Seasonal changes in otolith increment width trajectories and the effect of temperature on the daily growth rate of young sardines

Abstract

We studied the otolith microstructure and growth of sardine, Sardina pilchardus, in the North Aegean Sea (eastern Mediterranean Sea), using samples of larvae and juveniles that had hatched in winter (NovemberJanuary) and winter-spring (February-May), respectively. The juveniles had developed during an extended period coinciding with marked pelagic ecosystem changes (from winter, mixed conditions to summer, stratified waters). To examine the relationship between environmental changes and the observed variability in their otolith increment-width trajectories (width-at-age), we summarized the shape of trajectories with a four-parameter set estimated from a growth model fit to each width trajectory. The individual parameter sets were then related to the potential oceanographic conditions that fish experienced during their development, derived from a hydrodynamicbiogeochemical model (POM-ERSEM), implemented in the sampling area. Substantial seasonal effects were demonstrated on the otolith microstructure (platykurtic versus leptokurtic trajectories in winter-mixed versus summer-stratified conditions), which were related to the progressive sea surface warming. In a subsequent step, in order to study the effect of oceanographic conditions on larval and juvenile daily growth rates, a GAM (Generalized Additive Model) analysis of otolith increment widths was carried out, using modelderived oceanographic parameters and taking into account the 'inherent otolith growth', expressed by the explanatory variables 'previous increment width' and 'Age'. Results showed a strong and positive, linear effect of temperature on the growth rate of wintercaught larvae, whereas in juveniles, which had developed within a wide range of temperatures, an optimum temperature for growth was observed at around 24°C.

Spawning stock, egg production and larval survival in relation to small pelagic fish recruitment

“…the length at metamorphosis, decreases with temperature (Fuiman et al 1998), and morphological transitions are more abrupt and synchronized among traits at higher temperatures (Nikolioudakis et al 2014b). This is, for example, evident in the otolith growth pattern, which changes from increasing to decreasing increment widths during metamorphosis: increment width trajectories are more 'leptokurtic' at high temperatures and 'platykurtic' at low temperatures (Schismenou et al 2016).…”

“…In the eastern Mediterranean, Schismenou et al (2014Schismenou et al ( , 2016 studied the effect of temperature and other ecosystem parameters on the daily growth rate of European anchovy and European sardine in the field using otolith microstructure analysis and simulations of a hydrodynamic-biogeochemical model. Using a statistical modelling approach that accounted for the uncoupling of otolith and somatic growth (the 'inherent otolith growth'), they found that the co-occurring species had the same temperature optima for early growth, at about 24.5°C.…”

Strong evidence for changing fish reproductive phenology under climate warming on the Tibetan Plateau

“…The number of daily increments is largely determined by the length of the growing season, while the width of daily increments is highly associated with the environmental temperature (Ding, 2012). In natural systems, particularly those very sensitive to global warming (e.g., Siling Co), temperature could be the main factor affecting daily increment width of fish otolith, and potentially incorporated with other factors such as food resources (Campana & Neilson, 1985;Schismenou et al, 2016;Wenger, Whinney, Taylor, & Kroon, 2016). However, it is almost impossible to retrieve data of historical food availability of G. selincuoensis each year, which relies on long-term and continuous monitoring on food resources.…”

Effect of temperature on the growth, survival, development and foraging behaviour of Sardina pilchardus larvae

“…Thermal tolerance is expected to increase as fish grow up to the juvenile and adult stages. A recent work conducted in the Mediterranean Sea (Schismenou et al 2016) has found that larvae occurred in areas of SST ranging from 13 to 17°C, and a linear and positive relationship of sardine larvae growth rate was found with temperature. In contrast, sardine juveniles developed in a wider range of temperatures (12−27°C) and had a dome-shaped growth response, with an optimum at around 24°C.…”