Reconstructing historical stock development of Atlantic cod (Gadus morhua) in the eastern Baltic Sea before the beginning of intensive exploitation

2008 ◽  
Vol 65 (12) ◽  
pp. 2728-2741 ◽  
Author(s):  
Margit Eero ◽  
Friedrich W. Köster ◽  
Brian R. MacKenzie
Keyword(s):  
Baltic Sea ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Reference Level ◽  
Stock Size ◽  
Intensive Exploitation ◽  
Spawning Stock ◽  
The 1950S ◽  
The Baltic ◽  
Eastern Baltic

The landings of Atlantic cod ( Gadus morhua ) in the eastern Baltic Sea in the early decades of the 20th century were below 50 thousand tonnes and therefore lower than in recent years at very low stock size. These low landings have largely contributed to a perception that the stock size was also low before the 1950s. In this investigation, we demonstrate that cod spawning stock biomass in the years 1925–1944 fluctuated in a similar range as in the periods from the 1950s to the mid-1970s and from the late 1980s onwards and was in most of these years at least twice as high as at present. Fishing mortality before the 1940s was below 0.2, but reached moderate levels during the Second World War. The stock size before the war may be considered as a reference level of biomass at low fishing impact, providing important information for the management of fisheries and the Baltic ecosystem.

scholarly journals MSY-orientated management of Baltic Sea herring (Clupea harengus) during different ecosystem regimes

2012 ◽  
Vol 69 (2) ◽  
pp. 257-266 ◽  
Author(s):  
Noel M. A. Holmgren ◽  
Niclas Norrström ◽  
Robert Aps ◽  
Sakari Kuikka
Keyword(s):  
Baltic Sea ◽  
Gadus Morhua ◽  
Maximum Sustainable Yield ◽  
Clupea Harengus ◽  
Simultaneous Increase ◽  
Negative Effects ◽  
Planktonic Food ◽  
Spawning Stock ◽  
Food Shortages ◽  
The Baltic

Abstract Holmgren, N. M. A., Norrström, N., Aps, R., and Kuikka, S. 2012. MSY-orientated management of Baltic Sea herring (Clupea harengus) during different ecosystem regimes. – ICES Journal of Marine Science, 69: 257–266. The Baltic Sea ecosystem has undergone dramatic changes, so-called ecosystem regime shifts, during the past four decades. Baltic Sea herring (Clupea harengus) spawning-stock biomass has declined to a third, and weight-at-age has halved as a result of food shortages and competition with sprat (Sprattus sprattus). The management objective for the herring stock is currently in transition from precautionary to maximum sustainable yield (MSY). The main basin Baltic Sea herring was modelled under the current ecosystem regime and the effect of a recovery of the cod (Gadus morhua) stock and the availability of planktonic food to levels found in the early 1980s analysed. A target of FMSY = 0.16 for herring, which should decline to FMSY = 0.10 with recovery of the cod stock, is proposed. An increase in the availability of planktonic food is estimated to more than double the yield at FMSY = 0.27, overriding the negative effects of cod predation should there be a simultaneous increase in both cod and availability of planktonic food. The estimated net increase in yield is 40% at FMSY = 0.20. Functions are presented to calculate FMSY and to estimate the expected yield depending on the abundance of cod and food availability. Retrospective application of the functions is indicative of overfishing of herring in the 1990s and early 2000s, and a net loss in yield, with a landing value of some €440 million.

Feeding and growth of Atlantic cod (Gadus morhua L.) in the eastern Baltic Sea under environmental change

2019 ◽  
Vol 77 (2) ◽  
pp. 624-632 ◽  
Author(s):  
Stefan Neuenfeldt ◽  
Valerio Bartolino ◽  
Alessandro Orio ◽  
Ken H Andersen ◽  
Niels G Andersen ◽  
...  
Keyword(s):  
Growth Rate ◽  
Baltic Sea ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Somatic Growth ◽  
Environmental Forcing ◽  
Average Growth ◽  
Scarce Resources ◽  
Size At Age ◽  
Eastern Baltic

