and is continuously being updated with new applications, as otolith asymmetry. It
has been shown that larval trophodynamics are strongly relevant for enhancing daily
growth (Pepin et al. 2015). Studies of the trophic transfer of C and N from
phytoplankton to zooplankton and ichthyoplankton by determining the isotopic
composition (
13 C and
15
N) of different size fractions revealed that sardine and
anchovy larvae modify their diet depending on the quality or the type of food
available, namely, the phytoplankton and/or zooplankton groups present (Uriarte
2010; Laíz-Carrión et al. 2011; Quintanilla et al. 2015; Quintanilla 2016). Further
findings show that the stable isotope of nitrogen (δ
15 N) showed a linear relationship
between faster- and slower-growing individuals with the average values of δ
15 N by
daily age class. This link was further corroborated on the species Auxis rochei from
the Balearic Sea. Two cohorts of this species originating from two hydrographically
different water masses showed differentiated growth patterns in which enhanced
growth was linked to greater δ
15 N values (Laíz-Carrión et al. 2013).
With respect to anchovy, a comparison between the NW Mediterranean anchovy
and Alboran Sea anchovy stable isotope analysis linking larval growth study showed
that the NW Mediterranean anchovy population showed specialized prey selectivity
associated with a low productive ecosystem in contrast to the Alboran Sea population, which showed a more generalist feeding behavior associated with an ecosystem
of higher food resources. The differences between ecosystems were shown by the
significant differences in the δ
13 C values indicating differences in the carbon sources
of each larval habitat (Uriarte 2010). Higher growth rates recorded greater δ
15 N
values, thereby a higher trophic position which indicates a greater feeding specialization in larvae originating in less productive regions (Uriarte 2010; Quintanilla
et al. 2015). From the population viewpoint, differences in the amino acid composition of anchovy egg and larvae further corroborated stock differentiation (Riveiro
et al. 2003).
A similar study comparison was carried out in the Alboran Sea sardine which has
nursery grounds in widely distinct environmental characteristics, the bays of Almeria
and Malaga, being the former distinguished by its lower productivity consequent
with the less influence of the Atlantic current (Quintanilla et al. 2020). While δ
15
N
values were conditioned by the seasonal plankton community structure particular to
each nursery area, trophic levels are influenced by larval trophodynamics. In this
case, higher somatic and otolith biometric growth was related to higher trophic levels
due to the higher enrichment of larvae from their potential feeding resources.
Recently, these trophic relationships have been further investigated through the
molecular characterization of the diet of Sardina pilchardus larvae in the Bay of
Malaga. The development and application of new molecular tools have allowed
detecting the presence of certain groups of phytoplankton and zooplankton in the gut
of ichthyoplanktonic larvae. For example, specific primers and a multiplex PCR
assay have been designed to target copepod species and phytoplankton groups
identified as potential preys (Hernández de Rojas et al. unpubl.), allowing us to
determine their contribution, at least qualitatively, to the diet of S. pilchardus larvae
in the nursery area (Yebra et al. 2019). Also, recent developments in highthroughput sequencing techniques have allowed the metabarcoding of the entire
512
A. García et al.
has been shown that larval trophodynamics are strongly relevant for enhancing daily
growth (Pepin et al. 2015). Studies of the trophic transfer of C and N from
phytoplankton to zooplankton and ichthyoplankton by determining the isotopic
composition (
13 C and
15
N) of different size fractions revealed that sardine and
anchovy larvae modify their diet depending on the quality or the type of food
available, namely, the phytoplankton and/or zooplankton groups present (Uriarte
2010; Laíz-Carrión et al. 2011; Quintanilla et al. 2015; Quintanilla 2016). Further
findings show that the stable isotope of nitrogen (δ
15 N) showed a linear relationship
between faster- and slower-growing individuals with the average values of δ
15 N by
daily age class. This link was further corroborated on the species Auxis rochei from
the Balearic Sea. Two cohorts of this species originating from two hydrographically
different water masses showed differentiated growth patterns in which enhanced
growth was linked to greater δ
15 N values (Laíz-Carrión et al. 2013).
With respect to anchovy, a comparison between the NW Mediterranean anchovy
and Alboran Sea anchovy stable isotope analysis linking larval growth study showed
that the NW Mediterranean anchovy population showed specialized prey selectivity
associated with a low productive ecosystem in contrast to the Alboran Sea population, which showed a more generalist feeding behavior associated with an ecosystem
of higher food resources. The differences between ecosystems were shown by the
significant differences in the δ
13 C values indicating differences in the carbon sources
of each larval habitat (Uriarte 2010). Higher growth rates recorded greater δ
15 N
values, thereby a higher trophic position which indicates a greater feeding specialization in larvae originating in less productive regions (Uriarte 2010; Quintanilla
et al. 2015). From the population viewpoint, differences in the amino acid composition of anchovy egg and larvae further corroborated stock differentiation (Riveiro
et al. 2003).
A similar study comparison was carried out in the Alboran Sea sardine which has
nursery grounds in widely distinct environmental characteristics, the bays of Almeria
and Malaga, being the former distinguished by its lower productivity consequent
with the less influence of the Atlantic current (Quintanilla et al. 2020). While δ
15
N
values were conditioned by the seasonal plankton community structure particular to
each nursery area, trophic levels are influenced by larval trophodynamics. In this
case, higher somatic and otolith biometric growth was related to higher trophic levels
due to the higher enrichment of larvae from their potential feeding resources.
Recently, these trophic relationships have been further investigated through the
molecular characterization of the diet of Sardina pilchardus larvae in the Bay of
Malaga. The development and application of new molecular tools have allowed
detecting the presence of certain groups of phytoplankton and zooplankton in the gut
of ichthyoplanktonic larvae. For example, specific primers and a multiplex PCR
assay have been designed to target copepod species and phytoplankton groups
identified as potential preys (Hernández de Rojas et al. unpubl.), allowing us to
determine their contribution, at least qualitatively, to the diet of S. pilchardus larvae
in the nursery area (Yebra et al. 2019). Also, recent developments in highthroughput sequencing techniques have allowed the metabarcoding of the entire
512
A. García et al.