Sverdrup G.K.,University of Bergen |
Meager J.J.,University of Bergen |
Ferno A.,University of Bergen |
Ferno A.,Norwegian Institute of Marine Research |
And 6 more authors.
Aquaculture Research | Year: 2011
Studies of contest competition between wild and farmed fish have mostly focused on fish with strongly territorial behaviour. Little is known about species with more plastic social behaviour, such as Atlantic cod (Gadus morhua L.), a species that can either aggressively defend territories or shoal. There is also concern that cod that escape from farms will compete with wild populations. We examined dyadic contest competition between wild and farmed juvenile cod using an intruder-resident experimental set-up in the laboratory. No prior residency advantage was observed, but the differences between farmed and wild cod were clear. Farmed cod were more submissive than wild cod and fled earlier during contests, which suggests that wild fish often out-compete farmed intruders. Both fish types initiated aggression earlier against fish of the same background. A multivariate analysis of 11 different behavioural traits indicated that a group of 59% of farmed fish were behaviourally very similar to the 55% most submissive wild fish. These results suggest that wild juvenile cod may be quite robust towards competition for food and shelter from juvenile farmed cod, but further research is needed to verify this pattern. © 2010 Blackwell Publishing Ltd.
Westerberg H.,Swedish Board of Fisheries |
Westerberg K.,Lund University
Fisheries Research | Year: 2011
The formation of an odour trail can be broken down into a chain of events: first, the emission of the attractant from the bait, second, a turbulent mixing into the immediate surroundings and third, a downstream advection and dispersion of the attractant by the current flowing past the bait. In this work, a simple analysis of the physical processes governing the first two stages shows that the release of attractant will decline as the inverse of the square root of time. The decline curve will be similar for all solid natural baits within a realistic size range during normal soak times.Experiments were performed to measure typical diffusion constants of odour substances in fish tissue and it is shown that due to the low diffusivity just a thin surface layer will release its content of odour substances during a fishing operation using pieces of fish as bait. Moreover, the initial concentration of attractant when a plume is formed will be independent of the size of a solid bait and only depend on the ratio of the surface area to the cross-section area of the bait. To increase the maximum concentration of odour substance in the plume and utilize a given amount of bait optimally, a solid bait should be cut into smaller pieces. The effect of current speed on the initial odour concentration in the plume is strong. Due to speed variations during the soak time the effectiveness of the attraction will vary in time.To extend the analysis and develop models for optimization of the range of the olfactory signal from a bait it is necessary to know both the concentration of the attractant in the bait and the target species detection threshold. When such data become available it will be possible to estimate the range of attraction of baits under different environmental conditions. © 2011 Elsevier B.V.
Cardinale M.,Swedish Board of Fisheries |
Bartolino V.,Swedish Board of Fisheries |
Bartolino V.,Gothenburg University |
Llope M.,University of Oslo |
And 3 more authors.
Fish and Fisheries | Year: 2011
Increased knowledge on the spatial distribution of marine resources is crucial for the implementation of a true ecosystem approach to management and the conservation of marine organisms. For exploited fish species characterized by aggregation behaviour during spawning time, the identification and tracking of spawning areas is essential for a correct assessment of their productivity and population abundance. To elucidate this concept, we reconstructed the spatio-temporal distribution of adult plaice (Pleuronectes platessa, Pleuronectidae) during spawning time along the 20 th century. Historical data reveal that not only the abundance but also the former population richness was much higher than previously estimated and has declined because of protracted over-exploitation during the last 30years. We conclude that forecast of stock recovery to former levels of abundance neglecting spatial reorganizations might be over-optimistic and shaded by a lost memory of the past population richness. These results reinforce the importance of managing exploited marine resources at a greater spatial resolution than has been carried out in the history of fishery management. © 2010 Blackwell Publishing Ltd.
