摘要:

Alaskan sockeye salmonOncorhynchus nerkatypically spawn in lake tributaries during summer (early run) and along clear-water lake shorelines and outlet rivers during fall (late run). Production at the glacially turbid Tustumena Lake and its outlet, the Kasilof River (south-central Alaska), was thought to be limited to a single run of sockeye salmon that spawned in the lake's clear-water tributaries. However. up to 40% of the returning sockeye salmon enumerated by sonar as they entered the lake could not be accounted for during lake tributary surveys, which suggested either substantial counting errors or that a large number of fish spawned in the lake itself. Lake shoreline spawning had not been documented in a glacially turbid system. We determined the distribution and pattern of sockeye salmon spawning in the Tustumena Lake system from 1989 to 1991 based on fish collected and radiotagged in the Kasilof River. Spawning areas and times were determined for 324 of 413 sockeye salmon tracked upstream into the lake after release. Of these, 224 fish spawned in tributaries by mid-August and 100 spawned along shoreline areas of the lake during late August. In an additional effort, a distinct late run was discovered that spawned in the Kasilof River at the end of September. Between tributary and shoreline spawners, run and spawning time distributions were significantly different. The number of shoreline spawners was relatively stable and independent of annual escapement levels during the study, which suggests that the shoreline spawning component is distinct and not surplus production from an undifferentiated run. Since Tustumena Lake has been fully deglaciated for only about 2,000 years and is still significantly influenced by glacier meltwater, this diversification of spawning populations is probably a relatively recent and ongoing event.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0001:POSSBS>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Fecundities of the commercially important yellowtail rockfishSebastes flaviduswere compared to determine interannual variability and geographic variation, which will assist in stock assessment, characterization, and management. Gravimetrically estimated fecundities were compared in 1985–1991 between California, the southern extent of the species' distribution, and coastal waters of Washington, near the center of the species' abundance, where yellowtail rockfish are most heavily fished. California yellowtail rockfish were older, smaller in weight and length, and had smaller mesenteric fat deposits and more extensive disease and parasite pathologies than Washington fish. Egg production of this comparatively fecund viviparous fish increased linearly and sigmoidally with body weight and length, and asymptotically with age. Significant interannual differences were found in fecundities of young fish (<age 15) from California while no differences were observed in older California fish (>age 14) or in young or old Washington fish. Washington yellowtail rockfish had higher group fecundities because they were larger at age. Rate-specific fecundities were significantly higher in young Washington fish. Predictive models of fecundity were highly correlated for young yellowtail rockfish, less so for old fish. Although fecundity of young fish depended on weight, length, and age, that of old fish was age-independent. Our findings show age-dependent interannual and geographic differences in reproductive effort, which suggest population-specific reproductive life histories.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0016:TASVIF>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We assessed reproductive development of striped mulletMugil cephulusfrom the coastal waters of Louisiana. Maturation of primary oocytes began in September of each year, and by October, a synchronous group of homogeneous, vitellogenic oocytes was observed (isochronal development). Based on indirect evidence, spawning occurred from November through early January. Gonadosomatic index (GSI) values varied with size among small, mature female striped mullet, but reached an asymptote for females 330 mm in fork length (FL) and larger. Anomalous development in certain ovaries strongly influenced GSI findings and produced excessively low values. Thus, it is suggested that histological examination be included in this type of reproductive study to identify factors that are responsible for high GSI variation. Potential fecundity correlated moderately well with female size and ranged from 2.7 × 105to 1.6 × 106eggs per individual for fish that ranged from 290 mm to 445 mm FL.