scholarly journals Using data storage tags to link otolith macro- structure in Baltic cod Gadus morhua with environmental conditions

2009 ◽  
Vol 378 ◽  
pp. 161-170 ◽  
Author(s):  
K Hüssy ◽  
B Nielsen ◽  
H Mosegaard ◽  
LW Clausen
Keyword(s):  
Data Storage ◽  
Environmental Conditions ◽  
Gadus Morhua ◽  
Data Storage Tags ◽  
Using Data ◽  
Baltic Cod

scholarly journals Life under pressure: insights from electronic data-storage tags into cod swimbladder function

2007 ◽  
Vol 64 (7) ◽  
pp. 1293-1301 ◽  
Author(s):  
Jeroen van der Kooij ◽  
David Righton ◽  
Espen Strand ◽  
Kathrine Michalsen ◽  
Vilhjalmur Thorsteinsson ◽  
...  
Keyword(s):  
Data Storage ◽  
Gadus Morhua ◽  
Fish Length ◽  
Pressure Reduction ◽  
Electronic Data ◽  
Data Storage Tags ◽  
Rapid Ascent ◽  
Using Data ◽  
Electronic Tagging ◽  
Negatively Buoyant

Abstract van der Kooij, J., Righton, D., Strand, E., Michalsen, K., Thorsteinsson, V., Svedäng, H., Neat, F. C., and Neuenfeldt, S. 2007. Life under pressure: insights from electronic data-storage tags into cod swimbladder function. – ICES Journal of Marine Science. 64: 1293–1301. The behavioural response of cod (Gadus morhua) to sudden pressure reductions was investigated in a large electronic-tagging experiment using data collected from 141 cod tagged in five different areas of the Northeast Atlantic. More than 40% of cod exhibited a characteristic equilibration behaviour after a rapid pressure reduction caused either by capture before tagging, or by pressure reduction during a rapid ascent from the seabed, or when migrating to deeper water. The equilibration allowed the cod to regain demersal residence. The rate of descent averaged 10 m d−1 (ranging from 2 to 23 m d−1) over periods of less than a day to 1 month. Descent rates for cod on the Icelandic shelf were inversely related to fish length, i.e. smaller fish descended more rapidly, findings consistent with results achieved in the past under laboratory conditions. Modelling of swimbladder volume during equilibration suggested that cod were negatively buoyant for most of the time. The results imply that swimbladder functionality is retained after the probable barotrauma that would follow a large and rapid ascent, and that rates of gas exchange into the swimbladder may be naturally variable. These findings have implications for assumptions on discard mortality, the interpretation of cod behaviour, and its impact on biomass estimates obtained from acoustic surveys.

scholarly journals Evidence for alternative migratory behaviours in the northern Gulf of St Lawrence population of Atlantic cod (Gadus morhua L.)

2013 ◽  
Vol 70 (4) ◽  
pp. 793-804 ◽  
Author(s):  
Arnault Le Bris ◽  
Alain Fréchet ◽  
Peter S. Galbraith ◽  
Joseph S. Wroblewski
Keyword(s):  
Data Storage ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Fork Length ◽  
Daily Maximum ◽  
Migration Routes ◽  
Data Storage Tags ◽  
Spawning Behaviour ◽  
Using Data ◽  
Migration Propensity

Abstract Le Bris, A., Fréchet, A., Galbraith, P. S., and Wroblewski, J. S. 2013. Evidence for alternative migratory behaviours in the northern Gulf of St Lawrence population of Atlantic cod (Gadus morhua L.). – ICES Journal of Marine Science, 70: 793–804. Inter-individual variation in migration propensity affects population dynamics and connectivity. The diversity of migratory behaviours of Atlantic cod (fork length >40 cm) in the northern Gulf of St Lawrence was studied using data-storage tags that record depth and temperature. Movement patterns of Atlantic cod equipped with data-storage tags were reconstructed using a geolocation model based on daily maximum depth and bottom temperature. Reconstructed migration routes revealed the previously undocumented coexistence of resident and migratory individuals in the population. Migratory cod overwintered in relatively deep (300–500 m) and warm (5°C) waters, while residents displayed a prolonged period of immobility in shallow (<100 m) and near-freezing (–1.5°C) coastal waters of western Newfoundland. In the spring, migratory cod displayed extensive diel vertical migration suggestive of spawning behaviour. The presence of alternative migratory behaviours should be considered in the spatiotemporal management of the collapsed population.

