摘要:

The freshwater migration of elvers of the American eel Anguilla rostrata was continuously monitored at the freshwater interface and three locations in the lower stretches of a Rhode Island brook in 1980. Most elvers arrived at the freshwater interface in May and were incompletely pigmented. Although their initial arrival coincided with a large increase in water temperature, subsequent captures at the interface did not correlate with any measured environmental variable including water temperature, time of day, and tidal condition. Elvers appeared to delay upstream migration at the interface while experiencing behavioral and physiological changes. Two hundred meters above the interface, elvers were caught primarily at midday and capture records showed a significant 14.8-d periodicity corresponding to, but lagging behind, that of spring tides. The onset of upstream migration may have been triggered by changes in water chemistry caused by the intrusion of estuarine water during high spring tides. Further upstream, captures persisted through October and lacked both diurnal and 14.8-d periodicity. Migration in fresh water appeared highly stochastic; light and water temperature showed a weak positive correlation with some capture rates, and rain occasionally influenced migration at one location by altering river flow. The behavioral changes that elvers undergo during their entry into fresh water, coupled with the apparent influence of local hydrographic conditions on migration, may explain discrepancies among prior studies. The behavior of elvers of the American eel is similar to that of other species of freshwater eel.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<258:ECOTFM>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Fish species composition and richness were compared among an unaltered New Jersey salt marsh and marshes altered for mosquito control, based on monthly seine collections over a year. Impounded marshes (stop-ditched and low-level impoundments) had distinctly different fish assemblages from that of an unaltered marsh. Marshes altered by open marsh water management (OMWM) techniques had tidal flows and assemblages similar to that of an unaltered marsh. The most pronounced dissimilarities in species composition were attributable to differences in salinity. Freshwater and oligohaline species dominated in low salinities, such as in some impounded areas. In the higher-salinity areas, as in OMWM and unaltered marshes, a typical estuarine assemblage was abundant. Movements of some species from OMWM and unaltered sites in winter caused characteristic changes in faunal composition and abundance. Among impoundments, however, seasonal patterns of species composition, richness, and abundance varied inconsistently. Regardless of type of alteration, salinity and habitat preference appeared to account for most of the variation in species composition and richness.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<269:FSCINJ>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Length and age at maturity were determined for tilefish Lopholatilus chamaeleonticeps collected off the Georgia coast during the reproductive season. Fifty percent of the females were mature at a total length (TL) of 500 mm and an age of 6 years (the youngest female collected), whereas 50% of males were mature at 450 mm TL and 5 years of age (the youngest male collected); true sizes and ages of median maturity may be less. Fecundity estimates increased nonlinearly with tilefish weight, length, and age and ranged from approximately 0.85 × 106to 8.5 × 106eggs for fish ranging from 573 mm TL (2.0 kg, 8 years) to 899 mm TL (8.9 kg, 20 years), respectively. The relationship between fecundity (F) and length was: LogeF = (4.749 logeTL) - 16.508; r2= 0.93; N = 31. We observed disproportionately large numbers of females at smaller lengths and of males at larger lengths. This would be expected if protogynous hermaphroditism were common among tilefish in the South Atlantic Bight. Skewed sex ratios, however, may have been caused by sex-specific differential growth rates because (1) transitional ovotestes were not observed; (2) although previtellogenic oocytes were present in approximately 1% of testes examined, neither vitellogenic nor early stage atretic oocytes were present; and (3) testes never contained evidence of an ovarian lumen.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<279:RDOTFT>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Home range areas of largemouth bass Micropterus salmoides floridanus in two central Florida lakes varied from 0.01 to 5.16 hectares, and maximum home range dimensions ranged from 50 to 2,364 m, based on 2,047 radio locations of 22 fish from August 1979 to May 1981. Greatest average daily movements occurred during June, May, and February; the smallest were in August. Several largemouth bass migrated during the spawning season as far as 3 km from their home ranges to wave-protected sites within canals. Largemouth bass were often located in small areas of their home range and occupied panic grasses Panicum spp., stands of cattails Typha sp., and spatterdock Nuphar luteum more often than other available vegetation types and open water. A segment of the largemouth bass population remained offshore: 36% of the tagged fish were at least 10 m from shore 25% of the time. Studies such as this should facilitate identification of habitat use by fish, projection of realistic harvest rates, and formulation of predator stocking policies and fishing regulations.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<286:HRSMAH>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A 3-year study was conducted of growth and condition of northern largemouth bass Micropterus salmoides salmoides and F1hybrid largemouth bass (male northern smallmouth bass M. dolomieui dolomieui x female largemouth bass) stocked together in diverse pond treatments. Six drainable 0.4-hectare ponds in southern Illinois were initially stocked with similar numbers of half-sibling largemouth bass and F1hybrid larvae produced in the laboratory. Most populations were censused and restocked each spring and fall through three growing seasons (1979–1981). Supplementary data were generated by introducing age-1 largemouth bass and F1hybrids into two larger ponds containing mature populations dominated by largemouth bass and bluegills. Growth of pure largemouth bass was significantly faster than that of half-sibling F1hybrids in all populations studied each year, regardless of treatment, although third-year growths in the 0.4-hectare ponds were complicated by a differential response to tagging. After the initial stocks of pure and F1hybrid bass reached age 1, samples of their pond-spawned, age-0 progeny were subjected to starch gel electrophoresis to distinguish pure largemouth bass from those containing smallmouth bass alleles (F2and backcrossed individuals). In all cases, growth by pure age-0 largemouth bass was equal to or significantly greater than that by fish having smallmouth bass alleles (P < 0.05).

