Elin Kjørsvik

The early development of the halibut, Hippoglossus hippoglossus (L.), compared with other marine teleosts

Eggs were artificially fertilized and incubated in seawater of various salinities and temperatures. Both the ultrastructure of the exceptionally large eggs (average diameter: 2.92 mm) and the embryonic development suggest that the early developmental stages of the halibut are pelagic. Light and electron microscope studies of the halibut eggs showed a thin, homogeneous, lamellated chorion with small pores on the outer surface. However, neutral buoyancy determinations indicated that eggs would float only in salinities greater than c. 37 ‰. The halibut embryo, which develops very slowly, hatches at an apparently premature stage.

Appetite, gut transit, oxygen uptake and nitrogen excretion in captive Atlantic halibut, Hippoglossus hippoglossus L., and lemon sole, Microstomus kitt (Walbaum).

Abstract Atlantic halibut, Hippoglossus hippoglossus L., eat larger satiation meals (mean 11.7% body weight) than lemon sole, Microstomus kitt (Walbaum), (2.6% body weight). Total gut clearance time was about 120 h for halibut and 72 h for lemon sole. There are marked differences in feeding behaviour between the two species; halibut feed in midwater and require several body lengths of approach swimming before taking large items of food, while lemon sole eat only off the bottom. In shared tanks, no aggressive interaction was observed. A duoculture system holding small numbers of lemon sole with the more valuable halibut is recommended as a means of minimizing food waste and tank fouling. Oxygen uptakes of 0.07-0.11 ml O 2 g fish wt −1 h −1 (depending on nutritional state) were recorded for the two species. Ammonia nitrogen outputs were also similar. Starved halibut excreted 2.32 μg N g −1 h −1 , fed animals 5.08 μg N g −1 h −1 . The corresponding values for lemon sole were 3.26 μg N g −1 h −1 and 6.37 μg N g −1 h −1 , respectively.

Buoyancy in the lumpsucker Cyclopterus lumpus

The lumpsucker or lumpfish, Cyclopterus lumpus L. (Cyclopteridae, Scorpaeniformes), is a cottoid teleost, and, like other fish in its family, exhibits many characteristics of a coastal, bottom-dwelling fish. It is globiform, has no swimbladder, possesses a large abdominal sucker (formed from the pelvic fins), and lays demersal eggs which are brooded by the male parent for many weeks (Fulton, 1907; Cox & Anderson, 1922; Yesipov, 1937; Zhitenev, 1970; Mochek, 1973). The species spends the breeding season in shallow water, where both sexes may be seen attached to the rocks by their suckers. Early researchers (Couch, 1863; Day, 1880–4; Smitt, 1892) believed that the adults retreated to rocky bottoms in deep water after breeding. However, later workers (Cox & Anderson, 1922; Saemundsson, 1926, 1949; Andriyashev, 1954; Bagge, 1964; Blacker, 1983; Daborn & Gregory, 1983) have demonstrated that the lumpsucker spends much of its larval and adult life living epipelagically and in mid water in coastal and oceanic areas upon macrozooplankton (e.g. ctenophores, mysids). The term ‘semi-pelagic’ seems the most appropriate label for its mode of life.

Observations on the growth of juvenile Atlantic halibut (Hippoglossus hippoglossus L.) in captivity

Abstract Growth of juvenile Atlantic halibut kept in captivity in northern and western Norway was observed under satiation feeding conditions. In northern Norway, sea water temperatures ranged between 0.2 and 13°C. The total weight of 22 fish increased from 28.7 kg in October 1985 to 76.2 kg in January 1987. Biomass gain was minimal during the winter months. Fish were 2–4 years old at capture, and it was evident that growth rate was maintained at a higher level in captivity than in nature. Sea water temperatures were generally higher (4.5–12.5°C) and with lesser fluctuation amplitude in western Norway. Twelve fish were kept in captivity from June 1985 to October 1986, and total weight increased from 22 kg to 75.5 kg. Another group consisting of 26 fish increased in total weight from 22.8 kg to 39 kg during the period from May to November 1987. In general, the condition factor increased and was maintained at a higher level in captive fish than observed at the time of their capture.

Toxic effects of hydroxylated aromatic hydrocarbons on marine embryos

Abstract Phenol and methyl-substituted phenols were acutely toxic towards sea-urchin and fish eggs in concentrations of 3–30 ppm. Naphthols were considerably more toxic than phenols, killing most embryos even in concentrations of 0.3–3 ppm. Sublethal concentrations of phenols and naphthols caused pigment defects in cod larvae.

Some field and laboratory data from an oil spill in northern Norway during april 1982

Moderate amounts of oil came ashore in Troms county, northern Norway, in April 1982. Most of the oil was deposited in the supralittoral zone and ecological damage was slight. Toxicity tests with sea-urchin eggs and cod eggs and larvae showed seawater extracts of the ‘fresh’ stranded oil to be quite toxic; effects were noted at concentrations below 1 mg/1. After 5 months on the beach weathering had polymerized the oil extensively and further reduced its water solubility, but the viscosity had not changed appreciably. After 12 months the oil contained very small amounts of n-alkanes and volatile oxidation products, but the viscosity and water solubility had not changed much. Seawater extracts of the oil samples collected 5 and 12 months after the spill did not give any direct effects during 4 days treatment of sea-urchin and cod eggs, but during the further development of the cod, effects were observed during hatching in hydrocarbon concentrations around 1 mg/1.

Acute toxicity tests of the effects of oils and dispersants on marine fish embryos and larvae - A review

Abstract The toxicity of the various hydrocarbons and oil-related compounds varied with fish species and developmental stages tested. Generally cod embroys were most sensitive. Seawater soluble components from crude oil were less toxic than components from photooxidized and weathered oil. Single aromatic hydrocarbons varied in toxicity depending upon the number and molecular position of methylated groups. Cytological studies revealed chromosomal aberrations in exposed embryos.

Effects of short-term exposure to xylenes on the early cleavage stages of cod eggs (Gadus morhua L.)

Abstract Seawater solutions of the three isomers of xylenes were analysed both by gas chromatography (GLC) and ultra-violet spectroscopy (UV), and the two methods were compared. Cod eggs were exposed to seawater solutions of the xylenes. Concentrations ranged from less than 1 ppm to c. 35 ppm. Treatment during fertilization with ortho-xylene had no significant effect upon fertilization capacity, while meta-and para-xylene induced significant decreases in fertilization rate at concentrations above 10 ppm (p < 0.05). Fertilized cod eggs were exposed to xylenes 3 or 6 hours before the first cleavage. There was no significant difference in effect between the xylenes, and treatment for 3 and 6 hours gave similar effects. Effects upon the early cleavage pattern were significant from a concentration interval of 2–7 ppm (p < 0.01). Characteristic effects included inhibition of the formation, of the cleavage furrow. ‘Small cells’ or total absence of cleavage occurred in the highest concentrations (16–35 ppm), whil...