Environmental Engineering Reference
In-Depth Information
cultural, management, economic, socio-political and ethical aspects) and
has proved to be useful to assess the complex responses of ecosystems to
global climate change (Perry et al. 2010a, Perry et al. 2010c).
Fishing productivity has grown rapidly from 1950 uptil 1980 when
maximum yield was reached; however, the global landings are currently
stacked and might be decreasing (FAO 2007, Dow et al. 2009). Indeed, many
commercially important fi sh populations have been declining in the past
several decades (Myers and Worm 2003, Hutchings and Reynolds 2004),
though the exact role of fi shing and environmental change as underlying
factors driving the changes is not yet clarifi ed (Hsieh et al. 2006).
The goal of this chapter is to summarize the current and future impacts
of climate-driven changes on the physiology and ecology of marine fi shes,
and how world fi sheries are responding to the observed changes. The
interaction between fi sh stocks and climate change is analyzed on the
context of human disturbance. Finally, we present three case studies of
fi sheries in South-America, illustrating the vulnerability, possible mitigation
and future perspectives in the climate change context.
Climate Change and Fishes
Effects of climate warming
Individual-level responses.
Marine organisms are capable of synchronizing
developmental, reproductive and migratory cycles to periodic climate
oscillation (Overland et al. 2010). Within climatic variables, temperature
is recognized to infl uence the fate of biochemical reactions and to dictate
the rate of almost every biological activity. Indeed, metabolism increases
exponentially with temperature, and the metabolic rate of individuals
determines the rate of resource uptake in a given habitat, which affects
the ecological processes in all levels of organization (Brown et al. 2004).
However, higher metabolic rates involve higher oxygen demand, which
in turn becomes less available as the temperature increases (Keeling et al.
2010). As a consequence, aquatic species in a warmer environment must
confront the paradox of higher tissue oxygen demand and lower habitat
oxygen saturation.
The mechanism by which seawater warming affects the physiology
and ultimately the local adaptation of fi sh species was described by Pörtner
and Knust (2007). The authors suggested that once aerobic capacity (i.e.,
the capacity of an organism to fulfi ll tissue oxygen demands) starts to
be restricted, the threshold critical temperatures are surpassed (Fig. 1).
This value might not be the same for the entire population, since smaller
specimens present a wider thermal tolerance and thus will continue to
grow after higher critical temperatures are reached. Beyond specifi c critical
