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 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.

scholarly journals The influence of uncertainty in target strength on abundance indices based on acoustic surveys: examples of the Baltic Sea herring and sprat

2009 ◽  
Vol 66 (6) ◽  
pp. 1404-1409 ◽  
Author(s):  
Svetlana M. Kasatkina
Keyword(s):  
Baltic Sea ◽  
Size Structure ◽  
Stock Assessment ◽  
Clupea Harengus ◽  
Statistical Characteristics ◽  
Target Strength ◽  
The Baltic Sea ◽  
Abundance Indices ◽  
Acoustic Surveys ◽  
The Baltic

Abstract Kasatkina, S. M. 2009. The influence of uncertainty in target strength on abundance indices based on acoustic surveys: examples of the Baltic Sea herring and sprat. – ICES Journal of Marine Science, 66: 1404–1409. In situ, target-strength (TS) measurements at 38 kHz and an analysis of biometric fish characteristics are presented for the Baltic Sea herring (Clupea harengus membras) and sprat (Sprattus sprattus). It is demonstrated that the application of two TS–length functions for the Baltic Sea clupeids, the first for young herring and sprat and the second for adult herring, is reasonable, and the two functions can therefore replace the well-known equation used since 1983. Parameters of the proposed relationships, accompanied by their statistical characteristics, are included in a model to obtain uncertainty in acoustically derived abundance indices. Major components of survey uncertainty, such as spatial variability, species composition, and size structure, are also included in the simulation. The proposed TS functions should permit estimates of more realistic abundance dynamics of Baltic Sea clupeids, by years and age groups, thereby providing important information for stock assessment models.

scholarly journals Both predation and feeding opportunities may explain changes in survival of Baltic salmon post-smolts

2012 ◽  
Vol 69 (9) ◽  
pp. 1574-1579 ◽  
Author(s):  
Samu Mäntyniemi ◽  
Atso Romakkaniemi ◽  
Johan Dannewitz ◽  
Stefan Palm ◽  
Tapani Pakarinen ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Clupea Harengus ◽  
Coefficient Of Determination ◽  
Migration Route ◽  
Grey Seal ◽  
Explanatory Variables ◽  
Direct Observations ◽  
The Baltic ◽  
Bothnian Bay ◽  
Bothnian Sea

Abstract Mäntyniemi, S., Romakkaniemi, A., Dannewitz, J., Palm, S., Pakarinen, T., Pulkkinen, H., Gårdmark, A., and Karlsson, O. 2012. Both predation and feeding opportunities may explain changes in survival of Baltic salmon post-smolts. – ICES Journal of Marine Science, 69: 1574–1579. The survival of wild and hatchery-reared post-smolts of salmon (Salmo salar) in the Baltic Sea has declined since the 1990s. Direct observations of the processes affecting survival are, however, lacking. Here, the importance of food availability and predation in regulating post-smolt survival is analysed. Based on previous studies, the following explanatory variables were selected: (i) availability of herring (Clupea harengus membras) recruits in the Gulf of Bothnia (Bothnian Sea, Bothnian Bay) in the northern Baltic Sea; (ii) sprat (Sprattus sprattus balticus) and herring abundance in the southern Baltic Sea; and (iii) abundance of grey seal (Halichoerus grypus) along the post-smolt migration route. Bayesian analysis was used to estimate the relative probability of each of the 32 combinations of these variables and revealed that the model including grey seal abundance and herring recruits per post-smolt had the highest posterior probability and a high coefficient of determination. The results suggest that the declining trend in post-smolt survival is explained by the increased number of grey seals, whereas the annual variation in survival coincides with variation in the recruitment of Bothnian Sea herring. However, it remains uncertain whether the observed correlations arise from direct causalities or other mechanisms.

scholarly journals An ecosystem model of food web and fisheries interactions in the Baltic Sea

2003 ◽  
Vol 60 (5) ◽  
pp. 939-950 ◽  
Author(s):  
Chris J Harvey ◽  
Sean P Cox ◽  
Timothy E Essington ◽  
Sture Hansson ◽  
James F Kitchell
Keyword(s):  
Baltic Sea ◽  
Food Web ◽  
Species Interactions ◽  
Gadus Morhua ◽  
Population Analysis ◽  
Clupea Harengus ◽  
Trophic Relationships ◽  
The Baltic Sea ◽  
Management Actions ◽  
The Baltic

