Trout

Abstract: The occurrence of hermaphrodite fish in the lagoons of sewage treatment works led us to hypothesize that sewage effluent might contain a substance, or substances, estrogenic to fish. to test this hypothesis, we placed cages containing rainbow trout in the effluent from sewage-treatment works, and one to three weeks later measured the vitellogenin concentration in the plasma of the fish. Vitellogenin is a protein synthesized by the liver of oviparous fish in response to estradiol stimulation; it is then conveyed by the blood to the ovary, where it is sequestered by oocytes to form the yolk. Thus, the presence of vitellogenin in the plasma is indicative of estrogenic stimulation of the liver. an initial study, at a sewage-treatment works, showed that plasma vitellogenin concentrations rose rapidly and very markedly (over 1000-fold in three weeks) when trout were maintained in the effluent. an extensive nationwide survey was then conducted. Results were obtained from fifteen sewage-treatment works d...

Abstract: PrefaceAcknowledgments1. Introduction2. Homeward Migration of Adults on the Open Ocean3. Migrations in Coastal and Estuarine Waters4. Upriver Migration and Energetics5. Homing and Patterns of Straying6. Mating System and Reproductive Success7. The Ecology of Dead Salmon8. Incubation Rate and Mortality of Embryos9. Alevin Movements, Emergence, and Fry Migrations10. Sockeye Salmon and Trout in Lakes11. Juvenile Salmonids in Streams12. Downstream Migration: To Sea or Not to Sea?13. Estuarine Residence and Migration14. Marine Migration Patterns15. Survival in the Marine Environment16. Feeding and Growth at Sea17. Age and Size at Maturity18. The Evolution and Structure of Salmon Populations19. The Abundance and Diversity of Pacific Salmon: Past, Present, and FutureReferences CitedIndex

Abstract: The occurrence of certain natural and synthetic steroidal estrogens in the final effluent from STW has been demonstrated. 17β-Estradiol and estrone were present at concentrations in the tens of nanograms per liter range, and the synthetic estrogen 17α-ethynylestradiol was also identified, albeit in the low nanogram per liter range. The findings from subsequent in vivo tank trial experiments, in which adult male rainbow trout (Oncorhynchus mykiss) and adult roach (Rutilus rutilus) were exposed for 21 days via the water to environmentally relevant concentrations of 17β-estradiol and estrone are presented. In addition, the response of adult male and female roach following exposure to 17β-estradiol (1, 10, and 100 ng/L) was compared to the response to the alkylphenolic xenoestrogen, 4-tert-octylphenol (1, 10 and 100 μg/L). Plasma levels of vitellogenin were determined using previously validated radioimmunoassays in order to measure the estrogenic response of the fish to the varying concentrations of the compo...

Abstract: It is becoming evident that an increasing number of widely used industrial and agricultural chemicals are estrogenic. The biodegradation products of a major group of nonionic surfactants, the alkylphenol polyethoxylates, are one such group. Some of these chemicals are widespread aquatic pollutants, and bioconcentrate in aquatic biota. Exposure of male rainbow trout (Oncorhynchus mykiss) to four different alkylphenolic chemicals caused synthesis of vitellogenin, a process normally dependent on endogenous estrogens, and a concomitant inhibition of testicular growth. The magnitude of these estrogenic effects was dependent on the estrogenic potency of the chemical, the stage of reproductive development of the fish, and the concentration of the chemical in the water. These results support the contention that exposure of wildlife to environmentally persistent estrogenic chemicals can result in deleterious reproductive consequences.

Abstract: – Among the species in the family Salmonidae, those represented by the genera Salmo, Salvelinus, and Oncorhynchus (subfamily Salmoninae) are the most studied. Here, various aspects of phenotypic and life-history variation of Atlantic salmon Salmo salar L., brown trout Salmo trutta L., and Arctic charr Salvelinus alpinus (L.) are reviewed. While many strategies and tactics are commonly used by these species, there are also differences in their ecology and population dynamics that result in a variety of interesting and diverse topics that are challenging for future research. Atlantic salmon display considerable phenotypic plasticity and variability in life-history characters ranging from fully freshwater resident forms, where females can mature at approximately 10 cm in length, to anadromous populations characterised by 3–5 sea-winter (5SW) salmon. Even within simple 1SW populations, 20 or more spawning life-history types can be identified. Juveniles in freshwater can use both fluvial and lacustrine habitats for rearing, and while most smolts migrate to sea during the spring, fall migrations occur in some populations. At sea, some salmon undertake extensive oceanic migrations while other populations stay within the geographical confines of areas such as the Baltic Sea. At the other extreme are those that reside in estuaries and return to freshwater to spawn after spending only a few months at sea. The review of information on the diversity of life-history forms is related to conservation aspects associated with Atlantic salmon populations and current trends in abundance and survival. Brown trout is indigenous to Europe, North Africa and western Asia, but was introduced into at least 24 countries outside Europe and now has a world-wide distribution. It exploits both fresh and salt waters for feeding and spawning (brackish), and populations are often partially migratory. One part of the population leaves and feeds elsewhere, while another part stays as residents. In large, complex systems, the species is polymorphic with different size morphs in the various parts of the habitat. Brown trout feed close to the surface and near shore, but large individuals may move far offshore. The species exhibits ontogenetic niche shifts partly related to size and partly to developmental rate. They switch when the amount of surplus energy available for growth becomes small with fast growers being younger and smaller fish than slow growers. Brown trout is an opportunistic carnivore, but individuals specialise at least temporarily on particular food items; insect larvae are important for the young in streams, while littoral epibenthos in lakes and fish are most important for large trout. The sexes differ in resource use and size. Females are more inclined than males to become migratory and feed in pelagic waters. Males exploit running water, near-shore and surface waters more than females. Therefore, females feed more on zooplankton and exhibit a more uniform phenotype than males. The Arctic charr is the northernmost freshwater fish on earth, with a circumpolar distribution in the Holarctic that matches the last glaciation. Recent mtDNA studies indicate that there are five phylogeographic lineages (Atlantic, Arctic, Bering, Siberian and Acadian) that may be of Pleistocene origin. Phenotypic expression and ecology are more variable in charr than in most fish. Weights at maturation range from 3 g to 12 kg. Population differences in morphology and coloration are large and can have some genetic basis. Charr live in streams, at sea and in all habitats of oligotrophic lakes, including very deep areas. Ontogenetic habitat shifts between lacustrine habitats are common. The charr feed on all major prey types of streams, lakes and near-shore marine habitats, but has high niche flexibility in competition. Cannibalism is expressed in several cases, and can be important for developing and maintaining bimodal size distributions. Anadromy is found in the northern part of its range and involves about 40, but sometimes more days in the sea. All charr overwinter in freshwater. Partial migration is common, but the degree of anadromy varies greatly among populations. The food at sea includes zooplankton and pelagic fish, but also epibenthos. Polymorphism and sympatric morphs are much studied. As a prominent fish of glaciated lakes, charr is an important species for studying ecological speciation by the combination of field studies and experiments, particularly in the fields of morphometric heterochrony and comparative behaviour.