摘要:

Embryos of sockeye salmonOncorhynchus nerkawere transplanted from Shuswap Lake, British Columbia (BC), to tributaries of Lake Ohau in the South Island of New Zealand (NZ) in 1901. This single shipment gave rise to a self-sustaining freshwater resident population that spawns primarily in Larch Stream north of Lake Ohau. We compared the genotypic (using protein electrophoresis) and phenotypic traits of the NZO. nerkawith anadromous (sockeye salmon) and nonanadromous (kokanee) populations of the species in the Shuswap Lake system. Genetic analysis confirmed that the transplanted fish had been sockeye salmon, not kokanee, and allele frequencies in the current NZ population were not significantly different from those in anadromous sockeye salmon from Scotch Creek, BC. The NZO. nerkadeveloped two life history patterns: some spent their entire rearing period in Lake Ohau, whereas others migrated downstream from Lake Ohau after 1 year to mature in Lake Benmore. These latter “migrants” grew faster and matured at a younger age than the residents. Both NZ forms were younger and smaller at maturity than their anadromous ancestors and matured at an earlier age than Shuswap kokanee. Despite their much smaller size, the NZO. nerkahad eggs that were only slightly smaller than their anadromous ancestors' eggs (96.4 mg for NZ versus 101.4 and 98.4 mg for Lower Shuswap River and Adams River, BC, sockeye salmon, respectively). In contrast, their eggs were much larger than those of comparably sized kokanee (74.4 and 68.2 mg for kokanee from the Lower Shuswap River and Sinmax Creek, BC, respectively). Fecundity of NZO. nerkawas less than that of both Shuswap sockeye salmon (because they were smaller) and kokanee (because their eggs were larger). The coloration of NZO. nerkawas consistent with descriptions of “residuals” (nonanadromous offspring of anadromous sockeye salmon parents). Taken together, the suite of traits indicated considerable phenotypic plasticity in the adaptation of sockeye salmon to the NZ environments.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1998)127<0517:GAPDOS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0002-8487    

DOI:10.1577/1548-8659(1998)127<0535:GIOBSM>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Genetic research of fishes is hampered by lack of standardized karyotypes and reliable techniques of chromosome banding. The goal of this study was to develop a standardized karyotype of channel catfishIctalurus punctatusby a variety of banding techniques and computer-assisted analysis. Metaphase chromosomes were prepared from cultured leukocytes and kidney cells of adult and juvenile fish. Silver staining and alkali treatment methods were used to reveal nucleolus organizer regions (NOR) and the location of constitutive heterochromatin (C-bands). Chromosomes were treated with 10 different restriction enzymes, stained with Giemsa, and examined for banding patterns. The chromosomal data were analyzed with two computer software packages. The 29 chromosomes were classified into eight distinct groups based on morphology and size. The NOR were located on a pair of medium-sized submetacentric chromosomes (designated as D-11); this was consistent among cells from different specimens. The C-bands were small and restricted to centromeric regions and were useful for homologous pairing. A standard karyotype of CBG-banded chromosomes (C-bands visualized by treating with barium hydroxide and staining with Giemsa) was developed. The restriction enzymeMscI produced informative banding patterns with dark telomeric bands and clear centromeric regions. The enzymeHind III was most informative, yielding linear banding patterns that were consistent between members of homologous pairs. Our study provides a fundamental step in genome mapping of fishes. Standardization of the channel catfish karyotype and chromosome banding will facilitate physical mapping of genes in this important culture species.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1998)127<0551:SOTCCK>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

