Increasing biological knowledge for better management of by-catch species: age, growth, and mortality of piper and red gurnards (Teleostei: Triglidae) |
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Vera Sequeira, Inês Sousa, Ana Neves, Ana Rita Vieira, Elisabete Silva, Frederica Silva, Ana Marta Duarte, Susana Mendes, Rui Ganhão, Carlos Alberto Assis, Rui Rebelo, Maria Filomena Magalhães, Maria Manuel Gil, Leonel Serrano Gordo |
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Gurnards
are a valuable by-catch of mixed demersal fisheries and are
commercially important in European waters, but they are often discarded,
reported under “mixed gurnards” and with incomplete biological
information by species. In the present work, a total of 558 piper
gurnard specimens of between 10.9 and 44.4 cm (1 to 11 years) and 425
red gurnard specimens of between 10.2 and 42.1 cm (0 to 9 years) from
the northeast Atlantic (Portuguese) coast were used to study age and
growth. The von Bertalanffy growth parameters for piper gurnard were
estimated through the combination of whole-otolith readings and
back-calculation (L∞=44.7 cm, k=0.16 yr-1 and t0=-2.781 yr). For red gurnard the same growth parameters were estimated using whole-otolith readings (L∞=40.2 cm, k=0.28 yr-1 and t0=-1.074
yr). The results indicate that the red gurnard reaches a smaller
length, although it grows faster than the piper gurnard. Natural,
instantaneous and fishing mortalities were estimated as well as the
exploitation rate for both species. For the Portuguese coast, the red
gurnard showed a higher fishing mortality and exploitation rate than the
piper gurnard, raising concerns about its sustainable management. |
Keywords: by-catch; age determination; growth curves; fishing mortality; longevity; Chelidonichthys cuculus; Trigla lyra |
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