ABSTRACT

Chrousos (1998) has defi ned stress “as a state of threatened homeostasis, which is reestablished by a complex repertoire of physiologic and behavioral adaptive responses of the organism”. Thus stress is only a bad thing if the adaptive responses are inadequate for reestablishing homeostasis or are excessive and prolonged, and if a healthy steady state is not attained, in which case pathology may result. In fi shes, stress can negatively impact growth, health, reproduction, and welfare and ultimately result in mortality, which is of relevance in aquaculture and in wild populations, where stress can also shape the composition of fi sh communities. Since there are already a number of comprehensive reviews on stress physiology in fi shes that include general-whole animal (e.g., Sumpter 1997, Wendelaar-Bonga 1997, Barton and Iwama 1991, Barton 2002), ontogeny (Nesan and Vijayan 2012), specifi c aspects of physiology [metabolism (Mommsen et al. 1999, van der Boon et al. 1991), osmoregulation (McCormick 2001), immune system (Tort 2011, Weyts et al. 1999), reproduction (Leatherland et al. 2010, Milla et al. 2009, Schreck 2010), feeding and growth (Bernier and Peter 2001, van Weerd and Komen 1998)] and the cellular stress response (e.g., Iwama et al. 2004, Kultz 2005), the focus of this chapter will be to be eel-centric. There is a

Ecofi siologia, Centre for Interdisciplinar Marine and Environmental Research (CIIMAR) Porto, Portugal. E-mail: wilson.jm.cimar@gmail.com

rich literature on the use of eels as an experimental animal that spans from pioneering work on elucidating basic neuroendocrine mechanisms (e.g., pituitary-interrenal axis, Maetz 1969) to the application of stress physiology in fi eld studies to assess population health (Geeraerts and Belpaire 2010). Compared to other teleost fi shes eels are generally very tolerant of various environmental stressors (temperature, hypoxia, hypercapnia, ammonia and pH; e.g., Cruz-Neto and Steffensen 1997, Sadler 1981, McKenzie et al. 2003), and can be found in environments that are polluted or have poor water quality; however, their complex and often mysterious life-history strategy makes them vulnerable at crucial stages in their life cycle (Robinet and Feunteun 2002, Geeraerts and Belpaire 2010).