To characterize the marine distribution of New Zealand adult chinook salmonOncorhynchus tshawytscha, we analyzed data on chinook salmon taken off the South Island east coast as a bycatch of a commercial fishery dominated by bottom trawling on the continental shelf and slope in depths up to 1,000 m. Chinook salmon, widely but sparsely distributed out to depths of 100 m throughout most of the year, showed a strong tendency to concentrate off Banks Peninsula (latitude 43°45′S) in midsummer (December–February). Of 161 metric tons taken between 1984 and 1988, 151 metric tons were taken by larger trawlers capable of towing nets with 6-m headline heights at speeds of up to 6.5 km/h. Most chinook salmon caught at sea were maturing adults returning to nearby rivers, such as the Rakaia, rather than immature fish associated with the oceanic phase of their life cycle. The low incidence of immature fish and the lack of data for offshore waters preclude any definitive conclusions about the extent to which chinook salmon travel offshore, but our results are consistent with their northern distribution being bounded by subtropical water north of about latitude 43°S and their eastern distribution being bounded by cold, low-productivity sub-Antarctic waters.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1998)127<0560:OADOAC>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Variation in advection or other physical forces may accelerate or delay arrival of young marine fishes into productive nearshore habitats, thereby affecting the length of the available growing season. The bluefishPomatomus saltatrixis an oceanic spawner whose juvenile stages, upon entry into estuarine waters, become piscivorous and thereby experience greatly increased growth. Size attained during the growing season may therefore be determined by time of arrival into estuarine habitats. We exposed bluefish recently recruited to an estuary to three diet shift treatments in which test fish were fed adult brine shrimpArtemiasp. for 0, 10, or 20 d before they were switched to piscine prey. Bluefish that had a delayed onset of piscivory were smaller after 40 d of growth, indicating that they did not fully compensate for prior periods of slow growth. These bluefish did exhibit immediate moderate growth compensation (about 6% over 10 d) resulting from increased consumption rates, but relatively low growth efficiencies prevented full recovery of their growth losses. Low growth efficiencies may have resulted from an induced developmental handicap or an energetic penalty for prolonged feeding on anArtemiadiet. The timing of age-0 bluefish recruitment into estuarine environments can have a lasting influence on size attained during the first growing season.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1998)127<0576:EOADOO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

I examined size-selective predation by small (159–239 mm, total length, TL) piscivorous walleyesStizostedion vitreumfeeding on three sizes of yellow perchPerca flavescens.The size distributions were presented in three experiments with yellow perch size standardized to walleye size by using prey/predator TL ratios (PPTLRs). Experiment 1 included PPTLRs of 0.2, 0.3, and 0.4; experiment 2 included PPTLRs of 0.3, 0.4, and 0.5; experiment 3 included PPTLRs of 0.4, 0.5, and 0.6. Attack and consumption rates did not differ among prey sizes in experiment 1, but they were greater on small prey in experiments 2 and 3. For prey sizes common to more than one experiment (PPTLRs 0.3, 0.4, 0.5), selectivity was experiment-dependent. There was increased selection for a specific prey size as it became relatively smaller compared with the sizes of alternative yellow perch. Active selection, as measured by attack rate, was an important contributor to patterns of yellow perch consumption by walleyes.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1998)127<0588:PBSWOY>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Field observations of a variety of fish species at different latitudes suggest that there is an inverse (countergradient) relationship between growth rate within the first growing season and the length of the growing season. In this study, larvae of striped bassMorone saxatilisfrom four different latitudes—Hudson River, New York (NY) (41°N); Nanticoke and Patuxent rivers, Maryland (MD) (38°N); Santee–Cooper river system, South Carolina (SC) (33°N); Apalachicola River, Florida (FL) (30°N)—were raised in captivity under identical conditions to determine if differences in growth could be detected among the populations. Larvae from two mothers per latitude were reared at two temperatures (17°C and 21°C) with replication. The general result was that MD and NY larvae exhibited the highest growth rates and SC larvae grew the slowest. At 17°C, a significant difference in standard length growth rate was detected between MD larvae, the fastest growing population, and SC larvae, the slowest growing population. At 21°C, the rank order for growth in standard length was MD = NY > FL = SC. No significant differences in dry weight growth were found at 17°C. At 21°C, a significant difference in dry weight growth rate was detected between NY larvae—the fastest growing population—and SC larvae—the slowest growing population. Significant differences among the populations also were found in egg weight and egg oil volume. However, these maternal effects did not exert a statistically significant influence on growth rate. Results indicate the existence of a countergradient relationship between larval growth rate and the length of the growing season among striped bass from different latitudes.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1998)127<0598:VILGRA>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This experiment examined the metabolic costs and physiological consequences of growth and energetics of juvenile rainbow troutOncorhynchus mykissin a warmer, more polluted winter environment. Growth under the warm-winter conditions was approximately three times less than equivalent growth of experimental and control groups previously observed under warm-summer conditions. However, during winter exposure, wet weights and total lengths were roughly 30% higher in the “warmed” fish than in the base temperature group due to a combination of greater appetite and higher energy conversion efficiency. Oxygen consumption and nitrogenous (ammonia + urea) waste excretion rates were 30–40% higher for “warmed” fish but were less than one-third of levels recorded in the summer. A corresponding increase in food intake was associated with elevations in whole-body protein and lipid but not carbohydrate. Addition of 70 μmol ammonia/L elevated nitrogenous waste excretion much like in the previous summer exposure, but over this winter period it did not result in increased weight gain. Plasma total ammonia was not significantly higher in the ammonia-exposed fish, unlike the summer experiment. Although nitrogen retention efficiency was much lower for overwintering juvenile trout fed to satiation, the metabolic cost of nitrogen retention (growth) was similar to that of juvenile trout exposed during summer. We conclude that overwintering juvenile trout fed unlimited ration and subjected to simulated warming, both alone and in combination with elevated environmental ammonia, will exhibit increased growth with only a slight elevation in energetic cost.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1998)127<0611:TMCAPC>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

