions of the reservoir in 1993 and, using the relative importance (RI) index, compared walleye food habits in 1993 with those from a similar study of Lake Oahe conducted in 1991. Rainbow smelt (Osmerus mordax) had higher RI values than other prey in all regions of the reservoir throughout 1993. In 1991, rainbow smelt dominated the diet of walleye only in the lower portion of the reservoir. Ephemeridae and chironomidae were the only macroinvertebrates found in the walleye diet; however, neither constituted a large portion of the diet in either year. Seasonal importance did, however, vary slightly among sites as diets became more diverse in the upper reaches of the reservoir. The predominance of rainbow smelt in the diet of walleye throughout the reservoir in 1993 was probably due to cooler water temperatures and increased reservoir volume. Cooler water temperatures in 1993 allowed rainbow smelt to occupy areas where water temperatures exceeded their upper thermal limit in 1991.

ISSN:0270-5060    

DOI:10.1080/02705060.1995.9663411

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We examined diel feeding chronology of six fish species in the Juniata River, Pennsylvania. Ephemeropteran nymphs were the major prey of redbreast sunfish (Lepomis auritus; 70.5%) and smallmouth bass (Micropterus dolomieu; 59.7%) during each of six 4-h intervals over a 24-h period. The main dietary component of mimic shiner (Notropis volucellus) was chironomids (42.3%), whereas spotfin shiner (Cyprinella spiloptera) mainly ate terrestrial invertebrates (50.2%). Juvenile white sucker (Catostomus commersoni) exhibited substantial diel variation in diet composition with some prey taxa composing the entire diet during some 4-h intervals and being completely absent from the diet during other periods. Bluntnose minnow (Pimephales notatus) contained mostly detritus (75.5%). Interspecific diel diet overlap (Cγ) was low among the six species except for smallmouth bass-redbreast sunfish (0.735). Mimic shiner ([xbar] = 0.302) had the highest diet overlap with other species and bluntnose minnow ([xbar] = 0.134) had the least similar. Smallmouth bass, redbreast sunfish, white sucker, and spotfin shiner all had diurnal feeding peaks. Peak food consumption of mimic shiner and bluntnose minnow occurred at midnight. Our results indicate that because of diel variation in diet composition and feeding periodicity for these six species, dietary analysis conducted at only one interval would not provide an accurate representation of the diet of these species.

ISSN:0270-5060    

DOI:10.1080/02705060.1995.9663412

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Several morphological attributes of individualMyriophyllum spicatumL. plants were studied during three summers in Fish Lake, Dane County, Wisconsin to document spatial and temporal dynamics. Measurements were taken from twelve randomly-selected plants at each of four depth intervals along two transects on five dates during each year from 1990 to 1992. Density, length, foliation, and biomass attributes of stems and branches were each influenced somewhat differently by depth and location. Plants growing in deep water were long and thin, while plants growing in shallow water were shorter and more robust, with greater relative amounts of foliation. Plants at most locations increased in length, but percent of total plant length (and biomass) comprised of foliated stem decreased over time.

ISSN:0270-5060    

DOI:10.1080/02705060.1995.9663413

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

First-year growth patterns of seven fish species were determined with weekly or monthly samples taken from water intake screens of a power plant located along Navigation Pool 9 of the Mississippi River (River Mile 679). Mean total lengths of mooneye (Hiodon terqisus), gizzard shad (Dorosoma cepedianum), freshwater drum (Aplodinotus qrunniens), and white bass (Morone chrysops) were at least 110 mm by winter (November through March), but mean lengths of black crappie (Pomoxis nigromaculatus), channel catfish (Ictalurus punctatus), and flathead catfish (Pylodictis olivaris) were 67 to 74 mm by winter. Mean total lengths at capture of all species except channel catfish increased significantly with time (P< 0.05) until September or October, after which lengths did not change. Mean lengths of channel catfish increased significantly through winter until February. Mean lengths of flathead catfish and white bass did not increase after water temperatures in fall dropped below 18 °C, and mean lengths of gizzard shad, black crappie, and freshwater drum did not increase after water temperatures dropped to 9–11 °C. Water temperature when mooneye and channel catfish ceased growing was not determined. Earlier hatching fish species were longer by winter than later hatching species.