scholarly journals Post-smolt survival of Baltic salmon in context to changing environmental conditions and predators

2016 ◽  
Vol 74 (5) ◽  
pp. 1344-1355 ◽  
Author(s):  
Kevin D. Friedland ◽  
Johan Dannewitz ◽  
Atso Romakkaniemi ◽  
Stefan Palm ◽  
Henni Pulkkinen ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Coastal Waters ◽  
Gadus Morhua ◽  
Environmental Parameters ◽  
Predation Pressure ◽  
First Year ◽  
Central Basin ◽  
The Baltic ◽  
Latitudinal Range ◽  
Baltic Cod

The survival of Baltic salmon Salmo salar during the first year at sea (post-smolt stage) has declined since the beginning of the 1990s. In this analysis, we complement previous studies on possible causes of this decline by considering a suite of environmental parameters, potential change in predation pressure, and post-smolt growth. Marine survival estimates were found to be negatively correlated with temperature, indicating that warming conditions have not favoured survival. Survival was also found to be positively correlated with dissolved oxygen levels and regionally related to shifts in salinity. These relationships were further studied in context to the potential predation on post-smolts by one of the main piscivores in the Baltic, Eastern Baltic cod (Gadus morhua callarias). Concomitant with changes in environmental conditions, Baltic cod has changed its latitudinal range, moving northward in the Baltic, possibly in response to warming conditions. These changes lead us to hypothesize that predation pressure on salmon may have increased in recent years as cod has now occupied habitats used by salmon post-smolts during their southward feeding migrations. This predation may have been intensified as a result of anoxic conditions in the central basin by concentrating predation interactions in coastal waters and/or the upper water column typically occupied by salmon post-smolts. Indicators of post-smolt growth were applied to test the alternate hypothesis that mortality is growth-mediated; these indicators lacked a time series trend, which supports the contention that shifting predation pressure rather than feeding opportunities is responsible for the decline in post-smolt survival in Baltic salmon.

Reconstructing migrations of individual cod (Gadus morhua L.) in the Baltic Sea by using electronic data storage tags

2007 ◽  
Vol 16 (6) ◽  
pp. 526-535 ◽  
Author(s):  
STEFAN NEUENFELDT ◽  
HANS-HARALD HINRICHSEN ◽  
ANDERS NIELSEN ◽  
KEN H. ANDERSEN
Keyword(s):  
Baltic Sea ◽  
Data Storage ◽  
Gadus Morhua ◽  
The Baltic Sea ◽  
Electronic Data ◽  
Data Storage Tags ◽  
The Baltic

Migration patterns of the Faroe Plateau cod ( Gadus morhua , L.) revealed by data storage tags

2017 ◽  
Vol 195 ◽  
pp. 37-45 ◽  
Author(s):  
Katharina Maj Ottosen ◽  
Martin Wæver Pedersen ◽  
Sólvá Káradottir Eliasen ◽  
Petur Steingrund ◽  
Eyðfinn Magnussen ◽  
...  
Keyword(s):  
Data Storage ◽  
Gadus Morhua ◽  
Migration Patterns ◽  
Data Storage Tags

Modeling environmentally driven uncertainties in Baltic cod (Gadus morhua) management by Bayesian influence diagrams

1999 ◽  
Vol 56 (4) ◽  
pp. 629-641 ◽  
Author(s):  
S Kuikka ◽  
M Hildén ◽  
H Gislason ◽  
S Hansson ◽  
H Sparholt ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Gadus Morhua ◽  
Saline Water ◽  
Mesh Size ◽  
Influence Diagrams ◽  
Large Variability ◽  
Trawl Fishery ◽  
Management Advice ◽  
Estimation Of Uncertainties ◽  
Baltic Cod

