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Keller, S., Hidalgo, M., Alvarez-Berastegui, D., Bitetto, I., Casciaro, L., Cuccu, D., et al. (2017). Demersal cephalopod communities in the Mediterranean: a large-scale analysis. Mar. Ecol.-Prog. Ser., 584, 105–118.
Résumé: Cephalopod assemblages at the scale of the entire Mediterranean Sea were analysed using information from 2 decades of standardized scientific bottom trawl surveys. Western and eastern assemblages (6 yr of data) were compared using a combined approach of multivariate ordination techniques and non-linear regressions. These methods enabled us to distinguish assemblages and simultaneously analyse the influence of geographic, bathymetric and environmental (sea surface temperature and chlorophyll a concentration) gradients on observed community patterns. Despite few differences in species composition between sub-basins, the relative contribution of species differed. Bathymetry was the primary structural driver for the cephalopod communities of both basins, and contributed to 3 assemblages (shallow water, upper slope and middle slope). Winter temperature influenced community assemblages more strongly in the western than in the eastern basin, in contrast to a small but consistent winter productivity influence on community assemblages in both basins. Thus, the environmental parameters analysed did not cause an immediate change in cephalopod assemblages, but rather an effect lagged by several months. Differences in the relative importance of environmental drivers show that different processes operate in the 2 basins. These results demonstrate similarities and differences between Mediterranean basins regarding important cephalopod functional groups. This information should help integrative ecosystem management approaches currently used in fisheries and conservation management.
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Keller, S., Quetglas, A., Puerta, P., Bitetto, I., Casciaro, L., Cuccu, D., et al. (2017). Environmentally driven synchronies of Mediterranean cephalopod populations. Prog. Oceanogr., 152, 1–14.
Résumé: The Mediterranean Sea is characterized by large scale gradients of temperature, productivity and salinity, in addition to pronounced mesoscale differences. Such a heterogeneous system is expected to shape the population dynamics of marine species. On the other hand, prevailing environmental and climatic conditions at whole basin scale may force spatially distant populations to fluctuate in synchrony. Cephalopods are excellent case studies to test these hypotheses owing to their high sensitivity to environmental conditions. Data of two cephalopod species with contrasting life histories (benthic octopus vs nectobenthic squid), obtained from scientific surveys carried out throughout the Mediterranean during the last 20 years were analyzed. The objectives of this study and the methods used to achieve them (in parentheses) were: (i) to investigate synchronies in spatially separated populations (decorrelation analysis); (ii) detect underlying common abundance trends over distant regions (dynamic factor analysis, DFA); and (iii) analyse putative influences of key environmental drivers such as productivity and sea surface temperature on the population dynamics at regional scale (general linear models, GLM). In accordance with their contrasting spatial mobility, the distance from where synchrony could no longer be detected (decorrelation scale) was higher in squid than in octopus (349 vs 217 km); for comparison, the maximum distance between locations was 2620 km. The DFA revealed a general increasing trend in the abundance of both species in most areas, which agrees with the already reported worldwide proliferation of cephalopods. DFA results also showed that population dynamics are more similar in the eastern than in the western Mediterranean basin. According to the GLM models, cephalopod populations were negatively affected by productivity, which would be explained by an increase of competition and predation by fishes. While warmer years coincided with declining octopus numbers, areas of high sea surface temperature showed higher densities of squid. Our results are relevant for regional fisheries management and demonstrate that the regionalisation objectives envisaged under the new Common Fishery Policy may not be adequate for Mediterranean cephalopod stocks. (C) 2017 Elsevier Ltd. All rights reserved.
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Lamarre, S. G., Ditlecadet, D., McKenzie, D. J., Bonnaud, L., & Driedzic, W. R. (2012). Mechanisms of protein degradation in mantle muscle and proposed gill remodeling in starved Sepia officinalis. Am. J. Physiol.-Regul. Integr. Comp. Physiol., 303(4), R427–R437.
