摘要:

A biologically important feature of the Beaufort Sea is the occurrence of a band of relatively warm and brackish water (5–10 C, 10–25‰) that lies adjacent to the shoreline in summer. This estuarine band extends the length of the coast (750 km); it is very narrow (usually 2–10 km wide) and is often distinctly different from adjacent marine waters (-1 to 3 C, 27–32‰). The band provides important feeding habitat for anadromous and marine fishes. Dominant anadromous species are Arctic cisco Coregonus autumnalis, least cisco C. sardinella, and Arctic char Salvelinus alpinus which enter previously frozen nearshore waters each summer and feed extensively on an abundant supply of epibenthic mysids and amphipods. These fishes disperse parallel to the coastline, remaining in the estuarine band. Dominant marine species are Arctic cod Boreogadus saida and fourhorn sculpin Myoxocephalus quadricornis, which enter nearshore waters later in summer as salinities increase. In winter, the estuarine band is absent and most anadromous species return to North Slope drainages to spawn or overwinter; marine species remain under nearshore ice but eventually vacate shallow waters, which freeze solid to a depth of 2 m.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1984)113<265:FUOCWO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

We examined food and habitat use of sympatric smallmouth bass Micropterus dolomieui and rock bass Ambloplites rupestris in the Current and Jacks Fork rivers, Missouri. Use of food resources was similar between species and within a species. On a total caloric basis, the importance of prey ranked crayfish > fish > insects. The similarities of both prey types and the size selection of prey indicated that food resources were not a mechanism of ecological segregation between rock and smallmouth bass. Habitat use was evaluated by underwater observation. Location of both species was highly correlated with some aspect of cover, especially woody structure. Although cover use overlapped among size classes and species, rock bass were more often associated with rootwads and smallmouth bass with log complexes (aggregates of logs and branches). Cover use was independent of rock bass size, but smallmouth bass shorter than 350 mm long more often used vegetation and boulders and were more often found in open water than were smallmouth bass larger than 350 mm. Smallmouth bass used woody structure associated with higher current velocities more often than did rock bass. A positive relation between water depth and fish size was evident for each species, but water depth appeared unimportant in interspecific segregation.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1984)113<283:RUBSRB>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The effects of elevated temperatures on reproduction of smallmouth bass Micropterus dolomieui were evaluated in large outdoor channels (112 m long; 0.05 hectare) on the Tennessee River in Alabama, the southern limit of the species' native range. Replicated treatments were the ambient temperature of the Tennessee River and 3, 6, and 9 C above ambient (December 1978-October 1979). Peak egg deposition was advanced about 8 days per 3 C increase over ambient but occurred at temperatures (18–22 C) within the normal range reported for spawning by this species (15–26 C). Peak spawning time ranged from March 22 in the +9 C treatment to April 16 in the ambient regime. Duration of spawning periods (11 to 19 days) in the four temperature treatments was similar to those reported for natural populations. Survival rates from egg deposition to emergence from the nest were about 90% in all treatments. A maximum weekly average temperature of 26 C during the spawning season will allow survival of smallmouth bass eggs and larvae. This study indicated that the southern limit of the original range of smallmouth bass was not determined by the influence of temperature on reproduction and that above-normal temperatures would not affect reproduction and recruitment to the extent that low temperatures affect northernmost populations.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1984)113<295:SBRIET>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Fecundity, total egg potential, and survival from egg to fall juvenile for smallmouth bass Micropterus dolomieui in Nebish Lake, Wisconsin, were determined during 1979–1981. Most female smallmouth bass first matured at age III (72.5%), and all were mature by age IV. Estimated egg potential for smallmouth bass in Nebish Lake was 1,649,000 in 1979; 2,989,000 in 1980; and 1,002,000 in 1981. Survival from potential egg deposition to fall young of year was 0.3% in 1979, 0.1% in 1980, and 0.5% in 1981.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1984)113<304:FSETJO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

