| 1. |
- Larsson, Stefan, et al.
(författare)
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Characteristics of anadromous whitefish (Coregonus lavaretus (L.)) rivers in the Gulf of Bothnia
- 2013
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Ingår i: BIOLOGY AND MANAGEMENT OF COREGONID FISHES - 2011. - 9783510470662 ; 64, s. 189-201
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Konferensbidrag (refereegranskat)abstract
- In order to study anadromous whitefish spawning river requirements, we sampled 41 rivers in the Gulf of Bothnia for newly hatched whitefish larvae for one to three consecutive years. Chemical and morphological data (e.g. flow rate, topography, pH, estuary fetch and distance to coastal sandy areas) were collected for each river. Newly-hatched whitefish were caught in 19 rivers whereas whitefish were not confirmed present in 22 rivers. By applying partial least squares discriminant analysis (PLS-DA), data for rivers confirmed to support whitefish were contrasted with data for rivers in which whitefish were not found. The single most important factor was annual average water flow rate. Whitefish larvae were observed in 93% of the rivers with annual mean flow rate > 5 m(3) s(-1) (N = 14). In contrast, newly-hatched whitefish were only found in 22% of the smaller rivers (N = 27).
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| 2. |
- Gunnarsson, Gunnar, et al.
(författare)
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Food limits survival of breeding boreal mallards Anas platyrhynchos
- 2003
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- During the breeding period dabbling ducks (Anas sp.), and especially newly hatched ducklings, face heavy mortality. The reasons are not clear, but suggested factors contributing are scarce food, predation, chilling and disease. We highlighted the question why many of the boreal lakes in Scandinavia are without breeding ducks and why mortality is considerable during brood period. In an experimental study in 2002 we hypothesized food being a major factor deciding duck survival during breeding. One wing-clipped hen mallard with her own newly hatched brood (10 ducklings) was introduced onto each of 10 lakes. Food was added ad libitum at 5 of these lakes (experimental lakes), whereas the other five lakes (controls) did not get any extra food added. Survival of hens, broods as well as each individual duckling was monitored regularly until 24 days after introduction. At all three levels (i.e. duckling, brood and adult), survival was significantly higher on lakes with food added than on control lakes, although the difference was most pronounced on the duckling level. Direct consequences (i.e. dying from starvation) as well as indirect (e.g. undernourished individuals being more easily taken by predators) may both explain this pattern. Our results clearly show that food is a major limiting factor on mallard survival in this environment. Also, our results may explain why many boreal lakes in Scandinavia do not have any breeding waterfowl at all. It seems likely that such lakes are too poor to raise broods and even to sustain adults.
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| 3. |
- Sjöberg, Kjell, et al.
(författare)
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Density dependent survival of mallard ducklings in boreal lakes : a field experiment
- 2003
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- From earlier field studies and experiments we have found that the nutrient status of lakes in the boreal region of northern Europe might influence the production of ducklings among dabbling ducks. For ducks, this might be important in the choice of breeding strategy. In this study we created a 2-year cross-over field experiment in northern Sweden where mallard hens and broods (10 ducklings) were introduced on 10 oligotrophic lakes (i.e. poor lakes) in two different densities; 4 hens with broods (high density) on 5 lakes and 1 hen with brood (low density) on the remaining 5 lakes. The adult ducks were wild birds, caught and brought to a game farm where they hatched their eggs. Within a few days after hatching they were released on the lakes in the beginning of June when wild mallards have their hatching peak. After introductions the survival of broods, ducklings and hens were monitored daily the first 12 days and then every third day until day 24. The second year there was a switch of treatments in the lakes. The results after one year indicate that the survival rates of broods, ducklings and hens are density dependent. In lakes with high densities of introduced mallards the survival rates was higher compared to low density lakes.
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| 4. |
- Larsson, Kjell, et al.
