Production of high quality juveniles is still a bottleneck in the intensive culture of cod (Gadus morhua L.), and suboptimal nutrition at the larvae’s early life stages is one of the decisive factors for this. The cod larva hatches from small pelagic eggs, and has to start exogenous feeding shortly after hatching when it still lacks a functional stomach. Optimal feeding conditions are therefore crucial for the vulnerable larva at this early developmental stage. Copepod nauplii as live feed may provide nutritional benefits in terms of containing essential fatty acids in the phospholipid fraction that may be incorporated directly into membrane phospholipids, and also containing high amounts of free amino acids compared to rotifers and Artemia sp., which is applied as live feed in intensive production of cod today. The aim of the present study was to examine the effects of feeding with the intensively reared copepod Acartia tonsa compared to both enriched and unenriched rotifers (Brachionus ibericus), in terms of growth, survival, and functional development of the liver and gut. The liver and gut from larvae at 4 and 19 days post hatching (dph) was examined by performing quantitative measurements by stereology, and qualitative histological measurements on hepatocyte and enterocyte appearance. Mitochondrial development was given special emphasise to evaluate if there are tendencies implying a development in morphology of these energy producing organelles, and also whether they are affected by the nutritional composition of the live feed organisms.Feeding with copepod nauplii instead of enriched rotifers resulted in higher growth, survival, and increased pigmentation of the cod larvae. In addition it was found that feeding with rotifers, and especially with the unenriched type, showed signs of mitochondrial dysfunction in terms of cristae interdigitation within both hepatocytes and enterocytes. This was not found in the copepod-fed larvae, which might be attributed to providing phospholipid in the diet that may enhance normal development of biomembranes. Glycogen deposits were found in the hepatocytes in larvae at 19 dph, although to a much greater extent in the larvae fed rotifers, which might be due to differences in carbohydrate content in the different live feed organisms. The liver tissue was generally more evidently reflecting developmental processes between 4 dph and 19 dph and the effect of the live feeds nutritional value on the metabolic energy state of the larvae, than what the gut tissue did.

A mesocosm experiment was performed over 16 days during austral summer in 2010, in Northern Patagonia, Chile. Nutrients were added in 8 different concentrations along a gradient, simulating different levels of nutrients released by salmon farms. Nitrogen loading rate ranged from LN = 0 μg l-1 d-1 to LN = 42 μg l-1 d-1, and Silicate and Phosphorus were added in Redfield ratios. The goal of the study was to look at the effect of nutrient addition on the lower trophic levels of the marine pelagic food web represented by three groups of organisms: Phytoplankton, Ciliates and Copepods. Nutrient addition was found to have a very clear effect on chlorophyll a, POC and ciliate biomass, which showed a very clear linear increase with increasing loading rate. POC and chl a values showed that phytoplankton growth started immediately after nutrient addition. At the maximum level POC values had become 13 times larger than at the original level. Phytoplankton community composition, in the mesocosms with the highest loading rates, was found to shift from larger cells in the beginning of the experiment to smaller cells towards the end. Ciliate biomass was found to increase linearly with food concentration, indicating that ciliate population growth was closely tied to food availability. Ciliate biomass peaked on day 8 with 117 μg C l-1 found in the treatments with highest nutrient additions. A maximum of 91 ciliates ml-1 was found on day 16 during the experiment. Both these values are much higher than what has previously been reported in the area, indicating that ciliates might play a more important role in the Patagonian marine food web than previously thought. Copepod concentration and biomass were found to be uncorrelated to both nutrient addition and food concentration. This study found that nutrients released from fish farms have the potential to cause drastic increases in chl a and phytoplankton and ciliate biomass, as well as affect the community structure of phytoplankton.

