scholarly journals In situ target strength of the Baltic Sea herring and sprat

2004 ◽  
Vol 61 (3) ◽  
pp. 378-382 ◽  
Author(s):  
Tomas Didrikas ◽  
Sture Hansson
Keyword(s):  
Baltic Sea ◽  
Clupea Harengus ◽  
Target Strength ◽  
Fish Length ◽  
The North ◽  
Length Relationship ◽  
Stock Biomass ◽  
Acoustic Target ◽  
The North Sea ◽  
The Baltic

Abstract Using single- and split-beam hydroacoustic equipment (70 and 38 kHz), and gillnet and trawl catches, we derived the relationship TS = 25.5 log10 L − 73.6 (r2=0.95) between acoustic target strength (TS) and fish length (L, cm) for Baltic Sea herring (Clupea harengus membras L.) and sprat (Sprattus sprattus balticus (Schneider)). Fixing the slope to 20, which is a standard practice in hydroacoustics, gave TS = 20 log10 L − 67.8 (r2=0.91). Normally, the fisheries agencies around the Baltic use a TS–length relationship that is based mainly on data from the North Sea and the intercept-value in this equation is 3.4 dB lower than that reported in this paper. This difference corresponds to an approximately twofold difference in assessed stock biomass.

The acoustic target strength of herring (Clupea harengus L.) in the northern Baltic Sea

2005 ◽  
Vol 62 (4) ◽  
pp. 803-808 ◽  
Author(s):  
Heikki Peltonen ◽  
Helge Balk
Keyword(s):  
Baltic Sea ◽  
Clupea Harengus ◽  
Target Strength ◽  
Fish Length ◽  
The Baltic Sea ◽  
Length Relationship ◽  
Acoustic Target ◽  
The Baltic ◽  
Catch Composition ◽  
Bothnian Sea

Abstract The hydro-acoustic target strength (TS) of herring (Clupea harengus L.) was estimated from the catch composition of 19 pelagic-trawl hauls and from simultaneous recordings with a split-beam, 38 kHz echosounder. The data were collected in September 2000 during a Bothnian Sea survey in the northern Baltic Sea. The dependence of TS (in dB) on fish length (L, cm) was modelled with the equation TS = a log10 L + b. The fitted model was TS = 16.8 log10 L − 60.0. With a predefined slope of 20 the TS vs. log-fish length relationship was TS = 20 log10 L − 63.9. The analyses suggested that TS was higher in the Bothnian Sea than is assumed in most studies in the Baltic Sea. Applying the revised TS–length dependence considerably enhanced the agreement between the biomass estimates from hydroacoustics and those from a catche-at-age analysis (VPA).

scholarly journals The carbon budget of the Baltic Sea

2011 ◽  
Vol 8 (11) ◽  
pp. 3219-3230 ◽  
Author(s):  
K. Kuliński ◽  
J. Pempkowiak
Keyword(s):  
Organic Carbon ◽  
Baltic Sea ◽  
Carbon Budget ◽  
The Other ◽  
Minor Importance ◽  
The Baltic Sea ◽  
Sources And Sinks ◽  
The North ◽  
The North Sea ◽  
The Baltic

Abstract. This paper presents the results of a comprehensive study of the Baltic Sea carbon budget. The Baltic Sea is very much influenced by terrestrial carbon input. Rivers are the largest carbon source, and their input amounts to 10.90 Tg C yr−1 (Tg = 1012 g) with a 37.5% contribution of organic carbon. On the other hand, carbon is effectively exported from the Baltic to the North Sea (7.67 Tg C yr−1) and is also buried in bottom sediments (2.73 Tg C yr−1). The other sources and sinks of carbon are of minor importance. The net CO2 emission (1.05 Tg C yr−1) from the Baltic to the atmosphere was calculated as the closing term of the carbon budget presented here. There is a net loss of organic carbon, which indicates that the Baltic Sea is heterotrophic.

scholarly journals Model calculations of the effects of present and future emissions of air pollutants from shipping in the Baltic Sea and the North Sea

2014 ◽  
Vol 14 (15) ◽  
pp. 21943-21974 ◽  
Author(s):  
J. E. Jonson ◽  
J. P. Jalkanen ◽  
L. Johansson ◽  
M. Gauss ◽  
H. A. C. Denier van der Gon
Keyword(s):  
Baltic Sea ◽  
North Sea ◽  
Years Of Life Lost ◽  
Ship Emissions ◽  
The Baltic Sea ◽  
Model Calculations ◽  
The North ◽  
Before And After ◽  
The North Sea ◽  
The Baltic

