2019
 

Behaviour of adult sea trout Salmo trutta that survive or die at sea

År: 2019

Behaviour of adult sea trout Salmo trutta that survive or die at sea

Kristensen, M. L., Righton, D., Villar-Guerra, D. D., Baktoft, H. & Aarestrup, K., 2019, In : Estuarine, Coastal and Shelf Science. 227, 106310.

Research output: Contribution to journalJournal article – Annual report year: 2019Researchpeer-review

We tagged 125 sea trout kelts (460–925 mm) in seven Danish rivers with positively buoyant DSTs. Fifty-three (42%) tags were recovered, enabling a comparison of behaviour in kelts that survived the marine period and kelts that did not. Data revealed an estimated mean survival time at sea of 14.3 days (range 1–65 days) for fish that died at sea. Fish that did not survive had lower weight/length ratios when tagged than survivors (P = 0.005) but exhibited a similar diel diving pattern while at sea. Both surviving and non-surviving fish gradually increased diving activity and the daily visited maximum depths after sea entry, but some performed fewer dives and resided in shallower depths than others. This difference was pronounced when comparing surviving fish (most active divers) with fish caught by anglers (least active divers). The results show that the first weeks at sea are critical for kelt survival and that physical status of kelts may affect behaviour and probability of survival. The preference for shallower waters and less diving activity in some individuals indicate that coastally based fisheries and recreational angling may select against specific behavioural phenotypes which should be investigated more intensively.
Original languageEnglish
Article number106310
JournalEstuarine, Coastal and Shelf Science
Volume227
ISSN0272-7714
DOIs
Publication statusPublished - 2019

 

Maritim arealplanlægning i Øresund: Scenarier for udvikling af erhvervs-, samfunds- og miljømæssige forhold

År: 2019

Maritim arealplanlægning i Øresund: Scenarier for udvikling af erhvervs-, samfunds- og miljømæssige forhold

Riemann, B., Al-Hamdani, Z., Olafsson, A. S., Hasler, B., Kaae, B. C., Murray, C., Göke, C., Kallenbach, E., Olesen, H. J., Nabe-Nielsen, J., Tougaard, J., Andersen, J. H., Egekvist, J., Overgaard Leth, J., Dahl, K., Christoffersen, M., Zandersen, M., Termansen, M., Sveegaard, S. & Harvey, T., 2019, 174 p. (MiljøBiblioteket; No. 6).

Research output: Book/ReportBook – Annual report year: 2019Research

Øresund er et af de mest befærdede farvande og kystområder i verden. Store container- og krydstogtskibe passerer igennem på langs, mens færgetrafikken og Øresundsbroen går på tværs mellem Danmark og Sverige. Samtidig skal der være plads til både havmølleparker, byudvikling, fiskeri, lystbådesejlads og friluftsliv, ligesom områdets rige natur og dyreliv skal tilgodeses. Det stiller store krav til planlægningen af arealudnyttelsen.
Maritim arealplanlægning i Øresund giver indblik i, hvordan vi kan bevare havmiljøet i regionen og samtidig skabe en bæredygtig erhvervs- og samfundsudvikling. Én mulighed er at lave Øresund om til et stort naturreservat og på den måde understøtte en positiv udvikling af havmiljøet, tiltrække turister og styrke friluftslivet. Men det vil formentlig også betyde
et stop for indvinding af råstoffer til byggebranchen og restriktioner for fiskeriet. Som i ethvert andet økosystem er det afgørende at finde frem til den rette balance mellem forskellige aktiviteter og interesser. Her kan det travle stræde mellem Sjælland og Skåne tjene som eksempel på, hvordan man kan analysere konflikter og muligheder for sameksistens, og erfaringerne kan med fordel overføres til andre danske havområder.
Original languageDanish
Number of pages174
ISBN (Print)978-87-7184-887-8
Publication statusPublished - 2019
SeriesMiljøBiblioteket
Number6

 

Hypoxia but not shy-bold phenotype mediates thermal preferences in a threatened freshwater fish, Notropis percobromus

År: 2019

Hypoxia but not shy-bold phenotype mediates thermal preferences in a threatened freshwater fish, Notropis percobromus

Enders, E. C., Wall, A. J. & Svendsen, J. C., 2019, In : Journal of Thermal Biology. 84, p. 479-487

Research output: Contribution to journalJournal article – Annual report year: 2019Researchpeer-review

For ectothermic animals, ambient temperature strongly influences developmental growth rate and individual fitness. While many ectotherms live in environments that are spatially hetero-thermal, the coupling between behavioural phenotypes (e.g., shy or bold behaviour) and thermal preferences remains uncertain. Relative to shy counterparts, bolder phenotypes may exert higher preference for ambient temperatures that are closer to their thermal optimum, thereby accelerating development. In addition, ectotherms should select colder temperatures in low oxygen conditions (hypoxia) according to the oxygen- and capacity-limited thermal tolerance (OCLTT) hypothesis. Using wild caught carmine shiner (Notropis percobromus), this study examined thermoregulatory behaviour in individuals exhibiting consistent behavioural phenotypes along the shy-bold continuum and between ecologically relevant normal oxygen concentration (normoxic) and hypoxic treatments. Furthermore, the behaviour observed in the laboratory was compared to environmental data from the natal stream. Results demonstrated that individual shy-bold behavioural phenotype was consistent before and after a simulated aerial predator attack, indicating consistency of behaviour across situations. Individual preferred and avoidance temperatures varied substantially, but were unrelated to shy-bold behavioural phenotypes. In contrast, individual preferred and maximum avoidance temperatures were significantly reduced in hypoxia, consistent with the OCLTT hypothesis. These findings might indicate suppressed development rates in hypoxia, not only by the limited oxygen for aerobic metabolism, but also by the preference for colder water in hypoxia. Furthermore, the tolerated thermal ranges were reduced in hypoxia. Using test conditions confirmed by field data, our study demonstrates the strong influence of oxygen availability on thermoregulatory behaviours and preferences in aquatic environments.
Original languageEnglish
JournalJournal of Thermal Biology
Volume84
Pages (from-to)479-487
ISSN0306-4565
DOIs
Publication statusPublished - 2019

  PDF

Optimal Salmon Lice Treatment Threshold and Tragedy of the Commons in Salmon Farm Networks

År: 2019

Optimal Salmon Lice Treatment Threshold and Tragedy of the Commons in Salmon Farm Networks

Kragesteen, T. J., Simonsen, K., Visser, A. & Andersen, K. H., 2019, In : Aquaculture. 512, 734329.

Research output: Contribution to journalJournal article – Annual report year: 2019Researchpeer-review

The ectoparasite Lepeophtheirus salmonis has for decades plagued salmon aquaculture by decreasing profits and impacting wild salmon stocks. To protect migrating wild salmon stocks and avoid excessive cross-farm infections, authoritiesrequiretreatmentswhensealicelevelreachagiventhreshold. The treatment threshold is set to protect wild salmonid stocks but also to avoid costly lice infections on neighbouring farms. Here we make a bio-economic estimation of optimal treatment thresholds. We are particularly interested in identifying conflicts between the optimal threshold of for the entire system of farms and for the individual farmer. We show that isolated individual farms can maximize profit by operating with a high threshold, while the maximum profit for an entire network of farms occurs with a threshold about 0.1 gravid female lice/salmon. These findings substantiate the Norwegian policy of lowering the lice treatment threshold below 0.5 gravid lice/salmon. The results also demonstrate that too low a treatment threshold results in high treatment rates. The difference between the optimal treatment strategy of individual farmers and that for the total system demonstrates that management of salmon lice infections operates in a tragedy-of-the-commons environment, where individual farmers may have an incentive to disregard legislation at the expense of the others in the network. This means that strong enforcement is needed to achieve optimal management of salmon lice infections.
Original languageEnglish
Article number734329
JournalAquaculture
Volume512
ISSN0044-8486
DOIs
Publication statusPublished - 2019

  PDF

Challenges in quantifying, interpreting and predicting distributional shifts of marine species

År: 2019

Challenges in quantifying, interpreting and predicting distributional shifts of marine species

Marshall, C. T., Audzijonyte, A., Baudron, A., Champion, C., Fallon, N., Haynie, A. C., Haltuch, M., Townhill, B., van Denderen, P. D., Pecl, G., Pinnegar, J. K., Pinsky, M. L., Spencer, P., Stawitz, C. & Thorsen, J., 2019. 1 p.

Research output: Contribution to conferenceConference abstract for conference – Annual report year: 2019Research

Oceans are absorbing approximately 80% of the extra heat and 50% of additional CO2 trapped in the atmosphere and, as a result, have undergone rapid changes in temperature and acidity. The evidence for climate-driven global re-distribution of marine species is growing but often based on the distribution of fish species, many of which are mobile and able to rapidly shift their ranges in response to changing environmental conditions. Standardised surveys are commonly used for inferring spatial distribution, however, there are many examples of species moving beyond the bounds of a survey which then limits our understanding. Additionally, there are often non-climate factors that confound the interpretation of range shifts, e.g. fishing or habitat changes. Quantifying the magnitude and rates of distributional shifts is further complicated by the variety of metrics that are used to describe historical species distributions and then contemporary changes in these distributions. Accurately specifying both the suite of drivers underpinning range shifts and the magnitude of range shifts is essential due to the societal importance of marine species for food, local economies and future projections of commercial fish species. Here, based on a cross-comparison of methodological approaches from a range of globally important marine ecosystems, we make recommendations for appropriate approaches to the collection, analysis and interpretation of data describing the abundance and location of marine species.
Original languageEnglish
Publication date2019
Number of pages1
Publication statusPublished - 2019
EventSpecies on the Move - Kruger National Park, South Africa
Duration: 22 Jul 201926 Jul 2019
http://www.speciesonthemove.com/

Conference

ConferenceSpecies on the Move
LocationKruger National Park
CountrySouth Africa
Period22/07/201926/07/2019
Internet address