The aim of this study was to enhance the knowledge on ecological and life-history parameters of Sclerocrangon boreas and Sclerocrangon ferox in Svalbard waters, including sex ratio, population structure, parasitism and prey preference. Little research has been done on S. ferox before. It has been subject to unprecedented research in the present study, considering size distribution, prey preference and DNA barcoding. The barcoding result gave a genetic distance of 13.7 % between S. boreas and S. ferox. This study shows a clear difference in size distribution between males and females. Females are considerably larger than the males. This is an indication of the two species being protandric hermaphrodite. These findings support earlier research, showing the same pattern, suggesting S. boreas being a protandric hermaphrodite. It has not been found studies looking on S. ferox considering this, but the present study shows also this species follow this pattern and are most likely protandric hermaphrodite. The largest groups of prey found in the stomach content were Crustacea, Echinoidea and Ophiuroidea. Individual specimens had mostly one type of prey in their stomach, but several types of prey were identified for both species. These findings suggest that S. boreas and S. ferox are specialists as individual specimens and generalists as species. The genetic results indicate that the specimens of S. boreas from Smeerenburg are distinguished from Grønfjorden and Rijpfjorden, and there were also variation within the specimens sampled in Smeerenburg. However, the results do not give a basis to conclude whether the populations have different genetic signatures between the fjords where S. boreas is found. It can be concluded that DNA barcoding and the CO1 gene do not together give ample information of genetic differences within populations, but it will still be able to give a genetic signal on differences between populations. Parasites were found on both S. boreas and on S. ferox. Genetic analyses, using CO1 and 18S, of the parasites conclude that they are cocoons from a piscicolid (fish) leech. The identity of this species has not been found.  

The stellate sturgeons as well as the other sturgeon populations inhabiting the Lower Danube River system (LDR) and the NW part of the Black Sea have experienced a severe decline due to heavy fishery, river regulation and water pollution. Traditionally, sturgeons have represented a great economic value for the countries along the Danube, being fished mainly for their eggs, the “black caviar”. The human population along the Danube River took advantage of the anadromous behaviour of these fishes and over decades of overfishing they depleted the stocks. In 2006 the Romanian government banned the commercial fishing of sturgeons for a period of 10 years and started a Supportive Stocking Programme of Danube with farmed juveniles originating from wild parents. The present study focuses on whether there are genetically isolated subpopulations among the adult cohorts of stellate sturgeons migrating into the LDR in the year 2010, and whether the genetic characteristics of YOY samples in the same year supports the existence of such subpopulations. Samples from fall and spring migrants and from YOY stellate sturgeons naturally born in the river in 2010 were genetically analyzed for mtDNA cyt b and D-loop regions as well as a panel of nuclear microsatellites, and revealed considerable individual variability. Hardy-Weinberg conformity tests revealed heterozygote deficit at 3 out of 4 microsatellite loci. Based on the genic differentiation at the microsatellite loci and mtDNA and cluster analyses, a genetically distinct group were demonstrated among the 2010 YOY samples, pointing to the existence of a previously unknown population substructure within the stellate sturgeons of The Lower Danube River. This was supported by biological characteristics of the YOY samples.

Sturgeons belong to one of the oldest families of bony fish in existence, having their first appearance in the fossil records approximately 200 million years ago. Their natural habitats are found in the subtropical, temperate and sub-Arctic rivers, lakes and coastlines of Eurasia and North America. In the Romanian waters, five anadromous species of sturgeon, out of the total 25 species known by science, once migrated from the Black Sea into the Danube for spawning: beluga; Huso huso, Russian sturgeon; Acipenser gueldenstaedtii, stellate sturgeon; A. stellatus, ship sturgeon; A. nudiventris and the European Atlantic sturgeon; A. sturio (Knight, 2009). The NW Black Sea and Lower Danube River sturgeons, like many Acipenserids, were seriously affected by the rapid changes brought by human development. Being one of the finest caviar producers in the world they were intensively harvested for many centuries. Heavy uncontrolled fishing and destruction of habitat led to the collapse of most of the Acipenserids and the total disappearance of the European Atlantic sturgeon (A. sturio) from the NW Black Sea. Public attention was focused world wide on sturgeons after their listing in the IUCN Red List of Threatened species in 1996. In 1998, after evaluating their abundance in the wild, CITES also decided to strictly regulate the international trade in all Acipenserids. The paper aims to analyze and review conservation measures that were taken locally, nationally and internationally by humans and the effect they had on one of Europe’s only naturally reproducing sturgeon populations.

