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Isnard, E., Tournois, J., McKenzie, D. J., Ferraton, F., Bodin, N., Aliaume, C., et al. (2015). Getting a Good Start in Life? A Comparative Analysis of the Quality of Lagoons as Juvenile Habitats for the Gilthead Seabream Sparus aurata in the Gulf of Lions. Estuaries and Coasts, , 1–14.
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Le Vaillant, M., Viblanc, V. A., Saraux, C., Bohec, C. L., Maho, Y. L., Kato, A., et al. (2015). Telomere length reflects individual quality in free-living adult king penguins. Polar Biol, 38(12), 2059–2067.
Résumé: Growing evidence suggests that telomeres, non-coding DNA sequences that shorten with age and stress, are related in an undefined way to individual breeding performances and survival rates in several species. Short telomeres and elevated shortening rates are typically associated with life stress and low health. As such, telomeres could serve as an integrative proxy of individual quality, describing the overall biological state of an individual at a given age. Telomere length could be associated with the decline of an array of physiological traits in age-controlled individuals. Here, we investigated the links between individuals’ relative telomere length, breeding performance and various physiological (body condition, natural antibody levels) and life history (age, past breeding success) parameters in a long-lived seabird species, the king penguin Aptenodytes patagonicus. While we observed no link between relative telomere length and age, we found that birds with longer telomeres arrived earlier for breeding at the colony, and had higher breeding performances (i.e. the amount of time adults managed to maintain their chicks alive, and ultimately breeding success) than individuals with shorter telomeres. Further, we observed a positive correlation between telomere length and natural antibody levels. Taken together, our results add to the growing evidence that telomere length is likely to reflect individual quality difference in wild animal.
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Queiros, Q., Fromentin, J. - M., Gasset, E., Dutto, G., Huiban, C., Metral, L., et al. (2019). Food in the sea: size also matters for pelagic fish. Front. Mar. Sci., 6, Unsp-385.
Résumé: Small pelagic fish are key components of marine ecosystems and fisheries worldwide. Despite the absence of recruitment failure and overfishing, pelagic fisheries have been in crisis for a decade in the Western Mediterranean Sea because of a marked decline in sardine size and condition. This situation most probably results from bottom-up control and changes in the plankton community toward smaller plankton. To understand such an unusual phenomenon, we developed an original and innovative experimental approach investigating the mechanisms induced by a reduction in the quantity and size of sardine prey. While experimentations offer the unique opportunity to integrate behavior and ecophysiology in understanding key demographic processes, they remain rarely used in fisheries science, even more so on small pelagics due to the notorious difficulty to handle them. The results revealed that food size (without any modification of its energy content) is as important as food quantity for body condition, growth and reserve lipids: sardines that fed on small particles had to consume twice as much as those feeding on large particles to achieve the same condition and growth. Such a strong impact of food size (based on 100 vs. 1200 mu m pellets) was unexpected and may reflect a different energy cost or gain of two feeding behaviors, filter-feeding vs. particulate-feeding, which would have to be tested in further study. As increasing temperature favors planktonic chains of smaller size, climate change might actually accelerate and amplify such phenomenon and thus strongly affect fisheries.
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Saraux, C., Chiaradia, A., Salton, M., Dann, P., & Viblanc, V. A. (2016). Negative effects of wind speed on individual foraging performance and breeding success in little penguins. Ecol Monogr, 86(1), 61–77.
Résumé: Most effects of environmental and climate variability on predator life history traits and population dynamics result from indirect effects mediated through the food chain. There is growing evidence that wind strength might affect seabirds while foraging at sea. Here, we investigated the effect of wind speed on the foraging performance of a flightless marine predator, the little penguin (Eudyptula minor). To this end, we used satellite-derived wind data collected over 11 breeding seasons during which the daily attendance and body mass changes of more than 200 penguins breeding at Phillip Island (Victoria, Australia) were recorded by an automated penguin monitoring system. Over 17 363 foraging trips, we found that wind speed had important effects on foraging and provisioning parameters in breeding adults. During incubation and chick-guard, stronger winds were associated with decreased foraging efficiency (lower body mass gain). During chick-guard, stronger winds were furthermore associated with lower meal sizes provided to the chicks, but parental body reserves appeared unaffected. Under extreme wind conditions (>14 m/s) during the post-guard phase, adults maintained their body reserves by shifting towards longer foraging trips, while providing chicks with smaller meals. Chick meal size and foraging trip duration during chick rearing had direct effects on breeding success, suggesting that the influence of wind on individual fitness was mediated by changes in foraging performances and success. Furthermore, using a long-term wind data series spanning 150-yr from a coastal wind station, we found a slight decline in wind speed and a decrease in wind speed variability in the Bass Strait where little penguins forage. Interestingly, based on this wind data, we found birds to be more directly affected by punctual events of strong winds (e.g. storms or gales), than by an overall change in wind patterns over time. Potential candidate mechanisms mediating the effects of wind speed on foraging efficiency may include swell formation, energy costs of travelling and thermoregulation, and a possible disruption of thermoclines, which may be important for little penguins. Plasticity in foraging strategies allowed parents to partially compensate for negative wind effects.
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Saraux, C., Van Beveren, E., Brosset, P., Queiros, Q., Bourdeix, J. - H., Dutto, G., et al. (2019). Small pelagic fish dynamics: A review of mechanisms in the Gulf of Lions. Deep-Sea Res. Part II-Top. Stud. Oceanogr., 159, 52–61.
Résumé: Around 2008, an ecosystem shift occurred in the Gulf of Lions, highlighted by considerable changes in biomass and fish mean weight of its two main small pelagic fish stocks (European anchovy, Engraulis encrasicolus; European sardine, Sardina pilchardus). Surprisingly these changes did not appear to be mediated by a decrease in fish recruitment rates (which remained high) or by a high fishing pressure (exploitation rates being extremely low). Here, we review the current knowledge on the population's dynamics and its potential causes. We used an integrative ecosystem approach exploring alternative hypotheses, ranging from bottom-up to top-down control, not forgetting epizootic diseases. First, the study of multiple population characteristics highlighted a decrease in body condition for both species as well as an important decrease in size resulting from both a slower growth and a progressive disappearance of older sardines. Interestingly, older sardines were more affected by the decrease in condition than younger ones, another sign of an unbalanced population structure. While top-down control by bluefin tuna or dolphins, emigration and disease were mostly discarded as important drivers, bottom-up control mediated by potential changes in the plankton community appeared to play an important role via a decrease in fish energy income and hence growth, condition and size. Isotopic and stomach content analyses indicated a dietary shift pre- and post-2008 and modeled mesozooplankton abundance was directly linked to fish condition. Despite low energy reserves from 2008 onwards, sardines and anchovies maintained if not increased their reproductive investment, likely altering the life-history trade-off between reproduction and survival and resulting in higher natural mortality. The current worrying situation might thus have resulted from changes in plankton availability/diversity, which remains to be thoroughly investigated together with fish phenotypic plasticity.
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