In late summer 1979, 948 leopard sharks Triakis semifasciata were tagged and released into San Francisco Bay after being injected with the bone-labeling reagent oxytetracycline (OTC). The fluorescent time mark was compared to new growth zones in the vertebral centra of tagged fish recovered over 3 years to determine how often the calcified bands are formed. As of 31 December 1982, 25 vertebral samples were recovered and examined. Although OTC deposition was variable, an intense fluorescent mark was evident in 12 individuals. The results confirm that one opaque (highly calcified) zone and one translucent zone are deposited per year, and that these zones can be used reliably in aging this species within the size group examined. The progression of band formation indicates that opaque zones probably form sometime between May and September.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1984)113<308:TOVDIT>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Age, growth, mortality, and yield per recruit of the little skate Raja erinacea in the Georges Bank-Delaware Bay region were investigated from trawl-survey data collected during 1968–1978. Eight age groups were observed in the population. The parameters of the von Bertalanffy growth equation are asymptotic length L∞= 52.73 cm; growth coefficient K = 0.352; and hypothetical age at zero length t0= -0.449 years. The length-weight relationship for both sexes combined over seasons is log10W = -2.641 + 3.229 log10L, where length L is in centimeters and weight W is in grams. Estimates of total instantaneous mortality rates Z for fully recruited ages (age 5 and older) ranged from 0.54 to 1.76 between 1968 and 1978. Natural-mortality values M ranged from 0.4 to 0.5; fishing-mortality values F ranged from 0.14 to 1.36, depending on the value of M assumed.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1984)113<314:AGAMOT>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Age, growth, mortality, and reproduction of a relatively unexploited stock of snowy grouper Epinephelus niveatus from the lower Florida Keys, were studied during April 1978-July 1981. Biological statistics were derived from 309 snowy grouper. Ages, determined by otolith sectioning, ranged from 0 to XXVII. Back-calculated mean total lengths (TL) ranged from 209 mm at the end of year 1 to 909 mm at the end of year 15. The von Bertalanffy growth equation for snowy grouper was Lt= 1,320{1 - exp[-0.087(t + 1.013)]}, where L = total length (mm), and t = age (years). Annual mortality, determined by catch-curve analysis, was 16%. Full recruitment into the fishery occurred at 575–600 mm TL and at age VIII. The snowy grouper exhibited protogynous hermaphroditism. Most females (81%) were sexually mature by age IV to V. Males did not appear until age VI, but they comprised 40% of all fish of ages VIII or older. These biological findings preliminarily suggest that snowy grouper stocks in the Florida Keys cannot support an extensive and sustained commercial fishery.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1984)113<322:PPOARU>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Territorial behavior of the American lobster Homarus americanus was studied by observing shelter occupancy at a site on the northeast coast of Newfoundland year-round. Lobsters left their shelters only at night; nocturnal activity began at dusk, peaked around 2–3 hours after darkness, and dropped to a very low level before dawn. Nocturnal activity was virtually nil during winter, increased with increasing temperature during July, peaked during August, and declined during autumn as temperature dropped. Although lobsters commonly returned to the same shelter after nocturnal wandering, in July-August half the shelters occupied during one of two consecutive daily checks were empty the other day. Within the 0.19 km2study site, individual lobsters observed 1–2 months occupied an average two shelters; those observed for 11–12 months occupied an average five shelters. During these same observation periods, the same lobster was in the same shelter for 77% and 48% of the sightings, respectively. Occupancy rate was about 70% for shelters observed up to 8 months, and about 50% for those observed over longer periods. Shelters were occupied by only one lobster at a time, but each accommodated an average 2.4 different lobsters over 1–4 months, and 10.7 lobsters over 25–30 months. Of the lobsters sighted in the study area at least five times, 39% returned to a particular shelter after absences ranging to more than 7 months.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1984)113<330:TBOTAL>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

American lobsters Homarus americanus in Bonavista Bay, Newfoundland, observed by scuba divers, moved within a 30-m depth range to deep water in autumn and back to shallow water in spring. During summer, most animals occurred at depths more shallow than the thermocline, which usually lay at 5–10 m. Autumn movements appear related to increased turbulence due to frequent storms and to breakdown of the thermocline. The animals became inactive and remained at depth during winter but returned to shallow water as temperature and activity increased during spring.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1984)113<336:SSMOTA>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Investigations were conducted with underyearling coho salmon Oncorhynchus kisutch reared in marine net-pens to determine the extent of genetic involvement in traits associated with smoltiffcation and saltwater adaptation and to assess genetic relationships among these traits. Data were obtained from two brood years (1977 and 1978) of experimental families formed by a nested mating design and consisted of length and weight measurements and morphological smolt assessments at 7 and 11 months postfertilization. Reasonably high heritability estimates (h2= 0.22–0.29) were obtained for all smoltification traits except survival (h2= 0.07). Correlation estimates among the variables suggested a strong genetic relationship between size and smoltification traits, with the exception of percent survival. The use of these estimates for genetic improvement was illustrated by two types of selection index. Substantial increases in smoltification and saltwater-adaptation traits appeared to be possible.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1984)113<339:SITNCO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor