Hindrer Nordhordlandsbroen smoltens utvandring?

Den dramatiske nedgangen av laksebestanden i Vosso har brakt flere institusjoner sammen for å undersøke betydningen av menneskeskapte forhold for denne utviklingen. De siste årene har søkelyset i hovedsak vært rettet mot lakselus og andre faktorer som kan påvirke smoltutvandringen. Havforskningsinstituttet har undersøkt hvilken betydning Norhordlandsbroen kan ha

Dokumentation og datering af teglmurværk. Om iagttagelser og deres samspil i bygningsarkæologien

Brick masonry, its documentation and datingBy Jens Christian HolstBrick masonry is a specific category of architectural tradition Northern Germany and the Scandinavian countries have in common. It demands specific performances of documentation, dating and interpretation. The article deals with those contributions, a building archaeologist her- or himself might perform, and those better done by an expert. It is a rough sketch only, written from an empirical point of view, illustrated by a few examples. Steps of precision and accuracy in graphic resembling of a brick wall are named, what is achieved by them or not, and to which extent the competence of external surveying techniques is needed. Photographic and written documentation are merely quoted, the necessity of stratigraphic analysis is emphasized resulting from feature mapping and to be recorded by age mapping. The age layer model used, scaled into epochs, phases and stages, needs to be harmonized with the results of an archaeologist or a conservator dealing with the same building. Scientific methods to gain absolute datings out of the building material are shortly discussed. The architectural archaeologist´s own contribution is recognized in compiling chronologies of single and comprehensive material features, of brickmakers` as well as masons` techniques, to narrow down a possible date by comparison. Evaluation of written sources, to which precise dating is the key performance, cannot be discussed here. In the end possibilities occur to visualize historical stages of the architectural development, based on stratigraphic mapping. Clearing up the many stages of a building´s history until it became the one we know is seen as the main future field for our profession – not to be solved without help from many a friend

Numerical domination and herring migrations

There is accumulating evidence in favour of the hypothesis that herring migrations are influenced by social learning. The “adopted-migrant hypothesis” postulates that recruit spawning herring learn migration patterns by schooling with older individuals. However, this learning can be interrupted if the stock is unstable or if there are lack of overlap between recruits and the adult stock. There have been five reported changes in the location of the wintering area of Norwegian spring spawning (NSS) herring during the last 50 years. These changes co-occur with the recruitment of relatively strong year classes to the spawning stock. Simulations of schools containing naïve and experienced fish have shown that when abundant enough, naïve individuals repel guidance from a minority of experienced individuals. This process is referred to as numerical domination. We argue that numerical domination obstruct social learning from adults to recruits and plays a key role in establishing new wintering areas in NSS herring

Hindrer Nordhordlandsbroen smoltens utvandring?

Den dramatiske nedgangen av laksebestanden i Vosso har brakt flere institusjoner sammen for å undersøke betydningen av menneskeskapte forhold for denne utviklingen. De siste årene har søkelyset i hovedsak vært rettet mot lakselus og andre faktorer som kan påvirke smoltutvandringen. Havforskningsinstituttet har undersøkt hvilken betydning Norhordlandsbroen kan ha

Capture and handling of fish for electronic tagging - a review and a new non-intrusive capture method.

While tagging procedures are described in details the capture and handling of experimental fish prior to tagging is not given the same attention in most papers. However, traumas that originate from the capture and handling process may for a varying penid of time iradluenca: the post-release behaviour of the animals studied with Smart-or other electronic tags introducing errors when interpreting the data collected. With emphasis on Atlantic species, the paper gives an overview of capture and handling methods reported in electronic tagging experiments, and where relevant, references are made also to methods used to capture and transport fish for aquarium or other live holding purposes. The advantages and disadvantages of different handling methods are discussed, and a promising new &awl-method for c individuals of delicate species is summarised

Behaviour of Atlantic salmon (Salmo salar L.) recorded by data storage tags in the NE Atlantic – implications for interception by pelagic trawls

In a project carried out in the Nordic Seas (Northeast Atlantic) in 2002 - 2004, 413 Atlantic salmon (Salmo salar L.) were tagged with data storage tags (DST) either logging temperature and depth (StarOddi, Milli) or just temperature (Dallas semiconductor, iButton). The main aims were to study various marine life history traits of salmon, such as winter habitats, diurnal patterns of vertical migration, feeding activities. Another aim was to collect salmon behaviour data with relevance for issues related to by-catch of salmon in pelagic fisheries. In this paper we focus on possible implications of the diurnal depth distribution of salmon in relation to catchability of salmon in sampling trawls versus commercial fisheries. Five DSTs were returned from fishermen. Four of these were Milli-tags and are used in this presentation. Time from release to capture ranged from 48 - 128 days. The DSTs logged data at alternating intervals of 1, 5, 30, 60 and 120 min. almost 45000 recordings were retrieved. The data records were grouped in different phases: post-release; oceanic feeding & migration; coastal migration; estuarine migration; in-river phase. Salmon stay in the upper 5 m for 60% of the time during the oceanic phase, making deep dives (280 m) in between. The proportion of time the salmon stay at the surface (<2 m) decreases from 5.5 to 2.5% between 9 and 17 h

Experiences with recapture of escaped farmed salmon in Norway

Monitoring and statistics of the amount of escaped salmonids in the sea in Norway is limited. Recapture is encauraged in several counties by allowing a sea fishery targeting escapees from 1. October to 28. February. Low recapture rates have generally been obtained following large escape events. Telemetry studies of the post-release behaviour of cultured salmon in the Hardanger Fiord have shown 1)that the salmon dive frequently the first days after escape, 2) but then move close to the surface the next weeks. and 3) that they spread rapidly. The recapture effort should preferably cover a large area for at least 4-5 weeks and not be limited to the vicinity of the fish farm. NORSK SAMMENDRAG: Overvåking og statistikk over mengden rømt oppdrettslaks i sjøen i Norge er mangelfull. Gjenfangst av rømt fisk er i flere fylker organisert ved å tillate et generelt fiske etter rømt fisk fra 1. oktober til 28. februar.Gjenfangstfiske etter større rømmingsepisoder har generelt gitt lave gjenfangster. Pågående telemetristudier av adferden tii simulert rømt laks i Hardangerfjorden har vist 1) at laksen dykker etter rømming, 2) at den trekker opp mot overflaten etter noen dager, men 3)at den da allerede har spredd seg utover et stort område. Gjenfangst bør ikke begrenses til rømmingslokaliteten, men spres over et stort areal og kan opprettholdes i minst 4-5 uker

Cod, haddock, saithe, herring, and capelin in the Barents Sea and adjacent waters: a review of the biological value of the area

Cod, haddock, saithe, herring, and capelin are the most important fish species in the Barents Sea and adjacent waters. Ecosystem-based management requires species-specific knowledge of the biological value and vulnerability throughout their life history and distributional range. For each of the five species and four annual quarters, the spawning (egg) areas, nursery areas for larvae and juveniles, and feeding grounds for adults are described and mapped. Areas of eggs (spawning) and larvae were the most important because these are the life stages when fish are most vulnerable to anthropogenic impact. The greatest overlap of spawning areas was from Røstbanken in the south to the Varanger Peninsula in the northeast, and overlap of larval distribution was more extensive