Evaluación del rendimiento pesquero potencial de la República Argentina: III. Edad y crecimiento de peces 1

Age and growth of populations of three fish species from sixteen lakes and reservoirs situated in the Patagonian Andean and the Patagonian Plateau Region (Argentina) were studied. They included two native species, the Patagonian smallmouth perch. (Percichthys trucha) and the Patagonian silverside (Patagonina hatcheri) and the introduced rainbow trout (Oncorhynchus mykiss). For the three species backcalculated lenght at age was obtained from scale readings. Von Bertalanffy growth curves were usually adjusted to data. For the three species, faster growth was related with lake productivity. (Document contains 38 pages.)

Edad de la trucha arco iris (Salmo gairdneri) de la laguna Zeta (Prov.de Chubut)

Age of a population of rainbow trout (Salmo gairdneri) from a pond in Patagonia was studied by means of scale readings. The population was sampled three times, on December 1984, March 1985 and March 1986. Length at age was back-calculated from growth marks on scales, using the Fraser-Lee equation. By the analysis of length distributions and numbers of marks on scales from each sample, it was concluded that this population was formed by a single cohort, born in spring 1982 and stocked shortly after. Stocking rate is unknown. Significant differences (P0.05) were found between back-calculations of length at age 1 from samples of December 1984 and March 1986. These differences were probably due to length-scale radius relation. Evidences from scales suggested that a single mark is formed each year, during early-mid spring. On the other hand, according to availabe data from the literature for the same species, this population has presented one of the highest growth rates. (pdf contains 15 pages)

Growth, movement, and attrition of northern bluefin tuna, Thunnus thynnus, in the Pacific Ocean, as determined by tagging

ENGLISH: The growth of northern bluefin tuna is described by a two-stanza model. For fish between 191 and 564 mm in length the Gompertz curve, with values of 581 mm and 4.32 for Loo and K (annual), respectively, is used. The fish between 564 and 1530 mm grow linearly, at the rate of 0.709 mm per day. Age-O fish tagged and released in the western Pacific Ocean have been recaptured in the western, central, and eastern Pacific. The minimum time between release in the western Pacific and recapture in the eastern Pacific is 215 days. Older fish, mostly Land 2-year olds, tagged and released in the eastern Pacific have been recaptured in the eastern and western Pacific. The minimum time between release in eastern Pacific and recapture in the western Pacific is 674 days. The coefficient of natural mortality is estimated from data on growth and ambient temperature to be 0.276 on an annual basis, with 90-percent confidence limits of 0.161 and 0.47L Spawning of northern bluefin takes place only in the western Pacific. Some of the juveniles migrate to the eastern Pacific, where they reside for several months to several years before returning to the western Pacific. The portion of fish which migrate to the eastern Pacific varies among years, and this appears to be an important cause of the annual variation in the catches in the eastern Pacific Ocean. SPANISH: El crecimiento del atún aleta azul del norte es descrito por un modelo de dos estadios. Para los peces de entre 191 y 564 mm de talla se usa la curva de Gompertz, con valores de 581 mm y 4.32 para Loo y K (anual), respectivamente. Los peces de entre 564 y 1530 mm crecen de forma lineal, a 0.709 mm por día. Peces de edad Omarcados y liberados en el Pacífico occidental han sido recapturados en el Pacífico occidental, central, y oriental. La demora mínima entre la liberación en el Pacífico occidental y la recaptura en el Pacífico oriental es de 215 días. Peces mayores, principalmente de 1 ó 2 años de edad, marcados y liberados en el Pacífico oriental han sido re capturados en el Pacífico occidental y oriental. La demora mínima entre la liberación en el Pacífico oriental y la recaptura en el Pacífico occidental es de 674 días. Se estima el coeficiente de mortalidad natural a partir de los datos de crecimiento y temperatura ambiental en un 0.276 anual, con límites de confianza al 90% de 0.161 y 0.471. El aleta azul del norte desova únicamente en el Pacífico occidental. Algunos de los juveniles migran al Pacífico oriental, donde permanecen entre varios meses y varios años antes de regresar al Pacífico occidental. La porción de los peces que migran al Pacífico oriental varía entre años, y ésto parece ser una causa importante de la variación anual en las capturas en el Océano Pacífico oriental. (PDF contains 94 pages.)