| 1. |
- Bergenius, Mikaela, et al.
(författare)
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Fishing or the environment - what regulates recruitment of an exploited marginal vendace (Coregonus albula (L.)) population?
- 2013
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Ingår i: Advances in Limnology. - 1612-166X. ; 64, s. 57-70
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Konferensbidrag (refereegranskat)abstract
- Fish populations inhabiting marginal areas are generally highly susceptible to environmental variation and therefore show large fluctuations in recruitment. The commercially important, and usually freshwater, vendace (Coregonus albula (L.)) occupying the brackish waters of the Bothnian Bay forms one such marginal population and shows large annual variation in recruitment. Here, we investigate the relative importance of fishing (trawling time), hydro-climatic factors and species interactions in explaining the variability in vendace recruitment using three sets of models. A comparison of the best models in the hydro-climatic model set and the fishing model revealed that the hydro-climatic variables were overall superior to the anthropogenic model in describing recruitment variability. Trawling time and water temperature in winter combined with salinity explained 33 and 63.7% of the variation in recruitment, respectively. The importance of water temperature and salinity, in combination with the effects of trawling time, calls for catch levels to be set with caution in this vendace fishery.
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| 2. |
- 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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| 3. |
- Weyhenmeyer, Gesa A.
(författare)
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Resuspension in lakes and its ecological impact : a review
- 1998
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Ingår i: Advances in Limnology. - : E. Schweizerbart'sche Verlagsbuchhandlung. - 1612-166X. - 3510470532 ; 51, s. 185-200
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Forskningsöversikt (refereegranskat)abstract
- To determine geochemical, toxicological and biological impacts of sediment resuspension on lake ecosystems, this review tackles the questions where, why, when, how much, how often and what kind of sediment is resuspended and how resuspended material is distributed in the water column. Due to internal seiche activities sediment resuspension may occur in very deep areas. In the moderately deep Lake Erken in south-eastern Sweden (mean depth: 9 m, maximum depth: 21 m) internal seiche activities are, for example, one of the explanations why, as an annual average, 85 % of the total serving material in the water column was determined to be resuspended sediment. The annual averages of resuspended sediment in 16 other shallow and deep lakes spread throughout the world were 15 - 92 %. Also large amounts of organic sediment are resuspended (annual averages: 25 - 84 % of total organic settling material was resuspended organic sediment in 9 lakes). These large amounts of resuspended sediment, especially of organic resuspended sediment, have such an important influence on lake ecosystems that the nux of newly produced planktonic particulate matter was observed to be significantly related to the flux of resuspended sediment. It is suggested that the flux of resuspended sediment is not only related to planktonic production and thereby eutrophication but also to the degree of water pollution by contaminants.
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