Behaviour studies on fish reaction to long lines

This study is a continuation of a field investigation on the behaviour of fish towards long lines, started in 1976. The present paper gives an analysis of the effect of current and time of the day on the activity of whiting and haddock. Further, the influence of hook size and shape on hooking probability are shown

Uptake and elimination of aromatic hydrocarbons a chlorinated biphenyl in eggs and larvae of cod Gadus morhua

Artificially fertilized eggs and newly hatched larvae of cod Gadus rnorhua L. were exposed to 14C labelled naphthalene, phenanthrene, benzo(a)pyrene and 2. 4. 5. 2', 4', 5'-hexachlorobiphenyl (PCB) for 24 h and thereafter transferred to clean seawater. Radioactivity in eggs and larvae was measured at different times during exposure and after transfer to clean seawater. Maximum accumulation was found with phenanthrene, whereas naphthalene accumulated only slightly in both eggs and larvae. Naphthalene was, on the other hand, rapidly eliminated in contrast to the slow elimination of the other more lipophilic components. Most of the radioactivity accumulated in eggs was transferred to the larvae upon hatching. These findings show that cod eggs and larvae accumulate lipophilic xenobiotics from seawater and that the components will be stored for long time even after eggs and larvae are out of the polluted area

Fullskala havbeiteforsøk - laks, torsk, røye og hummer : Orientering om Fiskeridepartementes havbeiteprogram

Gjengitt med tillatelse av Nordisk Ministerrå

The distribution of cod larvae and prey organism in the Lofoten area related to critical prey concentration

The distribution of cod larvae and their main prey organisms in the first feeding areas off the Lofoten islands have been studied in sheltered and exposed areas in relation to feeding conditions. These findings are discussed in relation to laboratory studies on larval feeding dynamics and food density required to meet matebolic demands. It was found that the cod larvae are sporadic feeders having intervals of digestion between feeding periods. The maximu, gut filling of first feeding cod larvae was close to 3 prey/larval gut when nauplii were the dominant food organism. The larval gut evacuation processes were dependent on the value and state of degestion of the gut content. The critical prey density for first feeding cod larvae varied between 21 nauplii/1 and 190 nauplii/1 depending on larval swimming speed and feeding success. The highest concentrations of both cod larvae and its main prey organism, copepod nauplii, were found in the Austnesfjord, Hølla, Henningsvær and the Vesterålsfjord area. Patches of nauplii in densities between 50-100 per liter were found in these areas. From larval cod gut content analyses good agreement was found between feeding conditions and food density distribution. The effect of increased wind forces created a homogenous vertical distribution of both cod larvae and prey organisms causing reduced accessibility of food to the cod larvae

Primary growth increments in otoliths of cod larvae (Gadus morhua L.) of the Arcto-Norwegian cod stock

Primary growth increments have been detected in the otoliths of wild-caught, first-feeding cod larvae, living in a habitat where the light intensity is above the light threshold for visual feeding during 24 hours, and where the larvae were observed to have captured prey organisms both day and night. The comparison of increment counts and estimated age based on larval morphological characters, indicate a daily periodicity of the increments, but the relationship between the variates is not very strong in the very early larval stages