Age, growth and demographic of the Guitarfishes, R... - BV FAPESP
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Age, growth and demographic of the Guitarfishes, Rhinobatos horkelli, Rhinobatos percellens and Zapteryx brerostris in the continental shelf of São Paulo

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Author(s):
Fabio Prior Caltabellotta
Total Authors: 1
Document type: Doctoral Thesis
Press: Botucatu. 2015-03-03.
Institution: Universidade Estadual Paulista (Unesp). Instituto de Biociências. Botucatu
Defense date:
Advisor: Otto Bismarck Fazzano Gadig; Debra Jean Murie
Abstract

Guitarfishes (Elamobranchii, Rhinobatiformes) are usually components of the multispecific fishery as by-catch of double-rig, pair and single bottom trawls in the southeast and south of Brazil (Martins & Schwingel, 2003). Considering the lack of life history parameters on the age and population structure studies of these species there is therefore a need for research to enable a proper assessment of the condition of these stocks. We evaluated the structure and the capacity of population growth in the State of São Paulo continental shelf, using the estimated growth and demographic parameters. Were available for this study, 149 samples of Rhinobatos horkelli, 752 samples of Rhinobatos percellens and 952 samples of Zapteryx brevirostris.A sub-sample were used for the age and growth study. The best model that describes the growth of the species was the three parameters von Bertalanffy growth function. Estimated parameters were : L?=121.71 , k =0.21, and t0 = -1.34 for Rhinobatos horkelli (grouped sex), L? = 106.99 , k = 0.17 and t0 = -1.51 for Rhinobatos percellens (female) , L? = 90.69 , k = 0:24 and t0 = -1.36 for Rhinobatos percellens (male), L? = 60.73 , k = 0.23 and t0 = - 1.44 to Zapteryx brevirostris (female) and L? = 57.88 , k = 0.26 and t0 = -1.29 for Zapteryx brevirostris (male). Centrum edge analysis and marginal increment suggests the formation of one band-pair (opaque and translucent) per year. The formation of the translucent band should occour from late winter to the end of the spring. Five scenarios were evaluated for estimated the intrinsic rate of population growth. According to the results obtained under natural mortality conditions and in the absence of fishing, population trends of Rhinobatos horkelli showed a increase about 9% per year, Rhinobatos percellens about 10% per year and Zapteryx brevirostris 3.9% per year. When were considered scenarios with the presence of fishing, all species ... (AU)

FAPESP's process: 10/02397-7 - Population dynamics of the guitarfishes Rhinobatos horkelli, Rhinobatos percellens and Zapteryx brevirostris (Chondrichthyes, Rhinobatidae)of the Sao Paulo Continental Shelf, Brazil
Grantee:Fabio Prior Caltabellotta
Support Opportunities: Scholarships in Brazil - Doctorate