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<296:CGONLB>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Age-0 chinook salmon Oncorhynchus tshawytscha (mean length, 52.4 mm; mean weight, 1.4 g) were stocked in two small lakes in southeastern Alaska to determine whether the lakes could produce chinook salmon smolts. The lakes were without fish before 15 July 1982 when 4,714 fish/hectare of lake area were stocked in Tranquil Lake (1.4 hectares) and 4,561 fish/hectare were stocked in Larry Lake (3.4 hectares). The fish ate large (> 1.5-mm-long) zooplankton and grew rapidly during the first 3 weeks. However, growth rates declined markedly when large zooplankton disappeared from both lakes. Then fish primarily ate benthic invertebrates and cladocerans in shallow lake areas, even though small (< 1.5-mm) copepods were abundant. Of the chinook salmon stocked in Tranquil Lake, 42% emigrated as age-I smolts; of those stocked in Larry Lake, 38% emigrated as age-I smolts. Smolts from Tranquil Lake were twice as large (14.3 g versus 7.1 g) as those from Larry Lake. Net yield emigrating smolts was 21.1 kg/hectare in Tranquil Lake and 6.7 kg/hectare in Larry Lake. The large number of chinook salmon stocked in the lakes prematurely depleted the large zooplankton, thereby limiting size and number of smolts produced. Shoal, defined here as the area of lake bounded by the shoreline and a bottom contour equivalent to the maximum compensation depth (99% extinction of surface light), was important in determining smolt yields because most fish foraged in shallow (<3-m-deep) water. For greatest tissue production of juvenile chinook salmon and subsequent yield of smolts in lakes similar to Larry and Tranquil lakes, 2,500 fish should be stocked for each hectare of shoal.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<305:PAYOJC>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Juvenile (14–16 cm total length) and adult (24–26 cm) smallmouth bass Micropterus dolomieui were studied in a laboratory stream tank to determine the influence of light, current velocity, substrate, and cover on habitat selection. These factors were varied singly and in combination for ranges of 30–4,000 1x light intensity; 1–47 and 0–20 cm/s current; substrates of sand (1 mm), gravel (15–40 mm), boulders with cobble filler (250 mm with 50–100 mm), and boulders with cobble removed; and three types of clear and opaque covers. Fish exhibited strong preferences for slow current (< 10 cm/s), low light (<300 1x), and cover that provided slow current and low light. Substrate was only important when fish could get into the interstices. Juveniles selected slightly slower current speeds and lower light intensities than adults, but were similar in all other respects.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<314:HSBSBI>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Habitat selection by smallmouth bass Micropterus dolomieui in shallow pools of the Flat River, Michigan, during summer 1981 and 1982 was related to the distribution of substrate type, depth, and current velocities. When current velocity was increased through manipulation, smallmouth bass reduced time spent in a habitat, foraged less, and moved more. Manipulation of light intensity between sunlit and shaded habitats did not influence use of habitats by smallmouth bass. When smallmouth bass behavior and habitat choice were observed without habitat manipulation, the fish chose gravel- to boulder-sized substrate and they avoided sand and silt substrates. Areas deeper than 45 cm were preferred by Flat River smallmouth bass; however, preference for deep areas was directly related to fish length in 1982. Areas of reduced current velocity, generally less than 15 cm/s, also were preferred. Smallmouth bass spent much of their time in foraging-related activities; up to 40% of fish between 10 and 18 cm long were observed feeding in association with northern hog suckers Hypentelium nigricans. In contrast to laboratory experiments on habitat choice by smallmouth bass that lacked prey, Flat River smallmouth bass selected specific substrate types and were more active than fish in the laboratory, probably in response to prey distribution.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<322:HSBSBI>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Log drives in Maine from the 1830s to 1976 left an estimated 3.6–7.2 × 106m3of pulpwood logs submerged in the Kennebec River system, principally in Wyman Lake and Indian Pond. Because favorable economics have led to commercial log salvaging, we assessed the ecological value of submerged pulpwood logs in Wyman Lake. Three species of fishes, longnose suckers Catostomus catostomus, white suckers C. commersoni, and golden shiners Notemigonus crysoleucas, showed an attraction to submerged logs. Yellow perch Perca flavescens, the most numerous fish species collected, did not exhibit a clear association with submerged logs. Food habits of yellow perch shifted from a largely planktonic diet in areas lacking submerged logs to a diet dominated by benthic macroinvertebrates in areas containing logs. The amount of bark in the sediment was highest at the sites containing the most submerged logs, particularly in the former log holding area, but this had no clear effect on invertebrate biomass. Total biomass of macroinvertebrates was significantly greater in the sediment than on logs in all sites. Because logs are being covered with sediment at a relatively rapid rate, the ecological importance of this submerged habitat is continually changing, particularly in shallow areas.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<335:EIOSPL>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Three consecutive year classes of juvenile chum salmon Oncorhynchus keta were vaccinated with Vibrio spp. bacterin, marked, and released into the marine environment. The return rates of adults from these releases were similar to those of unvaccinated control groups for two of the three year classes and were significantly lower for one of the year classes. There was no difference in size or age distribution at return between the vaccinated and control groups; thus, vaccination procedures did not increase survival or growth of these freely migrating chum salmon.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<343:GASTAO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor