Spatial patterns of the temporal dynamics of three gadoid species along the Norwegian Skagerrak coast

Journal home page: http://www.int-res.com/journals/meps/Time series from an extensive research survey of juveniles of cod Gadus morhua, pollack Pollachius pollachius and whiting Merlangius merlangus sampled from 1919 to 1994 at 38 stations along the Norwegian Skagerrak coast were investigated. Spatial and temporal analyses were performed to study the spatial pattern of the temporal dynamics of the 3 fish species. Spatially consistent variations were detected in abundance, year-to-year fluctuation as well as in periodicity. The spatial heterogeneity occurred at a mesoscale (differences between fjords) and at a local scale (differences between stations within a fjord) for the 3 gadoids. However, the magnitude of the spatial heterogeneity differed between species. Cod and whiting, which were more abundant in sheltered areas, showed higher spatial variability than pollack, which was more abundant in exposed locations. In this way, the spatial pattern of abundance appeared to be linked to the scale of variability of the species. All 3 species exhibit periodic fluctuations of 2 to 2.5 yr in their optimal habitats, which probably resulted from intrinsic interactions in age-structured populations, such as density-dependent competition and cannibalism. In addition, all the species exhibited long-term trends possibly due to extrinsic forces, such as environmental changes or anthropogenic influences

Overvåking av forurensningsituasjonen i indre Oslofjord 2003

Årsliste 2004Rapporten omhandler resultatene fra undersøkelser foretatt i indre Oslofjord hovedsakelig i 2003. Dypvannsfornyelsen var god i Vestfjorden, men beskjeden i Bunnefjorden. Oksygenforholdene har blitt bedre i Vestfjorden siden begynnelsen av 1980-tallet, mens det ikke har skjedd noen forandring i Bunnefjorden. Det ble observert reker i Lysakerfjorden høsten 2003 (men ikke i 2002), noe som skyldtes bedre oksygenforhold. Rensetiltakene har forandret fjordens vannkjemi, med klart avtakende konsentrasjoner av fosfor mellom overflatelaget og 50 meters dyp, samt i Vestfjordens dypere vannmasser. I Bunnefjordens dypvann har det ikke skjedd noen forandring. Nitrogenrensingen har foreløpig ikke gitt signifikant utslag i observasjonene. Resultatene av strandnottrekk viser en økt fangst av kutling i Vestfjorden og Bunnefjorden, men antall arter viser ingen økning. Undersøkelser av miljøgifters effekt på fisk innsamlet i 2002 viste påvirkning av fra PAH/PCB/dioksin samt bly i torsk og skrubbe, sammenlignet med fisk fra ytre Oslofjord. Det var dog ikke noen effekt av østrogenliknende stoffer.Fagrådet for vann- og avløpsteknisk samarbeid i indre Oslofjor

Final Report of the Fifth Meeting of Scientific Experts on Fish Stocks in the Central Arctic Ocean

This report provides a summary of the 5th meeting of scientific experts on Fish Stocks in the Central Arctic Ocean (FiSCAO) on October 24‐26, 2017, in Ottawa, Canada. At the request of the 10 parties negotiating on an agreement to prevent unregulated commercial fishing in the High Seas portion of the Central Arctic Ocean (CAO), participants of the 5th FiSCAO meeting were tasked with addressing four Terms of Reference, summarized below: ToR 1. Design a 1‐3 year long mapping program. ToR 2. Design a monitoring program. ToR 3. Identify human, financial, vessel/equipment resources needed for mapping and monitoring. ToR 4. Develop data collection, sharing, and hosting protocols that outline the details of what and how data shall be collected, shared, and hosted for consideration by the Parties. The 5th FiSCAO meeting included scientific representatives from seven states including Canada, the People's Republic of China, the European Union, Iceland, the Republic of Korea, the Kingdom of Norway and the United States of America. The meeting also included representatives from the International Council for the Exploration of the Sea (ICES), the North Pacific Marine Science Organization (PICES) and the Arctic Council’s Protection of the Arctic Marine Environment (PAME) and Conservation of Arctic Flora and Fauna (CAFF) working groups. The report summarizes the elements for collecting baseline data (i.e., a mapping program) in the high seas CAO to achieve the goals of documenting species distributions, relative abundances and key ecosystem parameters (ToR 1). The mapping program describes the priority areas to sample, the types of data to collect and possible data collection approaches to employ. Participants emphasized that existing planned surveys are very limited, and that significant dedicated resources will be required to implement the mapping program. The report outlines a strategy for monitoring indicators of fish stocks and ecosystem components (ToR 2). The report includes a list of existing monitoring programs and a prioritized list of indicators to detect environmental change in the high seas CAO. Further refinement of a monitoring program will use information from the mapping program (ToR 1). Participants emphasized the need to begin monitoring as soon as possible and that additional research is required to operationalize monitoring indicators. The report summarizes the preliminary cost estimates (ToR 3) to implement a mapping program to collect data in the high seas portion of the CAO using a vessel of opportunity and in the Pacific Gateway region of the CAO using an independently‐organized survey. Cost implications for the monitoring program and other scientific activities are also listed (e.g., data analysis, data management). The report includes a draft data sharing policy as the foundation for a future data sharing protocol, including the technical specifications for data sharing (ToR 4). The development of the data sharing protocol will require negotiation and legal review among the participating states. A data management and data sharing pilot study on a CAO fish database is suggested to test a framework

