Marjut Rajasilta

Marjut Rajasilta
University of Turku | UTU · Department of Biology

About

55
Publications
5,239
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1,364
Citations

Publications

Publications (55)
Article
Full-text available
We report observations of vateritic crystallization in the sagittal otoliths of the Baltic herring Clupea harengus membras in the northern Baltic Sea. While the existence of vaterite in the calcium carbonate matrix of sagittal otoliths has been observed in various species globally, reports from the brackish Baltic Sea are few in number. Large varia...
Experiment Findings
Full-text available
In this study, the fat content and fatty acid composition of the Baltic herring muscle and eggs were investigated in the Archipelago Sea during 2020-2021. Fish samples were collected from the trawl catches in winter and from the trap net catches of spawning herring in two different areas. All fish were analysed on individual basis to find out the s...
Article
Full-text available
In fish, the lipid resources of the female form a link between the environment and progeny, contributing to the contents of the egg yolk. Variation of the environmental conditions is therefore expected to affect the egg quality via maternal pathways, reflecting the female’s response to the environmental factors before spawning. We investigated the...
Article
Full-text available
The blue mussel (Mytilus trossulus × edulis) is one of the most abundant benthic animals in the Archipelago Sea in the northern Baltic. The mussel is considered a key species, because it participates in the biomass and nutrient cycles by filtering water, serves as a growth platform and is a food source for many organisms. The mussel exhibits a gen...
Article
Full-text available
From 1970 to 2000, the yearly Baltic Sea River Runoff (BSRR) together with the silicate concentrations in the Baltic (BS) and North Sea (NS) were observed. We found that the concentrations of silicates were consistently higher in the BS. Furthermore, long-term changes in both ecosystems indicated an overall decrease of Si with increased BSRR. Silic...
Article
Full-text available
Uusin tutkimuksemme tuo vahvistusta näkemykselle, että Itämereltä Pohjanmereen purkautuvalla murtovedellä on aiemmin tiedettyä voimakkaampi vaikutus paitsi Pohjanmeren suolapitoisuuteen ja kasvi- ja eläinplanktonin määrään, myös silikaattiravinteen saatavuuteen Pohjanmeren ulappaekosysteemissä. Turun Sanomat: https://www.ts.fi/puheenvuorot/5144270...
Preprint
Full-text available
In the Baltic Sea (BS), the silicate concentrations in seawater are generally higher than in the North Sea (NS), and therefore BS outflows act as a silicate supply for the NS pelagic ecosystem. · The ground silicate concentrations are lower in the northern BS than in the south, where large sandy coastal areas predominate. · Since 1980s, a general i...
Article
Full-text available
Global climate change can affect the energy content of fish by altering their lipid physiology and lipid consumption. We investigated the effects of different environmental stressors on the lipid content of the Baltic herring (Clupea harengus membras) from spawning ground samples that were collected annually in the northern Baltic Sea. During 1987-...
Article
Full-text available
Silakkaa on tutkittu Saaristomerellä jo yli 30 vuoden ajan. Airiston silakka ilmentää muutoksia ympäristön ja kalakannan tilassa. Suomen Kalastuslehti 2/2019: 31-32.
Article
Full-text available
Vid Skärgårdshavets forskninginstitut har man i över 30 år följt upp strömmingen på Erstan. Strömmingproven återspeglar både förändringar i miljön och fiskbeståndet. Fiskeritidskrift för Finland 1/2019: 30-32.
Data
Fig. 1 A) Lipid content (% wt.w) of spawning female herring during 1987-2013 & 2013-2014 (black solid line) together with linear trend line (black arrow) and min and max values (black dashed line). B) Lipid content and mesentric fat (% w.wt.) of overwintering herring in outer archipelago in 1988 and 2017. ND= No Data.
Poster
Full-text available
Change of climate is expected to influence the energy content of fish by affecting the environmental conditions where lipids are produced, transferred, accumulated and consumed. We examined the lipid content of the Baltic herring (Clupea harengus membras) spawning in the Archipelago Sea during a period of declining salinity, high variability in te...
Article
Full-text available
The lipid reserves and occurrence of the cold-stenothermic, omnivorous copepod Limnocalanus macrurus were studied in the Bothnian Sea (northern Baltic Sea) during spring and summer 2013-2014 with a special emphasis on the fatty acid composition of adults and their potential food. The individual total wax ester (WE) content, determined from the size...
Poster
Full-text available
Reproductive disorders are a major environmental concern in the Baltic Sea, due to heavy anthropogenic influence and long- and short-term variations taking place in the natural environment. We report here an increasing prevalence of gonadal malformations in the Baltic herring (Clupea harengus membras),a key species of the Baltic ecosystem and impor...
Poster
Full-text available
Limnocalanus macrurus is a cold-stenothermic copepod that in the Baltic Sea occurs abundantly in low-salinity areas, such as the Bothnian Bay and the Bothnian Sea, where it is one of the most important species of the pelagic ecosystem. Projections for the future of the Baltic Sea suggest that a further decline of salinity will enable the species to...