Abstract. Land-based emissions of air pollutants in Europe have steadily decreased over the past two decades, and this decrease is expected to continue. Within the same time span emissions from shipping have increased, although recently sulphur emissions, and subsequently particle emissions, have decreased in EU ports and in the Baltic Sea and the North Sea, defined as SECAs (Sulphur Emission Control Areas). The maximum allowed sulphur content in marine fuels in EU ports is now 0.1%, as required by the European Union sulphur directive. In the SECAs the maximum fuel content of sulphur is currently 1% (the global average is about 2.4%). This will be reduced to 0.1% from 2015, following the new IMO rules (International Maritime Organisation). In order to assess the effects of ship emissions in and around the Baltic Sea and the North Sea, regional model calculations with the EMEP air pollution model have been made on a 1/4° longitude × 1/8° latitude resolution, using ship emissions in the Baltic Sea and the North Sea that are based on accurate ship positioning data. The effects on depositions and air pollution and the resulting number of years of life lost (YOLL) have been calculated by comparing model calculations with and without ship emissions in the two sea areas. The calculations have been made with emissions representative of 2009 and 2011, i.e. before and after the implementation of stricter controls on sulphur emissions from mid 2010. The calculations with present emissions show that per person, an additional 0.1–0.2 years of life lost is estimated in areas close to the major ship tracks with present emission levels. Comparisons of model calculations with emissions before and after the implementation of stricter emission control on sulphur show a general decrease in calculated particle concentration. At the same time, however, an increase in ship activity has resulted in higher emissions and subsequently air concentrations, in particular of NOx, especially in and around several major ports. Additional model calculations have been made with land based and ship emissions representative of year 2030. Following a decrease in emissions, air quality is expected to improve, and depositions to be reduced. Particles from shipping are expected to decrease as a result of emission controls in the SECAs. Further controls of NOx emissions from shipping are not decided, and calculations are presented with and without such controls.

scholarly journals Understanding resource driven female–female competition: ovary and liver size in sand gobies

2019 ◽  
Vol 6 (9) ◽  
pp. 190886 ◽  
Author(s):  
Aurora García-Berro ◽  
Johanna Yliportimo ◽  
Kai Lindström ◽  
Charlotta Kvarnemo
Keyword(s):  
Baltic Sea ◽  
North Sea ◽  
Nest Site ◽  
Operational Sex Ratio ◽  
Female Competition ◽  
The Baltic Sea ◽  
Nest Sites ◽  
The North ◽  
The North Sea ◽  
The Baltic

The operational sex ratio (OSR, ready-to-mate males to females) is a key factor determining mating competition. A shortage of a resource essential for reproduction of one sex can affect OSR and lead to competition within the opposite sex for resource-holding mates. In the sand goby ( Pomatoschistus minutus ), a fish with paternal care, male readiness to mate depends on acquiring a nest-site, whereas food abundance primarily impacts female egg production. Comparing body condition and gonadal investment of fish from two populations with different availability in resources (Baltic Sea: few nest-sites, more food; North Sea: many nest-sites, less food), we predicted females carrying more mature eggs in the Baltic Sea than in the North Sea. As predicted, ovaries were larger in Baltic Sea females, and so was the liver (storage of energy reserves and vitellogenic compounds) for both sexes, but particularly for females. More females were judged (based on roundness scores) to be ready to spawn in the Baltic Sea. Together with a nest colonization experiment confirming a previously documented difference between the two areas in nest-site availability, these results indicate a more female-biased OSR in the Baltic Sea population, compared to the North Sea, and generates a prediction that female–female competition for mating opportunities is stronger in the Baltic population. To our knowledge, this is the first time that female reproductive investment is discussed in relation to OSR using field data.

Iodine-129, Iodine-127 and Cesium-137 in seawater from the North Sea and the Baltic Sea

2016 ◽  
Vol 162-163 ◽  
pp. 289-299 ◽  
Author(s):  
A. Daraoui ◽  
L. Tosch ◽  
M. Gorny ◽  
R. Michel ◽  
I. Goroncy ◽  
...  
Keyword(s):  
Baltic Sea ◽  
North Sea ◽  
The Baltic Sea ◽  
The North ◽  
Cesium 137 ◽  
The North Sea ◽  
The Baltic

scholarly journals Ship emissions of SO<sub>2</sub> and NO<sub>2</sub>: DOAS measurements from airborne platforms

2012 ◽  
Vol 5 (5) ◽  
pp. 1085-1098 ◽  
Author(s):  
N. Berg ◽  
J. Mellqvist ◽  
J.-P. Jalkanen ◽  
J. Balzani
Keyword(s):  
Baltic Sea ◽  
North Sea ◽  
Optical Measurements ◽  
Light Path ◽  
The Baltic Sea ◽  
So2 Emission ◽  
The North ◽  
Geometric Approximation ◽  
The North Sea ◽  
The Baltic

Abstract. A unique methodology to measure gas fluxes of SO2 and NO2 from ships using optical remote sensing is described and demonstrated in a feasibility study. The measurement system is based on Differential Optical Absorption Spectroscopy using reflected skylight from the water surface as light source. A grating spectrometer records spectra around 311 nm and 440 nm, respectively, with the telescope pointed downward at a 30° angle from the horizon. The mass column values of SO2 and NO2 are retrieved from each spectrum and integrated across the plume. A simple geometric approximation is used to calculate the optical path. To obtain the total emission in kg h−1 the resulting total mass across the plume is multiplied with the apparent wind, i.e. a dilution factor corresponding to the vector between the wind and the ship speed. The system was tested in two feasibility studies in the Baltic Sea and Kattegat, from a CASA-212 airplane in 2008 and in the North Sea outside Rotterdam from a Dauphin helicopter in an EU campaign in 2009. In the Baltic Sea the average SO2 emission out of 22 ships was (54 ± 13) kg h−1, and the average NO2 emission was (33 ± 8) kg h−1, out of 13 ships. In the North Sea the average SO2 emission out of 21 ships was (42 ± 11) kg h−1, NO2 was not measured here. The detection limit of the system made it possible to detect SO2 in the ship plumes in 60% of the measurements when the described method was used. A comparison exercise was carried out by conducting airborne optical measurements on a passenger ferry in parallel with onboard measurements. The comparison shows agreement of (−30 ± 14)% and (−41 ± 11)%, respectively, for two days, with equal measurement precision of about 20%. This gives an idea of the measurement uncertainty caused by errors in the simple geometric approximation for the optical light path neglecting scattering of the light in ocean waves and direct and multiple scattering in the exhaust plume under various conditions. A tentative error budget indicates uncertainties within 30–45% but for a reliable error analysis the optical light path needs to be modelled. A ship emission model, FMI-STEAM, has been compared to the optical measurements showing an 18% overestimation and a correlation coefficient (R2) of 0.6. It is shown that a combination of the optical method with modelled power consumption can estimate the sulphur fuel content within 40%, which would be sufficient to detect the difference between ships running at 1% and at 0.1%, limits applicable within the IMO regulated areas.

Population structure of harbour porpoises in the Baltic region: evidence of separation based on geometric morphometric comparisons

2012 ◽  
Vol 92 (8) ◽  
pp. 1669-1676 ◽  
Author(s):  
Anders Galatius ◽  
Carl Christian Kinze ◽  
Jonas Teilmann
Keyword(s):  
Population Structure ◽  
Baltic Sea ◽  
North Sea ◽  
Harbour Porpoise ◽  
Baltic Region ◽  
Geometric Morphometric ◽  
The North ◽  
The North Sea ◽  
The Baltic ◽  
Separate Population

The harbour porpoise is seriously depleted and threatened with extinction in the Baltic Sea. It is usually assumed that Baltic porpoises form a separate population unit, although the evidence for this has been disputed lately. Here, a 3-D geometric morphometric approach was employed to test a number of hypotheses regarding population structure of the harbour porpoise in the Baltic region. 277 porpoise skulls from Denmark, Sweden, Finland, Germany and Poland were measured with a suite of 3-D landmarks. Statistical analyses revealed highly significant shape differences between porpoises from the North Sea, Belt Sea and the inner Baltic Sea. A comparison of the directionalities of the shape vectors between these units found differences that cannot be attributed to a general, continual shape trend going from the North Sea to the inner Baltic Sea. These vectors indicate a morphological adaptation to the specific sub-areas. Such adaptation may be the result of the topographic peculiarities of the area with variable topography and shallow waters, e.g. in the Belt Sea porpoises, there may be a greater reliance on benthic and demersal prey. The present results show that isolation by distance alone is an unlikely explanation for the differences found within the Baltic region and thus support previously reported molecular indications of a separate population within the inner Baltic Sea.

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