Carbon and nitrogen stable isotope ratios of particulate organic matter (POM) in surface water and 63-200 μm-sized microphytoplankton collected at the fluorescence maximum were studied in four sites in the Gulf of Lions (NW Mediterranean), a marine area influenced by the Rhone River inputs, in May and November 2004. Some environmental (temperature, salinity) and biological (POM, Chlorophyll a and phaeopigments contents, phytoplankton biomass and composition) parameters were also analysed. Significantly different C and N isotopic signatures between surface water POM and microphytoplankton were recorded in all sites and seasons. Surface water POM presented systematically lower δ 13 C ( 4.2‰) and higher δ 15 N ( 2.8‰) values than those of microphytoplankton, due to a higher content of continental and detrital material. Seasonal variations were observed for all environmental and biological parameters, except salinity. Water temperature was lower in May than in November, the fluorescence maximum was located deeper and the Chlorophyll a content and the phytoplankton biomass were higher, along with low PON/Chl a ratio, corresponding to spring bloom conditions. At all sites and seasons, diatoms dominated the phytoplankton community in abundance, whereas dinoflagellate importance increased in autumn particularly in coastal sites. C and N isotopic signatures of phytoplankton did not vary with season. However, the δ 15 N of surface water POM was significantly higher in November than in May in all sites likely in relation to an increase in 15 N/ 14 N ratio of the Rhone River POM which influenced surface water in the Gulf of Lions. As it is important to determine true baseline values of primary producers for analysing marine food webs, this study demonstrated that C and N isotopic values of surface water POM cannot be used as phytoplankton proxy in coastal areas submitted to high river inputs.

Variations in space and time of juvenile hake diet (5 to 19 cm total length, TL) were investigated in the Gulf of Lions (NW Mediterranean) and related to variation in C and N stable isotope ratios, condition and abundance. Crustaceans (mysids and euphausiids) dominated the diet of the smallest juvenile hake (5 to 9 cm TL), and fishes (sardines and anchovies) of the largest juveniles (15 to 19 cm TL). The transition from a crustacean-to a fish-based diet occurred in medium-sized juveniles (10 to 14 cm TL), which preyed on both crustaceans and fishes (gobiids). These juveniles preyed on fishes when living in shallow waters (30 to 50 m), and crustaceans when located in deep waters (70 to 150 m). Although hake diet did not change over time in shallow waters (fish-based diet), in deep waters it was dominated by mysids and euphausiids in 2002 and natantids in 2003. In the size range analysed, no correlation was found between juvenile hake length and their δ 13 C and δ 15 N values, but a significant correlation with depth was observed, with higher values in shallow waters. The condition factor of medium-sized juveniles did not vary with depth in 2002, but was significantly lower in deep waters in 2003 when they fed on natantids instead of small crustaceans. Abundance of juvenile hake in the Gulf of Lions drastically decreased from 2002 to 2003, particularly in deep waters. The lower condition factor of juvenile hake in deep waters in 2003, probably owing to a lack of suitable food, might have negatively affected their survival. These results support the hypothesis that food resources influence condition and survival of juvenile hake when settled, and thus affect NW Mediterranean fisheries.

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This study investigated the contributions of five putative nursery areas, namely four coastal lagoons and the marine coastal zone, to the local offshore fishery of the gilthead sea bream Sparus aurata, in the Gulf of Lion (NW Mediterranean). A detailed database of multi-elemental lagoon and marine otolith signatures was developed, based upon analysis of multiple sequential spots across growth bands of the otoliths of juveniles (n 5 142) sampled from the habitats over a 5-yr interval. Adults of 10 annual cohorts (n 5 114), fished throughout the Gulf, were then submitted to a similar microchemical analysis of the growth band of their otoliths that was formed after nursery settlement in their first year. Using the juvenile signature database and Random Forest classification algorithms, adults were re-assigned to the lagoons or marine coastal zone as a nursery. More than 80% of adults derived from lagoons, being 85.0% for five consecutive cohorts. Therefore, the marine coastal zone apparently contributed few adults, especially as a function of surface area. The four lagoons differed, however, in their contribution to the S. aurata fishery. Two lagoons qualified as "Effective Juvenile Habitats" that contributed more than 20% of the adults fished. Two shallow brackish lagoons were "Nursery-Role Habitats" that contributed almost twice as many adults, per unit surface area, as the overall average. Such information can support strategies for sustainable management of multiple coastal lagoon habitats, and of valuable fisheries that depend upon them.