Article
Full-text available
Due to heavy anthropogenic influence and variation of the environmental conditions in the Baltic Sea, reproductive disorders are becoming a major environmental concern. We show here an increasing prevalence of gonadal malformations in the Baltic herring (Clupea harengus membras), a key species of the Baltic ecosystem and important in commercial fis...
Article
Full-text available
Selected Baltic Sea watershed River Runoff (BSRR) events during 1970–2000 were used as predictor in Generalised Linear Mixed Models (GLIMMIX) for evidence of simultaneous changes/chain of events (including possible time lags) in some chemical, physical and biological variables in the Baltic and North Sea ecosystems. Our aim was to explore for clima...
Article
Full-text available
The authors regret a misprint in the citation year of Telesh I.V., Schubert H., Skarlato S.O. Publication year is 2011, not 2010. The correct citation is: Telesh I.V., Schubert H., Skarlato S.O., 2011. Revisiting Remane’s concept: evidence for high plankton diversity and a protistan species maximum in the horohalinicum of the Baltic Sea. Mar. Ecol...
Article
Full-text available
Substantial ecological changes occurred in the 1970s in the Northern Baltic during a temporary period of low salinity (S). This period was preceded by an episodic increase in the rainfall over the Baltic Sea watershed area. Several climate models, both global and regional, project an increase in the runoff of the Northern latitudes due to proceedin...
Article
Full-text available
The trade-off between somatic growth and reproduction in the female Baltic herring Clupea harengus was investigated from 1984 to 2002. During the study period, growth decreased, as a consequence of decreasing salinity and weakening of feeding conditions. Production of muscle and ovarian tissue decreased in repeat spawners, but investment in reprodu...
Article
Full-text available
The stomach contents of the herring (Clupea harengus membras L.) from the Bothnian Sea, northern Baltic, were analysed during spring 2011 and 2013. The stomachs were full of Limnocalanus macrurus in May and June, and an improvement in the condition of herring was observed when fish started to feed on this prey. The analyses showed that Limnocalanus...
Article
The effect of nutritional status on gonad maturation and timing of spawning was examined in the Baltic herring (Clupea harengus membras) in the Archipelago Sea. Fish were collected from overwintering areas in December and from the spawning grounds in May–July. Muscle fat content, amount of mesenteric fat, and condition factor were used as indicator...
Article
We studied the effect of salinity on growth, fat reserves and condition of the Baltic herring (Clupea harengus membras) juveniles in order to determine their optimum salinity. About 5months old fish were reared in four salinities (5.7, 8, 12 and 15psu) over a period of 1.5months in constant temperature (+6°C) and photoperiod (light:dark=12h:12h). U...
Article
In the Baltic Sea, herring (Clupea harengus membras) spawns in the littoral zone, where its eggs are attached to algae or vascular plants. Field studies indicate that egg mortality can be very high (up to 100%) in eggs that are attached to red algae (Rajasilta etal., 1989, 1993). Because high mortality can be due to allelochemical effects of the al...
Article
The gonad weight and gonadosomatic index of the male Baltic herring Clupea harengus membras L., were highest at the beginning of the reproductive season (April/May), the values decreasing towards the end of it (July/August) during 1988–1991. The decline could not be explained by fish size but may have been due to fish condition. A high individual v...
Article
Full-text available
Trends with spawning time in the ovarian weight of the Baltic herring (Clupea harengus membras) were studied from samples collected over the spawning season in 1988-1991, 1997 and 1998 in the Archipelago Sea, northern Baltic. Usually, ovarian weight was related to the size composition of the spawning shoals but there was also variation unrelated wi...
Article
The fertilisation success and mortality of Baltic herring (Clupea harengus membras L.) eggs were investigated experimentally during 1993–1997. Differences among years and among females were studied, and also the correlative relationships between females' size, condition and egg properties were analysed. Fish for the experiments were sampled near th...
Article
A collapse of the littoral fish populations was found in the middle archipelago zone near the Island of Seili (northern Baltic Sea) when fish populations were studied in summer 1996 in a comparable way with earlier studies done in the early 1970s and 1980s. A similar comparison was made in the outer archipelago (the islands off the island of Utö),...
Article
The reproductive properties of Baltic herring (Clupea harengus membras L.) females and their seasonal change were studied in the Archipelago Sea in Southwest Finland during 1988 and 1991. Fecundity, relative fecundity, fecundity index, gonadosomatic index (GSI), and egg fresh weight were used to describe females' reproductive effort. Ripe females f...
Article
The spawning bed characteristics of the Baltic herring (Clupea harengus membras L.) were investigated during the spawning season in the Airisto Inlet (Northern Baltic Sea) in SW Finland. Within the area, 46 transects were investigated by scuba diver; 37 transects were randomly selected and 9 were known to be spawning beds. Data on the substratum an...
