Sperm was collected from testes and from three or four parts of the deferent ducts of 4 to 6 winter-spawning male rainbow trout, about every two weeks over a three month period (January toMarch). Milt volume, spermatocrit, sperm motility, 11-ketotestosterone (11-KT) and 17α-hydroxy,20β dihydroprogesterone (17,20P) levels and ionic composition were determined. Steroids and ions were also measured in blood plasma. The K+ concentrations and steroid levels in the seminal fluid from each part of the ducts did not vary significantly over the period of study. In two out of the three parts of the ducts, Na+ (parts 1 and III) Ca2+ (parts I and III) and Mg2+ (parts I and II) levels were significantly higher at the end of March than two months earlier. Motility of testicular sperm peaked (42%) in mid-February while that of sperm from ducts usually remained stable (80 to 100%) throughout the three months. Seminal fluids and blood plasma were confirmed to be isotonic (300 mmol/kg). Levels of K+, Na+, Ca2+, 11-KT and 17.20P in the plasma and seminal fluid differed significantly (respectively 0.3 vs 34 mmol, 134 vs 116 mmol, 3.4 vs 2.0 mmol, 87 vs 17 to 39 ng/ml, 11 vs 3 to 13 ng/ml), with the Na+ and steroid levels being positively correlated in both liquids. Osmolality, Cl-, Na+, K+, Mg2+ and Ca2+ concentrationsremained constant along the genital tract. In contrast, spermatocrit and 11-KT and 17.20P levels decreased significantly and progressively from testis to the posterior or middle part of the ducts (respectively 97 to 49%, 39 to 17 ng/ml, 13 to 3 ng/ml) while sperm motility (percentage of motile cells and duration of motility) increased (74 to 96% and 41 to 51 s). No significant correlation was found between sperm motility and the studied physicochemical parameters of the seminal fluid.

A protocol for the extraction of genomic DNA from teleost fish was developed and produced high molecular weight DNA from English sole, white sucker and rainbow trout. A protocol for polymerase chain reaction (PCR) of tumour suppressor gene p53 from rainbow trout genomic DNA was developed. Several primers were chosen inside exon 5 and 9 and exon 6 and 7. A successful PCR method yielded the conserved exon 5 to 9 region of genomic rainbow trout p53 in two fragments: fragment 1 comprising exons 5 and 6 and fragment 2 spanning the region of exons 7 to 9. The apparent molecular weight of fragments 1 and 2 were 510 and 760 base pairs respectively. The sequences of both fragments including the introns were determined and gave 515 and 793 bp for the two PCR fragments. These sequences will facilitate examination of tumour suppressor gene p53 conserved exons from genomic DNA e.g. for study of p53 mutations in fish.

The dynamics of astaxanthin and canthaxanthin were studied through an 11-month feeding experiment by following carotenoid deposition in male and female rainbow trout muscle, during and after spawning. Carotenoids were analysed by chromatography (HPLC), muscle colour was measured by a colourimeter and visual rank evaluation. In both sexes, a decrease in the muscle carotenoid content was observed at spawning time. The recovery of the muscle pigmentation differed between females and males, but seemed not to be influenced by the type of carotenoid additives in feed. The carotenoid content of the female muscle increased rapidly after spawing, while in the male this increase was slower. Eighteen weeks after spawing, carotenoid concentrations in the muscle of females corresponded to those before spawning, while in males they reached only one third of that amount. Significant correlations were found between chemical analysis, colourimetric measurements and visual rank evaluation.

The objectives were to evaluate temporal variation in 137Cs in trout and charr from Crummock Water, Wastwater, Ennerdale Water, and to compare levels in trout from six lakes (above three + Windermere, Loweswater, Devoke Water) and charr from four lakes (above three + Windermere). Fish were caught between June 1986 and October 1988, chiefly with fyke nets and gill nets. Overall means for 137Cs in trout were markedly higher than those for charr in the three lakes. Values for individual trout exceeded 1000 Bq.kg-1 in Ennerdale and 500 Bq.kg-1 in Wastwater and Crummock Water, but values for charr never exceeded 350 Bq.kg-1. 137Cs content increased with fish weight for trout from Wastwater and therefore values were scaled to a standard weight in subsequent analyses. No similar relationships were found for trout in Ennerdale or Crummock Water, or for charr in all three lakes. Monthly mean values for 137Cs in trout followed similar temporal patterns in the three lakes and a parabola provided a simple model for these changes. Chernobyl deposition occurred early in May 1986 and maximum values in trout were in December 1986 in Wastwater, January/February 1987 in Ennerdale Water and March 1987 in Crummock Water. The exponential rate of decrease from these maxima did not differ significantly between the three lakes, and ecological half-lives of 137Cs in the trout differed slightly, but not significantly, between lakes : 180 days for Wastwater, 194 days for Crummock Water and 249 days for Ennerdale Water. The equivalent value for Ennerdale charr was lower at 132 days, and it was impossible to fit models or calculate half-lives for Wastwater and Crummock charr. Maximum monthly geometric mean 137Cs values in trout from six lakes and charr from four lakes were related to the initial concentration of 137Cs in both water and sediment, and the maximum monthly geometric mean 137Cs values obtained from the routine water samples. The relationship was curvilinear and approximated, but was not identical to, an asymptotic curve. No similar relationships were found with mean Ca or K levels in the lake water. Metabolic and diet differences may explain the lower 137Cs levels in charr compared with trout and differences for the same species from different lakes may be due to limnological variations and différences between lakes in the nature of their sediments and catchment soils. Both points are discussed in detail.