Density‐ and size‐dependent mortality in fish early life stages

The importance of survival and growth variations early in life for population dynamics depends on the degrees of compensatory density dependence and size dependence in survival at later life stages. Quantifying density‐ and size‐dependent mortality at different juvenile stages is therefore important to understand and potentially predict the recruitment to the population. We applied a statistical state‐space modelling approach to analyse time series of abundance and mean body size of larval and juvenile fish. The focus was to identify the importance of abundance and body size for growth and survival through successive larval and juvenile age intervals, and to quantify how the dynamics propagate through the early life to influence recruitment. We thus identified both relevant ages and mechanisms (i.e. density dependence and size dependence in survival and growth) linking recruitment variability to early life dynamics. The analysis was conducted on six economically and ecologically important fish populations from cold temperate and sub‐arctic marine ecosystems. Our results underscore the importance of size for survival early in life. The comparative analysis suggests that size‐dependent mortality and density‐dependent growth frequently occur at a transition from pelagic to demersal habitats, which may be linked to competition for suitable habitat. The generality of this hypothesis warrants testing in future research.publishedVersio

Proxy Measures of Fitness Suggest Coastal Fish Farms Can Act as Population Sources and Not Ecological Traps for Wild Gadoid Fish

Background: Ecological traps form when artificial structures are added to natural habitats and induce mismatches between habitat preferences and fitness consequences. Their existence in terrestrial systems has been documented, yet little evidence suggests they occur in marine environments. Coastal fish farms are widespread artificial structures in coastal ecosystems and are highly attractive to wild fish. Methodology/Principal Findings: To investigate if coastal salmon farms act as ecological traps for wild Atlantic cod (Gadus morhua) and saithe (Pollachius virens), we compared proxy measures of fitness between farm-associated fish and control fish caught distant from farms in nine locations throughout coastal Norway, the largest coastal fish farming industry in the world. Farms modified wild fish diets in both quality and quantity, thereby providing farm-associated wild fish with a strong trophic subsidy. This translated to greater somatic (saithe: 1.06–1.12 times; cod: 1.06–1.11 times) and liver condition indices (saithe: 1.4–1.8 times; cod: 2.0–2.8 times) than control fish caught distant from farms. Parasite loads of farm-associated wild fish were modified from control fish, with increased external and decreased internal parasites, however the strong effect of the trophic subsidy overrode any effects of altered loads upon condition. Conclusions and Significance: Proxy measures of fitness provided no evidence that salmon farms function as ecological traps for wild fish. We suggest fish farms may act as population sources for wild fish, provided they are protected from fishing while resident at farms to allow their increased condition to manifest as greater reproductive output.Funding was provided by the Norwegian Research Council Havet og kysten program to the CoastACE project (no: 173384)

Biomass of Scyphozoan Jellyfish, and Its Spatial Association with 0-Group Fish in the Barents Sea

