摘要:

The razorback suckerXyrauchen texanusis an endangered catostomid endemic to the mainstream Colorado River, which originally supported a limited number of piscivorous fishes. Recent attempts to recover razorback suckers by reintroducing them into their native range have not been successful, likely due to predation on the naive young suckers by nonnative fishes. We tested razorback sucker larvae singly and in groups to determine their ability to recognize and avoid predators. We related their performance to that of northern hog suckerHypentelium nigricans, a species that evolved in a predator-rich fish community. All larvae of both species recognized a predator attack when they were close to the predator and avoided the attack by fleeing or hiding. Single sucker larvae of both species improved their rate of avoidance with age, but northern hog suckers had a significantly higher initial avoidance rate than did razorback suckers. Groups of larval suckers of both species did not improve predator avoidance with age as rapidly as did single larvae. These results suggest an inherent difference in predator avoidance between species from predator-rich and predator-poor communities rather than a differential improvement with age. Recovery of razorback suckers by reintroducing them into historic riverine habitats will be limited by the presence of nonnative fishes.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<1139:NPRAAB>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

We evaluated stress due to net confinement among three genetically isolated strains of juvenile lake troutSalvelinus namaycushin relation to water hardness. Changes in plasma cortisol, glucose, sodium, and chloride were used as the stress indicators. In lake trout acclimated and then confined for 8 h in hard water, plasma glucose and cortisol increased significantly (by three- and sixfold, respectively), reaching a plateau by 4 h, while plasma Na+and Cl–significantly decreased by about 7%. Fish transferred from hard water to soft water and then confined exhibited significantly greater changes in blood chemistry than did fish confined in hard water. This soft-water effect on the stress response disappeared if fish were first acclimated to soft water, but full soft-water acclimation may take at least 2 months. Comparisons of blood chemistry among three different strains of lake trout (Lake Manitou, Killala Lake, and Slate Island) revealed significant differences in their responses to confinement stress. These findings have important implications for two fish culture issues: The choice of whether to rear stocks in soft-water versus hard-water hatcheries, and the selection of stocks for stress resistance.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<1146:PROLTT>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

During the final 10 d of a 22-d subchronic exposure of bluegillsLepomis macrochirusto a pentachlorophenol (PCP) concentration of 173 μg/L, bluegill growth rate significantly decreased by 75% when compared with untreated controls, and food intake declined significantly (29%). At a PCP concentration of 48 μg/L, growth rate was significantly reduced by 26%, but food intake showed a nonsignificant decline. Pentachlorophenol-induced decreases in food intake make this species especially vulnerable to the growth-perturbing effects of the toxicant.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<1156:PARFIO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Percent mortality of lake troutSalvelinus namaycushsubjected to single sea lampreyPetromyzon marinusattacks did not differ significantly between lower-temperature (mortality = 54%; temperature ≤ 10°C;N= 33) and higher-temperature (mortality = 69%; temperature = 12.8–14.4°C;N= 45) laboratory studies conducted from 1 June to 28 November 1989. However, sea lampreys fed longer and killed fewer fish in colder water (mean attachment 467.0 h; 18 fish killed) than in warmer water (mean attachment 161.7 h; 31 fish killed), probably because food consumption was lower in colder water. These results indicate that the number of fish killed by sea lampreys could be much greater in warmer water and that temperature must be considered when fish losses from sea lamprey attacks are estimated.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<1161:EOWTOS>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:0002-8487    

DOI:10.1577/1548-8659-122.6.1167

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor