摘要:

We examined rate of development to alevin hatching and fry emergence, embryo and alevin survival, and alevin and fry size for five Pacific salmon species. There was little difference among values for hatching and emergence time predicted by a modified thermal sums model, power law model (log-inverse Belehrádek), or quadratic model. Coho salmonOncorhynchus kisutchhad the fastest rates of development to hatching and emergence of the five species investigated; rankings for the other species depended upon temperature range. Coho salmon embryos had the highest survival rates at low incubation (1.5°C) temperatures. Embryos of pink salmonO. gorbuschahad the lowest survival at temperatures less than 4°C. For all five species, incubation temperature was the more important factor in determining alevin length, and egg size was the more important factor in determining alevin weight. Egg weight was a major determinant of fry weight at emergence. Rates of development to hatching and emergence, and alevin and fry size, differed by species in response to changes in temperature, Coho salmon alevins and fry were proportionately larger at 4°C than at 8°C or 12°C, but alevins and fry of pink salmon and chum salmonO. ketawere largest at 8°C. Variation in development characters of Pacific salmon reflected adaptations to each species' life history pattern.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1990)119<0927:TESADO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

We compared spontaneous locomotor activity and thyroidal activity between juvenile yellow American eelsAnguilla rostratacaught climbing waterfalls (migratory) and juvenile yellow American eels captured in an estuary (sedentary). Migratory fish were three times more active than sedentary fish during the first day of the experiment, both in natural light–dark conditions and in constant darkness. Migratory fish also had a mean concentration of plasma thyroxine (21.6 ng/mL) twice as high as that of sedentary fish (9.9 ng/mL). Mean concentrations of plasma triiodothyronine differed little between migratory fish (4.3 ng/mL) and sedentary fish (4.8 ng/mL). These results suggest that the thyroid gland is associated with migration of juvenile yellow American eels because no other life history transition that could involve the thyroid was occurring in the migratory individuals.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1990)119<0946:LAACOT>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

We examined morphological criteria to determine nutritional condition, assessed recent feeding activity by examining gut fullness, and examined recent growth patterns from otoliths to determine if the Mississippi River plume front enhances feeding opportunities for larvae of spotLeiostomus xanthurus. A greater percentage (35%) of starved larvae, as determined by morphological criteria, occurred at the plume front than well inside (19%) or well outside (15%) the plume. Considerable variability in the incidence of starvation occurred within and between stations, especially at the plume front. The majority of spot larvae, regardless of capture location, had only a small volume (<0.050 mm3) of food in their guts. The proportion of larvae that had 0.050 mm3or more food in their guts was equal at the plume front, well inside, or well outside the front. A low correlation (r= −0.56) between food volume and percent starvation, although statistically significant (P< 0.05), may be explained by the high variation in both variables and the different time scales of each. Gut fullness is a measure of feeding success on a scale of hours, whereas nutritional condition is a measure on a scale of days. There was minimal association between instantaneous growth rates, gut content volumes, and the degree of starvation. Larvae that exhibited the highest recent growth rate past 3 d of life) were considerably larger for any given age than those with low rates. Our inability to demonstrate consistently that larvae have a nutritional advantage when associated with the Mississippi River plume may reflect the transitory and dynamic nature of the plume front.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1990)119<0957:NCOSLA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Diet and growth of age-0 white perchMorone americanaand age-0 yellow perchPerca flavescenswere compared during July–October 1980 and 1987. Both fish species fed onDaphnia pulexin 1980 and growth was rapid; prey biomass per gram of fish was 2–12 times higher for white perch than for yellow perch. In 1987, white perch consumed up to three times more prey biomass than yellow perch, but the subsequent disappearance ofD. pulexcaused both fish species to switch to macroinvertebrates and growth of both species declined. Between 1977 and 1987, mean weights and specific growth rates of white perch exceeded yellow perch by October in all years, and weights of white perch were closely tied to the density ofD. pulexin late summer–early fall (Spearman's rank correlation = 0.58,P= 0.07). Diet overlap for age-0 white and yellow perch was high whenD. pulexwas present, and the potential for interspecific competition was greatest when these fish were similar in length. Because of a prolonged spawning period, age-0 white perch had a wide range in lengths, which enabled them to feed on a broad size range of prey. As a result, predation onD. pulexby white perch was exerted over a wider size range than was exerted by yellow perch. Such circumstances may allow daphnids to persist when age-0 white perch are abundant. Consequently, competitive interactions between young white and yellow perch appear to be asymmetric, because the ability of large cohorts of yellow perch to collapseDaphnia pulexpopulations has greater effect on white perch growth than large cohorts of white perch have on yellow perch growth.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1990)119<0966:DGAPCI>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The growth and abundance of yellow perchPerca flavescensin Saginaw Bay have varied historically. Changes in growth have been ascribed to many causes, including density and genetic composition of the fish stock, both of which are also believed to vary with location in the bay. The objectives of this study were to compare growth and maturation of yellow perch from inner and outer Saginaw Bay, to investigate the existence of different fish stocks, and to compare growth of yellow perch in Saginaw Bay to growth in other locations to determine the degree of stunting. Yellow perch were collected from four sites in inner and outer Saginaw Bay from 1983 to 1985. Size distributions differed between the inner and outer bay sites: larger and older fish were more common in the outer bay. Percentage of body water, body energy density, gonadosomatic index, and age at maturation did not differ between the inner and outer bay sites. Growth in weight, total body energy, and condition factors differed significantly. These results indicate that growth conditions differ between the inner and outer bay, but the fish populations may not be isolated completely, as has been suggested. Results also suggest that the growth differential has not caused large geographic differences in growth rate, but has caused small condition differences. Yellow perch growth is poor in Saginaw Bay, and the fish appear unable to store substantial energy reserves at any time of year. It appears that behavioral differences between young and old fish may cause the differential distribution of fish by size in Saginaw Bay.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1990)119<0976:ESGAMO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

