ALBERT

Notes: Abstract –  We studied some of the factors that might influence energy use in spawning Atlantic salmon (Salmo salar). Single females were placed into an experimental channel with either one or three males, after which spawning was monitored continuously. Male status was confirmed using genetic parentage analysis. Daily fat loss was monitored with the Torry Fish Fatmeter and validated through biochemical analyses. Several comparisons were in the expected direction but not statistically significant and therefore require further study: daily fat loss appeared higher for dominant males relative to subordinate males and in the three-male treatment relative to the one-male treatment. Most of the variation among individuals remained unexplained, suggesting that several as yet unknown factors strongly influence fat loss in spawning salmon. A large and significant effect was that daily fat loss was higher for females than for males, a difference that might contribute to the shorter spawning duration typical of females.

Notes: The molecular beam electric resonance technique has been used to examine the hyperfine spectrum of CsF to determine the nuclear quadrupole interaction of the cesium nucleus. A total of 95 transitions in vibrational states v=0−5 and rotational states J=1−8 have been included in a fit to determine the cesium nuclear quadrupole and spin–rotation interactions, the fluorine spin–rotation interaction, and the tensor and scalar parts of the spin–spin interaction. Vibration and rotation dependencies of these constants have been determined, allowing correction for zero point vibration effects. This experimental Cs nuclear quadrupole coupling constant when combined with the electric field gradient calculated using a relativistic coupled cluster method yields a nuclear quadrupole moment of the Cs nucleus equal to eQ=−3.43098 mbarn. The vibrational dependence of the coupling constant is smaller than the theoretical estimate. The coupling constants we have determined are the following: eQCsqCs=1245.598(10)−14.322(25)(v+1/2)+0.080(14)(v+1/2)2+0.0040(22)(v+1/2)3−0.00209(59)J(J+1)+0.00048(40)(v+1/2)J(J+1), cCs=0.66177(14)−0.01509(28)(v+1/2)+0.000550(94)(v+1/2)2, cF=15.08163(84)−0.1744(14)(v+1/2)+0.00234(41)(v+1/2)2−0.000093(13)J(J+1), c3=0.92713(53)−0.00917(93)(v+1/2)+0.00097(29)(v+1/2)2, c4=0.62745(30)−0.00903(22)(v+1/2). All values are in kHz units, with one standard deviation uncertainty estimates in the last two digits shown in ( ). © 1999 American Institute of Physics.

Notes: Genetic variation at 24 enzymatic loci was investigated in eight south European Atlantic salmon populations from the rivers Nivelle, Cares, Sella, Narcea, Esva, Navia, Porcia and Eo. In these rivers, management based on supplementation of native populations with foreign stocks was carried out for more than one decade. Population genetic patterns expressed in terms of allele frequencies, mean heterozygosity and conformity to Hardy-Weinberg equilibrium, were significantly different between populations. Relevant temporal changes of genetic variability were reported. Evidence that foreign stocking has disturbed the genetic patterns of some of the studied populations is presented.

Notes: Six males and five females anadromous Atlantic salmon were released in two sections of the Lapitxuri experimental stream (Southwest France), where they could reproduce naturally. Females had all the same size and age, contrary to males. We focussed our attention on the variation with time of spawning tactics and success of males. Two factors affected male spawning behaviour in the short term. An increase of the OSR increased the level of male competition around redds which resulted in a larger number of males adopting sneaking rather than fighting tactics. Changes in female activities also seemed to be detected by males, since male aggressiveness increased when females were close to oviposition. But whatever their activities, males preferentially courted the earlier spawning female when two females were active at the same time. Fighting in males was confirmed to be the most successful tactic at a given time. However, males adopting sneaking tactic at the beginning of the spawning season could dramatically increase their reproductive success in the long-term. Fighting males invested much more energy in contests than secondary males, which may constitute a handicap in terms of longevity. They could quickly lose their status or strength with time which, although placed in a situation of high OSR, resulted in greater numbers of previously low-ranking males adopting satellite and fighting tactics during the period preceding oviposition. Age more than size affected male status and reproductive success. Females seemed to select their mate directly in relation to their physiological condition, since they only attacked dull coloured males showing obvious wound marks. They also could indirectly choose their mate by repeatedly leaving the redd during the period preceding oviposition in a situation of high OSR. This behaviour might incite male competition and also promoted, by incessant attempts of secondary males to rob the more successful status of primary males, their chance to spawn with fitter males. These results emphasized the importance of environment, physiological condition and energy expenditure in allocation tactics and variations in salmon reproductive success throughout the spawning season. This led us to hypothesize that the choice of sneaking through conditional strategies might provide greater average fitness in salmon alternative life histories.

Notes: Interspecific relationships between Atlantic salmon and coho salmon were studied at early life stages in laboratory and semi-natural stream channels. During emergence, the survival and dispersal patterns were similar for the two species in single or mixed populations. Survival of Atlantic salmon fry was reduced in the presence of older coho fry. However, no predation was observed. Microdistribution differed between the two species, with Atlantic salmon fry more numerous in riffles when coho were present.Coho juveniles had a pelagic and gregarious distribution, in contrast to the benthic behaviour of the Atlantic salmon. In laboratory streams, Atlantic salmon fry moved out or adopted a subordinate cryptic behaviour which allowed them to escape predation while negatively affecting their growth.

Notes: Both sexes of Atlantic salmon Salmo salar were very sensitive to the absence of their mate on the spawning ground, particularly females during the last hour before oviposition. The improvement of behavioural chaining just before viposition might elicit the accurate timing of synchronized gamete release for successful fertilization. While the reproductive behaviour of the opposite sex could largely affect breeding activity, relative mate size appeared to be the prevailing sexual motivation factor in this species. Even in the absence of courtship, large mate size may constitute a supra-stimulus inducing an increase in spawning behaviour of the other sex. Females with smaller males delayed their first spawning activity, took longer to spawn and made more nests than those with large males. However, female egg retention was not influenced by relative male size.

Notes: A new nuclear DNA marker is described to identify Atlantic salmon, brown trout, and their hybrids. Species-specific banding patterns are obtained by digestion of genomic DNA with the restriction endonuclease Sac I and hybridization with a histone DNA probe. FISH analyses in hybrid metaphases illustrate the potential of interspecific hybrids for evolutionary studies.

Notes: The influence of overripening on salmonid egg quality has often been described in artificial breeding. However, no information exists on the impact of this factor on fish reproducing naturally, although it is likely to be critical, especially in disturbed environments. Pairs of Atlantic salmon in which the size of the male and the female was evenly matched were released in a spawning channel from 1 to 12 days after ovulation. Handling did not affect egg quality. Overripening had a negative effect on egg viability. Egg mortality, infertility and malformations increased with the number of days after ovulation. In females which had just matured, 16·7% of their recovered eggs were dead, 3·1% were unfertilized and 1·7% were malformed, as compared to 25·4, 9·7 and 5·4%, respectively, in females that had been mature for at least a week. Overripening played a role in both female spawning behaviour and capacity to spawn, as females which had been mature for over a week released their eggs more quickly while they retained more ova in their abdominal cavity than early spawning females. Thus, in studies of reproductive behaviour and in particular of sexual selection, it is critical to take into account the maturation status of females since the duration of spawning activity is used by various authors to determine female sexual motivation. Alternatively, overripening may decrease the female selectivity for mates.