Artsfordeling og bestandsstørrelser for de ulike artene av leppefisk i de undersøkte områdene

Sammensetningen av leppefiskarter er signifikant forskjellige mellom alle lokalitetene som ble undersøkt, også mellom lokaliteter som ligger nær hverandre. De dominerende artene var grønngylt og bergnebb alle steder foruten Smøla som bare hadde bergnebb i fangstene. Grønngylt hadde større gjenfangstfrekvens enn bergnebb på alle lokalitetene dette ble målt foruten de to Tysnes – lokalitetene. Der var det ingen signifikante forskjeller mellom disse to artene

Alder og vekst hos de ulike artene av leppefisk i utbredelsesområdet

De ulike leppefiskartene har forskjellige livshistorier. Bergnebb vokser seint, men ganske jevnt gjennom livet. De vil ha en alder på 4-5 år før de når fangbar størrelse på 11 cm som var instestørrelsen i 2012. Grønngylt vokser raskt til å begynne med, men veksten flater ut senere i livet. Grønngylt har stor variasjon i vekst mellom individer, og en kan finne 2-åringer som er 6 cm og som er 16 cm i samme område

Analysis of European eel (Anguilla anguilla) time series in Norway

The European eel Anguilla anguilla is found all over Europe and in extremely diverse habitats both in freshwater and saltwater systems. Its life strategy also varies, from catadromous to a strictly marine life cycle. Eels are undergoing a severe decline in almost every European country, as concluded by the ICES Working Group on Eel since 1998. However all indicators are based on catadromous eels having spent some part of their life cycle in freshwater. Because most of the factors (mostly anthropogenic) would only affect catadromous eels, it can be questioned whether the subpopulation of eels that remain in marine waters are undergoing a similar decline. The Skagerrak beach seine surveys, initiated and carried out by the Institute of Marine Research in Flødevigen since 1904, constitute the only potential data on such eels. It is also the longest fishery independent time series on Anguilla anguilla. Here, we analyzed these data, as well as other time series for recruitment and escapement of eels in freshwater from the river Imsa in Norway (data collected by the Norwegian Institute for Nature Research. Results showed that trends calculated on all the time series have been decreasing. The collapse in elvers (freshwater recruitment) in the river Imsa began in 1981. This is consistent with declines in other European countries: glass eels in the Netherlands began to decline in 1982. Silver eel escapement from the river Imsa also showed a significant decline 7 years after. This delay corresponds to the mean age of silver eels estimated in previous studies. A collapse in eel numbers was also observed in the Skagerrak time series but beginning later, in 1997. No eels were caught in 2007. This data series was also significantly and negatively correlated with surface sea temperatures in the Sargasso Sea when lags of 7 and 11 years were applied. This suggests that a temperature increase at the eel's spawning ground negatively affects the recruitment of larvae, possibly through a reduction in primary production

Analyse av bestandsutviklingen til ål i Norge – i sjø og ferskvann

The European eel Anguilla anguilla is found all over Europe and in extremely diverse habitats both in freshwater and saltwater systems. Its life strategy also varies, from catadromous to a strictly marine life cycle. Eels are undergoing a severe decline in almost every European country, as concluded by the ICES Working Group on Eel since 1998. However all indicators are based on catadromous eels having spent some part of their life cycle in freshwater. Because most of the factors (mostly anthropogenic) would only affect catadromous eels, it can be questioned whether the subpopulation of eels that remain in marine waters are undergoing a similar decline. The Skagerrak beach seine surveys, initiated and carried out by the Institute of Marine Research in Flødevigen since 1904, constitute the only potential data on such eels. It is also the longest fishery independent time series on Anguilla anguilla. Here, we analyzed these data, as well as other time series for recruitment and escapement of eels in freshwater from the river Imsa in Norway (data collected by the Norwegian Institute for Nature Research. Results showed that trends calculated on all the time series have been decreasing. The collapse in elvers (freshwater recruitment) in the river Imsa began in 1981. This is consistent with declines in other European countries: glass eels in the Netherlands began to decline in 1982. Silver eel escapement from the river Imsa also showed a significant decline 7 years after. This delay corresponds to the mean age of silver eels estimated in previous studies. A collapse in eel numbers was also observed in the Skagerrak time series but beginning later, in 1997. No eels were caught in 2007. This data series was also significantly and negatively correlated with surface sea temperatures in the Sargasso Sea when lags of 7 and 11 years were applied. This suggests that a temperature increase at the eel's spawning ground negatively affects the recruitment of larvae, possibly through a reduction in primary production