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0026:RDOSMI>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Red drumsSciaenops ocellatuswere sampled in North Carolina waters from October 1987 through December 1990. Ages determined from sectioned otoliths were validated by length-frequency and marginal-increment analyses, and the recapture of oxytetracycIine-marked fish. Fish growth was rapid during the first 5 years, after which annual growth increments were much smaller. Growth was best described by a continuous double von Bertalanffy growth curve, with a transition age of 4.4 years;K1, the growth coefficient for fish younger than the transition age, was 0.30/year andK2, the growth coefficient for fish older than the transition age, was 0.07/year. Maximum observed age and size were 56 years and 1,250 mm fork length (FL) for males and 52 years and 1,346 mm FL for females. Fifty-percent maturity was attained among males by age 2 at 621–640 mm FL and among females by age 3 at 801–820 mm FL. Spawning occurred from August through early October in estuarine waters of Pamlico Sound and nearshore ocean waters close to barrier island inlets. Commercial and recreational landings increased during the 1980s, with most of the harvest composed of immature, age- I fish caught during the fall. Unadjusted annual return rates (18–25%) for tagged juveniles were high. Annual survival rates based on tag–recapture data were only 6–24%, and estimates of instantaneous total mortality rates (Z) from cohort-based catch curves were 1.56–2.88 for the 1985–1988 year-classes. The relative abundance of 20–55-year-old red drums has declined 90% since 1968–1972.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0037:AGMARB>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A previously described in situ growth model was used to predict the summer growth of age-1 and age-2 broad whitefishCoregonus nasusin the Sagavanirktok River delta near Prudhoe Bay, Alaska, during 1990–1992. Comparisons of observed versus predicted weekly growth increments over the entire 9-year study (1982 and 1985–1992) yieldedr= 0.789 (N= 77;P< 0.01) for age- I fish andr= 0.522 (N= 70;P< 0.01) for age-2 fish. Based on daily comparisons of observed versus predicted mean fork length, the model was able to predict growth in 1991 and 1992 with mean squared errors (MSE) of 3.0 and 1.8 mm for age- I fish and 6.5 and 21.2 mm for age-2 fish. Results were similar to those previously described for 1982 and 1985–1989. The model failed noticeably in 1990 for age-1 fish (MSE = 48.6), and model fit for age-2 fish (MSE = 29.9) was the poorest of the 9 years examined. Poor model fit for both year-classes in 1990 was attributed to a divergence of observed from predicted growth; observed growth began lagging predicted growth about the third week of July. By the end of August, predicted mean length exceeded observed length by 13.6 mm for age-1 fish and 12.8 mm for age-2 fish. Data suggest that the divergence in growth began at the time of a massive immigration of least ciscoesC. sardinellainto the delta. We speculate that the presence of least ciscoes may have overtaxed the trophic carrying capacity of the delta, thereby curtailing the growth of young broad whitefish.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0055:AOAISG>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We assessed the effects of angling stress on nesting male smallmouth bassMicropterus dolomieufrom two lakes in southeastern Ontario. In the first portion of the study, adult male smallmouth bass were hooked and then played either briefly (<20 s) or to exhaustion (2 min). White muscle acid–base and metabolite status were used as indicators of the extent of the physiological disturbance in these fish. Angling of smallmouth bass resulted in decreases in muscle pH and energy reserves for burst activity (phosphocreatine and adenosine triphosphate), as well as increases in muscle lactate, metabolic protons (▵H+), and partial pressure of carbon dioxide (Pco2). The physiological disturbance was most severe in smallmouth bass played to exhaustion. In the second portion of the study, other adult male smallmouth bass were hooked and played as described above. Fish played to exhaustion took four times longer to return to their nests than did fish played briefly. As a result, offspring in the nests of fish played to exhaustion were exposed to more predation risk. The physiological and behavioral effects of exhaustive exercise induced by angling indicate the potential for catch-and-release angling of smallmouth bass during their spawning season to negatively affect reproductive success.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0070:EOCARA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The diel movements of seven adult burbotLota lota, 55–67 cm in total length, were seasonally monitored with sonic tags in Lake Opeongo during 1989 and 1991 to determine patterns of activity and habitat use. Burbot were inactive during daylight hours, began moving near dusk, and moved throughout each night until dawn. In the summer, burbot moved more slowly and occupied deeper water than in the spring. Swimming speed appeared to increase in the fall. Burbot occupied the same local areas within seasons and between years. Burbot were sometimes active in 20°C water for extended periods at night but moved to cooler water during the day. Burbot seemed to use an area-restricted searching pattern. None of the burbot were located in water less than 2 m deep.