The thymus and T-cell ontogeny in ballan wrasse (Labrus bergylta) is nutritionally modelled

Marine fish larvae often experience high mortality unrelated to predation during early life stages, and farmed ballan wrasse (Labrus bergylta) is no exception. Knowing when the adaptive immune system is developed and fully functional, and how nutrition may modulate these processes is therefore of importance to establish effective prophylactic measures and will also extend the relatively limited knowledge on the immune system in lower vertebrates. The thymus anlage of ballan wrasse was found to be histologically visible for the first time at larval stage 3 (20–30 days post hatch, dph) and becomes lymphoid at stage 5 (50–60 dph) correlating with an increase of T-cell marker transcripts. At this stage, a clear zonation into a RAG1+ cortex and a RAG1- CD3ϵ+ medulla was distinguished, indicating that T-cell maturation processes in ballan wrasse are similar to other teleosts. The higher abundance of CD4-1+ compared to CD8β+ cells in the thymus together with the apparent lack of CD8β+ cells in gill, gut, and pharynx, where CD4-1+ cells were identified, indicates that helper T-cells have a more prominent role during larval development compared to cytotoxic T-cells. As ballan wrasse lacks a stomach but has an exceptionally high IgM expression in the hindgut, we hypothesize that helper T-cells are crucial for activation and recruitment of IgM+ B-cells and possibly other leukocytes to the gut during early development. Nutritional factors such as DHA/EPA, Zn and Se may lead to an earlier expression of certain T-cell markers as well as a larger size of the thymus, indicating an earlier onset of adaptive immunity. Including live feeds that supplies the larva with higher amounts of these nutrients can therefore be beneficial for ballan wrasse farming.publishedVersio

Glass eels (Anguilla anguilla) have a magnetic compass linked to the tidal cycle

The European eel (Anguilla anguilla) has one of the longest migrations in the animal kingdom. It crosses the Atlantic Ocean twice during its life history, migrating between the spawning area in the Sargasso Sea and Europe, where it is widely distributed. The leptocephalus larvae drift with the Gulf Stream and other currents for more than a year and metamorphose into glass eels when they arrive on the continental shelf and move toward coastal areas. The mechanisms underlying glass eel orientation toward the coast and into freshwater systems are poorly known. However, anguillid eels, including the glass eel life stage, have a geomagnetic sense, suggesting the possibility that they use Earth’s magnetic field to orient toward the coast. To test this hypothesis, we used a unique combination of laboratory tests and in situ behavioral observations conducted in a drifting circular arena. Most (98%) of the glass eels tested in the sea exhibited a preferred orientation that was related to the tidal cycle. Seventy-one percent of the same eels showed the same orientation during ebb tide when tested in the laboratory under a manipulated simulated magnetic field in the absence of any other cue. These results demonstrate that glass eels use a magnetic compass for orientation and suggest that this magnetic orientation system is linked to a circatidal rhythm.publishedVersio

Kunnskapstøtte og råd for regulering av fisket etter leppefisk i 2021

Fiskeridirektoratet har i en bestilling datert 07.09.2020 bedt Havforskningsinstituttet (HI) om kunnskapsstøtte for regulering av totaluttak, fartøykvoter, artsbegrensninger i fisket etter leppefisk. Det bes også om ny kunnskap om effekten av mindre innganger i teiner. Fiskeridirektoratet ønsker også kunnskap om hvordan fiske etter stamfisk av berggylte kan gjennomførers på en bærekraftig måte, kunnskap om oppdretternes behov for stamfisk, og kunnskapsstøtte knyttet til fangsten av stamfisk med hensyn på fangsttid, antall, redskaptype, røkting og bifangst.publishedVersio

Goldsinny wrasse (Ctenolabrus rupestris) have a sex-dependent magnetic compass for maintaining site fidelity

The goldsinny wrasse (Ctenolabrus rupestris) is a commercially important fish that inhabits coastal areas across the eastern Atlantic. This species moves from a shallow home territory along the coast into deeper waters in the autumn and winter and then returns to that same territory in the spring. Only male goldsinny wrasse exhibit strong territorial behavior, which may manifest as sexual differences in the ability or motivation to return to home territories. The orientation mechanism underlying the homing migration of goldsinny wrasse males and females is unknown. In this study, we hypothesized that goldsinny wrasse use the magnetic field of the Earth to follow a compass-based path toward their home territory. To test this hypothesis, we collected 50 adult goldsinny wrasse, approximately half males and half females, in a harbor in Austevoll, Norway. Fish were translocated to a magnetoreception laboratory situated north of the site of capture, in which the magnetic field was artificially rotated. In the laboratory, males oriented toward the magnetic south taking a mean direction of 201°, which is the approximate direction that they would have had to take to return to the site at which they were captured. Females oriented in random magnetic directions. There was no difference in swimming kinematics between males and females. These results show that male goldsinny wrasse have a magnetic compass that they could use to maintain site fidelity, an ability that could help them and other coastal fish undertake repeatable short-range migrations.publishedVersio

Early ontogeny of the lesser sandeel (Ammodytes marinus)

Background Lesser sandeel (Ammodytes marinus) is widely distributed in North Sea ecosystems. Sandeel acts as a critical trophic link between zooplankton and top predators (fish, mammals, sea birds). Because they live buried in the sand, sandeel may be directly affected by the rapid expansion of anthropogenic activities linked to their habitat on the sea bottom (e.g., hydrocarbon extraction, offshore renewable energy, and subsea mining). It is, therefore, important to understand the impact of cumulative environmental and anthropogenic stressors on this species. A detailed description of the ontogenetic timeline and developmental staging for this species is lacking limiting the possibilities for comparative developmental studies assessing, e.g., the impact of various environmental stressors. Results A detailed description of the morphological development of lesser sandeel and their developmental trajectory, obtained through visual observations and microscopic techniques, is presented. Methods for gamete stripping and intensive culture of the early life stages are also provided. Conclusion This work provides a basis for future research to understand the effect of cumulative environmental and anthropogenic stressors on development in the early life stages of lesser sandeel.publishedVersio

Program rensefisk: Adferd og artssamspill i laksemerder

Rensefisk er lakseoppdretternes viktigste, ikke-medikamentelle hjelpemiddel i kampen mot lakselus. Det brukes ofte flere arter rensefisk i kombinasjon, men det er lite kjent om adferd og artssamspill kan påvirke effekten av lusebeiting i merd. I dette forsøket ble kombinasjoner av rensefiskartene berggylt, bergnebb, grønngylt og rognkjeks testet i kombinasjoner. Adferd ble undersøkt ved bruk av kamera og antenner til posisjonsregistrering for PIT-merket rensefisk. Lus ble talt i alle merder ukentlig. Forsøket ble avsluttet etter tre uker pga. sykdomsutbrudd på laksen, men vi kunne likevel se tydelig effekt av rensefisken på antall lus sammenlignet med kontrollgrupper. Kombinasjoner med berggylt + bergnebb og berggylt + grønngylt var mest effektive for å redusere lusetallene, men leppefiskene fungerte også bra når de ikke var i kombinasjon med andre. Rognkjeks gav mindre effekt i kombinasjoner med leppefisk og fungerte dårlig når den ble brukt som eneste rensefiskarten. Dette kan relateres til at vi observerte tydelige forskjeller i dybdeatferd; leppefiskene benyttet et større dybdespenn, mens rognkjeksen ble hovedsakelig registrert i overflaten. Dette kan skyldes høy vanntemperatur og mye maneter i sjøen som rognkjeksen ble observert beitende på. Det er derfor sannsynlig at rognkjeksen har en annen dybdepreferanse og bedre effekt på lusetall under andre miljøbetingelser. Selv om forsøkene demonstrerer at kombinasjoner av ulike leppefiskarter tyder på å gi en god effekt og fungerer fint sammen, er det fortsatt behov for bedre forståelse av sesongmessige variasjoner i adferd og lusebeiting for å få en optimal utnyttelse av rensefisk og en rett kombinasjon av artene gjennom hele året. AGD-utbrudd på laksen i merdforsøkene gav utfordringer angående rensefiskenes toleranse for de vanlige behandlingene som blir brukt mot AGD hos laks, ferskvann og hydrogenperoksid. Hovedfunnene i forsøkene med de to behandlingsmetodene på rognkjeks, berggylt, grønngylt og bergnebb var at verken berggylt, bergnebb eller grønngylt kan settes direkte i ferskvann, men de tålte 2 timers opphold i tilnærmet ferskvann ved gradvis tilvenning til ferskvann. Alle de undersøkte artene klarte 20 minutters opphold i hydrogenperoksidløsning (1500 ppm).Cleanerfish program: Behaviour and species interactions in the seacages.Program rensefisk: Adferd og artssamspill i laksemerderpublishedVersio

Regulation of gene expression is associated with tolerance of the Arctic copepod Calanus glacialis to CO2-acidified sea water

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Movement patterns of temperate wrasses (Labridae) within a small marine protected area

e Institute of Marine Research (Project 15638-01publishedVersio

Program rensefisk: Kunstig lys og rensefisk - Sluttrapport FHF prosjekt 901146

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Seleksjon i leppefiskredskap - FHF-prosjekt 901253, sluttrapport

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