Magnetic Compass Orientation in the European Eel

European eel migrate from freshwater or coastal habitats throughout Europe to their spawning grounds in the Sargasso Sea. However, their route (~ 6000 km) and orientation mechanisms are unknown. Several attempts have been made to prove the existence of magnetoreception in Anguilla sp., but none of these studies have demonstrated magnetic compass orientation in earth-strength magnetic field intensities. We tested eels in four altered magnetic field conditions where magnetic North was set at geographic North, South, East, or West. Eels oriented in a manner that was related to the tank in which they were housed before the test. At lower temperature (under 12uC), their orientation relative to magnetic North corresponded to the direction of their displacement from the holding tank. At higher temperatures (12–17uC), eels showed bimodal orientation along an axis perpendicular to the axis of their displacement. These temperature-related shifts in orientation may be linked to the changes in behavior that occur between the warm season (during which eels are foraging) and the colder fall and winter (during which eels undertake their migrations). These observations support the conclusion that 1. eels have a magnetic compass, and 2. they use this sense to orient in a direction that they have registered moments before they are displaced. The adaptive advantage of having a magnetic compass and learning the direction in which they have been displaced becomes clear when set in the context of the eel’s seaward migration. For example, if their migration is halted or blocked, as it is the case when environmental conditions become unfavorable or when they encounter a barrier, eels would be able to resume their movements along their old bearing when conditions become favorable again or when they pass by the barrier

El azufre en suelos de los Llanos Orientales de Colombia

This study is the first step investigating a new food chain, using Zophobas morio as a potential “vehicle” to transport amino acids (AA) from Norwegian kelp (Ascophyllum nodosum) into the insect body. Additionally, suitability of Z. morio as a dietary protein substitute for fishmeal (FM) in aquaculture feeds, was evaluated. Proximate composition (dry matter, ash, protein, fat and energy) and complete (free + hydrolysed + tryptophan) AA profiles were determined for Z. morio fed with kelp granulate or oat meal. Using principle component analysis we identified similarities and differences in essential AA between diets and Z. morio fed with these diets. AA scores were calculated to evaluate protein quality of Z. morio. Results showed a slight enrichment in several essential AA for Z. morio fed kelp granulate. Protein level of Z. morio in this study fell within the ranges of protein requirements for fish. All essential AA for fish were present in Z. morio. Based on AA scores it was concluded that methionine would be first limiting. Overall, protein levels and AA profiles showed that Z. morio fed with kelp granulate can be seen as an interesting candidate to replace FM in aquatic diets

Relations entre l'activité locomotrice, les facteurs environnementaux et leur synchronisation avec la migration pour la ponte chez l'anguille européenne, Anguilla anguilla

[Departement_IRSTEA]MA [TR1_IRSTEA]QSA / DYMECOInternational audienceAt the onset of sexual maturation, European eels Anguilla anguilla exhibit high locomotor activity which may correspond to migratory restlessness. We measured activity of captive eels and determined whether it correlated with downstream runs of silver eels as well as changes in environmental factors. Groups of eels at different stages of the silvering process (yellow to silver stage) were tagged and placed in separate tanks supplied with either river or tap water. Activity was measured by means of a flat-board antenna placed vertically in the middle of the tank at the surface of the water.Wild migrating silver eels were caught in the nearby river. Activity of eels in the river water tanks increased 1 to 2 days before downstream migrating eels were caught in the trap, and concurrently with a rise in turbidity and a decrease in conductivity. Activity of eels in the tap water tank showed a different pattern, which did not correspond to downstream runs. A peak in activity corresponded to a drop in tap water pH. It is concluded that eels do show periods of high locomotor activity at the onset of migration and this could be used to predict downstream migration. Movements are triggered by changes in water composition (as opposed to changes in discharge, atmospheric pressure and lunar cycle) measured using turbidity and/or conductivity as proxies. If eels are able to detect such small changes in water conductivity (80 μS cm−1), they may use it to find their way to the estuary.Au tout début de leur maturation sexuelle, les anguilles européennes, Anguilla anguilla, présentent une forte agitation qui pourrait correspondre aux premiers mouvements migratoires. L'objectif de cette étude est de déterminer si ces périodes d'activité correspondent aux pics de dévalaison d'anguilles argentées en rivière et si elles peuvent être associées aux variations de certains facteurs environnementaux. Plusieurs lots d'anguilles (stades jaune et argenté) ont été marqués et placés dans des bassins séparés, alimentés soit en eau de la rivière, soit en eau de ville. L'activité des anguilles est mesurée par l'intermédiaire d'une antenne de détection située verticalement au milieu du bassin, près de la surface. Un piège de dévalaison permet de capturer les anguilles en migration dans la rivière. L'activité des anguilles en bassins alimentés par la rivière ont une activité accrue 1 à 2 jours avant la capture d'anguilles de dévalaison dans le piège et ces périodes correspondent à une augmentation de la turbidité et à une diminution de la conductivité. Les individus dans le bassin eau de ville présentent un comportement différent et l'unique pic d'activité correspond à une baisse du pH. En conclusion, les anguilles montrent bien des périodes d'activité intense au moment de la dévalaison et ceci pourrait être utilisé pour prévoir les pics de dévalaison. Les mouvements sont déclenchés par des variations dans la composition de l'eau de la rivière (par opposition à des variations de débit, de pression atmosphérique et au cycle lunaire) visibles à travers les changements de turbidité et/ou de conductivité. Si les anguilles sont capables de percevoir des variations aussi faibles de conductivité (80 μS cm−1), ceci pourrait constituer un signal pour l'orientation vers l'aval

Kunnskapsstatus leppefisk : Utfordringer i et økende fiskeri

Over the past few years there has been a rapid increase in the use of wrasses as cleanerfish for sealice on salmon farms. During 2010, the landed catch of wrasse was 440 tons, more than twice the 2009 catch and nearly ten times the 2008 catch. This rapid and exrteme increase in the fishing pressure on these species has occurred despite very limited knowledge of their biology, ecology and population dynamics. This has led to justifiable concern about the sustainibility of this resource. Wrasse demonstrate specialized life history traits. Many species change sex during their lifetime and exhibit species-specific mating behaviour, including nest building and parental care of eggs. This mating strategy lends to limited dispersal of offspring, ond only goldsinny wrasse have pelagic eggs. Many adult individuals are stationary, thereby creating a population struction dominated by Iocal populations. This population structure is also documented through genetic sludies in corkwing and goldsinny wrasse. Small local populations are more vulnerable to overfishing and possible extinction of local genetic adaptations. Studies of growth of wild wrasse demonstrate that goldsinsy and rock cook grow slower than corkwing. This suggests that the first two will take longer to recover from heavy fishing pressure. Results presented here suggest that both the composition of species and the size distribution; vary between habitats, particularly between exposed and sheltered areas. More precise and complete information on population structure. growth and maturation of these species is required 10 provide the knowledge base for sustainable fishing. Better knowledge of the health and welfare of these species - in salmon co-culture scenarios - is also needed

The swimming kinematics and foraging behavior of larval Atlantic herring (Clupea harengus L.) are unaffected by elevated pCO2

The kinematics of swimming behavior of Atlantic herring larvae cultured under three pCO2 conditions (control - 370, medium - 1800, and high - 4200μatm) were extracted at 34days post-hatch (dph) from swim path recordings obtained using silhouette video photography. The swim paths were analyzed for move duration, speed and length, stop duration, and horizontal and vertical turn angles to determine the effects of elevated pCO2 on fish larval behavior. The swimming kinematics and occurrence of S-postures in Atlantic herring larvae that had survived to 34-dph were unaffected by extremely elevated levels of seawater pCO2, indicating that at least some larvae in the population are resilient to ocean acidification