A biotest system for optimalization of environmental parameters for production of halibut fry

A system for controlled testing of different environmental parameters in seawater was made. Both the biotest system and an experimental setup using larvae of the Atlantic Halibut (Hippoglossus hippoglossus L.) are described

Oxygen consumption and bioenergetics of the Atlantic halibut (Hippoglossus hippoglossus L.) : implications for culture

Aspects of oxygen consumption and bioenergetics of the Atlantic halibut (Hippoglossus hippoglossus L. ) were studied under laboratory conditions. Resting oxygen consumption rate was monitored over 36 hour periods in Atlantic halibut while held individually in open system respirometers. Routine oxygen consumption rate was determined in small populations of tank held Atlantic halibut over 24 hour periods, through modification of tank systems as open system respirometers. Values for resting and routine oxygen consumption in this species were quantified and models Produced enabling the prediction of the energetic cost of homeostasis and spontaneousa ctivity for a range of fish size from 53g to 5861g, at temperatures of 6, 10 and 14°C. These results were ftirther used to form the basis of an energy budget equation for this species. PhotoPeriod influences on the periodicity of respiratory rhythm in both resting and routine oxygen consumption trials were determined through analysis of data recorded throughout the 24 hour daily period. The results indicated a cyclic respiratory rhythm, with peak oxygen consumption often observed nocturnally. The relevance of these results to culture of this organism are discussed. Post-prandial oxygen consumption and ammonia excretion were measured in small populations of tank held Atlantic halibut, these results contributing further information to the partitioning of energy within the metabolic and excretory components of the energy budget equation. Values for resting, routine and postprandial oxygen consumption in the Atlantic halibut were found to be low in comparison to roundfish species, but corresponded closely with literature data produced for other species of temperate marine flatfish. Activity patterns in small populations of Atlantic halibut were monitored over 24 hour periods in a specially constructed film unit. The results of this work showed dualistic patterns of activity over the diurnal cycle. Further elucidation of the energy budget was achieved through the determination of the metabolic costs of activity in the tank environment. Atlantic halibut were observed to remain at rest for periods of between 76% and 94% of any 24 hour period, with the time at rest dependent on fish size and stocking density. One 28 day trial was undertaken in which the components of the energy budget were measured simultaneously, and the balance of the budget investigated. Oxygen consumption, ammonia excretion, growth, feed consumption and faecal production were monitored within a purpose built experimental unit, and these values finther applied to the construction of an energy budget model. Finally, the oxygen consumption data of this study was ftirther applied to produce a model quantifying the water requirements of this species in a single-pass tank system, for the intensive culture of this species in the tank environment. Further development of these figures allowed the quantification of the pumping costs in an Atlantic halibut ongrowing tank system, and these figures were incorporated into a simple economic model. The results present some of the first bioenergetic data produced for this species, and this is an important step towards the development of an Atlantic halibut farming industry

Shallow-water residency and limited dispersal of Atlantic halibut in the Gulf of Maine

• Atlantic halibut (Hippoglossus hippoglossus), once abundant in the Gulf of Maine (GOM) on the northeast coast, were overfished until the stock collapsed in the 1940s. • In 2007, a three-year tagging study using electronic tags was done by the Maine Dept. of Marine Resources. • The objective of the study was to determine if GOM halibut migrate to spawning grounds on the Scotian Shelf and mix with Canadian halibut stock

A novel ladder-like lectin relates to sites of mucosal immunity in Atlantic Halibut (Hippoglossus hippoglossus L.)

A novel 27 kDa ladder-lectin-like protein, showing a multimeric structure under non-reducing conditions, was isolated from halibut serum by binding to N-acetyl glucosamine. Mass-spectrometry analysis did not show significant homology with known proteins. Specific antibodies were produced and used in immunohistochemistry on tissue sections of early halibut ontogeny from 119 until 1050 °d post hatching. A strong positive response was detected in the mucosal cells of the skin, gills and gut, indicating a role in the mucosal immune defence at these sites. Further immunopositivity was detected in liver, myeloma of kidney and the brain at different developmental stages but predominant expression was found in mucosal surfaces at later stages of development tested (1050 °d). It is still uncertain whether this ladder-like lectin forms part of the complement pathway, as a lectin or ficolin, or if it belongs to galectins. A strong detection in mucosal surfaces on skin, gills and gut, show similar patterns of expression as both mucosal lectins and galectins in other fish. Detection in neuronal tissue may indicate putative roles in tissue remodelling of brain and in ongoing neurogenesis in the fish eye

The effect of dietary Arachidonic acid concentration on Atlantic halibut (Hippoglossus hippoglossus) broodstock performance. Assessment of egg, milt and larval quality.