Abstract Five decades of stomach content data allowed insight into the development of consumption, diet composition, and resulting somatic growth of Gadus morhua (Atlantic cod) in the eastern Baltic Sea. We show a recent reversal in feeding level over body length. Present feeding levels of small cod indicate severe growth limitation and increased starvation-related mortality. For young cod, the low growth rate and the high mortality rate are manifested through a reduction in size-at-age. The low feeding levels are likely the result of a decrease in benthic prey abundance due to increased hypoxic areas, while decreasing abundances of pelagic species in the area of cod distribution have prevented a compensatory shift in diet. Our study emphasizes that environmental forcing and the decline in pelagic prey caused changes in consumption and growth rates of small cod. The food reduction is amplified by stunted growth leading to high densities of cod of smaller size competing for the scarce resources. The average growth rate is negative, and only individuals with feeding levels well above average will survive, though growing slowly. These results suggest that the relation between consumption rate, somatic growth and predatorprey population densities is strongly environmentally mediated.

scholarly journals Transcriptome analysis of gill tissue of Atlantic cod Gadus morhua L. from the Baltic Sea

2015 ◽  
Vol 23 ◽  
pp. 37-40 ◽  
Author(s):  
Magdalena Małachowicz ◽  
Agnieszka Kijewska ◽  
Roman Wenne
Keyword(s):  
Baltic Sea ◽  
Transcriptome Analysis ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Gill Tissue ◽  
The Baltic Sea ◽  
The Baltic

Biological indications of contaminant exposure in Atlantic cod (Gadus morhua) in the Baltic Sea

2008 ◽  
Vol 65 (6) ◽  
pp. 1122-1134 ◽  
Author(s):  
Sabine Schnell ◽  
Doris Schiedek ◽  
Rolf Schneider ◽  
Lennart Balk ◽  
Pekka J. Vuorinen ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Organic Contaminants ◽  
Gadus Morhua ◽  
Polychlorinated Biphenyl ◽  
Atlantic Cod ◽  
Human Impacts ◽  
Toxic Substances ◽  
The Baltic Sea ◽  
Contaminant Exposure ◽  
The Baltic

The Baltic Sea is exposed to severe human impacts. Besides eutrophication and overfishing, a variety of chemical contaminants threaten the health of fish. During a cruise in December 2001, Atlantic cod ( Gadus morhua ) were collected in the western and southern Baltic Sea, somatic condition factors were estimated, and different biomarkers of contaminant exposure were analysed. Additionally, various polychlorinated biphenyl congeners and organochlorine pesticides were measured in cod liver as more general indicators of pollution, not necessarily as the causative agents for biomarker signals. In most specimens, hepatic ethoxyresorufin-O-deethylase activity and bile 1-OH pyrene, a common polycyclic aromatic hydrocarbon metabolite, were detectable. Both features indicate an induction of the CYP1A biotransformation system in response to toxic substances. The increased occurrence of DNA adducts in some of the specimens also indicates the presence of genotoxic substances. Acetylcholinesterase was inhibited, an indication of exposure to organophosphates, carbamates, or certain heavy metals, particularly in specimens taken at Wismar Bay and off the Lithuanian coast. In general, spatial differences in the biomarker responses as well as in contaminant loads were found, suggesting differences in physiologically active concentrations and mixtures of organic contaminants in this ecosystem.

scholarly journals Using the particle filter to geolocate Atlantic cod (Gadus morhua) in the Baltic Sea, with special emphasis on determining uncertainty

2007 ◽  
Vol 64 (4) ◽  
pp. 618-627 ◽  
Author(s):  
K H Andersen ◽  
A Nielsen ◽  
U H Thygesen ◽  
H -H Hinrichsen ◽  
S Neuenfeldt
Keyword(s):  
Baltic Sea ◽  
Particle Filter ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Day Length ◽  
Swimming Velocity ◽  
Spatial And Temporal Variability ◽  
The Baltic Sea ◽  
Time Step ◽  
The Baltic

The use of archival tags on fish gives information of individual behaviour with an unprecedented high resolution in time. A central problem in the analysis of data from retrieved tags is the geolocation, namely the infererence of movements of the fish by comparing the data from the tags with environmental observations like temperature, tide, day length, etc. The result is usually represented as a track; however, the spatial and temporal variability in the precision is often substantial. In this article, the particle filter is applied to geolocate Atlantic cod (Gadus morhua) in the Baltic Sea, leading to a representation of the results as probability distributions for each time step, thus giving an explicit representation of uncertainty. Furthermore, the method is used to estimate the magnitude of the error in the measurements by the tags and the swimming velocity of the fish. The average swimming velocity during a day was estimated to be around 0.20 m·s–1 for fish of ~60 cm length. The method is general and the presentation is formulated to facilitate implementation for different systems where other quantities are observed.