To assess the role of commercial fishing in the destruction of lake troutSalvelinus namaycushin Lakes Huron, Michigan, and Superior in the 1940s and 1950s, we reviewed the literature and analyzed catch and effort data for U.S. waters by regression analysis. There is abundant evidence of the effect of the sea lampreyPetromyzon marinusin the destruction of lake trout, but some have claimed that fishing also was influential. We considered that a persistent, significant decrease in catch per unit of effort before and in the first few years after the sea lamprey was first found in a lake would be evidence of overfishing. We found no convincing evidence of overfishing in Lakes Huron and Michigan. Lake trout probably were overfished in Lake Superior before the sea lamprey became a major influence. We conclude that statements that lake trout were destroyed in Lake Huron or Lake Michigan by a combination of overfishing and the sea lamprey are not justified. The same claim applied simply to the Great Lakes is ambiguous, for it may be construed that lake trout were overfished in all the lakes. More critical analysis of evidence for our beliefs and hypotheses is recommended.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1990)119<0985:LTSLAO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

When lake troutSalvelinus namaycushwere subjected to a single attack by a sea lampreyPetromyzon marinusin laboratory tests in 1986, percentage mortality was significantly higher in small fish (64%; 469–557 mm;N= 67) than in medium (44%; 559–643 mm;N= 45) or large fish (43%; 660–799 mm;N= 47). Additional studies conducted in 1987 with 55 medium (559–650 mm) and 52 large (660–825 mm) lake trout confirmed that there was no difference in mortality between the two larger size-groups. Mortality declined in lake trout over 559 mm, but was still greater than 43%. This level of mortality and the sea lampreys' apparently active selection of larger fish indicated that, contrary to previously published opinions, large size in lake trout (up to ∼800 mm in length) might not allow better survival from single sea lamprey attacks.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1990)119<0996:EOLTSO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Genetic variation in resistance to bacterial kidney disease (BKD) was investigated between and within the Robertson Creek and Kitimat River strains of coho salmonOncorhynchus kisutchfrom British Columbia. For each strain, juvenile fish from 20 pairs of paternal half-sib families were inoculated withRenibacterium salmoninarum, the causative agent of BKD. Mortality due to BKD began 26 d after inoculation, and had reached a level of 68% when the experiment was terminated on day 113. Survival was greater (P= 0.08) and time to death (in days) was longer (P< 0.05) among juvenile coho salmon from the Kitimat River strain than among those from the Robertson Creek strain. The estimated sire component of survival heritability, based on binomial data, was 0.53 ± 0.16 (mean ± SE), which became 0.90 ± 0.26 when survival was considered to be a threshold trait. The sire component estimate of heritability of time to death was 0.26 ± 0.10. There was no consistent genetic correlation between fish weight and survival time after inoculation. The results indicated that increased BKD resistance could be achieved in domesticated coho salmon brood stocks both by judicious choice of the wild progenitor strain and by subsequent selective breeding.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1990)119<1003:GVIRTB>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Densities of dominant macroinvertebrates declined in profundal and pelagic regions but not in littoral regions of Lake Lenore, Washington, after introduction of cutthroat troutOncorhynchus clarki,Chaoborus flavicans,Hyalella azteca, andCallibaetissp. composed over 90% of cutthroat trout diets, and these prey taxa showed the greatest response to the introduction. Although cutthroat trout selectively consumed larger individuals of these taxa and reduced mean length of prey in autumn populations, no change in size distribution of overwintering individuals was apparent 6 years after the fish were introduced. Reported changes in spatial distribution of these prey support the hypothesis that prey refuge space in littoral regions buffers prey populations from the direct effects of cutthroat trout predators.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1990)119<1010:CIAADO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Little is known about behavior patterns and habitat use of large (400+ mm total length) brown troutSalmo trutta. We used radio telemetry to monitor the movements of eight large (437–635 mm), free-ranging brown trout for up to 346 d. Total range of movement upstream and downstream varied from 370 m to 33,420 m. At some time during the year, six of the fish moved out of an area protected with no-kill fishing regulations, even though none of them were tagged and released closer than 2 km from its boundaries. However, four of five fish tracked during the height of the fishing season spent 87% of their time in the protected area. The fish appeared to have separate winter and summer ranges. Five of six fish tracked during autumn–winter moved upstream about 10 km to slower, deeper parts of the river between August and November, and remained there at least through the following April. The part of the river used as autumn–winter range was considered only marginal habitat for brown trout during summer due to warm water temperatures. Individuals used as many as four specific home sites within their spring–summer range; average separation between home sites was 386 m. The fish typically rotated among sites, spending 2–3 d at one site before moving, usually at night, to another section of river. Activity was divided into two categories: active displacement – long-range travel from one part of the range to another; and foraging – short-range movements that might occur when searching for food. Active displacement appeared to be correlated with stream discharge, Fish displaced themselves an average of 239 m between telemetry observations in spring–summer and 3,103 m in autumn–winter; only 11% of this variation was attributable to variations in the length of time between telemetry observations in spring–summer and autumn–winter. Daily foraging activity varied by month and appeared to be related to light level, food availability, and water temperature, In spring–summer, fish typically moved to midstream to forage at night, then returned to cover at specific home sites during the day. The sites they selected in daytime were characterized by deep (>30 cm), slow (< 10 cm/s) water with heavy log cover and silt substrate.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1990)119<1022:RAAHOL>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor