Four behavioral experiments conducted in both the laboratory and the field provide evidence that adult sea lamprey (Petromyzon marinus) select spawning rivers based on the odor of larvae that they contain and that bile acids released by the larvae are part of this pheromonal odor. First, when tested in a recirculating maze, migratory adult lamprey spent more time in water scented with larvae. However, when fully mature, adults lost their responsiveness to larvae and preferred instead the odor of mature individuals. Second, when tested in a flowing stream, migratory adults swam upstream more actively when the water was scented with larvae. Third, when migratory adults were tested in a laboratory maze containing still water, they exhibited enhanced swimming activity in the presence of a 0.1 nM concentration of the two unique bile acids released by larvae and detected by adult lamprey. Fourth, when adults were exposed to this bile acid mixture within flowing waters, they actively swam into it. Taken together, these data suggest that adult lamprey use a bile acid based larval pheromone to help them locate spawning rivers and that responsiveness to this cue is influenced by current flow, maturity, and time of day. Although the precise identity and function of the larval pheromone remain to be fully elucidated, we believe that this cue will ultimately prove useful as an attractant in sea lamprey control.
1992. [nfluence of fat content on uptake and depuration sf the sff-flavor 2-methylisobsrneol by channel catfish (bctalurus punctatus). Can. J. Fish. Aquat. Sci. 49: 2486-241 1.Channel catfish (Icealurus punstatus) sf different tissue fat contents (0.5-1 1 .O%) were held in water containing approximately 0.5 pg/L of the sff-flavor compound 2-methylissborneol (MlB) for various times. A new analytical method was developed to quantify tissue burdens of MlB. Fish showed significant bioeoncentration of MIB after 2 k and equilibrium by 24 h. The fatter fish (>2.5% muscle fat) accumulated nearly three times more MlB than lean fish (<2%j. Purging fish in MlB-free water indicated that leaner fish depurate faster (8 h) than fatter fish (48 h). Fat content had more influence in determining the time for return ts acceptable flavor than initial MIB concentration. Managing catfish production ts harvest leaner fish could minimize the impact of off-flavor on fish producers.Des barksues de riviPre (Ictalerrus punctatus) presentant diffbrentes teneurs tissulaires en graisses (de 0,s 2 11,0%) snt ete detenues dans de l'eau contentant environ 0,s pglL du compose 2-m6thylssborn&1I (MlB) generant une saveur desagreable pendant differentes pkrisdes. Une nouvelle methsde analytique a 6t6 mise au point pour quantifier la charge tissulaire en MIB. On a not6 chez les psisssns une biocowcentratisn significative de MIB aprPs 2 k et un kquilibre 21 24 h. Les p~issons plus gras (graisse musculaire > 2'5%) ont accumul6 pr6s de trois fois plus de MIB que les poissons maigres (< 2%). La purge des poissons dans de l'eau ne contenant pas de MIB a Indiquk que les poissons plus maigres detoxifient plus rapidement (8 k) que les psisssns plus gras (48 h). La teneur en graisses a eu plus d'influence pour detern-liner le temps requis jusqu'au retsur 2 une saveur acceptable que la concentration de MIB initiale. La gestisn de la production de Ia barbue de riviere avec capture des poissons plus maigres seulement pourrait minimiser I'impact de la saveur di2sagr6able sur les prsducteurs de poisssn.
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