Distribution of nursery areas of Merluccius merluccius obtained by geostatistical techniques
1998
Lembo, G. | Spedicato, M.T. | Silecchia, T. (Coispa Tecnologia e Ricerca, Mola di Bari (Italy)) | D'Agostino, V. (Tecnopolis, Valenzano (Italy))
This paper aims to assess the abundance of recruits and localize the nursery areas in order to provide useful information for fisheries management. The data were collected in the central-southern Tyrrhenian Sea during the bottom trawl survey carried out in the summer 1996, as part of Medits-it programme. The fraction of length frequency distribution lower than 12 cm was used. The variables under investigation were the number of juveniles and depth, they were used to construct the experimental auto and cross-variograms. The models which best describe the spatial continuity were detected by structural analysis. After the structural analysis the estimated value of the given variable was obtained by applying the co-kriging techniques. The conditioned probability of exceeding a given threshold value of the variable number of juveniles was estimated by disjunctive kriging techniques. Different types of maps were generated, which represented the localization of nursery areas, the estimation variance of the investigated variable and the conditioned probability of finding an abundance index higher than 300 individuals per hour.
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