The large variability in Baltic cod (Gadus morhua) recruitment has been attributed both to environmental factors dependent on the inflow of saline water (oxygen and salinity in spawning deeps) and to the size of the spawning stock. Due to the complex interactions between hydrographic and biological processes, future recruitment levels of cod will remain highly uncertain and increase uncertainties in stock predictions and management advice. We assessed the effects of the exploitation level and mesh size used by a trawl fishery on some variables of management interest under different environmental conditions. The modeling consisted of three separate steps: (i) modeling of selectivity, (ii) estimation of uncertainties by Monte Carlo simulations, and (iii) decision analysis by Bayesian influence diagrams, focusing on the structural uncertainties and model selection. Realistic assumptions of environmental conditions and present fishing mortality rates suggest that the current Baltic cod fishery is unsustainable. We use our approach to identify robust management measures that reduce the risk of overfishing and the sensitivity to management information. The value of information analysis demonstrates the advantages of a larger mesh size as a management measure.

scholarly journals Hydrographic influence on the spawning habitat suitability of western Baltic cod (Gadus morhua)

2012 ◽  
Vol 69 (10) ◽  
pp. 1736-1743 ◽  
Author(s):  
K. Hüssy ◽  
H.-H. Hinrichsen ◽  
B. Huwer
Keyword(s):  
Water Temperature ◽  
Environmental Conditions ◽  
Habitat Suitability ◽  
Gadus Morhua ◽  
Reproductive Potential ◽  
Spawning Season ◽  
Spawning Habitat ◽  
Egg Survival ◽  
The Impact ◽  
Baltic Cod

Abstract Hüssy, K., Hinrichsen, H.-H., and Huwer, B. 2012. Hydrographic influence on the spawning habitat suitability of western Baltic cod (Gadus morhua) – ICES Journal of Marine Science, 69: 1736–1743. Recruitment variability of marine fish is influenced by the reproductive potential of the stock (i.e. stock characteristics and abundance) and the survival of early life stages, mediated by environmental conditions of both a physical (water temperature, salinity and oxygen conditions, ocean currents) and a biological nature (i.e. food, predators). The objective of this study is to assess the importance of variability in environmental conditions within different western Baltic cod spawning grounds for egg survival. Habitat identification was based on environmental threshold levels for egg survival and development and ambient hydrographical conditions at different times during the spawning season. The long-term resolution of environmental conditions allowing survival of western Baltic cod eggs indicates that favourable conditions predominantly occurred during the late spawning season in April/May, while minimum survival rates could be expected from January to March. Unsuitable time periods and habitats exhibiting the highest mortality rates are exclusively characterized by ambient water temperatures below the critical survival threshold. Despite the strong influence of water temperature on habitat suitability, the impact of habitat suitability on recruitment was not clearly defined, suggesting that other mechanisms regulate year class strength.

Connectivity among offshore feeding areas and nearshore spawning grounds; implications for management of migratory fish

2017 ◽  
Vol 75 (1) ◽  
pp. 148-157 ◽  
Author(s):  
Jón Sólmundsson ◽  
Ingibjörg G Jónsdóttir ◽  
Stefán Á Ragnarsson ◽  
Björn Björnsson
Keyword(s):  
Data Storage ◽  
Gadus Morhua ◽  
Migratory Fish ◽  
Long Distance ◽  
Migration Patterns ◽  
Spatial Management ◽  
Data Storage Tags ◽  
Low Levels ◽  
Mature Fish ◽  
Migration Pathways

Abstract Knowing movement and structure of fish populations is a prerequisite for effective spatial fisheries management. The study evaluates migration patterns and connectivity of two groups of cod (Gadus morhua) associated with offshore feeding and nursery grounds. This was achieved by investigating (i) migration pathways of cod tagged at the feeding areas, (ii) immigration of cod to the areas based on mark-recapture data covering a period of two decades, and (iii) depth and temperature data from data storage tags (DSTs). Despite undertaking long-distance migrations after attaining sexual maturity, the cod aggregations in the two study areas appear to be largely separated from each other. This conclusion is supported by DSTs, indicating that mature fish associated with the two areas occupy different thermal-bathymetric niches. Low levels of connectivity suggest that effective spatial management in the two study areas would preserve fish of different origin. For the highly migratory adults, however, spatial management would need to focus on migration pathways and the areas where the fish are particularly vulnerable to fishing.

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