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Browsing by Author "Alves, Adriana"

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  • Age and growth of the blue jack mackerel, Trachurus picturatus Bowdich, 1825 (Pisces: Teleostei) off Madeira archipelago
    Publication . Vasconcelos, Joana; Alves, Adriana; Gouveia, Elisabete; Faria, Graça
    Between 1984 and 1986, 630 pairs of sagitta otoliths were collected to determine the age and growth of the blue jack mackerel, Trachurus picturatus from Madeiran waters. The oldest specimen in this study was nine years old and the largest was 46 cm of total length (TL). The parameters of the von Bertalanffy growth curve were estimated for the whole period studied for all fish (L∞=42.32 cm, k=0.161 year-1, t0= -2.563 year; r2=0.743) for males (L∞=39.57 cm, k=0.194 year-1, t0=-2.282 year; r2=0.722) and for females (L∞=49.78 cm, k=0.114 year-1, t0=-3.052 year; r2 = 0.747). There was no significant differences in mean lengths (t–test, p>0,05) and in the von Bertalanffy growth curves (F test, p>0,05) between sexes. The validity of otolith readings for estimating age and growth was supported by results from backcalculation method. No significant differences were found in the Bertalanffy growth curves between direct reading of otoliths and backcalculation. Growth parameters estimated from backcalculated sizes-at-age were: for both sexes, L∞=48.28 cm, k=0.135 year-1, t0=-2.898 year and r2=0.999; for males, L∞=44.79 cm, k=0.143 year-1, t0=-3.207 year, r2=0.999; and females, L∞=44.63 cm, k=0.163 year-1, t0=-2.430 year, r2=0.999. The relationship between length and weight was calculated for all fish (Wt=0.00764Lt3.05746; r2=0.951), for males (Wt=0.01271Lt2.90807; r2=0.915) and for females (Wt=0.00604Lt3.12613; r2=0.948).
    2006Journal article Open access Show more
  • Age and growth of the pink dentex Dentex gibbosus (Rafinesque, 1810) caught off the Madeira Archipelago
    Publication . Alves, Adriana; Vasconcelos, Joana
    A total of 146 otoliths were extracted for age readings from 68 females (23.2-90.1 cm TL), 76 males (22.0-81.3 cm TL) and 2 undetermined (30.3-38.0 cm TL), between April 2004 and December 2007. The maximum age obtained from whole otoliths was 11 years. Differ ences in the growth rhythms were observed between the sexes (females: L∞=134.4, K=0.092 and t0=−0.406; males: L∞=135.9, K=0.078 and t0=−0.894; and all fish were: L∞=149.8, K=0.078 and t0=−0.784). Pink dentex attain 50% of their maximum theoretical length during their fourth year of life. The weight-length relationship (W = q Lfb) were de termined separately for each sex and for all fish: for females q=0.01094 and b=3.033, for males q=0.10002 and b=3.047 and for all, q=0.01027 and b=3.046. According to the F-test, there were no significant differences between the weight-length relations obtained for fe males and males (F-test, F=2.2526, p=0.06646).
    2013Journal article Open access Show more