Full text
| |
| Author(s): |
Carolina Correia Siliprandi
Total Authors: 1
|
| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto Oceanográfico (IO/DIDC) |
| Defense date: | 2009-11-06 |
| Examining board members: |
Carmen Lucia Del Bianco Rossi Wongtschowski;
June Ferraz Dias;
Antonio Olinto Avila da Silva
|
| Advisor: | Carmen Lucia Del Bianco Rossi Wongtschowski |
| Abstract | |
The beardfish Polymixia lowei is a demersal species which lives in the outer continental shelf and upper slope of the continents and islands of the Western Atlantic Ocean. In Brazilian waters, it is considered a potential resource since the early 70s and now a component of the list of species submitted to the fishing fleets operating with bottom trawling. Considering the need of biology studies for the species, its age and growth were studied, providing information for the evaluation and management of its stock. The analyzed sample comprised 2171 specimens collected during the exploration cruises of fishing with bottom-trawl nets (REVIZEE Program) in 2001 and 2002. The otoliths of 403 fishes (52 mm < Ls < 227 mm), were submitted to cutting techniques (horizontal axis), and the number of rings carried out under stereomicroscope. The time of rings deposition was analyzed through the frequency of translucent/opaque edge zones and marginal increment along the year. In order to estimate the growth parameters of von Bertalanffy model, Ford-Walford method was applied to the data of average length at age. The otoliths analyses revealed six rings (nucleus + R1 to R6), that showed the following averages: Nucleus = 1,56; R1 = 1,94 mm, R2 = 2,51 mm, R3 = 3,05 mm, R4 = 3,57 mm, R5 = 4,01 mm e R6 = 4,48 mm. The ring formation is annual, occurring at the end of autumn beginning of winter (june/july), and specimens with one to six years was found. The parameters obtained with von Bertalanffy model were: Ls = 301*[ 1 e 0.13 (t (-2.33)] (all specimens), Ls = 257 *[ 1 e 0.19 (t (-1.75) ] (males), Ls = 340 *[ 1 e 0.13 (t (-1.84) ] (females). P. lowei is a k strategist species showing slow growth and long life cycle and reaching until twenty years old. The results are consistent with the lengths observed in the sample of P. lowei, describing adequately the species growth and providing adequate information to its stock assessment and its fishery management in the Southeast-South of Brazil. (AU) | |