ISSN:0270-5060    

DOI:10.1080/02705060.1995.9663414

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Swan Lake, a backwater of the Illinois River, had a smaller population of zebra mussels (Dreissena polymorpha) in 1994 compared with 1993. This reduction in mussel abundance may reflect the controlling influence of lake physical properties and interactions between waterfowl, freshwater drum, andD. polymorpha.Because this lake is inhabited by a diverse unionid fauna (at least 16 species) but by relatively fewD. polymorpha, it could function as a refugia for native mussels from the adverse effects ofD. polymorpha.Other such refugia should be sought and protected as a means of maintaining unionid diversity in the Illinois River and other rivers colonized byD. polymorpha.

ISSN:0270-5060    

DOI:10.1080/02705060.1995.9663415

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We tested prey preferences of adult (200- to 222-mm long) redear sunfish (Lepomis microlophus) on two size classes of zebra mussels (Dreissena polymorpha) and two-ridge rams-horns (Helisoma anceps) in experimental aquaria. We also tested physical limitations on consuming these mollusks and determined prey bioenergetic profitability. Redear sunfish strongly preferred rams-horns over zebra mussels, but they displayed no size preference for either prey. Ingestion was not physically limited since both prey species up to 15-mm long fit within the pharyngeal gapes of redear sunfish. Rams-horns were more bioenergetically profitable than zebra mussels and ingestion of rams-horn shell fragments was about three times less than zebra mussels. Rams-horns were somewhat more resistant to shell-crushing, but all size ranges of both prey species tested were crushable by redear sunfish. These studies suggested that the redear sunfish should not be considered a panacea for biological control of zebra mussels.

ISSN:0270-5060    

DOI:10.1080/02705060.1995.9663416

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The influence of substrate type on larval chironomid community structure was studied in a controlled experiment utilizing small artificial ponds. Wading pools containing three types of sterilized sediments of different particle size and organic content were colonized naturally over two eight-week periods. Total abundance and species composition varied with substrate type. Clay treatment ponds had the lowest abundance and were dominated byChironomusspp. Gravel and sand-silt treatment ponds were dominated byKiefferulus dux.Results agree with field studies and indicate that substrate is important in structuring chironomid assemblages in lakes and ponds. Data obtained using multiplate samplers did not agree well with data from benthic samples, indicating that artificial substrates do not always provide a representative sample of the benthic habitat.

ISSN:0270-5060    

DOI:10.1080/02705060.1995.9663417

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Grass carp (Ctenopharyngodon idella) is an exotic species which was imported into the United States in 1963 to control aquatic vegetation. Individuals escaped from ponds and subsequently spread into streams in the Mississippi River basin. We have been collecting grass carp in the Illinois River since 1990, and some of our associates have also collected grass carp in other portions of the upper Mississippi River system. The presence of juveniles (some less than 20 mm long) and adults (some diploid) in our collections leads us to believe that grass carp are reproducing in the Illinois River, and their larvae are finding suitable nursery areas in backwaters. Naturalized, reproducing grass carp populations probably exist as far north as 209 km into the Illinois River. Collections of juveniles by other researchers indicate reproduction and recruitment may also be occurring in upper Mississippi River Reaches 25, 26 and the Open River Reach below Lock and Dam 27.

ISSN:0270-5060    

DOI:10.1080/02705060.1995.9663418

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Macroinvertebrate communities in the Grensmaas stretch of the River Meuse (The Netherlands) were described for the period 1981–1990, largely based on unpublished data. Three biotopes were distinguished: (a) stones in the near-shore zone, (b) the river bottom in the near-shore zone, and (c) the deeper river bottom in the navigable section. Fifty-two taxa were found in the communities described for these biotopes: 37 on the stones in the near-shore zone, 44 in/on the river bottom in the near-shore zone and 26 in/on the deeper river bottom in the navigable section of the Grensmaas. The majority (58%) of the taxa were Chironomidae. Mollusca were represented by only eight taxa; gammarids were absent as were several pollution-intolerant groups (Ephemeroptera, Trichoptera, Coleoptera, Odonata and Plecoptera).

ISSN:0270-5060    

DOI:10.1080/02705060.1995.9663419

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

One aspect of island biogeography theory contends that a direct correlation exists between the size of an island and the species richness of an island. We applied this aspect of island biogeography theory to temporary pools. Six temporary pools were randomly selected and placed into three size categories based on the volume of water contained in each. The contents were filtered through a 0.250 mm sieve and retained. Invertebrates were identified, and counted. We found that species richness and the total number of individuals increased with pool size. In addition, the larger pools supported more functional feeding groups than smaller pools. These results were probably a reflection of greater microhabitat availability in the larger pools.

ISSN:0270-5060    

DOI:10.1080/02705060.1995.9663420

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor