Food and feeding of young herring larvae of Norwegian spring spawners

The gut contents of young herring larvae sampled each hour from 3 to 9 April 1967 at three depth intervals around a floating drogue were examined to study their feeding. Copepod eggs constituted more than 90% of the food items. Feeding started shortly after sunrise within the same hour in the depth intervals 25-5 m, 30-50 m and 75-55 m. Mean length increased with diminishing yolk sac until absorption when mean length decreased. The latter could indicate lack of suitable food. The mean gut content of feeding larvae did not increase until after absorption of the yolk sac. Larvae from the deepest strata had less gut contents than the others, probably because a lower percentage of them had absorbed yolk sacs. A high percentage of larvae feeding during day-time contradicted total defecation due to capture. No correlation was found between numbers of Calanus eggs in the guts and in plankton. Larvae containing Calanus nauplii had more assorted gut contents than larvae containing Calanus eggs. The critical period concept is discussed

Food and feeding of young herring larvae of Norwegian spring spawners

The gut contents of young herring larvae sampled each hour from 3 to 9 April 1967 at three depth intervals around a floating drogue were examined to study their feeding. Copepod eggs constituted more than 90% of the food items. Feeding started shortly after sunrise within the same hour in the depth intervals 25-5 m, 30-50 m and 75-55 m. Mean length increased with diminishing yolk sac until absorption when mean length decreased. The latter could indicate lack of suitable food. The mean gut content of feeding larvae did not increase until after absorption of the yolk sac. Larvae from the deepest strata had less gut contents than the others, probably because a lower percentage of them had absorbed yolk sacs. A high percentage of larvae feeding during day-time contradicted total defecation due to capture. No correlation was found between numbers of Calanus eggs in the guts and in plankton. Larvae containing Calanus nauplii had more assorted gut contents than larvae containing Calanus eggs. The critical period concept is discussed

Recordings of mature Gonatus fabricii (Lichtenstein) off the Norwegian coast

Two mature female and three mature males were sampled by trawling with a pelagic trawl at depths of more than 800 m off northem Norway. A third female were sampled with bottom trawl at 970 m off mid Norway. The females had a flabby, swollen appearance and degenerated tentacles and from 5 to 12 mature eggs on the ovary. The mature eggs had a largest diameter varying from 4 to 6 mm. The females were all larger than the mature males and the smallest had a DML of 260 mm. The females seems to mature at lengths between 200 and 250 mm. The mature males had spermatophores, 7 to 9 mm long, in the spermatophoric sac and in the penis, showing that they had not copulated. The smallest male had a DML of 190 mm. The males seems to mature at smaller length than the females. Assuming the same growth rate as observed at West Greenland, Gonatus fabricii seems to mature at an age of 2 to 2,5 years. Other recordings of larger mature males could indicate a second mating at an age of three years. The recordings of mature females at bottom indicate spawning at bottom. Recordings of mature females from summer to end of November indicate that spawning takes at least place during this period. The recordings of mature females at bottom indicate spawning at bottom. Recordings of mature females with emty spermatophores more than 500 m above bottom arise questions of a second mating or pelagic spawning

Spawning areas and spawning period of the North-east Arctic haddock [HELP 25}

Spawning of North-East Artic haddock occurs on the Norwegian continental slope. The location of the spawning grounds is, however, diffuse. This is mainly due to difficulties in identifying haddock eggs. In this work this problem is solved by using the biochemical genetical approach of electrophoresis. The results from haddock egg and trawl surveys in April -May 1987 and 1988 are analysed in relation to previous knowledge of haddock egg distribution and mature fish. Gonad maturity is compared to the distribution of egg developmental stages i n different regions. Both horizontal and vertical gradients in gonad maturity of haddock are revealed. Most of the Tromsøflaket area from Nordkapp to near the shelf edge bordering the Norwegian Sea (Norskehavet) are inhabited by immature haddock. An increase in abundance of mature fish takes place in the western part of the shelf. The main spawning areas of North-East Arctic haddock seems to be the southeastern part of the continental slope of Tromsgflaket at depths from 303 to 600 m and temperatures between 4ºand 6º C. Other spawning areas are found in Vestfjorden and over the continental slope from Tromsøflaket south to Rosttunga. The spawning in Vestfjorden seems to take place a t depths shallower than 200 m, but within the same temperature limits . Spawning seems to start at the beginning of April, reaches its maximum at the end of the month and ends during the first half of May. Very little spawning is recorded on the shelf and the continental slope from Røsttunga to 64º N. Spawning i n the area 62-64º N (Møre) is supposed to origin from a local stock. The onset of this spawning seems to take place a week or two earlier than what was observed further north. A distinct bimodal distribution of larvae sampled in July 1987 indicate a possible influx of haddock larvae to the Norwegian coast which might originate from a population different from the North-East Arctic haddock

Tilgjengelighet av seismiske aktiviteter i forhold til sårbare fiskeressurser. [HELP 38]

Rapporten presenterer biologisk informasjon som grunnlag for vurderinger av tilgjengelighet for seismiske aktiviteter til havs i forhold til gyteområder, gyteperioder og driftområder for fiskeegg, larver og yngel. Dette er gjennomført ved først å presentere spesielle karakteristika for våre viktigste kommersielle fiskearter i ulike livsfaser med spesiell oppmerksomhet på gyteområder, gyteperioder og tidlige livsstadier. For lodde har vi dessuten påpekt visse spesielle atferdstrekk som kan medføre mulig risiko for skade også for voksen fisk. En kort gjennomgang av oseanografiske og topografiske forhold i norsk økonomisk sone er gitt for å forklare typiske trekk ved havstrømmene. Disse påvirker og dels styrer spredning og fordeling av egg, larver og yngel. Videre har vi tatt utgangspunkt i at ulike seismiske utrustninger vil medføre ulike belastninger på organismene innenfor et område. Her trekker vi inn type seismiske tokt, antall og type signalkilder, utsendt energi fra disse og hvordan de er fordelt arealmessig. På grunnlag av dette og etablert viten om sannsynlige skadevirkninger fra seismiske aktiviteter på egg, larver og yngel og forvaltningsmessige retningslinjer, har vi gitt tilrådinger om geografiske områder som bør vurderes vernet til visse tider for å hindre uønsket dødelighet på fisks tidlige livsstadier

Some preliminary results on food and feeding of young capelin larvae

The gut contents of young capelin larvae sampled during a 24 hour period around a floating drogue were examined to study their feeding. The food consisted mainly of Calanus eggs (52%) and Calanus nauplii (42%). Compared to their abundance in plankton, Calanus eggs were by far preferred. The young larvae started to feed while still having large yolk-sacs, and the percentage of larvae feeding increased with decreasing yolk-sac size. No change in diet with age could be seen. Feeding started shortly after sunrise and declined at nightfall. A low percentage of larvae with gut content might indicate that the densities of food particles in plankton were too low to maintain survival and growth

Norwegian investigations on Gonatus fabricii (Lichtenstein)

By far the majority of the investigated Gonatus fabricii were caught as bycatch by pelagic trawls fishing in the upper 60 m. Sampling took place in April/May, June/July and August/September in the period 1978- 1991. The distribution of gonatus along the Norwegian coast south of 71 °N is clearly connected with Atlantic water with salinities above 35‰ . The highest concentrations are found in the area between Jan Mayen and Spitsbergen, i.e. in the Polar front area. The biomass of young gonatus in the Norwegian Sea constituted at least 1,5 mill tonnes in July 1994. Young gonatus begin to occur in the surface layers in May, and they seem to descend from the upper 60 m at a length of 50-60 mm. They might then live near the bottom or pelagically at depths of 200-600 m. Age and growth based on counts of primary growth rings should be treated with caution. At least in the eastem part of the Norwegian Sea prey items for gonatus are, in decreasing order of impoerance, amphipods, mainly Parathemisto spp., copepods, chaetognaths and euphausiids. Larger gonatus consume fry of Sebastes sp., Maurolicus miilleri, and small gonatus. Based on catch statistics are four spawning areas for gonatus suggested: West of Spitsbergen, off Vesterålen, off Møre and between Iceland and Jan Mayen. Hatching seems to take place throughout the year while the main spawning takes place from December to April. The growth rate of the statoliths decreases strongly in gonatus with DML 70-250 mm. The correlation between the rostral length of the gonatus beak and dorsal mantle length was calculated. Gonatus are important as food for the bottlenose whale. It has been recorded in stomachs of hooded seals, salmon, blue ling and Greenland halibut