1. In the Amazon, migratory catfishes of the genus Brachyplatystoma are apex predators that are important for fisheries and conservation. The life cycle of Brachyplatystoma platynemum Boulenger, 1898 is poorly known, although it has been hypothesized to be very similar to that of Brachyplatystoma rousseauxii Castelnau, 1855, which uses the entire length of the Amazon basin to complete its life cycle (from the Andes to the estuary). This study provides the first data on the migratory patterns of B. platynemum at the individual level using otolith microchemistry.2. In total, 94 individuals were sampled close to major breeding areas in the Amazon basin (78 fish from the middle and upper Madeira River and 14 fish from the upper Amazon), and their lifetime movements were assessed by measuring variations in 87 Sr/ 86 Sr along transverse sections of their otoliths (ear stones), using laser ablation multi-collector mass spectrometry (LA-MC-ICP-MS).3. The migrations of B. platynemum are not as extensive as those of B. rousseauxii, and do not involve natal homing. Furthermore, the estuary is not a nursery area, at least for fish hatched in the Madeira. Nevertheless, B. platynemum migrates several

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Abstract1. Elemental analysis of biological calcified structures (e.g. fish otoliths, mollusc shelves, coral skeletons or fish and shark bones) provides invaluable information regarding ecological processes for many aquatic species. Despite this importance, the reduction of the raw data obtained through Laser-ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS) (i.e. the conversion of the machine raw signal into elemental concentrations) remains a challenge as the tools developed so far for carrying out this task have important limitations for aquatic ecologists.2. Here, we introduce the elementr R-package which provides a handy, reliable and transparent way to reduce elemental data acquired from spot or transect LA-ICPMS analysis of biological calcified structures. This free and open-source software, implemented based on state-of-the-art literature, handles data from both standards and samples, allowing fast and simultaneous calculations of concentration for any chemical element, correction for potential machine drift, and realignment and averaging for sample replicates when needed.3. The major attributes of elementr are: (i) its user-friendly graphical interface which provides widgets to set all the reduction settings (i.e. no programming skills are required to run it), (ii) its reactivity whereby the software continuously observes any setting change made by the user, re-calculates and displays all updated results, allowing therefore users to visually check the validity of their settings and to tune them if needed and (iii) an object oriented underlying that facilitates subsequent handling of LA-ICPMS data in R.4. Despite the elementr design being most suited to the needs of aquatic ecologists, its use could be broadened to other research fields (i.e. geology, material engineering) due to its flexibility. Moreover, the open-source approach used for programming this software allows its expansion in order to refine calculation procedures or to add new functionalities. K E Y W O R D Sgraphical user interface, laser ablation, microchemistry, object-oriented programming, spot and transect reduction 1660 | Methods in Ecology and Evoluঞon SIROT eT al. | INTRODUCTIONOver the last decade, elemental microchemistry of biological calcified structures (e.g. fish otoliths, fish and shark bones, mollusc shelves or coral skeletons) has become one of the top reference methods for studying aquatic organism life cycles and past environmental conditions (Morrongiello, Thresher, & Smith, 2012). Regarding fish ecology, this approach has already proved its worth for identifying key lifetime habitats (Vasconcelos et al., 2008(Vasconcelos et al., , 2010, discriminating populations and stocks (Campana, Chouinard, Hanson, Fréchet, & Brattey, 2000;Edmonds, Caputi, & Morita, 1991;Kerr & Campana, 2013), tracking individual migration (Jessop, Shiao, Iizuka, & Tzeng, 2002;Mercier, Mouillot, Bruguier, Vigliola, & Darnaude, 2012) or assessing habitat connectivity (Gillanders, 2005;Reis-Santos et al., 2012). Moreover, numerous studi...