We investigated resource use by early life stage (≤30 mm, total length) humpback chubGila cypha, speckled daceRhinichthys osculus, bluehead suckersCatostomus discobolus, and flannelmouth suckersC. latipinnisin the Little Colorado River, a tributary to the Colorado River in Grand Canyon, Arizona. Significant logistic regression models for habitat use were developed for all species pairwise combinations except flannelmouth sucker–humpback chub and flannelmouth sucker–speckled dace; correct classification probabilities ranged from 54% to 81%. Parameters used in discriminating among habitat use included depth, distance from shore, cover, and substrate. Logistic models were also developed to compare habitat use among larval stages within species, and most combinations produced significant models. Classification probabilities ranged from 60% to 95% in these models with the variables of depth, distance from shore, current velocity, cover, and substrate contributing to the various models. Behavioral observations revealed significant differences in vertical use of the water column and feeding locations among bluehead suckers and the two cyprinids. Diet analysis supported differences observed in feeding location and also identified some differences in diel feeding patterns. These differences in habitat use, behavioral time budgets, and diet indicate that some resource partitioning occurs among larval fishes in the Little Colorado River. Further laboratory study is needed to verify the mechanisms that sustain differential resource use in this system.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1998)127<0620:RUBLAE>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Radio telemetry was used to monitor the diel movement of 22 brown troutSalmo trutta(268–446 mm in total length, TL) in the Chattooga River watershed. Forty-seven diel tracks, locating individuals once per hour for 24 consecutive hours, were collected for four consecutive seasons. High variability in movement both within and among individual brown trout resulted in similar seasonal means in total distance moved, diel range, and displacement. The majority of fish moved a total distance of less than 80 m within a diel range of less than 80 m and had a displacement of less than 10 m. Brown trout were more likely to occur in pool habitat independent of season or period of the day. Hourly movement patterns differed among seasons. During the winter and fall, trout moved only around sunrise; during the spring, they moved around sunrise, sunset, and intermittently throughout the night. Large brown trout (>375 mm, TL) were found to move greater total distances and establish wider diel ranges than small brown trout. Overall, most brown trout exhibited restricted diel movement within a single riffle–pool or run–pool sequence.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1998)127<0630:DMOBTI>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor