|Determination of age and growth of Galeus melastomus, Rafinesque, 1810, a deep water shark, using a modified cobalt nitrate technique|
Baptista, M. (2010). Determination of age and growth of Galeus melastomus, Rafinesque, 1810, a deep water shark, using a modified cobalt nitrate technique. MSc Thesis. University of Algarve, Faculty of Marine and Environmental Sciences/Erasmus Mundus Master of Science in Marine Biodiversity and Conservation (EMBC): Faro. 44 pp.
University of Algarve; Faculty of Marine and Environmental Sciences (FCMA), more
|Available in|| Author |
- VLIZ: Archive VLIZ ARCHIVE A.THES2 
- VLIZ: Non-open access 230615
|Document type: Dissertation|
Age determination; Growth; Modelling; Population dynamics; Galeus melastomus Rafinesque, 1810 [WoRMS]; Marine
The deepwater blackmouth catshark, Galeus melastomus, is captured as by-catch by deep water bottom trawlers targeting crustaceans and deep water longliners targeting teleosts. Most catches have little or no commercial value and are therefore discarded, but larger individuals are marketable. In Portugal, an increase in landings of G. melastomus has been observed over the past 25 years. Vertebrae from this species are poorly calcified, rendering common band enhancement techniques useless. Different sectioning methods and band enhancement techniques were evaluated in order to determine the most efficient methodology for ageing G. melastomus using its poorly calcified vertebrae. A new, simple, rapid and inexpensive methodology using 500 µm vertebrae sections and a modification of the cobalt nitrate technique yielded the best results. Age and growth estimates for the southern coast of Portugal were obtained from 189 vertebrae extracted from specimens ranging from 13 to 71 cm total length and compared to those presented in the only study performed to this date on age and growth of this species. Maximum age estimates of 14 and 17 years were obtained for males and females respectively but could not be validated. Four growth models were fitted and compared for length-at-age data, showing that even though this is a small sized species, it has a relatively slow growth rate. The new methodology for band visualization may be used on other species exhibiting poorly calcified vertebrae.