An 0-group fish survey is conducted annually in the Barents Sea in order to estimate fish population abundance. Data on jellyfish by-catch have been recorded since 1980, although this dataset has never been analysed. In recent years, however, the ecological importance of jellyfish medusae has become widely recognized. In this paper the biomass of jellyfish (medusae) in 0–60 m depths is calculated for the period 1980–2010. During this period the climate changed from cold to warm, and changes in zooplankton and fish distribution and abundance were observed. This paper discusses the less well known ecosystem component; jellyfish medusae within the Phylum Cnidaria, and their spatial and temporal variation. The long term average was ca. 9×108 kg, with some years showing biomasses in excess of 5×109 kg. The biomasses were low during 1980s, increased during 1990s, and were highest in early 2000s with a subsequent decline. The bulk of the jellyfish were observed in the central parts of the Barents Sea, which is a core area for most 0-group fishes. Jellyfish were associated with haddock in the western area, with haddock and herring in the central and coastal area, and with capelin in the northern area of the Barents Sea. The jellyfish were present in the temperature interval 1°C<T<10°C, with peak densities at ca. 5.5°C, and the greatest proportion of the jellyfish occurring between 4.0–7.0°C. It seems that the ongoing warming trend may be favourable for Barents Sea jellyfish medusae; however their biomass has showed a recent moderate decline during years with record high temperatures in the Barents Sea. Jellyfish are undoubtedly an important component of the Barents Sea ecosystem, and the data presented here represent the best summary of jellyfish biomass and distribution yet published for the region

Overvåking av forurensningsituasjonen i indre Oslofjord i 1999

Vannkvaliteten i fjordens overflatelag sommeren 1999 var noe dårligere enn i 1998, men klart bedre enn i 1994/95, hvor den var påvirket av ekstra store overløp og storflom. Juni 1999 var relativt kald og nedbørrik. Intensive regnskyll ga flom i elvene og overløp til renseanleggene ble tatt i bruk. Høyere næringssaltkonsentrasjon, større planteplanktonbiomasse og dårligere siktedyp preget situasjonen i fjordens overflatevann. Det ble utferdet advarsel mot bading på utvalgte badeplasser i noen dager. Selv om juni var relativt dårlig ble forholdene i juli bedre og i august bra. Sammenlignet med eldre observasjoner ble den positive utviklingen i fjordens vannkvalitet bekreftet. bekreftet. Vinteren 1999 var igjen mild og de klimatiske forhold mindre gunstige for en større dypvannsfornyelse. Det var ikke noen dypvannsfornyelse i Bunnefjorden som hadde hydrogensulfidholdig dypvann hele året (ca. 60 meters dyp til bunn). Det ble også lave oksygenkonsentrasjoner i Lysakerfjorden og Vestfjorden høsten 1999. I samband med en vannutskiftning i oktober ble det rapportert fiskedød enkelte steder i Vestfjorden hos fisk fanget i nett og ruser. Selv om oksygensituasjonen 1999 var mindre bra enn tidligere, er det fortsatt en positiv tendens i Vestfjordens dypvann (1973-99), og ikke noen klar negativ tendens i Bunnefjordens dypvann. De mindre gode oksygenforholdene sammenfaller i tid med en nedgang i fangst av reker og med enkelte unntak generelt noe dårligere fiske i fjorden. Fangsten av O-gruppe torsk i grunntvannsområdene i Vestfjorden var dårligere enn i 1998, noe som skyldes en generelt svak årsklasse langs Skagerrakkysten. Det er gjort små, men akseptable fangster i på gjenopprettede stasjoner i Bunnefjorden, hvor tilstanden tidligere var så dårlig at stasjonene ble nedlagt i 1964

An integrated database for marine research

In 1992 an integrated model for marine research data was developed at the Institute of Marine Research. Traditionally, the marine research disciplines collect data from their own fields, normally used in a limited context. In many research programs there is a strong need to crossrelate data from various sources. To accomplish this it is essential to establish an integrated database, with a uniform data representation and a structure that is flexible enough to represent all kinds of marine data. A centralized database increases the availability, avoids redundancy and enforces access control and protection against loss of data. The model is based on a generic data structure where "platform", "operation", "object" and "measurement" are central entities. In an operation (e.g. trawling) on a platform (e.g. ship), series of measurements (e.g. lengths) of different objects (e.g. fish) are gathered. Data can be classified according to different systems (e.g. taxonomy, regions and methods). The database is implemented in the Ingres relational database system running on HP9000/755 computers with Unix operating system and connected to the institute's local network and Internet. Tests have been carried out to evaluate functionality and performance. While the test results are acceptable, minor immediate modifications are needed. The database will be subject to further development in the future. Currently, work is in progress on data quality assurance, inserting data into the database and adapting software applications. The database is planned to be in regular use at the end of 1993