Population structure, recruitment, mortality, life expectancy, age at maturity, gonad development, fecundity, net reproductive rate and energy storage were studied in a perch population exposed to thermal discharge. The experiment was conducted during 1978-1990 in an artificial enclosure at a nuclear power plant on the Baltic Sea coast. Abundance increased after the plant started operating, although the proportion of larger perch dropped to a low level. Recruitment improved, but adult mortality increased. This effect was accentuated as the fishes matured very early and at a very small size, reducing their ability to support a growing gonad in high winter temperatures. During the spawning period, condition dropped to very low levels accompanied by increased mortality. Surviving fish delayed the next spawning by one or more years and reduced their fecundity. Body condition thus improved in large perch at the end of the study period. Life-time fecundity was reduced, and reproductive performance shifted to younger ages. 1995 The Fisheries Society of the British Isles
Growth and reproductive capacity in perch (Percafluviatilia L.) and roach (Rutilusrutilus (L.)) were studied during 1983, 1984 and 1985 in a coastal area of the Bothnian Sea affected by bleached pulp mill effluents. Comparative investigations were made at a mill producing unbleached pulp. In perch exposed to bleachery effluents effects were observed on length increase rates, somatic condition factors and on gonad development. The fraction of fishes displaying inhibited gonadal recrudescence was high close to the mill, and the size of developing gonads was comparatively small. Growth was faster in exposed fishes, in young-of-the-year as well as in older fish. Effects on length growth could be distinguished as far back as in 1975. Energy storage, expressed as the condition factor, was highest in exposed fishes. The effect pattern was more diffuse in roach, but examples of reduced gonad growth were noted. In conclusion, these studies provided evidence for changes in the energy allocation system in fish exposed to a bleached pulp mill effluent.
The maturation pattern in the female European eel Anguilla anguilla was studied by investigating age and size patterns of silver eels in different aquatic environments in Sweden, covering limnic, brackish and marine waters. The results neither supported the hypothesis that there is a critical size or age when eels enter the silvery stage, nor that size and age at maturity are positively related. Age at maturity, however, was observed to be negatively related to growth rate in all localities, i.e. the female reproductive tactic apparently is to become sexually mature at the earliest possible opportunity. Furthermore, it was recognized that a significant amount of variation was due to habitat differences, since the female eel maturation pattern deviated systematically between sampling sites, as it did also when the effect of growth rate was eliminated. Thus, the ability of the female eel to adjust maturation to an optimal size and age can be questioned, because the panmictic nature of the eel means local adaptations are unlikely. Growth rate dependent differences suggest that variations in maturation patterns between eel environments are linked more to the opportunity for nutrient accumulation than to other aspects of growth. 1996 The Fisheries Society of the British Isles
Variations in the year-class strength of perch (Perca fluviatilis) were analyzed among 23 populations in Baltic coastal areas distributed between 57 and 66°N using the age distribution in catches. In spite of large differences in abiotic and biotic factors, the variations in year-class strength were similar in 14 of these areas. The similarities could be attributed to large-scale weather variations influencing water temperature. Year-class strength was shown to be correlated with an index based on temperature and day length during the whole first year of life. In two of the nine deviating populations, perch nursery areas are situated in small nearshore freshwaters, where fluctuations in the water level may be more important for recruitment than temperature variations. The other deviating areas were exposed to environmental disturbances, i.e. acidification, oxygen deficits, pulp mill effluents, and thermal discharge, which obviously affected recruitment in a decisive way.
The dynamics of a Baltic perch (Perca fluviatilis) population were studied in a bleached pulp mill effluent area on the Swedish coast. Recruitment was seriously affected, as larval and fry abundances were very low. Studies of spawning on artificial substrates demonstrated that sufficient numbers of eggs were deposited even in the most effluent-exposed parts of the study area. No increased egg mortality could be noted, but at the stage close to hatching about 10% of the embryos were observed to be malformed, generally having sharp bends in the posterior part of the spinal cord. Exposed embryos were generally smaller than reference fishes, both when length and weight data were compared. Larval samplings provided evidence for high mortality at or very close to hatching. Food and feeding conditions appeared to be of little importance for mortality. Two mortality causes were suggested: chronic failure of parental reproductive systems and/or acute toxicity to embryo or early larvae.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.