Year of grant:
Náttúra og náttúrutilfeingi
Livilíkindi hjá toska- og hýsuyngli á føroyska landgrunninum.
Grant from the FRC in DKK:
Elucidating the early life history of Faroe Plateau cod and Faroe haddock
Cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) are main demersal fish species on the Faroe Shelf which have always been key fish species for the Faroese community and economy. The stocks show large fluctuations in year class strengths which has severe economical and sociological consequences. Although there are many bottlenecks affecting the final year class strengths of fish, the early life phase of the individuals (i.e. larval and pelagic juvenile stages) is generally considered to be essential for successful further development. During the pelagic phase, the fishes undergo a period of rapid development with considerable changes in size, structure, physiology and behaviour. Survival of eggs and larvae are mainly dependant on drift and distribution, feeding and growth conditions, and extent of predation. Monitoring of pelagic 0-group fish on the Faroe Plateau in late June from 1974 until present has revealed large variations in cod and haddock abundance and sizes. Interestingly, the abundance and individual sizes to a large extent seem to co-vary between years, indicating simultaneous environmental influences on mortality and individual sizes. The aim of this project is to investigate the life history of cod and haddock larvae and pelagic juveniles and to relate this to oceanographical parameters and feeding conditions. The research material is based on field samplings and in situ measurements on the Faroe Shelf on two annual cruises, in late April and late June respectively. The April cruise is placed at a critical time in spring (late pre-bloom and early bloom phase), studying the match-mismatch between spring bloom development, subsequent zooplankton reproduction, and occurrence of first-feeding fish larvae. The June cruise is placed close towards the end of the pelagic phase of the juveniles. Historical data and stored samples of cod and haddock larvae and juveniles will be analysed, together with environmental variables. This information may reveal how growth and survival of cod and haddock during their pelagic phase is affected by the dynamic environmental conditions on the Faroe Shelf. Since abundance of 0-group cod and haddock is a relatively good predictor for subsequent recruitment to the fish stocks, such information will be valuable in advice and management of sustainable exploitation of these important fish species in the future.
The project has increased the understanding of the early life history of Faroe Plateau cod and haddock. From analysis of historical samples from late April 1997-2016 it has been shown that phytoplankton biomass stimulates abundance of small sized (neritic) zooplankton, which are a main food item for cod and haddock larvae. Cod and haddock juveniles co-vary in mean length and abundance and the variation is closely related to the primary (phytoplankton) and secondary (zooplankton) production. Mean length and abundance of the juveniles is highest when the primary production is high and vice versa. Otolith analysis have revealed that the variation in mean size of the juveniles is both a result of higher mean age and better growth during productive years compared with years with poor production.
Scientific articles, books, thesis etc.
Jacobsen S, Gaard E, Larsen KMH, Eliasen S, Hátún H (2018) Temporal and spatial variability of zooplankton on the Faroe shelf in spring 1997-2016. Journal of Marine Systems 177: 28-38. DOI: 10.1016/J.JMARSYS.2017.08.004
Other results, such as unpublished articles, patents, computer systems, original models and new procedures
Jacobsen et al. (in prep) Covariability in growth and survival of Faroe Plateau cod and haddock: the environmental link. Manuscript in preparation.
Jacobsen et al. (in prep) Feeding ecology of pelagic Faroe Plateau cod 1998-2005. Manuscript in preparation.
Publications outside the scientific community, i.e. lectures, periodicals, articles in newspapers, television and radio
Sólvá Jacobsen: “Zooplankton community structure and size spectra linked to phytoplankton and hydrographic features on the Faroe Shelf in spring”. Presentation given at the ICES/PICES 6th zooplankton production symposium, Bergen, Norway, 10 May 2016.
Sólvá Jacobsen: ”Æti og yngul á føroyska landgrunninum”. Presentations given at Bank Nordik and Fiskivinnuskúlin in Vestmanna, Faroe Islands, 28 and 29 September 2016, respectively.
Højgaard DP, Jacosben S (2017) Toskayngul etin upp innanífrá av rundormi. Sjóvarmál 2017, s.14-15.
Storage and access rights til collected data
All data used in this work is collected and saved in databases within the Faroe Marine Research Institute. The rights to collected data belong to the Faroese government/people.