Résumé: Lamarre SG, Ditlecadet D, McKenzie DJ, Bonnaud L, Driedzic WR. Mechanisms of protein degradation in mantle muscle and proposed gill remodeling in starved Sepia officinalis. Am J Physiol Regul Integr Comp Physiol 303: R427-R437, 2012. First published May 30, 2012; doi:10.1152/ajpregu.00077.2012.-Cephalopods have relatively high rates of protein synthesis compared to rates of protein degradation, along with minimal carbohydrate and lipid reserves. During food deprivation on board protein is catabolized as a metabolic fuel. The aim of the current study was to assess whether biochemical indices of protein synthesis and proteolytic mechanisms were altered in cuttlefish, Sepia officinalis, starved for 7 days. In mantle muscle, food deprivation is associated with a decrease in protein synthesis, as indicated by a decrease in the total RNA level and dephosphorylation of key signaling molecules, such as the eukaryote binding protein, 4E-BP1 (regulator of translation) and Akt. The ubiquitination-proteasome system (UPS) is activated as shown by an increase in the levels of proteasome beta-subunit mRNA, polyubiquitinated protein, and polyubiquitin mRNA. As well, cathepsin activity levels are increased, suggesting increased proteolysis through the lysosomal pathway. Together, these mechanisms could supply amino acids as metabolic fuels. In gill, the situation is quite different. It appears that during the first stages of starvation, both protein synthesis and protein degradation are enhanced in gill. This is based upon increased phosphorylation of 4E-BP1 and enhanced levels of UPS indicators, especially 20S proteasome activity and polyubiquitin mRNA. It is proposed that an increased protein turnover is related to gill remodeling perhaps to retain essential hemolymph-borne compounds.
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Paulino, C., Aroni, E., Xu, H., Alburqueque, E., & Demarcq, H. (2017). Use of nighttime visible images in the study of the spatial and temporal variability of fishing areas of jumbo flying squid (Dosidicus gigas) outside Peruvian EEZ 2004-2015. Fish Res., 191, 144–153.
Résumé: We analyzed the temporal variability of the fishing fleet of Dosidicus gigas, located outside the exclusive economic zone of Peru (EEZ), with a spatial luminosity index. The nighttime satellite images were provided by the Operational Linescan System (DMSP-OLS) from 2004 to 2015. 2995 images were processed, selecting pixels in the range of 30-63 Digital Number (DN), to identify the presence of vessels in the image. The time series showed an extensive latitudinal distribution of the fishing fleet from 6 degrees S to 32 degrees S, with years of low (2005-2009) and high (2004, 2010-2015) presence, describing a recurrent seasonal pattern of latitudinal displacement measured from its center of gravity (CG). The CG reaches its southernmost position between February to April and its northernmost position between August to October. Some vessels were also detected within the Peruvian EEZ. The latitudinal inertia presented values of 0.3-1 indicating high fleet concentration between 12 degrees S to 17 degrees S and the longitudinal inertia presented values >2, showing the wide distribution of the resource. Luminous pixels showed high fishing occurrence (>18 times) on a single pixel, in front of Chimbote around 9 degrees 51'S-82 degrees 31'W from 2004 to 2011. From 2012 to 2015 areas of high fishing occurrence increased in front of Huarmey (10 degrees 36'S/82 degrees 41'W) and San Juan de Marcona (15 degrees 53'S/80 degrees 6'W). For both periods, high intensity pixels (DN >60) show extensive areas of fishing operation between 9 degrees S to 20 degrees S along 200 nautical miles from the coast, while values between 30 and 45 DN could be mostly associated with the search for fishing zones. Since 2012, pixels with DN >58 have increased, indicating a greater fishing activity likely related to a higher availability of the resource or a better knowledge of the fishing zones, associated with an increase of the fishing effort and a possible higher pressure on the resource. (C) 2017 Elsevier B.V. All rights reserved.
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