Abstract Because fisheries operate within a complex array of species interactions, scientists increasingly recommend multispecies approaches to fisheries management. We created a food web model for the Baltic Sea proper, using the Ecopath with Ecosim software, to evaluate interactions between fisheries and the food web from 1974 to 2000. The model was based largely on values generated by multispecies virtual population analysis (MSVPA). Ecosim outputs closely reproduced MSVPA biomass estimates and catch data for sprat (Sprattus sprattus), herring (Clupea harengus), and cod (Gadus morhua), but only after making adjustments to cod recruitment, to vulnerability to predation of specific species, and to foraging times. Among the necessary adjustments were divergent trophic relationships between cod and clupeids: cod exhibited top-down control on sprat biomass, but had little influence on herring. Fishing, the chief source of mortality for cod and herring, and cod reproduction, as driven by oceanographic conditions as well as unexplained variability, were also key structuring forces. The model generated many hypotheses about relationships between key biota in the Baltic Sea food web and may ultimately provide a basis for estimating community responses to management actions.

Impact of Spawning Substrate Complexity on Egg Survival of Atlantic Herring (Clupea harengus, L.) in the Baltic Sea

2017 ◽  
Vol 41 (2) ◽  
pp. 549-559 ◽  
Author(s):  
Lena von Nordheim ◽  
Paul Kotterba ◽  
Dorothee Moll ◽  
Patrick Polte
Keyword(s):  
Baltic Sea ◽  
Clupea Harengus ◽  
Atlantic Herring ◽  
The Baltic Sea ◽  
Egg Survival ◽  
Spawning Substrate ◽  
The Baltic

scholarly journals Nitrogen fixation estimates for the Baltic Sea indicate high rates for the previously overlooked Bothnian Sea

AMBIO ◽  
2020 ◽  
Vol 50 (1) ◽  
pp. 203-214 ◽  
Author(s):  
Malin Olofsson ◽  
Isabell Klawonn ◽  
Bengt Karlson
Keyword(s):  
Nitrogen Fixation ◽  
Baltic Sea ◽  
Nutrient Loading ◽  
External Input ◽  
Nitrogen Loading ◽  
External Loading ◽  
The Baltic Sea ◽  
Positive Effects ◽  
The Baltic ◽  
Bothnian Sea

AbstractDense blooms of diazotrophic filamentous cyanobacteria are formed every summer in the Baltic Sea. We estimated their contribution to nitrogen fixation by combining two decades of cyanobacterial biovolume monitoring data with recently measured genera-specific nitrogen fixation rates. In the Bothnian Sea, estimated nitrogen fixation rates were 80 kt N year−1, which has doubled during recent decades and now exceeds external loading from rivers and atmospheric deposition of 69 kt year−1. The estimated contribution to the Baltic Proper was 399 kt N year−1, which agrees well with previous estimates using other approaches and is greater than the external input of 374 kt N year−1. Our approach can potentially be applied to continuously estimate nitrogen loads via nitrogen fixation. Those estimates are crucial for ecosystem adaptive management since internal nitrogen loading may counteract the positive effects of decreased external nutrient loading.

Environmental genotoxicity and cytotoxicity levels in herring (Clupea harengus), flounder (Platichthys flesus) and cod (Gadus morhua) inhabiting the Gdansk Basin of the Baltic Sea

2018 ◽  
Vol 133 ◽  
pp. 65-76 ◽  
Author(s):  
Roberta Valskienė ◽  
Janina Baršienė ◽  
Laura Butrimavičienė ◽  
Wlodzimierz Grygiel ◽  
Virmantas Stunžėnas ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Gadus Morhua ◽  
Clupea Harengus ◽  
The Baltic Sea ◽  
Platichthys Flesus ◽  
The Baltic ◽  
Environmental Genotoxicity

The first large-scale assessment of three-spined stickleback (Gasterosteus aculeatus) biomass and spatial distribution in the Baltic Sea

