Therefore, there appears to be a relevant association between the NAO and migrating
tuna in the Alboran Sea.
17.4 The NAO and Tuna Fisheries in the Alboran Sea
In the case of migrating tunas in the Alboran Sea, the NAO may have a direct effect
on the physical condition of the fish. Thus, Báez et al. (2013) in the case of
prereproductive bluefin tuna; Muñoz-Expósito et al. (2017), in the case of bullet
tuna; and Báez et al. (2019), in the case of little tunny and Atlantic bonito, have
shown the existence of a relationship between an improved physical condition and
positive phases of the NAO. Thus, in positive phases of the NAO, the physical
condition of fish migrating to spawning grounds in the Mediterranean Sea is
improved due to an increase in the prevalence of strong westerly winds, mediated
by a positive AO or NAO, favoring the migration by reducing energy costs and by
increasing the supply of nutrients (Báez et al. 2013; Muñoz-Expósito et al. 2017).
Likewise, this physical condition improvement may lead to a higher gonadosomatic
index (GSI) level in reproductive females (Báez et al. 2019).
17.5 Conclusions
NAO index plays a fundamental role in the biology of migrating tunas in the Alboran
Sea, both improving the physical condition and reproductive potential. Thus, thanks
to better climate conditions during pre-spawning migration, females can use more
energy resources for reproduction, thereby improving the gonadosomatic index
(GSI) levels. Moreover, recent studies show that a higher GSI female level increases
larvae survival of some tuna species (Reglero et al. 2018; Hiraoka et al. 2019).
Currently, there are evidences of an abrupt global warming, an expected effect of
climate change, and most likely leading to extreme climate oscillations. Extreme
phases of short-term climate oscillations, such as the NAO, can lead to rapid and
sudden weather responses including floods and droughts and extreme temperatures
such as heat and cold waves (Vicente-Serrano et al. 2011). This combination of
extreme phases could have adverse effects on the biology of migrating tunas, in such
a way that it could affect reproductive success and therefore recruitment.
Finally, it is important to stress that climate oscillations may also have great
effects on catchability and first sale price variability of fish, as recently shown by
Fernández et al. (2020).
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J. C. Báez et al.
tuna in the Alboran Sea.
17.4 The NAO and Tuna Fisheries in the Alboran Sea
In the case of migrating tunas in the Alboran Sea, the NAO may have a direct effect
on the physical condition of the fish. Thus, Báez et al. (2013) in the case of
prereproductive bluefin tuna; Muñoz-Expósito et al. (2017), in the case of bullet
tuna; and Báez et al. (2019), in the case of little tunny and Atlantic bonito, have
shown the existence of a relationship between an improved physical condition and
positive phases of the NAO. Thus, in positive phases of the NAO, the physical
condition of fish migrating to spawning grounds in the Mediterranean Sea is
improved due to an increase in the prevalence of strong westerly winds, mediated
by a positive AO or NAO, favoring the migration by reducing energy costs and by
increasing the supply of nutrients (Báez et al. 2013; Muñoz-Expósito et al. 2017).
Likewise, this physical condition improvement may lead to a higher gonadosomatic
index (GSI) level in reproductive females (Báez et al. 2019).
17.5 Conclusions
NAO index plays a fundamental role in the biology of migrating tunas in the Alboran
Sea, both improving the physical condition and reproductive potential. Thus, thanks
to better climate conditions during pre-spawning migration, females can use more
energy resources for reproduction, thereby improving the gonadosomatic index
(GSI) levels. Moreover, recent studies show that a higher GSI female level increases
larvae survival of some tuna species (Reglero et al. 2018; Hiraoka et al. 2019).
Currently, there are evidences of an abrupt global warming, an expected effect of
climate change, and most likely leading to extreme climate oscillations. Extreme
phases of short-term climate oscillations, such as the NAO, can lead to rapid and
sudden weather responses including floods and droughts and extreme temperatures
such as heat and cold waves (Vicente-Serrano et al. 2011). This combination of
extreme phases could have adverse effects on the biology of migrating tunas, in such
a way that it could affect reproductive success and therefore recruitment.
Finally, it is important to stress that climate oscillations may also have great
effects on catchability and first sale price variability of fish, as recently shown by
Fernández et al. (2020).
584
J. C. Báez et al.