Otolith Microstructure in Young-of-the-Year Dolly Varden, Salvelinus Malma, from American and Asian Populations: Resolution of Comparative Life History Characteristics

• Published in: Arctic 1996-06, Vol.49 (2), p.162-169
• Main Authors: Radtke, R. L., Fey, D. P., Decicco, A. F., Montgomery, A.
• Format: Article
• Language: English
• Subjects: Anadromous fishes; Climatic conditions; Environment; Environmental conditions; Feeding; Fish; Fish eggs; Fisheries science; Freshwater; Freshwater fishes; Growth rate; Hatching; Life history; Light microscopy; Marine; Marine fishes; Otolith organs; Otoliths; Overwintering; Population growth; Population growth rate; Rivers; Salmon; Salvelinus malma; Spawning; Summer; Trout; Water temperature; Young animals
• ISSN: 0004-0843; 1923-1245
• DOI: 10.14430/arctic1194

Sagittal otoliths from young-of-the-year Dolly Varden, Salvelinus malma, captured from Cripple River, Alaska and Cha'atam River, Russia were prepared and observed with transmitted light microscopy. Distinct microstructure in samples from both locations indicated daily growth increments, hatching checks and first feeding checks that confirm literature findings in other salmonids. We used increment counts to estimate the ages of individual juveniles and calculated hatch dates and times of first feeding from those ages. Increments deposited before the first feeding mark were significantly smaller then those formed after this mark. Alaskan and Russian fish showed a significant difference in hatching times and the period of first feeding. Summer growth rates of the Russian population, calculated from length-at-age data, were faster (0.356 mm-day⁻¹) than those of the Alaskan population (0.301 mm-day⁻¹). However, when the average growth rate was calculated with the formula GR = ${\rm{(L}}_{{\rm{capture}}} {\rm{ - }}{\rm{L}}_{{\rm{hatching}}} {\rm{)}}$/age, the values were higher for the Alaskan population (0.25 mm-day⁻¹) than for the Russian population (0.20 mm-day⁻¹). When otolith radius-fish size relationships were estimated, Alaskan otoliths were found to be larger for the same size fish, because wider increments were deposited in fish from Alaska. Increment width also was related to time of the year: wider increments were deposited during the warmer months. Otolith microstfucture provided insights into the early life history of young-of-the-year Dolly Varden from American and Asian populations. /// /// Des sagittas provenant de Dolly Varden (Salvelinus malma) de l'année capturées dans la Cripple en Alaska et dans la Cha'atam en Russie ont été préparées et étudiées au microscope pour examen par transmission. Une microstructure distincte dans les échantillons provenant des deux sites révélait une croissance quotidienne, des repères de l'éclosion et des repères de la première phase alimentaire, qui confirment les résultats consignés dans la documentation sur d'autres salmonidés. On s'est servi du comptage des unités d'accroissement pour estimer l'âge des individus juvéniles et on a calculé la date d'éclosion et la date de la première phase alimentaire à partir de cet âge. Les unités d'accroissement formées avant le repère signalant le début de la phase alimentaire étaient nettement moindres que celles qui se sont formées après ce repère. Les poissons d'Alaska et