In order to evaluate the impact of four different diets on halibut broodstock, eight tanks were set up. Each tank contained 15 females and 5 males. The four broodstock diet formulations contained 0.4% arachidonic acid (20:4n-6; ARA), (0.4g ARA/l00g dry feed), 0.6% ARA, a control feed not supplemented with ARA and a control feed in which a proportion of the fish meal was replaced with squid meal, to improve palatability. The experimental diets were fed for a period of 3 years. The spawning period was regulated by photoperiod. Four tanks spawned in May and the four others spawned in July. A pit tag was used to identify each fish. This allowed individual length and weight data to be collected every 2 months. During the spawning season, milt, eggs, at different developmental stages, and yolk sac larvae were sampled for subsequent biochemical analyses (lipids, fatty acids and prostaglandins). Fish fed the ARA enriched diets showed significantly better growth compared to the other two treatments. During the second spawning season, fish fed the 0.4% ARA diet showed significantly improved egg production while fish fed on the 0.6% ARA diet showed a delay in their spawning season and poor reproductive performance. Fatty acid analyses on eggs, yolk sac larvae and milt showed significant ARA uptake and deposition in relation to the diet. Broodstock females fed the 0.4% ARA diet produced early life stages with what could be regarded as an optimal DHA: EPA: ARA ratio. Furthermore, males fed the 0.4% ARA diet produced the best quality milt over an extended period

The exorhodopsin and melanopsin systems in the pineal complex and brain at early developmental stages of Atlantic halibut (Hippoglossus hippoglossus)

The complexity of the nonvisual photoreception systems in teleosts has just started to be appreciated, with colocalization of multiple photoreceptor types with unresolved functions. Here we describe an intricate expression pattern of melanopsins in early life stages of the marine flat fish Atlantic halibut (Hippoglossus hippoglossus), a period when the unpigmented brain is directly exposed to environmental photons. We show a refined and extensive expression of melanopsins in the halibut brain already at the time of hatching, long before the eyes are functional. We detect melanopsin in the habenula, suprachiasmatic nucleus, dorsal thalamus, and lateral tubular nucleus of first feeding larvae, suggesting conserved functions of the melanopsins in marine teleosts. The complex expression of melanopsins already at larval stages indicates the importance of nonvisual photoreception early in development. Most strikingly, we detect expression of both exorhodopsin and melanopsin in the pineal complex of halibut larvae. Double-fluorescence labeling showed that two clusters of melanopsin-positive cells are located lateral to the central rosette of exorhodopsin-positive cells. The localization of different photopigments in the pineal complex suggests that two parallel photoreceptor systems may be active. Furthermore, the dispersed melanopsin-positive cells in the spinal cord of halibut larvae at the time of hatching may be primary sensory cells or interneurons representing the first example of dispersed high-order photoreceptor cells. The appearance of nonvisual opsins early in the development of halibut provides an alternative model for studying the evolution and functional significance of nonvisual opsins.acceptedVersio

A Rare Case of Completely Ambicoloured Atlantic Halibut, Hippoglossus hippoglossus, from the Lower St. Lawrence Estuary, Quebec

An Atlantic Halibut (Hippoglossus hippoglossus) (41.4 cm fork length) with the same pigmentation on the blind side as on the ocular side (ambicoloration) was captured in the lower St. Lawrence estuary, Canada, on 24 June 2004. This specimen represents the most extreme case of ambicoloration published for this species to date. As in other cases of extreme ambicoloration, this specimen shows other signs of abridged metamorphosis and reduced asymmetry, such as incomplete migration of the left eye and a hooked dorsal fin. Studies of hatchery-reared larvae have shown that the most common cause of malpigmentation, including ambicoloration, in halibut is a diet containing inadequate amounts and proportions of essential unsaturated fatty acids shortly before metamorphosis. Even though not expected to be common in the wild, inadequate diet for a short duration before metamorphosis is the most likely cause of ambicolouration in wild halibut

Health and productivity monitoring of cage-cultured Atlantic halibut (Hippoglossus hippoglossus)

