DOI: 10.5061/dryad.xpnvx0kfp
title: Changes in foraging mode caused by a decline in prey size have major bioenergetic consequences for a small pelagic fish

description: Global warming is causing profound modifications of aquatic ecosystems and
 one major outcome appears to be a decline in adult size of many fish
 species. Over the last decade, sardine populations in the Gulf of Lions
 (NW Mediterranean Sea) have shown severe declines in body size and
 condition as well as disappearance of the oldest individuals, which could
 not be related to overfishing, predation pressure, or epizootic diseases.
 In this study, we investigated whether this situation reflects a bottom-up
 phenomenon caused by reduced size and availability of prey that could lead
 to energetic constraints. We fed captive sardines with food items of two
 different sizes eliciting a change in feeding mode (filter-feeding on
 small items and directly capturing larger ones) at two different rations
 for several months, and then assessed their muscle bioenergetics to test
 for changes in cellular function. Feeding on smaller items was associated
 with a decline in body condition, even at high ration, and almost
 completely inhibited growth by comparison to sardines fed large items at
 high ration. Sardines fed on small items presented specific mitochondrial
 adjustments for energy sparing, indicating a major bioenergetic challenge.
 Moreover, mitochondria from sardines in poor condition had low basal
 oxidative activity but high efficiency of ATP production. Notably, when
 body condition was below a threshold value of 1.07, close to the mean
 observed in the wild, it was directly correlated with basal mitochondrial
 activity in muscle. The results show a link between whole-animal condition
 and cellular bioenergetics in the sardine, and reveal physiological
 consequences of a shift in feeding mode. They demonstrate that
 filter-feeding on small prey leads to poor growth, even under abundant
 food and an increase in the efficiency of ATP production. These findings
 may partially explain the declines in sardine size and condition observed
 in the wild.
description: "Read me" for usage of Data_Changes in foraging
 mode. Each sheet contains the data presented in each
 figure and table of the article. All the mitochondrial
 measurements were performed at 20°C.<br> Missing values of the
 mitochondrial measurements at the fibre or at the muscle level (Figure 2;
 Table 2) have been retired when the measurement was more than 2 standard
 deviations higher than the group average, or when the oxygen consumption
 after the addition of cytochrome c was increased by 30% or more.<br>
 Missing values of the mitochondrial measurements at the mitochondrial
 level (Table 2) are due to omissions during the measurements.<br> In
 the tab "Figure 3", the missing values are due to omissions
 during the measurements. Specific legends :<br>
 NA = missing values<br> Identity refers to the fish tag<br> LI
 = large items, SI = small items, LQ = large quantity, SQ = small
 quantity<br> BCI = Body condition index<br> ETS = electron
 transport system<br> ATP/O ratio = ratio between ATP production rate
 and oxygen consumption rate