In this study an attempt was made to develop a suitable diluent based on the characteristics ofgood quality ovarian fluid of Oncorhynchus mykiss. The resulting simulated ovarian fluid (SOF) was compared with Borax-borie acid buffer diluent and adjusted versions thereof. The composition of al1 these diluents are given in this paper. Maximum fertilization success (81.76%) was achieved when ovarian lluid was employed as a sperm diluent. Spermatozoa showed maximum (34 seconds) forward motility after dilution with Borax 3. The use of diluents in artificial fertilization techniques by trout farmers can help them to increase the fertilization success and also facilitates hatchery procedures and broodslock management.

Cryopreservation of sperm is an important component of genetic conservation programs for fish.However, since fish eggs or embryos cannot be successfully cryopreserved and since the mitochondrialDNA is maternally inherited, the mitochondrial genomes of fish populations are presently not beingpreserved in these programs. One method of obtaining eggs from stored materials would be tocryopreserve embryonic cells that could later be transplanted into female recipient embryos, formingchimeras; a proportion of these transplanted cells would be expected to enter the germ line andsubscquently develop into eggs. The hypothesis of this study is that isolated blastomeres of rainbowtrout can be successfully cryopreserved and thawed. The objective of this investigation was to determine if the rate of cooling or the type of container alters cryopreservation success. Isolated blastomeres in a freezing solution containing 8.7% DMSO were subjected to one of two different cooling rates in either 0.5 ml French semen straws or cryovials. Thawed samples were examined using phase contrat microscopy, wkh cells scored as being either intact or non-intact. In the nonfrozen control group, 85.4%f 7.6 ($\bar{x}$ ± S.D.) of the blastomeres were intact. There was no significant difference between the cooling rates used in this investigation based on the proportion of intact cells, but there was a significant (p < 0.002) difference in the proportion of intact cells between samples frozen in French straws (35.9% ± 16.5) and those frozen in cryovials (19.4% ± 4.9).

Samples of trout (Salmo trutta L.) were taken from four rivers in the Conwy system, North Wales: the Roe and the Nant-y-goron, which support sea trout stocks, and the Iwrch and Machno which are situated above impassable waterfalls and contain resident trout. Tissue samples from the fish were used in electrophoretic analysis of enzymes. Fourteen loci were scored of which six were polymorphic (Pgi-2, Gpd-2, Ldh-5, Mdh-2, Mdh-4 and Ck-2). Allele frequency data from these loci were used to test interpopulation heterogeneity, which indicated that the two upstream samples were probably reproductively isolated from each other and also from the downstream samples. Mean heterozygosity was generally lower in the upstream stocks compared with the sea trout populations. UPGMA cluster analysis based on Nei's genetic distance (D) revealed a clear dichotomy between those stocks above, and those below waterfalls. This was best explained by the presence of two strains of trout in the system. One strain, the resident trout occurring above impassable waterfalls, was characterized by high frequencies of the Ldh-5(100) allele, the other strain, principally consisting of sea trout, exhibited high frequencies of the Lhd-5(90) allele.

Rainbow trout juveniles (Oncorhynchus mykiss) were fed diets containing high levels (50, 70 or 100%) of vegetable proteins for 8 weeks. Vegetable protein sources employed were soybean meal, lupin seed meal and corn gluten meal, as well as potato protein concentrate. Nutritional evaluation showed that diets containing 50 or 70% plant protein supported growth rates, fish acceptance and nutritive utilization similar to those of both a whole fish meal diet and a commercial trout feed. A taste panel proved that organoleptic properties of fish were not affected by feeding on diets containing high levels of vegetable feedstuffs.