2019 ◽  
Vol 76 (6) ◽  
pp. 1653-1665 ◽  
Author(s):  
Jens Olsson ◽  
Eglė Jakubavičiūtė ◽  
Olavi Kaljuste ◽  
Niklas Larsson ◽  
Ulf Bergström ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Baltic Sea ◽  
Gasterosteus Aculeatus ◽  
Population Characteristics ◽  
Alternative Methods ◽  
The Baltic Sea ◽  
Baltic Proper ◽  
The Baltic ◽  
The Impact ◽  
Bothnian Sea

Abstract Declines in predatory fish in combination with the impact of climate change and eutrophication have caused planktivores, including three-spined stickleback (Gasterosteus aculeatus), to increase dramatically in parts of the Baltic Sea. Resulting impacts of stickleback on coastal and offshore foodwebs have been observed, highlighting the need for increased knowledge on its population characteristics. In this article, we quantify abundance, biomass, size structure, and spatial distribution of stickleback using data from the Swedish and Finnish parts of the Baltic International Acoustic Survey (BIAS) during 2001–2014. Two alternative methods for biomass estimation suggest an increase in biomass of stickleback in the Baltic Proper, stable or increasing mean size over time, and larger individuals toward the north. The highest abundance was found in the central parts of the Baltic Proper and Bothnian Sea. The proportion of stickleback biomass in the total planktivore biomass increased from 4 to 10% in the Baltic Proper and averaged 6% of the total planktivore biomass in the Bothnian Sea. In some years, however, stickleback biomass has ranged from half to almost twice that of sprat (Sprattus sprattus) in both basins. Given the recent population expansion of stickleback and its potential role in the ecosystem, we recommend that stickleback should be considered in future monitoring programmes and in fisheries and environmental management of the Baltic Sea.

scholarly journals Fractionation of iron species and iron isotopes in the Baltic Sea euphotic zone

2010 ◽  
Vol 7 (8) ◽  
pp. 2489-2508 ◽  
Author(s):  
J. Gelting ◽  
E. Breitbarth ◽  
B. Stolpe ◽  
M. Hassellöv ◽  
J. Ingri
Keyword(s):  
Baltic Sea ◽  
Isotope Composition ◽  
Salinity Gradient ◽  
Euphotic Zone ◽  
Early Spring ◽  
Strong Positive Correlation ◽  
The Baltic Sea ◽  
Gotland Deep ◽  
The Baltic ◽  
Bothnian Sea

Abstract. To indentify sources and transport mechanisms of iron in a coastal marine environment, we conducted measurements of the physiochemical speciation of Fe in the euphotic zone at three different locations in the Baltic Sea. In addition to sampling across a salinity gradient, we conducted this study over the spring and summer season. Moving from the riverine input characterized low salinity Bothnian Sea, via the Landsort Deep near Stockholm, towards the Gotland Deep in the Baltic Proper, total Fe concentrations averaged 114, 44, and 15 nM, respectively. At all three locations, a decrease in total Fe of 80–90% from early spring to summer was observed. Particulate Fe (PFe) was the dominating phase at all stations and accounted for 75–85% of the total Fe pool on average. The Fe isotope composition (δ 56Fe) of the PFe showed constant positive values in the Bothnian Sea surface waters (+0.08 to +0.20‰). Enrichment of heavy Fe in the Bothnian Sea PFe is possibly associated to input of aggregated land derived Fe-oxyhydroxides and oxidation of dissolved Fe(II). At the Landsort Deep the isotopic fractionation of PFe changed between −0.08‰ to +0.28‰ over the sampling period. The negative values in early spring indicate transport of PFe from the oxic-anoxic boundary at ∼80 m depth. The average colloidal iron fraction (CFe) showed decreasing concentrations along the salinity gradient; Bothnian Sea 15 nM; Landsort Deep 1 nM, and Gotland Deep 0.5 nM. Field Flow Fractionation data indicate that the main colloidal carrier phase for Fe in the Baltic Sea is a carbon-rich fulvic acid associated compound, likely of riverine origin. A strong positive correlation between PFe and chl-a indicates that cycling of suspended Fe is at least partially controlled by primary production. However, this relationship may not be dominated by active uptake of Fe into phytoplankton, but instead may reflect scavenging and removal of PFe during phytoplankton sedimentation.

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