Article
Full-text available
Spawning of herring (Clupea harengus membras) was investigated in the Archipelago Sea, south-west Finland, in 1987–1989 using SCUBA diving, trap-net sampling, and catch statistics. Herring spawned repeatedly on the same beds. Spawning was rather continuous from April to July when the whole spawning area was considered and took place in temperatures...
Article
Aqua Fennica, ISSN 0356-7133, vol. 23, nr. 2, 187-191 This paper presents results of benthic studies in the middle and outer parts of the archipelago. Even though there were some differences in benthic communities, there was no clear zonation between the three study areas. In Seili area, the changes in Macoma and Pontoporeia populations in 1969-92...
Article
Lateral migration of Amazonian lowland rivers causes a vegetation succession on recently deposited fluvial sediments. The forest ground is formed gradually in sequence, giving rise to age-zonation of the successional stages. Sequential successional forests appear extensively along meandering white-water rivers, which are rich in suspended sediments...
Article
1.1. The food of vendace in Lake Pyhäjärvi (SW Finland) consisted mainly of cladocerans and copepods throughout the sampling period from May to October.2.2. The content of triacylglycerols and polar lipids of vendace flesh, varied seasonally, in accordance with the total lipids. Triacylglycerols dominated in vendace flesh, while these and polar lip...
Article
The larval period began in May; it was not constant, however, from year to year but varied with regard to start, duration and timing of hatching of cohorts. Three to four successive cohorts of different strengths were produced each year. The feeding conditions of the newly-hatched larvae varied according to season, with zooplankton species composit...
Article
The spawning shoal structure and intensity of spawning Clupea harengus membras were studied in the Archipelago Sea. After a mild winter, 1) spawning started earlier; 2) its intensity shifted towards the earlier part of the reproductive period, ie more fish spawned earlier than normally; and 3) the spawning stock was sorted by size, the large fish s...
Article
Newly deposited fluvial sediments are poor in organic C and N. Colonization begins either with immigrant propagules dispersed by wind or water, or with invasion of species by vegetative means. Usually numbers of individuals are few, and the initial vegetation pattern is a reflection of the small-scale mosaic of microsites. The pioneer flora (125 sp...
Article
Abstract We studied the diel distribution of cladoceran zooplankton in a shallow bay of Lake Pyhäjärvi, SW Finland. Zooplankton samples were collected during one day and night from 24 locations distributed along three horizontal zones 0.5, 2.5, and 5.0 m from the shoreline. The total number of species was significantly higher in the night samples,...
Article
1 We studied the recent history (1852-1982) of Lake Pyhä-järvi, south-west Finland, using both cladoceran microfossils and independent historical data. The objective of the study was to assess the impact of introduced planktivorous whitefish Coregonus lavaretus s.1. on zooplankton, especially on the main prey species Bosmina coregoni Baird s.str. 2...
Article
The environmental factors affecting the deposition and mortality of the eggs of the spring-spawning Baltic herring were studied in the inner Archipelago Sea of south-western Finland. On four spawning grounds, 27 study squares (area 1 m2) were surveyed by divers. In each square, one quantitative egg sample was taken and the following data were recor...
Article
The Baltic Sea environment : history - eutrophication - recruitment - ecotoxicology : proceedings of the 10th Symposium of the Baltic Marine Biologist, Keil, September 29 - October 3, 1987: eds. H. Theede, W. Schramm, Kieler Meeresforschungen ; Sonderheft 6, 348-356 Symposium of the Baltic Marine Biologists. 10 Kiel 1987
Article
The Baltic sea environment : history - eutrophication - recruitment - ecotoxicology : proceedings of the 10th Symposium of the Baltic Marine Biologists, Kiel, September 29 - October 3, 1987: eds. H. Theede, W. Schramm, Kieler Meeresforschungen ; Sonderheft 6, 140-146 Symposium of the Baltic Marine Biologist. 10 Kiel 1987
Article
The food selection of larval fish was studied from field samples collected in two areas that differ in productivity. In the area where planktonic primary and secondary production was high the fish larvae showed a tendency to specialise and they selected the largest prey species available as food; in the area of lower production fish were generalist...
Article
In studying the relevance of the predation hypothesis as an explanation for the vertical migration of zooplankton two predictions were tested:1) The egg sacs of Eurytemora are sufficient to cause different predation pressure in food selection experiments with visually hunting planktivores as predators and ovigerous vs. non-ovigerous Eurytemora fema...
Article
Kala- ja riistahallinnon julkaisuja Nro 31;1236-7222 Pages: 41 pp Nauvon Käldingessä tehtiin vuonna 1996 siianpoikasten kasvatuskoe, jonka tarkoituksena oli selvittää mahdollisuudet kasvattaa verkkokasseissa murtovesiolosuhteissa merkittäviä määriä vaellussiian ja merikutuisen siian yksikesäisiä istutuspoikasia lisäravintoa (poikasrehua) ja valoa a...