(författare)
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Continuing growth of the Baltic barnacle goose population : Number of individuals and reproductive success in different colonies
- 1997
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Ingår i: Research on arctic geese. - : Norsk Polarinstitutt. - 8276661548 ; , s. 213-219
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Konferensbidrag (refereegranskat)abstract
- The Baltic barnacle goose population increased rapidly after 1971, when the first breeding attempt was observed off the eastern coast of Gotland, Sweden. In 1997, about 3,990 pairs bred along the Baltic coast in Sweden, western Estonia and southern Finland. The majority of these pairs, about 3,490 pairs, were found breeding in colonies along the eastern coasts of Gotland and Oland, Sweden. The total population size at the end of July in 1997 was estimated to be approximately 17,000 individuals. The production of fledged young per breeding pair was negatively related to the size of colonies, although the production varied greatly among different colonies. In 1997, the largest Baltic colony hosted more than 50% of the total number of breeding pairs but produced less than 15% of the total number of fledged young. This finding points out the need to consider different colonies as separate demographic units when studying regulation processes in populations of colonially breeding geese. In the future, we find it most probable that the Baltic population will continue to increase and that new colonies will be established. We also expect that the number of Baltic barnacle geese eventually will be limited by the availability of predator-safe grazing grounds with short, protein rich grass which families with newly hatched goslings are dependent on.
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| 5. |
- Blom, Eva-Lotta, et al.
(författare)
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Continuous and intermittent noise has a negative impact on reproductive success and early life survival in marine fish
- 2022
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Konferensbidrag (refereegranskat)abstract
- Anthropogenic underwater noise is a global pollutant of increasing concern and its effect on marine organisms is largely unknown. Importantly, direct assessments of fitness consequences are lacking especially in fish. The effect of noise pattern with continuous or intermittent noise are poorly understood and the few existing studies investigating the effect highlight contradictory responses in fish. Working in aquaria, we experimentally tested the impact of broadband noise exposure (similar frequency range as anthropogenic boat noise; added either continuously or intermittently) on the behaviour and reproductive success, assessed by the number of obtained eggs, of the common goby (Pomatoschistus microps), a vocal fish with exclusive paternal care. The continuous noise treatment had the most detrimental effect by reducing spawning probability and females took longer to spawn under continuous noise. Males exposed to continuous noise got significantly fewer egg clutches (4 compared to 11 and 15 in the intermittent noise and silence treatments). Clutch area did not differ among treatments but clutches in the intermittent and continuous noise treatment had significantly more eggs per cm2. In addition, eggs in the control tanks hatched earlier than in the intermittent and noisy treatments. Larvae reared in continuous noise treatment were larger and had a smaller yolk-sac at hatching than larvae in the intermittent noise treatment and the control. Taken together, we show that noise, particularly a continuous noise exposure, negatively affects reproductive success and early life survival in fish larvae.
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| 6. |
- Martyshyn, A., et al.
(författare)
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Taphonomy of tubular fossils (algae) from the deposits of the Late Ediacaria of Ukraine
- 2022
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Ingår i: 11<sup>th</sup> European Palaeobotany and Palynology Conference Abstracts, Program and Proceedings. - Stockholm, Sweden : Swedish Museum of Natural History. - 9789152734339 ; , s. 224-225
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Konferensbidrag (refereegranskat)abstract
- The collection of Ediacaran algal flora is stored in the Institute of Geological Sciences of the National Academy of Sciences of Ukraine. These fossils were collected by Andrii Martyshyn in southwestern Ukraine. Within the framework of the priority topic “Integration of large-scale geological data to solve fundamental and applied problems of Ukraine”, which is being carried out at the Institute, the collection was revised. New fossil specimens of giant tubularstructures were also added, which we recently discovered in sediments (argillites, siltstones, sandstones) of the Mohyliv-Podilska series of the Ediacaran (Dniester river valley, southwestern Ukraine). The material is represented by three taphonomic variants of these remains: three-dimensionally preserved rods, phytoleimes and rods with charred shell fragments. We have collected a large number of fossils of soft-bodied organisms, trace fossils, macroalgae and problematic remains. Analysis of our findings suggests that some known and new fossils are likely to be the remains of algae. This interpretation is based on findings that demonstrate the different taphonomic states of preservation. The material of the new species of the previously described genus Harlaniella Sokolov in argillitic strata of the Kanylivka Group was described as traces of movement of worm-like creatures. These fossils look like straight or curved rods with oblique hatching on the lower surface of the rock. There are no trace fossils with similar morphology in the fossil record of the Phanerozoic. Our new material shows that the fossils were organic tubes with a smooth surface and an obliquely transverse sculpture on the inner surface of the wall. We found specimens with examples of the transition from smooth tubes into hatched rods and carbonaceous compression fossils (phytoleims). Similar phytoleims are widespread in this stratum and are described as remnants of probable brown algae Vendotaenia Gnilovskaja. New finds demonstrate a morphology different from the holotype: numerous branching segments and elasticity of deformed tubes. We did not detect holdfasts attaching bodies to the substrate, indicating a probable planktonic habit for these putative algae.
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