Waldo S.,Swedish University of Agricultural Sciences |
Paulrud A.,Swedish University of Agricultural Sciences |
Jonsson A.,Swedish Board of Fisheries
Marine Policy | Year: 2010
The cod stocks in the Baltic Sea are important not only for fisheries but for the entire ecosystem utilized by numerous stakeholders around the coast. All such activities have economic values. In this note the economics of the Swedish Baltic Sea cod fishery is estimated in relation to the sector's interaction with other users of the Baltic Sea ecosystem. The results show a negative resource rent for the fishery, € -5 million without public expenses (subsidies and administrative costs), and € -13 million including public expenses. The interactions between the fisheries and tourism, seal population, carbon dioxide emissions, recreational fishing, and discards are discussed, and when monetary estimates are available these are related to the estimated resource rent. © 2009 Elsevier Ltd. All rights reserved.
Righton D.A.,CEFAS - Center for Environment, Fisheries and Aquaculture Science |
Andersen K.H.,Technical University of Denmark |
Neat F.,Marine Scotland - Marine Laboratory |
Thorsteinsson V.,Iceland Marine Research Institute |
And 13 more authors.
Marine Ecology Progress Series | Year: 2010
Recent studies in the marine environment have suggested that the limited phenotypic plasticity of cold-adapted species such as Atlantic cod Gadus morhua L. will cause distributions to shift toward the poles in response to rising sea temperatures. Some cod stocks are predicted to collapse, but this remains speculative because almost no information is available on the thermal tolerance of cod in its natural environment. We used electronic tags to measure the thermal experience of 384 adult Atlantic cod from 8 different stocks in the northeast Atlantic. Over 100 000 d of data were collected in total. The data demonstrate that cod is an adaptable and tolerant species capable of surviving and growing in a wide range of temperate marine climates. The total thermal niche ranged from -1.5 to 19°C; this range was narrower (1 to 8°C) during the spawning season. Cod in each of the stocks studied had a thermal niche of approximately 12°C, but latitudinal differences in water temperature meant that cod in the warmer, southern regions experienced 3 times the degree days (DD; ∼4000 DD yr-1) than individuals from northern regions (∼1200 DD yr-1). Growth rates increased with temperature, reaching a maximum in those cod with a mean thermal history of between 8 and 10°C. Our direct observations of habitat occupation suggest that adult cod will be able to tolerate warming seas, but that climate change will affect cod populations at earlier life-history stages as well as exerting effects on cod prey species. © Inter-Research 2010.
Meager J.J.,University of Bergen |
Rodewald P.,University of Bergen |
Rodewald P.,University of Helsinki |
Domenici P.,CNR Institute for Coastal Marine Environment |
And 6 more authors.
Journal of Fish Biology | Year: 2011
The behavioural responses of wild (predator-experienced) and hatchery-reared (predator-naive) cod Gadus morhua to standardized mechano-acoustic (MA) stimuli were compared in the laboratory. Wild fish responded mainly with freezing and fast-start escapes away from the stimulus, whereas hatchery-reared fish often ignored or approached the stimulus. Wild fish also had stronger responses, turning faster during escapes and reducing activity immediately after the stimulus. Both fish types were less active on a 'risky' bare substratum after the stimulus. The antipredator responses of wild fish were consistent to repeated stimuli, whereas hatchery-reared fish that had generally only encountered harmless stimuli showed more variable responses with lower repeatability. This suggests that experience plays a role in shaping the behavioural response of fishes to MA stimuli. © 2011 The Authors. Journal of Fish Biology © 2011 The Fisheries Society of the British Isles.
Sjogren M.,Uppsala University |
Jonsson P.R.,Gothenburg University |
Dahlstrom M.,Swedish Board of Fisheries |
Lundalv T.,Gothenburg University |
And 3 more authors.