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Projects

Projects (3)
Project
The Institute participates in multidisciplinary research of the Baltic Sea, with a special focus on the Archipelago Sea. Additionally, we conduct long-term environmental monitoring and offer a number of research and teaching services and support to researchers, teachers, and students. Our own research chiefly comprises projects studying the biological and geological condition of the Archipelago Sea. Most of the research in Seili is done in cooperation with other research groups within and outside the University of Turku. The Saaristomeri.utu.fi website (Saaristomeri means Archipelago Sea in Finnish) is administered by the Archipelago Research Institute, University of Turku, Finland. On this website we offer online data on weather and sea water quality at the Archipelago Sea as well as live stream of an osprey nest, located on the island of Seili. The site is meant to serve everyone interested in nature and knowledge backed by research.
Project
The Baltic herring research project focuses on the reproductive biology of the Baltic herring (Clupea harengus membras) and processes and factors affecting clupeid fish in the Baltic Sea. The research started at the University of Turku in the beginning of the 1980s. Since then, the research on herring has continued in the form of several scientific and monitoring sub-projects, which have been carried out in the northern Baltic Archipelago Sea area and especially in the vicinity of the city of Turku (Finland), where some of the major reproductive areas of herring are situated. As a result, the project has accumulated and now maintains several unique long-term data sets on herring, which have been collected by sampling the spawning fish and by monitoring the spawning beds by scuba diving. During the project’s almost four-decade-long history, environmental conditions at the spawning area have changed considerably, e.g. due to eutrophication and decreasing salinity, which gives us means to study how herring reproduces and survives in the changing conditions of the Baltic Sea. Please, get introduced to Baltic herring -project at: https://sites.utu.fi/seili/en/station/research/
Archived project
This international summer school will be organized in the Archipelago Research Institute's Seili field station in September 2017.