Biofouling has become a serious problem for farmers in the Norwegian finfish aquaculture industry in recent years; with the hydroid Ectopleura larynx dominating the fouling community in southwestern and mid-Norwegian waters. Most farmers in Norway use a combination of strategies to deal with fouling: the use of copper coated nets combined with washing, the use of copper coated nets combined with drying, and the use of uncoated nets combined with frequent washing. Concerns have been raised about the use of copper coatings on nets due to possible environmental threats. A better understanding of fouling patterns with depth and time; as well as the effectiveness of environmentally friendly treatments is needed. The aims of the study were to identify the temporal and depth variability of biofouling on salmon cage nets from a farm in mid-Norway. Additionally, the effect of drying on hydroid survival and the effects of environmentally friendly anti-fouling treatments on the survival of E. larynx were investigated. The first experiment was to look at the development of biofouling on salmon cage nets at 3 different depths (1, 5 and 10 m) over a six month period (June-November). The second experiment involved the drying of hydroid colonies at 6 different drying times to determine the shortest time needed to ensure complete mortality of hydroids. The third experiment was to determine the effects of washing and drying on the recovery of hydroid colonies, using 5 different treatments; after which hydroids were allowed to recover for a two week period and analysed. The results showed that the major fouling groups were algae, molluscs, hydroids, crustaceans and bryozoans, with hydroids becoming abundant from August onwards. Hydroids began to completely colonise the nets from 10 m in September and then completely colonized the nets at all three depths in October and November. 48 hours of air drying caused a complete mortality of hydroids. Dead hydroids shed their hydranths and cut or damaged hydroids were capable of regeneration. Nets which had hydroids removed, damaged or cut by the washing process had the highest percentage growth increase after a two week recovery period. This study demonstrated that fouling communities differ with depth and time but are driven by some ecological interactions, and that, a combination of washing and then killing of hydroids with hot water; or washing and then drying can help farmers deal effectively with fouling. Further research into the feasibility of these on an industrial scale is recommended.

I investigated hoe different spacing of breeding sited affects different aspects of mating behaviour in the two-spotted goby. I found that clumped nest spacing affects nest occupations and reproductive success negatively. Clumped nest spacing incresed male agonistic behaviour and led to a higher variance in reproductive success.

The financial crises and global change have caused setbacks to the improvements in many undeveloped countries. To be able to achieve the ‘Millennium developmental goals’ within 2015, it will require a higher effort. Sub-Saharan African countries show the slowest economic growth and have experienced the highest setbacks. Malawi is one of these countries and is struggling with a high share of poverty and poverty related issues. Trade is believed to be the most prominent tool to fight world poverty, as it will provide economic growth and employment. Cichlid fishes from Lake Malawi are popular ornamentals for hobby aquarist’s world wide, representing yearly turnover of 340 million US dollars. It is suggested that ornamental Malawi cichlids can be developed into an industry benefiting country and the local poor people. This can be achieved without pressure upon the lake biodiversity if the wild-collected fishes are used for breeding purpose and not for export. To be able to deliver a high quality fish, it will be necessary to establish proper handling strategies that will ensure fish health and welfare. Stress from handling procedures is known to have negative impact on fish growth, reproduction, immune function and survival. Anesthetics may be a useful tool during handling procedures of the fish, as it can reduce the perception of the stressor and thus prevent activation of the hypothalamus-pituitary-interrenal (HPI) axis. In this study the three commercial anesthetics; MS-222, Benzoak® and Aqui-S™ were evaluated for; (1) anesthetic efficacy, (2) safety margin, (3) prolonged exposure and (4) stress-reducing capacity on the Malawi cichlid, red zebra (Metriaclima estherae). The overall results show that concentration of 150 mg/L MS-222, 120 mg/L Benzoak® and 50 mg/L Aqui-S™ gave satisfying introduction and recovery time for anesthesia. Both MS-222 and Aqui-S™ gave high safety margins as no fish mortality was recorded after anesthetic exposure for 30 minutes. Benzoak® gave a lower safety margin as there was recorded 50 % mortality following 10 minutes exposure. High mortality rate and sign of insufficient blockage upon the red zebra fish, suggested that prolonged exposure to the tested sedative dosages did not benefit the fish. MS-222 exposure reduced the stress response while Benzoak® and Aqui-S™ seemed to self-induce an increase in plasma cortisol concentration after anesthetic exposure. In conclusion; for short-term treatment on red zebra fish, a concentration of 150 mg/L MS-222 is recommended.

!

The aim of this thesis is to give insight into how a short term exposure to higher water temperatures affect photosynthesis in two of the most important species of the Norwegian kelp forest; Laminaria digitata and Saccharina latissima. In addition the effect of increased water temperature on kelp growing in the temperate regions, Trondheimsfjorden, will be compared the effect on kelp growing in the arctic region, Svalbard.