Journal of Natural Products | Year: 2011
The current work shows that two structurally similar cyclodipeptides, barettin (1) and 8,9-dihydrobarettin (2), produced by the coldwater marine sponge Geodia barretti Bowerbank act in synergy to deter larvae of surface settlers and may also be involved in defense against grazers. Previously, 1 and 2 were demonstrated to bind specifically to serotonergic 5-HT receptors. It may be suggested that chemical defense in G. barretti involves a synergistic action where one of the molecular targets is a 5-HT receptor. A mixture of 1 and 2 lowered the EC50 of larval settlement as compared to the calculated theoretical additive effect of the two compounds. Moreover, an in situ sampling at 120 m depth using a remotely operated vehicle revealed that the sponge releases these two compounds to the ambient water. Thus, it is suggested that the synergistic action of 1 and 2 may benefit the sponge by reducing the expenditure of continuous production and release of its chemical defense substances. Furthermore, a synergistic action between structurally closely related compounds produced by the same bioenzymatic machinery ought to be the most energy effective for the organism and, thus, is more common than synergy between structurally indistinct compounds. © 2011 The American Chemical Society and American Society of Pharmacognosy.
Daverat F.,IRSTEA |
Beaulaton L.,ONEMA |
Poole R.,Marine Institute of Ireland |
Lambert P.,IRSTEA |
And 7 more authors.
Ecology of Freshwater Fish | Year: 2012
A cooperative effort gathered a large European length-at-age data set (N=45,759, Lat. 36S-61N Long. 10W-27E) for Anguilla anguilla, covering one century. To assess the effect of global warming during the last century and habitat effects on growth, a model was fitted on the data representing the conditions met at the distribution area scale. Two GLMs were designed to predict eel log(GR): one model was fitted to the whole data and the other was fitted to the female data subset. A model selection procedure was applied to select the best predictors among sex, age class, five temperature parameters and six habitat parameters (depth, salinity and four variables related to the position in the catchment). The yearly sum of temperatures above 13°C (TempSUP13), the relative distance within the catchment, sex, age class, salinity class and depth class were finally selected. The best model predicted eel log(GR) with a 64.46% accuracy for the whole data and 66.91% for the female eel data. Growth rate (GR) was greater in habitats close to the sea and in deep habitats. TempSUP13 variable had one of the greatest predictive powers in the model, showing that global warming had affected eel growth during the last century. © 2012 John Wiley & Sons A/S.
Ratner B.D.,WorldFish |
Asgard B.,Swedish Board of Fisheries |
Allison E.H.,University of Washington
Global Environmental Change | Year: 2014
A review of case law and other documentation of human rights issues in fishing communities highlights forced evictions, detention without trial, child labour, forced labour and unsafe working conditions, and violence and personal security, including gender-based violence, as key areas of concern. We argue that human rights violations undermine current attempts to reform the fisheries sector in developing countries by increasing the vulnerability and marginalization of certain groups. Citing cases from India, the Philippines, Cambodia, and South Africa, we show how human rights advocacy can be an effective element of support for development in fisheries. Finally, we outline how fisheries reform can better address human rights issues as an essential complement to the equitable allocation of fishing rights, contributing to improved resource management and human wellbeing. © 2014 The Authors.
Hedman J.E.,Swedish Museum of Natural History |
Rudel H.,Fraunhofer Institute for Molecular Biology and Applied Ecology |
Gercken J.,Institute of Applied Ecology Ltd. |
Bergek S.,Swedish Board of Fisheries |
And 6 more authors.
Marine Pollution Bulletin | Year: 2011
The implementation of the EU Marine Strategy Framework Directive necessitates the development of common criteria and methodological standards for marine environmental monitoring and assessment across Europe. Eelpout (Zoarces viviparus) is proposed as a key indicator organism in the Baltic and North Sea regions. This benthic fish species is widely used in ecotoxicological studies and as a bioindicator of local pollution due to its stationary behavior. Eelpout is included in the environmental monitoring program of several Baltic States, covering both chemical and biological effects measurements, and samples have been archived in environmental specimen banks for >15. years. A method for evaluating the frequency of larval aberrations has been suggested as a standardized assessment tool. The large scientific knowledge-base and considerable experience of long-term chemical and biological effects monitoring and specimen banking, make eelpout a suitable species for the assessment of Good Environmental Status in the Baltic and North Seas. © 2011 Elsevier Ltd.