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Baltic herring (Clupea harengus membras) spawning grounds on the Lithuanian coast: current status and shaping factors

Šaškov A., Šiaulys A., Bučas M., Daunys D.

Oceanologia

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2014

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No. 56 (4)

789--804

EN

During the 2009 and 2010 seasons Baltic herring (Clupea harengus membras L.) spawning grounds were investigated by SCUBA divers off the Lithuanian Baltic Sea coast. The most important spawning substrate was a hard bottom overgrown with red algae Furcellaria lumbricalis, but only 32.8% of potentially suitable spawning locations had herring eggs. Bottom geomorphological analysis using multibeam bathymetry revealed that the distribution of spawning beds is not random, but is determined rather by small-scale geomorphological features. The majority of the detected spawning locations were on local elevations characterised by 2.4±1.1 m depth differences and 4.8±1.8 slopes.

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Mapping an ecosystem service: A quantitative approach to derive fish feeding ground maps

Šiaulys A., Daunys D., Bučas M., Bacevičius E.

Oceanologia

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2012

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No. 54 (3)

491-505

EN

This study presents a quantitative approach to mapping benthophagous fish feeding grounds. This approach combines the spatial biomass distribution of benthic prey items and their importance for the diets of predators. A point based biomass data of macrozoobenthos together with a set of environmental factors was used to develop Random Forests models that produce continuous biomass distribution layers for individual prey species. Depending on the diet composition and the importance of prey for fish feeding, these layers are overlaid and an integrated GIS map of the seabed showing the quality of feeding grounds is generated. These maps provide a useful basis for conservation and marine spatial planning. In addition, this method could be applied to the mapping of resources used by other benthophagous organisms. The method is presented using the example of three common Baltic fish species: cod, flounder and viviparous eelpout.

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Recent distribution and stock assessment of the red alga Furcellaria lumbricalis on an exposed Baltic Sea coast: combined use of field survey and modelling methods

Bučas M., Daunys D., Olenin S.

Oceanologia

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2009

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No. 51 (3)

341-359

EN

Recent results of field studies on the exposed coast of Lithuania were used to model the area occupied by the red alga Furcellaria lumbricalis using the Natural Neighbor interpolation technique, while linear regression was applied to estimate the species' standing stock. The area covered by F. lumbricalis extended for 26 km along the coast between depths of 1 and 15 m. The maximum species cover in the study area ranged between 4 and 10 m depth, which is one of the widest in the Baltic Sea. The modelled area of F. lumbricalis covered 35 š 11 km2 with a total biomass of 7554 š 3813 t.

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Modelling the material uptake and deposition of the mytilus edulis in the Baltic coastal ecosystem

Zemlys P., Daunys D., Razinkovas A.

Oceanological and Hydrobiological Studies

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2003

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Vol. 32, No. 2

53-79

EN

A model was developed to describe the material uptake and biodeposition of bivalve Mytilus edulis. The existing blue mussel organism level models are based on contradictory assumptions and no agreement has still been found regarding the processes and environmental factors to be included into the model. A reconciliation of contradictory approaches was successfully done in the present model. Using seston concentration, seston organic content and mussel size as input data, the model is able to predict the uptake of suspended material, selection of organic particles and material allocation as pseudofaeces, ingested, assimilated fractions and faeces. The results of the model application to mussels in the south-eastern Baltic conditions are discussed.