Effects of prey concentration on ingestion rates of European sardine Sardina pilchardus larvae in the laboratory

Abstract

The quantification of prey requirements for larval fish is essential to understand how environmental factors act to restrict suitable habitats and recruitment success in marine fish. The effect of prey concentration on ingestion rates of the European sardine Sardina pilchardus was estimated for larvae through 50 d post-hatch (dph) under controlled laboratory conditions at 15°C. Prey were nauplii and copepodites of the calanoid copepod Acartia grani, which were provided to larvae at 3 concentrations (0.5, 2 and 6 nauplii ml −1 and 0.1, 0.5 and 1 copepodites ml −1 ). Larvae were not able to capture copepod nauplii at the beginning of exogenous feeding, suggesting that early larvae depend on smaller prey types and/or less mobile prey than copepods. The mean size of prey found in the guts of sardine larvae increased from 145 to 348 μm for larvae of total length increasing from 6 to 18 mm, respectively. Maximum ingestion rates (232 ± 8.0 μg C larva −1 h −1 ) were reached at the highest prey concentration diet for individuals > 40 dph (1500 to 2500 μg C dry weight). These feeding rates are higher than values previously reported for the larvae of small pelagic fish. The inability of sardine larvae to feed at low prey concentrations, particularly during the first weeks of life, suggests that this species relies on and is adapted to forage within dense prey patches. Given this feeding strategy, bottom-up processes causing food limitation may strongly impact the survival and growth of sardine larvae.

Remotely Sensing the Biophysical Drivers of Sardinella aurita Variability in Ivorian Waters

“…Finally, the carbon consumption rate may be divided by the total number of larvae, which gives 1.2 µg C larva −1 h −1 . The latter result is within the same order of magnitude compared to previously published figures by Caldeira et al [90], who reported carbon intake rates for sardine species Sardina pilchardus in European waters between 4.5 and 7 µg C larva −1 h −1 . The relatively lower carbon consumption rate observed here for Sardinella aurita may be due to the fact that (1) the European Sardina pilchardus is likely to present anatomical and physiological differences, as well as living in different environmental conditions, compared with the species Sardinella aurita studied here in Ivorian waters; and (2) our calculation is based on total Sardinella catch, and this value is likely to underestimate the total number of Sardinella individuals present in the study area (i.e., not all Sardinella may have been caught).…”

Sardine (Sardina pilchardus) larval dispersal in the Iberian upwelling system, using coupled biophysical techniques

“…Presently, there are already very realistic hydrodynamical models developed for the region (e.g., Tanner et al 2017;Lamas et al 2017) but the coupling with NPDZ models is still in its infancy in this region (e.g., Reboreda et al 2014). Results from several laboratory experiments about sardine biological traits are now available regarding larvae feeding (Caldeira et al 2014, growth (Moyano et al 2014;, mortality (Garrido et al 2015a, predation (Pereira et al 2014) and…”

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

“…The time spent swimming and the foraging behaviour of sardine larvae increased with age/size. The increase in the frequency of prey capture with age/size is a consequence of larger larvae swimming faster (Silva et al 2014) and being able to capture prey within a wider size range (Caldeira et al 2014). By being able to select larger prey, larger larvae maximize the net rate of energy gain, because, all other things being equal, larger prey yield more energy per unit effort.…”

“…Both K and C were expressed in carbon units (µg C) by using available conversions of larvae length to carbon content and prey mean length of prey (Paracartia grani) to carbon content (Caldeira et al 2014). Statistical ana lyses were performed using Matlab 8.1 (R2013a) from Mathworks (mortality data) and the open source software R version 2.9.2 of R Development Core Team (growth and behavioural data).…”

“…and nauplii, copepodites and adults of the copepod Paracartia grani. Details of the feeding conditions, which translate into saturated feeding and growth rates of sardine larvae, can be found in Silva et al (2014) and Caldeira et al (2014). Each morning, after checking the food concentration in the tanks, 20 to 30% of the tank water was renewed by syphoning the bottom of the tank, and new food was added to obtain the preestablished food concentration.…”