Rainbow trout were fed two experimental diets differed in lipid content by replacement of crudestarch (lipid-poor diet : 4.2% lipid or lipid or lipid-rich diet : 14.8% lipid) supplemented or not with antibiotics (a combination Flumequine + Gentamycin, 1:4). The apparent digestibility of dry matter, crude protein, lipid, carbohydrate and total energy were measured. Addition of lipid by replacement of crude starch in the fish diet in the absence of antibiotics enhanced significantly (p < 0.01) the apparent digestibility of dry matter, crude protein, carbohydrate and total energy, but did not influence those of lipid. Antibiotics supplementation of the lipid-poor diet (consequently with a high level of carbohydrate) enhanced significantly (p < 0.01) the apparent digestibility of dry matter, crude protein, lipid, and total energy, but not those of carbohydrate. On the other hand the antibiotics-treated lipid-rich diet (consequentlywith a low level of carbohydrate) showed a higher (p < 0.01) digestibility for dry matter, lipid, carbohydrate and total energy, but not for crude protein. The stimulatory effect of antibiotics on nutrient digestibility is discussed.

Les spermes de deux lots de 20 mâles d'une souche de truite arc-en-ciel (Oncorhynchus mykiss) à reproduction printanière, ont été collectés individuellement une fois par semaine pendant 10 semaines. Seuls les spermes d'un volume supérieur à 5 cm3 ont été utilisés pour cette étude. Pour chacun, la concentration en spermatozoïdes, l'osmolarité et les concentrations enzymatiques en glutamique oxaloacétique transaminase (GOT) et stéroïdienne en 17 α, 20 β-dihydroxy-4-pregnen-3-one (17 α, 20 β-OH-P) du plasma séminal ont été mesurées. Des échantillons de spermatozoïdes ont été incubés pendant 1 et 24 heures dans des solutions hypotoniques (60 et 20 mOsm) et leurs réactions (gonflement, éclatement, colorabilité ou non par l'iodure de propidium) ont été analysées. Un échantillon de chaque sperme a été congelé en boulettes à partir desquelles la GOT libérée par les spermatozoïdes après décongélation a été dosée. Des fécondations ont été réalisées avec du sperme frais et du sperme congelé-décongelé.

L'analyse factorielle des correspondances (AFC) entre la fécondante du sperme après congélation d'une part et la fécondante à l'état frais, les caractéristiques physico-chimiques et les résultats des différents tests de qualité membranaire d'autre part, a montré que l'aptitude à la cryoconservation peut être estimée a priori à partir de la mesure de la pression osmotique séminale et de tests reflétant l'intégrité fonctionnelle de la membrane. Ce résultat confirme le rôle déterminant de la membrane lors de la congélation.

The body components of female rainbow trout (Salmo gairdneri) reared in an experimental fish farm were studied during sexual maturation. For a period of 13 months, carcass, liver, gut and ovaries were sampled every month and their fat and non fat constituents analysed. In the trout, lipids are mainly stored in the carcass and to a less extent in the gut and ovaries. The distribution ranged from 68 to 73%, 31 to 6% and 0.1 to 20%, respectively from the beginning to the end of sexual maturation (March-November). Whatever the stage, carcass and visceral total lipids (TL) were mainly composed of neutral lipids (NL). The ovarian NL relative to TL content decreased from 90% during the first gonadal slow growth phase (SG. I from March to June) to 60% at ovulation in October or November while the proportion of phospholipids (PL) increased during the second slow growth phase (SG. II from July to August) and the rapid growth phase (RG from September until ovulation in October or November). This observation suggests that trout preferentially incorporate fatty acids into phospholipids in the oocyte during late ovarian growth.

During sexual maturation there was a large mobilisation of carcass and visceral lipid reserves, but non fat dry matter (NFDM) was only slightly changed. In our experimental fish (mean weight 1200 g) the loss of lipids averaged 76 g (42 and 34 g, respectively from the carcass and gut) versus 33 g for NFDM (from the carcass mainly). Loss of visceral lipids began during SG. I and ceased at ovulation in November, whereas loss of carcass lipids seemed to start during the RG phase and finished 1 month after ovulation.

Un lot de 40 mâles d'une souche de truite arc-en-ciel (Salmo gairdneri) à reproduction printanièrea été suivi. Seuls les spermes d'un volume supérieur ou égal à 6 ml ont été caractérisés et congelés enboulettes. L'analyse factorielle des correspondances entre les caractéristiques et la fécondance dusperme après 5 à 9 mois de congélation a montré en particulier que l'aptitude à la cryoconservationpeut être caractérisée par l'analyse du plasma séminal : les spermes médiocres sont associés à uneosmolarité plasmatique élevée (260 m-osmoles) et/ou une teneur élevée en protéine 42 KD, l'un desconstituants majeur de la membrane des spermatozoïdes; les très bons spermes sont associés àl'absence de protéine 42 KD dans le liquide séminal. Ces résultats renforcent l'idée que l'aptitude à lacryoconservation du sperme de truite dépend en premier lieu de la qualité de la membrane des spermatozoïdes.