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0077:STOBIL>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Age-0 yellow perchPerca flavescens, sunfishLepomisspp., black crappiesPomoxis nigromaculatus, and freshwater drumsAplodinotus grunnienshad pelagic life history phases in Lake Mendota in 1988, 1989, and 1990, as determined by purse-seine sampling. The duration of the pelagic phase varied from 3 to 7 weeks and differed between species and in some cases between years within species. Age-0 yellow perch were numerically dominant through most of June and as summer progressed were replaced sequentially by black crappies, freshwater drums, andLepomisspp. By August, the pelagic community of age-0 fish was numerically dominated byLepomisspp. This temporal succession of taxa was consistent among years, although the absolute and relative abundance of taxa differed between years. Most species were distributed across the surface of the lake early in their pelagic phase, became relatively more abundant near shore later in their pelagic phase, and then disappeared from the pelagic zone. Other published studies have demonstrated that age-0 fish migrated into the littoral zone of Lake Mendota after their pelagic residence. Variability in density of age-0 yellow perch among replicate sites within depth strata was high, with coefficients of variation ranging from 48 to 154%. The mean-to-variance relationship indicated that the age-0 yellow perch were aggregated. There were significant differences in the density of age-0 yellow perch among years but not among depth strata within years. The purse seine was our preferred gear because it has been shown to catch a wider range of sizes of age-0 fish than most other sampling gear. Therefore, we believe that the temporal and spatial patterns we describe during the pelagic life history phase of age-0 fish in Lake Mendota is more accurate than those described in other studies because our data include a better representation of the larger size-classes of age-0 fish.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0084:TASDOP>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Cyprinid populations in the Appalachian Plateaus Province of Maryland may be at risk from the effects of acidification because of the high proportion of acid-sensitive streams and elevated levels of acidic deposition within the region. During 1989, we related water chemistry, physical habitat, and watershed characteristics to cyprinid distributions in 56 Appalachian streams in Maryland. These streams were dominated by two cyprinid species, blacknose daceRhinichthys atratulusand creek chubSemotilus atromaculatus. Eleven streams had a pH of 5.30 or less, an acid-neutralizing capacity (ANC) of 50 μeq/L or less, and lacked cyprinids. The remaining streams had a pH of 6.49 or more and ANC value greater than 50 μeq/L, and cyprinids were either absent or present. Streams with pH values 5.30 or less had lower ANC, higher levels of inorganic monomeric aluminum, and lower concentrations of dissolved calcium than high-pH (≥6.49) streams. Chemical characteristics were similar among high-pH streams whether or not they contained cyprinids. Gradient was the primary factor affecting cyprinid distributions in streams that had a pH of 6.49 or more. This indicates that some streams with a pH of 5.30 or less would have lacked cyprinids in the absence of acidification. We conclude that, in Appalachian streams of Maryland, cyprinid distributions are affected by factors related to surface water acidification.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0094:IOPAHO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Between October 1987 and December 1988, 732 winter flounderPleuronectes americanus, 91–380 mm total length, were collected during biweekly sampling from Narragansett Bay, Rhode Island. Left sagittal otoliths from these fish were embedded in epoxy resin, and transverse sections through the foci were prepared. With hyaline zones considered as annual increments, ages ranged from 1 to 11 for 608 winter flounder; 97% of the fish were younger than age 5. The dorsoventral otolith diameter was determined by linear regression analyses to be the best (r2= 0.90) of six “radial” axes for increment measurements. Marginal increment analyses for ages 1–4 showed that the increments, each composed of one opaque and one hyaline zone, are deposited annually, which clearly verified sectioned otolith ages for age-2 and age-3 fish. Opaque edges were prevalent in May, June, and July. Sectioned otoliths from winter flounder can provide clear increments and measurable increment widths through age 11. Two individuals read 369 sectioned otoliths and 116 whole otoliths; one individual read 155 scales twice. Precision between readers and aging methods was relatively high (average percent error, 1.5–4.5). Comparison of ages from scales and whole and sectioned otoliths from 154 fish showed no significant differences (P≤ 0.05).

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0103:AVOWFI>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor