Temporal variability of larval growth, size, stage duration and recruitment of a wrasse, <i>Coris julis</i> (Pisces: Labridae), from the Azores

Abstract

SUMMARY: Temporal variability in the size at settlement (SAS), age at settlement (PLD), larval growth and recruitment patterns of a temperate wrasse, Coris julis, were examined over two recruitment seasons for a single island site from the Azores archipelago in the northeastern Atlantic. Relationships between these early life-history traits and recruitment variability over time were also investigated. Average PLD and SAS varied significantly among sampling dates over the settlement season, increasing consistently over time. This pattern was persistent over two consecutive summers. Larval growth was not a good predictor for PLD or SAS, which were in turn positively correlated with each other. Differences in recruitment magnitude over time were not related to SAS, PLD or larval growth. Instead, we found that recruits whose early pelagic stage (first 30 d) overlapped part of a period of enhanced growth (above average and independent of larval age), tended to result in the largest recruitment events; these tended to occur in the mid season. Larvae from earlier and later settlement events, overlapping periods of depressed growth, were linked to more modest recruitment events. We hypothesize that short PLD, with resulting small SAS is favoured early in the season, when post-settlement density is lowest. Over the course of the settlement season, as recruits accumulate competition may increase, and larger SAS (associated with longer PLD), may provide a competitive/survival advantage.Keywords: Coris julis, Azores, seasonal patterns, larval growth, recruitment.RESUMEN: Variabilidad temporal del crecimiento, talla y duración larvaria, y reclutamiento de un lábri-do , Coris julis (Pisces: Labridae), de las Azores. -La variabilidad temporal en la talla de reclutamiento (SAS), edad de reclutamiento (PLD), crecimiento larvario y patrón de reclutamiento en un lábrido de aguas templadas, Coris julis, fueron examinados en dos épocas de reclutamiento consecutivas, en una isla de las Azores (Atlántico nordeste). Se examinaron también las relaciones entre estas características y la variabilidad de reclutamiento temporal. La PLD y la SAS medios aumentaron significativamente a lo largo del período de reclutamiento en los dos veranos consecutivos. La PLD y la SAS se correlacionaron positivamente, pero el crecimiento larvario no fue un buen predictor de estas características. Las diferencias en magnitud de reclutamiento entre fechas de muestreo sucesivas no fueron explicadas por las SAS/PLD medias, ni tampoco por el crecimiento larvario. En cambio, encontramos que los reclutas cuyos primeros estadios de desarrollo pelágico (30 días) se solapaban, en parte, con un periodo de crecimiento intenso (por encima del promedio e independiente de de edad) resultaron en los mayores reclutamientos; que tienden a suceder a mitad de la estación. Las larvas de asentamientos tempranos o tardíos (periodos de solapamiento, con crecimiento disminuido), se asociaron a reclutamientos modestos. Se plantea la hipótesis de que las PLD cortas, con las resultant...

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“…In addition to this potential effect of larval density, an effect of settler density could also affect PLD: in a site with low settler density, larvae could 'choose' to settle as soon as they can (which results in a short PLD) in order to minimize larval mortality, since the resulting small size at settlement could be further compensated by faster juvenile growth with reduced intraspecific competition (Fontes et al 2010). On the other hand, at a higher settler density, settlement at a bigger size (resulting in a longer PLD, Denit & Sponaugle 2004, Fontes et al 2011 will increase the capability of escaping predators and successfully competing for shared resources (Tupper & Boutilier 1995, McCormick 1999, despite having a higher larval mortality (Fontes et al 2010). From this perspective, PLD could be the outcome of a trade-off among different pre-post settlement 'requirements' (Cowen & Sponaugle 1997) aimed at maximizing chances of settling under optimal conditions (Sponaugle & Cowen 1994).…”

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