The Atlantic Canadian aquaculture industry is dominated by Atlantic salmon production. In recent years, infectious disease, parasitic infestations, and price fluctuations from international competition have caused disruptions to the industry. Diversification of the industry away from Atlantic salmon production is a potential strategy to insulate the industry from these fish health and market challenges. Atlantic halibut has long been a primary candidate for this diversification. However, the early commercialization of the species over the last 15 years has failed to reach its potential, owning primarily to a lack of information on the biology of the species, best management practices and proven economic feasibility. To address this information gap, a multi-objective Randomized Controlled Trial (RCT) was conducted at a commercial farm on the Bay of Fundy in New Brunswick. The study collected detailed information on the growth and survival of 5000 Atlantic halibut individually identified with Passive Integrated Transponder (PIT) tags and followed over a four year grow-out period. The main objectives of this research were: (1) to evaluate the impact of individual fish characteristics on growth, survival and farm economics, (2) to determine the effects of oil-adjuvanted vaccines on growth performance, survival and vaccine associated lesions, (3) to evaluate the suitability of FT4 Lock-on tags as an external tagging method for individual identification of Atlantic halibut, and (4) to test a Stratified Transport System (STS) as a means of improving fish welfare and the economics of overland halibut transport. A variety of fish level characteristics were found to be important predictors of productivity. Identifying and culling fish with these specific characteristics prior to grow-out was identified as a method to improve overall farm productivity. The side-effects of oil-adjuvanted vaccines were found to be mild in Atlantic halibut, thereby identifying oil-adjuvants as an available tool for future vaccine development. FT4 Lock-on tags were found to be suitable for identifying cage-cultured halibut with the exception of substantial impacts on growth. The STS was demonstrated to reduce post-transport mortality, establishing it as a cost-effective transport solution over currently practiced methods. In conclusion, this research allows producers to make evidence-based management decisions, to strengthen and facilitate the continued development of the Atlantic halibut aquaculture sector in Atlantic Canada

Maternal effects on oocyte quality in farmed Atlantic halibut (Hippoglossus hippoglossus L.)

Atlantic halibut (Hippoglossus hippoglossus) oocyte quality is highly variable and one of the major bottlenecks during fry-production for on-growth in commercial Atlantic halibut farming. In this study, the effect of maternally derived oocyte constituents (i.e. yolk components and mRNAs) on oocyte quality (i.e fertilisation, embryonic hatching and normal blastomere symmetry) in farmed Atlantic halibut has been investigated. Atlantic halibut embryos and larvae depend on nutritional yolk components until larval first feeding. The importance of yolk n-3 fatty acids for oocyte quality was confirmed. However, highest positive correlations with oocyte quality were found for the less studied fatty acids dihomo-γ-linolenic acid (DGLA, 20:3n6) and docosapentaenoic acid (DHA, 20:5n3) that are known to compete with two of the most abundant fatty acids, arachidonic acid (ARA, 20:4n6)and docosahexaenoic acid (DPA, 22:5n3), respectively during fatty acid metabolism. High methionine and aspartic concentrations, amino acids essential to eukaryotic protein synthesis, were found to influence oocyte quality positively while no significant correlations were found between oocyte folate concentrations and oocyte quality. Before activation of zygotic transcription, maternal mRNAs control cell divisions and embryonic patterning. Due to the limited available genomic information on Atlantic halibut maternal transcripts, an expressed sequence tag (EST) maternal library containing 2,341high quality ESTs was created by suppressive subtractive hybridization (SSH). The maternal library constitutes an EST pool to identify suitable Atlantic halibut reference genes and identify differentially expressed maternal genes in high and low quality Atlantic halibut oocytes. To perform reliable quantification of gene expression by qPCR, stable reference genes have to be used to normalize target gene expression. Tubb2/Actb and Tbb2/Fau were identified as the best two-gene normalization factors during Atlantic halibut embryonic and larval development. Either of these normalization factors can be used for future developmental gene expression studies in Atlantic halibut. Tubb2/Actb was further used as reference gene during this study. Poor embryonic hatching success was found to not be correlated with a general decrease in oocyte maternal transcript abundance but with low transcript levels of specific maternal transcripts by qPCR. The majority of genes showed either no or very minor correlations between their transcript levels and oocyte quality parameters (Fertilisation: 13-93 %, embryonic hatching: 1-94 %). However, maternal transcript levels of three genes, most likely involved in nuclear protein and mRNA transport, growth factor regulation, and embryonic patterning, correlated with oocyte quality. Further, a new Atlantic halibut 4x44k oligonucleotide microarray was constructed and used to identify 192 strictly maternal genes during Atlantic halibut embryonic development and 20 differentially expressed genes between high and low quality oocytes, involved in immune response, metabolism, RNA transcription, protein degradation, cell signalling and the cytoskeleton. Microarray validation confirmed its suitability for future gene expression studies during Atlantic halibut embryonic development. The identified maternal genes in this study can serve as a pool for future in-depth studies of embryonic gene expression to advance the knowledge of important developmental processes such as germ cell development, growth and immune response in Atlantic halibut. Some of these may serve as possible markers for Atlantic halibut oocyte quality due to their high expression differences between high and low quality oocytes. Future nutritional studies on Atlantic halibut broodstock should focus on the identified yolk constituents acting positively on oocyte quality

The effects of different levels of macronutrients on growth, histology and gene expression in the hindgut of Atlantic halibut (Hippoglossus hippoglossus)

Masteroppgave i biologiBIO399MAMN-BIOMAMN-HAVS