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Abstract(s)
This dissertation aims to study the impact of commercial purse seine fishing operations
on slipped sardines (Sardina pilchardus), accounting for the survival rates of the
escapees and studying the main factors/stressors that may lead to delayed mortality.
Field work onboard commercial seiners allowed to study the early dynamics of sardine
(Sardina pilchardus) stress reactions and identify likely stressors during fishing
operations. Appropriate methodology for capturing, transporting and maintaining
sardines in captivity after live capture was optimized in order to use the species for
laboratory fishing simulation studies. Laboratory fishing simulations were used to study
some operational and environmental factors that lead to variable physical, physiological
and behavior responses and result in delayed mortality after slipping. Results showed
variable stress responses of sardines during purse seining operations with the significant
effect of fishing duration in several physiological blood parameters (cortisol, glucose,
haematocrit, haemoglobin, ionic balance, and ATP and its metabolites). Laboratory
fishing simulations revealed that survival rates decrease significantly with time inside
the net, with temperature having an additional effect on mortality. Fish short term stress
responses (physiological) immediately after fishing do not correlate with observed
delayed mortality. Scale loss is an important variable of physical injury directly related
with the probability of dying. Long term stress responses such as the inhibition of the
immune and reproductive systems affects all escapees (whether surviving or not).
Sardine suffer behavioral impairments such as lower swimming speed, shorter predator
approaches and larger nearest neighbor distances (wider school area) regardless of
fishing stressor severity, what indirectly may increase their vulnerability to predation.
Description
Tese dout., Ciências e Tecnologias das Pescas, Universidade do Algarve, 2009
SFRH/BD/23053/2005 (FCT)
SFRH/BD/23053/2005 (FCT)
Keywords
Teses Sardinha Sardina pilchardus Pesca de cerco