scholarly journals Climate-driven long-term trends in Baltic Sea oxygen concentrations and the potential consequences for eastern Baltic cod (Gadus morhua)

2011 ◽  
Vol 68 (10) ◽  
pp. 2019-2028 ◽  
Author(s):  
Hans-Harald Hinrichsen ◽  
Bastian Huwer ◽  
Andrejs Makarchouk ◽  
Christoph Petereit ◽  
Matthias Schaber ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Field Data ◽  
Gadus Morhua ◽  
The Baltic Sea ◽  
Oxygen Conditions ◽  
Long Term Trends ◽  
The Baltic ◽  
Eastern Baltic ◽  
Baltic Cod

Abstract Hinrichsen, H-H., Huwer, B., Makarchouk, A., Petereit, C., Schaber, M., and Voss, R. 2011. Climate-driven long-term trends in Baltic Sea oxygen concentrations and the potential consequences for eastern Baltic cod (Gadus morhua). – ICES Journal of Marine Science, 68: 2019–2028. Variations in oxygen conditions in the Baltic are influenced by several mechanisms. Generally, the frequency and magnitude of major inflows have been identified as the most crucial process for the renewal of oxygen-depleted water masses in the Baltic Sea. Furthermore, enhanced degradation of suspended organic matter by bacteria over the past few decades has increased oxygen consumption. Finally, the effects of large-scale climate warming are causing long-term variations in oxygen content and saturation as an observed increase in temperature has led to a general decrease in oxygen solubility of water masses. Oxygen-dependent relationships based on field data and laboratory experiments were used to analyse the impact of the observed decrease in oxygen content on eastern Baltic cod (Gadus morhua) stock-specific processes (e.g. survival rates of eggs, settlement probability of juveniles, habitat utilization of spawning fish, age structure of successful spawners, food consumption rates of adult fish). The observed long-term decline in oxygen conditions in the Baltic Sea has had a seemingly generally negative impact on oxygen-related processes for the different life stages of eastern Baltic cod. Experimentally derived results of oxygen-driven processes were validated by field data.

scholarly journals Effects of freezing on length and mass measurements of Atlantic cod Gadus morhua in the Baltic Sea

2019 ◽  
Vol 95 (6) ◽  
pp. 1486-1495 ◽  
Author(s):  
Kate McQueen ◽  
Monica Mion ◽  
Annelie Hilvarsson ◽  
Michele Casini ◽  
Hans J. Olesen ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Mass Measurements ◽  
The Baltic Sea ◽  
The Baltic

scholarly journals Eastern Baltic cod in distress: biological changes and challenges for stock assessment

2015 ◽  
Vol 72 (8) ◽  
pp. 2180-2186 ◽  
Author(s):  
Margit Eero ◽  
Joakim Hjelm ◽  
Jane Behrens ◽  
Kurt Buchmann ◽  
Massimiliano Cardinale ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Gadus Morhua ◽  
Stock Assessment ◽  
The Baltic Sea ◽  
Stock Status ◽  
Management Measures ◽  
Stock Assessments ◽  
Management Advice ◽  
The Baltic ◽  
Eastern Baltic

Abstract The eastern Baltic (EB) cod (Gadus morhua) stock was depleted and overexploited for decades until the mid-2000s, when fishing mortality rapidly declined and biomass started to increase, as shown by stock assessments. These positive developments were partly assigned to effective management measures, and the EB cod was considered one of the most successful stock recoveries in recent times. In contrast to this optimistic view, the analytical stock assessment failed in 2014, leaving the present stock status unclear. Deteriorated quality of some basic input data for stock assessment in combination with changes in environmental and ecological conditions has led to an unusual situation for cod in the Baltic Sea, which poses new challenges for stock assessment and management advice. A number of adverse developments such as low nutritional condition and disappearance of larger individuals indicate that the stock is in distress. In this study, we (i) summarize the knowledge of recent changes in cod biology and ecosystem conditions, (ii) describe the subsequent challenges for stock assessment, and (iii) highlight the key questions where answers are urgently needed to understand the present stock status and provide scientifically solid support for cod management in the Baltic Sea.

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